Optical communication system, terminal device, and base station device

Abstract

This terminal device for performing optical communication with a base station device comprises: a plurality of light-receiving units arranged toward an optical axis in mutually different directions; and a control unit which, when receiving same data optical signals which are simultaneously broadcast from a plurality of base station devices, performs an identification process for identifying each of the light receiving units which receive the same data optical signals. The control unit performs a synthesis process for synthesizing the reception signals of the respective light-emitting units identified by the identification process.

Description

[Technical Field]

[0001] The present disclosure relates to an optical communication system, a terminal device, and a base station device. [Background technology]

[0002] For example, optical communication systems that use light (especially visible light) as a transmission medium for underwater communication are known. Because light has high directivity, conventional optical communication systems generally perform one-to-one communication (i.e., unicast communication) between the transmitting and receiving sides, assuming that the optical communication devices on the transmitting and receiving sides are fixed. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 4-103232 Summary of the Invention

[0004] An optical communication system according to a first aspect is a system in which a terminal device and a base station device perform optical communication. The terminal device includes a plurality of light receiving units arranged with their optical axes facing different directions, and a control unit that performs a specification process to identify each light receiving unit that receives the same data optical signal when the terminal device receives the same data optical signal that is simultaneously broadcast from a plurality of base stations. The control unit performs a combination process to combine the received signals of the light receiving units identified by the specification process.

[0005] A terminal device according to a second aspect is a device that performs optical communication with a base station device. The terminal device includes a plurality of light receiving units arranged with their optical axes facing different directions, and a control unit that performs a specification process to identify each light receiving unit that receives the same data optical signal when the terminal device receives the same data optical signal that is simultaneously broadcast from a plurality of base stations. The control unit performs a combination process to combine the received signals of the light receiving units identified by the specification process.

[0006] A base station device according to a third aspect is a device that performs optical communication with a terminal device, and includes a plurality of light-emitting units arranged with their optical axes facing different directions, and a control unit that controls the plurality of light-emitting units to transmit reference optical signals for broadcast communication and / or control optical signals indicating time slots for broadcast communication when broadcasting the same data optical signal from the plurality of light-emitting units. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a diagram illustrating an example of the configuration of an optical communication system according to a first embodiment. [Figure 2] FIG. 2 is a diagram illustrating an example of the configuration of a base station device according to the first embodiment. [Figure 3] 1 is a diagram illustrating an example of the external configuration of a base station device according to a first embodiment. [Figure 4] FIG. 2 is a diagram illustrating an example of the configuration of a terminal device according to the first embodiment. [Figure 5] 1 is a diagram illustrating an example of the external configuration of a terminal device according to a first embodiment. [Figure 6] FIG. 2 is a diagram illustrating DL communication as an example of optical communication according to the first embodiment. [Figure 7] 2 is a diagram illustrating an example of the configuration of a communication frame used in the optical communication system according to the first embodiment. FIG. [Figure 8] FIG. 2 is a diagram illustrating an example of unicast communication according to the first embodiment. [Figure 9] FIG. 10 is a diagram illustrating another example of unicast communication according to the first embodiment. [Figure 10] FIG. 2 is a diagram illustrating an example of broadcast communication according to the first embodiment. [Figure 11] FIG. 2 is a diagram illustrating an example of a time slot used for broadcast communication according to the first embodiment. [Figure 12] FIG. 4 is a diagram showing an example of an operation sequence related to broadcast communication according to the first embodiment. [Figure 13]FIG. 10 is a diagram for explaining the operation of the optical communication system according to the second embodiment. [Figure 14] FIG. 10 is a diagram illustrating an example of the configuration of a base station device according to a second embodiment. [Figure 15] FIG. 10 is a diagram illustrating a first configuration example of a terminal device according to a second embodiment. [Figure 16] FIG. 10 is a diagram illustrating a second configuration example of a terminal device according to the second embodiment. [Figure 17] FIG. 10 is a diagram for explaining the operation of the optical communication system according to the third embodiment. [Figure 18] FIG. 11 is a diagram showing an example of an operation sequence related to broadcast communication according to the third embodiment. [Figure 19] FIG. 10 is a diagram for explaining another embodiment. [Figure 20] FIG. 10 is a diagram for explaining another embodiment. [Figure 21] FIG. 10 is a diagram for explaining another embodiment. [Figure 22] FIG. 10 is a diagram for explaining another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] In the future, it is expected that optical communication between multiple terminal devices and a base station device will be realized in optical communication systems. Under such assumptions, when a base station device transmits common data to multiple terminal devices, it is desirable for the base station to realize communication with an unspecified number of terminal devices (i.e., broadcast communication). However, because light has high directionality, it is difficult to realize broadcast communication.

[0009] Therefore, an object of the present disclosure is to realize broadcast communication using light as a transmission medium.

[0010] An optical communication system according to an embodiment will be described with reference to the drawings. In the description of the drawings, the same or similar parts are denoted by the same or similar reference numerals.

[0011] The optical communication system according to the embodiment is a system that performs optical communication using visible light as an example of light. However, the optical communication system may be a system that performs optical communication using light other than visible light, for example, infrared light. Furthermore, the optical communication system according to the embodiment is a system that performs optical communication underwater. However, the optical communication system is not limited to a system that performs optical communication underwater, and may be a system that performs optical communication in space, for example.

[0012] (1) First embodiment First, an optical communication system according to a first embodiment will be described.

[0013] (1.1) Example of optical communication system configuration 1 is a diagram showing an example of the configuration of an optical communication system 1 according to this embodiment. The optical communication system 1 includes a plurality of terminal devices 100 (100a, 100b) and a base station device 200. However, the number of terminal devices 100 and the number of base station devices 200 are not limited to those shown in the example of FIG.

[0014] The base station device 200 is an example of an optical communication device. In the example of FIG. 1, the base station device 200 is located on the water surface. For example, the base station device 200 is fixed to a buoy. The base station device 200 is connected to the network 10 via a backhaul line. The backhaul line may be a wireless line. The backhaul line may be a wired line. In order to efficiently secure a communication area underwater, the base station device 200 may be installed a predetermined distance away from other adjacent base station devices. The base station device 200 may be installed temporarily, for example, for a period during which underwater investigations are performed using the terminal device 100.

[0015] The terminal device 100 is another example of an optical communication device. Each terminal device 100 is underwater. Each terminal device 100 is configured to be able to move underwater. For example, each terminal device 100 may be a self-propelled terminal device 100 such as an underwater robot or an underwater drone. Each terminal device 100 performs optical communication (underwater visible light communication in this embodiment) with the base station device 200. In other words, the base station device 200 is a serving base station device for each terminal device 100.

[0016] Each terminal device 100 may include a sensor such as an image sensor and generate sensor data. For example, each terminal device 100 may transmit uplink (UL) data including the sensor data to the base station device 200 by visible light communication. Each terminal device 100 may receive downlink (DL) data including instruction data from the base station device 200 by visible light communication. Each terminal device 100 may move and perform a sensing operation (such as taking a photograph) based on the instruction data.

[0017] Although details will be described later, each of the base station device 200 and the terminal device 100 has multiple optical communication units whose directivities of optical communication (optical axes from another perspective) are oriented in different directions. This allows each of the base station device 200 and the terminal device 100 to perform optical communication in various directions using multiple optical communication units.

