Optical communication device, optical communication method, and optical communication program

Abstract

This base station device comprises: a plurality of light emitting elements; and a control unit which divides the plurality of light emitting elements into a plurality of clusters such that each cluster is composed of one or more light emitting elements. The control unit modifies the combination of the light emitting elements constituting each cluster in a time-division manner, and controls the plurality of light emitting elements so that the light emitting elements in each cluster transmits the same optical signal in each time interval.

Description

[Technical Field]

[0001] The present disclosure relates to an optical communication device, an optical communication method, and an optical communication program. [Background technology]

[0002] For example, in underwater communications, an optical communication system that uses visible light as a transmission medium is known (see, for example, Patent Document 1). Because visible light has high directionality, in conventional optical communication systems, it is common for the transmitting and receiving sides to communicate facing each other, with the optical communication devices on each side being fixed.

[0003] Furthermore, in an optical communication system, a technique has been proposed for using a plurality of light-emitting elements in a transmitting optical communication device, in which a reference optical signal is transmitted from each light-emitting element in a time-division manner (see Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 4-103232 [Patent Document 2] Special Publication No. 2020-532899 [Overview of the Initiative]

[0005] An optical communication device according to a first aspect comprises a plurality of light-emitting elements and a control unit that divides the plurality of light-emitting elements into a plurality of clusters so that each cluster is composed of one or more light-emitting elements, and the control unit changes the combination of light-emitting elements that make up each cluster in a time-division manner and controls the plurality of light-emitting elements so that the light-emitting elements in each cluster transmit the same optical signal within each time interval.

[0006] A second embodiment of the optical communication method is an optical communication method used in an optical communication device equipped with a plurality of light-emitting elements, comprising the steps of: dividing the plurality of light-emitting elements into a plurality of clusters such that each cluster is composed of one or more light-emitting elements; changing the combination of light-emitting elements constituting each cluster in a time-division manner; and controlling the plurality of light-emitting elements so that the light-emitting elements in each cluster transmit the same optical signal within each time interval.

[0007] The optical communication program according to the third embodiment causes an optical communication device having a plurality of light-emitting elements to perform the following steps: divide the plurality of light-emitting elements into a plurality of clusters such that each cluster consists of one or more light-emitting elements; change the combination of light-emitting elements constituting each cluster in a time-division manner; and control the plurality of light-emitting elements such that the light-emitting elements in each cluster transmit the same optical signal within each time interval. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a diagram illustrating a configuration example of an optical communication system according to an embodiment. [Figure 2] FIG. 1 is a diagram illustrating an example of the configuration of a base station device according to an embodiment. [Figure 3] FIG. 1 is a diagram illustrating an example of the external configuration of a base station device according to an embodiment. [Figure 4] FIG. 2 is a diagram illustrating an example of the configuration of a terminal device according to the embodiment. [Figure 5] FIG. 1 is a diagram illustrating an example of the external configuration of a terminal device according to an embodiment. [Figure 6] FIG. 10 is a diagram illustrating an example of synthesis transmission according to the embodiment. [Figure 7] FIG. 10 is a diagram illustrating an example of synthesis transmission according to the embodiment. [Figure 8] FIG. 10 is a diagram illustrating an example of synthesis transmission according to the embodiment. [Figure 9] FIG. 10 is a diagram illustrating an example of the operation of a base station device according to an embodiment. [Figure 10] FIG. 10 is a diagram illustrating an example of the operation of a base station device according to an embodiment. [Figure 11]FIG. 10 is a diagram illustrating an example of the operation of a base station device according to an embodiment. [Figure 12] This figure shows an example of a communication sequence of an optical communication system according to the embodiment. [Figure 13] This figure shows a first example of the configuration of a communication frame according to the embodiment. [Figure 14] This figure shows a second example of the configuration of a communication frame according to the embodiment. [Figure 15] This figure shows a third example of the communication frame configuration according to the embodiment. [Figure 16] This figure shows a fourth example of the communication frame configuration according to the embodiment. [Figure 17] This figure shows a fifth example of the communication frame configuration according to the embodiment. [Figure 18] This is a diagram illustrating another embodiment. [Figure 19] This is a diagram illustrating another embodiment. [Figure 20] This is a diagram illustrating another embodiment. [Figure 21] This is a diagram illustrating another embodiment. [Figure 22] This is a diagram illustrating another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] In visible light communication, combined transmission, which involves transmitting the same optical signal from multiple light-emitting elements, is effective. Combined transmission allows for effects such as extending the communication range by combining the optical signals transmitted by multiple light-emitting elements. However, there is room for improvement in optical communication systems that employ combined transmission in terms of increasing the communication capacity (i.e., system capacity) of the optical communication system.

