Communication method, communication system, transmitter, receiver, transmission control program, and reception control program

Abstract

To provide a technique that can ensure real-time performance by performing multiple communications substantially simultaneously in UWB communication.SOLUTION: An exemplary communication method is a communication method using UWB communication, in which multiple pieces of information are transmitted from multiple transmitters at partially overlapping timing while shifting the transmission start timing of each piece, and each receiver corresponding to each of the multiple transmitters starts receiving in accordance with the shifted transmission start timing and receives the information.SELECTED DRAWING: Figure 9B

Description

[Technical Field]

[0001] The present invention relates to a communication technology using wireless communication. [Background technology]

[0002] In recent years, wireless communication has been on the rise in the field of communications due to its advantages in terms of installation, such as the elimination of wiring. One type of wireless communication that is on the rise is known as UWB (Ultra Wide Band) communication, which uses radio waves in the 8 GHz band (see, for example, Patent Document 1).

[0003] UWB communication has the advantages of low interference with radio waves used in Wi-Fi (registered trademark) and mobile devices such as smartphones, and good transmission due to its wide bandwidth of 500 MHz. UWB communication also has the advantage of being easily established in vehicles, which are confined spaces made of metal and have many wires. For these reasons, UWB communication has attracted attention as a communication method advantageous for use inside vehicles and outdoors. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2016-38332 Summary of the Invention [Problem to be solved by the invention]

[0005] However, although this differs from country to country, the number of frequency channels permitted for outdoor use in UWB communications is sometimes limited. For example, in Japan, only one frequency channel is permitted for outdoor use. When the number of frequency channels permitted for use is limited, it is difficult to conduct multiple communications simultaneously due to the problem of radio wave interference between UWB communications.

[0006] If multiple communications cannot be performed simultaneously, information cannot be sent from one device to multiple devices at the same time, which can cause delays on the receiving side and impair real-time performance.Furthermore, if multiple communications cannot be performed simultaneously, techniques such as dividing information and sending it in parallel to efficiently transmit it cannot be used, which can cause the communication speed to be unable to keep up with the processing speed on the receiving side, impairing real-time performance.

[0007] In view of the above, an object of the present invention is to provide a technique that can perform a plurality of communications substantially simultaneously in UWB communications, thereby ensuring real-time performance. [Means for solving the problem]

[0008] An exemplary communication method of the present invention is a communication method using UWB communication, in which multiple pieces of information are transmitted from multiple transmitters at partially overlapping times while shifting the transmission start timing of each piece, and each receiver corresponding to each of the multiple transmitters starts receiving in accordance with the shifted transmission start timing and receives the information. [Effects of the Invention]

[0009] In the exemplary embodiment of the present invention, a plurality of pieces of information are transmitted from a plurality of transmitters with their transmission start timings shifted from one another, and each receiver starts receiving the information in accordance with the shifted transmission start timings. This allows each receiver to properly receive information from its associated transmitter without being affected by transmission waves from other transmitters. Taking advantage of this feature, the exemplary embodiment of the present invention allows a plurality of transmitters to transmit information at partially overlapping timings. By increasing the amount of overlap in the transmission timings, the timings at which each transmitted wave is received by each receiver can be made very close. Because the reception timings of each receiver can be made very close, for example, the timing of the information received by each receiver can be aligned with a short timing adjustment, thereby ensuring real-time performance. Furthermore, because the reception timings of each receiver can be made very close, for example, the information received by each receiver can be easily connected continuously by timing adjustment, thereby ensuring real-time performance. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a block diagram showing a schematic configuration of a communication system according to a first embodiment. [Figure 2] FIG. 1 shows a frame format used in UWB communication. [Figure 3] Schematic diagram showing an overview of radio interference countermeasures in communication systems [Figure 4] FIG. 10 is a schematic diagram illustrating a detailed example of how to set the reception mode start time τstart. [Figure 5] A block diagram showing a schematic configuration of a transmitter provided in a communication system. [Figure 6] 1 is a flowchart showing an example of the operation of a transmitter; [Figure 7] A block diagram showing a schematic configuration of a receiver included in a communication system. [Figure 8] Flowchart showing an example of the operation of a receiver [Figure 9A]A diagram showing the process from encoding to decoding an audio signal [Figure 9B] 1 is a time chart illustrating the operation of a communication system; [Figure 10] 10 is a time chart illustrating an operation of a communication system according to a first modification of the first embodiment; [Figure 11] FIG. 10 is a schematic diagram showing an arrangement of four speakers in a vehicle included in a communication system according to a first modified example of the first embodiment; [Figure 12] FIG. 10 is a block diagram showing a schematic configuration of a communication system according to a second modification of the first embodiment. [Figure 13] FIG. 10 is a block diagram showing a schematic configuration of a transmitter included in a communication system according to a third modification of the first embodiment. [Figure 14] FIG. 10 is a block diagram showing the configuration of a communication system according to a second embodiment. [Figure 15] FIG. 10 is a diagram for explaining a method of transmitting and receiving data between a video playback device and a second display device. [Figure 16] 10 is a time chart illustrating the operation of the communication system according to the second embodiment; [Figure 17] FIG. 1 shows a comparative example DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. In the description of the embodiments, the same components are denoted by the same reference numerals, and redundant description will be omitted unless particularly necessary.

[0012] 1. First Embodiment First, a communication system 100 according to a first embodiment of the present invention will be described.

[0013] [1-1. Overview of the communication system] 1 is a block diagram showing a schematic configuration of a communication system 100 according to a first embodiment of the present invention. The communication system 100 performs UWB communication. UWB communication is wireless communication performed in accordance with a standard such as IEEE 802.15.4 (hereinafter sometimes simply referred to as a communication standard).

[0014] The communication system 100 is, for example, an in-vehicle system. However, the communication system 100 may be applied to a target other than a vehicle where communication equipment is installed. The communication system 100 may be, for example, a communication system for a mobile body other than a vehicle, a home communication system, etc. Note that the vehicle includes an automobile and a railroad car. Furthermore, the mobile body other than a vehicle includes, for example, a ship, an aircraft, etc.

[0015] 1, the communication system 100 includes an audio reproduction device 1, a transmitting amplifier 2, a transmitter 3, a receiver 4, a receiving amplifier 5, and a speaker 6. The communication system 100 is an audio communication system. However, this is merely an example, and the present invention can also be applied to communication systems for other purposes besides audio, such as video, or video and audio.

[0016] The sound reproducing device 1 reads and reproduces sound information from a recording medium such as an optical disc or a USB memory. The sound reproducing device 1 also receives and reproduces sound information from an external device connected via wired or wireless communication. The sound reproducing device 1 is included in, for example, an in-car audio device, a display audio device, or a navigation device.

[0017] The transmitting amplifier 2 is a preamplifier that amplifies the signal output from the sound reproducer 1. More specifically, there are multiple transmitting amplifiers 2, and the multiple transmitting amplifiers 2 are composed of a first transmitting amplifier 2a and a second transmitting amplifier 2b. The first transmitting amplifier 2a is a preamplifier for the left channel, and receives an audio signal for the left channel from the sound reproducer 1. The second transmitting amplifier 2b is a preamplifier for the right channel, and receives an audio signal for the right channel from the sound reproducer 1. In other words, the sound system formed by the communication system 100 is of stereo (2.0ch) specification. However, the sound system formed by the communication system 100 may also be of monaural specification or a multi-channel specification with three or more channels. Note that the monaural specification referred to here assumes a configuration in which the same sound is output from multiple speakers 6.