[0018] The base station device 200 can perform time-division optical communication with multiple terminal devices 100 using time division multiple access (TDMA). The base station device 200 assigns a time slot to each terminal device 100 and performs optical communication with the terminal devices 100 using the assigned time slot.

[0019] In this embodiment, the optical communication system 1 can perform optical communication via unicast communication, which is one-to-one communication between the base station device 200 and the terminal device 100, and optical communication via broadcast communication between the base station device 200 and an unspecified number of terminal devices 100.

[0020] In the case of unicast communication, the base station device 200 selects, for each terminal device 100, its own optical communication unit that corresponds to the direction of that terminal device 100, and performs optical communication with that terminal device 100 using the selected optical communication unit. Here, the base station device 200 transmits and receives optical signals (data optical signals) that include data specific to the terminal device 100 to and from that terminal device 100. In addition, the base station device 200 individually allocates time slots to be used for unicast communication to each terminal device 100.

[0021] On the other hand, in the case of broadcast communication, the base station device 200 simultaneously transmits optical signals (data optical signals) containing data common to all terminal devices 100 using all of its optical communication units. In this way, in broadcast communication, the base station device 200 simultaneously transmits (i.e., broadcasts) the same data optical signals in all directions that it can support. Here, the base station device 200 commonly allocates time slots for broadcast communication to all terminal devices 100. This makes it possible to improve resource utilization efficiency. The use of broadcast communication is not particularly limited, but for example, the base station device 200 transmits (i.e., broadcasts) data optical signals containing system information, emergency alerts, or map information as data by broadcast communication.

[0022] The terminal device 100 selects its own optical communication unit corresponding to the direction of the base station device 200, which is its own serving base station, and performs optical communication with the base station device 200 using the selected optical communication unit. In the case of unicast communication, the terminal device 100 transmits and receives optical signals (data optical signals) containing data specific to the terminal device 100 to and from the base station device 200, using time slots allocated for unicast communication by the base station device 200. On the other hand, in the case of broadcast communication, the terminal device 100 receives optical signals (data optical signals) containing data common to all terminal devices 100 from the base station device 200, using time slots allocated for broadcast communication by the base station device 200.

[0023] In unicast communication, the base station device 200 can individually control optical communication with the terminal devices 100, making it easy to perform high-quality optical communication that is adapted to the situation of the terminal devices 100 and the state of the propagation path. In contrast, although broadcast communication can improve resource utilization efficiency compared to unicast communication, it is difficult to perform high-quality optical communication because the base station device 200 cannot individually control optical communication with the terminal devices 100.

[0024] (1.2) Example of base station equipment configuration An example of the configuration of the base station device 200 according to the first embodiment will be described.

[0025] (1.2.1) Example of base station device block configuration 2 is a diagram showing an example of the configuration of a base station device 200 according to this embodiment. The base station device 200 includes a plurality of optical communication units 201 (201#0, 201#1, ...), a control unit 230, and a backhaul communication unit 240. The base station device 200 may include a battery for supplying power necessary for the operation of the base station device 200.

[0026] The multiple optical communication units 201 are arranged with the directivity (optical axis) of optical communication facing in different directions. Each optical communication unit 201 performs optical communication (visible light communication in this embodiment) with the terminal device 100 under the control of the control unit 230. Each optical communication unit 201 has a light receiving unit 210 and a light emitting unit 220. Since each optical communication unit 201 has the same configuration, the configuration of optical communication unit 201#0 will be described here.

[0027] The light receiving unit 210#0 of the optical communication unit 201#0 receives an optical signal (a visible light signal in this embodiment) from the terminal device 100 and outputs the received signal to the control unit 230. The light receiving unit 210#0 has at least one light receiving element 211#0 and a receiver 212#0. The light receiving element 211#0 may include a photodiode (PD) and its peripheral circuitry. The light receiving element 211#0 receives an optical signal, converts the received optical signal into an electrical signal (received signal), and outputs the received signal to the receiver 212#0. The optical axis of the light receiving element 211#0 is oriented in a predetermined direction different from the optical axis of the other light receiving elements 211 (e.g., the light receiving element 211#1). The receiver 212#0 may be configured using an FPGA (Field Programmable Gate Array) and / or an SoC (System-on-a-Chip). The receiver 212#0 converts the received signal output by the light receiving element 211#0, performs signal processing on the converted received signal, and outputs the processed signal to the control unit 230. At least a part of the receiver 212#0 may be integrated with another receiver 212 (for example, the receiver 212#1). At least a part of the receiver 212#0 may be integrated with the transmitter 222.

[0028] The light-emitting unit 220#0 of the optical communication unit 201#0 transmits an optical signal (in this embodiment, a visible light signal) to the terminal device 100 under the control of the control unit 230. The light-emitting unit 220#0 has at least one light-emitting element 221#0 and a transmitter 222#0. The light-emitting element 221#0 may include a laser diode (LD) or a light-emitting diode (LED) and its peripheral circuitry. The light-emitting element 221#0 converts an electrical signal (transmission signal) output by the transmitter 222#0 for optical communication into an optical signal and transmits the optical signal. The optical axis of the light-emitting element 221#0 is oriented in a predetermined direction different from the optical axes of other light-emitting elements 221 (e.g., light-emitting element 221#1). However, the optical axis of the light-emitting element 221#0 is oriented in the same direction as the optical axis of the corresponding light-receiving element 211#0. The transmitter 222#0 may be configured using an FPGA and / or an SoC. The transmitter 222#0 performs signal processing on a transmission signal output by the control unit 230, converts the processed signal, and outputs it to the light-emitting element 221#0. At least a part of the transmitter 222#0 may be integrated with another transmitter 222 (for example, the transmitter 222#1). At least a part of the transmitter 222#0 may be integrated with the receiver 212.

[0029] The control unit 230 controls the overall operation of the base station device 200. The operations of the base station device 200 described above and later may be controlled by the control unit 230. For example, the control unit 230 controls multiple optical communication units 201. The control unit 230 includes at least one processor 231 and at least one memory 232. The memory 232 stores programs executed by the processor 231 and information used in processing by the processor 231. The processor 231 may include a digital signal processor and a CPU (Central Processing Unit). The digital signal processor performs modulation, demodulation, encoding, decoding, etc. of digital signals. The CPU executes programs stored in the memory to perform various processes. At least a portion of the control unit 230 may be integrated with the receiver 212. At least a portion of the control unit 230 may be integrated with the transmitter 222.

[0030] The backhaul communication unit 240 performs backhaul communication (wired communication and / or wireless communication) via a backhaul line under the control of the control unit 230. The backhaul communication unit 240 may include a network communication unit 241 that performs communication with the network 10 (e.g., a core network) and an inter-base station communication unit 242 that performs inter-base station communication with adjacent base stations. For example, the network communication unit 241 receives, from the network 10, unicast data to be transmitted to the terminal device 100 by unicast communication and broadcast data to be transmitted to the terminal device 100 by broadcast communication, and outputs the received data to the control unit 230. Furthermore, the network communication unit 241 transmits, to the network 10, unicast data that the optical communication unit 201 has received from the terminal device 100 by unicast communication. The inter-base station communication unit 242 transmits and receives, for example, control data to be used for cooperative control of broadcast communication with adjacent base stations, to and from adjacent base stations.

