Receiving device and receiving method

Abstract

To provide a receiver device capable of obtaining information safely.SOLUTION: A receiver device A2000 includes: one or more image sensors A8001-1 for acquiring image data and optical signals; and a processor A10001. The processor A10001 is configured to detect an object that includes the light source that has emitted the light signal by performing image processing on image data, acquire demodulated data by demodulating the optical signal, and store the demodulated data in memory A10002 while associating the same with the detected object.SELECTED DRAWING: Figure 43

Description

Technical Field

[0001] The present disclosure relates to a receiving apparatus and a receiving method.

Background Art

[0002] For purposes such as using services based on the position of a terminal, there is a method that uses GPS (Global Positioning System) as a method for a terminal to acquire information such as its own position. In the method using GPS, the terminal estimates its own location by receiving a modulated signal transmitted from a satellite and performing positioning calculation. However, when it is difficult for the terminal to receive radio waves transmitted from a satellite (for example, indoors), it becomes difficult for the terminal to estimate its own location.

[0003] As a method for a terminal to estimate its own location in such a case, for example, as disclosed in Non-Patent Document 1, there is a method in which the terminal estimates information such as its own location by using radio waves transmitted from an access point (AP (access point)) of a wireless LAN (Local Area Network).

Prior Art Documents

Non-Patent Documents

[0004]

Non-Patent Document 1

Non-Patent Document 2

Non-Patent Document 3

[0005] However, if a device does not store information such as the SSID (service set identifier) ​​of the access point it should access, it is not easy for the device to properly determine which access point to connect to from among several access points in its vicinity. For this reason, when a device connects to an access point to obtain information such as its location, it may connect to an access point with an insecure SSID, posing a threat such as information leakage.

[0006] One aspect of this disclosure facilitates the provision of a receiving device, for example, that can securely obtain information used to identify an access point to which a terminal should connect. [Means for solving the problem]

[0007] A receiving device according to one aspect of the present disclosure includes one or more image sensors that acquire image data and optical signals, and a processor, wherein the processor detects an object equipped with a light source that transmitted the optical signal by performing image processing on the image data, acquires demodulated data by demodulating the optical signal, and stores the demodulated data in memory in association with the detected object.

[0008] A receiving device according to one aspect of the present disclosure comprises one or more image sensors that acquire image data and a received signal, and a processor, wherein the processor detects an object by performing image processing on the image data, acquires demodulated data by demodulating the received signal, and stores the demodulated data in memory in association with the detected object.

[0009] A receiving method according to one aspect of the present disclosure is a receiving method performed by a receiving device equipped with one or more image sensors, wherein the one or more image sensors acquire an image and a received signal, an object is detected by performing image processing on the image data, demodulated data is acquired by demodulating the received signal, and the demodulated data is stored in a memory associated with the detected object.

[0010] These comprehensive or specific embodiments may be implemented as a system, method, integrated circuit, computer program, or recording medium, or as any combination of a system, device, method, integrated circuit, computer program, and recording medium. [Effects of the Invention]

[0011] According to one aspect of this disclosure, a terminal can securely obtain information.

[0012] Further advantages and effects of one aspect of this disclosure will be made apparent from the specification and drawings. Such advantages and / or effects are provided by several embodiments and features described in the specification and drawings, but not all of them are necessarily provided in order to obtain one or more identical features. [Brief explanation of the drawing]

[0013] [Figure 1] Figure 1 is a diagram illustrating the principle of line scan sampling. [Figure 2] Figure 2 shows an example of an image captured with a long exposure time. [Figure 3] FIG. 3 is a diagram illustrating an example of a captured image when the exposure time is short. [Figure 4A] FIG. 4A is a diagram for explaining 4PPM. [Figure 4B] FIG. 4B is a diagram for explaining the Manchester coding scheme. [Figure 5] FIG. 5 is a diagram illustrating a configuration example of a visible light communication system. [Figure 6] FIG. 6 is a diagram illustrating a configuration example of a communication system according to the first embodiment. [Figure 7] FIG. 7 is a diagram illustrating an example of a frame structure according to the first embodiment. [Figure 8] FIG. 8 is a diagram illustrating the positional relationship between a device and a terminal according to the second embodiment. [Figure 9] FIG. 9 is a diagram illustrating a configuration example of a communication system according to the third embodiment. [Figure 10] FIG. 10 is a diagram illustrating a display example of a display unit according to the third embodiment. [Figure 11] FIG. 11 is a diagram illustrating an example of a frame structure of a modulated signal transmitted by a first device according to the third embodiment. [Figure 12] FIG. 12 is a diagram illustrating an example of a frame structure of a modulated signal transmitted by a base station according to the third embodiment. [Figure 13] FIG. 13 is a flowchart illustrating an example of processing in the communication system according to the third embodiment. [Figure 14] FIG. 14 is a diagram illustrating a display example of a display unit according to the third embodiment. [Figure 15] FIG. 15 is a diagram illustrating a configuration example of a communication system according to the fourth embodiment. [Figure 16] FIG. 16 is a diagram illustrating an example of a frame structure of a modulated signal transmitted by a first device according to the fourth embodiment. [Figure 17] FIG. 17 is a diagram illustrating an example of a frame structure of a modulated signal transmitted by a wireless device of a terminal according to the fourth embodiment. [Figure 18] FIG. 18 is a flowchart illustrating an example of processing in the communication system according to the fourth embodiment. [Figure 19] Figure 19 shows an example of the configuration of a communication system according to Embodiment 5. [Figure 20] Figure 20 shows an example of the frame configuration of a modulated signal including the SSID transmitted by the third device according to Embodiment 5. [Figure 21] Figure 21 shows an example of the frame configuration of a modulated signal including an encryption key transmitted by the third device according to Embodiment 5. [Figure 22] Figure 22 is a flowchart showing an example of processing in the communication system according to Embodiment 5. [Figure 23] Figure 23 is a flowchart showing another example of processing in the communication system according to Embodiment 5. [Figure 24] Figure 24 shows an example of a space in which the communication system according to Embodiment 5 is installed. [Figure 25] Figure 25 shows an example of the configuration of a communication system according to Embodiment 6. [Figure 26] Figure 26 is a flowchart showing an example of processing in the communication system according to Embodiment 6. [Figure 27] Figure 27 is a diagram showing an example configuration of a communication system according to Embodiment 7. [Figure 28] Figure 28 shows an example of the frame configuration of a modulated signal transmitted by the fifth device according to Embodiment 7. [Figure 29] Figure 29 is a diagram showing an example of the frame configuration of a modulated signal transmitted by the fifth device according to Embodiment 7. [Figure 30] Figure 30 shows an example of the frame configuration of the modulated signal transmitted by the fifth device according to Embodiment 7. [Figure 31] Figure 31 shows an example of a frame transmission method by the fifth device according to Embodiment 7. [Figure 32] Figure 32 shows an example of a space in which the communication system according to Embodiment 7 is installed. [Figure 33]Figure 33 is a flowchart showing an example of processing in the communication system according to Embodiment 7. [Figure 34] Figure 34 shows an example of the configuration of a communication device according to Embodiment 8. [Figure 35] Figure 35 shows another example of the configuration of the communication device according to Embodiment 8. [Figure 36] Figure 36 shows a first configuration example of a light receiving device according to Embodiment 8. [Figure 37] Figure 37 shows a first example of the configuration of the light receiving signal processing unit according to Embodiment 8. [Figure 38] Figure 38 shows a second example of the configuration of the light receiving signal processing unit according to Embodiment 8. [Figure 39] Figure 39 shows an example of image sensor control in Embodiment 8. [Figure 40] Figure 40 shows a third example of the configuration of the light receiving signal processing unit according to Embodiment 8. [Figure 41] Figure 41 shows a second example configuration of the light receiving device according to Embodiment 8. [Figure 42] Figure 42 shows an example of performing line scan sampling in parallel across multiple regions. [Figure 43] Figure 43 shows an example of the physical configuration of the control unit according to Embodiment 8. [Figure 44] Figure 44 shows an example of the configuration of the control unit according to Embodiment 8. [Figure 45] Figure 45 shows another example of the configuration of the control unit according to Embodiment 8. [Figure 46] Figure 46 is the first diagram illustrating communication control based on acquired images according to Embodiment 8. [Figure 47] Figure 47 is a second diagram illustrating communication control based on acquired images according to Embodiment 8. [Figure 48] Figure 48 is a third diagram illustrating communication control based on acquired images according to Embodiment 8. [Figure 49]Figure 49 is a fourth diagram illustrating communication control based on acquired images according to Embodiment 8. [Figure 50] Figure 50 is a fifth diagram illustrating communication control based on acquired images according to Embodiment 8. [Figure 51] Figure 51 is a sixth diagram illustrating communication control based on acquired images according to Embodiment 8. [Figure 52] Figure 52 shows an example configuration of another communication system that uses optical communication. [Figure 53] Figure 53 shows an example of the configuration of the transmitting device and receiving device according to Embodiment 10. [Figure 54] Figure 54 shows an example of the configuration of a transmitting device and a receiving device according to Embodiment 10. [Figure 55] Figure 55 shows an example of the frame configuration of an optically modulated signal according to Embodiment 10. [Figure 56] Figure 56 shows an example of the reception state in the receiving device according to Embodiment 10. [Figure 57] Figure 57 shows an example of the symbol configuration according to Embodiment 10. [Figure 58] Figure 58 shows another example of the symbol configuration according to Embodiment 10. [Figure 59] Figure 59 shows another example of the reception state in the receiving device according to Embodiment 10. [Figure 60] Figure 60 shows another example of the reception state in the receiving device according to Embodiment 10. [Figure 61] Figure 61 shows another example of the symbol configuration according to Embodiment 10. [Figure 62] Figure 62 shows another example of the symbol configuration according to Embodiment 10. [Figure 63] Figure 63 shows another example of the symbol configuration according to Embodiment 11. [Figure 64] Figure 64 shows an example of the configuration of a receiving device according to Embodiment 11. [Figure 65]Figure 65 shows another example of the configuration of the receiving device according to Embodiment 11. [Figure 66] Figure 66 shows another example of the configuration of the receiving device according to Embodiment 11. [Figure 67] Figure 67 shows another example of the configuration of the receiving device according to Embodiment 11. [Figure 68] Figure 68 shows an example of multiple light sources installed in a vehicle. [Figure 69] Figure 69 shows an example of multiple light-receiving units equipped in a vehicle. [Modes for carrying out the invention]

[0014] Embodiments of this disclosure will be described in detail below with reference to the drawings.

[0015] [Example of a first visible light communication modulation / demodulation method] In this embodiment, an optical communication method is used to transmit and receive modulated signals as optical signals.

[0016] First, we will describe a first example of visible light communication, which is an example of an optical communication method applicable to each embodiment of this disclosure.

[0017] <Line scan sampling> Smartphones and digital cameras are equipped with image sensors such as CMOS (Complementary Metal Oxide Semiconductor) sensors. Images captured by a CMOS sensor do not depict the entire scene at exactly the same time. For example, as shown in Non-Patent Documents 2 and 3, a rolling shutter method is used, where the shutter operates row by row, and the amount of light received by the sensor is read out for each line. Therefore, the start and end of light reception are controlled with a time difference for each line, taking into account the time required for reading out. In other words, the image captured by a CMOS sensor is a superimposed image of many lines with a slight time lag in the exposure period.

[0018] In the first example of the visible light communication method, high-speed reception of visible light signals is achieved based on a method that focuses on the properties of this CMOS sensor. Specifically, in the first example of the visible light communication method, by utilizing the fact that the exposure time differs slightly for each line, as shown in Figure 1, the brightness and color of the light source at multiple points in time can be measured line by line from a single image (image captured by the image sensor), and a signal modulated faster than the frame rate can be captured.

[0019] In the following, this sampling method will be referred to as "line scan sampling," and a row of pixels that are exposed at the same time will be called an "exposure line."

[0020] While "line scan sampling" can be achieved using a rolling shutter method with a CMOS sensor, it is also possible to perform "line scan sampling" using a rolling shutter method with sensors other than CMOS sensors, such as CCD (Charge-Coupled Device) sensors or organic (CMOS) sensors as exemplified in Non-Patent Document 4.

[0021] However, when using the camera function (video or still image capture function) with the imaging settings, even if a rapidly flashing light source is photographed, the flashing will not appear as stripes along the exposure lines. This is because, with these settings, the exposure time is sufficiently longer than the flashing period of the light source, so as shown in Figure 2, the change in brightness due to the flashing (emission pattern) of the light source is averaged out, the change in pixel values ​​between exposure lines becomes small, and a nearly uniform image is produced.

[0022] In contrast, as shown in Figure 3, by setting the exposure time to approximately the blinking period of the light source, the blinking state (emission pattern) of the light source can be observed as a change in the brightness of the exposure line. In Figure 3, the length of the exposure period is set to be slightly longer than the minimum duration for which the same emission state continues, and the difference in the start time of the exposure period between adjacent exposure lines is set to be shorter than the minimum duration for which the same emission state continues. However, the setting of the exposure period in RiceScan sampling is not limited to this. For example, the length of the exposure period may be set to be shorter than the minimum duration for which the same emission state continues, or it may be set to be about twice the minimum duration for which the same emission state continues. Furthermore, as an optical communication method, in addition to a method in which the optical signal is represented by a combination of rectangular waves as shown in Figure 4A, a method in which the optical signal changes continuously may also be used. In either case, the receiving device of the optical communication method sets the difference in the start or end time of the exposure period between temporally adjacent exposure lines to be the same as or less than the sampling interval corresponding to the sampling rate required to receive and demodulate the optical signal. The receiving device of the optical communication method also sets the length of the exposure period to be the same as or less than the sampling interval. However, the optical communication receiving device may set the exposure period to 1.5 times or less the sampling interval, or to 2 times or less.

[0023] For example, the exposure lines are designed to be parallel to the longer side of the image sensor. In this case, for instance, with a frame rate of 30fps (frames per second), a resolution of 1920×1080 would yield more than 32,400 samples per second, and a resolution of 3840×2160 would yield more than 64,800 samples per second.

[0024] <Examples of line scan sampling applications> The above description explains line scan sampling, which reads out a signal indicating the amount of light received for each line. However, the sampling method for optical signals using image sensors such as CMOS is not limited to this. Various sampling methods can be applied to receive optical signals, including methods that can acquire signals sampled at a sampling rate higher than the frame rate used for normal video recording. For example, a global shutter method, as shown in Non-Patent Documents 2 and 3, which provides a shutter function for each pixel, can be used to control the exposure period for each pixel and read out the signal. Alternatively, a method can be used in which the exposure period is controlled for groups of multiple pixels arranged in a non-linear shape and the signal is read out. Furthermore, a method can be used in which signals are read out multiple times from the same pixel within a period equivalent to one frame at the frame rate used for normal video recording.

[0025] <Sampling using frames> Furthermore, by using the frame rate method described in Non-Patent Documents 2 and 3, which provides a shutter function for each pixel, it is possible to sample optical signals even in a high-speed frame rate system.

[0026] The embodiments described below can be implemented using any of the methods already described, such as "line scan sampling," "applications of line scan sampling," and "frame sampling."

[0027] <Light source and modulation method> In visible light communication, for example, an LED (Light Emitting Diode) can be used as a transmitter. LEDs are becoming increasingly popular as lighting or backlight sources for displays, and they can be blinked at high speed.

[0028] However, light sources used as transmitters for visible light communication cannot be freely made to blink for visible light communication purposes. If the changes in brightness caused by visible light communication are perceptible to humans, it would impair the original function of the light source, such as illumination. Therefore, the transmitted signal must be designed to illuminate at the desired brightness while not appearing to the human eye as a flicker.

[0029] One modulation scheme that can meet this requirement is called 4PPM (4-Pulse Position Modulation). As shown in Figure 4A, 4PPM is a method that represents 2 bits using four combinations of brightness and darkness of the light source. Also, as shown in Figure 4A, in 4PPM, three of the four combinations are bright and one is dark, so the average brightness (average luminance) is 3 / 4 = 75%, regardless of the content of the signal.

[0030] For comparison, the Manchester coding scheme, shown in Figure 4B, is a similar method. The Manchester coding scheme represents one bit in two states, and its modulation efficiency is the same as 4PPM at 50%, but since one of the two states is bright and the other is dark, the average brightness is 1 / 2 = 50%. In other words, 4PPM is more suitable than the Manchester coding scheme as a modulation method for visible light communication. However, even if the change in brightness due to visible light communication is perceived by humans, the communication performance does not deteriorate, so depending on the application, there is no problem in using a method that produces a change in brightness that is perceived by humans. Therefore, the transmitter (light source) may generate a modulated signal using a modulation method such as ASK (Amplitude Shift Keying), PSK (Phase Shift Keying), or PAM (Pulse Amplitude Modulation), and then light up or illuminate the light source.

[0031] <Example of overall communication system configuration> As shown in Figure 5, a communication system that performs visible light communication includes at least a transmitter that transmits (irradiates) an optical signal and a receiver that receives (receives) an optical signal. For example, there are two types of transmitters: a variable optical transmitter that changes the transmitted content according to the image or content to be displayed, and a fixed optical transmitter that continues to transmit a fixed content. However, a communication system using light can also be configured with a configuration in which either a variable optical transmitter or a fixed optical transmitter is present.

[0032] The receiver receives an optical signal from the transmitter and, for example, can acquire related information associated with that optical signal and provide it to the user.

[0033] The above describes the overview of the visible light communication method, but the communication methods applicable to the optical communication described in the following embodiments are not limited to the above method. For example, the light-emitting part of the transmitter may use multiple light sources to transmit data. Also, the light-receiving part of the receiving device may use a device that can convert optical signals into electrical signals, such as a photodiode, instead of an image sensor such as a CMOS. In this case, it is not necessary to perform sampling using the line scan sampling described above, so it is applicable even to methods that require sampling of 32,400 or more per second. Furthermore, depending on the application, a communication method using wireless communication at frequencies other than visible light, such as infrared or ultraviolet light, may be used.

[0034] (Embodiment 1) Figure 6 shows an example of the configuration of the device 100 and terminal 150 in this embodiment.

[0035] [Configuration of device 100] Device 100 (corresponding to a visible light communication transmitter) is equipped with a visible light source such as an LED (Light Emitting Diode), illumination, or light (collectively referred to as a light source). In the following, device 100 may also be referred to as "the first device."

[0036] In the first device 100 in Figure 6, the transmitting unit 102 may, for example, receive location information or position information 101 as input. Alternatively, the transmitting unit 102 may receive time information 105 as input. Alternatively, the transmitting unit 102 may receive both location information or position information 101 and time information 105 as input.

[0037] The transmitting unit 102 takes location information or position information 101 and / or time information 105 as input, generates a (optical) modulated signal 103 based on these input signals, and outputs the modulated signal 103. The modulated signal 103 is then transmitted, for example, from the light source 104.

[0038] Here, we will describe 101 examples of location-related or position-related information.

[0039] <Example 1> The location information or positional information 101 may also be information about the latitude and / or longitude of the location. For example, the information "45 degrees North latitude, 135 degrees East longitude" may be the location information or positional information 101.

[0040] <Example 2> The location information or positional information 101 may also be address information. For example, the information "1-1-1, XX-cho, Chiyoda-ku, Tokyo" may be the location information or positional information 101.

[0041] <Example 3> The location information or positional information 101 may be information about buildings, facilities, etc. For example, the information "Tokyo Tower" may be the location information or positional information 101.

[0042] <Example 4> The location information or positional information 101 may also be information about the specific location or position of something installed in a building, facility, etc.

[0043] For example, suppose there is space in a parking lot that can accommodate five cars. In this case, the first parking space is called A-1, the second parking space is called A-2, the third parking space is called A-3, the fourth parking space is called A-4, and the fifth parking space is called A-5. In this case, for example, the information "A-3" may be considered as location information or positional information 101.

[0044] It should be noted that such examples are not limited to parking lots. For example, information about "areas, seats, shops, facilities, etc." in concert venues, stadiums for baseball, soccer, tennis, etc., airplanes, airport lounges, railways, stations, etc. may also be referred to as location information or positional information 101.

[0045] The above describes an example of location information or positional information 101. However, the method of constructing location information or positional information 101 is not limited to the example described above.

[0046] [Configuration of Terminal 150] The terminal 150 in Figure 6 (corresponding to a visible light communication receiver) receives the modulated signal 103 transmitted from the first device 100.

[0047] The light-receiving unit (photodetector) 151 is, for example, an image sensor such as a CMOS (Complementary Metal Oxide Semiconductor) or an organic CMOS. The light-receiving unit 151 receives light containing a modulated signal transmitted from the first device 100 and outputs a received signal 152.

[0048] The received signal 152 output from the light receiving unit 151 may be a signal containing image or video information acquired by the image sensor, or it may be the output signal of another optical-to-electrical conversion (converting light to an electrical signal) element. In the following description, when it is stated that the receiving device receives a modulated signal without specifically explaining the processing performed by the light receiving unit 151, it means that the receiving device obtains a "modulated signal for transmitting information," or an "image / video signal" and a "modulated signal for transmitting information," by performing optical-to-electrical conversion (converting light to an electrical signal) from the light containing the modulated signal at the light receiving unit 151. However, the method described above is just one example of how the receiving device receives a modulated signal, and the method of receiving a modulated signal is not limited to these.

[0049] The receiving unit 153 then takes the received signal 152 as input, performs demodulation, error correction decoding, and other processing on the modulated signal contained in the received signal 152, and outputs the received data 154.

[0050] The data analysis unit 155 takes the received data 154 as input and analyzes the received data 154 to estimate the location of the terminal 150, for example, and outputs information 156 that includes at least the location information of the terminal 150.

[0051] The display unit 157 takes information 156 as input and displays information about the location of the terminal 150 based on the location information of the terminal 150 contained in information 156.

[0052] [Frame composition] Figure 7 shows an example of the frame configuration of the modulated signal transmitted by the first device 100.

[0053] In Figure 7, the horizontal axis represents time. The first device 100 transmits, for example, a preamble 201, followed by a control information symbol 202, a symbol 203 relating to location or position information, and a symbol 204 relating to time information.

[0054] The preamble 201 is a symbol used by the terminal 150, which receives the modulated signal transmitted by the first device 100, to perform actions such as signal detection, time synchronization, and frame synchronization.

[0055] The control information symbol 202 is a symbol that contains data such as the method of constructing the modulated signal, the method of the error correction coding scheme used, and the method of constructing the frame.

[0056] Symbol 203, which relates to location information or positional information, is a symbol that includes location information or positional information 101 as shown in Figure 6.

[0057] The frame may also contain symbols other than symbols 201, 202, and 203. For example, as shown in Figure 7, it may include symbol 204 related to time information. Symbol 204 related to time information may include, for example, information 105 related to the time when the first device 100 transmits the modulated signal. Note that the configuration of the frame of the modulated signal transmitted by the first device 100 is not limited to that shown in Figure 7, and the symbols included in the modulated signal are not limited to the configuration shown in Figure 7. The frame may also contain symbols that include other data and information.

[0058] [effect] As explained in Figures 6 and 7, the effect when the first device 100 transmits a modulated signal and the terminal 150 receives that modulated signal will be described below.

[0059] Since the first device 100 transmits a modulated signal using visible light, the terminal 150 that can receive this modulated signal is not located far from where the first device 100 is located. Therefore, by obtaining the location information transmitted by the first device 100, the terminal 150 can easily obtain highly accurate location information (without performing complex signal processing).

[0060] Furthermore, if the first device 100 is installed in a location where it is difficult to receive satellite signals from GPS, the terminal 150 can safely obtain highly accurate location information by receiving the modulated signal transmitted by the first device 100, even in situations where it is difficult to receive signals from GPS satellites.

[0061] (Embodiment 2) This embodiment describes a case where there are multiple units of the first device 100 described in Embodiment 1.

[0062] In this embodiment, for example, as shown in Figure 8, a first-first device 301-1, which has a configuration similar to the first device 100 shown in Figure 6, transmits a modulated signal. A terminal 302, which has a configuration similar to the terminal 150 shown in Figure 6, receives the modulated signal transmitted by the first-first device 301-1 and obtains, for example, information regarding the first-first location and information regarding the first-first time.

[0063] Similarly, a first- and second device 301-2, having the same configuration as the first device 100 shown in Figure 6, transmits a modulated signal. Terminal 302 receives the modulated signal transmitted by the first- and second devices 301-2 and obtains, for example, information regarding the location and position of the first- and second devices, and information regarding the time of the first- and second devices.

[0064] Terminal 302 can calculate the distance between device 1-1 and device 1-2 in Figure 8 from the location information of 1-1 and the location information of 1-2. Terminal 302 can also calculate the distance between terminal 302 and device 1-1 based on the time information of 1-1 and, for example, the time at which terminal 302 received the modulated signal transmitted by device 1-1 301-1. Similarly, terminal 302 can calculate the distance between terminal 302 and device 1-2 based on the time information of 1-2 and, for example, the time at which terminal 302 received the modulated signal transmitted by device 1-2 301-2.

[0065] Furthermore, terminal 302 can determine the location of device 301-1 from the location information of 1-1. Terminal 302 can determine the location of device 301-2 from the location information of 1-2.

[0066] Furthermore, terminal 302 can determine the "triangle formed by device 301-1, device 301-2, and terminal 302" from the "distance between device 301-1 and device 301-2", the "distance between device 301-1 and terminal 302", and the "distance between device 301-2 and terminal 302".

[0067] Therefore, the position of terminal 302 can be calculated with high accuracy from "the position of the first-first device 301-1", "the position of the first-second device 301-2", and "the triangle formed by the first-first device 301-1, the first-second device 301-2, and terminal 302".

[0068] However, the geodetic surveying method used by terminal 302 to obtain location information is not limited to the above description, and any method of geodetic surveying may be used. For example, examples of geodetic surveying methods include triangulation, polygonal surveying, trilateration, and leveling.

[0069] As described above, in this embodiment, terminal 302 obtains the above-mentioned information from multiple devices 301 equipped with light sources that transmit location information, thereby enabling terminal 302 to estimate its own location with high accuracy.

[0070] Furthermore, in this embodiment, as described in Embodiment 1, if the device 301 equipped with a light source that transmits location information is installed in a location where it is difficult to receive satellite radio waves from GPS, the terminal 302 can safely obtain highly accurate location information by receiving the modulated signal transmitted by the device 301, even in situations where it is difficult to receive radio waves from GPS satellites.

[0071] In the example described above, terminal 302 receives modulated signals transmitted by two devices 301. However, the same procedure can be followed even when terminal 302 receives modulated signals transmitted by more than two devices 301. Furthermore, the greater the number of devices 301, the more accurately terminal 302 can calculate location information.

[0072] (Embodiment 3) Figure 9 shows an example of the configuration of the device 400, terminal 450, and base station 470 (or AP (access point)) that communicates with terminal 450 in this embodiment.

[0073] Device 400 includes, for example, a visible light source such as an LED, illumination, light source, or light. In the following, device 400 may also be referred to as "the first device."

[0074] In Figure 9, components of the first device 400 that operate in the same way as those of the first device 100 shown in Figure 6 are denoted by the same reference numerals. Similarly, in Figure 9, components of the terminal 450 that operate in the same way as those of the terminal 150 shown in Figure 6 are denoted by the same reference numerals.

[0075] In the first device 400 in Figure 9, the transmitting unit 102 receives, for example, location information or position information 101, SSID (service set identifier) ​​information 401-1 which is the identifier of the base station 470, and access destination information 401-2 as input. The transmitting unit 102 may also receive time information 105 as input.

[0076] The transmitting unit 102 takes location information or position information 101, SSID information 401-1, access destination information 401-2, and / or time information 105 as inputs, generates a (optical) modulated signal 103 based on these input signals, and outputs the modulated signal 103. The modulated signal 103 is then transmitted, for example, from the light source 104.

[0077] As examples of location information or positional information 101 were explained in Embodiment 1, their explanation will be omitted here.