[0018] The transmitter 3 transmits information. The transmission of information by the transmitter 3 is performed in accordance with the UWB communication standard. As described above, since the communication system 100 is a stereo audio system, the communication system 100 includes a plurality of transmitters 3. Specifically, the plurality of transmitters 3 are composed of a first transmitter 3a and a second transmitter 3b. The first transmitter 3a is a transmitter for the left channel, and transmits information input from the transmitting-side first amplifier 2a. The second transmitter 3b is a transmitter for the right channel, and transmits information input from the transmitting-side second amplifier 2b. Note that if the audio system configured by the communication system 100 is a multi-channel system with three or more channels, the number of transmitters 3 may be three or more (basically the same number as the number of channels in the audio system).

[0019] The receiver 4 is provided corresponding to the transmitter 3, and communicates with the transmitter 3 in accordance with the UWB communication standard. The receiver 4 receives information transmitted by the transmitter 3. In detail, the communication system 100 includes a plurality of receivers 4 provided corresponding to the plurality of transmitters 3, respectively. The plurality of receivers 4 are composed of a first receiver 4a and a second receiver 4b. The first receiver 4a is a receiver for the left channel, and receives information transmitted from the first transmitter 3a. The second receiver 4b is a receiver for the right channel, and receives information transmitted from the second transmitter 3b.

[0020] The receiving amplifier 5 is a power amplifier that amplifies the signal output from the receiver 4. More specifically, there are multiple receiving amplifiers 5, and the multiple receiving amplifiers 5 are composed of a first receiving amplifier 5a and a second receiving amplifier 5b. The first receiving amplifier 5a is a power amplifier for the left channel, and receives as input the sound signal output from the first receiver 4a. The second receiving amplifier 5b is a power amplifier for the right channel, and receives as input the sound signal output from the second receiver 4b.

[0021] The speaker 6 emits sound information output from the sound reproduction device 1 toward the interior of the vehicle. Specifically, there are multiple speakers 6, each consisting of a first speaker 6a for the right channel and a second speaker 6b for the left channel. The first speaker 6a is located, for example, on the front right side of the vehicle interior and outputs sound corresponding to a signal input from the first receiving amplifier 5a. The second speaker 6b is located, for example, on the front left side of the vehicle interior and outputs sound corresponding to a signal input from the second receiving amplifier 5b.

[0022] In this embodiment, information from the sound reproduction device 1 is transmitted to the speaker 6 using wireless communication, which reduces the number of wire harnesses used in the vehicle. Furthermore, UWB communication is used for sound communication, which reduces the possibility of interference between sound transmission radio waves and radio waves used in mobile devices such as smartphones, thereby increasing the success rate of sound communication. Furthermore, the use of UWB communication makes it easier to establish sound communication even in a vehicle interior, which is a narrow metal space with many wires.

[0023] [1-2. Overview of UWB communication in communication systems] 2 is a diagram showing a frame format used in UWB communication. The frame format shown in Fig. 2 corresponds to the structure of one unit (communication frame) of transmission data in UWB communication.

[0024] The frame format used in UWB communication is determined by the above-mentioned communication standard. As shown in Figure 2, the frame format used in UWB communication has a structure in which a preamble is first followed by an SFD (Start Frame Delimiter), a PHR (PHY Header), and a data body. In other words, it can be said to be a preamble-based UWB communication. The term "data body" is used to make it easier to understand the difference between the preamble, SFD, and PHR.

[0025] A preamble is a sequence of bits or pulses (e.g., -, 0, +) that is sent before the data itself in digital communications to inform the receiving end that data is about to be sent. The receiving end uses the preamble signal to synchronize the receiving clock.

[0026] There are multiple patterns in the preamble. The preamble code is a code for identifying these multiple patterns. Different preamble codes use different code symbols. Code symbols are composed of ternary symbols (for example, -, 0, +). One code symbol (1 symbol) is composed, for example, of "-+0++000-+-++00++0+00-0000-0+0-".

[0027] The SFD is a bit string with a specific pattern that signals the start of data in a communication frame. The PHR contains information necessary for decoding a packet. For example, the PHR contains information such as the address of the communication partner and the data length of the subsequent data. The data body is the main body of information to be sent to the communication partner and contains the actual data to be transmitted. In this embodiment, the data body contains sound data to be emitted from the speaker 6.

[0028] In UWB communication, although the strength of radio waves also has an effect, radio waves received earlier are generally processed with priority. For this reason, when the first transmitter 3a and the second transmitter 3b simultaneously transmit their transmission waves, it is possible that at least one of the first receiver 4a and the second receiver 4b will first receive the radio waves (interference waves) from the transmitter 3a or 3b that does not correspond to itself.

[0029] If receivers 4a and 4b receive a jamming signal first, they cannot recognize it as a jamming signal unless they demodulate the address in the PHR, which is processed after the preamble and SFD. Once they recognize it as a jamming signal, they stop processing the jamming signal and can start receiving other signals. However, if the target transmission signal reaches receivers 4a and 4b before the reception process identifies the radio wave as a jamming signal, they will miss receiving the target transmission signal.

[0030] In UWB communication, if different channels are available, the first transmitter 3a and the second transmitter 3b can use different channels to prevent the above-mentioned radio wave interference. However, in Japan, for example, there is only one frequency channel available for UWB communication outdoors. When there is only one frequency channel available for UWB communication, it is difficult for the first transmitter 3a and the second transmitter 3b to simultaneously transmit transmission waves due to the problem of radio wave interference.

[0031] Considering the above points, in communication system 100, transmitter 3 has delay unit 31 in addition to transmitting unit 32, and receiver 4 has adjustment unit 42 in addition to receiving unit 41 (see FIG. 1). Delay unit 31 is used to shift the transmission start timing between multiple transmitters 3, and adjustment unit 42 is used to restore the timing shifted by delay unit 31. These will be described in detail later.

[0032] However, simply shifting the transmission timing on the transmitting side does not completely solve the above-mentioned problem of radio wave interference. Taking this into consideration, the communication system 100 has implemented radio wave interference countermeasures as shown in Fig. 3. Fig. 3 is a schematic diagram showing an overview of the radio wave interference countermeasures in the communication system 100.

[0033] As shown in Fig. 3, the receiver 4 can switch between a reception mode and an idle mode. The receiver 4 can receive signals when in the reception mode, and cannot communicate when in the idle mode. In the idle mode, power is supplied to necessary circuits, etc., and the receiver 4 can immediately switch to the reception mode. In this embodiment, the transmitter 3 can also switch between a transmission mode and an idle mode, but the transmitter 3 may be in a transmission mode in which it can transmit at all times.

[0034] 3, τstart is the time when the receiver 4 starts receiving (reception mode start time), and τnext is the time when the target wave transmitted from the corresponding transmitter 3 is expected to be received (expected reception time), which is a time previously agreed upon between the transmitter 3 and the receiver 4.

[0035] The predetermined time may be shared between the transmitter 3 and the receiver 4 using a wired communication facility (not shown) included in the communication system 100. The wired communication facility may be, for example, a power line communication (PLC) facility that uses a power line to start the communication system 100. However, the wired communication used in the communication system 100 is not limited to PLC communication, and may be CAN (Registered Trademark, Controller Area Network) communication, LIN (Registered Trademark, Local Interconnect Network) communication, CXPI (Clock Extension Peripheral Interface) communication, or the like. In some cases, wireless communication (UWB communication) may be used instead of wired communication. In this case, the transmitter 3 functions as both a transmitter and a receiver, and the receiver 4 functions as both a receiver and a transmitter. When wireless timing is determined, the receiving side is in a constant receiving state (or a state close to it).

[0036] The reception mode start time τstart is set slightly before the expected reception time τnext. For example, the reception mode start time τstart is set relative to the expected reception time τnext, taking into consideration the length of time it takes for the receiving circuit to stabilize and enable good reception after the receiver 4 starts reception mode.