[0031] In the base station device 200 configured in this manner, the multiple light-emitting units 220 (220#0, 220#1, ...) are arranged with their optical axes facing different directions. When the same data optical signal is to be broadcast from the multiple light-emitting units 220, the control unit 130 controls the multiple light-emitting units 220 to transmit a reference optical signal for broadcast communication (hereinafter referred to as a "broadcast communication reference signal") and / or a control optical signal indicating a time slot for broadcast communication. In other words, when the base station device 200 broadcasts the same data optical signal from all of the light-emitting units 220, it transmits the broadcast communication reference signal and / or the control optical signal from all of the light-emitting units 220.

[0032] This allows the base station device 200 to transmit broadcast communication reference signals and / or control optical signals in all directions that the base station device 200 can support. Furthermore, the terminal device 100 that receives the broadcast communication reference signal can appropriately select the optical communication unit to use for broadcast communication based on the broadcast communication reference signal. Furthermore, the terminal device 100 that receives the control optical signal can appropriately determine the time slot to use for broadcast communication based on the control optical signal.

[0033] (1.2.2) Example of base station equipment external configuration FIG. 3 is a diagram showing an example of the external configuration of the base station device 200 according to this embodiment.

[0034] The base station device 200 includes a hemispherical light-receiving and light-emitting unit 250 and a main body 260 connected to the light-receiving and light-emitting unit 250. However, the base station device 200 may be configured as a sphere in its entirety. The light-receiving and light-emitting unit 250 includes multiple optical communication units 201 arranged in a dispersed manner. Each optical communication unit 201 includes a set of at least one light-receiving element 211 and at least one light-emitting element 221. This configuration enables the base station device 200 to perform optical communication with the terminal device 100 in various directions. In the illustrated example, the hemispherical light-receiving and light-emitting unit 250 includes a total of 19 optical communication units 201, from optical communication unit 201#0 to optical communication unit 201#18. In this case, the base station device 200 may include a total of 19 light-receiving elements, from light-receiving element 211#0 to light-receiving element 211#18, and a total of 19 light-emitting elements, from light-emitting element 221#0 to light-emitting element 211#18.

[0035] (1.3) Example of terminal device configuration An example of the configuration of the terminal device 100 according to the first embodiment will be described.

[0036] (1.3.1) Example of terminal device block configuration 4 is a diagram showing an example of the configuration of a terminal device 100 according to this embodiment. The terminal device 100 has a plurality of optical communication units 101 (101#0, 101#1, ...), a control unit 130, and a movement mechanism 140. The terminal device 100 may have a battery for supplying power necessary for the operation of the terminal device 100. The terminal device 100 may also have a sensor such as an image sensor and generate sensor data.

[0037] The multiple optical communication units 101 are arranged with their optical communication directivities (optical axes) facing in different directions. Each optical communication unit 101 performs optical communication (visible light communication in this embodiment) with the base station device 200 under the control of the control unit 130. Each optical communication unit 101 has a light receiving unit 110 and a light emitting unit 120. Since each optical communication unit 101 has the same configuration, the configuration of optical communication unit 101#0 will be described here.

[0038] The light receiving unit 110#0 of the optical communication unit 101#0 receives an optical signal (a visible light signal in this embodiment) from the base station device 200 and outputs the received signal to the control unit 130. The light receiving unit 110#0 has at least one light receiving element 111#0 and a receiver 112#0. The light receiving element 111#0 may include a photodiode (PD) and its peripheral circuitry. The light receiving element 111#0 receives an optical signal, converts the received optical signal into an electrical signal (received signal), and outputs the received signal to the receiver 112#0. The optical axis of the light receiving element 111#0 is oriented in a predetermined direction different from the optical axis of the other light receiving elements 111 (e.g., the light receiving element 111#1). The receiver 112#0 may be configured using an FPGA and / or an SoC. The receiver 112#0 converts the received signal output by the light receiving element 111#0, performs signal processing on the converted received signal, and outputs the processed signal to the control unit 130. At least a portion of the receiver 112#0 may be integrated with another receiver 112 (for example, the receiver 112#1). At least a portion of the receiver 112#0 may be integrated with the transmitter 122.

[0039] The light-emitting unit 120#0 of the optical communication unit 101#0 transmits an optical signal (in this embodiment, a visible light signal) to the base station device 200 under the control of the control unit 130. The light-emitting unit 120#0 has at least one light-emitting element 121#0 and a transmitter 122#0. The light-emitting element 121#0 may include a laser diode (LD) or a light-emitting diode (LED) and its peripheral circuitry. The light-emitting element 121#0 converts an electrical signal (transmission signal) output by the transmitter 122#0 for optical communication into an optical signal and transmits the optical signal. The optical axis of the light-emitting element 121#0 is oriented in a predetermined direction different from the optical axes of other light-emitting elements 121 (e.g., light-emitting element 121#1). However, the optical axis of the light-emitting element 121#0 is oriented in the same direction as the optical axis of the corresponding light-receiving element 111#0. The transmitter 122#0 may be configured using an FPGA and / or an SoC. The transmitter 122#0 performs signal processing on a transmission signal output by the control unit 130, converts the processed signal, and outputs it to the light-emitting element 121#0. At least a part of the transmitter 122#0 may be integrated with another transmitter 122 (for example, the transmitter 122#1). At least a part of the transmitter 122#0 may be integrated with the receiver 112.

[0040] The control unit 130 controls the overall operation of the terminal device 100. The operations of the terminal device 100 described above and later may be controlled by the control unit 130. For example, the control unit 130 controls multiple optical communication units 101. The control unit 130 includes at least one processor 131 and at least one memory 132. The memory 132 stores programs executed by the processor 131 and information used in processing by the processor 131. The processor 131 may include a digital signal processor and a CPU. The digital signal processor performs modulation, demodulation, encoding, decoding, etc. of digital signals. The CPU executes programs stored in the memory to perform various processes. At least a part of the control unit 130 may be integrated with the receiver 112. At least a part of the control unit 130 may be integrated with the transmitter 122.

[0041] The movement mechanism 140 moves the terminal device 100 under the control of the control unit 130. The movement mechanism 140 includes, for example, a motor and a screw connected to the rotation shaft of the motor.

[0042] In the terminal device 100 configured as described above, the multiple light receiving units 110 (110#0, 110#1, ...) are arranged with their optical axes facing different directions. In this embodiment, when the control unit 130 receives the same data optical signal (i.e., broadcast data optical signal) simultaneously broadcast from the multiple base station devices 200, the control unit 130 performs a specification process to specify each light receiving unit 110 that will receive the same data optical signal. The control unit 130 then performs a combination process to combine the received signals of the light receiving units 110 specified by the specification process. The combination process may be a process using maximal ratio combining. The control unit 130 adjusts the amplitude and phase of the received signals of the light receiving units 110 specified by the specification process and combines them to obtain a combined output with a maximum SNR (Signal-to-Noise Ratio).

[0043] This allows the terminal device 100 to receive broadcast data optical signals from multiple base station devices 200 located in different directions. For example, the terminal device 100 can receive broadcast data from a serving base station as well as from adjacent base stations. The terminal device 100 can then combine the received signals from each base station device 200 to improve the reception quality of the broadcast data. This enables high-quality broadcast communication.