[0078] Next, we will explain information regarding the SSID (401-1) and information regarding the access destination (401-2).

[0079] First, we will explain information regarding SSIDs (401-1).

[0080] Information regarding the SSID, 401-1, is information indicating the SSID of base station 470 in Figure 9. Here, if it is determined that the SSID notified by the optical signal is the SSID of a secure base station, the first device 400 can provide terminal 450 with access to base station 470, which is a secure access destination. As a result, terminal 450 in Figure 9 can securely obtain information from base station 470.

[0081] On the other hand, the first device 400 can restrict the terminals that access the base station 470 to terminals located in a space where they can receive the optical signals transmitted (irradiated) by the first device 400.

[0082] Furthermore, terminal 450 may determine that the notified SSID is the SSID of a secure base station when it receives an optical signal transmitted in a predetermined manner. Terminal 450 may also perform a separate process to determine whether the notified SSID is secure or not. For example, the first device 400 may transmit a predetermined identifier in the optical signal, and terminal 450 may determine whether the notified SSID is the SSID of a secure base station based on the received identifier. Alternatively, terminal 450 may, without performing a process to determine whether it is a secure base station, use the characteristics of visible light to allow the user to select the first device 400 which is highly secure, and terminal 450 may receive an optical signal from the first device 400 to obtain the SSID of the highly secure base station.

[0083] Although Figure 9 only shows base station 470, if, for example, there is one or more other base stations (or APs) besides base station 470, terminal 450 will access base station 470 using the SSID obtained from the first device 400 and obtain information.

[0084] Next, we will explain information regarding the access destination, 401-2.

[0085] Information regarding the access destination 401-2 is information regarding the access destination that terminal 450 uses to obtain information after accessing base station 470. Specific examples of operation of this embodiment will be described later.

[0086] The above explains information regarding the SSID (401-1) and the access destination (401-2).

[0087] Terminal 450 receives the modulated signal 103 transmitted from the first device 400.

[0088] The light-receiving unit 151 is, for example, an image sensor such as a CMOS or organic CMOS. The light-receiving unit 151 receives light containing a modulated signal transmitted from the first device 400 and outputs a received signal 152.

[0089] The receiving unit 153 then takes the received signal 152 received by the light receiving unit 151 as input, performs demodulation, error correction, and decoding on the modulated signal contained in the received signal 152, and outputs the received data 154.

[0090] The data analysis unit 155 takes the received data 154 as input and estimates, for example, the location of the terminal 450 from the received data 154. The data analysis unit 155 then outputs information 156 that includes at least the location information of the terminal 450, information 451 related to the SSID, and information 452 related to the access destination.

[0091] The display unit 157 receives information 156 including the location information of the terminal 450, information 451 regarding the SSID, and information 452 regarding the access destination as input, and displays, for example, the location of the terminal 450, the SSID of the communication partner accessed by the wireless device 453 equipped with the terminal 450, and / or the access destination (hereinafter, this display will be referred to as the "first display").

[0092] For example, after the first display, the wireless device 453 takes as input information about the SSID 451 and information about the access destination 452. Then, based on the information about the SSID 451, the wireless device 453 connects with the communication partner, for example, by using radio waves. In the case of Figure 9, the wireless device 453 will connect with the base station 470.

[0093] The wireless device 453 then generates a modulated signal from data containing information about the access destination based on the information about the access destination 452, and transmits this modulated signal to the base station 470, for example, using radio waves.

[0094] In Figure 9, the base station 470, which is the communication partner of terminal 450, receives the modulated signal transmitted by the radio device 453 installed in terminal 450.

[0095] The base station 470 then performs processing such as demodulation and error correction decoding of the received modulated signal and outputs received data 471 containing information about the access destination transmitted from the terminal 450. Based on this information about the access destination, the base station 470 accesses the desired access destination via the network and, for example, obtains desired information 472 from the access destination. The base station 470 then takes the desired information 472 as input, generates a modulated signal from the desired information 472, and transmits this modulated signal to the terminal 450 (radio device 453), for example, using radio waves.

[0096] The wireless device 453 of the terminal 450 receives a modulated signal transmitted from the base station 470, performs processing such as demodulation and error correction decoding, and obtains the desired information 472.

[0097] For example, suppose the desired information 472 is information such as maps, building maps / floor guides, facility maps / floor guides, parking lot maps / floor guides, and information on "areas, seats, shops, and facilities" in concert venues, stadiums, airplanes, airport lounges, railways, and stations.

[0098] The display unit 157 receives information 454 including the desired information 472, information 156 including at least the location information of the terminal 450, and information 451 regarding the SSID as input. After the first display, it maps the location of the terminal 450 onto a display of a map, floor guide, facility information, seating information, or store information, using the desired information 472 and the information 156 including at least the location information of the terminal 450.

[0099] Figure 10 shows a specific example of the display on the display unit 157.

[0100] The indication in Figure 10 shows that it is the "3rd floor." A-1, A-2, A-3, A-4, A-21, A-22, A-23, and A-24 indicate the locations of car parking spaces, respectively. Also, a-1 and a-2 indicate the locations of elevators. This map information, including the locations of parking spaces and elevators, is an example of the desired information 454(472).

[0101] As shown in Figure 10, the display unit 157 maps and displays the current location of the terminal 450 on a map. The current location is obtained from information 156, which includes at least the location information of the terminal 450.

[0102] Figure 11 shows an example of the frame structure of the modulated signal transmitted by the first device 400 shown in Figure 9. In Figure 11, the horizontal axis represents time. Also, in Figure 11, symbols that transmit the same information as in Figure 7 are given the same reference numerals, and their explanations are omitted.

[0103] The first device 400 transmits a preamble 201, a control information symbol 202, a symbol 203 relating to location or position information, a symbol 204 relating to time information, as well as a symbol 600-1 relating to the SSID and a symbol 600-2 relating to the access destination.

[0104] Symbol 600-1, which relates to the SSID, is used to transmit information 401-1 regarding the SSID in Figure 9, and symbol 600-2, which relates to the access destination, is used to transmit information 401-2 regarding the access destination in Figure 9. Note that the frame in Figure 11 may contain symbols other than those shown in Figure 11. Furthermore, the frame configuration, including the order in which symbols are transmitted, is not limited to the configuration in Figure 11.

[0105] Figure 12 shows an example of the frame structure of a modulated signal transmitted by base station 470 shown in Figure 9. In Figure 12, the horizontal axis represents time.

[0106] As shown in Figure 12, the base station 470 transmits, for example, a preamble 701, and then transmits a control information symbol 702 and an information symbol 703.

[0107] Preamble 701 is a symbol used by terminal 450, which receives a modulated signal transmitted by base station 470, to perform tasks such as signal detection, time synchronization, frame synchronization, frequency synchronization, and frequency offset estimation.

[0108] The control information symbol 702 is a symbol that contains data such as the error correction coding method used to generate the modulated signal, information about the modulation scheme, and information about the frame configuration. The radio device 453 of the terminal 450 performs demodulation of the modulated signal and other operations based on the information in the control information symbol 702.

[0109] Information symbol 703 is a symbol for transmitting information. In this embodiment, information symbol 703 is a symbol for transmitting the desired information 472 described above.

[0110] Furthermore, the base station 470 shown in Figure 9 may transmit frames containing symbols other than those shown in Figure 12. For example, the base station 470 may transmit frames that include a pilot symbol (reference symbol) in the middle of an information symbol 703. Also, the frame configuration, including the order in which symbols are transmitted, is not limited to the configuration shown in Figure 12. In addition, multiple symbols may exist in the frequency axis direction in Figure 12. That is, symbols may exist on multiple frequencies (multiple carriers) in Figure 12.

[0111] Furthermore, for example, the modulated signal with the frame configuration shown in Figure 11, transmitted by the first device 400, can be transmitted at regular intervals, for example, repeatedly. This allows multiple terminals 450 to perform the operations described above.

[0112] Figure 13 is a flowchart illustrating an example of the processing performed by the "first device 400," "terminal 450," and "base station 470" shown in Figure 9, as described above.

[0113] First, the first device 400 transmits a modulated signal with the frame configuration shown in Figure 11 (ST801).

[0114] Then, terminal 450 receives the modulated signal transmitted by the first device 400 and performs location estimation of terminal 450 (ST802).

[0115] In addition, terminal 450 receives the modulated signal transmitted by the first device 400 and determines the SSID of the base station 470 that terminal 450 is accessing (ST803).

[0116] The terminal 450 then transmits a modulated signal containing data including information 452 about an access destination for obtaining information such as maps to the base station 470, for example, using radio waves (ST804).

[0117] The base station 470 receives the modulated signal transmitted by the terminal 450, obtains information about the access destination, accesses the desired access destination via the network, and obtains desired information such as a map (information to be transmitted to the terminal 450) (ST805).

[0118] Then, base station 470 transmits a modulated signal containing the desired information, such as the acquired map, to terminal 450, for example, using radio waves (ST806).

[0119] Terminal 450 receives the modulated signal transmitted by base station 470 and obtains information such as a map. Then, terminal 450 displays information such as the map and location information already obtained for terminal 450, as shown in Figure 10.

[0120] Next, we will describe an example of operation when multiple first devices 400 and base stations 470 are installed at the location shown in Figure 10.

[0121] Figure 14 shows a map of the same location as Figure 10. That is, Figure 14 is a map of the "3rd floor" as explained in Figure 10. In Figure 14, A-1, A-2, A-3, A-4, A-21, A-22, A-23, and A-24 indicate car parking spaces, and a-1 and a-2 indicate elevators.

[0122] Furthermore, a first device having the same configuration as the first device 400 shown in Figure 9 is installed at the position marked "○" 901-1 in Figure 14. Hereafter, the first device having the same configuration as the first device 400 installed at position 901-1 will be referred to as "device 1-1 400". Device 1-1 400 carries the information "A-1" as location information or position information and transmits the information "A-1".

[0123] A first device having the same configuration as the first device 400 in Figure 9 is installed at the position marked "○" 901-2 in Figure 14. Hereafter, the first device having the same configuration as the first device 400 installed at position 901-2 will be referred to as "the first-second device 400". The first-second device 400 carries the information "A-2" as location information or position information and transmits the information "A-2".

[0124] A first device having the same configuration as the first device 400 in Figure 9 is installed at the position marked "○" 901-3 in Figure 14. Hereafter, the first device having the same configuration as the first device 400 installed at position 901-3 will be referred to as "device 1-3 400". Device 1-3 400 carries the information "A-3" as location information or position information and transmits the information "A-3".

[0125] A first device having the same configuration as the first device 400 in Figure 9 is installed at the position marked "○" 901-4 in Figure 14. Hereafter, the first device having the same configuration as the first device 400 installed at position 901-4 will be referred to as "device 1-4 400". Device 1-4 400 carries the information "A-4" as location information or position information and transmits the information "A-4".

[0126] A first device having the same configuration as the first device 400 in Figure 9 is installed at the location marked "○" 901-21 in Figure 14. Hereafter, the first device having the same configuration as the first device 400 installed at location 901-21 will be referred to as "device 400 1-21". Device 400 1-21 carries the information "A-21" as location information or position information and transmits the information "A-21".

[0127] A first device having the same configuration as the first device 400 in Figure 9 is installed at the location marked "○" 901-22 in Figure 14. Hereafter, the first device having the same configuration as the first device 400 installed at location 901-22 will be referred to as "device 1-22 400". Device 1-22 400 carries the information "A-22" as location information or position information and transmits the information "A-22".

[0128] A first device having the same configuration as the first device 400 in Figure 9 is installed at the location marked "○" 901-23 in Figure 14. Hereafter, the first device having the same configuration as the first device 400 installed at location 901-23 will be referred to as "device 400 1-23". Device 400 1-23 carries the information "A-23" as location information or position information and transmits the information "A-23".

[0129] A first device having the same configuration as the first device 400 in Figure 9 is installed at the location marked "○" 901-24 in Figure 14. Hereafter, the first device having the same configuration as the first device 400 installed at location 901-24 will be referred to as "device 1-24 400". Device 1-24 400 carries the information "A-24" as location information or position information and transmits the information "A-24".

[0130] Furthermore, a base station (or AP) with the same configuration as base station 470 in Figure 9 will be installed at the location marked "◎" 902 in Figure 14. Hereafter, the base station (or AP) with the same configuration as base station 470 in Figure 9 will simply be referred to as "base station 470". Also, here, the SSID of base station 470 installed at location 902 will be "abcdef".

[0131] Terminals 450 located around the location shown on the map in Figure 14 can access the base station 470 located at location 902 in Figure 14 when performing wireless communication.

[0132] Therefore, the "device 400 of the first type" installed at 901-1 in Figure 14 transmits "abcdef" as information related to the SSID (see 401-1 in Figure 9).

[0133] Similarly, "device 400 of the first-second unit" installed at 901-2 in Figure 14 transmits "abcdef" as information related to the SSID (see 401-1 in Figure 9).

[0134] The "First-to-third device 400" installed at 901-3 in Figure 14 transmits "abcdef" as information related to the SSID (see 401-1 in Figure 9).

[0135] The "device 400 of the 1st to 4th" installed at 901-4 in Figure 14 transmits "abcdef" as information related to the SSID (see 401-1 in Figure 9).

[0136] The "device 400 of the 1st-21st unit" located at 901-21 in Figure 14 transmits "abcdef" as information related to the SSID (see 401-1 in Figure 9).

[0137] The "device 400 of the 1st to 22nd" located at 901-22 in Figure 14 transmits "abcdef" as information related to the SSID (see 401-1 in Figure 9).

[0138] The "device 400 of the 1st to 23rd" installed at 901-23 in Figure 14 transmits "abcdef" as information related to the SSID (see 401-1 in Figure 9).

[0139] The "device 400 of the 1st to 24th" located at 901-24 in Figure 14 transmits "abcdef" as information related to the SSID (see 401-1 in Figure 9).

[0140] The following explains specific examples of how it works.

[0141] Assume that a terminal with the same configuration as terminal 450 in Figure 9 (hereinafter simply referred to as "terminal 450") exists at position 903-1 in Figure 14. In this case, terminal 450 receives a modulated signal transmitted by "device 1-4 400" at position 901-4 in Figure 14 and obtains location information "A-4". Terminal 450 also receives a modulated signal transmitted by "device 1-4 400" at position 901-4 in Figure 14 and obtains SSID information "abcdef". As a result, terminal 450 accesses base station 470 located at 902 in Figure 14. Terminal 450 also obtains map information and other information from base station 470 located at 902 in Figure 14. Terminal 450 then displays the map information and location information (see, for example, Figure 10; however, Figure 10 is merely an example of the display).

[0142] Similarly, assume that a terminal with the same configuration as terminal 450 in Figure 9 (hereinafter simply referred to as "terminal 450") exists at position 903-2 in Figure 14. In this case, terminal 450 receives a modulated signal transmitted by "device 400 of the first 22" located at position 901-22 in Figure 14 and obtains the location information "A-22". Terminal 450 also receives a modulated signal transmitted by "device 400 of the first-fourth" located at position 901-22 in Figure 14 and obtains the SSID information "abcdef". As a result, terminal 450 accesses base station 470 located at 902 in Figure 14. Terminal 450 also obtains map information and other information from base station 470 located at 902 in Figure 14. Terminal 450 then displays the map information and location information (see, for example, Figure 10; however, Figure 10 is merely an example of the display).

[0143] Furthermore, the terminal 450 may record a map (surrounding information) and location information, as shown in Figure 14, in a memory unit (not shown) provided by the terminal 450, allowing the user of the terminal 450 to retrieve the information stored in the memory unit when needed. This allows the user to utilize the map (surrounding information) and location information more conveniently.

[0144] As described above, since the first device 400 transmits a modulated signal using visible light, the terminal 450 that can receive this modulated signal is limited to those within the range from the location of the first device 400 that can receive the optical signal. Therefore, by receiving the location information transmitted by the first device 400, the terminal 450 can easily acquire highly accurate location information (without complex signal processing).

[0145] Furthermore, if the first device 400 is installed in a location where it is difficult to receive satellite signals from GPS, the terminal 450 can safely obtain highly accurate location information by receiving the modulated signal transmitted by the first device 400, even in situations where it is difficult to receive signals from GPS satellites.

[0146] Furthermore, based on the SSID information transmitted from the first device 400, terminal 450 can connect to base station (or AP) 470 to obtain information, thereby enabling terminal 450 to securely acquire information. This is because, when terminal 450 obtains information from a visible light modulation signal, the user can easily recognize the first device 400 that transmitted the modulation signal visually, making it easier to determine whether the information source is safe. In contrast, for example, if the SSID is obtained from the modulation signal of radio waves transmitted by a wireless LAN, it is difficult for the user to identify the device that transmitted the radio waves. For this reason, in terms of ensuring the security of information, visible light communication is more suitable for acquiring SSIDs compared to wireless LAN communication.

[0147] Furthermore, multiple signals may be input to the wireless device 453 of terminal 450 in Figure 9. For example, control signals for controlling the wireless device 453 and information to be transmitted to base station 470 may be input to the wireless device 453. In this case, one example of operation is that the wireless device 453 starts communication based on the control signals. As described above, in this embodiment, the configuration of the first device is not limited to the configuration of the first device 400 in Figure 9, the configuration of the terminal is not limited to the configuration of terminal 450 in Figure 9, and the connection destination and configuration of the base station are not limited to the connection destination and configuration of base station 470 shown in Figure 9.

[0148] Furthermore, although Figure 9 describes the case where only one base station 470 is deployed, there may be multiple (secure) base stations (or APs) that the terminal 450 can access. In this case, the SSID symbol transmitted by the first device 400 in Figure 9 may include information indicating the SSID of each of these multiple base stations (or APs). In this case, the display unit 157 of the terminal 450 in Figure 9 will display a list of the SSIDs of multiple base stations and / or a list of multiple access destinations as an access destination display (the "first display" mentioned above). The terminal 450 in Figure 9 may then select one or more base stations to actually connect to wirelessly based on the SSID information of the multiple base stations (or APs) (i.e., it may connect to multiple base stations simultaneously).

[0149] For example, suppose there are three base stations 470. Here, the three base stations 470 are referred to as base station #A, base station #B, and base station #C. Also, the SSID of base station #A is "abcdef", the SSID of base station #B is "ghijk", and the SSID of base station #C is "pqrstu". In this case, the symbol 600-1 related to the SSID in the frame configuration shown in Figure 11 of the modulated signal transmitted by the first device 400 contains the information that "the SSID of base station #A is "abcdef", "the SSID of base station #B is "ghijk", and "the SSID of base station #C is "pqrstu". Then, terminal 450 in Figure 9 receives the symbol 600-1 related to the SSID and selects one or more base stations 470 to actually connect to wirelessly based on the information that "the SSID of base station #A is "abcdef", "the SSID of base station #B is "ghijk", and "the SSID of base station #C is "pqrstu".

[0150] (Embodiment 4) Figure 15 shows an example of the configuration of the communication system in this embodiment.

[0151] The communication system in Figure 15 includes, for example, equipment 1000, terminal 1050, and a base station (or AP) 470 that communicates with terminal 1050.

[0152] Device 1000 includes, for example, a visible light source such as an LED, illumination, light source, or light (hereinafter referred to as light source 104). In the following, device 1000 may also be referred to as the "second device" in this embodiment.

[0153] In Figure 15, components of the second device 1000 that operate similarly to those of the first device 100 shown in Figure 6 are given the same numbers. Similarly, in Figure 15, components of the terminal 1050 that operate similarly to those of the terminal 150 shown in Figure 6 are given the same numbers. Furthermore, communication between the wireless device 453 of the terminal 1050 shown in Figure 15 and the base station 470 is assumed to be conducted using, for example, radio waves.

[0154] In the second device 1000 in Figure 15, the transmitting unit 102 receives SSID information 1001-1, encryption key information 1001-2, and data 1002 as inputs, generates a (optical) modulated signal 103 based on these input signals, and outputs the modulated signal 103. The modulated signal 103 is then transmitted, for example, from a light source 104.

[0155] Next, we will describe the information regarding the SSID (1001-1) and the information regarding the encryption key (1001-2).

[0156] First, we will explain information regarding the SSID, item 1001-1.

[0157] Information 1001-1 regarding the SSID indicates the SSID of base station 470 in Figure 15. For example, base station 470 transmits a modulated signal to terminal 1050 via radio waves and receives a modulated signal from terminal 1050 via radio waves. In other words, the second device 1000 can provide terminal 1050 with access to base station 470, which is a secure access destination. As a result, terminal 1050 in Figure 15 can securely obtain information from base station 470.

[0158] On the other hand, the second device 1000 can restrict the terminals that access the base station 470 to terminals located in a space where they can receive the optical signals transmitted (irradiated) by the second device 1000.

[0159] Furthermore, terminal 1050 may determine that the notified SSID is the SSID of a secure base station when it receives an optical signal transmitted in a predetermined manner. Terminal 1050 may also perform a separate process to determine whether the notified SSID is secure or not. For example, the second device 1000 may transmit a predetermined identifier in the optical signal, and terminal 1050 may determine whether the notified SSID is the SSID of a secure base station based on the received identifier.

[0160] Although Figure 15 only shows base station 470, if, for example, other base stations (or APs) exist besides base station 470, terminal 1050 will access base station 470 using the SSID obtained from the second device 1000 and obtain information.

[0161] Next, we will explain information regarding the encryption key, 1001-2.

[0162] The encryption key information 1001-2 is information about the encryption key that terminal 1050 needs to communicate with base station 470. By obtaining the encryption key information 1001-2 from the second device 1000, terminal 1050 can perform encrypted communication with base station 470.

[0163] The above describes the information regarding the SSID (1001-1) and the information regarding the encryption key (1001-2).

[0164] Terminal 1050 in Figure 15 receives the modulated signal transmitted by the second device 1000. Note that in terminal 1050 in Figure 15, components that operate similarly to terminal 150 in Figure 6 and terminal 450 in Figure 9 are given the same numbers.

[0165] The light-receiving unit 151 of the terminal 1050 is, for example, an image sensor such as a CMOS or organic CMOS. The light-receiving unit 151 receives light containing a modulated signal transmitted from the second device 1000 and outputs a received signal 152.

[0166] The receiving unit 153 then takes the received signal 152 received by the light receiving unit 151 as input, performs demodulation, error correction, and decoding on the modulated signal contained in the received signal 152, and outputs the received data 154.

[0167] The data analysis unit 155 takes the received data 154 as input and outputs, for example, information 1051 about the SSID of the base station to connect to, and information 1052 about the encryption key for communicating with the base station to connect to. For example, in a wireless LAN (Local Area Network), encryption methods include WEP (Wired Equivalent Privacy), WPA (Wi-Fi® Protected Access), and WPA2 (Wi-Fi Protected Access 2) (PSK (Pre-Shared Key) mode, EAP (Extended Authentication Protocol) mode). However, the encryption method is not limited to these.

[0168] The display unit 157 receives SSID information 1051 and encryption key information 1052 as input and displays, for example, the SSID of the communication partner accessed by the wireless device 453 equipped with terminal 1050, and the encryption key (this display is referred to as the "first display" in this embodiment).

[0169] For example, after the first display, the wireless device 453 takes the SSID information 1051 and the encryption key information 1052 as input and establishes a connection with the base station 470 (for example, the connection is made using radio waves). At this time, if the base station 470 is also communicating with the wireless device 453 equipped with terminal 1050, it transmits a modulated signal, for example, using radio waves.

[0170] Subsequently, the wireless device 453 receives data 1053 and control signal 1054 as input, modulates data 1053 according to the control indicated in control signal 1054, and transmits the modulated signal by radio waves.

[0171] Then, for example, base station 470 transmits data to the network (471) and receives data from the network (472). After that, for example, base station 470 transmits a modulated signal to terminal 1050 via radio waves.

[0172] The wireless device 453 of terminal 1050 performs processing such as demodulation and error correction decoding on the modulated signal received by radio waves and acquires received data 1056. The display unit 157 displays information based on the received data 1056.

[0173] Figure 16 shows an example of the frame structure of a modulated signal transmitted by the second device 1000 shown in Figure 15. In Figure 16, the horizontal axis represents time. Also, in Figure 16, symbols similar to those in Figures 7 and 11 are given the same numbers, and their explanations are omitted.

[0174] Symbol 600-1, which relates to the SSID, is a symbol for transmitting information 1001-1 related to the SSID in Figure 15, and symbol 1101, which relates to the encryption key, is a symbol for transmitting information 1001-2 related to the encryption key in Figure 15. Data symbol 1102 is a symbol for transmitting data 1002 in Figure 15.

[0175] The second device 1000 transmits the preamble 201, the control information symbol 202, the SSID symbol 600-1, the encryption key symbol 1101, and the data symbol 1102. The second device 1000 may also transmit frames containing symbols other than those shown in Figure 16. Furthermore, the frame configuration, including the order in which symbols are transmitted, is not limited to the configuration shown in Figure 16.

[0176] Figure 17 shows an example of the frame structure of a modulated signal transmitted by the wireless device 453 equipped with terminal 1050 in Figure 15. In Figure 17, the horizontal axis represents time.

[0177] As shown in Figure 17, the wireless device 453 of terminal 1050 transmits, for example, a preamble 1201, and then a control information symbol 1202 and an information symbol 1203.

[0178] The preamble 1201 is a symbol used by the base station 470, which receives the modulated signal transmitted by the radio device 453 of the terminal 1050, for purposes such as signal detection, time synchronization, frame synchronization, frequency synchronization, and frequency offset estimation.

[0179] The control information symbol 1202 is a symbol that contains data such as the error correction coding method used to generate the modulated signal, information about the modulation scheme, information about the frame configuration, and information about the transmission method. Based on the information contained in the control information symbol 1202, the base station 470 performs tasks such as demodulating the modulated signal.

[0180] Information symbol 1203 is a symbol used by the wireless device 453 of terminal 1050 to transmit data.

[0181] Furthermore, the wireless device 453 of terminal 1050 may transmit frames containing symbols other than those shown in Figure 17. For example, the wireless device 453 may transmit a frame that includes a pilot symbol (reference symbol) in the middle of the information symbol 1203. Also, the frame configuration, including the order in which symbols are transmitted, is not limited to the configuration in Figure 17. In addition, in Figure 17, there may be multiple symbols in the frequency axis direction. That is, in Figure 17, there may be symbols on multiple frequencies (multiple carriers). Furthermore, in Embodiment 3, when the wireless device 453 of terminal 450 in Figure 9 transmits a modulation signal, the frame configuration in Figure 17 may be used.

[0182] The frame configuration of the modulated signal transmitted by the base station 470 in this embodiment is the same as the frame configuration shown in Figure 12 described in Embodiment 3. That is, as shown in Figure 12, the base station 470 transmits, for example, a preamble 701, and then transmits a control information symbol 702 and an information symbol 703.

[0183] The preamble 701 is a symbol used by the radio equipment 453 of the terminal 1050, which receives the modulated signal transmitted by the base station 470, to perform tasks such as signal detection, time synchronization, frame synchronization, frequency synchronization, and frequency offset estimation.

[0184] The control information symbol 702 is a symbol that contains data such as the error correction coding method used to generate the modulated signal, information about the modulation scheme, information about the frame configuration, and information about the transmission method. The radio device 453 of terminal 1050 performs demodulation of the modulated signal and other operations based on the information in the control information symbol 702.

[0185] Information symbol 703 is a symbol used by base station 470 to transmit data.

[0186] Furthermore, the base station 470 shown in Figure 15 may transmit frames containing symbols other than those described in Figure 12. For example, the base station 470 may transmit frames that include a pilot symbol (reference symbol) in the middle of an information symbol 703. Also, the frame configuration, including the order in which symbols are transmitted, is not limited to the configuration in Figure 12. In addition, multiple symbols may exist in the frequency axis direction in Figure 12. That is, symbols may exist on multiple frequencies (multiple carriers) in Figure 12.