[0037] 3, the receiver 4 switches from idle mode to reception mode just before the expected reception time agreed upon with the transmitter 3. The receiver 4 then ends reception mode and switches to idle mode in synchronization with the end of the transmission wave from the transmitter 3. The receiver 4 ends reception mode at a pre-programmed timing based on the reception mode start time τstart.

[0038] With this configuration, the receiver 4 starts receiving in accordance with the transmission start timing of the target wave transmitted from the corresponding transmitter 3. As a result, it is possible to reduce the possibility that the receiver 4 will receive a transmission wave that arrives at a different timing from the target wave. In other words, by shifting the transmission timing of the first transmitter 3a and the second transmitter 3b, it is possible to increase the probability that the first receiver 4a will receive the transmission wave transmitted from the corresponding first transmitter 3a and the second receiver 4b will receive the transmission wave transmitted from the corresponding second transmitter 3b. It is preferable to start the reception mode as close as possible to the expected time of reception of the target wave. An example of this will be described below.

[0039] FIG. 4 is a schematic diagram for explaining a detailed example of how to set the reception mode start time τstart. In the communication standard for UWB communication, the transmission and reception times (times) can be obtained at the timing of the PHR. Taking this into consideration, as shown in FIG. 4, the expected reception time τnext is determined based on the PHR included in the frame format used in UWB communication. In detail, the expected reception time τnext is set to the start timing of the PHR.

[0040] In the example shown in FIG. 4, the reception mode start time τstart, which is the time immediately before the expected reception time τnext, is determined by the following equation (1). τstart = τnext -(tSFD +tsym × Nrg ) (1)

[0041] In equation (1), tSFD is the reception period (SFD time) of the SFD included in the frame format. tsym is the reception period (one symbol time) of one symbol of the preamble code in the preamble included in the frame format. As described above, one symbol of the preamble code refers to a sequence symbol formed using pulses of a predetermined pattern (e.g., -, 0, +). Nrg is the required number of times to recognize one symbol of the preamble code. The receiver 4 can receive the transmission data of UWB communication only after recognizing one symbol of the preamble code the required number of times Nrg.

[0042] The required number of recognition attempts Nrg is a predetermined number that depends on the device. In the example shown in FIG. 4, the required number of recognition attempts Nrg is, for example, four. The minimum recognition period for the preamble can be calculated by multiplying tsym by the device-dependent required number of recognition attempts Nrg. In this embodiment, the reception mode start time τstart is set to a time that is earlier than the expected reception time τnext by the period obtained by the calculation formula (tSFD + tsym × Nrg).

[0043] By determining the receive mode start time in this manner, the start of the period in which UWB communication transmission data can be received can be set as close as possible to the expected reception time. This reduces the possibility of being affected by interference from jamming waves and improves the success rate of communication. Note that the receive mode start time τstart may be set to a time earlier than the expected reception time τnext by the period (time) calculated using the formula (tSFD + tsym × Nrg), or by an appropriate margin time determined through experiments, etc.

[0044] [1-3.Detailed example] (1-3-1. Transmitter) Fig. 5 is a block diagram showing a schematic configuration of the transmitter 3 included in the communication system 100. Note that Fig. 5 shows components necessary for explaining the features of this embodiment, and omits a description of general components. The transmitter 3 is one of a plurality of transmitters used in a set, and more specifically, is a first transmitter 3a or a second transmitter 3b. That is, the first transmitter 3a and the second transmitter 3b have the same configuration.

[0045] As shown in Fig. 5, the transmitter 3 includes a controller 31 and a transmission unit 32. The controller 31 can be interpreted as the delay unit 31 shown in Fig. 1 (specifically, the first delay unit 31a or the second delay unit 31b), and is therefore given the same reference numeral as the delay unit 31. The transmission unit 32 is the same as the transmission unit 32 shown in Fig. 1, and specifically, is the first transmission unit 32a or the second transmission unit 32b.

[0046] The controller 31 is a computer device including a processor that performs arithmetic processing and the like. The processor may be configured to include, for example, a CPU (Central Processing Unit). The controller 31 may be configured with one processor or multiple processors. When configured with multiple processors, the processors only need to be connected to each other so that they can communicate with each other. The controller 31 also includes computer components such as memory (RAM, ROM, etc.) necessary for executing programs.

[0047] The controller 31 has, as its functions, a delay control unit 311 and a transmission control unit 312. Each of the functional units 311, 312 is realized, for example, by a processor executing arithmetic processing in accordance with one program. However, this configuration is not limited thereto, and each of the functional units 311, 312 may be realized, for example, by a processor executing arithmetic processing in accordance with a separate program for each functional unit.

[0048] As described above, each of the functional units 311 and 312 may be realized by causing a processor to execute a program, i.e., by software, but may also be realized by other methods. At least one of the functional units 311 and 312 may be realized using, for example, an ASIC (Application Specific Integrated Circuit) or an FPGA (Field Programmable Gate Array). That is, each of the functional units 311 and 312 may be realized by hardware using a dedicated IC or the like. Also, each of the functional units 311 and 312 may be realized by a combination of software and hardware. Also, each of the functional units 311 and 312 is a conceptual component. The function performed by one component may be distributed among multiple components. Also, the functions of multiple components may be integrated into one component.

[0049] The delay control unit 311 delays the transmission start timing of information input from the transmitting amplifier 2 to the transmitter 3 by a predetermined delay time. The delay control unit 311 manages this delay time. As described above, the transmission start timings of the first transmitter 3a and the second transmitter 3b are shifted so as not to cause radio wave interference. This shift in transmission start timing is achieved by a difference in delay time. In other words, the amount of time by which the transmission start timing is delayed by the delay control unit 311 differs between the first transmitter 3a and the second transmitter 3b. The shift in transmission start timing between the first transmitter 3a and the second transmitter 3b is made as small as possible within a range that does not cause radio wave interference.

[0050] The transmission control unit 312 controls the transmission unit 32. The transmission control unit 312 causes the transmission unit 32 to transmit information input from the transmission-side amplifier 2 to the transmitter 3 in accordance with the timing delayed by the delay control unit 311.

[0051] Under the control of the transmission control unit 312, the transmitter 32 transmits the information input from the transmitting amplifier 2 in a format conforming to the UWB communication standard. As described above, the delay times controlled by the controller 31 differ between the first transmitter 3a and the second transmitter 3b, so there is a difference in the transmission start timing between the first transmitter 32a of the first transmitter 3a and the second transmitter 32b of the second transmitter 3b. As described above, this difference in the transmission start timing is set as small as possible in this embodiment. For this reason, the transmission timing of the first transmitter 32a and the transmission timing of the second transmitter 32b partially overlap.

[0052] As can be seen from the above explanation, the controller 31 can be considered a delay unit that delays the timing at which input information starts to be transmitted. That is, the transmitter 3 includes the delay unit 31 that delays the timing at which input information starts to be transmitted. Furthermore, the transmitting unit 32 included in the transmitter 3 uses the delay provided by the delay unit 31 to transmit information at timings that partially overlap with the timing at which the transmission starts of the other transmitters are shifted relative to the other transmitters. In this configuration, by minimizing the shift in the timing at which the transmission starts of the multiple transmitters 3 are transmitted as much as possible, it is possible to achieve substantially simultaneous transmission with a large overlap in the transmission timings.

[0053] In this embodiment, when the transmitter 3 is the first transmitter 3a, the other transmitter is the second transmitter 3b. When the transmitter 3 is the second transmitter 3b, the other transmitter is the first transmitter 3a. The functions of the transmitter 3 described above can also be said to be functions obtained by causing a computer device included in the transmitter 3 to execute processing in accordance with a transmission control program stored in a memory provided in the controller 31.

[0054] In the present embodiment, the delay unit 31 included in the transmitter 3 is configured to be realized by software using the controller 31, but this is merely an example. The delay unit 31 may be a delay circuit configured as hardware. Furthermore, the delay unit 31 may be a delay device provided separately from the transmitter 3.