[0044] (1.3.2) Example of external configuration of terminal device FIG. 5 is a diagram showing an example of the external configuration of the terminal device 100 according to this embodiment.

[0045] The terminal device 100 has a hemispherical light-receiving and light-emitting unit 150 and a main body 160 connected to the light-receiving and light-emitting unit 150. However, the terminal device 100 may be configured as a sphere in its entirety. The light-receiving and light-emitting unit 150 has multiple optical communication units 101 arranged in a dispersed manner. Each optical communication unit 101 is provided with a set of at least one light-receiving element 111 and at least one light-emitting element 121. This configuration enables the terminal device 100 to perform optical communication with the base station device 200 in various directions. In the illustrated example, the hemispherical light-receiving and light-emitting unit 150 has a total of seven optical communication units 101, from optical communication unit 101#0 to optical communication unit 101#6. In this case, the terminal device 100 may have a total of seven light-receiving elements, from light-receiving element 111#0 to light-receiving element 111#6, and a total of seven light-emitting elements, from light-emitting element 121#0 to light-emitting element 121#6.

[0046] (1.4) An example of optical communication An example of optical communication according to this embodiment will be described. Fig. 6 is a diagram showing DL communication as an example of optical communication according to this embodiment. In the illustrated example, a cross section of a base station device 200 and a cross section of a terminal device 100 are simply shown for DL ​​communication.

[0047] In base station device 200, multiple light-emitting units 220 are arranged such that the angle formed between the optical axis of one light-emitting unit 220 and the optical axis of another light-emitting unit 220 increases as the distance between the light-emitting unit 220 and another light-emitting unit 220 increases. For example, the angle formed between the optical axis of light-emitting unit 220#0 and the optical axis of light-emitting unit 220#2 that is not adjacent to light-emitting unit 220#0 is larger than the angle formed between the optical axis of light-emitting unit 220#0 and the optical axis of light-emitting unit 220#1 that is adjacent to light-emitting unit 220#0.

[0048] The base station device 200 associates the light-emitting unit 220#4 (optical communication unit #4) corresponding to the direction in which the terminal device 100 is located with the terminal device 100, and performs unicast communication with the terminal device 100 using the light-emitting unit 220#4 (optical communication unit #4). The terminal device 100 associates the light-receiving unit 110#0 (optical communication unit #0) corresponding to the direction in which the base station device 200 is located with the base station device 200, and performs unicast communication with the base station device 200 using the light-receiving unit 110#0 (optical communication unit #0).

[0049] 7 is a diagram showing an example of the configuration of a communication frame used in the optical communication system 1 according to this embodiment. In the example shown, one communication frame is made up of 10 time slots, but the number of time slots making up one communication frame is not limited to 10. Each time slot is made up of a predetermined number of symbol intervals.

[0050] In this frame configuration example, the communication frame consists of one synchronization slot (Sync.), one control slot (Ctrl.), four DL slots (DL slots) #0 to #3, and four UL slots (UL slots) #0 to #3.

[0051] The synchronization slot (Sync.) is a time slot in which the base station device 200 transmits a synchronization optical signal (and a base station device-specific reference signal). The terminal device 100 identifies the base station device 200 by the synchronization optical signal received from the base station device 200, and establishes or maintains synchronization with the base station device 200 using the synchronization optical signal. Note that the base station device-specific reference signal may be transmitted in all slots except for the UL slot.

[0052] The control slot (Ctrl.) is a time slot in which the base station device 200 transmits a control optical signal. The control optical signal includes, for example, scheduling information indicating DL and UL resource allocation (time slot allocation). The terminal device 100 determines its own time slot allocation, for example, from a synchronous optical signal received from the base station device 200.

[0053] DL slots #0 to #3 constitute a DL communication period. The base station device 200 allocates each of the DL slots #0 to #3 to one or more terminal devices 100. The base station device 200 transmits a DL data optical signal in each DL slot. A reference signal (Ref.TxElement) specific to a light-emitting element and a data optical signal may be allocated in each DL slot in a time-division manner.

[0054] UL slots #0 to #3 constitute a UL communication period. The base station device 200 allocates each of the UL slots #0 to #3 to one or more terminal devices 100. The terminal devices 100 transmit UL data optical signals in the allocated UL slots.

[0055] The base station device 200 can simultaneously communicate with multiple terminal devices 100 located in different directions. Specifically, the base station device 200 can spatially multiplex multiple terminal devices 100 located in different directions. Therefore, the base station device 200 may allocate one DL slot or one UL slot to multiple terminal devices 100.

[0056] (1.5) Operation of optical communication systems The operation of the optical communication system 1 according to this embodiment will be described with reference to Figures 8 to 12. The optical communication system 1 according to this embodiment can perform unicast communication and broadcast communication in a time-division manner.

[0057] 8 is a diagram showing an example of unicast communication according to this embodiment. The base station device 200 forms a communication range with each of its own optical communication units 201#0 to 201#4. The terminal device 100 is located within the communication range of the optical communication unit 201#1 of the base station device 200. The terminal device 100 uses its own optical communication unit 101#1 for optical communication (unicast communication) with the base station device 200. In this case, optical signals are transmitted and received between the optical communication unit 201#1 of the base station device 200 and the optical communication unit 101#1 of the terminal device 100.

[0058] 9 is a diagram showing another example of unicast communication according to this embodiment. In the illustrated example, the terminal device 100 selects the base station device 200a as the serving base station. The terminal device 100 is located in an overlapping portion between the communication range of the base station device 200a and the communication range of the neighboring base station device 200b. Here, the terminal device 100 is located within the communication range of the optical communication unit 201#4 of the base station device 200a.

[0059] The terminal device 100 uses its own optical communication unit 101#1 and optical communication unit 101#3 for optical communication (unicast communication) with the base station device 200a. In this case, an optical signal (desired signal) is transmitted and received between the optical communication unit 201#4 of the base station device 200a and the optical communication unit 101#1 and optical communication unit 101#3 of the terminal device 100. When its own optical communication unit 101#1 and optical communication unit 101#3 receive a data optical signal from the optical communication unit 201#4 of the base station device 200a, the terminal device 100 performs a combining process to combine the received signals of its own optical communication unit 101#1 and optical communication unit 101#3.

[0060] In the example of FIG. 9, the optical communication unit 101#1 of the terminal device 100 receives sunlight as an interference signal. In this case, the terminal device 100 does not use the received signal of the optical communication unit 101#1 for combining processing. Also, the optical communication units 101#2 and 101#4 of the terminal device 100 receive an optical signal from the optical communication unit 201#0 of the base station device 200b, which is an adjacent base station, as an interference signal. In this case, the terminal device 100 does not use the received signal of the optical communication unit 101#2 or the received signal of the optical communication unit 101#4 for combining processing. In this way, in unicast communication, the terminal device 100 uses only the received signal of each optical communication unit 101 that receives a desired signal from the serving base station (base station device 200a) for combining processing.

[0061] 10 is a diagram showing an example of broadcast communication according to this embodiment. In the illustrated example, each of the base station device 200a and the base station device 200b simultaneously transmits (broadcasts) the same data optical signal using all of its own optical communication units 201. Specifically, the base station device 200a and the base station device 200b transmit the same data in all directions at the same timing (the same time slot).