[0187] Furthermore, for example, the modulated signal in the frame configuration shown in Figure 16 transmitted by the second device 1000 can be transmitted repeatedly at regular intervals. This allows multiple terminals 1050 to perform the operations described above.

[0188] Figure 18 is a flowchart showing an example of the processing performed by the "second device 1000," "terminal 1050," and "base station 470" shown in Figure 15.

[0189] First, the second device 1000 transmits a modulated signal with the frame configuration shown in Figure 16 (ST1301).

[0190] Then, terminal 1050 receives the modulated signal transmitted by the second device 1000 and obtains the SSID of the base station 470 that terminal 1050 is accessing (ST1302).

[0191] In addition, terminal 1050 acquires an encryption key to be used for communication with base station 470 that terminal 1050 accesses (ST1303).

[0192] Then, terminal 1050 establishes a radio connection with base station 470 (ST1304). When terminal 1050 receives a response from base station 470, the connection with base station 470 is completed (ST1305).

[0193] Then, terminal 1050 transmits information about the connection destination to base station 470 using radio waves (ST1306).

[0194] Base station 470 obtains information from the network to be transmitted to terminal 1050 (ST1307).

[0195] Then, the base station 470 transmits the acquired information to the terminal 1050 using radio waves, and the terminal 1050 receives the information (ST1308). The terminal 1050, for example, obtains necessary information from the network via the base station 470 when needed.

[0196] As described above, based on the SSID information and encryption key information transmitted from the second device 1000, terminal 1050 connects to base station 470 and acquires the information, thereby securely obtaining the information via the base station 470, which is guaranteed to be secure. This is because when terminal 1050 obtains information from a visible light modulation signal, it is easier for the user to determine whether the information source is secure because it is visible light. In contrast, for example, if the SSID is obtained from the modulation signal of radio waves transmitted by a wireless LAN, it is difficult for the user to identify the device that transmitted the radio waves. For this reason, in terms of ensuring the security of information, visible light communication is more suitable for obtaining the SSID compared to wireless LAN communication.

[0197] In this embodiment, the case in which the second device 1000 transmits encryption key information has been described. However, for example, if the base station 470 is not performing encrypted communication using an encryption key, the second device 1000 may not transmit encryption key information and may only transmit information related to the SSID. In this case, the same configuration can be implemented by simply removing the encryption key-related configuration from the above-described configuration.

[0198] Furthermore, the configuration of the second device is not limited to the configuration of the second device 1000 shown in Figure 15, the configuration of the terminal is not limited to the configuration of the terminal 1050 shown in Figure 15, and the connection destination and configuration of the base station are not limited to the connection destination and configuration of the base station 470 shown in Figure 15.

[0199] Furthermore, although Figure 15 describes the case where only one base station 470 is deployed, there may be multiple (secure) base stations (or APs) that the terminal 1050 can access. These multiple base stations and the terminal 1050 will each transmit and receive modulated signals using radio waves. In this case, the SSID symbol transmitted by the second device 1000 in Figure 15 may include the SSID information of each of these multiple base stations (or APs). In this case, the display unit 157 of the terminal 1050 in Figure 15 will display a list of the SSIDs of the multiple base stations and / or a list of multiple access destinations as an indication of the access destinations. Also, the encryption key symbol transmitted by the second device 1000 in Figure 15 may include the encryption key information used to connect to each of these multiple base stations (or APs). Then, the terminal 1050 in Figure 15 may select one or more base stations to actually connect to wirelessly (for example, by radio waves) based on the SSID information and encryption key information of the multiple base stations (i.e., it may connect to multiple base stations simultaneously).

[0200] For example, suppose three base stations 470 are deployed. Here, the three base stations 470 will be called base station #A, base station #B, and base station #C. Also, the SSID of base station #A will be "abcdef", the SSID of base station #B will be "ghijk", and the SSID of base station #C will be "pqrstu". Furthermore, the encryption key for connecting to base station #A will be "123", the encryption key for connecting to base station #B will be "456", and the encryption key for connecting to base station #C will be "789".

[0201] In this case, the symbol 600-1 related to the SSID in the frame configuration of Figure 16 of the modulated signal transmitted by the second device 1000 contains the information that "the SSID of base station #A is "abcdef"", "the SSID of base station #B is "ghijk"", and "the SSID of base station #C is "pqrstu". In addition, the symbol 1101 related to the encryption key in the frame configuration of Figure 16 contains the information that "the encryption key for connecting to base station #A is "123"", "the encryption key for connecting to base station #B is "456"", and "the encryption key for connecting to base station #C is "789".

[0202] Then, terminal 1050 in Figure 15 receives symbol 600-1 related to SSIDs and obtains the information that "the SSID of base station #A is "abcdef"", "the SSID of base station #B is "ghijk"", and "the SSID of base station #C is "pqrstu". Terminal 1050 also receives symbol 1101 related to encryption keys and obtains the information that "the encryption key for connecting to base station #A is "123"", "the encryption key for connecting to base station #B is "456"", and "the encryption key for connecting to base station #C is "789". Based on this information, terminal 1050 selects one or more base stations to actually connect to wirelessly (for example, by radio waves) and connects to them.

[0203] Furthermore, as in this embodiment, by using a light source such as an LED to configure the base station 470 that the terminal 1050 accesses, a special setting mode for the wireless connection procedure between the terminal 1050 and the base station 470 is not required in the modulation signal for wireless communication transmitted by the terminal 1050. Similarly, a special setting mode for the wireless connection procedure between the terminal 1050 and the base station 470 is not required in the modulation signal transmitted by the base station 470. Therefore, in this embodiment, the data transmission efficiency of wireless communication can be improved.

[0204] Furthermore, as mentioned above, the encryption key may be an encryption key for the wireless LAN's SSID, or it may be an encryption key used to restrict connection type, service type, network coverage area, etc. In other words, an encryption key should be introduced for some purpose of restriction.

[0205] (Embodiment 5) Figure 19 shows an example of the configuration of the communication system in this embodiment.

[0206] The communication system in Figure 19 includes, for example, equipment 1400A, 1400B, terminal 1050, and a base station (or AP) 470 that communicates with terminal 1050.

[0207] Devices 1400A and 1400B are equipped with, for example, visible light sources such as LEDs, illumination, light sources, and lights (hereinafter referred to as light sources 1406-1 and 1406-2). In the following description, device 1400A will be referred to as the "third device" in this embodiment, and device 1400B will be referred to as the "fourth device" in this embodiment.

[0208] In Figure 19, components of terminal 1050 that operate similarly to those of terminal 150 in Figure 1 or terminal 1050 in Figure 15 are given the same numbers. Similarly, in Figure 19, components of base station (or AP) 470 that operate similarly to those of base station 470 in Figure 9 are given the same numbers as those in Figure 9. Furthermore, communication between the wireless device 453 of terminal 1050 and base station 470 in Figure 19 is assumed to be conducted using, for example, radio waves.

[0209] In the third device 1400A in Figure 19, the transmitter 1404-1 receives SSID information 1401-1 and data 1402-1 as inputs, generates a (optical) modulated signal 1405-1 based on these input signals, and outputs the modulated signal 1405-1. The modulated signal 1405-1 is then transmitted, for example, from the light source 1406-1.

[0210] In the fourth device 1400B in Figure 19, the transmitter 1404-2 receives information about the encryption key 1403-2 and data 1402-2 as inputs, generates a (optical) modulated signal 1405-2 based on these input signals, and outputs the modulated signal 1405-2. The modulated signal 1405-2 is then transmitted, for example, from the light source 1406-2.

[0211] Next, we will explain information regarding the SSID (1401-1) and information regarding the encryption key (1403-2).

[0212] First, we will explain information regarding SSIDs (1401-1).

[0213] Information 1401-1 regarding the SSID indicates the SSID of base station 470 in Figure 19. In other words, the third device 1400A can provide terminal 1050 with access to base station 470, which is a secure access destination via radio waves. As a result, terminal 1050 in Figure 19 can securely obtain information from base station 470.

[0214] Furthermore, terminal 1050 may determine that the notified SSID is the SSID of a secure base station when it receives an optical signal transmitted in a predetermined manner. Terminal 1050 may also perform a separate process to determine whether the notified SSID is secure or not. For example, the third device 1400A may transmit a predetermined identifier in the optical signal, and terminal 1050 may determine whether the notified SSID is the SSID of a secure base station based on the received identifier.

[0215] Although Figure 19 only shows base station 470, if, for example, other base stations (or APs) exist besides base station 470, terminal 1050 will access base station 470 and obtain information using the SSID obtained from the third device 1400A and the encryption key obtained from the fourth device 1400B.

[0216] Next, we will explain information regarding the cryptographic key, 1403-2.

[0217] The encryption key information 1403-2 is information about the encryption key necessary for terminal 1050 to communicate with base station 470 by radio waves. By obtaining the encryption key information 1403-2 from the fourth device 1400B, terminal 1050 can perform encrypted communication with base station 470.

[0218] The above explains the information regarding the SSID (1401-1) and the information regarding the encryption key (1403-2).

[0219] Terminal 1050 in Figure 19 receives the modulated signal transmitted by the third device 1400A.

[0220] The light-receiving unit 151 of the terminal 1050 is, for example, an image sensor such as a CMOS or organic CMOS. The light-receiving unit 151 receives light including a modulated signal transmitted from the third device 1400A and outputs a received signal 152.

[0221] The receiving unit 153 then takes the received signal 152 received by the light receiving unit 151 as input, performs demodulation, error correction, and decoding on the modulated signal contained in the received signal 152, and outputs the received data 154.

[0222] The data analysis unit 155 takes the received data 154 as input and outputs, for example, information 1051 of the SSID of the base station to be connected to from the received data. The wireless device 453 obtains the SSID information of the base station 470 to which the wireless device 453 will connect via radio waves from the SSID information 1051.

[0223] Terminal 1050 in Figure 19 receives the modulated signal transmitted by the fourth device 1400B.

[0224] The light-receiving unit 151 of the terminal 1050 is, for example, an image sensor such as a CMOS or organic CMOS. The light-receiving unit 151 receives light containing a modulated signal transmitted from the fourth device 1400B and outputs a received signal 152.

[0225] The receiving unit 153 then takes the received signal 152 received by the light receiving unit 151 as input, performs demodulation, error correction, and decoding on the modulated signal contained in the received signal 152, and outputs the received data 154.

[0226] The data analysis unit 155 takes the received data 154 as input and outputs, for example, encryption key information 1052 for communicating with the base station to be connected to. For example, in a wireless LAN (Local Area Network), encryption methods include WEP (Wired Equivalent Privacy), WPA (Wi-Fi Protected Access), and WPA2 (Wi-Fi Protected Access 2) (PSK (Pre-Shared Key) mode, EAP (Extended Authentication Protocol) mode). There are other methods as well. Note that these are not the only encryption methods available.

[0227] The wireless device 453 equipped with terminal 1050 obtains the encryption key information of the base station 470 to which the wireless device 453 is connected from the encryption key information 1052 for communicating with the base station to which it is connected (for example, by radio waves).

[0228] The display unit 157 receives SSID information 1051 and encryption key information 1052 as input and displays, for example, the SSID of the communication partner accessed by the wireless device 453 equipped with terminal 1050, and the encryption key (this display is referred to as the "first display" in this embodiment).

[0229] For example, after the first display, the wireless device 453 takes the SSID information 1051 and the encryption key information 1052 as input and establishes a radio connection with the base station 470. At this time, if the base station 470 is also communicating with the wireless device 453 equipped with terminal 1050, it transmits a modulated signal, for example, using radio waves.

[0230] Subsequently, the wireless device 453 receives data 1053 and control signal 1054 as input, modulates data 1053 according to the control indicated in control signal 1054, and transmits the modulated signal by radio waves.

[0231] Then, for example, base station 470 transmits data to the network (471) and receives data from the network (472). After that, for example, base station 470 transmits a modulated signal to terminal 1050 via radio waves.

[0232] The wireless device 453 of terminal 1050 performs processing such as demodulation and error correction decoding on the modulated signal received by radio waves and acquires received data 1056. The display unit 157 displays information based on the received data 1056.

[0233] Figure 20 shows an example of the frame structure of the modulated signal transmitted by the third device 1400A shown in Figure 19. In Figure 20, the horizontal axis represents time. Also, in Figure 20, the same symbols as in Figures 2, 11, and 16 are denoted by the same reference numerals, and their explanations are omitted.

[0234] Symbol 600-1, which relates to the SSID, is the symbol used to transmit the SSID information 1401-1 shown in Figure 19. Data symbol 1102 is the symbol used to transmit data 1402-1.

[0235] The third device 1400A transmits the preamble 201, control information symbol 202, SSID-related symbol 600-1, and data symbol 1102. The third device 1400A may also transmit frames containing symbols other than those shown in Figure 20. Furthermore, the frame configuration, including the order in which symbols are transmitted, is not limited to the configuration shown in Figure 20.

[0236] FIG. 21 illustrates an example of a frame configuration of a modulation signal transmitted by the fourth device 1400B in FIG. 19. In FIG. 21, the horizontal axis represents time. In addition, in FIG. 21, symbols that are the same as those in FIGS. 7 and 16 are assigned the same reference numerals, and descriptions thereof are omitted.

[0237] The symbol 1101 related to an encryption key is a symbol for transmitting information 1403-2 related to the encryption key in FIG. 19. The data symbol 1102 is a symbol for transmitting data 1402-2.

[0238] The fourth device 1400B transmits a preamble 201, a control information symbol 202, the encryption key-related symbol 1101, and the data symbol 1102. Note that the fourth device 1400B in FIG. 19 may transmit a frame including symbols other than the symbols described in FIG. 21. In addition, the frame configuration, including the order in which symbols are transmitted, is not limited to that shown in FIG. 21.

[0239] The frame configuration of a modulation signal transmitted by the wireless device 453 in the present embodiment is the same as the frame configuration in FIG. 17 described in Embodiment 4. That is, as shown in FIG. 17, the wireless device 453 included in the terminal 1050 transmits, for example, a preamble 1201, and thereafter transmits a control information symbol 1202 and an information symbol 1203.

[0240] The preamble 1201 is a symbol used by a base station (or AP) 470 that receives a modulation signal transmitted by the wireless device 453 of the terminal 1050 in FIG. 19, for example, to perform signal detection, time synchronization, frame synchronization, frequency synchronization, frequency offset estimation, and the like.

[0241] The control information symbol 1202 is a symbol including data such as, for example, an error correction coding scheme method used to generate the modulation signal, information related to a modulation scheme, information related to a frame configuration, and information related to a transmission method. The base station 470 performs demodulation of the modulation signal and the like based on information included in the control information symbol 1202.

[0242] Information symbol 1203 is a symbol used by the wireless device 453 of terminal 1050 to transmit data.

[0243] Furthermore, the wireless device 453 of terminal 1050 shown in Figure 19 may transmit frames containing symbols other than those described in Figure 17. For example, the wireless device 453 may transmit frames that include a pilot symbol (reference symbol) in the middle of an information symbol 1203. Also, the frame configuration, including the order in which symbols are transmitted, is not limited to the configuration in Figure 17. In addition, in Figure 17, multiple symbols may exist in the frequency axis direction. That is, in Figure 17, symbols may exist on multiple frequencies (multiple carriers).

[0244] The frame configuration of the modulated signal transmitted by the base station 470 in this embodiment is the same as the frame configuration shown in Figure 12 described in Embodiment 3. That is, as shown in Figure 12, the base station 470 transmits, for example, a preamble 701, and then transmits a control information symbol 702 and an information symbol 703.

[0245] The preamble 701 is a symbol used by the radio equipment 453 of terminal 1050 in Figure 19, which receives the modulated signal transmitted by base station 470, to perform tasks such as signal detection, time synchronization, frame synchronization, frequency synchronization, and frequency offset estimation.

[0246] The control information symbol 702 is a symbol that contains data such as the error correction coding method used to generate the modulated signal, information about the modulation scheme, information about the frame configuration, and information about the transmission method. The radio device 453 of terminal 1050 in Figure 19 performs demodulation of the modulated signal and other operations based on the information in the control information symbol 702.

[0247] Information symbol 703 is a symbol used by base station 470 in Figure 19 to transmit data.

[0248] Furthermore, the base station 470 shown in Figure 19 may transmit frames containing symbols other than those described in Figure 12. For example, the base station 470 may transmit frames that include a pilot symbol (reference symbol) in the middle of an information symbol 703. Also, the frame configuration, including the order in which symbols are transmitted, is not limited to the configuration in Figure 12. In addition, multiple symbols may exist in the frequency axis direction in Figure 12. That is, symbols may exist on multiple frequencies (multiple carriers) in Figure 12.

[0249] Furthermore, for example, the modulated signal with the frame configuration shown in Figure 20 transmitted by the third device 1400A could be transmitted repeatedly at regular intervals. This would allow multiple terminals 1050 to perform the operations described above. Similarly, the modulated signal with the frame configuration shown in Figure 21 transmitted by the fourth device 1400B could be transmitted repeatedly at regular intervals. This would allow multiple terminals 1050 to perform the operations described above.

[0250] Figure 22 is a flowchart illustrating a first example of the processing performed by the "third device 1400A," "fourth device 1400B," "terminal 1050," and "base station 470" shown in Figure 19. In Figure 22, components that operate similarly to those in Figure 18 are given the same numbers.

[0251] First, the third device 1400A transmits a modulated signal with the frame configuration shown in Figure 20 (ST1701).

[0252] Then, terminal 1050 receives the modulated signal transmitted by the third device 1400A and obtains the SSID of base station 470 that terminal 1050 is accessing (ST1702).

[0253] Next, the fourth device 1400B transmits a modulated signal with the frame configuration shown in Figure 21 (ST1703).

[0254] Then, receive the modulated signal transmitted by the terminal 1050 and the fourth device 1400B, and acquire an encryption key used for communication with the base station 470 accessed by the terminal 1050 (ST1704).

[0255] Then, the terminal 1050 establishes a radio wave connection with the base station 470 (ST1304). When the terminal 1050 receives a response from the base station 470, the radio wave connection with the base station 470 is completed (ST1305).

[0256] Then, the terminal 1050 transmits connection destination information to the base station 470 using radio waves (ST1306).

[0257] The base station 470 acquires information to be transmitted to the terminal 1050 from the network (ST1307).

[0258] Then, the base station 470 transmits the acquired information to the terminal 1050 using radio waves, and the terminal 1050 obtains the information (ST1308). For example, when necessary, the terminal 1050 acquires necessary information from the network via the base station 470.

[0259] FIG. 23 is a flowchart showing a second example of processing performed by the "third device 1400A", "fourth device 1400B", "terminal 1050", and "base station 470" shown in FIG. 19. In FIG. 23, components that operate in the same manner as in FIG. 18 are assigned the same reference numerals.

[0260] First, the fourth device 1400B transmits a modulated signal having the frame configuration shown in FIG. 21 (ST1801).

[0261] Then, the terminal 1050 receives the modulated signal transmitted by the fourth device 1400B, and acquires an encryption key used for communication with the base station 470 accessed by the terminal 1050 (ST1802).

[0262] Next, the third device 1400A transmits a modulated signal having the frame configuration shown in FIG. 20 (ST1803).

[0263] Then, terminal 1050 receives the modulated signal transmitted by the third device 1400A and obtains the SSID of base station 470 that terminal 1050 is accessing (ST1804).

[0264] Then, terminal 1050 establishes a radio connection with base station 470 (ST1304). When terminal 1050 receives a response from base station 470, the radio connection with base station 470 is completed (ST1305).

[0265] Then, terminal 1050 transmits information about the connection destination to base station 470 using radio waves (ST1306).

[0266] Base station 470 obtains information from the network to be transmitted to terminal 1050 (ST1307).

[0267] Then, the base station 470 transmits the acquired information to the terminal 1050 using radio waves, and the terminal 1050 receives the information (ST1308). The terminal 1050, for example, obtains necessary information from the network via the base station 470 when needed.

[0268] As described above, terminal 1050 connects to base station 470 and acquires information based on the SSID transmitted from the third device 1400A and the encryption key information transmitted from the fourth device 1400B. In other words, since terminal 1050 acquires SSID information from one device and acquires encryption key information from another, it can securely obtain information via base station 470, which is guaranteed to be secure. This is because when terminal 1050 obtains information from a visible light modulation signal, it is easier for the user to determine whether the information source is secure because it is visible light. In contrast, for example, if the SSID is acquired from a modulation signal of radio waves transmitted by a wireless LAN, it is difficult for the user to identify the device that transmitted the radio waves. For this reason, in terms of ensuring the security of information, visible light communication is more suitable for acquiring SSIDs compared to wireless LAN communication.

[0269] In this embodiment, the case in which the fourth device 1400B transmits encryption key information has been described. However, for example, if the base station 470 does not perform encrypted communication using an encryption key, the fourth device 1400B does not transmit encryption key information, and only the third device 1400A needs to transmit information related to the SSID. In this case, the same configuration can be implemented by simply removing the encryption key configuration from the above-described configuration.

[0270] Furthermore, as in this embodiment, by separating the device that transmits information about the SSID (third device 1400A) from the device that transmits information about the encryption key (fourth device 1400B), the terminal 1050 can achieve more secure communication with the base station 470.

[0271] For example, consider a space like the one in Figure 24. In Figure 24, there are Area #1 and Area #2, with an entrance and a wall separating Area #1 and Area #2. That is, in the space of Figure 24, movement from Area #1 to Area #2, and movement from Area #2 to Area #1, is only possible through the entrance.

[0272] In Figure 24, area #1 is assumed to have base station 470, third equipment 1400A, and fourth equipment 1400B installed. On the other hand, area #2 is assumed to have only third equipment 1400A installed. Furthermore, in Figure 24, it is assumed that the radio waves transmitted by base station 470 can be received in both area #1 and area #2.

[0273] At this time, terminal 1050 located in area #1 where the fourth device 1400B is installed can obtain the encryption key for base station 470 from the fourth device 1400B and communicate with base station 470. Furthermore, even if terminal 1050 that has connected with base station 470 in area #1 moves to area #2, it can communicate with base station 470 using the encryption key obtained from the fourth device 1400B in area #1. Also, even if terminal 1050 that has connected with base station 470 in area #1 moves to an area other than area #1 or area #2 and then returns to either area #1 or area #2, it can communicate with base station 470 using the encryption key obtained from the fourth device 1400B in area #1.

[0274] On the other hand, terminal 1050, which cannot enter area #1, cannot obtain the encryption key from the fourth device 1400B. In this case, terminal 1050 only knows the SSID of base station (or AP) 470. Therefore, for example, terminal 1050 may be allowed to receive communication with base station 470 through services that can be enjoyed by knowing only the SSID of base station 470. The services that can be enjoyed by knowing only the SSID of base station 470 can be more limited than the services that can be enjoyed when both the SSID and the encryption key are known.

[0275] Therefore, only terminal 1050, which was able to enter area #1, will be able to communicate with base station 470. This ensures the security of communications. It also makes it possible to build a system that can provide different services in each area.

[0276] Furthermore, by changing the encryption key that terminal 1050 uses to communicate with base station 470 (for example, every certain time interval), terminal 1050 that retains the previous encryption key will no longer be able to communicate with base station 470. This type of operation makes it possible to achieve more secure communication.

[0277] Furthermore, the configuration of the third and fourth devices is not limited to the configurations of the third device 1400A and the fourth device 1400B shown in Figure 19, the configuration of the terminal is not limited to the configuration of terminal 1050 shown in Figure 19, and the connection destination and configuration of the base station are not limited to the connection destination and configuration of base station 470 shown in Figure 19.

[0278] Furthermore, although Figure 19 describes the case where only one base station 470 is deployed, there may be multiple (secure) base stations (or APs) that the terminal 1050 can access. In this case, the SSID symbol transmitted by the third device 1400A in Figure 19 may include the SSID information of each of these multiple base stations 470. Also, the encryption key symbol transmitted by the fourth device 1400B in Figure 19 may include the encryption key information used to connect to each of these multiple base stations. In this case, the display unit 157 of the terminal 1050 in Figure 19 will display a list of the SSIDs of multiple base stations and / or a list of multiple access destinations as an access destination display (the "first display" mentioned above). The terminal 1050 in Figure 19 may then select one or more base stations to actually connect to wirelessly based on the SSID information and encryption key information of the multiple base stations (i.e., it may connect to multiple base stations simultaneously).

[0279] For example, suppose three base stations 470 are deployed. Here, the three base stations 470 will be called base station #A, base station #B, and base station #C. Also, the SSID of base station #A will be "abcdef", the SSID of base station #B will be "ghijk", and the SSID of base station #C will be "pqrstu". Furthermore, the encryption key for connecting to base station #A will be "123", the encryption key for connecting to base station #B will be "456", and the encryption key for connecting to base station #C will be "789".

[0280] In this case, the symbol 600-1 related to the SSID in the frame configuration of Figure 20 of the modulated signal transmitted by the third device 1400A contains information that "the SSID of base station #A is "abcdef"", "the SSID of base station #B is "ghijk"", and "the SSID of base station #C is "pqrstu". Also, the symbol 1101 related to the encryption key in the frame configuration of Figure 21 of the modulated signal transmitted by the fourth device 1400B contains information that "the encryption key for connecting to base station #A is "123"", "the encryption key for connecting to base station #B is "456"", and "the encryption key for connecting to base station #C is "789".

[0281] Then, terminal 1050 in Figure 19 receives symbol 600-1 related to SSIDs and obtains the information that "the SSID of base station #A is "abcdef"", "the SSID of base station #B is "ghijk"", and "the SSID of base station #C is "pqrstu". Terminal 1050 also receives symbol 1101 related to encryption keys and obtains the information that "the encryption key for connecting to base station #A is "123"", "the encryption key for connecting to base station #B is "456"", and "the encryption key for connecting to base station #C is "789". Based on this information, terminal 1050 selects a base station to connect to wirelessly (for example, by radio waves) and connects to it.

[0282] Furthermore, as in this embodiment, by using a light source such as an LED to configure the base station 470 that the terminal 1050 accesses, a special setting mode for the wireless connection procedure between the terminal 1050 and the base station 470 is not required in the modulation signal for wireless communication transmitted by the terminal 1050. Similarly, a special setting mode for the wireless connection procedure between the terminal 1050 and the base station 470 is not required in the modulation signal transmitted by the base station 470. Therefore, in this embodiment, the data transmission efficiency of wireless communication can be improved.

[0283] Furthermore, as mentioned above, the encryption key may be an encryption key for the wireless LAN's SSID, or it may be an encryption key used to restrict connection type, service type, network coverage area, etc. In other words, an encryption key should be introduced for some purpose of restriction.

[0284] (Embodiment 6) Figure 25 shows an example of the configuration of the communication system in this embodiment.

[0285] The communication system in Figure 25 includes, for example, a base station 2000 and a terminal 1050. The base station 2000 also includes a transmitter 2001 and a radio device 2002. In Figure 25, components that operate similarly to those in Figures 6 and 15 are given the same numbers. Furthermore, communication between the radio device 2002 and the radio device 453 in Figure 25 is assumed to use, for example, radio waves.

[0286] The transmitter 2001 of the base station (or AP) 2000 in Figure 25 is equipped with, for example, a visible light source such as an LED, illumination, light source, or light (hereinafter referred to as light source 104). First, the operation of the transmitter 2001 (that is, "the part related to the visible light source such as an LED, illumination, light source, or light") will be explained.

[0287] In the transmitting device 2001, the transmitting unit 102 receives SSID information 1001-1, encryption key information 1001-2, and data 1002 as inputs, generates a (optical) modulated signal 103 based on these input signals, and outputs the modulated signal 103. The modulated signal 103 is then transmitted, for example, from a light source 104.

[0288] Next, we will describe the information regarding the SSID (1001-1) and the information regarding the encryption key (1001-2).

[0289] First, we will explain information regarding the SSID, item 1001-1.