[0055] Fig. 6 is a flowchart showing an example of the operation of the transmitter 3. The operation shown in Fig. 6 is started, for example, when a power source for starting the communication system 100 is turned on. The power source switch for starting the communication system 100 is, for example, a power source switch for an audio device. The power source switch for starting the communication system 100 may be a dedicated switch, but, as an example, it may also be used as a switch for the ACC power source of the vehicle.

[0056] In step S1, the controller 31 (delay control unit 311) monitors whether or not audio information has been acquired from the sound reproduction device 1 via the transmission-side amplifier 2. If the controller 31 has acquired audio information (Yes in step S1), the controller 31 proceeds to the next step S2. If the controller 31 has not acquired audio information (No in step S1), the controller 31 continues the processing of step S1.

[0057] In step S2, the controller 31 (delay control unit 311) delays the timing of starting transmission of the audio information by a predetermined time. When the delay process is completed, the controller 31 proceeds to the next step S3.

[0058] In step S3, the controller 31 (transmission control unit 312) causes the transmission unit 32 to transmit the audio information at a timing delayed by a predetermined time from the input timing by delay processing. When the transmission processing is completed, the controller 31 proceeds to the next step S4.

[0059] In step S4, the controller 31 (transmission control unit 312) determines whether or not there is a termination reason for terminating the operation of the transmitter 3. The termination reason may be, for example, a command to stop the operation of the communication system 100 or the occurrence of a failure in the communication system 100. If there is a termination reason (Yes in step S4), the processing shown in Fig. 6 is terminated. If there is no termination reason (No in step S4), the controller 31 returns the processing to step S1 and repeats the processing from step S1 onwards.

[0060] (1-3-2. Receiver) Fig. 7 is a block diagram showing a schematic configuration of the receiver 4 included in the communication system 100. Note that Fig. 7 shows components necessary for explaining the features of this embodiment, and omits descriptions of general components. The receiver 4 is used as one of the receivers provided corresponding to each of the multiple transmitters 3, and is specifically a first receiver 4a or a second receiver 4b. That is, the first receiver 4a and the second receiver 4b have the same configuration.

[0061] As shown in Fig. 7, the receiver 4 includes a receiving unit 41 and a controller 42. The receiving unit 41 is the same as the receiving unit 41 shown in Fig. 1, and more specifically, is a first receiving unit 41a or a second receiving unit 41b. The controller 42 can be interpreted as the adjusting unit 42 shown in Fig. 1 (more specifically, the first adjusting unit 42a or the second adjusting unit 42b), and is therefore denoted by the same reference numeral.

[0062] Under the control of the controller 42, the receiving unit 41 starts receiving at a timing that matches the transmission start timing of the corresponding transmitter 3. As a result, the receiving unit 41 receives information transmitted from the corresponding transmitter 3. In this embodiment, the first receiving unit 41a starts receiving at a timing that matches the transmission start timing of the first transmitter 3a, and receives the information transmitted from the first transmitter 3a. The second receiving unit 41b starts receiving at a timing that matches the transmission start timing of the second transmitter 3b, and receives the information transmitted from the second transmitter 3b.

[0063] The controller 42 is a computer device including a processor that performs arithmetic processing and the like. The processor may include, for example, a CPU. The controller 42 may be configured with one processor or multiple processors. When configured with multiple processors, the processors only need to be connected to each other so that they can communicate with each other. The controller 42 also includes computer components such as memory (RAM, ROM, etc.) necessary for executing programs.

[0064] The controller 42 has, as its functions, a reception control unit 421 and a timing control unit 422. Each of the functional units 421, 422 is realized, for example, by a processor executing arithmetic processing in accordance with one program. However, this configuration is not limited thereto, and each of the functional units 421, 422 may be realized, for example, by a processor executing arithmetic processing in accordance with a separate program for each functional unit.

[0065] As described above, each of the functional units 421, 422 may be realized by having a processor execute a program, i.e., by software, but may also be realized by other methods. At least one of the functional units 421, 422 may be realized using, for example, an ASIC or an FPGA. That is, each of the functional units 421, 422 may be realized by hardware using a dedicated IC or the like. Also, each of the functional units 421, 422 may be realized by a combination of software and hardware. Also, each of the functional units 421, 422 is a conceptual component. The function performed by one component may be distributed among multiple components. Also, the functions of multiple components may be integrated into one component.

[0066] The reception control unit 421 controls the receiving unit 41. The reception control unit 421 sets the receiving unit 41 to the reception mode based on transmission timing information of the transmitter 3 acquired in advance using PLC communication or the like. In detail, the reception control unit 421 sets the receiving unit 41 to the reception mode based on the reception mode start time τ start The reception control unit 421 controls the reception unit 41 to enter the reception mode at the reception mode start time τ start The receiving mode is controlled to end at a pre-programmed timing based on the reference time.

[0067] The timing control unit 422 adjusts the timing of output from the receiver 4 of the information received by the receiving unit 41. More specifically, the timing control unit 422 delays the output timing of the received information by a predetermined delay time. This delay time is determined based on the time by which the delay unit 31 in the corresponding transmitter 3 delays the transmission start timing. This delay time is also determined in relation to the output timing of information from the other receivers. These points will be described in detail later. In this embodiment, the other receiver is the second receiver 4b when the receiver 4 is the first receiver 4a, and is the first receiver 4a when the receiver 4 is the second receiver 4b.

[0068] As can be seen from the above explanation, the receiver 4 includes a receiving unit 41 that starts receiving in synchronization with the transmission start timing of the corresponding transmitter 3. With this configuration, even if the difference in the transmission start timing between the multiple transmitters 3 is small, the receiver 4 can receive information from the transmitter 3 corresponding to itself while avoiding radio wave interference with other transmitters. In other words, even if the multiple transmitters 3 transmit with mostly overlapping timing, the receiver 4 can receive information from the transmitter 3 corresponding to itself.

[0069] Furthermore, the controller 42 can be said to be an adjustment unit that adjusts the output timing of the information received by the receiving unit 41 with the output timing of information from other receivers. That is, the receiver 4 includes an adjustment unit 42 that adjusts the output timing of the information received by the receiving unit 41 with the output timing of information from other receivers. With this configuration, the output timings of multiple receivers 4 can be aligned or intentionally shifted.

[0070] In this embodiment, the output timing is aligned among the multiple receivers 4. This will be described in detail later. In this embodiment, the other transmitter is the second transmitter 3b when the transmitter 3 is the first transmitter 3a. In addition, the other transmitter is the first transmitter 3a when the transmitter 3 is the second transmitter 3b.

[0071] Furthermore, the functions of the receiver 4 described above can also be said to be functions that are obtained by causing a computer device included in the receiver 4 to execute processing in accordance with a reception control program stored in a memory provided in the controller 42.

[0072] In the present embodiment, the adjustment unit 42 included in the receiver 4 is configured to be realized by software using the controller 42, but this is merely an example. The adjustment unit 42 may be configured by hardware, and specifically may be a delay circuit. The adjustment unit 42 may also be a device (specifically, a delay device) provided separately from the receiver 4.

[0073] Fig. 8 is a flowchart showing an example of the operation of the receiver 4. The operation shown in Fig. 8 is started at the same timing as that of the transmitter 3 described above. That is, the operation shown in Fig. 8 is started, for example, when the power supply for starting the communication system 100 is turned on.

[0074] In step S11, the controller 42 (reception control unit 421) monitors whether it is time to start receiving. The timing to start receiving is determined based on transmission timing information of the transmitter 3 acquired in advance using PLC communication or the like, as described above. If it is time to start receiving (Yes in step S11), the controller 42 proceeds to the next step S12. If it is not time to start receiving (No in step S11), the controller 42 continues the processing of step S11.