[0010] Therefore, this disclosure aims to improve the communication capacity of optical communication systems that use composite transmission.

[0011] An optical communication system according to an embodiment will be described with reference to the drawings. In the drawings, identical or similar parts are denoted by the same or similar reference numerals.

[0012] The optical communication system according to the embodiment is a system that performs visible light communication. Furthermore, the optical communication system according to the embodiment is a system that performs underwater optical communication. However, the optical communication system is not limited to a system that performs underwater optical communication; it may also be a system that performs optical communication on land (or in space).

[0013] (1) Example of optical communication system configuration First, an example of the configuration of the optical communication system according to the embodiment will be described. Figure 1 is a diagram showing an example of the configuration of the optical communication system 1 according to the embodiment.

[0014] 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 the example in Figure 1.

[0015] 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 a network via a backhaul line. The backhaul line may be a wireless line or 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 surveys are conducted using the terminal device 100.

[0016] 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 movable underwater. Each terminal device 100 performs visible light communication (specifically, underwater visible light communication) with the base station device 200. In other words, the base station device 200 is a serving base station for each terminal device 100.

[0017] Each terminal device 100 may be equipped with a sensor such as an image sensor and generate sensor data. For example, each terminal device 100 may transmit uplink (UL) data including sensor data to the base station device 200 via visible light communication. Each terminal device 100 may receive downlink (DL) data including instruction data from the base station device 200 via visible light communication. Each terminal device 100 may perform movement and sensing operations (such as taking pictures) based on the instruction data.

[0018] In this embodiment, the base station device 200 performs combined transmission in the downlink, transmitting the same optical signal from multiple light-emitting elements. Combined transmission provides effects such as extending the communication range by combining the optical signals transmitted by multiple light-emitting elements. The following description will mainly focus on combined transmission in the downlink. However, the terminal device 100 may also perform combined transmission in the uplink.

[0019] In the example shown in Figure 1, the base station device 200 accommodates two terminal devices 100. By increasing the number of terminal devices 100 accommodated by the base station device 200, the system capacity of the optical communication system 1 can be improved. Furthermore, the base station device 200 needs to follow the movement of each terminal device 100. The base station device 200 selects the combination of light-emitting elements to be used for combined transmission according to the status of each terminal device 100.

[0020] (2) Example of base station equipment configuration Next, a configuration example of the base station device 200 according to the embodiment will be described.

[0021] (2.1) Example of base station device block configuration Figure 2 shows an example configuration of a base station device 200 according to an embodiment. The base station device 200 includes a light-emitting unit 210, a light-receiving unit 220, a control unit 230, and a backhaul communication unit 240. The base station device 200 may also have a battery to supply the power necessary for the operation of the base station device 200.

[0022] The light-emitting unit 210 transmits an optical signal to the terminal device 100 under the control of the control unit 230. The light-emitting unit 210 has a plurality of light-emitting elements 211 (211#0, 211#1, ...) and a transmitter 212.

[0023] Each light emitting element 211 may be a laser diode or a light emitting diode. Each light emitting element 211 converts an electrical signal (transmission signal) output by the transmitter 212 for visible light communication into an optical signal and transmits the optical signal.

[0024] The transmitter 212 may be composed of an FPGA (Field Programmable Gate Array) and / or a SoC (System-on-a-chip). The transmitter 212 performs signal processing on the transmission signal output by the control unit 230, converts the processed signal, and outputs it to the light-emitting element 211. In this embodiment, each of the multiple light-emitting elements 211 has a different optical axis orientation. That is, each of the multiple light-emitting elements 211 has a different direction of directivity (transmission directivity).

[0025] The light-receiving unit 220 receives optical signals from the terminal device 100. The light-receiving unit 220 has a plurality of light-receiving elements 221 (221#0, 221#1, ...) and a receiver 222.

[0026] Each light receiving element 221 may be a photodiode. Each light receiving element 221 receives an optical signal, converts the received optical signal into an electrical signal (received signal), and outputs the received signal to the receiver 222.

[0027] The receiver 222 may be configured with an FPGA and / or an SoC. At least a part of the receiver 222 may be configured integrally with the transmitter 212. The receiver 222 converts the received signal output by the light receiving element 221, performs signal processing on the converted received signal, and outputs the processed signal to the control unit 230.