[0290] Information 1001-1 regarding the SSID indicates the SSID of the radio device 2002 of the base station 2000 in Figure 25. In other words, the transmitting device 2001 can provide terminal 1050 with secure wireless access to the radio device 2002. This allows terminal 1050 in Figure 25 to securely obtain information from the radio device 2002.

[0291] On the other hand, the transmitting device 2001 can restrict the terminals that access the wireless device 2002 to terminals located in a space where they can receive the optical signal transmitted (irradiated) by the transmitting device 2001.

[0292] Furthermore, terminal 1050 may determine that the notified SSID is the SSID of a secure base station when it receives an optical signal transmitted in a predetermined manner. Terminal 1050 may also perform a separate process to determine whether the notified SSID is secure or not. For example, the transmitting device 2001 may include a predetermined identifier in the optical signal and transmit it, and terminal 1050 may determine whether the notified SSID is the SSID of a secure base station based on the received identifier.

[0293] Although Figure 25 only shows base station 2000, if, for example, other base stations (or APs) exist besides base station 2000, terminal 1050 will access the wireless device 2002 of base station 2000 using the SSID and encryption key obtained from the transmitting device 2001 to obtain the information.

[0294] Next, we will explain information regarding the encryption key, 1001-2.

[0295] The encryption key information 1001-2 is information about the encryption key that terminal 1050 needs to communicate with wireless device 2002. By obtaining the encryption key information 1001-2 from transmitting device 2001, terminal 1050 can perform encrypted communication with wireless device 2002.

[0296] The above describes the information regarding the SSID (1001-1) and the information regarding the encryption key (1001-2).

[0297] Terminal 1050 in Figure 25 receives the modulated signal transmitted by the transmitting device 2001. Note that in terminal 1050 in Figure 25, components that operate similarly to terminal 150 in Figure 6 and terminal 1050 in Figure 15 are given the same numbers.

[0298] The light-receiving unit 151 of the terminal 1050 is, for example, an image sensor such as a CMOS or organic CMOS. The light-receiving unit 151 receives light containing a modulated signal transmitted from the transmitting device 2001 and outputs a received signal 152.

[0299] The receiving unit 153 then takes the received signal 152 received by the light receiving unit 151 as input, performs demodulation, error correction, and decoding on the modulated signal contained in the received signal 152, and outputs the received data 154.

[0300] The data analysis unit 155 takes the received data 154 as input and outputs, for example, information 1051 about the SSID of the wireless device 2002 of the base station 2000 to be connected to, and information 1052 about the encryption key for communicating with the wireless device 2002 of the base station 2000 to be connected to. For example, in a wireless LAN (Local Area Network), encryption methods include WEP (Wired Equivalent Privacy), WPA (Wi-Fi Protected Access), and WPA2 (Wi-Fi Protected Access 2) (PSK (Pre-Shared Key) mode, EAP (Extended Authentication Protocol) mode). However, the encryption method is not limited to these.

[0301] The display unit 157 receives SSID information 1051 and encryption key information 1052 as input and displays, for example, the SSID of the communication partner accessed by the wireless device 453 equipped with terminal 1050, and the encryption key (this display is referred to as the "first display" in this embodiment).

[0302] For example, after the first display, the wireless device 453 takes the SSID information 1051 and the encryption key information 1052 as input and establishes a connection with the wireless device 2002 of the base station 2000 (for example, the connection is made using radio waves). At this time, if the wireless device 2002 of the base station 2000 is also communicating with the wireless device 453 equipped on the terminal 1050, it transmits a modulated signal, for example, using radio waves.

[0303] Subsequently, the wireless device 453 receives data 1053 and control signal 1054 as input, modulates data 1053 according to the control indicated in control signal 1054, and transmits the modulated signal by radio waves.

[0304] Then, for example, the radio device 2002 of the base station 2000 transmits data to the network (471) and receives data from the network (472). Subsequently, for example, the radio device 2002 of the base station 2000 transmits a modulated signal to the terminal 1050 via radio waves.

[0305] The wireless device 453 of terminal 1050 performs processing such as demodulation and error correction decoding on the modulated signal received by radio waves and acquires received data 1056. The display unit 157 displays information based on the received data 1056.

[0306] The frame configuration of the modulated signal transmitted by the transmitting device 2001 of the base station 2000 in this embodiment is the same as the frame configuration in Figure 16 described in Embodiment 4. That is, in Figure 16, the symbol 600-1 related to the SSID is a symbol for transmitting the SSID information 1001-1 in Figure 25, and the symbol 1101 related to the encryption key is a symbol for transmitting the encryption key information 1001-2 in Figure 25. The data symbol 1102 is a symbol for transmitting the data 1002 in Figure 25.

[0307] As shown in Figure 16, the transmitter 2001 of the base station 2000 transmits the preamble 201, the control information symbol 202, the SSID symbol 600-1, the encryption key symbol 1101, and the data symbol 1102. The transmitter 2001 of the base station 2000 may also transmit frames containing symbols other than those shown in Figure 16. Furthermore, the frame configuration, including the order in which symbols are transmitted, is not limited to the configuration shown in Figure 16.

[0308] The frame configuration of the modulated signal transmitted by the wireless device 453 equipped in terminal 1050 in this embodiment is the same as the frame configuration in Figure 17 described in Embodiment 4. That is, as shown in Figure 17, the wireless device 453 equipped in terminal 1050 in Figure 25 transmits, for example, a preamble 1201, and then transmits a control information symbol 1202 and an information symbol 1203.

[0309] In this case, the preamble 1201 is a symbol used by the radio equipment 2002 of the base station 2000, which receives the modulated signal transmitted by the radio equipment 453, for purposes such as signal detection, time synchronization, frame synchronization, frequency synchronization, and frequency offset estimation.

[0310] The control information symbol 1202 is a symbol that contains data such as the error correction coding method used by terminal 1050 to generate the modulated signal, information about the modulation scheme, information about the frame configuration, and information about the transmission method. The radio equipment 2002 of base station 2000 performs demodulation of the modulated signal and other operations based on the information contained in the control information symbol 1202.

[0311] Information symbol 1203 is a symbol used by the wireless device 453 of terminal 1050 to transmit data.

[0312] Furthermore, the wireless device 453 of terminal 1050 may transmit frames containing symbols other than those shown in Figure 17. For example, the wireless device 453 may transmit a frame that includes a pilot symbol (reference symbol) in the middle of an information symbol 1203. Also, the frame configuration, including the order in which symbols are transmitted, is not limited to the configuration in Figure 17. In addition, multiple symbols may exist in the frequency axis direction in Figure 17. That is, symbols may exist on multiple frequencies (multiple carriers) in Figure 17.

[0313] The frame configuration of the modulated signal transmitted by the wireless device 2002 in this embodiment is the same as the frame configuration shown in Figure 12 described in Embodiment 3. That is, as shown in Figure 12, the wireless device 2002 transmits, for example, a preamble 701, and then transmits a control information symbol 702 and an information symbol 703.

[0314] The preamble 701 is a symbol used by the radio device 453 of terminal 1050, which receives the modulated signal transmitted by the radio device 2002, to perform tasks such as signal detection, time synchronization, frame synchronization, frequency synchronization, and frequency offset estimation.

[0315] The control information symbol 702 is a symbol that contains data such as the error correction coding method used to generate the modulated signal, information about the modulation scheme, information about the frame configuration, and information about the transmission method. The radio device 453 of terminal 1050 performs demodulation of the modulated signal and other operations based on the information in the control information symbol 702.

[0316] Information symbol 703 is a symbol used by the wireless device 2002 to transmit data.

[0317] Furthermore, the radio device 2002 of the base station 2000 shown in Figure 25 may transmit frames containing symbols other than those described in Figure 12. For example, the radio device 2002 may transmit frames that include a pilot symbol (reference symbol) in the middle of an information symbol 703. Also, the frame configuration, including the order in which symbols are transmitted, is not limited to the configuration in Figure 12. In addition, multiple symbols may exist in the frequency axis direction in Figure 12. That is, symbols may exist on multiple frequencies (multiple carriers) in Figure 12.

[0318] Furthermore, for example, the modulated signal in the frame configuration shown in Figure 16 transmitted by the transmitting device 2001 can be transmitted repeatedly at regular intervals. This allows multiple terminals 1050 to perform the operations described above.

[0319] Figure 26 is a flowchart illustrating an example of the processing performed by the "transmitter 2001 of base station 2000," "terminal 1050," and "wireless device 2002 of base station 2000" shown in Figure 25.

[0320] First, the transmitter 2001 transmits a modulated signal with the frame configuration shown in Figure 16 (ST1301).

[0321] Then, terminal 1050 receives the modulated signal transmitted by the transmitting device 2001 and obtains the SSID of the base station 2000 (wireless device 2002) that terminal 1050 is accessing (ST1302).

[0322] In addition, terminal 1050 acquires an encryption key to be used for communication with base station 2000 (wireless device 2002) that terminal 1050 accesses (ST1303).

[0323] Then, terminal 1050 establishes a radio connection with the base station 2000's radio device 2002 (ST1304). When terminal 1050 receives a response from the base station 2000's radio device 2002, the connection between terminal 1050 and the base station 2000's radio device 2002 is completed (ST1305).

[0324] Then, terminal 1050 transmits connection destination information to the wireless device 2002 of base station 2000 using radio waves (ST1306).

[0325] The radio equipment 2002 of base station 2000 obtains information from the network to be transmitted to terminal 1050 (ST1307).

[0326] Then, the radio device 2002 of the base station 2000 transmits the acquired information to the terminal 1050 using radio waves, and the terminal 1050 receives the information (ST1308). The terminal 1050, for example, obtains necessary information from the network via the radio device 2002 of the base station 2000 when needed.

[0327] As described above, based on the SSID information and encryption key information transmitted from the base station 2000's transmitter 2001, terminal 1050 connects to the base station 2000's wireless device 2002 and acquires the information, thereby securely obtaining information via the base station 2000, which is guaranteed to be secure. This is because when terminal 1050 obtains information from a visible light modulation signal, it is easier for the user to determine whether the information source is secure because it is visible light. In contrast, for example, if the SSID is obtained from the modulation signal of radio waves transmitted by a wireless LAN, it is difficult for the user to identify the device that transmitted the radio waves. For this reason, in terms of ensuring the security of information, visible light communication is more suitable for obtaining SSIDs compared to wireless LAN communication.

[0328] In this embodiment, the case in which the transmitting device 2001 transmits encryption key information has been described. However, for example, if the wireless device 2002 of the base station 2000 does not perform encrypted communication using an encryption key, the transmitting device 2001 may not transmit encryption key information and may only transmit information related to the SSID. In this case, the same implementation can be carried out by simply removing the configuration related to the encryption key from the configuration of the transmitting device 2001.

[0329] Furthermore, as shown in Figure 25, the SSID and encryption key of the base station 2000's wireless device 2002 may be configured to be rewritable. For example, in Figure 25, the wireless device 2002 receives SSID information 1001-1 and encryption key information 1001-2. The base station 2000's wireless device 2002 rewrites the SSID and encryption key using the input SSID information 1001-1 and encryption key information 1001-2. This further ensures the security of communication between the terminal 1050 and the base station 2000's wireless device 2002. Note that in Figure 25, the base station 2000's wireless device 2002 has the function to rewrite the SSID and encryption key, but it may also be configured so that it does not have the function to rewrite either or both of the SSID and encryption key.

[0330] Furthermore, the configuration of the transmitting device is not limited to the configuration of transmitting device 2001 shown in Figure 25, the configuration of the terminal is not limited to the configuration of terminal 1050 shown in Figure 25, and the connection destination and configuration of the wireless device are not limited to the connection destination and configuration of wireless device 2002 shown in Figure 25.

[0331] Furthermore, although Figure 25 describes the case where one base station 2000 is deployed, there may be multiple (secure) base station (or AP) 2000 radio devices 2002 accessible to terminal 1050. These multiple base station 2000 radio devices 2002 and terminal 1050 will transmit and receive modulated signals using radio waves. In this case, the SSID symbol transmitted by the transmitter 2001 in Figure 25 may include the SSID information of each of these multiple base station 2000 radio devices 2002. Also, the encryption key symbol transmitted by the transmitter 2001 in Figure 25 may include the encryption key information used to connect with each of these multiple base station 2000 radio devices 2002. Then, terminal 1050 in Figure 25 may select a base station 2000's radio device 2002 to connect to wirelessly (for example, by radio waves) based on the SSID information and encryption key information of the radio devices 2002 of multiple base stations 2000 (or it may connect to the radio devices of multiple base stations).

[0332] For example, suppose there are three base stations 2000, each equipped with a wireless device 2002. Here, the wireless devices 2002 of the three base stations 2000 are referred to as wireless device #A, wireless device #B, and wireless device #C, respectively. The SSID of wireless device #A is "abcdef", the SSID of wireless device #B is "ghijk", and the SSID of wireless device #C is "pqrstu". The encryption key for connecting to wireless device #A is "123", the wireless device for connecting to wireless device #B is "456", and the encryption key for connecting to wireless device #C is "789".

[0333] In this case, the symbol 600-1 related to the SSID in the frame configuration of Figure 16 of the modulated signal transmitted by the transmitter 2001 contains the information that "the SSID of wireless device #A is "abcdef"", "the SSID of wireless device #B is "ghijk"", and "the SSID of wireless device #C is "pqrstu". In addition, the symbol 1101 related to the encryption key in the frame configuration of Figure 16 contains the information that "the encryption key for connecting with wireless device #A is "123", "the encryption key for connecting with wireless device #B is "456", and "the encryption key for connecting with wireless device #C is "789".

[0334] Then, terminal 1050 in Figure 25 receives symbol 600-1 related to SSIDs and obtains the information that "the SSID of wireless device #A is "abcdef"", "the SSID of wireless device #B is "ghijk"", and "the SSID of wireless device #C is "pqrstu". Terminal 1050 also receives symbol 1101 related to encryption keys and obtains the information that "the encryption key for connecting to wireless device #A is "123"", "the encryption key for connecting to wireless device #B is "456"", and "the encryption key for connecting to wireless device #C is "789". Based on this information, terminal 1050 selects a base station to connect to wirelessly (for example, by radio waves) and establishes a connection.

[0335] Furthermore, as in this embodiment, by using a light source such as an LED to configure the wireless device 2002 of the base station 2000 that the terminal 1050 accesses, a special setting mode for the wireless connection procedure between the terminal 1050 and the base station 2000 is not required in the modulation signal for wireless communication transmitted by the terminal 1050. Similarly, a special setting mode for the wireless connection procedure between the terminal 1050 and the base station 2000 is not required in the modulation signal transmitted by the base station 2000. Therefore, in this embodiment, the data transmission efficiency of wireless communication can be improved.

[0336] Furthermore, as mentioned above, the encryption key may be an encryption key for the wireless LAN's SSID, or it may be an encryption key used to restrict connection type, service type, network coverage area, etc. In other words, an encryption key should be introduced for some purpose of restriction.

[0337] (Embodiment 7) Figure 27 shows an example of the configuration of the communication system in this embodiment.

[0338] The communication system in Figure 27 includes equipment 1000, terminal 1050, and base stations (or APs) 470-1 (base station #1), 470-2 (base station #2), and 470-3 (base station #3) that communicate with terminal 1050. In Figure 27, components that operate in the same way as in Figures 6, 9, and 15 are given the same numbers.

[0339] Device 1000 includes, for example, a visible light, illumination, light source, or light (light source 104), such as an LED. Hereafter, device 1000 will be referred to as the "fifth device" in this embodiment. Furthermore, the communication between the wireless device 453 and base station 470-1 (base station #1), the communication between the wireless device 453 and base station 470-2 (base station #2), and the communication between the wireless device 453 and base station 470-3 (base station #3) in Figure 27 will use, for example, radio waves.

[0340] In the fifth device 1000 of Figure 27, the transmitting unit 102 receives SSID information 1001-1, encryption key information 1001-2, and data 1002 as inputs, generates a (optical) modulated signal 103 based on these input signals, and outputs the modulated signal 103. The modulated signal 103 is then transmitted, for example, from a light source 104.

[0341] Next, we will describe the information regarding the SSID (1001-1) and the information regarding the encryption key (1001-2).

[0342] First, we will explain information regarding the SSID, item 1001-1.

[0343] The SSID information 1001-1 includes, for example, information indicating the SSID of base station 470-1 (base station #1) in Figure 27, information indicating the SSID of base station 470-2 (base station #2), and information indicating the SSID of base station 470-3 (base station #3). For example, base stations 470-1, 470-2, and 470-3 transmit and receive modulated signals via radio waves. In other words, the fifth device 1000 can provide terminal 1050 with secure access to base stations 470-1, 470-2, and 470-3. This allows terminal 1050 in Figure 27 to securely obtain information from base stations 470-1, 470-2, and 470-3.

[0344] On the other hand, the fifth device 1000 can restrict the terminals accessing base stations 470-1, 470-2, and 470-3 to terminals located in a space where they can receive the optical signals transmitted (irradiated) by the fifth device 1000.

[0345] Furthermore, terminal 1050 may determine that the notified SSID is the SSID of a secure base station when it receives an optical signal transmitted in a predetermined manner. Terminal 1050 may also perform a separate process to determine whether the notified SSID is secure or not. For example, the fifth device 1000 may transmit a predetermined identifier in the optical signal, and terminal 1050 may determine whether the notified SSID is the SSID of a secure base station based on the received identifier.

[0346] Note that while Figure 27 shows base stations 470-1, 470-2, and 470-3, other base stations (or access points) may exist besides base stations 470-1, 470-2, and 470-3.

[0347] Next, we will explain information regarding the encryption key, 1001-2.

[0348] The encryption key information 1001-2 is information about the encryption key necessary for terminal 1050 to communicate with base stations 470-1, 470-2, and 470-3. By obtaining the encryption key information 1001-2 from the fifth device 1000, terminal 1050 can perform encrypted communication "between terminal 1050 and base station 470-1", "between terminal 1050 and base station 470-2", and "between terminal 1050 and base station 470-3".

[0349] The above describes the information regarding the SSID (1001-1) and the information regarding the encryption key (1001-2).

[0350] Terminal 1050 in Figure 27 receives the modulated signal transmitted by the fifth device 1000. Note that in terminal 1050 in Figure 27, components that operate similarly to terminal 150 in Figure 6 and terminal 450 in Figure 9 are given the same numbers.

[0351] The light-receiving unit 151 of the terminal 1050 is, for example, an image sensor such as a CMOS or organic CMOS. The light-receiving unit 151 receives light containing a modulated signal transmitted from the fifth device 1000 and outputs a received signal 152.

[0352] The receiving unit 153 then takes the received signal 152 received by the light receiving unit 151 as input, performs demodulation, error correction, and decoding on the modulated signal contained in the received signal 152, and outputs the received data 154.

[0353] The data analysis unit 155 takes the received data 154 as input and outputs, for example, information 1051 of the SSIDs of the base stations 470-1, 470-2, and 470-3 to be connected to, and information 1052 of the encryption key for communicating with the base stations 470-1, 470-2, and 470-3 to be connected to. For example, in a wireless LAN (Local Area Network), encryption methods include WEP (Wired Equivalent Privacy), WPA (Wi-Fi Protected Access), and WPA2 (Wi-Fi Protected Access 2) (PSK (Pre-Shared Key) mode, EAP (Extended Authentication Protocol) mode). However, the encryption method is not limited to these.

[0354] The display unit 157 receives SSID information 1051 and encryption key information 1052 as input and displays, for example, the SSID of the communication partner accessed by the wireless device 453 equipped with terminal 1050, and the encryption key (this display is referred to as the "first display" in this embodiment).

[0355] For example, after the first display, the wireless device 453 takes the SSID information 1051 and the encryption key information 1052 as input and establishes a connection with one of the base stations 470-1, 470-2, or 470-3 (for example, the connection is made using radio waves). At this time, if the connected base station 470 is also communicating with the wireless device 453 equipped with terminal 1050, it transmits a modulated signal, for example, using radio waves.

[0356] Subsequently, the wireless device 453 receives data 1053 and control signal 1054 as input, modulates data 1053 according to the control indicated in control signal 1054, and transmits the modulated signal as a radio wave.

[0357] Then, for example, the connected base station 470 transmits data to the network (one of 471-1, 471-2, or 471-3) and receives data from the network (one of 472-1, 472-2, or 472-3). Subsequently, for example, the connected base station 470 transmits a modulated signal to the terminal 1050 via radio waves.

[0358] The wireless device 453 of terminal 1050 performs processing such as demodulation and error correction decoding on the modulated signal received by radio waves and acquires received data 1056. The display unit 157 displays information based on the received data 1056.

[0359] In the case of Figure 27, there are three types of frame configurations for the modulated signal transmitted by the fifth device 1000. Figure 28 shows frame 2300-1 (frame #1), which is one of the three types of frame configurations; Figure 29 shows frame 2300-2 (frame configuration #2), which is one of the three types of frame configurations; and Figure 30 shows frame 2300-3 (frame configuration #3), which is one of the three types of frame configurations.

[0360] Figure 28 shows an example of the configuration of frame 2300-1 (frame #1) of the modulated signal transmitted by the fifth device 1000. In Figure 28, the horizontal axis represents time. Also, in Figure 28, symbols similar to those in Figures 2 and 16 are given the same numbers and their explanations are omitted. Frame 2300-1 (frame #1) in Figure 28 is a frame for transmitting the SSID information of base station 470-1 (base station #1) in Figure 27 and the encryption key information of base station 470-1 (base station #1) (the encryption key for accessing base station 470-1).

[0361] Symbol 2301-1, which relates to the SSID, is a symbol used to transmit the SSID information 1001-1 shown in Figure 27. Furthermore, symbol 2301-1, which relates to the SSID, is a symbol used by the fifth device 1000 in Figure 27 to transmit the SSID of base station 470-1 (base station #1).

[0362] Symbol 2302-1, which relates to the encryption key, is a symbol used to transmit the encryption key information 1001-2 shown in Figure 27. Furthermore, symbol 2302-1 is a symbol used by the fifth device 1000 in Figure 27 to transmit the encryption key for base station 470-1 (base station #1) (the encryption key for accessing base station 470-1).

[0363] The fifth device 1000 transmits the preamble 201, the control information symbol 202, the SSID symbol 2301-1, the encryption key symbol 2302-1, and the data symbol 1102. The fifth device 1000 may also transmit frame 2300-1 (frame #1) which includes symbols other than those shown in Figure 28. Furthermore, the configuration of frame 2300-1 (frame #1), including the order in which the symbols are transmitted, is not limited to the configuration shown in Figure 28.

[0364] Figure 29 shows an example of the configuration of frame 2300-2 (frame #2) of the modulated signal transmitted by the fifth device 1000. In Figure 29, the horizontal axis represents time. Also, in Figure 29, symbols similar to those in Figures 2 and 16 are given the same numbers and their explanations are omitted. Frame 2300-2 (frame #2) in Figure 29 is a frame for transmitting the SSID information of base station 470-2 (base station #2) in Figure 27 and the encryption key information of base station 470-2 (base station #2) (the encryption key for accessing base station 470-2).

[0365] Symbol 2301-2, which relates to the SSID, is a symbol used to transmit the SSID information 1001-1 shown in Figure 27. Furthermore, symbol 2301-2, which relates to the SSID, is a symbol used by the fifth device 1000 in Figure 27 to transmit the SSID of base station 470-2 (base station #2).

[0366] Symbol 2302-2, which relates to the encryption key, is a symbol used to transmit the encryption key information 1001-2 shown in Figure 27. Furthermore, symbol 2302-2 is a symbol used by the fifth device 1000 in Figure 27 to transmit the encryption key for base station 470-2 (base station #2) (the encryption key for accessing base station 470-2).

[0367] The fifth device 1000 transmits the preamble 201, control information symbol 202, SSID-related symbols 2301-2, encryption key-related symbols 2302-2, and data symbol 1102. The fifth device 1000 may also transmit frame 2300-2 (frame #2), which may include symbols other than those shown in Figure 29. Furthermore, the configuration of frame 2300-2 (frame #2), including the order in which symbols are transmitted, is not limited to the configuration shown in Figure 29.

[0368] Figure 30 shows an example of the configuration of frame 2300-3 (frame #3) of the modulated signal transmitted by the fifth device 1000. In Figure 30, the horizontal axis represents time. Also, in Figure 30, symbols similar to those in Figures 2 and 16 are given the same numbers and their explanations are omitted. Frame 2300-3 (frame #3) in Figure 30 is a frame for transmitting the SSID information of base station 470-3 (base station #3) in Figure 27 and the encryption key information of base station 470-3 (base station #3) (the encryption key for accessing base station 470-3).

[0369] Symbol 2301-3, which relates to the SSID, is a symbol used to transmit the SSID information 1001-1 shown in Figure 27. Furthermore, symbol 2301-3, which relates to the SSID, is a symbol used by the fifth device 1000 in Figure 27 to transmit the SSID of base station 470-3 (base station #3).

[0370] Symbol 2302-3, which relates to the encryption key, is a symbol used to transmit the encryption key information 1001-2 shown in Figure 27. Furthermore, symbol 2302-3, which relates to the encryption key, is a symbol used by the fifth device 1000 to transmit the encryption key for base station 470-3 (base station #3) (the encryption key for accessing base station 470-3).

[0371] The fifth device 1000 transmits the preamble 201, control information symbol 202, SSID-related symbols 2301-3, encryption key-related symbols 2302-3, and data symbol 1102. The fifth device 1000 may also transmit frame 2300-3 (frame #3) containing symbols other than those shown in Figure 30. Furthermore, the configuration of frame 2300-3 (frame #3), including the order in which symbols are transmitted, is not limited to the configuration shown in Figure 30.

[0372] Figure 31 shows an example of the transmission method when the fifth device 1000 transmits "frame 2300-1 (frame #1) in Figure 28", "frame 2300-2 (frame #2) in Figure 29", and "frame 2300-3 (frame #3) in Figure 30". In Figure 31, the horizontal axis represents time.

[0373] In Figure 31, in "frame #1 group transmission" 2601-1 and 2601-2, one or more frames 2300-1 (frame #1) from Figure 28 are transmitted. Also, in "frame #2 group transmission" 2602-1 and 2602-2, one or more frames 2300-2 (frame #2) from Figure 29 are transmitted. Furthermore, in "frame #3 group transmission" 2603-1 and 2603-2, one or more frames 2300-3 (frame #3) from Figure 30 are transmitted.

[0374] A detailed explanation of this will be given below.

[0375] First, let's explain that in "frame #1 group transmission" 2601-1 and 2601-2, one or more frames 2300-1 (frame #1) shown in Figure 28 are transmitted.

[0376] For example, if the light-receiving unit 151 uses an image sensor such as a CMOS or organic CMOS, it may process the received signal on a frame-by-frame basis in the video or still image. For example, if "4K 30p" is written in the video, it means that the number of pixels per frame is 3840 x 2160 and the number of frames per second is 30.

[0377] Therefore, if the fifth device 1000 transmits a modulated signal configured such that "frame 2300-1 (frame #1) in Figure 28", "frame 2300-2 (frame #2) in Figure 29", and "frame 2300-3 (frame #3) in Figure 30" exist within one frame, it becomes difficult for the terminal 1050 in Figure 27 to select which base station 470 to access from among the multiple base stations 470-1, 470-2, and 470-3.

[0378] Therefore, in this embodiment, we propose a frame configuration as shown in Figure 31.

[0379] <Method 1-1> As method 1-1, each of the "frame #1 group transmissions" 2601-1 and 2601-2 includes multiple frames 2300-1 (frame #1) from Figure 28, so that the time interval occupied by each of the "frame #1 group transmissions" 2601-1 and 2601-2 is longer than the time of a frame in a video or still image.

[0380] This prevents terminal 1050 from receiving modulated signals containing different SSIDs and encryption keys within a single frame of video or still image from the fifth device 1000, such as "frame 2300-1 (frame #1) in Figure 28," "frame 2300-2 (frame #2) in Figure 29," and "frame 2300-3 (frame #3) in Figure 30." Therefore, terminal 1050 in Figure 27 can easily select the base station 470 to access from among multiple base stations 470-1, 470-2, and 470-3.