[0075] In step S12, the controller 42 (reception control unit 421) issues a command to the receiving unit 41 to put the receiving unit 41 into reception mode, and ends the reception mode when a predetermined time has elapsed since the start of the reception mode. This causes the receiving unit 41 to receive information transmitted from the corresponding transmitter 3. When the reception process is complete, the controller 42 proceeds to the next step, S13.

[0076] In step S13, the controller 42 (timing control section 422) controls the output timing of the information received by the receiving section 41 to the receiving-side amplifier 5. Specifically, it manages the information so that it is output at a predetermined timing. When the controller 42 completes the control of the output timing, it proceeds to the next step S14.

[0077] In step S14, the controller 42 (timing control section 422) outputs the information received by the receiving section 41 to the receiving-side amplifier 5 at a predetermined timing. When the controller 42 completes the information output process, the process proceeds to the next step S15.

[0078] In step S15, the controller 42 (reception control unit 421) determines whether or not there is a termination reason for terminating the operation of the receiver 4. The termination reason may be, for example, a command to stop the operation of the communication system 100 or the occurrence of a failure in the communication system 100. If there is a termination reason (Yes in step S15), the processing shown in Fig. 8 is terminated. If there is no termination reason (No in step S15), the controller 42 returns the processing to step S11 and repeats the processing from step S11 onwards.

[0079] (1-3-3. Example of communication system operation) Next, a detailed example of the operation of the communication system 100 configured including the transmitter 3 and receiver 4 configured as above will be described.

[0080] First, we will explain the outline of the process from encoding to decoding of the original audio information. Figure 9A is a diagram that schematically illustrates the process from encoding to decoding of an audio signal. The original audio information is an analog signal, and this analog signal is sequentially encoded (A / D converted). The digital signal obtained by the encoding process is received by the receiver 4 via the transmitting buffer and the transmitter 3 as appropriate. The received digital signal is decoded (D / A converted) by the decoder via the receiving buffer. The analog signal obtained by the decoding process is input to the speaker 6 and emitted as sound. Although the time length varies depending on the signal processing speed, compression level, and communication rate, digital signals are shorter than analog signals. Therefore, by utilizing a buffer, the original audio waveform can be reproduced without interruption, enabling continuous playback. Note that similar encoding and decoding processes are performed even when the information is video information rather than audio information.

[0081] FIG. 9B is a time chart illustrating the operation of the communication system 100. For ease of understanding, FIG. 9B shows only one communication frame. FIG. 9B also assumes that first audio information and second audio information are output from the sound reproducing device 1, the first audio information is input to the transmitting-side first amplifier 2a, and the second audio information is input to the transmitting-side second amplifier 2b. The first audio information is audio information for the left channel, and the second audio information is audio information for the right channel. The first audio information and second audio information are simultaneously output from the sound reproducing device 1 and simultaneously input to the transmitting-side amplifiers 2a and 2b.

[0082] 9B, the output of the first audio information from the transmitting-side first amplifier 2a to the first delay unit 31a and the output of the second audio information from the transmitting-side second amplifier 2b to the second delay unit 31b are simultaneous (at the same timing). Therefore, the input of the first audio information to the first delay unit 31a and the input of the second audio information to the second delay unit 31b are simultaneous.

[0083] As described above, the delay times (set delay times) set in the first delay unit 31a and the second delay unit 31b are different. Specifically, the set delay time in the second delay unit 31b is longer than the set delay time in the first delay unit 31a. Therefore, the output timing of the second audio information in the second delay unit 31b is delayed from the output timing of the first audio information in the first delay unit 31a by the difference t1 between the set delay times of both. Note that the set delay time in the first delay unit 31a may be zero (no delay time).

[0084] The first transmitter 32a transmits the first audio information to the first receiver 4a at a timing corresponding to the delay time set by the first delay unit 31a. The second transmitter 32b transmits the second audio information to the second receiver 4b at a timing corresponding to the delay time set by the second delay unit 31b. Because the delay times set by the first delay unit 31a and the second delay unit 31b are different, the timing at which the first transmitter 32a starts transmitting the first audio information and the timing at which the second transmitter 32b starts transmitting the second audio information are shifted (by a time t1). That is, the communication method of this embodiment is configured such that the multiple information is transmitted from the multiple transmitters 3a and 3b at timings that are shifted and partially overlap with each other. In other words, each of the multiple transmitters 3a and 3b transmits information (audio information) at timings that are shifted and partially overlap with each other.

[0085] The time difference t1 is set to the minimum time necessary for preventing interference between the transmissions of the first transmitter 32a (first transmitter 3a) and the second transmitter 32b (second transmitter 3b) in UWB communication, in order to ensure that the transmission timings of the first transmitter 32a (first transmitter 3a) and the second transmitter 32b (second transmitter 3b) overlap as much as possible. This minimum time corresponds to the time required for synchronization using the preamble at the beginning of a communication frame in UWB communication.

[0086] The first receiving unit 41a starts receiving in accordance with the transmission start timing of the first transmitting unit 32a (first transmitter 3a). The second receiving unit 41b starts receiving in accordance with the transmission start timing of the second transmitting unit 32b (second transmitter 3b). Because there is a difference in the transmission start timing between the first transmitting unit 32a and the second transmitting unit 32b, the reception start timing of the first receiving unit 41a and the second receiving unit 41b is shifted by the time difference (time t1).

[0087] That is, in this embodiment, each receiver 4a, 4b corresponding to each of the multiple transmitters 3a, 3b is configured to start reception and receive information (audio information) in accordance with the shifted transmission start timing. The shift in reception start timing is the shift in the timing of switching to the reception mode. Due to the shift in the timing of switching to the reception mode, the first receiving unit 41a (first receiver 4a) and the second receiving unit 41b (second receiver 4b) can properly receive the transmission waves from the corresponding transmitters 3a, 3b.

[0088] The first adjustment unit 42a adjusts the output timing of the first audio information received by the first receiving unit 41a. The second adjustment unit 42b adjusts the output timing of the second audio information received by the second receiving unit 41b. That is, the communication method of this embodiment is configured to adjust the output timing of the information received by each of the receivers 4a and 4b. The communication system 100 includes adjustment units 42a and 42b that adjust the output timing of the information received by each of the receivers 4a and 4b.

[0089] Specifically, the first adjustment unit 42a and the second adjustment unit 42b adjust the timing shifted on the transmitting side to return it to an unshifted state. That is, in this embodiment, the output timing is adjusted so that multiple pieces of information (audio information) are output with aligned timing. Specifically, the timing adjustment is achieved by providing a difference between the delay time until the audio information is output between the first adjustment unit 42a and the second adjustment unit 42b.

[0090] The first audio information output from the first adjustment unit 42a is output (emitted as sound) from the first speaker 6a via the receiving-side first amplifier 5a. The second audio information output from the second adjustment unit 42b is output (emitted as sound) from the second speaker 6b via the receiving-side second amplifier 5b. By adjusting the output timing as described above, the output timing of the first audio information from the first speaker 6a and the output timing of the second audio information from the second speaker 6b become the same.

[0091] As can be seen from the above, in this embodiment, information can be transmitted from the multiple transmitters 3a, 3b to the receivers 4a, 4b in a state where the transmission start timings are shifted from one another while the transmission timings are substantially overlapping. Therefore, on the receiving side, the information received by the receivers 4a, 4b can be output with the timings restored (i.e., aligned) to the original timings that were shifted during transmission, simply by performing a short time adjustment. In other words, in this embodiment, UWB communication between the sound reproducing device 1 and the multiple speakers 6a, 6b can be performed substantially simultaneously, ensuring real-time performance.