[0062] The terminal device 100 has selected the base station device 200a as its serving base station. The terminal device 100 is located in an overlapping area between the coverage area of ​​the base station device 200a and the coverage area of ​​its neighboring base station device 200b. Here, the terminal device 100 is located within the coverage area of ​​the optical communication unit 201#4 of the base station device 200a and within the coverage area of ​​the optical communication unit 201#0 of the base station device 200b. In this case, the terminal device 100 receives, as desired signals, a data optical signal from the optical communication unit 201#4 of the base station device 200a and a data optical signal from the optical communication unit 201#0 of the base station device 200b.

[0063] Specifically, the optical communication units 101#0 and 101#3 of the terminal device 100 receive, as a desired signal, a data optical signal from the optical communication unit 201#4 of the base station device 200a, which is the serving base station. Furthermore, the optical communication units 101#2 and 101#4 of the terminal device 100 receive, as a desired signal, a data optical signal from the optical communication unit 201#0 of the base station device 200b, which is the adjacent base station. The terminal device 100 performs a combining process to combine the received signals of its own optical communication units 101#0, 101#2, 101#3, and 101#4.

[0064] Thus, in broadcast communication, the terminal device 100 uses not only the received signals of each optical communication unit 101 that receives a desired signal from the serving base station (base station device 200a), but also the received signals of each optical communication unit 101 that receives a desired signal from an adjacent base station (base station device 200b) for the combining process. That is, when the control unit 130 of the terminal device 100 receives the same data optical signal broadcast simultaneously from multiple base station devices 200, it performs identification processing to identify each light receiving unit 110 that receives the same data optical signal, and then performs combining processing to combine the received signals of each light receiving unit 110 identified by the identification processing. This makes it possible to use more received signals for the combining process, further improving reception quality.

[0065] However, the optical communication unit 101#1 of the terminal device 100 receives sunlight as an interference signal. In this case, the terminal device 100 does not use the received signal of the optical communication unit 101#1 in the combining process. Specifically, the control unit 130 of the terminal device 100 identifies the optical receiving unit 110 that receives an interference optical signal different from the broadcast data optical signal, and controls the identified optical receiving unit 110 not to use the interference optical signal received by the identified optical receiving unit 110 in the combining process.

[0066] For example, the terminal device 100 can identify its own optical communication unit 101 (specifically, light receiving unit 110) to use for combining processing during broadcast communication based on the broadcast communication reference signal from each base station device 200. The terminal device 100 receives the broadcast communication reference signal transmitted from each base station device 200, determines the direction of each base station device 200 based on the signal, and selects the optical communication unit 101 (light receiving unit 110) to use during broadcast communication. Specifically, the control unit 130 of the terminal device 100 identifies each light receiving unit 110 that receives broadcast communication reference signals from multiple base station devices 200.

[0067] FIG. 11 is a diagram showing an example of time slots used for broadcast communication according to this embodiment.

[0068] In the illustrated example, DL slot #0 in the communication frame is allocated for broadcast communication. However, a time slot different from DL slot #0 may be allocated for broadcast communication. The time slot for broadcast communication may be determined by each base station device 200 based on setting information from the network 10. The time slot may also be determined by each base station device 200 through negotiation in inter-base station communication. The time slot for broadcast communication may be specified in advance in the specifications of the optical communication system 1. The number of time slots for broadcast communication within a communication frame is not limited to one, and there may be multiple time slots within a communication frame.

[0069] Each base station device 200 may transmit a control optical signal including information indicating the time slot for broadcast communication (e.g., slot number) in the control slot (Ctrl.). In the illustrated example, each base station device 200 notifies the terminal device 100 that DL slot #0 is the time slot for broadcast communication. When any of the multiple light receiving units 110 receives a control optical signal, the control unit 130 of the terminal device 100 controls the light receiving units 110 to receive a data optical signal to be broadcast in the time slot specified by the received control optical signal.

[0070] Each base station device 200 may transmit a broadcast communication reference signal in a time slot for broadcast communication. Each base station device 200 may transmit the broadcast communication reference signal in a time slot (for example, a synchronization slot or a control slot) different from the time slot for broadcast communication. The broadcast communication reference signal may be an optical signal including a known signal sequence indicating that broadcast communication is to be applied. The broadcast communication reference signal may be used for measurements (channel estimation and / or reception strength measurement) on the terminal device 100 side.

[0071] Thus, in this embodiment, when the same data optical signal is broadcast from multiple light-emitting units 220, the control unit 230 of the base station device 200 controls the multiple light-emitting units 220 to transmit a broadcast communication reference signal and a control optical signal indicating a time slot for broadcast communication.

[0072] FIG. 12 is a diagram showing an example of an operation sequence related to broadcast communication according to this embodiment.

[0073] In step S101, the control unit 230 of the base station device 200a controls each light-emitting unit 220 to transmit a broadcast communication reference signal. In step S102, the control unit 230 of the base station device 200b controls each light-emitting unit 220 to transmit a broadcast communication reference signal. The terminal device 100 receives the broadcast communication reference signal from each base station device 200.

[0074] In step S103, the control unit 130 of the terminal device 100 identifies the light receiving unit 110 to be used for the combining process (broadcast reception, from another perspective) depending on the reception status of the broadcast communication reference signal. That is, when the control unit 130 of the terminal device 100 receives the same data optical signal broadcast simultaneously from multiple base station devices 200 (200a, 200b), it identifies each light receiving unit 110 that receives the same data optical signal. In this embodiment, the control unit 130 of the terminal device 100 identifies each light receiving unit 110 that has received the broadcast communication reference signal to be used for the combining process. Here, the explanation will be given assuming that the light receiving unit 110#0 of the terminal device 100 receives the broadcast communication reference signal from the base station device 200a, and the light receiving unit 110#1 of the terminal device 100 receives the broadcast communication reference signal from the base station device 200b. In this case, the control unit 130 of the terminal device 100 determines to use the light receiving units 110#0 and 110#1 for the synthesis process.

[0075] In step S104, the control unit 230 of the base station device 200a controls each light-emitting unit 220 to transmit a control optical signal including information indicating a time slot for broadcast communication. In step S105, the control unit 230 of the base station device 200b controls each light-emitting unit 220 to transmit a control optical signal including information indicating a time slot for broadcast communication. The terminal device 100 receives a control optical signal from each base station device 200. Here, the explanation will proceed assuming that the light-receiving unit 110#0 of the terminal device 100 receives a control optical signal from the base station device 200a, and the light-receiving unit 110#1 of the terminal device 100 receives a control optical signal from the base station device 200b. In this case, the control unit 130 of the terminal device 100 may combine and decode the received signals of the light-receiving unit 110#0 and the light-receiving unit 110#1.