[0381] <Method 2-1> As method 2-1, the time interval occupied by frame 2300-1 (frame #1) in Figure 28 is made longer than the time of a frame in a video or still image.

[0382] For example, the symbol 2301-1 related to the SSID in Figure 28 may contain multiple instances of "SSID information for base station #1" (i.e., the "SSID information for base station #1" is repeatedly included), and the symbol 2302-1 related to the encryption key may contain multiple instances of "encryption key information for base station #1 (encryption key information for connecting to base station #1)" (i.e., the "encryption key information for base station #1 (encryption key information for connecting to base station #1)" is repeatedly included).

[0383] This prevents terminal 1050 from receiving modulated signals containing different SSIDs and encryption keys within a single frame of video or still image from the fifth device 1000, such as "frame #1 of 2300-1 in Figure 28," "frame #2 of 2300-2 in Figure 29," and "frame #3 of 2300-3 in Figure 30." Therefore, terminal 1050 can easily select the base station 470 to access from among the multiple base stations 470-1, 470-2, and 470-3.

[0384] Similarly, the "frame #2 group transmission" 2602-1 and 2602-2 should ideally have the following configuration.

[0385] <Methods 1-2> As a second method, each of the "frame #2 group transmissions" 2602-1 and 2602-2 includes multiple frames 2300-2 (frame #2) from Figure 29, so that the time interval occupied by the "frame #2 group transmission" is longer than the time of a frame in a video or still image.

[0386] <Method 2-2> As a second method, the time interval occupied by frame 2300-2 (frame #2) in Figure 29 is made longer than the time of a frame in a video or still image.

[0387] For example, the symbol 2301-2 for SSID in Figure 29 may contain multiple instances of "SSID information for base station #2" (i.e., the "SSID information for base station #2" is repeatedly included), and the symbol 2302-2 for encryption key may contain multiple instances of "encryption key information for base station #2 (encryption key information for connecting to base station #2)" (i.e., the "encryption key information for base station #2 (encryption key information for connecting to base station #2)" is repeatedly included).

[0388] Similarly, the "frame #3 group transmission" 2603-1 and 2603-2 should have the following configuration.

[0389] <Methods 1-3> As a third method, multiple frames 2300-3 (frame #3) from Figure 30 are included in each of the "frame #3 group transmissions" 2603-1 and 2603-2, so that the time interval occupied by the "frame #3 group transmission" is longer than the time of a frame in a video or still image.

[0390] <Methods 2-3> As a second or third method, the time interval occupied by frame 2300-3 (frame #3) in Figure 30 is made longer than the time of a frame in a video or still image.

[0391] For example, the symbols 2301-3 related to the SSID in Figure 30 may contain multiple instances of "SSID information for base station #3" (i.e., the "SSID information for base station #3" is repeatedly included), and the symbols 2302-3 related to the encryption key may contain multiple instances of "encryption key information for base station #3 (encryption key information for connecting to base station #3)" (i.e., the "encryption key information for base station #3 (encryption key information for connecting to base station #3)" is repeatedly included).

[0392] Next, we will explain the effect when the fifth device 1000 transmits a frame, as shown in Figures 28 to 31.

[0393] As an example, let's consider the 2700 area in Figure 32. In Figure 32, the fifth device 1000 is placed at the locations marked "○" 2701-1, 2701-2, 2701-3, 2701-4, 2701-5, 2701-6, 2701-7, 2701-8, 2701-8, 2701-9, and 2701-10. Also, base station 470-1 (base station #1) is placed at the location marked "◎" 2702-1, base station 470-2 (base station #2) is placed at the location marked "◎" 2702-2, and base station 470-3 (base station #3) is placed at the location marked "◎" 2702-3.

[0394] For example, let's assume that within area 2703 there are 99 terminals (hereinafter simply referred to as terminal 1050) that have the same configuration as terminal 1050.

[0395] At this time, for example, the fifth device 1000 located at positions "○" 2701-5 and 2701-10 both transmit the SSID information of base station 470-3 (base station #3) and the encryption key information for accessing base station 470-3 (base station #3). This is because base station 470-3 (base station #3) is the closest base station to positions "○" 2701-5 and 2701-10.

[0396] In this case, all 99 terminals 1050 would access base station 470-3 (base station #3). This would increase the likelihood that some terminals 1050 would have difficulty accessing base station 470-3 (base station #3) due to the high volume of traffic.

[0397] Considering this point, by controlling the 99 terminals 1050 to access base stations 470-1 (base station #1) (location of "◎" 2702-1), 470-2 (base station #2) (location of [◎] 2702-2), and 470-3 (base station #3) (location of [◎] 2702-3) as evenly as possible, the existence of terminals 1050 that have difficulty accessing base station 470, as described above, can be reduced.

[0398] For example, since the timing at which the 99 terminals 1050 access the fifth device 1000 will generally differ, if the fifth device 1000 transmits frames as shown in Figures 28 to 31, as in this embodiment, each of the 99 terminals 1050 will obtain the SSID and encryption key of one of the base stations 470-1, 470-2, or 470-3, depending on the timing at which they access the fifth device 1000. This ensures that the 99 terminals 1050 access the base stations 470-1, 470-2, and 470-3 as evenly as possible. Therefore, the existence of terminals 1050 that have difficulty accessing the base station 470, as described above, can be reduced.

[0399] Figure 31 shows an example of the transmission method used by the fifth device 1000 when transmitting "frame 2300-1 (frame #1) in Figure 28," "frame 2300-2 (frame #2) in Figure 29," and "frame 2300-3 (frame #3) in Figure 30." However, the transmission method used by the fifth device 100 when transmitting "frame 2300-1 (frame #1) in Figure 28," "frame 2300-2 (frame #2) in Figure 29," and "frame 2300-3 (frame #3) in Figure 30" is not limited to this.

[0400] For example, Figure 31 shows a configuration in which the fifth device 1000 repeatedly transmits "frame #1 group transmission," "frame #2 group transmission," and "frame #3 group transmission" in that order. However, "frame #1 group transmission," "frame #2 group transmission," and "frame #3 group transmission" do not need to be transmitted in the order shown in Figure 31. Alternatively, for example, the fifth device 1000 may transmit "frame group 1 transmission," "frame group #2 transmission," and "frame group #3 transmission" in a time-random order, or it may transmit "frame group 1 transmission," "frame group #2 transmission," and "frame group #3 transmission" in a regular order different from that shown in Figure 31. At a minimum, it is sufficient that the fifth device 1000 transmits "frame group 1 transmission," "frame group #2 transmission," and "frame group #3 transmission."

[0401] Furthermore, in Figure 31, the fifth device 1000 transmits "frame #1 group transmission," "frame #2 group transmission," and "frame #3 group transmission" in succession, but it is not necessary to transmit them consecutively. For example, in Figure 31, there may be a time interval between frame #1 group transmission 2601-1 and frame #2 group transmission 2602-2.

[0402] Furthermore, although Figure 31 consists only of "frame #1 transmission," "frame #2 transmission," and "frame #3 transmission," other symbols and other frames may also exist. In addition, although Figures 31 and 27 show three base stations 470, the number of base stations 470 is not limited to this, and it is possible to operate in the same way as when there are two or more base stations 470. Therefore, for example, if there are N base stations 470 (where N is an integer of 2 or more), and the fifth device 1000 performs a transmission as shown in Figure 31, then "frame #k transmission" will exist. Here, k is an integer between 1 and N. Then, "frame #k transmission" will contain symbols related to the SSID (information about the SSID of base station #k) and symbols related to the encryption key (information about the encryption key for accessing base station #k).

[0403] The frame configuration of the modulated signal transmitted by the wireless device 453 equipped with terminal 1050 in Figure 27 is the same as the frame configuration in Figure 17 described in Embodiment 4. That is, as shown in Figure 17, the wireless device 453 equipped with terminal 1050 in Figure 27 transmits, for example, a preamble 1201, and then transmits a control information symbol 1202 and an information symbol 1203.

[0404] Preamble 1201 is a symbol used by base stations 470-1, 470-2, and 470-3, which receive the modulated signal transmitted by the radio device 453 of terminal 1050, for purposes such as signal detection, time synchronization, frame synchronization, frequency synchronization, and frequency offset estimation.

[0405] The control information symbol 1202 is a symbol that contains data such as the error correction coding method used to generate the modulated signal, information about the modulation scheme, information about the frame configuration, and information about the transmission method. Base stations 470-1, 470-2, and 470-3 perform demodulation of the modulated signal and other operations based on the information contained in the control information symbol 1202.

[0406] Information symbol 1203 is a symbol used by the wireless device 453 of terminal 1050 to transmit data.

[0407] Furthermore, the wireless device 453 of terminal 1050 in Figure 27 may transmit frames containing symbols other than those shown in Figure 17 (for example, a frame containing a pilot symbol (reference symbol) in the middle of an information symbol 1203). Also, the frame configuration, including the order in which symbols are transmitted, is not limited to the configuration in Figure 17. Moreover, in Figure 17, multiple symbols may exist in the frequency axis direction, that is, symbols may exist on multiple frequencies (multiple carriers).

[0408] The frame configuration of the modulated signals transmitted by base stations 470-1, 470-2, and 470-3 in Figure 27 is the same as the frame configuration in Figure 12 described in Embodiment 3. That is, as shown in Figure 12, base stations 470-1, 470-2, and 470-3 transmit, for example, a preamble 701, and then control information symbols 702 and information symbols 703.

[0409] Preamble 701 is a symbol used by the radio equipment 453 of terminal 1050, which receives modulated signals transmitted by base stations 470-1, 470-2, and 470-3, to perform tasks such as signal detection, time synchronization, frame synchronization, frequency synchronization, and frequency offset estimation.

[0410] The control information symbol 702 is a symbol that contains data such as the error correction coding method used to generate the modulated signal, information about the modulation scheme, information about the frame configuration, and information about the transmission method. The radio device 453 of terminal 1050 performs demodulation of the modulated signal and other operations based on the information in the control information symbol 702.

[0411] Information symbol 703 is a symbol used by base stations 470-1, 470-2, and 470-3 to transmit data.

[0412] Furthermore, base stations 470-1, 470-2, and 470-3 may transmit frames containing symbols other than those shown in Figure 12. For example, base stations 470-1, 470-2, and 470-3 may transmit frames that include a pilot symbol (reference symbol) in the middle of an information symbol 703. Also, the frame configuration, including the order in which symbols are transmitted, is not limited to the configuration shown in Figure 12. Moreover, in Figure 12, multiple symbols may exist along the frequency axis. In other words, in Figure 12, symbols may exist on multiple frequencies (multiple carriers).

[0413] Figure 33 is a flowchart illustrating an example of the processing performed by "Fifth Device 1000," "Terminal 1050," and "Base Station #X." Note that X can be 1, 2, or 3.

[0414] First, the fifth device 1000 transmits a modulated signal with the frame configuration shown in Figure 31 (ST2801).

[0415] Then, terminal 1050 receives the modulated signal transmitted by the fifth device 1000 and selects the base station to access from base stations 470-1 (base station #1), 470-2 (base station #2), and 470-3 (base station #3) in Figure 27 (ST2802).

[0416] The following explains this point. Terminal 1050 receives a modulated signal transmitted by the fifth device 1000 in order to access one of the base stations 470. At this time, terminal 1050 will obtain one of the "frame #1 transmission group", "frame #2 transmission group", or "frame #3 transmission group" in Figure 31, for example, in one frame of a video or still image. Then, terminal 1050 determines from the obtained base station information (e.g., SSID) that the base station 470 to access is one of base station 470-1 (base station #1), base station 470-2 (base station #2), or base station 470-3 (base station #3).

[0417] Next, terminal 1050 receives the modulated signal transmitted by the fifth device 1000 and obtains the SSID of base station #X that terminal 1050 is accessing (ST2803).

[0418] In addition, terminal 1050 obtains the encryption key used for communication with base station #X that terminal 1050 accesses (ST2804).

[0419] Then, terminal 1050 establishes a radio connection with base station #X (ST2805). When terminal 1050 receives a response from base station #X, the connection between terminal 1050 and base station #X is completed (ST2806).

[0420] Then, terminal 1050 transmits information about the connection destination to base station #X using radio waves (ST2807).

[0421] Base station #X obtains information from the network to send to terminal 1050 (ST2808).

[0422] Then, base station #X transmits the acquired information to terminal 1050 using radio waves, and terminal 1050 receives the information (ST2809). Terminal 1050, for example, can obtain necessary information from the network via base station #X when needed.

[0423] As described above, based on the SSID information and encryption key information transmitted from the fifth device 1000, terminal 1050 connects to base station 470 and acquires the information, thereby securely obtaining the information via the base station 470, which is guaranteed to be secure. This is because when information is obtained from a modulated signal of visible light, it is easier for the user to determine whether the information source is secure because it is visible light. In contrast, for example, if the SSID is obtained from the modulated signal of radio waves transmitted by a wireless LAN, it is difficult for the user to identify the device that transmitted the radio waves. For this reason, in terms of ensuring the security of information, visible light communication is more suitable for obtaining the SSID compared to wireless LAN communication.

[0424] In this embodiment, the case in which the fifth device 1000 transmits encryption key information has been described. However, for example, if the base station 470 is not performing encrypted communication using an encryption key, the fifth device 1000 may not transmit encryption key information and may only transmit information related to the SSID. In this case, the same configuration can be implemented by simply removing the encryption key-related configuration from the above-described configuration.

[0425] Furthermore, the configuration of the fifth device is not limited to the configuration of the fifth device 1000 shown in Figure 27, the configuration of the terminal is not limited to the configuration of terminal 1050 shown in Figure 27, and the connection destinations and configurations of base stations #1, #2, and #3 are not limited to the connection destinations and configurations of base stations 470-1, 470-2, and 470-3 shown in Figure 27.

[0426] Furthermore, according to this embodiment, even if there are multiple terminals 1050 in a certain area, the number of terminals 1050 that have difficulty accessing the base station 470 can be reduced.

[0427] In Figure 32, the frame configurations of the modulated signals transmitted by the fifth device 1000 positioned at positions marked "○" 2701-1, 2701-2, 2701-3, 2701-4, 2701-5, 2701-6, 2701-7, 2701-8, 2701-8, 2701-9, and 2701-10 may all be the same as the configuration in Figure 31, the modulated signals transmitted by the fifth device 1000 may each have different frame configurations, and there may be multiple fifth devices 1000 that transmit modulated signals with the same frame configuration.

[0428] (Embodiment 8) In this embodiment, as one example of the application of the optical signal-based communication method described above, a case in which the optical signal-based communication method is used in combination with image processing will be explained. The communication system according to this embodiment can also be applied, for example, to communication between automobiles (vehicle-to-vehicle communication) or to communication between a vehicle and communication equipment installed on or near a road (road-to-vehicle communication).

[0429] First, the basic configuration of this embodiment will be briefly described. However, this basic configuration is not limited to automobiles, but can also be applied to mobile devices such as smartphones and notebook PCs, and furthermore, to other electronic devices.

[0430] Figure 34 is a block diagram showing the configuration of communication device A1000, which is an example of a communication device in this embodiment. Communication device A1000 includes a light receiving device A1002, a control unit A1004, and a wireless device A1006.

[0431] The light receiving device A1002 receives an optical signal A1001 emitted from a transmitter (not shown) and / or captures still or moving images, and outputs light received data A1003. The control unit A1004 controls other devices provided by the communication device A1000 and processes the light received data A1003 input from the light receiving device A1002 and the wireless received data input from the wireless device A1006. The wireless device A1006 wirelessly connects with other communication devices A1100 based on a control signal A1005 from the control unit A1004 to perform wireless communication, transmitting wireless transmission data and receiving wireless reception data. The wireless transmission data and wireless reception data are transmitted and received between the wireless device A1006 and the control unit A1004 as wireless communication data A1008. The control unit A1004 outputs a control signal A1007 to control the operation of the light receiving device A1002, and the light receiving device A1002 controls its operation based on the control signal A1007.

[0432] If the light-receiving data A1003 generated by the light-receiving device A1002 includes still image data or video data, the control unit A1004 may perform image processing using the still image data or video data. Details of examples of image processing performed by the control unit A1004 will be described later.

[0433] Figure 35 is a block diagram showing the configuration of communication device A2000, which is another example of a communication device in this embodiment. In Figure 35, components that have the same functions as communication device A1000 shown in Figure 34 are denoted by the same reference numerals as in Figure 34, and their description is omitted. Communication device A2000 differs from communication device A1000 in that it includes a presentation unit A2003 and an input unit A2004.

[0434] The control unit A1004 generates an image based on the received light data A1003 and / or wireless received data, other input information, information read from memory, etc., and outputs the generated image as presentation information A2002 to the presentation unit A2003. Presentation information A2002 is information including, for example, image information and character information generated based on the received light data A1003 or other data, and the presentation unit A2003 is, for example, a liquid crystal display, plasma display, organic EL display, etc., which displays the image signal generated from the image information and character information obtained as presentation information A2002, but is not limited to these. For example, presentation information A2002 may be audio information, and the presentation unit A2003 may be a speaker that outputs audio according to the audio information. The input unit A2004 outputs input information A2005, such as information indicating the operation performed by the user and input character information, to the control unit A1004 according to the user's operation. The input unit A2004 is, for example, a touch panel, physical keys, floating touch display, motion sensor, etc., but is not limited to these. For example, input unit A2004 may be a microphone, and input information A2005 may be audio information.

[0435] Next, we will describe the detailed configuration of the light receiving device A1002.

[0436] Figure 36 is a block diagram showing the configuration of light receiving device A3000, which is a first example of the detailed configuration of light receiving device A1002 in this embodiment.

[0437] The light receiving device A3000 comprises a light receiving unit A3001 and a light receiving signal processing unit A3003. The light receiving unit A3001 has a configuration similar to, for example, the light receiving unit 151 in Figure 6, and receives light incident from the outside and outputs a received signal A3002. The light receiving signal processing unit A3003 performs predetermined processing on the received signal A3002 and sends out the resulting signal as light receiving data A1003.

[0438] In one example, the light-receiving signal processing unit A3003 performs predetermined processing on the received signal A3002. This processing includes demodulation and error correction decoding of the modulated signal component contained in the received signal A3002, and outputs the demodulated data A4002 as light-receiving data A1003. In another example, the light-receiving signal processing unit A3003 generates still image data or moving image data from the received signal A3002 acquired by the light-receiving unit A3001, which is an image sensor such as a CMOS or organic CMOS, and outputs the generated still image data or moving image data as light-receiving data A1003. Here, the still image data or moving image data may be encoded data using an image compression method or a moving image compression method, or it may be uncompressed data. The details of the configuration example of the light-receiving signal processing unit A3003 will be described below.

[0439] Figure 37 shows the configuration of a light-receiving signal processing unit A4000, which is an example of the configuration of the light-receiving signal processing unit A3003. The light-receiving signal processing unit A4000 has a receiving processing unit A4001. The receiving processing unit A4001 performs demodulation, error correction, and other processing on the received signal A3002 and outputs the resulting demodulated data A4002 as received data A1003. The received signal A3002 input to the light-receiving signal processing unit A4000 may be a signal acquired by an image sensor such as a CMOS sensor using a sampling method for receiving optical signals, such as the line scan sampling, application examples of line scan sampling, or frame sampling described above, or it may be a signal sampled at the sampling rate required for receiving optical signals using an element different from the image sensor that can convert optical signals into electrical signals, such as a photodiode.

[0440] Figure 38 shows the configuration of a light-receiving signal processing unit A5000, which is another example of the configuration of the light-receiving signal processing unit A3003. The light-receiving signal processing unit A5000 has an image data generation unit A5001, which outputs image data A5002 containing optical signal information as light-receiving data A1003. That is, the image data generation unit A5001 generates still image data or video data from the received signal A3002, and outputs the generated still image data or video data, image data A5002, as light-receiving data A1003.

[0441] In the following explanation, for the sake of simplicity, unless otherwise specified, we will describe an example where image data A5002 is video data. However, it goes without saying that the same procedures can be followed even if the video data in the following explanation is replaced with still image data, or a combination of video and still image data.

[0442] If the light receiving device A1002 includes a light receiving signal processing unit A5000, the light receiving unit A3001 is an image sensor such as a CMOS sensor. The light receiving device A1002 controls the operation of the light receiving unit A3001, for example, and acquires the received signal A3002 using a sampling method for receiving optical signals during the first period in Figure 39, and acquires the received signal A3002 using an imaging method for shooting video during the second period in Figure 39.

[0443] Hereafter, signals acquired using a sampling method for receiving optical signals will be referred to as optical communication imaging signals, and signals acquired using an imaging method for video recording will be referred to as video imaging signals. Furthermore, data generated by the image data generation unit A5001 from optical communication imaging signals will be referred to as optical communication imaging data, and data generated from video imaging signals will be referred to as video imaging data.

[0444] Figure 39 shows an example of an image sensor control method when acquiring both an imaging signal for optical communication and an imaging signal for video using a single image sensor in a time-division manner, as described above. In the first period shown in Figure 39, the light receiving device A1002 acquires an imaging signal for optical communication using a sampling method for receiving optical signals with the light receiving unit A3001, and in the second period, it acquires an imaging signal for video using an imaging method for video recording with the light receiving unit A3001.

[0445] Here, the first period and the second period are, for example, periods corresponding to one or more frames in a video. However, the light receiving device A1002 may switch between a sampling method for receiving optical signals and an imaging method for shooting video at a timing that is not synchronized with the frames in the video. The light receiving device A1002 may arrange the first period periodically or aperiodicly. Furthermore, the rules for arranging the first period, such as the period for arranging the first period, may be changed dynamically.

[0446] The light receiving device A1002 may determine the start time of the first period and / or the end time of the first period based on signals input from an external source. For example, the light receiving device A1002 controls the operation of the light receiving unit A3001 based on the control signal A1007 input from the control unit A1004. In this case, the control unit A1004 may output a control signal to control the operation of the light receiving unit A3001 based on signals received from external transmitting devices of the communication devices A1000 and A2000 using communication methods such as wireless communication, wired communication, or optical communication, or data acquired from sensors such as image sensors provided by the communication devices A1000 and A2000.

[0447] The control information for controlling the operation of the light-receiving unit A3001 may be, for example, a signal specifying a rule for arranging the first and second periods described above, or a signal instructing the light-receiving unit A3001, which normally acquires imaging signals for video using an imaging method for video recording, to acquire imaging signals for optical communication using a sampling method for receiving optical signals, either temporarily or continuously. Specific examples will be explained later.

[0448] In the above explanation, an example was described in which the first and second periods are arranged alternately, but the method of controlling the image sensor is not limited to this. For example, a third period may be included in which the CMOS sensor is operated using an imaging or sampling method different from either of the methods implemented in the first and second periods, or a transition period for switching the operation of the image sensor may be included between the first and second periods.

[0449] According to the image sensor control method, both imaging signals for optical communication and imaging signals for video can be acquired in time-division multiplexing using a single image sensor. As a result, the number of image sensors installed in the communication device can be reduced.

[0450] Alternatively, the light receiving device A1002 may operate the light receiving unit A3001 in a sampling method for receiving optical signals at all times to acquire the received signal A3002.

[0451] When generating video data A5002, the image data generation unit A5001 may apply encoding processing using a video compression method to the video signal, which consists of multiple frames generated from the received signal A3002.

[0452] For example, if the received signal A3002 includes both an imaging signal for optical communication and an imaging signal for video, the image data generation unit A5001 may perform video compression on the frames generated from the video imaging signal, excluding the images (or frames) generated from the imaging signal for optical communication. In this case, the light receiving device A1002 outputs the encoded video data and the image data generated from the imaging signal for optical communication as received data A1003.

[0453] In the above explanation, it was stated that the imaging signal for optical communication is output as image data from the light receiving device A1002. However, the imaging signal for optical communication may be output from the light receiving device A1002 in any data format as long as it is in a format that can demodulate the optical signal. For example, it may be data obtained by averaging or summing the brightness values ​​of the pixels included in each exposure line, or data obtained by sequentially arranging the brightness values ​​of the pixels included in each region obtained by dividing each exposure line into multiple regions.

[0454] Furthermore, the motion image encoding process that the image data generation unit A5001 may perform when the received signal A3002 includes both an imaging signal for optical communication and an imaging signal for motion video is not limited to the motion image encoding process described above. For example, the image data generation unit A5001 may apply a common motion image compression process to a motion video that includes frames composed of imaging signals for optical communication and frames composed of imaging signals for motion video, and the light receiving device A1002 may output the encoded motion video data generated from the imaging signals for optical communication and motion video as received data A1003.

[0455] Next, we will describe the operation of the control unit A1004 when the light receiving device A1002 is configured with a light receiving signal processing unit A5000.

[0456] If the light receiving device A1002 is configured with a light receiving signal processing unit A5000, the light receiving device A1002 does not perform demodulation, error correction, or other processing on the imaging data for optical communication. Therefore, the control unit A1004 uses the imaging data for optical communication contained in the light receiving data A1003 to perform demodulation, error correction, and other processing on the optical signal and acquire the data transmitted by the optical signal.

[0457] Furthermore, if the received light data A1003 includes both optical communication imaging data and video imaging data, the control unit A1004 may perform image processing such as pattern recognition on the video imaging data in addition to demodulation and error correction processing on the optical signals included in the optical communication imaging data, and may also control the light receiving device A1002 and the wireless device A1006 based on the results of the image processing such as pattern recognition.

[0458] Examples of signal processing using video image data include, for example, processing to detect people or parts of a person's body such as a face, processing to identify people, processing to detect objects such as cars or drones, processing to identify objects such as cars or drones, processing to detect the movement or motion of detected people or objects, and processing to track detected people or objects. These processes may be performed by extracting features from the video image data according to the purpose of the signal processing, and using the extracted features, or they may be performed using a model created by machine learning with a multi-layered neural network. When using a model created by machine learning with a multi-layered neural network, the video image data may be preprocessed, and the preprocessed data may be input into the model created by machine learning with a multi-layered neural network.

[0459] In the above explanation, it was stated that the control unit A1004 uses image data for video for signal processing, but in addition to image data for video, audio data and data obtained from other sensors may be used, or audio data and data obtained from other sensors may be used instead of image data for video.

[0460] Furthermore, if the light receiving device A1002 is configured with a light receiving signal processing unit A5000 and the light receiving device A1002 outputs encoded video data as light receiving data A1003, the control unit A1004 may perform video decoding processing corresponding to video encoding processing on the encoded video data included in the light receiving data A1003 as part of the above signal processing or as part of the signal processing.

[0461] Next, we will describe an example of the configuration of the light receiving signal processing unit A3003.

[0462] Figure 40 shows the configuration of a light-receiving signal processing unit A7000, which is a third example of the configuration of the light-receiving signal processing unit A3003. The light-receiving signal processing unit A7000 includes a receiving processing unit A7001 and an image data generation unit A7003.

[0463] The receiving unit A7001 of the light receiving signal processing unit A7000 has the same function as the receiving unit A4001 of the light receiving signal processing unit A4000, as explained using Figure 37.

[0464] The image data generation unit A7003 of the light receiving signal processing unit A7000 has the same function as the image data generation unit A5001 of the light receiving signal processing unit A5000, as explained using Figure 38.

[0465] If the light receiving device A1002 is equipped with a light receiving signal processing unit A7000, the light receiving device A1002 controls the light receiving unit A3001 to acquire the imaging signal for video and the imaging signal for optical communication as a received signal A3002. The light receiving signal processing unit A7000 inputs the imaging signal for video to the image data generation unit A7003 and the imaging signal for optical communication to the receiving processing unit A7001. However, it goes without saying that the light receiving signal processing unit A7000 may also input the imaging signal for optical communication to the image data generation unit A5001.

[0466] The light receiving signal processing unit A7000 outputs demodulated data A7002 and video data A7004 as light receiving data A1003.