[0092] Although the above describes an example in which the present invention is applied to UWB communication between the sound reproduction device 1 and multiple speakers 6a and 6b, the present invention can also be applied to other cases in which simultaneous communication is required. For example, the present invention can also be applied to cases in which UWB communication is used between a video reproduction device and multiple display devices, or between a video and audio reproduction device and a display device and speaker.

[0093] [1-4. Modifications] (1-4-1. First Modified Example) In the first embodiment described above, the adjustment unit 42 adjusts the output timing to output a plurality of pieces of information at the same timing, but this is merely an example. The output timing may be adjusted to output at least one piece of information among the plurality of pieces of information at a timing shifted from the other pieces of information. This allows the output pattern of the audio information to be changed to suit preferences. The present modified example shows an example of such a configuration.

[0094] In this modification, four-channel acoustic signals (four pieces of audio information) are simultaneously output from the sound reproduction device 1. Accordingly, there are four of each of the transmitting amplifiers 2, transmitters 3, receivers 4, receiving amplifiers 5, and speakers 6. Note that four channels is an example, and other numbers of channels may be used. Each transmitter 3 includes a delay unit 31 and a transmitting unit 32, as in the above-described embodiment. Each receiver 4 includes a receiving unit 41 and an adjusting unit 42, as in the above-described embodiment.

[0095] 10 is a time chart illustrating the operation of a communication system according to a first modification of the first embodiment. In this modification, although there are differences in the number of audio information and devices, the flow of operations from the output of an audio signal (audio information) in the sound reproducing device 1 to the reception of information by the receiver 4 is the same as in the above-described embodiment (see FIG. 9B, etc.).

[0096] That is, the first audio information, second audio information, third audio information, and fourth audio information output from the sound reproducing device 1 are simultaneously input to the respective transmitting amplifiers 2, and are simultaneously output from the respective transmitting amplifiers 2 to the respective delay units 31 (respective transmitters 3). The first audio information, second audio information, third audio information, and fourth audio information are output from the respective delay units 31 with a shift in timing. As a result, although not shown in FIG. 10, the transmission start timing of each transmitting unit 32 is shifted. Furthermore, the reception start timing of each receiving unit 41 is shifted in accordance with the shift in the transmission start timing. In detail, the reception timing of the first audio information, second audio information, third audio information, and fourth audio information is shifted in this order, and the information is received by the corresponding receiver 4.

[0097] 10, in this modification, of the pieces of audio information output from the four adjustment units 42, the first audio information and the second audio information are output with the same output timing. Also, of the pieces of audio information output from the four adjustment units 42, the third audio information and the fourth audio information are output with the same output timing. The output timing of the third audio information and the fourth audio information is delayed from the output timing of the first audio information and the second audio information.

[0098] Fig. 11 is a schematic diagram showing the arrangement of four speakers 6 in a vehicle V1 included in a communication system according to a first modification of the first embodiment. In Fig. 11, the first speaker 6a is arranged near the front left side of the vehicle V1 and outputs first audio information. The second speaker 6b is arranged near the rear left side of the vehicle V1 and outputs second audio information. The third speaker 6c is arranged near the front right side of the vehicle V1 and outputs third audio information. The fourth speaker 6d is arranged near the rear right side of the vehicle V1 and outputs fourth audio information.

[0099] Using the driver's seat DS located at the front right of the vehicle V1 as a reference, the first speaker 6a is located in a position far away to the left and in front of the driver's seat DS. The second speaker 6b is located in a position far away to the left and behind the driver's seat DS. The third speaker 6c is located in front of the driver's seat DS, slightly to the right. The fourth speaker 6d is located behind the driver's seat DS, slightly to the right. In other words, the driver's seat DS is not located in the center of the four speakers 6a to 6d, but is located to the right of that center.

[0100] As described above, in this modification, the first speaker 6a and the second speaker 6b, which are far to the left of the driver's seat DS, emit audio information at an earlier timing than the third speaker 6c and the fourth speaker 6d, which are located slightly to the right of the driver's seat DS. As a result, the driver sitting in the driver's seat DS hears the sound as if he or she were in the center of the four speakers 6a to 6d.

[0101] The adjustment patterns for the output timing of audio information shown here are merely examples, and different patterns may be used as appropriate. Furthermore, in the configuration of this modified example, a delay unit (delay circuit or the like) for adjusting the output timing of audio information is provided on the speaker 6 side, not on the sound reproduction device 1 side, making it easy to add functions later.

[0102] (1-4-2. Second Modified Example) 12 is a block diagram showing a schematic configuration of a communication system 100B according to a second modification of Embodiment 1. The communication system 100B according to this modification differs from the configuration of the first embodiment described above in that it includes an equalizer 7.

[0103] In this modification, each of the multiple pieces of information, which are audio information, is equalized after being received by the receiver 4. That is, the communication system 100B of this modification is capable of controlling sound quality. Specifically, a first equalizer 7a that controls frequency characteristics is disposed between the first receiver 4a and the first receiving amplifier 5a. Furthermore, a second equalizer 7b that controls frequency characteristics is disposed between the second receiver 4b and the second receiving amplifier 5b.

[0104] The equalizer 7 may be built into the receiver 4. That is, the equalization process may be performed by processing the audio data in the receiver 4. Alternatively, each of the plurality of pieces of audio information may be equalized before being transmitted by the transmitter 3. In this case, sound quality can still be controlled. In this case, the equalizer may be disposed between the transmitting amplifier 2 and the transmitter 3, or the transmitter 3 may have an equalization process function.

[0105] (1-4-3. Third Modification) 13 is a block diagram showing a schematic configuration of a transmitter 3C included in a communication system according to a third modification of the first embodiment. The configuration of the transmitter 3C of this modification is basically the same as that of the transmitter 3 of the first embodiment described above (see FIG. 5). However, differences are that an equalizer unit 313 and a setting reception unit 314 are added as functional units of a controller 31C, and that a setting operation unit 33 is added as an element constituting the transmitter 3.

[0106] The equalizer unit 313 performs equalization processing on the audio information input to the transmitter 3C. The equalizer unit 313 performs equalization processing by processing the audio data. The equalizer unit 313 is provided in place of the equalizer 7 of the second modified example, and in this modified example, the equalization processing on the audio information is performed before transmission by the transmitter 3C.

[0107] The setting reception unit 314 receives a setting change command from the user using the setting operation unit 33. In response to the received command, the setting reception unit 314 issues a setting change command to the delay control unit 311 and the equalizer unit 313. In response to the setting change command, the delay control unit 311 and the equalizer unit 313 change the currently set delay time and equalizer setting value.

[0108] The setting operation unit 33 includes, for example, an input device and a display device. The setting operation unit 33 may be, for example, a touch panel. The setting operation unit 33 may also serve as a setting operation unit provided in the sound reproduction device 1. This modification is convenient because the user can use the setting operation unit 33 to change the delay time that determines the transmission start timing of the transmitter 3 and the equalizer settings.

[0109] The setting operation unit 33 may be connected to the controller 31C by wire or wirelessly. The wireless connection referred to here may be UWB communication, or may be, for example, Bluetooth (registered trademark) communication. As described above, the equalization function and the transmission-side delay function may be provided outside the transmitter 3C. In this case, the setting operation unit may also be provided to correspond to the externally provided device (delay unit or equalizer).

[0110] The settings in the adjustment unit 42 may also be configured to be changeable by the setting operation unit 33. In this case, a setting change command may be included in information (data) transmitted from the transmitter 3C. As another example, a setting operation unit for changing the settings of the adjustment unit 42 may be provided separately on the receiver 4 side.

[0111] As can be seen from the above description, at least one of the amount of shift in transmission start timing, the amount of adjustment in output timing, and the amount of equalization processing may be configured to be changeable by external operation. By configuring in this way, the audio output using the communication system can be set to suit the user's preferences.