[0076] In the illustrated example, the transmission and reception of the control optical signal is performed after the transmission and reception of the broadcast communication reference signal, but the transmission and reception of the control optical signal may occur before the transmission and reception of the broadcast communication reference signal. In this case, the control unit 130 of the terminal device 100 may identify the time slot for broadcast communication based on the control optical signal, and then identify the light receiving unit 110 to be used for the combining process (broadcast reception) based on the broadcast communication reference signal. Alternatively, the control unit 130 of the terminal device 100 may further identify the light receiving unit 110 to be used for the combining process (broadcast reception) based on the control optical signal. In this case, the transmission and reception of the broadcast communication reference signal may be unnecessary. Alternatively, each base station device 200 may transmit a broadcast communication reference signal in the time slot for broadcast communication to implicitly notify the terminal device 100 of the time slot for broadcast communication. In this case, the transmission and reception of the control optical signal may be unnecessary.

[0077] In step S106, the control unit 130 of the terminal device 100 identifies a time slot for broadcast communication based on the control optical signal received by the light receiving unit 110#1.

[0078] In step S107, the control unit 230 of the base station device 200a controls each light-emitting unit 220 to transmit a data optical signal including broadcast data in the time slot for broadcast communication. In step S108, the control unit 230 of the base station device 200b controls each light-emitting unit 220 to transmit a data optical signal including broadcast data in the time slot for broadcast communication. The terminal device 100 receives the same data optical signal from each base station device 200. Here, the explanation will proceed assuming that the light-receiving unit 110#0 of the terminal device 100 receives the data optical signal from the base station device 200a, and the light-receiving unit 110#1 of the terminal device 100 receives the data optical signal from the base station device 200b.

[0079] In step S109, the control unit 130 of the terminal device 100 combines the received signals from the light receiving unit 110#0 and the light receiving unit 110#1, and decodes the combined received signal.

[0080] (2) Second embodiment Next, an optical communication system 1 according to a second embodiment will be described, focusing on differences from the optical communication system 1 according to the first embodiment. Note that this embodiment can be implemented in combination with the first embodiment.

[0081] When visible light communication is performed underwater, the propagation characteristics differ depending on the color (i.e., wavelength) of the visible light used in the visible light communication. For example, assuming four colors, blue, green, red, and yellow, blue and green generally propagate farther than red and yellow even with the same transmission power. However, depending on the turbidity and / or plankton concentration in the water, red and yellow may have better propagation characteristics than blue and green. Therefore, sufficient reception quality may not be obtained with single-color broadcast communication. In this embodiment, broadcast communication using multiple colors is performed, enabling a line with even better reception quality.

[0082] FIG. 13 is a diagram for explaining the operation of the optical communication system 1 according to this embodiment.

[0083] In this embodiment, each of the multiple light-emitting units 220 of the base station device 200 transmits a broadcast data signal (the same data optical signal) in multiple colors with different wavelengths. In the illustrated example, four colors, blue light, green light, red light, and yellow light, are used, but only two colors, for example, blue light and yellow light, may be used. The light-receiving unit 110 of the terminal device 100 receives the broadcast data signal in at least one of the multiple colors. This increases the likelihood that the terminal device 100 can receive the broadcast data signal in another color, even if good propagation characteristics cannot be obtained for a certain color, thereby improving reception quality.

[0084] FIG. 14 is a diagram showing an example of the configuration of a base station device 200 according to this embodiment.

[0085] In this embodiment, each of the multiple light-emitting units 220 of the base station device 200 includes multiple light-emitting elements 221 provided corresponding to multiple colors. In the illustrated example, the light-emitting unit 220#0 includes a blue light-emitting element 221#0B, a green light-emitting element 221#0G, a red light-emitting element 221#0R, and a yellow light-emitting element 221#0Y. Each light-emitting element 221#0 is connected to a transmitter 222#0. The control unit 130 of the base station device 200 controls the multiple light-emitting elements 221#0 to transmit broadcast data signals (the same data optical signal) in multiple colors (blue, green, red, and yellow).

[0086] Here, the blue light-emitting element 221#0B and the green light-emitting element 221#0G may be used for long-distance broadcast communication, and the red light-emitting element 221#0R and the yellow light-emitting element 221#0Y may be used for short-distance broadcast communication.

[0087] The base station device 200 may have a sensor that measures underwater communication environment parameters (such as turbidity and / or plankton concentration). The control unit 130 of the base station device 200 may select a light-emitting element 221#0 to be used for broadcast communication from among the multiple light-emitting elements 221#0 based on measurements obtained by the sensor, and may control the selected light-emitting element 221#0 to transmit a broadcast data signal (the same data optical signal). For example, if the turbidity and / or plankton concentration in the water are higher than a threshold, the control unit 130 may select the red light-emitting element 221#0R and / or the yellow light-emitting element 221#0Y, and if not, the control unit 130 may select the blue light-emitting element 221#0B and / or the green light-emitting element 221#0G.

[0088] FIG. 15 is a diagram showing a first configuration example of the terminal device 100 according to this embodiment.

[0089] In this configuration example, each of the multiple light receiving units 110 of the terminal device 100 includes multiple light receiving elements 111 provided with color filters of each color. In the illustrated example, the light receiving unit 110#0 includes a blue light receiving element 111#0B, a green light receiving element 111#0G, a red light receiving element 111#0R, and a yellow light receiving element 111#0Y. Each light receiving element 111#0 is connected to the transmitter 122#0. The control unit 130 of the terminal device 100 performs a combining process to combine the received signals of the light receiving elements 111#0. The control unit 130 of the terminal device 100 may control the receiver 112#0 to perform the combining process.

[0090] FIG. 16 is a diagram showing a second configuration example of the terminal device 100 according to this embodiment.

[0091] In this configuration example, each of the multiple light receiving units 110 of the terminal device 100 includes a light receiving element 111 and a bandpass filter (BPF) 1121 that separates the received signal of the light receiving element 111 by color. In the illustrated example, the receiver 112#0 of the light receiving unit 110#0 includes a blue bandpass filter 1121B, a green bandpass filter 1121G, a red bandpass filter 1121R, and a yellow bandpass filter 1121Y. Each bandpass filter 1121 extracts the received signal of the corresponding color component from the received signal of the light receiving element 111 and outputs the extracted received signal. The control unit 130 of the terminal device 100 performs a combining process to combine the received signals output by the bandpass filters 1121. If the receiver 112#0 has a combining means, the control unit 130 of the terminal device 100 may control the receiver 112#0 to perform the combining process.

[0092] (3) Third embodiment Next, the optical communication system 1 according to the third embodiment will be described, focusing mainly on the differences from the optical communication systems 1 according to the first and second embodiments. Note that this embodiment can be implemented in combination with the first and / or second embodiments.

[0093] In the above-described embodiment, if another terminal device 100 exists between one terminal device 100 and the base station device 200, the broadcast data signal (the same data optical signal) from the base station device 200 is blocked by the other terminal device 100. As a result, there is a problem that the one terminal device 100 cannot receive the broadcast data signal from the base station device 200. Therefore, in this embodiment, this problem can be solved by having the terminal device 100 relay (repeat transmission) the broadcast communication.

[0094] 17 is a diagram for explaining the operation of the optical communication system 1 according to this embodiment. In the example shown in the figure, each terminal device 100 is formed in a spherical shape as a whole, and optical communication in all directions is possible.

[0095] When any of the multiple light receiving units 110 receives a broadcast data signal, the control unit 130 of the terminal device 100a controls at least one of the multiple light emitters 120 to relay the received broadcast data signal. By performing such relay transmission, it becomes possible to virtually extend the communication range of the base station device 200, making it easier for more terminal devices 100 to receive broadcast signals. Note that the terminal device 100a may not only relay the broadcast data signal, but also relay the broadcast communication reference signal and / or the control optical signal.