[0467] In this case, the demodulated data A7002 may have additional information or metadata attached to it, such as time information indicating the time when the modulated signal corresponding to the demodulated data was received. Here, the time information attached to the demodulated data A7002 may be in a format that can identify its relationship with the time information attached to the video data A7004. For example, the light-receiving signal processing unit A7000 may attach the time information of the demodulated data A7002 and the time information of the video data A7004 based on a common clock signal or timeline, or information indicating the relationship between the time information of the demodulated data A7002 and the time information of the video data A7004, such as information indicating the offset of the time information of the video data A7004 with respect to the time information of the demodulated data A7002, may be included in the time information of the demodulated data A4002 or the time information of the video data A5002.

[0468] Furthermore, the demodulated data A7002 may include, as additional information or metadata, positional information indicating the position within the image of the transmitting device or light source that transmitted the modulated signal corresponding to the demodulated data.

[0469] The additional information in demodulated data A7002 may include both time information and location information, or only one of them. Furthermore, the additional information in demodulated data A7002 may include related information other than time information and location information that pertains to the demodulated data.

[0470] While the position information is defined as information indicating the position of the transmitting device or light source within the image, it may be other information. For example, it may be information indicating the region within the image used to detect the optical signal, or it may be information indicating the position in three-dimensional space. The position information in three-dimensional space may, for example, be information indicating the direction in which the light receiving device A1002 is capturing images and the position within the image of the video capture data, or it may be information indicating the coordinate values ​​or region in a coordinate system centered on the light receiving device or communication device estimated from this information. Alternatively, it may be information indicating the coordinate values ​​or region in an arbitrary coordinate system used in GPS or 3D maps, etc., estimated using the position information of the communication device or light receiving device. Furthermore, if the light receiving device A1002 acquires not only video capture data but also distance image data indicating the depth to the captured object, the position in three-dimensional space may be estimated using the distance image data in addition to the video capture data.

[0471] Depth images can be acquired using methods such as TOF (Time-Of-Flight), stereo disparity-based distance measurement, and LIDER (Laser Imaging Detection and Ranging).

[0472] The demodulated data A7002 and the video data A7004 may be transmitted to the control unit A1004 of communication device A1000 or the control unit A1004 of communication device A2000 as multiple separate data streams or data packet sequences, or both the demodulated data A7002 and the video data A7004 may be multiplexed into a data stream in a format that can store both, and transmitted to the control unit A1004 of communication device A1000 or the control unit A1004 of communication device A2000 as a single data stream or data packet sequence.

[0473] Figure 41 shows the configuration of a light receiving device A8000, which is a second example of the configuration of light receiving device A1002. Light receiving device A8000 comprises a first light receiving unit A8001-1, a second light receiving unit A8001-2, a first light receiving signal processing unit A8003-1, and a second light receiving signal processing unit A8003-2.

[0474] The first light-receiving unit A8001-1 is an image sensor such as a CCD, CMOS, or organic CMOS, and the second light-receiving unit A8001-2 is an image sensor such as a CCD, CMOS, or organic CMOS, or a device capable of converting optical signals into electrical signals, such as a photodiode. The light-receiving device A8000 operates the first light-receiving unit A8001-1 in an imaging method for video recording and acquires an imaging signal for video as a received signal A8002-1.

[0475] If the second light-receiving unit A8001-2 is an image sensor, the light-receiving device A8000 operates the second light-receiving unit A8001-2 using a sampling method for receiving optical signals and acquires an imaging signal for optical communication as a received signal A8002-2. On the other hand, if the second light-receiving unit A8001-2 is a device capable of converting optical signals into electrical signals, such as a photodiode, the light-receiving device A8000 acquires a received signal A8002-2 sampled at the sampling rate required for receiving optical signals using the second light-receiving unit A8001-2.

[0476] The first light-receiving signal processing unit A8003-1 has the same function as, for example, the light-receiving signal processing unit A5000 shown in Figure 38, and outputs image data A8004-1, which is imaging data for video, as light-receiving data A1003.

[0477] The second light-receiving signal processing unit A8003-2 has the same function as the light-receiving signal processing unit A4000 shown in Figure 37, for example, and outputs demodulated data A8004-2 as light-receiving data A1003. The second light-receiving signal processing unit A8003-2 also has the same function as the light-receiving signal processing unit A5000 shown in Figure 38, and outputs image data A8004-2, which is imaging data for optical communication, as light-receiving data A1003.

[0478] With this configuration, the light receiver A8000 can simultaneously acquire image data A8004-1, which is imaging data for video, and image data A8004-2, which is demodulated data or imaging data for optical communication. Therefore, it is possible to perform both optical communication and video imaging without any period during which video imaging data cannot be acquired.

[0479] Although the A8000 light receiving device was described using the example of a case where it has two sets of light receiving units and light receiving signal processing units, it may also have N (where N is an integer of 3 or more) sets of light receiving units and light receiving signal processing units.

[0480] Furthermore, the first light-receiving unit A8001-1 and the second light-receiving unit A8001-2 do not necessarily have to be separate elements. For example, some pixels of an image sensor may be used as the first light-receiving unit A8001-1 in an imaging method for video recording, and other pixels of the same image sensor may be used as the second light-receiving unit A8001-2 in a sampling method for receiving optical signals, for optical communication.

[0481] Similarly, if the light receiving device A8000 is equipped with N or more light receiving units and light receiving signal processing units, the pixels included in the first region of the image sensor may be operated using an imaging method for video recording and used for video recording, while the pixels included in each of the second to Nth regions of the image sensor may be operated using a sampling method for receiving optical signals and used for optical communication. If it is not necessary to perform video recording and optical communication simultaneously, the pixels of the image sensor may be divided into multiple regions, and the pixels of each region may be operated using a sampling method for receiving optical signals, thereby performing multiple optical communications in parallel.

[0482] Furthermore, when using an image sensor for video recording or optical communication, it is not necessary to keep all pixels operational at all times. The sensor may include pixels that are temporarily or continuously inactive, i.e., elements whose accumulated charge is not read out by receiving light.

[0483] Next, Figure 42 shows an example of image sensor control when receiving multiple optical signals simultaneously using the image sensor.

[0484] Figure 42(A) shows a scenario where the shooting range, when using an imaging method for video recording, includes four light sources A and D, each transmitting a different optical signal. Each rectangle within the shooting range in Figure 42(A) corresponds to a single pixel.

[0485] At this time, the light receiving device A8000 determines regions A to D that contain light sources A and D, for example as shown in Figure 42 (B), and for each region A to D, it operates the pixels contained in that region using a sampling method for receiving optical signals to acquire the optical signal.

[0486] As an example of a configuration in which optical signals are sampled for reception in each region, a sampling method in an image sensor having a shutter function for each pixel will be described.

[0487] (Example of line scan sampling for each region) As shown in Figure 42(C), we will now describe a case where line scan sampling is performed in region A, where four pixels arranged vertically (in the column direction) form one line. In this case, region A consists of five lines. The light receiving device acquires the change in brightness or color of the modulated optical signal by exposing each of the five lines in region A with a staggered exposure period. However, the size of each region, that is, the number of pixels in the row direction and the number of pixels in the column direction included in each region, is not limited to the example shown in Figure 42 and may be any number. Furthermore, the size of the sampling area for optical communication may be changed according to the size, position of each light source in the screen, and their relative positions to each other. In the example of Figure 42(C), four pixels arranged in the column direction form one line, but for example, five pixels arranged in the row direction may form one line, and in the case of Figure 42(C), it may be considered that there are four lines in the row direction.

[0488] In area A of Figure 42(C), the light receiving device reads the signal from Line 1, which is the leftmost line of area A, and then sequentially reads the signal from the line to the right of the line that was read most recently. Once the reading of the signal from Line 5, which is the rightmost line of area A, is complete, the device returns to Line 1, which is the leftmost line, and repeats the process of reading signals from line to line.

[0489] The light-receiving device performs line scan sampling by acquiring signals in each of regions B through D in Figure 42 (B) using the same processing as in region A. Here, the light-receiving device may expose the leftmost line of all regions at the same time, or at different times. Alternatively, lines in region A and region C located in the same column on the image sensor may be exposed for the same exposure period, and lines in region B and region D located in the same column on the image sensor may be exposed for the same exposure period. However, regions A through D include lines that are exposed for the same exposure period.

[0490] Here, we have described a case where multiple pixels arranged vertically (in columns) are exposed to light for the same period as a single line, and the signal is read out for each line. However, line scan sampling may also be performed by treating multiple pixels arranged horizontally (in rows) as a single line.

[0491] The above description describes a case where at least one pixel in the image sensor is used for both video recording and optical communication, and the system switches between acquiring signals using an imaging method for video recording or a sampling method for optical communication. However, the configuration of the light-receiving device equipped with the image sensor is not limited to this. For example, the image sensor may have a pixel used for optical communication in addition to the pixel used for video recording.

[0492] If an image sensor has pixels used for optical communication in addition to pixels used for video recording, the shape or size of the pixels used for optical communication may differ from the shape or size of the pixels used for video recording.

[0493] Furthermore, the video recording using pixels for video recording and the sampling for optical communication using pixels for optical communication may be controlled independently. In situations where one of the processes is unnecessary, the other process may be stopped, and the power supply to the circuit for acquiring the signals necessary for that process may be partially or completely stopped to suppress power consumption.

[0494] As described above, by performing line scan sampling, it becomes possible to receive different modulated signals from multiple light sources in parallel, as shown in Figure 42(A), thereby improving the data transmission speed.

[0495] Next, an example of the configuration of the control unit A1004 provided in the communication device A1000 or communication device A2000 will be described.

[0496] Figure 43 shows a control unit A10000, which is an example of the physical configuration of control unit A1004. Control unit A10000 includes a CPU (Central Processing Unit) A10001 and memory A10002. Memory A10002 stores programs executed by control unit A1004 and data necessary for processing performed by the control unit. CPU A10001 performs processing based on programs read from memory A10002, for example, to realize the functions of control unit A1004. Memory A10002 also stores data such as image data acquired by a receiving device and reads stored data.

[0497] In this document, the CPU and memory have been described as components of the control unit A10000, but other components may also be included. For example, it may have a GPU (Graphics Processing Unit) in addition to the CPU, or it may have circuits for image processing such as video encoding, video decoding, and pattern recognition on image data for video. Furthermore, the control unit A10000 may include I / O (Input / Output) that controls the transfer of data between the control unit A10000 and connected devices, such as the wireless device A1006.

[0498] Figure 44 shows the configuration of control unit A11000, which is a first example of the configuration of control unit A1004. Control unit A11000 includes a signal processing unit A11002, a wireless control unit A11004, and a light receiving device control unit A11006.

[0499] The signal processing unit A11002 acquires either image data including imaging data for optical communication, or demodulated data that has undergone demodulation and error correction as an optical signal, from the light receiving device A1002 as received data A1003. If the received data A1003 is image data including imaging data for optical communication, the signal processing unit A11002 acquires a received signal corresponding to the modulated signal from the imaging data for optical communication, and acquires demodulated data by performing demodulation and error correction processing on the received signal.

[0500] The wireless control unit A11004 outputs a control signal A1005 to the wireless device A1006 to control its operation. The wireless control unit A11004 transfers the wireless reception data received via the wireless device A1006 to the signal processing unit A11002, and transfers the wireless transmission data to be sent to other communication devices via the wireless device A1006 from the signal processing unit A11002 to the wireless device A1006.

[0501] The signal processing unit A11002 performs signal processing using arbitrary data such as demodulated optical communication data, video image data, and wireless reception data acquired via the light receiving device A1002 and the wireless device A1006. For example, based on the results of the aforementioned signal processing, the signal processing unit A11002 gives instructions to the wireless control unit A11004 to control the wireless device A1006, and instructions to the light receiving device control unit A11006 to control the light receiving device (A11005).

[0502] The light receiving device control unit A11006 controls the light receiving device A1002 based on instructions from the signal processing unit A11002. Examples of control over the light receiving device A1002 include controlling whether the light receiving units A3001, A8001-1, and A8001-2 acquire signals using an imaging method for video recording or a sampling method for receiving optical signals, and setting the pixel area to operate using the sampling method for receiving optical signals when acquiring signals using a sampling method for receiving optical signals with some pixels of the image sensor. However, control over the light receiving device A1002 is not limited to these examples. For example, it may also control the ON / OFF switch of the power to the light receiving device A1002, or switch the signal processing performed on the received light signal inside the light receiving device A1002. Furthermore, some of the controls described here may be performed automatically inside the light receiving device A1002 based on the results of the signal processing on the received light signal.

[0503] Figure 45 shows the configuration of control unit A12000, which is a second example of the configuration of control unit A1004. Control unit A12000 differs from control unit A11000 in that it has an equipment control unit A12002.

[0504] The device control unit A12002 takes the video imaging data acquired by the signal processing unit A11002 and the processing results from the signal processing unit A11002 as input (A12001), generates an image to be displayed in the display unit A2003, and outputs the generated image signal as display information A2002 to the display unit A2003. The device control unit A12002 acquires input information A2005 acquired by the input unit A2004 in response to user operations on the input unit A2004 and transfers it to the signal processing unit A11002.

[0505] With this configuration, the signal processing unit A11002 can perform signal processing based on demodulated optical communication data, video capture data, and wireless reception data acquired via the light receiving device A1002 and wireless device A1006, as well as input information A2005 acquired in response to user operations. For example, based on the results of the aforementioned signal processing, the signal processing unit A11002 can issue instructions to the wireless control unit A11004 to control the wireless device A1006, instructions to the light receiving device control unit A11006 to control the light receiving device (A11005), and instructions to change the image displayed on the display unit A2003.

[0506] The following describes a communication control method that controls the wireless device A1006 based on demodulated data obtained from receiving an optical signal and the results of image processing such as pattern recognition applied to the image capture data for video, as an example of the processing performed by the control unit A1004.

[0507] The signal processing unit A11002 acquires image data for video as received data A1003 from the light receiving device A1002, and performs image processing such as pattern recognition on the image data for video. The wireless control unit A11004 controls the wireless device A1006 based on the results of the image processing in the signal processing unit A11002.

[0508] In the communication control method described in this embodiment, demodulated data with added information is used, which associates demodulated data obtained by receiving an optical signal with additional information such as location information indicating the position on an image of the light source used to transmit the optical signal or the transmitter that transmitted the optical signal. In this embodiment, the information transmitted using optical communication can be anything and is not limited to the transmission of specific information, but in the following description of this communication control method, as an example, a case in which connection information including information necessary for connection or communication with other wireless communication devices such as the SSID of a base station described in Embodiments 3 to 7 is transmitted by optical signal is described.

[0509] The signal processing unit A11002 processes the demodulated data to which additional information has been added, either from the light receiving device A1002 or within the signal processing unit A11002 itself. Here, the demodulated data is connection information corresponding to other wireless communication devices. If there are multiple pieces of connection information acquired, the signal processing unit A11002 controls the communication processing performed by the wireless device A1006 using the additional information corresponding to each piece of connection information and the results of image processing such as pattern recognition.

[0510] The following describes a first example of communication control based on the results of image processing.

[0511] In the first example of communication control based on the results of image processing, the communication devices A1000 and A2000 are cars or devices mounted on cars, and a camera mounted on a car is used as the light receiving device A1002. Figure 46 schematically shows an example of an image taken by a camera that photographs the front of the car. In Figure 46, three other cars A13001, A13002, and A13003 are shown traveling in front of the cars corresponding to the communication devices A1000 and A2000.

[0512] In this embodiment, we will describe an example using a camera that photographs the front of the car, but it goes without saying that the same method can be applied to cameras that photograph the rear or sides of the car.

[0513] Here, the other vehicles A13001, A13002, and A13003 each have a light source such as an LED and a transmitting unit 102 that transmits optical signals using the light source. Any light source provided by the vehicle, such as headlights or taillights, can be used as the light source for optical communication, and which of the multiple light sources provided by the vehicle is used to transmit optical signals can be arbitrarily designed according to the application of optical communication. Furthermore, when multiple light sources provided by the vehicle are used to transmit optical signals, the vehicle may provide a transmitting unit for optical communication for each of the multiple light sources, or a single transmitting unit may transmit optical signals using multiple light sources. Note that the vehicle may also have a light source for optical communication separate from the headlights and taillights.

[0514] Other vehicles A13001, A13002, and A13003 are equipped with a wireless communication device, corresponding to the other communication device A1100 described in Figures 34 and 35, in addition to a transmitter and light source for optical communication. If the vehicle itself and the other vehicles A13001, A13002, and A13003 have functions for transmitting and receiving optical signals and wireless communication, then each vehicle will be configured with a transmitter 102 and a light source 104 for optical communication in the communication device A1000 and A2000. In this case, the control unit A1004 may control the data transmitted by the transmitter 102.

[0515] In the first example of communication control based on the results of image processing, other vehicles A13001, A13002, and A13003 transmit connection information, which is information that can be used to connect to the communication devices installed in each vehicle via optical communication. Below, we will describe the case where the connection information includes information indicating the SSID and the frequency channel used for communication when the communication device installed in each vehicle is operating as a base station.

[0516] In the above explanation, we described an example where the SSID is notified as an identifier for determining the communication partner included in the connection information. However, the identifier information included in the connection information is not limited to the SSID. For example, it could be a physical address such as the MAC (Media Access Control) address of another communication device, or a logical address such as the IP (Internet Protocol) address of another communication device. Furthermore, if the identifier information is not used by the communication device to select other communication devices with which it communicates directly, but rather to select resources accessed via a network such as the Internet, it could be the address of a server communicating via the network such as the Internet, or a URL (Uniform Resource Locator), URN (Uniform Resource Name), or URI (Uniform Resource Identifier) ​​used to identify resources on the Internet. Any identifier information that can identify other communication terminals or resources on the Internet that are being accessed can be used as the identifier information included in the connection information.

[0517] The above explanation described a case where connection information notifies the frequency channel being used. However, connection information does not necessarily have to include information about the frequency channel being used, nor does it have to include other information. Examples of other information that can be used as connection information include information about the encryption key, the type of physical layer transmission method standard supported, and the supported data format and communication protocol.

[0518] Figure 47 schematically shows the connection information obtained by demodulating the optical signals transmitted by the respective transmitters of other vehicles A13001, A13002, and A13003 using a light source, in the optical receiver A1002 or control unit A1004 of communication devices A1000 and A2000. Communication devices A1000 and A2000 obtain connection information from the optical signal transmitted by other vehicle A13001 that the SSID is "XXX" and the frequency channel being used is "1", obtain connection information from the optical signal transmitted by other vehicle A13002 that the SSID is "YYY" and the frequency channel being used is "3", and obtain connection information from the optical signal transmitted by other vehicle A13003 that the SSID is "ZZZ" and the frequency channel being used is "3".

[0519] Some of this connection information can be replaced by information obtained by the wireless device A1006, which is included in communication devices A1000 and A2000, performing carrier sensing over a certain period and receiving signals transmitted from each of several other communication devices. However, it is difficult for communication devices A1000 and A2000 to identify which of several other communication devices in the vicinity transmitted those signals, and there is a possibility that they may connect to and communicate with a communication device other than the one they actually intend to communicate with.

[0520] Therefore, in the first example of communication control based on the results of image processing, the control unit A1004 of the communication devices A1000 and A2000 performs image processing on the video image data captured by the light receiving device A1002 to detect, for example, the other cars A13001, A13002, and A13003 from the image in Figure 46. At this time, the control unit A1004 associates each of the other cars A13001, A13002, and A13003 detected from the image with the three connection information received via optical communication, based on the position of the light source of the three received optical signals. This makes it possible to identify the connection information to be used when communicating wirelessly with each of the three cars detected from the image.

[0521] Next, the control unit A1004 determines the relative positions of the other cars A13001, A13002, and A13003 from the image, as well as the relative positions of each car to the own car, and selects a target for wireless communication. For example, the control unit A1004 may select car A13003, which is the closest to the own car, as the communication target. Alternatively, the control unit A1004 may determine the lane each car is traveling in and select car A13001, which is traveling in the same lane as the own car and is in the foreground in the image, as the communication partner.

[0522] This configuration allows for the association of information that is difficult to link to real-world devices using wireless communication alone, such as identifiers like SSIDs and addresses in wireless communication, with objects detected by signal processing such as pattern recognition from sensing data obtained from sensors, such as images acquired by image sensors. As a result, it facilitates the connection to an appropriate communication partner when acquiring information such as the surrounding environment and the movement of surrounding vehicles for purposes such as controlling autonomous driving, including driver assistance.

[0523] Next, we will describe a second example of communication control based on the results of image processing.

[0524] In the second example of communication control based on image processing results, the configuration of the vehicle equipped with communication devices A1000, A2000, or the vehicle itself equipped with communication devices A1000, A2000, and the configurations of other vehicles A13001, A13002 are the same as in the first example of communication control based on image processing results. The second example of communication control based on image processing results differs from the first example of communication control based on image processing results in that another vehicle A15003, which does not have the function of transmitting optical signals on behalf of other vehicle A13003, is also in operation.

[0525] Figure 48 schematically shows an example of an image taken by a camera that photographs the front of a car in a second example of communication control based on the results of image processing. In Figure 48, three other cars A13001, A13002, and A15003 are shown traveling in front of the cars corresponding to communication devices A1000 and A2000.

[0526] Figure 49 schematically shows the connection information obtained by demodulating the optical signals transmitted by the respective transmitters of other vehicles A13001 and A13002 using a light source, in the optical receiver A1002 or control unit A1004 of communication devices A1000 and A2000. Communication devices A1000 and A2000 obtain connection information from the optical signal transmitted by other vehicle A13001 that the SSID is "XXX" and the frequency channel being used is "1", and obtain connection information from the optical signal transmitted by other vehicle A13002 that the SSID is "YYY" and the frequency channel being used is "3". At this time, since other vehicle A15003 does not have the function of transmitting optical signals, communication devices A1000 and A2000 cannot obtain connection information regarding other vehicle A15003.

[0527] In a second example of communication control based on image processing results, the control unit A1004 of the communication devices A1000 and A2000 performs image processing on the video image data captured by the light receiver A1002 to detect, for example, the other vehicles A13001, A13002, and A15003 from the image in Figure 48. At this time, based on the position of the light source of the two received optical signals, the control unit A1004 associates the two connection pieces received via optical communication with the other vehicles A13001 and A13002 from the other vehicles A13001, A13002, and A15003 detected from the image. This makes it possible to identify the connection piece to be used when communicating wirelessly with the other vehicles A13001 and A13002 detected from the image, and to identify that the base station or communication device with an SSID of "XXX" or "YYY" is not the SSID to be used to communicate with the other vehicle A15003.

[0528] First, let's explain the case where another vehicle, A15003, does not have the function to transmit optical signals, but does have the function to perform wireless communication using the SSID "PPP".

[0529] At this time, the wireless device A1006 detects three SSIDs, "XXX", "YYY", and "PPP", as SSIDs of other communication devices installed in vehicles within communication range by performing carrier sensing. The control unit A1004 determines that "PPP", which is different from "XXX" and "YYY", which are SSIDs included in the connection information received as optical signals, is the SSID to be used to communicate with the other vehicle A15003, and associates the other vehicle A15003 with the SSID "PPP".

[0530] The control unit A1004 determines the relative positions of other vehicles A13001, A13002, and A15003 from the image, as well as the relative positions of each vehicle to the own vehicle, and selects a target for wireless communication. For example, the control unit A1004 may select vehicle A15003, which is the closest to the own vehicle, as the communication target. Alternatively, the control unit A1004 may determine the lane each vehicle is traveling in and select vehicle A13001, which is traveling in the same lane as the own vehicle and is in the foreground in the image, as the communication partner.

[0531] This configuration allows for the association of information that is difficult to link to real-world devices using wireless communication alone, such as identifiers like SSIDs and addresses in wireless communication, with objects detected by signal processing such as pattern recognition from sensing data obtained from sensors, such as images acquired by image sensors. As a result, it facilitates the connection to an appropriate communication partner when acquiring information such as the surrounding environment and the movement of surrounding vehicles for purposes such as controlling autonomous driving, including driver assistance.

[0532] Next, we will describe the case where another vehicle A15003 does not have both the ability to transmit optical signals and the ability to perform wireless communication.

[0533] At this time, the wireless device A1006 detects two SSIDs, "XXX" and "YYY," as SSIDs of other communication devices installed in cars within communication range by performing carrier sensing. The control unit A1004 determines that, since no SSIDs other than "XXX" and "YYY," which are included in the connection information received as optical signals, are detected as SSIDs of other communication devices installed in cars, the other car A15003 does not have the function to perform wireless communication, or is not in a relationship that would allow it to perform wireless communication.

[0534] The control unit A1004 determines the relative positions of other vehicles A13001, A13002, and A15003 from the image, as well as the relative positions of each vehicle to the own vehicle, and selects either vehicle A13001 or vehicle A13002 as the target for wireless communication. For example, the control unit A1004 may select the vehicle A13002 that is closest to the own vehicle and capable of communication as the communication target. Alternatively, the control unit A1004 may determine the lane each vehicle is traveling in and select the vehicle A13001 that is traveling in the lane the own vehicle is in and is in the foreground in the image as the communication partner.

[0535] This configuration allows for the association of information that is difficult to associate with devices in real space using only wireless communication, such as identifiers like SSIDs and addresses in wireless communication, with objects detected by signal processing such as pattern recognition from sensing data obtained from sensors, such as images acquired by an image sensor. As a result, for example, it can be determined that information cannot be obtained through communication with another vehicle A15003 that is driving directly ahead. For example, when controlling autonomous driving, including driver assistance, it is possible to prevent misidentification of other vehicles that can communicate, such as A13001 or A13002, as other vehicles A15003, thereby promoting the provision of appropriate autonomous driving control.

[0536] Next, we will describe a third example of communication control based on the results of image processing.

[0537] In the third example of communication control based on image processing results, the configuration of the communication devices A1000, A2000, or the configuration of the vehicle equipped with communication devices A1000, A2000, and the configurations of the other vehicles A13002, A13003 are the same as in the first example of communication control based on image processing results. The third example of communication control based on image processing results differs from the first example of communication control based on image processing results in that a police vehicle A17001 is driving instead of the other vehicle A13001. The police vehicle A17001 differs from the other vehicle A13001 in that it is a police vehicle, but it has the same configuration as the other vehicle A13001 and has the functions of transmitting optical signals and wireless communication.

[0538] Figure 50 schematically shows an example of an image taken by a camera that photographs the front of a car in a third example of communication control based on the results of image processing. In Figure 50, other cars A13002 and A13003 and a police vehicle A17001 are shown traveling in front of the cars corresponding to communication devices A1000 and A2000.

[0539] Figure 51 schematically shows the connection information obtained by demodulating the optical signals transmitted by the respective transmitters of other vehicles A17001, A13002, and A13003 using light sources, in the optical receiver A1002 or control unit A1004 of communication devices A1000 and A2000. Communication devices A1000 and A2000 obtain connection information from the optical signal transmitted by police vehicle A17001 that the SSID is "QQQ" and the frequency channel being used is "1", obtain connection information from the optical signal transmitted by other vehicle A13002 that the SSID is "YYY" and the frequency channel being used is "3", and obtain connection information from the optical signal transmitted by other vehicle A13003 that the SSID is "ZZZ" and the frequency channel being used is "3".

[0540] In a third example of communication control based on image processing results, the control unit A1004 of the communication devices A1000 and A2000 performs image processing on the video image data captured by the light receiver A1002 to detect, for example, police vehicle A17001 and other vehicles A13002 and A13003 from the image in Figure 50. At this time, the control unit A1004 associates the three connection pieces received via optical communication with the police vehicle A17001 and other vehicles A13002 and A13003 detected from the image, based on the position of the light sources of the three received optical signals. This makes it possible to identify the connection piece to be used when performing wireless communication for each of the police vehicle A17001 and other vehicles A13002 and A13002 detected from the image.