[0028] In the embodiment, the light receiving elements 221 are also provided in a one-to-one correspondence with the light emitting elements 211. Specifically, the light receiving elements 221 have directivity (reception directivity) in the same direction as the corresponding light emitting elements 211. That is, a plurality of pairs of the light emitting elements 211 and the light receiving elements 221 transmit optical signals in different directions and receive optical signals from different directions.

[0029] The control unit 230 controls the overall operation of the base station device 200. For example, the control unit 230 controls the light emitting unit 210 and the light receiving unit 220. 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. The digital signal processor performs modulation / demodulation and encoding / decoding of digital signals. The CPU executes programs stored in the memory to perform various processes.

[0030] The backhaul communication unit 240 performs backhaul 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 a network (e.g., a core network) and an inter-base station communication unit 242 that performs inter-base station communication with adjacent base stations.

[0031] In the base station device 200 configured in this manner, the control unit 230 divides the plurality of light-emitting elements 211 into a plurality of clusters so that each cluster is composed of one or more light-emitting elements 211. A cluster is a light-emitting element group composed of one or more light-emitting elements 211. The control unit 230 changes the combination of the light-emitting elements 211 that constitute each cluster in a time-division manner. Furthermore, the control unit 230 controls the light-emitting elements 211 in each cluster so that they transmit the same optical signal (i.e., composite transmission) within each time interval.

[0032] In this way, by dividing the multiple light-emitting elements 211 into multiple clusters and configuring the system to perform combined transmission for each cluster, it becomes easy to perform combined transmission to multiple terminal devices 100 simultaneously. Furthermore, it becomes easy to perform combined transmission from multiple clusters in various directions. Therefore, it is possible to increase the number of terminal devices 100 that can be accommodated by the base station device 200 that performs combined transmission.

[0033] Furthermore, by changing the combination of light-emitting elements 211 that constitute each cluster in a time-division manner, it becomes possible to change the combination of light-emitting elements used for combined transmission according to the status of each terminal device 100, thereby enabling adaptation to the movement of the terminal devices 100.

[0034] In this embodiment, each time interval in which a composite transmission is performed is a time interval included in the downlink communication period. In the following, a time interval may be referred to as a time slot (or slot), but a time interval may also be referred to as a subframe. The control unit 230 assigns each cluster to one or more terminal devices 100. This makes it possible to perform a composite transmission for each time interval while changing the cluster (i.e., changing the combination of light-emitting elements 211 that constitute the cluster) for each time interval within the downlink communication period.

[0035] The light-receiving unit 220 (specifically, the light-receiving element 221) may receive a feedback optical signal from the terminal device 100. Based on the feedback optical signal from the terminal device 100, the control unit 230 determines the combination of light-emitting elements 211 that constitute the cluster to be assigned to the terminal device 100. This makes it possible to assign an appropriate cluster (combination of light-emitting elements 211) to each terminal device 100. In addition, the control unit 230 may determine the assignment pattern that maximizes the system capacity from among all combination patterns of light-emitting elements 211 during the resource allocation (scheduling) process. Alternatively, the control unit 230 may determine the assignment pattern that maximizes the system capacity from among a predetermined set of combination patterns of light-emitting elements 211.

[0036] The feedback optical signal from the terminal device 100 may include information indicating a combination of light-emitting elements 211 selected by the terminal device 100. The information may include an identifier of the cluster selected by the terminal device 100 and / or an identifier of each light-emitting element 211 selected by the terminal device 100. This makes it easier to assign an appropriate cluster to each terminal device 100.

[0037] The control unit 230 may multiplex multiple terminal devices 100 assigned the same cluster within one time interval using code division multiple access (CDMA). This makes it possible to assign the same cluster to multiple terminal devices 100 within one time interval, making it easier to increase the number of terminal devices 100 that can be accommodated by the base station device 200. When multiplexing optical signals using CDMA, the control unit 230 may perform spreading processing on the optical signal addressed to the terminal device 100 using a code (spreading code) assigned to the terminal device 100.