[0112] 2. Second Embodiment Next, a communication system 200 according to a second embodiment of the present invention will be described. In describing the second embodiment, the description of the same content as in the first embodiment will be omitted unless it is particularly necessary.

[0113] 14 is a block diagram showing the configuration of a communication system 200 according to a second embodiment of the present invention. The communication system 200 of the second embodiment also performs UWB communication, similar to the communication system 100 of the first embodiment. The communication system 200 is an in-vehicle system as an example, but may also be, for example, a communication system for mobile objects other than automobiles, a home communication system, an office communication system, or a factory communication system.

[0114] As shown in Fig. 14, a communication system 200 includes a video playback device 8, a plurality of display devices 9, a plurality of transmitters 30, and a plurality of receivers 40. In the example shown in Fig. 14, UWB communication is used for transmitting and receiving video, but this is merely an example. UWB communication may also be used for transmitting and receiving video and audio, for example. In such a case, the video playback device 8 may be replaced with a video and audio playback device, and the display device 9 may be replaced with a video and audio output device.

[0115] The video playback device 8 reads and plays video information from a recording medium such as an optical disc or a USB memory. The video playback device 8 also receives and plays video information from an external device connected via wired or wireless communication. The video playback device 8 is included in, for example, a navigation device or a display audio.

[0116] The display device 9 is a device that displays the video information output from the video playback device 8. The display device 9 is configured using, for example, a liquid crystal display or an organic EL display. In this embodiment, there are multiple display devices 9, and the multiple display devices 9 are configured as a first display device 9a and a second display device 9b.

[0117] The first display device 9a is connected to the video playback device 8 by wire. The second display device 9b is connected to the video playback device 8 wirelessly using UWB communication. The first display device 9a is configured, for example, as an integrated part with the video playback device 8 placed on the dashboard. That is, the first display device 9a may be part of a navigation device or the like. The second display device 9b is placed in a position away from the video playback device 8, for example, in the center or rear of the vehicle. The first display device 9a and the second display device 9b display the same image. For example, the first display device 9a is a display device for passengers sitting in the driver's seat or passenger seat of the vehicle to view, and the second display device 9b is a display device for passengers sitting in the rear seat of the vehicle to view.

[0118] The number of display devices connected to the video playback device 8 wirelessly using UWB communication is not limited to one, and may be multiple. The first display device 9a may also be a display device connected to the video playback device 8 wirelessly using UWB communication.

[0119] The transmitter 30 is part of a communication device that enables UWB communication between the video playback device 8 and the second display device 9b. The transmitter 30 is connected to the video playback device 8 by wire. The configuration of the transmitter 30 is generally similar to that of the transmitter 3 in the first embodiment. However, the transmitter 30 in this embodiment includes a transmission unit but does not include a delay unit. Since the configuration of the transmission unit is the same as that in the first embodiment, a detailed description thereof will be omitted. Furthermore, in this embodiment, the video playback device 8 has a function that performs a similar function to the delay unit, as described below, so the delay unit is not included. However, if the video playback device 8 does not have such a function, the transmitter 30 may include a delay unit. In this embodiment, there are multiple transmitters 30, and the multiple transmitters 30 include a first transmitter 30a, a second transmitter 30b, and a third transmitter 30c.

[0120] The receiver 40 is a receiver that enables UWB communication between the video playback device 8 and the second display device 9b, and is provided corresponding to the transmitter 30 described above. The receiver 40 is connected to the second display device 9b by wire. The configuration of the receiver 40 is generally similar to the configuration of the receiver 4 of the first embodiment. However, the receiver 40 of this embodiment includes a receiving unit but does not include an adjustment unit. Note that the configuration of the receiving unit is similar to that of the first embodiment, so a detailed description thereof will be omitted.

[0121] In this embodiment, there are multiple receivers 40, and the multiple receivers 40 are composed of a first receiver 40a, a second receiver 40b, and a third receiver 40c. The first receiver 40a is provided corresponding to the first transmitter 30a. The second receiver 40b is provided corresponding to the second transmitter 30b. The third receiver 40c is provided corresponding to the third transmitter 30c.

[0122] Figure 15 is a diagram for explaining a method of transmitting and receiving data between the video playback device 8 and the second display device 9b. The symbol BD in Figure 15 indicates video data transmitted from the video playback device 8 to the second display device 9b. The video data BD is large in size and cannot be transmitted all at once, so it is transmitted divided into multiple pieces of data (communication frames).

[0123] In this embodiment, in order to efficiently transmit data, multiple sets of transmitters 30 and receivers 40 are prepared and parallel transmission is performed. In this embodiment, the multiple systems include a first system SY1 consisting of a first transmitter 30a and a first receiver 40a, a second system SY2 consisting of a second transmitter 30b and a second receiver 40b, and a third system SY3 consisting of a third transmitter 30c and a third receiver 40c (see FIG. 14). Note that the number of systems is an example, and there may be two systems, four systems, or more.

[0124] The multiple data obtained by dividing the video data BD are allocated in order from the beginning as first data D1, second data D2, and third data D3. Then, when allocation up to the third data D3 is completed, allocation is repeated starting from the first data D1. The first data D1 is transmitted and received using the first system SY1. The second data D2 is transmitted and received using the second system SY2. The third data D3 is transmitted and received using the third system SY3.

[0125] In this embodiment, the division of the video data BD and the allocation of the divided data to groups (allocation of D1 to D3) are performed by a microcomputer 81 included in the video playback device 8. However, the microcomputer that divides the video data BD and allocates the divided data may be provided separately from the microcomputer of the video playback device 8.

[0126] In this embodiment, transmission and reception of each system SY1 to SY3 is performed to avoid radio wave interference and enable efficient communication. In detail, similar to the first embodiment, a plurality of pieces of information (D1 to D3) are transmitted from a plurality of transmitters 30a to 30c at timings that overlap with each other while shifting the start timings of their transmissions. The transmissions from the plurality of transmitters 30a to 30c are performed so that the transmission timings overlap as much as possible. Furthermore, the receivers 40a to 40c corresponding to the plurality of transmitters 30a to 30c start reception in accordance with the shifted start timings of their transmissions and receive the information (D1 to D3). As can be seen from the above explanation, in this embodiment, the plurality of pieces of information transmitted from the plurality of transmitters 30a to 30c at overlapping timings are divided information obtained by dividing one piece of information into multiple pieces.

[0127] Fig. 16 is a time chart illustrating the operation of the communication system 200 of the second embodiment. Fig. 16 shows, as an example, an example in which data for two communication frames is transmitted and received in each of the systems SY1 to SY3. The operation shown in Fig. 16 is started, for example, when a command to play a video is issued to the video playback device 8.

[0128] First, data D1 to D3 are output from the microcomputer 81 (transmitting microcomputer 81) of the video playback device 8 to each of the transmitters 30a to 30c. Specifically, the transmitting microcomputer 81 outputs first data D1 to the first transmitter 30a. The transmitting microcomputer 81 outputs second data D2 to the second transmitter 30b. The transmitting microcomputer 81 outputs third data D3 to the third transmitter 30c.

[0129] 16, the transmitting microcomputer 81 outputs the first data D1, the second data D2, and the third data D3 with a staggered timing. Specifically, the second data D2 is output with a slight delay relative to the first data D1. The third data D3 is output with a slight delay relative to the second data D2. The reason for staggering the timing in this manner is to avoid radio wave interference between the next transmissions by the transmitter 30, as in the first embodiment. Note that, although the transmitting microcomputer 81 is configured not to stagger the timing in this embodiment, a delay unit may be provided in the transmitter 30, and the timing may be shifted by the transmitter 30, as in the first embodiment.