[0541] The control unit A1004 uses information such as the vehicle's appearance to perform a detailed classification of the three vehicles recognized in the image processing, determining whether or not they are police vehicles, and recognizes that vehicle A17001 is a police vehicle. Of the police vehicle A17001 and the other vehicles A13002 and A13003, the control unit A1004 selects the police vehicle A17001, which has a higher priority for acquiring information, as the target for wireless communication.

[0542] With this configuration, when recognizing an object using signal processing such as pattern recognition from sensing data obtained from sensors, such as images acquired by an image sensor, the recognized object can be further classified, and communication control can be performed based on that classification.

[0543] It should be noted that the control described above, which selects police vehicles as high-priority communication partners for information acquisition, is merely an example, and different control may be performed when a police vehicle is recognized. For example, if police vehicle A17001 transmits an optical signal that includes an identifier to identify the police vehicle, the control unit A1004 may, instead of directly wirelessly connecting to the police vehicle, specify the identifier received from police vehicle A17001 via optical signal to another vehicle A13002 or another vehicle A13003 to acquire information about police vehicle A17001.

[0544] Furthermore, when a police vehicle is detected by image processing, instead of always performing the same communication control, communication control prioritizing the collection of information about the police vehicle may be performed when it is recognized that the warning lights of the recognized police vehicle are illuminated, or when the communication devices A1000 and A2000 are equipped with microphones as sensors other than image sensors, and the control unit A1004 detects a siren sound by applying pattern recognition signal processing to the audio data acquired by the microphone.

[0545] Furthermore, when using audio data acquired by a microphone to detect sounds generated by other devices, a modulated signal generated based on the transmitted data, such as the identifier of the other device, may be transmitted simultaneously.

[0546] This configuration allows for the association between the device that generated the sound recognized by signal processing such as pattern recognition and the transmitted data, such as the identifier sent as the sound signal. As a result, it may be possible to easily identify the device that generated the detected sound, for example, in an environment where there are multiple devices with known identifiers.

[0547] Furthermore, sound signals may be used instead of optical signals. In this case, the optical receiver A1002 in communication devices A1000 and A2000 is replaced with a sound detection device such as a microphone. Additionally, by using a sound detection device capable of determining the direction of sound arrival, such as an array microphone, the correspondence between the device that generated the sound being detected and the sound signal can be made even more accurate.

[0548] Furthermore, the communication devices A1000 and A2000 according to this embodiment may have multiple wireless devices. For example, the communication devices A1000 and A2000 may be equipped with multiple wireless devices corresponding to communication methods defined by different standards, or they may be equipped with multiple wireless devices corresponding to the same communication method.

[0549] Furthermore, if the communication devices A1000 and A2000 in this embodiment are a vehicle or communication devices mounted on a vehicle, the light receiving device A1002 may be, for example, a camera included in a drive recorder, a camera for a rearview monitor, a camera for checking the area around the vehicle, or a camera used to display images on a monitor in place of side mirrors. In this way, by receiving optical signals using a camera mounted for purposes other than optical communication, the communication control disclosed in this embodiment can be realized without adding a new camera, thereby reducing costs and promoting the widespread adoption of optical signal receiving functionality. Moreover, since such cameras are installed to capture areas that are necessary for the driver, that is, areas from which important information for operating the vehicle can be obtained, combining signal processing such as image recognition with wireless communication to collect more information can facilitate the provision of appropriate autonomous driving control and the provision of information to the driver.

[0550] This disclosure describes a method and apparatus for demodulating a transmitted signal, which is received by a sensor such as an image sensor or a microphone, using sensing data obtained by the sensor.

[0551] In the above embodiment, if signal processing such as image recognition is performed on sensing data obtained from the sensor, it becomes possible to determine the correspondence between the real-space object detected or recognized from the sensing data and the source of the transmitted signal.

[0552] In the above embodiment, if information such as SSID, address, and identifier used in processing via a network including communication is transmitted using a transmission signal, it becomes easier to associate the information used in processing via a network including communication with objects in the real world. In other words, information used in processing via a network, which was previously difficult to associate with objects in the real world, can now be used based on sensing data obtained from the real world.

[0553] In the above embodiment, if an image sensor is used as the sensor and information used in processing via a network including communication is transmitted as an optical signal, the reliability of the correspondence between visible objects and information used in processing via a network including communication can be improved.

[0554] In the above embodiment, if identifiers used for communication, such as SSID and address, are transmitted as optical signals, and the identifier of the target to connect to via communication is selected based on the results of signal processing of image recognition, communication control can be performed based on the positional relationship and attributes of objects in real space, and communication can be performed by specifying the target to connect to, and information can be acquired or control instructions can be given. As a result, for example, it becomes possible to provide a means to realize communication with an appropriate communication partner in an environment where an unspecified number of devices are within the communication range, and the creation and dissemination of new services via communication can be promoted.

[0555] Embodiment 8 of this disclosure has been described above.

[0556] Although the configuration shown in Figure 5 has been described as an example of a communication system that performs visible light communication, the configuration of a communication system that performs visible light communication is not limited to the configuration shown in Figure 5. For example, a configuration like the one shown in Figure 52 is also acceptable (see, for example, "IEEE 802.11-16 / 1499r1"). In Figure 52, the transmitted signal is transmitted as an optical signal in the baseband band without being upconverted. That is, the device that transmits the optical signal in this embodiment (i.e., the device equipped with a light source) may have the transmitting side configuration shown in Figure 52, and the terminal that receives the optical signal in this embodiment may have the receiving side configuration shown in Figure 52.

[0557] (Embodiment 9) In this embodiment, Figure 52 will be explained in more detail.

[0558] Let's explain Figure 52 in detail. The symbol mapping unit receives the transmission data, performs mapping based on the modulation scheme, and outputs a symbol sequence (ci).

[0559] The pre-equalization processing unit takes a symbol sequence as input, performs pre-equalization processing on the symbol sequence to reduce the need for equalization processing on the receiving end, and outputs the pre-equalization processed symbol sequence.

[0560] The Hermitian symmetry processing unit takes the symbol sequence after equalization preprocessing as input, assigns subcarriers to the symbol sequence after equalization preprocessing to ensure Hermitian symmetry, and outputs a parallel signal.

[0561] The inverse (fast) Fourier transform section takes a parallel signal as input, applies an inverse (fast) Fourier transform to the parallel signal, and outputs the signal after the inverse (fast) Fourier transform.

[0562] The parallel-serial and cyclic prefix addition units take the signal after the inverse (fast) Fourier transform as input, perform parallel-serial conversion and add a cyclic prefix, and output the signal after signal processing.

[0563] The digital-to-analog conversion unit receives the processed signal as input, performs digital-to-analog conversion, and outputs an analog signal. This analog signal is then output as light from one or more sources, such as LEDs.

[0564] Note that the equalization preprocessing and Hermitian symmetry processing sections are optional. In other words, signal processing in the equalization preprocessing and Hermitian symmetry processing sections may not be performed.

[0565] A photodiode takes light as input and obtains the received signal using a Transimpedance Amplifier (TIA).

[0566] The analog-to-digital conversion unit performs analog-to-digital conversion on the received signal and outputs a digital signal.

[0567] The cyclic prefix removal and serial-to-parallel conversion unit takes a digital signal as input, performs cyclic prefix removal, then performs serial-to-parallel conversion, and finally takes a parallel signal as input.

[0568] The (Fast) Fourier Transform (FCR) unit takes a parallel signal as input, performs a (Fast) Fourier Transform, and outputs the signal after the (Fast) Fourier Transform.

[0569] The detection unit takes the Fourier-transformed signal as input, performs detection, and outputs the received symbol sequence.

[0570] The symbol demapper takes a received symbol sequence as input, performs demapping, and obtains a received data sequence.

[0571] As described above, each embodiment can be implemented similarly even if the transmitting device for transmitting an optically modulated signal and the receiving device for receiving an optically modulated signal are applied to each embodiment of this specification.

[0572] (Embodiment 10) In Embodiment 8, an example was described using Figure 42 in which a transmitting device transmits multiple optically modulated signals and a receiving device receives multiple optically modulated signals. This embodiment will describe the example in this case.

[0573] Figure 53 shows an example configuration of the transmitting and receiving devices in this embodiment. In Figure 53, the transmitting device 100 transmits multiple optical modulation signals, and the receiving device 150 receives multiple optical modulation signals and obtains received data. In Figure 53, components that operate in the same way as in Figure 6 are given the same numbers.

[0574] The transmitting device in Figure 53 transmits M optically modulated signals, where M is an integer greater than or equal to 2.

[0575] The transmitter A2002_i receives data A2001_i and control signal A2005 as input. Based on the error correction coding method information and transmission method information contained in control signal A2005, it performs error correction coding and signal processing based on the transmission method to generate and output the optical modulation signal A2003_i. Note that i is an integer between 1 and M.

[0576] Then, the optical modulation signal A2003_i is transmitted from the light source A2004_i.

[0577] The light-receiving unit A2051 of an image sensor or similar device receives light corresponding to the optical modulation signal A2003_i. At this time, the light-receiving unit A2051 receives light corresponding to M optical modulation signals. The method for receiving multiple light signals in the light-receiving unit A2051 is as described in Embodiment 8, for example.

[0578] The light receiving unit A2051 outputs an optical reception signal A2052_i corresponding to the optical modulation signal 2003_i. Note that i is an integer between 1 and M.

[0579] The receiver A2053_i receives the optical reception signal A2052_i corresponding to the optical modulation signal A2003_i as input, performs processing such as demodulation and error correction decoding, and outputs the received data A2054_i corresponding to the data A2001_i.

[0580] The data acquisition unit A2055 takes data A2054_1, data A2054_2, ..., and data A2054_M as input and generates and outputs data A2056.

[0581] Figure 54 shows an example of the configuration of the transmitting and receiving devices in this embodiment, which differs from Figure 53. In Figure 54, components that operate similarly to those in Figure 53 are given the same numbers.

[0582] The distribution unit A2102 takes information A2101 and control signal A2005 as inputs, and performs error correction coding on information A2101 based on the information regarding the error correction coding method contained in control signal A2005, generating error-corrected coded data. Then, the distribution unit A2102 distributes the error-corrected coded data and outputs error-corrected coded data A2001_i.

[0583] The distribution of the M error-corrected encoded data A2001_i can be carried out in any way. For example, the error-corrected encoded data may be divided into M parts, and each of the M divided data sequences may be assigned to the error-corrected encoded data A2001_i. Alternatively, M data sequences consisting of identical data may be generated from the error-corrected encoded data, and each data sequence may be assigned to the error-corrected encoded data A2001_i. The method of assigning to the error-corrected encoded data A2001_i is not limited to these methods; it is sufficient to generate M data sequences from the error-corrected encoded data and assign each data sequence to the error-corrected encoded data A2001_i.

[0584] The transmitter A2002_i receives data A2001_i and control signal A2005 as inputs. Based on the transmission method information contained in control signal A2005, it performs signal processing according to the transmission method to generate and output the optical modulation signal A2003_i. Note that i is an integer between 1 and M.

[0585] Then, the optical modulation signal A2003_i is transmitted from the light source A2004_i.

[0586] The light-receiving unit A2051 of an image sensor or similar device receives light corresponding to the optical modulation signal A2003_i. At this time, the light-receiving unit A2051 receives light corresponding to M optical modulation signals. The method for receiving multiple light signals in the light-receiving unit A2051 is as described in Embodiment 8, for example.

[0587] The light receiving unit A2051 outputs an optical reception signal A2052_i corresponding to the optical modulation signal 2003_i. Note that i is an integer between 1 and M.

[0588] The receiver A2053_i receives the optical reception signal A2052_i corresponding to the optical modulation signal A2003_i as input, performs processing such as demodulation, and outputs the received data (log-likelihood ratio) 2054_i corresponding to the data A2001_i.

[0589] The error correction and decoding unit A2151 takes the received data (log-likelihood ratio) 2054_1, received data (log-likelihood ratio) 2054_2, ..., received data (log-likelihood ratio) 2054_M as input, performs error correction and decoding, and outputs the received data A2152.

[0590] Figure 55 shows an example of the frame configuration of the optically modulated signal transmitted by the transmitting device 100 in Figures 53 and 54.

[0591] The frame configuration A2201_1 in Figure 55 shows an example of the frame configuration of the optical modulation signal A2003_1 in Figures 53 and 54. In frame configuration A2201_1, the horizontal axis represents time.

[0592] Therefore, frame configuration A2201_i in Figure 55 shows an example of the frame configuration of the optical modulation signal A2003_i in Figures 53 and 54. In frame configuration A2201_i, the horizontal axis represents time, and i is assumed to be an integer between 1 and M (i.e., Figure 55 shows M frame configurations).

[0593] As shown in frame configuration A2201_i, the transmitter 100 in Figures 53 and 54 transmits the preamble A2210_i, control information symbol A2211_i, and data symbol A2212_i in the optical modulation signal A2003_i.

[0594] Figure 56 shows an example of the reception state in the receiving device 150. In the following example, it is assumed that the transmitting device 100 in Figures 53 and 54 is equipped with 16 (M=16) light sources.

[0595] In Figure 56, A2300 represents an image sensor, which is an example of a light-receiving unit, and A2301_1 represents the light emitted by the first light source, which contains the first optical modulation signal. The first optical modulation signal corresponds to A2201_1 in Figure 55.

[0596] Therefore, in Figure 56, A2301_i is the light emitted by the i-th light source, and this light contains the i-th optical modulation signal. The i-th optical modulation signal corresponds to A2201_i in Figure 55. Note that i is an integer between 1 and 16.

[0597] In the example of the receiving state in the receiving device 150 shown in Figure 56, the light receiving unit of the receiving device 150 receives light from a fourth light source containing a fourth optical modulation signal, light from an eighth light source containing an eighth optical modulation signal, and light from a twelfth light source containing a twelfth optical modulation signal.

[0598] For example, if the transmitter 100 in Figures 53 and 54 transmits 16 optically modulated signals from 16 light sources, then in the state shown in Figure 56, the receiver 150 in Figures 53 and 54 is unable to receive all 16 optically modulated signals, making it difficult to obtain correct received data. A method to overcome this problem will be described below.

[0599] Figure 57 shows an example of the preamble A2210_i, the information contained in the control information symbol A2211_i, and the symbol configuration of the frame configuration A2201_i of the optical modulation signal A2003_i in Figure 55. Note that i is an integer between 1 and M (=16).

[0600] In frame configuration A2201_i, the preamble A2210_i and control information symbol A2211_i include, as shown in Figure 57, a symbol A2401 for signal detection, a symbol A2402 for synchronization, a symbol A2403 containing information about the number of optically modulated signals being transmitted, and a symbol A2404 containing information about the error correction coding method, transmission method, and modulation scheme.

[0601] The symbol A2401 for signal detection is a symbol that allows the receiving device 150 to know that an optically modulated signal is present. By detecting this symbol, the receiving device 150 knows that an optically modulated signal is present.

[0602] The synchronization symbol A2402 is a symbol used by the receiving device 150 to perform time synchronization (which may include frequency synchronization). By using this symbol, the receiving device 150 can perform time synchronization, enabling high-precision demodulation of each symbol.

[0603] Symbol A2403, which contains information about the number of optically modulated signals being transmitted, is a symbol used to notify the number of optically modulated signals being transmitted by the transmitting device 100. In the state shown in Figure 56, symbol A2403, which contains information about the number of optically modulated signals being transmitted, is transmitting the information "16".

[0604] In the reception state shown in Figure 56, the receiving device 150 receives symbol A2403, which contains information about the number of optically modulated signals being transmitted, and thus learns that the transmitting device 100 is transmitting "16" optically modulated signals. However, in the reception state shown in Figure 56, the receiving device 150 learns that it has only received 3 of the 16 optically modulated signals.

[0605] Symbol A2404, which contains information about the error correction coding method, transmission method, and modulation scheme, is, for example, a symbol containing information about the error correction coding method, transmission method, and modulation scheme used in the data symbol (a symbol for transmitting data) of the optical modulation signal A2003_i. By receiving this symbol, the receiving device 150 can determine the error correction coding method, transmission method, and modulation scheme used in the optical modulation signal A2003_i.

[0606] In the frame configuration shown in Figure 55, the transmitter 100 transmits the symbols shown in Figure 57 for optical modulation signals A2003_1 to A2003_16. In this way, even when the receiver 150 has not received all of the optical modulation signals, as shown in Figure 56, it is possible to know the number of optical modulation signals transmitted by the transmitter 100, and thus the receiver 150 can know whether or not it has received all of the optical modulation signals. If not all of the optical modulation signals have been received, signal processing can be stopped midway, thereby reducing unnecessary power consumption.

[0607] Figure 58 shows an example of the preamble A2210_i, control information symbol A2211_i, and symbol configuration of the optical modulation signal A2003_i in Figure 55, which differs from Figure 57. Note that i is an integer between 1 and M (=16). Also, in Figure 58, elements that operate similarly to those in Figure 57 are given the same numbers and have already been explained, so the explanation is omitted.

[0608] In Figure 58, compared to Figure 57, symbol A2501, which contains information about the optical modulation signal number, is added as a symbol transmitted by the transmitter 100.

[0609] Figure 58 shows the frame configuration A2201_i of the optical modulation signal A2003_i in Figure 55. In other words, it is the frame configuration of the i-th optical modulation signal, so the symbol A2501, which contains information about the number of the optical modulation signal, contains the information "i".

[0610] For example, the symbol A2501, which contains information about the number of the optical modulation signal transmitted by the transmitter 100 in the first optical modulation signal, will contain the information "1".

[0611] In the reception state shown in Figure 56, the receiver 150 receives symbol A2403, which contains information about the number of optically modulated signals being transmitted, and thus learns that the transmitter 100 is transmitting "16" optically modulated signals. The receiver 150 then receives "symbol A2501 containing information about the number of optically modulated signals" included in the fourth optically modulated signal, "symbol A2501A containing information about the number of optically modulated signals" included in the eighth modulated signal, and "symbol A2501A containing information about the number of optically modulated signals" included in the twelfth modulated signal. Thus, the receiver 150 learns that it has received the fourth, eighth, and twelfth optically modulated signals. Knowing this, the receiver 150 performs actions to improve the reception, which improves the quality of data reception. The details of these actions will be explained later.

[0612] Figures 59 and 60 show other examples of the reception status in the receiving device 150. Note that in Figures 59 and 60, components that operate similarly to those in Figure 56 are given the same number and have already been explained, so their explanation is omitted.

[0613] In the example of the receiving state in the receiving device 150 shown in Figure 59, the light receiving unit A2300 of the receiving device 150 receives light from a first light source containing a first optical modulation signal to light from a 16th light source containing a 16th optical modulation signal, that is, 16 optical modulation signals. In the case of Figure 59, for example, the first optical modulation signal is being received in the upper left of the light receiving unit A2300.

[0614] In the example of the receiving state in the receiving device 150 shown in Figure 60, the light receiving unit A2300 of the receiving device 150 receives light from a first light source containing a first optical modulation signal to light from a 16th light source containing a 16th optical modulation signal, that is, 16 optical modulation signals. In the case of Figure 60, for example, the first optical modulation signal is received in the lower right of the light receiving unit A2300, which is different from Figure 59.

[0615] The reception states in Figures 59 and 60 are merely examples, and the conditions under which the receiving device 150 receives the first to 16th optical modulation signals will vary depending on the environment. Considering this, as shown in Figure 58, each optical modulation signal has a symbol A2501 containing information about the optical modulation signal number, so the receiving device 150 can determine which optical modulation signal was received at which part of the light-receiving section. Furthermore, when the receiving device 150 obtains the i-th received data from the received signal of the i-th optical modulation signal and needs to rearrange the data from the first to the 16th received data, it can identify which optical modulation signal the received data is from the symbol A2501 containing information about the optical modulation signal number. This enables the correct rearrangement of the received data, thereby improving the quality of data reception.

[0616] Next, we will explain a different frame configuration method than the one described above.

[0617] Figure 55 shows an example of the frame configuration of the optically modulated signal transmitted by the transmitting device 100 in Figures 53 and 54, and since this has already been explained, the explanation will be omitted.

[0618] For example, Figure 57 shows the preamble and control information symbol configuration for frame configuration A2201_1 in optical modulation signal A2003_1 in Figure 55, and Figure 61 shows the preamble and control information symbol configuration for frame configuration A2201_2 in optical modulation signal A2003_2 to frame configuration A2201_16 in optical modulation signal A2003_16. In Figure 61, elements that operate similarly to those in Figure 57 are given the same numbers, and a distinctive feature of Figure 61 is that it does not include symbol A2403, which contains information about the number of optical modulation signals being transmitted. In other words, the transmitting device 100 transmits symbol A2403, which contains information about the number of optical modulation signals being transmitted, using only optical modulation signal A2003_1.

[0619] In this case, in the receiving state of the receiver 150 shown in Figure 56, the receiver 150 has not obtained "symbol A2403 which contains information about the number of optically modulated signals being transmitted," and therefore cannot determine the number of optically modulated signals transmitted by the transmitter 100. As a result, the receiver 150 can determine that it is difficult to receive the data correctly, stop the signal processing for the receiving operation, and reduce unnecessary power consumption.

[0620] In this example, it is stated that "transmitting device 100 transmits symbol A2403, which contains information about the number of optically modulated signals being transmitted, only with optically modulated signal A2003_1." However, this is not limited to this example. If "transmitting device 100 transmits symbol A2403, which contains information about the number of optically modulated signals being transmitted, with some of the optically modulated signals A2003_1 to A2003_16," the same effect as described above can be obtained.

[0621] Let me give another example.

[0622] Figure 55 shows an example of the frame configuration of the optically modulated signal transmitted by the transmitting device 100 in Figures 53 and 54, and since this has already been explained, the explanation will be omitted.

[0623] For example, Figure 58 shows the preamble and control information symbol configuration for frame configuration A2201_1 in optical modulation signal A2003_1 in Figure 55, and Figure 62 shows the preamble and control information symbol configuration for frame configuration A2201_2 in optical modulation signal A2003_2 to frame configuration A2201_16 in optical modulation signal A2003_16. In Figure 62, components that operate similarly to those in Figures 57 and 58 are given the same numbers, and a distinctive feature of Figure 62 is that it does not include "symbol A2403, which contains information about the number of optical modulation signals being transmitted." In other words, the transmitting device 100 transmits "symbol A2403, which contains information about the number of optical modulation signals being transmitted" only with optical modulation signal A2003_1.

[0624] In this case, in the receiving state of the receiver 150 shown in Figure 56, the receiver 150 has not obtained "symbol A2403 which contains information about the number of optically modulated signals being transmitted," and therefore cannot determine the number of optically modulated signals transmitted by the transmitter 100. As a result, the receiver 150 can determine that it is difficult to receive the data correctly, stop the signal processing for the receiving operation, and reduce unnecessary power consumption.

[0625] In this example, it is stated that "transmitting device 100 transmits symbol A2403, which contains information about the number of optically modulated signals being transmitted, only with optically modulated signal A2003_1." However, this is not limited to this example. If "transmitting device 100 transmits symbol A2403, which contains information about the number of optically modulated signals being transmitted, with some of the optically modulated signals A2003_1 to A2003_16," the same effect as described above can be obtained.

[0626] As yet another example, "the transmitting device 100 may be configured to transmit a preamble and control information symbols for some of the optical modulation signals A2003_1 to A2003_16."

[0627] As described above, when the transmitting device transmits multiple optical modulation signals, as explained in this embodiment, the receiving device can obtain the effect of high data reception quality or reduced power consumption by transmitting optical modulation signals.

[0628] In this embodiment, the number of optically modulated signals transmitted by the transmitting device was described as 16, but this is not the only option. For example, if the transmitting device has the configuration shown in Figure 53, the number of optically modulated signals transmitted may be changed depending on the transmission time. For example, 16 optically modulated signals may be transmitted in the first time, 8 optically modulated signals in the second time, and 1 optically modulated signal in the third time. In this example, in the first time, the symbol A2404 containing information about the number of optically modulated signals being transmitted will transmit "16", in the second time, the symbol A2404 containing information about the number of optically modulated signals being transmitted will transmit "8", and in the third time, the symbol A2404 containing information about the number of optically modulated signals being transmitted will transmit "1".

[0629] In this embodiment, the frame configuration shown in Figure 55 was used as an example, but the frame configuration is not limited to this, and other symbols may be present in the frame. Also, the order in which symbols are transmitted is not limited to the order shown in Figure 55.

[0630] Furthermore, while Figures 57, 58, 61, and 62 have been described as configurations for preambles and control information symbols, it is possible to operate similarly even if some symbols are missing in each figure, or if different symbols are present in each figure. In other words, the configuration of preambles and control information symbols is not limited to the configurations shown in Figures 57, 58, 61, and 62. Also, the order in which the symbols constituting the preamble and control information symbols are transmitted is not limited to the examples shown in Figures 57, 58, 61, and 62.

[0631] (Embodiment 11) In this embodiment, for example, a method for improving the data reception quality of the receiving device 150 when the receiving state of the receiving device 150 is as shown in Figure 56 will be described.

[0632] As described in Embodiment 10, if the receiving device 150 is in a situation like that shown in Figure 56, for example, it will be difficult for the receiving device 150 to correctly obtain the received data. In addition, the receiving state of the receiving device 150 may be as shown in Figure 63. In Figure 63, components that operate in the same way as in Figure 56 are given the same numbers.

[0633] In the case of Figure 63, because the area illuminated by each light source in the light-receiving part such as the image sensor is small, a problem arises in which the data reception quality at the receiving device 150 deteriorates. Furthermore, when using a line scan method or area-by-area line scan sampling, the data reception quality at the receiving device 150 may deteriorate significantly.

[0634] In this embodiment, an example configuration of a receiving device 150 that overcomes this problem will be described.

[0635] Figure 53 shows a transmission device 100 as an example of a data transmission device configuration. Since Figure 53 has already been explained, its explanation will be omitted here.

[0636] Figure 64 shows the configuration of the receiving device 150 that receives the optically modulated signal transmitted by the transmitting device 100 in Figure 53.

[0637] Furthermore, Figure 54 shows the transmitting device 100, which has a different configuration from the transmitting device shown in Figure 53. Note that Figure 54 has already been explained, so its explanation will be omitted here.

[0638] Figure 65 shows the configuration of the receiving device 150 that receives the optically modulated signal transmitted by the transmitting device 100 in Figure 54.

[0639] The following section will describe the receiving device 150 shown in Figures 64 and 65.

[0640] Figure 64 shows an example of the configuration of a receiving device 150 that receives an optically modulated signal transmitted by the transmitting device 100 in Figure 53. Components that operate similarly to those in Figure 53 are given the same numbers.

[0641] Lens (group) A3101 receives the lens control signal A3109 as input and controls the focal length, aperture, focus, etc.

[0642] The image sensor (light receiving unit) A3103 receives light A3102 after it has passed through the lens as input and outputs light reception signals A2052_1 to A2502_M and image signal A3104. The image signal A3104 may then be processed and displayed as an image on an internal display unit, or it may be displayed as an image on an external display unit via an interface.

[0643] The data acquisition unit A2055 takes received data A2054_1 to A2054_M as input and outputs data A2056 and reception status information A3107.

[0644] The reception status information A3107 may, for example, be "information regarding the number of optically modulated signals being transmitted" obtained from "symbol A2403 containing information regarding the number of optically modulated signals being transmitted" transmitted by the transmitting device 100 in Embodiment 10, or "information regarding the number of optically modulated signals" obtained from "symbol A2501 containing information regarding the number of optically modulated signals" transmitted by the transmitting device 100. Alternatively, the reception status information A3107 may be reception status information generated from "information regarding the number of optically modulated signals being transmitted" and "information regarding the number of optically modulated signals." Note that this is not the only example.