[0096] In this embodiment, when any of the multiple light receiving units 110 receives a broadcast data signal, the control unit 130 of the terminal device 100a controls the relay transmission to be performed using the light emitting unit 120 whose optical axis is oriented in a direction different from the arrival direction of the received broadcast data signal. For example, the control unit 130 of the terminal device 100a controls the relay transmission to be performed using the light emitting unit 120 located on the opposite side of the arrival direction of the received broadcast data signal. In this way, even if the terminal device 100a is located between the terminal device 100b and the base station device 200, the terminal device 100b can receive the broadcast data signal relayed by the terminal device 100a.

[0097] FIG. 18 is a diagram showing an example of an operation sequence related to broadcast communication according to this embodiment.

[0098] In step S201, the base station device 200 controls each light-emitting unit 220 to transmit a data optical signal (broadcast data signal) including broadcast data in a time slot for broadcast communication. One of the light-receiving units 110 of the terminal device 100a receives the broadcast data signal from the base station device 200.

[0099] In step S202, the control unit 130 of the terminal device 100a performs relay control so that the broadcast data signal received by the light receiving unit 110 in step S201 is transmitted from the light emitting unit 120 located opposite the light receiving unit 110. The control unit 130 of the terminal device 100a may control the light emitting unit 220 to transmit the broadcast data signal in a time slot for broadcast communication in the communication frame following the communication frame in which the light receiving unit 110 received the broadcast data signal in step S201. One of the light receiving units 110 of the terminal device 100b receives the broadcast data signal from the terminal device 100a.

[0100] The terminal device 100b may perform relay transmission in the same manner as the terminal device 100a. However, since relay transmission may continue indefinitely, an upper limit may be set on the number of relays. For example, in step S202, the terminal device 100a may notify the terminal device 100b, for example, by using a control optical signal, that the broadcast data signal has been relayed. Based on this notification, the terminal device 100b may decide not to relay the broadcast data signal from the terminal device 100a.

[0101] Alternatively, each terminal device 100 that performs relaying may transmit a broadcast data signal with a count value indicating the number of relays added. The terminal device 100 that receives the broadcast data signal may ascertain the number of relays from the count value, and may decide not to relay the broadcast data signal if the number of relays reaches a predetermined upper limit.

[0102] (4) Other embodiments In the above embodiment, an example has been described in which the base station device 200 is installed on the water surface. However, the base station device 200 may be installed on the bottom of the water, as shown in Fig. 19. A terminal device 100 moving underwater performs visible light communication with a base station device 200 located below (diagonally below) the terminal device 100. Alternatively, the base station device 200 may be installed on a wall surface underwater, as shown in Fig. 20. The terminal device 100 performs visible light communication with the base station device 200 while moving vertically underwater.

[0103] In the above-described embodiment, an example has been described in which the light-emitting and receiving unit 150 of the terminal device 100 and the light-emitting and receiving unit 250 of the base station device 200 are configured in a hemispherical shape. However, the terminal device 100 and / or the base station device 200 may be configured in an overall spherical shape (or, from another perspective, a mirror ball shape) as shown in FIG. 21 . For example, the terminal device 100 and / or the base station device 200 may form a polyhedron, each face of the polyhedron may form an optical communication unit, and a set of light-emitting elements and light-receiving elements may be arranged on each face. Alternatively, the terminal device 100 and / or the base station device 200 may be configured in an overall rod shape as shown in FIG. 22 . For example, the terminal device 100 and / or the base station device 200 may form a prism, each side of the prism may form an optical communication unit, and a set of light-emitting elements and light-receiving elements may be arranged on each side.

[0104] A program may be provided that causes a computer to execute each process performed by the terminal device 100 or the base station device 200. The program may be recorded on a computer-readable medium. Using the computer-readable medium, the program can be installed on a computer. Here, the computer-readable medium on which the program is recorded may be a non-transitory recording medium. The non-transitory recording medium is not particularly limited, and may be, for example, a recording medium such as a CD-ROM or a DVD-ROM. Furthermore, circuits that execute each process performed by the terminal device 100 or the base station device 200 may be integrated, and at least a part of the terminal device 100 or the base station device 200 may be configured as a semiconductor integrated circuit (chip set, SoC: System on a chip).

[0105] As used in this disclosure, the terms "based on" and "depending on / in response to" do not mean "based only on" or "depending only on," unless expressly stated otherwise. The term "based on" means both "based only on" and "based at least in part on." Similarly, the term "depending on" means both "depending only on" and "depending at least in part on." The terms "include," "comprise," and variations thereof do not mean including only the listed items, but may mean including only the listed items or including additional items in addition to the listed items. Additionally, the term "or," as used in this disclosure, is not intended to mean an exclusive or. Furthermore, any reference to elements using designations such as "first," "second," etc., as used in this disclosure does not generally limit the quantity or order of those elements. These designations may be used in this disclosure as a convenient method of distinguishing between two or more elements. Thus, a reference to a first and a second element does not imply that only two elements may be employed therein or that the first element must precede the second element in some way. In this disclosure, where articles are added by translation, such as a, an, and the in English, these articles shall include the plural unless the context clearly indicates otherwise.

[0106] The above describes the embodiments in detail with reference to the drawings, but the specific configuration is not limited to that described above, and various design changes can be made within the scope that does not deviate from the gist of the invention.

[0107] This application claims priority from Japanese Patent Application No. 2022-133722 (filed August 25, 2022), the entire contents of which are incorporated herein by reference.

[0108] (5) Supplementary Notes Additional notes will be given regarding the features of the above-described embodiment.

[0109] (Appendix 1) An optical communication system in which a terminal device and a base station device perform optical communication, The terminal device A plurality of light receiving units arranged with their optical axes facing in different directions; a control unit that, when receiving the same data optical signal simultaneously broadcast from a plurality of base station devices, performs a specification process to specify each light receiving unit that receives the same data optical signal; The control unit performs a synthesis process of synthesizing the received signals of the light receiving units identified by the identification process. Optical communication system.

[0110] (Appendix 2) The control unit of the terminal device identifies a light receiving unit that receives an interference light signal different from the same data light signal, and controls the interference light signal received by the identified light receiving unit not to be used in the combining process. 10. The optical communication system of claim 1.

[0111] (Appendix 3) The base station device A plurality of light emitting units arranged with their optical axes facing in different directions; a control unit that controls the plurality of light-emitting units to transmit a reference optical signal for broadcast communication and / or a control optical signal indicating a time slot for broadcast communication when the same data optical signal is broadcast from the plurality of light-emitting units. 3. The optical communication system according to claim 1 or 2.

[0112] (Appendix 4) The control unit of the terminal device, in the identification process, identifies each light receiving unit that receives the reference optical signal from the plurality of base station devices. 4. The optical communication system of claim 3.

[0113] (Appendix 5) When any one of the plurality of optical receivers receives the control optical signal, the control unit of the terminal device controls the optical receivers to receive the same data optical signal in the time slot specified by the received control optical signal. 5. The optical communication system according to claim 3 or 4.