[0038] The control unit 230 may control the light-emitting elements 211 so that the light-emitting elements 211 in each cluster transmit a cluster-specific reference optical signal (hereinafter referred to as a "cluster-specific reference signal"). The cluster-specific reference signal is an optical signal including a signal sequence that differs for each cluster. The reference optical signal is an optical signal used for propagation path estimation and received power measurement (hereinafter simply referred to as a "measurement process") in the terminal device 100. By transmitting the cluster-specific reference signal from the light-emitting elements 211 in each cluster, the terminal device 100 can perform measurement process on a cluster-by-cluster basis.

[0039] The feedback optical signal received by the light receiving unit 220 (specifically, the light receiving element 221) from the terminal device 100 includes measurement information for each cluster obtained by the terminal device 100 performing measurement processing on the cluster-specific reference signal. This allows the base station device 200 to grasp the reception state in the terminal device 100 for each cluster based on the feedback optical signal. The measurement information may be measurement report information including reference signal reception power and / or reference signal reception quality. The measurement information may also be channel state information (CSI).

[0040] The control unit 230 may control the plurality of light-emitting elements 211 to transmit the cluster-specific reference signals of each cluster in a time interval that is not included in the downlink communication period in a time division manner. This allows the terminal device 100 to efficiently perform measurement processing for each cluster in the time interval, making it easier to grasp the reception state of each cluster.

[0041] The control unit 230 may control the plurality of light-emitting elements 211 so that each light-emitting element 211 in each cluster transmits a reference optical signal specific to the light-emitting element (hereinafter referred to as a "light-emitting element-specific reference signal"). The light-emitting element-specific reference signal is an optical signal including a signal sequence that differs for each light-emitting element 211. By each light-emitting element 211 transmitting the light-emitting element-specific reference signal, the terminal device 100 can perform measurement processing on a light-emitting element basis.

[0042] The feedback optical signal received by the light receiving unit 220 (specifically, the light receiving element 221) from the terminal device 100 may include measurement information for each light emitting element obtained by the terminal device 100 performing measurement processing on a light emitting element-specific reference signal. The control unit 230 may derive measurement information for each cluster from the measurement information for each light emitting element. For example, the control unit 230 classifies the measurement information for each light emitting element into corresponding clusters and calculates measurement information for each cluster from the classified measurement information. This allows the base station device 200 to grasp the reception state of the terminal device 100 for each cluster based on the feedback optical signal, without using a cluster-specific reference signal.

[0043] The control unit 230 may control the plurality of light-emitting elements 211 to transmit the cluster-specific reference signal and the light-emitting element-specific reference signal in a time interval not included in the downlink communication period in a time division manner. This allows the terminal device 100 to efficiently perform measurement processing for each cluster and each light-emitting element within the time interval, making it easier to grasp the reception state of each cluster and the reception state of each light-emitting element.

[0044] (2.2) Example of base station equipment external configuration Figure 3 shows an example of the external configuration of the base station device 200 according to this embodiment.

[0045] The base station device 200 has a hemispherical light-emitting and receiving unit 250 and a main body 260 connected to the light-emitting and receiving unit 250. However, the base station device 200 may be configured to be spherical as a whole. The light-emitting and receiving unit 250 has a plurality of light-emitting and receiving areas 251 that are dispersedly arranged. Each light-emitting and receiving area 251 is provided with a pair of a light-emitting element 211 and a light-receiving element 221. This configuration makes it easy for the base station device 200 to perform visible light communication with terminal devices 100 in various directions.

[0046] 3, the hemispherical light emitting and receiving unit 250 has a total of 19 light emitting and receiving areas 251#0 to 251#18. That is, the base station device 200 has a total of 19 light emitting elements 211#0 to 211#18, and a total of 19 light receiving elements 221#0 to 221#18.

[0047] (3) Example of terminal device configuration Next, an example of the configuration of the terminal device 100 according to this embodiment will be described.

[0048] (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 an embodiment. The terminal device 100 includes a light-emitting unit 110, a light-receiving unit 120, and a control unit 130. The terminal device 100 may include a battery for supplying power necessary for the operation of the terminal device 100. The terminal device 100 may include a movement mechanism (for example, a motor and a screw) used to move the terminal device 100.

[0049] The light-emitting unit 110 transmits an optical signal to the base station device 200 under the control of the control unit 130. The light-emitting unit 110 has a plurality of light-emitting elements 111 (111#0, 111#1, ...) and a transmitter 112.

[0050] Each light-emitting element 111 may be a laser diode or a light-emitting diode. Each light-emitting element 111 converts an electrical signal (transmission signal) output by the transmitter 112 for visible light communication into an optical signal, and transmits the optical signal.