[0645] The object recognition unit A3105 takes the image signal A3104, reception status information A3107, and instruction signal A3150 as inputs and performs object recognition based on the instruction signal A3150. For example, if instruction signal A3150 indicates "communicate," the object recognition unit A3105 will start recognizing the optical modulation signal. At this time, the object recognition unit A3105 takes the image signal A3104 and reception status information A3107 as inputs and outputs the object recognition signal A3106. The specific operation will be explained later.

[0646] The lens control unit A3108 receives the object recognition signal A3106 as input, recognizes the reception status as shown in Figures 56 and 63, and "determines whether to perform lens control, or if so, the set value for focal length, aperture, and focus," and outputs a lens control signal A3109 corresponding to these controls. In Figure 64, the lens control unit A3108 receives the object recognition signal A3106 as input, but other input signals may also be present.

[0647] Figure 65 shows an example of the configuration of a receiving device 150 that receives an optical modulation signal transmitted by the transmitting device 100 in Figure 54. Components that operate similarly to those in Figures 53 and 54 are given the same numbers. The operation of the lens (group) A3101, image sensor A3103, object recognition unit A3105, and lens control unit A3108 has already been explained, so the explanation is omitted here.

[0648] The error correction and decoding unit A2155 takes received data A2054_1 to A2054_M as input and outputs data A2056 and reception status information A3107.

[0649] Next, we will describe a specific example of how to control lens (group) A3101 in Figures 64 and 65.

[0650] As described in Embodiment 10, for example, if the receiving state of the receiving device 150 is as shown in Figure 56, the light receiving unit does not receive light from several light sources, making it difficult for the receiving device 150 to correctly receive data. Also, as already explained, if the receiving state of the receiving device 150 is as shown in Figure 63, there is a problem with the poor data reception quality of the receiving device 150.

[0651] On the other hand, when the receiving device 150 is in the reception state shown in Figures 59 and 60, the data reception quality is high.

[0652] From the above, the receiving device 150 improves the data reception quality by controlling the lens (group) A3101 to achieve the reception state shown in Figures 59 and 60. The receiving device 150 in Figures 64 and 65 is an example of a configuration to achieve this.

[0653] A specific example of the control of the receiving device 150 shown in Figures 64 and 65 will be described.

[0654] Let's assume that the receiving device 150 is in the state shown in Figure 56, for example. In this case, the receiving state information A3107 in Figures 64 and 65 is information created based on "information regarding the number of optically modulated signals being transmitted" and "information regarding the number of optically modulated signals," as explained earlier. Therefore, the object recognition unit A3105 in Figures 64 and 65 recognizes that 3 of the 16 optically modulated signals have been received.

[0655] Furthermore, the object recognition unit A3105 recognizes from the image signal A3104 the "reception status of the optical modulation signal, for example, at which position on the image sensor the three optical modulation signals are being received." In other words, the object recognition unit A3105 performs object recognition on the image in Figure 56. The object recognition unit A3105 then recognizes the "reception status of the optical modulation signal" and that "16 optical modulation signals have not been received." In this example, based on these recognition results, the object recognition unit A3105 decides to perform lens control and determines "optimal focal length settings, optimal aperture settings, and optimal focus settings" to achieve optimal communication, and outputs an object recognition signal A3106 containing this information. Note that the object recognition signal A3106 only needs to include "optimal focal length settings," and does not need to include information on optimal aperture settings and optimal focus settings.

[0656] The lens control unit A3108 receives the object recognition signal A3106 as input and outputs a lens control signal A3109 for controlling the lens (group) A3101 based on information contained in the object recognition signal A3106, such as "optimal focal length setting value, optimal aperture setting value, and optimal focus setting."

[0657] By performing this series of operations, the receiving device 150 in Figures 64 and 65 will enter a receiving state as shown in Figures 59 and 60, for example, which will result in the effect of obtaining high data reception quality.

[0658] In the example described above, the receiving state of the receiving device 150 was explained using the case where it is controlled from Figure 56 to Figures 59 and 60. However, this is not the only example; the receiving state of the receiving device 150 may also be controlled from Figure 63 to Figures 59 and 60.

[0659] Next, we will describe an example of the control of the receiving device 150 shown in Figures 66 and 67, which is different from Figures 64 and 65.

[0660] Figure 66 shows an example of the configuration of a receiving device 150 that receives an optically modulated signal transmitted by the transmitting device 100 in Figure 53. Parts that operate similarly to those in Figure 64 are given the same numbers, and parts that have already been explained are omitted from the explanation.

[0661] The difference between the receiving device 150 in Figure 66 and the receiving device 150 in Figure 64 is that the signal processing unit A3302 is located after the image sensor A3103.

[0662] The signal processing unit A3302 shall have at least a zoom (image enlargement / reduction) processing function.

[0663] Therefore, the signal processing unit A3302 receives the image signal A3301, the zoom signal A3300, the object recognition signal A3106, and the instruction signal A3150 as inputs. If the instruction signal A3150 indicates "shooting mode (take a picture)", the signal processing unit A3302 performs zoom signal processing on the image signal A3301 based on the zoom (image enlargement / reduction) information of the zoom signal A3300, and outputs the processed image signal A3104.

[0664] If instruction signal A3150 indicates "communication mode (to perform communication)," signal processing unit A3302 performs zoom signal processing on image signal A3301 based on information such as "suitable focal length setting, suitable aperture setting, and suitable focus setting" included in object recognition signal A3106, and outputs the processed image signal A3104 and the processed optical reception signals 2052_1 to A2052_M. As a result, as explained above, the reception state is improved, and thus the quality of data reception is improved.

[0665] Since the method for improving the reception status in the lens control unit A3108 has already been explained, the explanation will be omitted here.

[0666] As described above, the receiving device 150 can improve its reception status, thereby achieving the effect of improved data reception quality. In Figure 66, if the lens (group) A3101 does not have a focal length changing function, the focal length will not be changed to improve reception.

[0667] Figure 67 shows an example of the configuration of a receiving device 150 that receives an optically modulated signal transmitted by the transmitting device 100 in Figure 54. Parts that operate similarly to those in Figure 65 are given the same numbers, and parts that have already been explained are omitted from the explanation.

[0668] The difference between the receiving device 150 in Figure 67 and the receiving device 150 in Figure 65 is that, as in Figure 66, the signal processing unit A3302 is located after the image sensor A3103.

[0669] The operation of the signal processing unit A3302 has already been explained, so we will omit the explanation here. As explained previously, the reception condition is improved, resulting in an improvement in the quality of data reception.

[0670] Since the method for improving the reception status in the lens control unit A3108 has already been explained, the explanation will be omitted here.

[0671] By doing so, the receiving device 150 can improve its reception status, thereby achieving the effect of improved data reception quality. In Figure 67, if the lens (group) A3101 does not have a focal length changing function, the focal length will not be changed to improve reception.

[0672] By the way, in the receiving device 150 shown in Figures 64, 65, 66, and 67, the lens (group) A3101 is assumed to be capable of setting multiple values ​​for its focal length. For example, it is possible to set the focal length to be between 12mm and 35mm, or to set it to 12mm and 25mm. The following explanation will be based on this example.

[0673] As a first example, consider the case where multiple discrete values ​​are supported for the focal length.

[0674] The receiver 150 shown in Figures 64, 65, 66, and 67 will start communication when set to "communication mode" by instruction signal A3150. At this time, it is preferable to set the focal length of lens (group) A3101 to, for example, the widest angle, which is 12mm. This is because setting it to the widest angle makes it highly likely that reception conditions where reception of some optical modulations is difficult, as shown in Figure 56, can be avoided. This has the effect of improving the quality of data reception. However, to further improve the quality of data reception, the focal length and other parameters may be controlled to suitable values.

[0675] In this example, we explain the case where 12mm and 25mm focal lengths are supported. However, even if more than one focal length is supported, setting the focal length to, for example, the widest angle at the start of communication is an effective method for improving the quality of data reception.

[0676] As a second example, consider the case where the focal length can be set continuously (or finely).

[0677] The receiver 150 in Figures 64, 65, 66, and 67 will start communication when set to "communication mode" by instruction signal A3150. At this time, it is preferable to set the focal length of lens (group) A3101 to, for example, the widest angle, which is 12mm. This is because setting it to the widest angle makes it highly likely that reception conditions where reception of some optical modulations is difficult, as shown in Figure 56, can be avoided. This has the effect of improving the quality of data reception. However, in this example, it is possible to set the focal length more precisely, so it is highly likely that a similar effect can be obtained even if it is set to, for example, 14mm. However, in order to further improve the quality of data reception, the focal length and other parameters may be controlled to a suitable value.

[0678] Let's consider the case where the receiving device 150 in Figures 66 and 67 has a zoom (image enlargement / reduction) processing function. In this case, we will explain using the example of a case that supports 1x image enlargement (no enlargement), 2x image enlargement, and 4x image enlargement.

[0679] When the receiver 150 in Figures 66 and 67 is set to "communication mode" by instruction signal A3150, it will start communicating. At this time, it is recommended to set the zoom (image enlargement / reduction) of the signal processing unit A3302 to the widest angle, "1x image enlargement (no enlargement)". This is because setting it to the widest angle makes it highly likely that the reception condition in which some optical modulation is difficult to receive, as shown in Figure 56, can be avoided. This has the effect of improving the quality of data reception. However, to further improve the quality of data reception, the zoom value may be controlled to a suitable value.

[0680] (Supplement 1) Naturally, multiple embodiments and other elements described herein may be combined and implemented.

[0681] Furthermore, each embodiment is merely an example, and even if "modulation method, error correction coding method (error correction code used, code length, coding rate, etc.), control information, etc." are given as examples, it is possible to implement the same configuration even if a different "modulation method, error correction coding method (error correction code used, code length, coding rate, etc.), control information, etc." is applied.

[0682] Regarding the modulation scheme, it is possible to implement the embodiments and other details described herein even if a modulation scheme other than those described herein is used. For example, APSK (Amplitude Phase Shift Keying) (e.g., 16APSK, 64APSK, 128APSK, 256APSK, 1024APSK, 4096APSK, etc.), PAM (Pulse Amplitude Modulation) (e.g., 4PAM, 8PAM, 16PAM, 64PAM, 128PAM, 256PAM, 1024PAM, 4096PAM, etc.), PSK (Phase Shift Keying) (e.g., BPSK, QPSK, 8PSK, 16PSK, 64PSK, 128PSK, 256PSK, 1024PSK, 4096PSK, etc.), QAM (Quadrature Amplitude Modulation) (e.g., 4QAM, 8QAM, 16QAM, 64QAM, 128QAM, Modulation schemes such as 256QAM, 1024QAM, and 4096QAM may be applied, and uniform or non-uniform mapping may be used for each modulation scheme. Furthermore, the arrangement of 2, 4, 8, 16, 64, 128, 256, and 1024 signal points in the IQ plane (modulation schemes with 2, 4, 8, 16, 64, 128, 256, and 1024 signal points) is not limited to the signal point arrangement methods of the modulation schemes shown in this specification.

[0683] Examples of devices equipped with the wireless equipment described herein include communication and broadcasting equipment such as broadcasting stations, base stations, access points, terminals, and mobile phones, as well as communication equipment such as televisions, radios, terminals, personal computers, mobile phones, access points, and base stations. Furthermore, the wireless equipment described herein may be a device having communication functions that can be connected via some interface to devices for running applications such as televisions, radios, personal computers, and mobile phones.

[0684] Furthermore, the receiving unit described in this specification may be found in, for example, communication and broadcasting equipment such as broadcasting stations, base stations, access points, terminals, and mobile phones, as well as communication equipment such as televisions, radios, terminals, personal computers, mobile phones, access points, and base stations.

[0685] In the radio wave wireless communication of this embodiment, symbols other than data symbols, such as pilot symbols (preamble, unique word, postamble, reference symbol, etc.) and symbols for control information, may be arranged in any way within the frame. Here, we refer to them as pilot symbols and symbols for control information, but any naming convention is acceptable, and the role of each symbol is important.

[0686] The pilot symbol can be any known symbol modulated using PSK modulation in the transceiver (or the receiver may know the symbol transmitted by the transmitter by synchronizing with it). The receiver will use this symbol to perform frequency synchronization, time synchronization, channel estimation (CSI (Channel State Information) estimation) (for each modulated signal), signal detection, etc.

[0687] Furthermore, symbols for control information are used to transmit information that needs to be sent to the communication partner in order to enable communication other than data (such as applications), such as the modulation scheme, error correction coding scheme, coding rate of the error correction coding scheme, and settings information at higher layers.

[0688] (Supplement 2) The video coding schemes described in each of the above embodiments may be those conforming to specifications defined by names such as MPEG (Moving Picture Experts Group) 2, H.264 / AVC (Advanced Video Coding), H.265 / HEVC (High Efficiency Video Coding), VC-1, VP8, and VP9. However, the video coding schemes described in each of the above embodiments may be different from those listed above.

[0689] This disclosure is not limited to the embodiments described herein and can be implemented with various modifications. For example, while each embodiment describes the case where the communication is performed as a communication device, it is not limited to this, and this communication method can be implemented using software, hardware, or software linked to hardware.

[0690] Alternatively, for example, a program that performs the above-mentioned communication method, transmission method, or reception method may be stored in ROM (Read Only Memory) beforehand, and that program may be run by the CPU (Central Processor Unit).

[0691] Alternatively, a program that performs the above-mentioned communication method, transmission method, or reception method may be stored in a computer-readable storage medium, and the program stored in the storage medium may be recorded in the computer's RAM (Random Access Memory) so that the computer operates according to that program.

[0692] Furthermore, each functional block used in the description of each embodiment above may be implemented partially or entirely as an integrated circuit, or LSI (Large Scale Integration), and each process described in each embodiment above may be controlled partially or entirely by a single LSI or a combination of LSIs. An LSI may consist of individual chips, or it may consist of a single chip that includes some or all of the functional blocks. An LSI may have data inputs and outputs. Depending on the degree of integration, LSIs may also be called ICs (Integrated Circuits), system LSIs, super LSIs, or ultra LSIs. The method of integrated circuit implementation is not limited to LSIs, and may also be implemented with dedicated circuits, general-purpose processors, or dedicated processors. In addition, a Field Programmable Gate Array (FPGA) that can be programmed after LSI manufacturing, or a reconfigurable processor that can reconfigure the connections and settings of circuit cells inside the LSI, may be used. This disclosure may be implemented as digital processing or analog processing. Furthermore, if an integrated circuit implementation technology that replaces LSIs emerges due to advances in semiconductor technology or other derived technologies, it is of course possible to integrate functional blocks using that technology. The application of biotechnology is a possible possibility.

[0693] (Supplement 3) Furthermore, at least one of the FPGA (Field Programmable Gate Array) and CPU (Central Processing Unit) may be configured to download all or part of the software necessary to implement the communication method, transmission method, or reception method described in this disclosure via wireless or wired communication. In addition, it may be configured to download all or part of the software for updates via wireless or wired communication. The downloaded software may then be stored in a memory unit, and the FPGA and at least one of the CPU may be operated based on the stored software to perform the digital signal processing described in this disclosure.

[0694] In this case, the device comprising at least one of the FPGA and CPU may be connected to a communication modem wirelessly or via a wired connection, and the communication method, transmission method, or reception method described in this disclosure may be implemented using this device and the communication modem.

[0695] For example, a communication device (transmitter or receiver) such as a base station, AP, or terminal described herein may include at least one of an FPGA and a CPU, and the communication device may also include an interface for obtaining software from an external source to operate at least one of the FPGA and CPU. Furthermore, the communication device may include a storage unit for storing the software obtained from an external source, and the signal processing described herein may be realized by operating the FPGA and CPU based on the stored software.

[0696] A first "vehicle or vehicle" may be equipped with the transmitting device described herein, and a second "vehicle or vehicle" may be equipped with the receiving device described herein, and data transmission and reception may be performed.

[0697] The "transmitting device, or part of the functions of the transmitting device" described herein may be connected to a first "vehicle or vehicle" via an interface, and the "receiving device, or part of the receiving device" described herein may be connected to a second "vehicle or vehicle" via an interface, thereby performing data transmission by sending and receiving.

[0698] Furthermore, the first "vehicle or vehicle" may be equipped with the transmitting device described herein, and data transmission and reception may be performed between this transmitting device and the receiving device described herein.

[0699] A second "vehicle or vehicle" may be equipped with the receiving device described herein, and data transmission and reception may be performed between this receiving device and the transmitting device described herein.

[0700] Furthermore, the "transmitting device, or part of the functions of the transmitting device" described herein may be connected to a first "vehicle or vehicle" via an interface, and data transmission and reception may be performed between this series of transmitting devices and the receiving device described herein.

[0701] The “receiving device, or part of a receiving device” described herein may be connected to a second “vehicle, or vehicle” via an interface, and data transmission and reception may be performed between the transmitting device and this set of receiving devices described herein.

[0702] If the “vehicle or vehicle” is equipped with the transmitting device or a part of the transmitting device described herein, or if the “vehicle or vehicle” is connected via an interface to the “transmitting device described herein” or a part of the function of the transmitting device described herein, then the light source provided by the “vehicle or vehicle” may be used as the light source provided by the transmitting device described herein.

[0703] For example, as shown in Figure 68, vehicle B100 is equipped with light sources B101_1, B101_2, B101_3, and B101_4, and one or more of these light sources may be used as light sources for the transmitting device described herein to transmit optically modulated signals.

[0704] Furthermore, the transmitter, or a device connected to the transmitter, may have a function to select "which of the multiple light sources mounted on vehicle B100 will be used as the light source for the transmitter described herein to transmit the optical modulation signal." The brightness, illumination angle, and position of the light source may also be adjustable.

[0705] If the "vehicle or vehicle" is equipped with a receiving device or a part of a receiving device as described herein, or if the "vehicle or vehicle" is connected via an interface to the "vehicle or vehicle" or a part of the function of a receiving device as described herein, then a light-receiving part (e.g., an image sensor, a photodiode, etc.) provided by the "vehicle or vehicle" may be used as the light-receiving part provided by the receiving device as described herein.

[0706] For example, as shown in Figure 69, the vehicle B100 is equipped with light-receiving units B201_1, B201_2, B201_3, B201_4, B201_5, and B201_6, and one or more of these light-receiving units may be used as light-receiving units for the receiving device described herein to receive optically modulated signals.

[0707] Furthermore, the receiving device, or a device connected to the receiving device, may be equipped with a function to select "which of the multiple light-receiving units mounted on vehicle B100 will be used by the receiving device described herein as the light-receiving unit for receiving the optical modulation signal." The angle and position of the light-receiving unit may also be adjustable.

[0708] Furthermore, the receiving device described herein may indicate on the front panel of the vehicle or the cockpit of the vehicle that it is able to receive data. Alternatively, the receiving device described herein may indicate to the user that it is able to receive data by vibrating the steering wheel of the vehicle or a vibrator attached to the steering wheel.

[0709] (Supplement 4) In this specification, a server may provide an application relating to processing of a receiving device, and a terminal may implement the functions of the receiving device described herein by installing this application. The application may also be provided to the terminal by a communication device equipped with the transmitting device described herein connecting to the server via a network, or by a communication device having a different transmitting function connecting to the server via a network.

[0710] Similarly, in this specification, a server may provide an application related to processing of a transmitting device, and a communication device may implement the functions of the transmitting device described herein by installing this application. It is conceivable that the application may be provided to the communication device by another communication device connecting to the server via a network.

[0711] Alternatively, the server may provide software relating to the light source of the transmitting device and the light-receiving unit of the receiving device. By obtaining this software, the light source of the transmitting device can respond to the transmission of optically modulated signals, and the light-receiving unit of the receiving device can respond to the reception of optically modulated signals.

[0712] Furthermore, the transmitting device in this specification may also have server functionality, and the applications provided by the transmitting device may be provided to a communication device using some means of communication, and the communication device may implement the receiving device in this specification using the applications obtained by downloading.

[0713] In this specification, the terms "illumination unit" and "light source" are used, but it is also possible that a display or projector that shows images, videos, advertisements, etc., emits light, and that light contains an optical modulation signal. In other words, the "illumination unit" and "light source" may have functions other than emitting light. Furthermore, the "illumination unit" and "light source" may be composed of multiple "illumination" and "light sources".

[0714] Furthermore, the transmission method used by a communication device that generates an optically modulated signal and emits light may be a transmission method other than those described herein. Also, the optically modulated signal may contain information other than that described herein.

[0715] Furthermore, the lighting or light source itself, such as an LED, may have the functions of the transmitting device described herein.

[0716] Furthermore, although this specification uses the example of mounting the transmitter and receiver in a vehicle, it is not limited to this. The transmitter and receiver may be mounted in other devices, or they may exist as standalone units. In such cases, the operations described herein can be performed, and similar effects can be obtained.

[0717] (Supplement 5) The communication device and receiving device in this disclosure may be any of the embodiments 1 to 11.

[0718] In other words, a first communication device, which is one aspect of the present disclosure, includes: a light receiving unit that receives a first optical signal that transmits first identifier information indicating an identifier of a first communication device and a second optical signal that transmits second identifier information indicating an identifier of a second communication device, and generates a received signal; a demodulation unit that demodulates the received signal to obtain the first identifier information and the second identifier information; a camera that photographs a region including the first optical signal and the second optical signal and acquires video or still image data; a control unit that selects either the first identifier information or the second identifier information based on the video or still image data; and a communication unit that communicates with a communication device corresponding to the selected identifier information.

[0719] A second communication device, in one aspect of the present disclosure, comprises: a receiving signal for photographing a predetermined area and demodulating an optical signal irradiated onto the predetermined area; a light receiving unit for acquiring video or still image data for use in image processing; a demodulation unit for demodulating the image data and acquiring a plurality of identifiers indicating identifiers of other communication devices corresponding to each of them; a control unit for selecting one of the plurality of identifiers based on the video or still image data; and a communication unit for wireless communication with the other communication device corresponding to the selected identifier.

[0720] A first receiving device, in one aspect of the present disclosure, includes: a first light receiving unit that receives a first optical signal transmitting first identifier information indicating an identifier of a first communication device and a second optical signal transmitting second identifier information indicating an identifier of a second communication device to generate an optical receiving signal; a demodulation unit that demodulates the optical receiving signal to acquire the first identifier information and the second identifier information; a second light receiving unit that acquires video or still image data of a region including the first optical signal and the second optical signal; and a control unit that selects either the first identifier information or the second identifier information based on the video or still image data.

[0721] A second receiving device, in one aspect of the present disclosure, includes: a light receiving unit that receives a first optical signal transmitting first identifier information indicating an identifier of a first communication device and a second optical signal transmitting second identifier information indicating an identifier of a second communication device and generates a received signal; a demodulation unit that demodulates the received signal to acquire the first identifier information and the second identifier information; a camera that photographs a region including the first optical signal and the second optical signal and acquires video data or still image data; and an analysis unit that analyzes the video data or still image data and generates relative position information indicating the positional relationship between a first transmitter that transmitted the first optical signal and a second transmitter that transmitted the second optical signal.

[0722] A third receiving device, in one aspect of the present disclosure, comprises a light receiving unit that receives a first optical signal that transmits first identifier information indicating the identifier of a first communication device, a second optical signal that transmits second identifier information indicating the identifier of a second communication device, and an image sensor to generate a received signal; a demodulation unit that demodulates the received signal to acquire the first identifier information and the second identifier information; and an analysis unit that generates first position information indicating the position of a first transmitter that transmitted the first optical signal and second position information indicating the position of a second transmitter that transmitted the second optical signal.

[0723] A fourth receiving device, which is one aspect of the present disclosure, comprises: a receiving signal for photographing a predetermined area and demodulating an optical signal irradiated onto the predetermined area; a light receiving unit for acquiring video or still image data for use in image processing; a demodulation unit for demodulating the received signal and generating demodulated data; and an analysis unit for analyzing the video or still image data and generating attribute information indicating the attributes of the transmitter that transmitted the optical signal corresponding to the demodulated data.

[0724] Furthermore, the receiving device in this disclosure may be in the form of Embodiments 8 to 11.

[0725] In other words, a receiving device according to one aspect of the present disclosure includes an image sensor that acquires an image by capturing an image, and a receiving unit that receives N different optical signals transmitted from multiple light sources in parallel by sampling a plurality of pixels in each of the N (where N is an integer of 2 or more) regions included in the imaging surface of the image sensor. For example, as shown in Figure 42, the receiving device receives different optical signals in parallel from light sources corresponding to each of the regions A, B, C, and D by performing line scan sampling.

[0726] This allows the receiving device to securely obtain information such as the SSID by receiving optical signals. Furthermore, because it receives different optical signals transmitted from multiple light sources in parallel, it is possible to improve the data transmission speed.

[0727] Furthermore, the receiving device further comprises at least one lens and a lens control unit that controls the at least one lens, and the lens control unit may control the at least one lens so that light from each of the plurality of light sources is projected onto the image sensor through the at least one lens. For example, the lens control unit may control the focal length of the at least one lens. Specifically, the at least one lens is, for example, the lens (group) A3101 shown in Figures 64 to 67, and the lens control unit is, for example, the lens control unit A3108 shown in Figures 64 to 67. Also, by controlling the focal length by the lens control unit, the receiving state shown in Figures 56 and 63 is changed to, for example, the receiving state shown in Figures 59 and 60. Note that not only the focal length but also the aperture and focus may be controlled.

[0728] This results in the ability to obtain high-quality data reception.

[0729] Furthermore, the optical signals transmitted from each of the plurality of light sources include signal count information relating to the number of optical signals transmitted from the plurality of light sources, and the receiving device further includes a recognition unit that recognizes the reception state of the N optical signals, and the recognition unit recognizes the reception state based on the number of optical signals N received by the receiving unit and the signal count information included in the optical signals received by the receiving unit, and the lens control unit may control the focal length of the at least one lens based on the reception state recognized by the recognition unit. For example, the recognition unit determines whether the reception state is one in which all optical signals transmitted from the plurality of light sources are received by the receiving unit, based on the number of optical signals N received by the receiving unit and the number of optical signals indicated by the signal count information, and if the recognition unit determines that not all optical signals are received by the receiving unit, the lens control unit may control the at least one lens so that its focal length is shortened. Specifically, the signal count information is, for example, the information contained in "Symbol A2403, which contains information about the number of optically modulated signals being transmitted," as shown in Figures 57 and 58. The recognition unit is the object recognition unit A3105, as shown in Figures 64 to 67.

[0730] This allows the system to determine whether all optical signals transmitted from multiple light sources are being received, based on the number of received optical signals (N) and the number of optical signals indicated by the signal count information. If not all optical signals are being received, the focal length of at least one lens is shortened. As a result, the field of view widens, allowing all light from multiple light sources to be projected onto the image sensor and all optical signals to be received. Therefore, high data reception quality can be obtained. [Industrial applicability]

[0731] One aspect of this disclosure is useful for optical communication systems. [Explanation of Symbols]

[0732] 100,400,1000,1400A,1400B equipment 102, 1404-1, 1404-2 Transmitter 104,1406-1,1406-2 Light source 150,1050 terminals (receiving devices) 151 Light receiving part 153 Receiving Unit 155 Data Analysis Department 157 Display section 453,2002 Radio equipment 470,2000 base stations 2001 Transmitter

Claims

1. One or more image sensors that acquire image data and optical signals, Equipped with a processor, The aforementioned processor, By performing image processing on the aforementioned image data, an object equipped with the light source that transmitted the optical signal is detected. Demodulated data is obtained by demodulating the aforementioned optical signal. The demodulated data is stored in memory in association with the detected object. Receiving device.

2. The demodulated data includes connection information for connecting to the object via wireless communication. The receiving device according to claim 1.

3. A receiving method performed by a receiving device equipped with one or more image sensors, Image data and optical signals are acquired by the one or more image sensors described above. By performing image processing on the aforementioned image data, an object equipped with the light source that transmitted the optical signal is detected. Demodulated data is obtained by demodulating the aforementioned optical signal. The demodulated data is stored in memory in association with the detected object. Reception method.

4. The demodulated data includes connection information for connecting to the object via wireless communication. The receiving method according to claim 3.

Images