[0114] (Appendix 6) each of the plurality of light-emitting units of the base station device transmits the same data optical signal in a plurality of colors with different wavelengths; Each of the plurality of light receiving units of the terminal device receives the same data optical signal in at least one of the plurality of colors. 6. An optical communication system according to any one of appendixes 3 to 5.

[0115] (Appendix 7) each of the plurality of light-emitting units of the base station device includes a plurality of light-emitting elements provided corresponding to the plurality of colors; The control unit of the base station device controls the plurality of light-emitting elements to transmit the same data optical signal in the plurality of colors. 7. The optical communication system of claim 6.

[0116] (Appendix 8) Each of the plurality of light receiving units of the terminal device includes a plurality of light receiving elements provided with color filters of respective colors. 8. The optical communication system of claim 7.

[0117] (Appendix 9) Each of the plurality of light receiving units of the terminal device includes a light receiving element and a band pass filter that separates signals received by the light receiving element by color. 8. The optical communication system of claim 7.

[0118] (Appendix 10) the terminal device further includes a plurality of light-emitting units arranged with their optical axes facing different directions, When any one of the plurality of light receiving units receives the same data optical signal, the control unit of the terminal device controls at least one of the plurality of light emitting units to relay and transmit the received data optical signal. 10. An optical communication system according to any one of claims 1 to 9.

[0119] (Appendix 11) When any one of the plurality of light receiving units receives the same data optical signal, the control unit of the terminal device controls the relay transmission to be performed using a light emitting unit whose optical axis is directed in a direction different from the direction of arrival of the received data optical signal. 11. The optical communication system of claim 10.

[0120] (Appendix 12) The terminal device and the base station device perform the optical communication underwater. 12. An optical communication system according to any one of claims 1 to 11.

[0121] (Appendix 13) The terminal device and the base station device perform the optical communication using visible light. 13. An optical communication system according to any one of claims 1 to 12.

[0122] (Appendix 14) A terminal device that performs optical communication with a base station device, A plurality of light receiving units arranged with their optical axes facing in different directions; a control unit that, when receiving the same data optical signal simultaneously broadcast from a plurality of base station devices, performs a specification process to specify each light receiving unit that receives the same data optical signal; The control unit performs a synthesis process of synthesizing the received signals of the light receiving units identified by the identification process. Terminal device.

[0123] (Appendix 15) A base station device that performs optical communication with a terminal device, A plurality of light emitting units arranged with their optical axes facing in different directions; a control unit that controls the plurality of light-emitting units to transmit a reference optical signal for broadcast communication and / or a control optical signal indicating a time slot for broadcast communication when the same data optical signal is broadcast from the plurality of light-emitting units. Base station equipment. [Explanation of symbols]

[0124] 1: Optical communication system 10: Network 100: Terminal device 101: Optical Communications Department 110: Light receiving section 111: Light receiving element 112: Receiver 120: Light emitting part 121: Light-emitting element 122: Transmitter 130: Control unit 131: Processor 132: Memory 140: Movement mechanism 150: Light receiving and emitting unit 160: Main body 200:Base station equipment 201: Optical Communications Department 210: Light receiving part 211: Photodetector 212: Receiver 220: Light-emitting part 221: Light-emitting element 222: Transmitter 230: Control unit 231: Processor 232: Memory 240: Backhaul communication unit 241: Network Communications Department 242: Base station communication unit 250: Light receiving and emitting unit 260: Main body 1121: Bandpass filter

Claims

1. An optical communication system in which a terminal device and a base station device perform optical communication, The terminal device A plurality of light receiving units arranged with their optical axes facing in different directions; a control unit that, when receiving the same data optical signal simultaneously broadcast from a plurality of base station devices, performs a specification process to specify each light receiving unit that receives the same data optical signal; the control unit performs a synthesis process of synthesizing the reception signals of the light receiving units identified by the identification process, In the case of unicast communication, the control unit performs a combining process to combine signals received by each light receiving unit that receives a data optical signal addressed to the terminal device from a specific base station device that is a serving base station, and to control the combining process to prevent data optical signals transmitted from base station devices other than the specific base station device from being combined. Optical communication system.

2. The control unit of the terminal device identifies a light receiving unit that receives an interference light signal different from the same data light signal, and controls the interference light signal received by the identified light receiving unit not to be used in the combining process.

2. The optical communication system according to claim 1.

3. The base station device A plurality of light emitting units arranged with their optical axes facing in different directions; a control unit that controls the plurality of light-emitting units to transmit a reference optical signal for broadcast communication and / or a control optical signal indicating a time slot for broadcast communication when the same data optical signal is broadcast from the plurality of light-emitting units.

2. The optical communication system according to claim 1.

4. The control unit of the terminal device, in the identification process, identifies each light receiving unit that receives the reference optical signal from the plurality of base station devices.

4. The optical communication system according to claim 3.

5. When any one of the plurality of optical receivers receives the control optical signal, the control unit of the terminal device controls the optical receivers to receive the same data optical signal in the time slot specified by the received control optical signal.

4. The optical communication system according to claim 3.

6. each of the plurality of light-emitting units of the base station device transmits the same data optical signal in a plurality of colors with different wavelengths; Each of the plurality of light receiving units of the terminal device receives the same data optical signal in at least one of the plurality of colors.

4. The optical communication system according to claim 3.

7. each of the plurality of light-emitting units of the base station device includes a plurality of light-emitting elements provided corresponding to the plurality of colors; The control unit of the base station device controls the plurality of light-emitting elements to transmit the same data optical signal in the plurality of colors.

7. The optical communication system according to claim 6.

8. Each of the plurality of light receiving units of the terminal device includes a plurality of light receiving elements provided with color filters of respective colors.

8. The optical communication system according to claim 7.

9. Each of the plurality of light receiving units of the terminal device includes a light receiving element and a band pass filter that separates signals received by the light receiving element by color.

8. The optical communication system according to claim 7.

10. the terminal device further includes a plurality of light-emitting units arranged with their optical axes facing different directions, When any one of the plurality of light receiving units receives the same data optical signal, the control unit of the terminal device controls at least one of the plurality of light emitting units to relay and transmit the received data optical signal.

2. The optical communication system according to claim 1.

11. When any one of the plurality of light receiving units receives the same data optical signal, the control unit of the terminal device controls the relay transmission to be performed using a light emitting unit whose optical axis is directed in a direction different from the direction of arrival of the received data optical signal.

11. The optical communication system according to claim 10.

12. The terminal device and the base station device perform the optical communication underwater.

12. An optical communication system according to any one of claims 1 to 11.

13. The terminal device and the base station device perform the optical communication using visible light.

12. An optical communication system according to any one of claims 1 to 11.

14. A terminal device that performs optical communication with a base station device, A plurality of light receiving units arranged with their optical axes facing in different directions; a control unit that, when receiving the same data optical signal simultaneously broadcast from a plurality of base station devices, performs a specification process to specify each light receiving unit that receives the same data optical signal; the control unit performs a synthesis process of synthesizing the reception signals of the light receiving units identified by the identification process, In the case of unicast communication, the control unit performs a combining process to combine signals received by each light receiving unit that receives a data optical signal addressed to the terminal device from a specific base station device that is a serving base station, and to control the combining process to prevent data optical signals transmitted from base station devices other than the specific base station device from being combined. Terminal device.

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