[0051] The transmitter 112 may be configured as an FPGA and / or SoC. The transmitter 112 performs signal processing on the transmission signal output by the control unit 130, converts the processed signal, and outputs it to the light-emitting element 111. In this embodiment, each of the multiple light-emitting elements 111 has a different optical axis orientation. That is, each of the multiple light-emitting elements 111 has a different direction of directivity (transmission directivity).

[0052] The light receiving unit 120 receives an optical signal from the base station device 200. The light receiving unit 120 includes a plurality of light receiving elements 121 (121#0, 121#1, . . . ) and a receiver 122.

[0053] Each of the light receiving elements 121 may be a photodiode. Each of the light receiving elements 121 receives an optical signal, converts the received optical signal into an electrical signal (received signal), and outputs the received signal to the receiver 122.

[0054] The receiver 122 may be configured with an FPGA and / or an SoC. At least a part of the receiver 122 may be configured integrally with the transmitter 112. The receiver 122 converts the received signal output by the light receiving element 121, performs signal processing on the converted received signal, and outputs the processed signal to the control unit 130.

[0055] In this embodiment, the light-receiving element 121 is provided in a one-to-one pair with the light-emitting element 111. Specifically, the light-receiving element 121 has the same directionality (receiving directionality) as its corresponding light-emitting element 111. That is, multiple pairs of light-emitting elements 111 and light-receiving elements 121 each transmit optical signals in different directions and receive optical signals from different directions.

[0056] The control unit 130 controls the overall operation of the terminal device 100. For example, the control unit 130 controls the light-emitting unit 110 and the light-receiving unit 120. 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 for 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, and decoding of digital signals. The CPU executes programs stored in memory and performs various processes.

[0057] In the terminal device 100 configured in this way, the light receiving unit 120 (specifically, the light receiving element 121) receives the optical signal transmitted from the base station device 200 by composite transmission within the time interval allocated to the terminal device 100. 130 The light receiving unit 120 demodulates and decodes the optical signal. If the optical signal is multiplexed using code division multiplexing, the control unit 230 may perform despreading processing on the optical signal received by the light receiving unit 120 using the code (spreading code) assigned to the terminal device 100.

[0058] The light-receiving unit 120 (specifically, the light-receiving element 121) may receive a cluster-specific reference signal and / or a light-emitting element-specific reference signal from the base station device 200. The control unit 130 may perform measurement processing using the cluster-specific reference signal and / or the light-emitting element-specific reference signal to generate measurement information. The control unit 130 may control the light-emitting unit 110 to transmit a feedback optical signal containing the measurement information to the base station device 200.

[0059] The control unit 130 may select a combination of light-emitting elements 211 that the base station device 200 allocates to the terminal device 100 based on the result of the measurement process. 130 The light emitting unit 110 may be controlled to transmit, to the base station apparatus 200, a feedback optical signal including information indicating the combination of the selected light emitting elements 211.

[0060] (3.2) Example of external configuration of terminal device Figure 5 shows an example of the external configuration of the terminal device 100 according to this embodiment.

[0061] The terminal device 100 has a hemispherical light-emitting and receiving unit 150 and a main body 160 connected to the light-emitting and receiving unit 150. However, the terminal device 100 may be configured to be spherical as a whole. The light-emitting and receiving unit 150 has a plurality of light-emitting and receiving areas 151 that are dispersedly arranged. Each light-emitting and receiving area 151 is provided with a pair of a light-emitting element 111 and a light-receiving element 121. This configuration makes it easy for the terminal device 100 to perform visible light communication with base station devices 200 in various directions.

[0062] 5, the hemispherical light emitting and receiving unit 150 has a total of seven light emitting and receiving areas 151#0 to 151#6. That is, the terminal device 100 has a total of seven light emitting elements 111#0 to 111#6, and has a total of seven light receiving elements 121#0 to 121#6.

[0063] (4) Example of composite transmission Next, an example of combining transmission according to the embodiment will be described. Fig. 6 is a diagram showing an example of combining transmission according to the embodiment. In the example of Fig. 6, a cross section of a base station device 200 is shown in a simplified manner.

[0064] In the base station device 200, the multiple light-emitting elements 211 are arranged such that as the distance between one light-emitting element 211 and another light-emitting element 211 increases, the angle formed between the optical axis of the one light-emitting element 211 and the optical axis of the other light-emitting element 211 increases. The angle formed between the optical axis of the light-emitting element 211#0 and the optical axis of the light-emitting element 211#7 that is not adjacent to the light-emitting element 211#0 is larger than the angle formed between the optical axis of the light-emitting element 211#0 and the optical axis of the light-emitting element 211#1 that is adjacent to the light-emitting element 211#0.