[0130] The transmitters 30a to 30c, to which the data D1 to D3 have been input by the transmitting microcomputer 81, transmit the data sequentially in accordance with the input timing. That is, the transmitters 30a to 30c transmit data at timings that are offset from each other. Specifically, the first transmitter 30a transmits the first data D1. The second transmitter 30b transmits the second data D2 with a timing slightly delayed from the first data D1. The third transmitter 30c transmits the third data D3 with a timing slightly delayed from the second data D2.

[0131] Although not shown in Fig. 16, each of the receivers 40a to 40c starts reception in synchronization with the transmission start timing of each of the transmitters 30a to 30c, and receives the data D1 to D3. In particular, the first receiver 40a starts reception in synchronization with the transmission start timing of the first transmitter 30a, and receives the first data D1. The second receiver 40b starts reception in synchronization with the transmission start timing of the second transmitter 30b, and receives the second data D2. The third receiver 40c starts reception in synchronization with the transmission start timing of the third transmitter 30c, and receives the third data D3.

[0132] Then, each of the receivers 40a to 40c outputs the received data D1 to D3 to the microcomputer 91 (receiving-side microcomputer 91) of the second display device 9b, as shown in Fig. 16. The output timing of each of the data D1 to D3 from each of the receivers 40a to 40c to the receiving-side microcomputer 91 is also shifted because the reception start timings are shifted.

[0133] 16, the receiving microcomputer 91 sequentially outputs the data D1 to D3 input from the receivers 40a to 40c in the order of the original information BD (see FIG. 15). In this embodiment, an image is displayed in accordance with the output.

[0134] In this embodiment, the receiving microcomputer 91 has a role of adjusting the output timing of the information received by each of the receivers 40a to 40c. That is, the receiving microcomputer 91 can be said to be an example of an adjustment unit of the present invention that adjusts the output timing of the information received by each of the receivers 40a to 40c. In detail, the adjustment of the output timing by the receiving microcomputer 91 is an adjustment that restores each of the multiple pieces of divided information D1 to D3 to the output order of the original information BD (see FIG. 15) before division.

[0135] As can be seen from the above, in this embodiment, information (video) is divided into data for multiple systems SY1 to SY3, and the divided data is transmitted and received in what can essentially be considered simultaneous communication. Then, the divided data is restored to its original state (data sequence) and output to the outside. With this configuration, it is possible to perform communication at a significantly higher communication rate than when UWB communication is performed using only one system. In other words, it is possible to improve communication efficiency. As a result, it is possible to reduce the possibility that video output will be delayed due to the influence of the communication rate, resulting in a loss of real-time performance.

[0136] This will be further explained with reference to Figures 16 and 17. Figure 17 is a diagram showing a comparative example. In Figures 16 and 17, the length (horizontal length) of the data output from the receiving microcomputer is shorter than the data output from the receiver. This indicates that the output rate of the receiving microcomputer 91 is faster than the communication rate of UWB communication.

[0137] Normally, the receiving microcomputer 91 cannot output data until it has received data output from the receiver 40. For this reason, as shown in Figure 17, if the output rate of the receiving microcomputer 91 is faster than the communication rate of UWB communication, a waiting time WT occurs in the receiving microcomputer 91 after it has finished outputting the first received data until it is ready to output the next data. As a result, the continuity of data output cannot be ensured, and images cannot be displayed in real time.

[0138] In this regard, in the configuration of this embodiment, data is divided into three systems SY1 to SY3, and communication of these three systems SY1 to SY3 is essentially simultaneous. For this reason, as shown in FIG. 16, when the output of first data D1 is completed, second data D2 exists to be output next. Similarly, when the output of second data D2 is completed, third data D3 exists to be output next. Furthermore, when the output of third data D3 is completed, first data D1 exists to be output next. This state is repeated according to the size of the original video data BD (see FIG. 15). This reduces the possibility that the communication rate will cause delays in video output, impairing real-time performance.

[0139] <3. Things to keep in mind> Various technical features disclosed in the description of the present invention may be modified in various ways without departing from the spirit of the technical creation. Furthermore, multiple embodiments and modifications disclosed in the description of the present invention may be combined to the extent possible. [Explanation of symbols]

[0140] 3, 3C, 30... transmitter 3a, 30a...1st transmitter 3b, 30b...2nd transmitter 4, 40... receiver 4a, 40a...First receiver 4b, 40b... Second receiver 30c···Third transmitter 31 Delay section 31a First delay section 31b Second delay section 32 Transmitter 32a First transmitter 32b Second transmitter 40c···Third receiver 41 Receiving unit 41a First receiving unit 41b Second receiving unit 42 Controller, adjustment unit 42a...1st adjustment section 42b...Second adjustment section 91... Microcomputer, receiving microcomputer (adjustment section) 100, 100B, 200... Communication systems

Claims

1. A communication method using UWB communication, The plurality of pieces of information are transmitted from a plurality of transmitters at timings that are partially overlapping while shifting the timings at which the transmission starts; each receiver corresponding to each of the plurality of transmitters starts reception in accordance with the shifted transmission start timing and receives the information; Communication method.

2. adjusting the output timing of the information received by each of the receivers; The communication method according to claim 1 .

3. By adjusting the output timing, the plurality of pieces of information are output at the same timing. The communication method according to claim 2 .

4. By adjusting the output timing, at least one piece of information among the plurality of pieces of information is output at a timing shifted from other pieces of information. The communication method according to claim 2 .

5. Each of the plurality of pieces of information is audio information and is equalized before being transmitted by the transmitter or after being received by the receiver. A communication method according to any one of claims 2 to 4.

6. At least one of the amount of shifting the transmission start timing, the amount of adjustment of the output timing, and the set amount of the equalization process is configured to be changeable by an external operation. The communication method according to claim 5.

7. the plurality of pieces of information are divided pieces of information obtained by dividing one piece of information into a plurality of pieces, The adjustment of the output timing is an adjustment to restore each of the plurality of pieces of split information to the output order of the original information before splitting. The communication method according to claim 2 .

8. A communication system for performing UWB communication, a plurality of transmitters for transmitting information; a plurality of receivers provided corresponding to the plurality of transmitters, respectively; Equipped with each of the plurality of transmitters transmits the information at a timing that is shifted from and partially overlaps with the other transmitters; each of the plurality of receivers starts reception in accordance with the shifted transmission start timing and receives the information; Communication system.

9. further comprising an adjustment unit that adjusts the output timing of the information received by each of the receivers; 9. The communication system of claim 8.

10. A transmitter used as one of a plurality of transmitters used in a pair for UWB communication, a delay unit that delays the timing of starting transmission of input information; a transmitting unit that transmits the information at a timing that partially overlaps with the other transmitters while shifting the transmission start timing with respect to the other transmitters by using the delay caused by the delay unit; A transmitter comprising:

11. A transmission control program for a transmitter that is used as one of a plurality of transmitters that are used in a group for UWB communication, comprising: causing the transmitter to transmit the information at a timing that is shifted and partially overlaps with the timing at which the other transmitters start transmitting the information; Transmission control program.

12. A receiver used as one of a plurality of receivers for UWB communication provided corresponding to each of a plurality of transmitters, a receiving unit that starts receiving in synchronization with the transmission start timing of the corresponding transmitter; Receiver.

13. Further, an adjustment unit adjusts the output timing of the information received by the receiving unit with the output timing of the information of the other receivers.

13. The receiver of claim 12.

14. A reception control program for a receiver used as one of a plurality of UWB communication receivers provided corresponding to a plurality of transmitters, the program comprising: causing the receiver to start receiving in synchronization with the transmission start timing of the corresponding transmitter; Reception control program.

15. and causing the receiver to further adjust the output timing of the received information with the output timing of information of the other receivers. The reception control program according to claim 14.

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