[0065] When one cluster is configured with two or more light-emitting elements 211, the base station device 200 (control unit 230) configures the cluster with adjacent light-emitting elements 211. In the example of Fig. 6, the base station device 200 configures a cluster with adjacent light-emitting elements 211#1 and 211#7, and performs combined transmission from the cluster to the terminal device 100. The visible light emitted by the light-emitting element 211#1 (i.e., the optical signal transmitted by the light-emitting element 211#1) and the visible light emitted by the light-emitting element 211#7 (i.e., the optical signal transmitted by the light-emitting element 211#7) are the same optical signal, and are partially combined and constructively coupled in water, which makes it possible to extend the communication distance.

[0066] Here, we consider a case where the number of terminal devices 100 that the base station device 200 can accommodate is increased by applying code division multiple access (CDMA) to the downlink. Normally, when CDMA is applied only to the downlink, detailed transmission power control between terminal devices, as in uplink CDMA, is not required, and therefore downlink CDMA is considered to be easily realized. Note that uplink CDMA requires uplink transmission power control to equalize the reception power of optical signals received by the base station device 200 from each terminal device 100.

[0067] Assuming that downlink CDMA is applied, as shown in Fig. 7, the base station device 200 performs combined transmission using multiple light-emitting elements (light-emitting elements 211#0, #1, #2) to the terminal device 100a, and single transmission using a single light-emitting element (light-emitting element 211#1) to the terminal device 100b. In this case, since the received power is greater in combined transmission than in single transmission, a large difference in received power occurs between the terminal device 100a and the terminal device 100b, which may hinder decoding by despreading processing. Specifically, since the terminal device 100b receives an interference wave that is larger than the desired wave by the amount of the light-emitting elements 211#0 and #2, there is a risk that the desired wave will be buried in the interference wave.

[0068] As shown in Figure 8, it is believed that the above-mentioned problems can be solved by aligning the light-emitting elements used for combined transmission between the code-division multiplexed terminal devices 100a and 100b. However, this may lead to a decrease in system capacity because it becomes impossible to flexibly combine light-emitting elements in response to the movement of individual terminal devices 100. Specifically, system capacity may decrease by consuming light-emitting elements 211#0,2 that could have been allocated to other terminals. In addition, system capacity may decrease due to increased interference with other terminals to which adjacent light-emitting elements #3,4,5,6 have been allocated. Furthermore, system capacity may decrease because the degree of freedom in selecting the optimal light-emitting element 211 in accordance with the movement of each terminal decreases.

[0069] In this embodiment, the base station device 200 switches the combination of light-emitting elements 211 used for composite transmission in a time-division manner, thereby realizing the switching of light-emitting elements when the terminal device 100 moves by changing the allocated time slot. Specifically, the base station device 200 according to this embodiment divides a plurality of light-emitting elements 211 into a plurality of clusters such that each cluster consists of one or more light-emitting elements 211. The base station device 200 changes the combination of light-emitting elements 211 constituting each cluster in a time-division manner, and transmits the same optical signal from the light-emitting elements 211 in each cluster within each time interval.

[0070] This solves the problems described above and improves system capacity. Although the problems of applying CDMA to the downlink have been explained, in this embodiment, it is not necessary to apply CDMA to the downlink. The base station device 200 may switch whether or not to apply CDMA depending on the traffic conditions of the downlink.

[0071] (5) Example of base station equipment operation Next, an example of the operation of the base station device 200 according to the embodiment will be described. Figures 9 to 11 are diagrams showing an example of the operation of the base station device 200 according to the embodiment. In Figures 9 to 11, each cluster is distinguished by hatching.

[0072] 9, in downlink time slot (DL slot) #0, the base station device 200 divides a plurality of light emitting elements 211 into a plurality of clusters so that each cluster is composed of one or more light emitting elements 211. In the example of FIG. 9, the base station device 200 First cluster: one light-emitting element 211#0 Second cluster: three light-emitting elements 211#1, #7, and #18 Third cluster: three light-emitting elements 211#2, #8, and #9 Fourth cluster: three light-emitting elements 211#3, #10, and #11 Fifth cluster: three light-emitting elements 211#4, #12, and #13 Sixth cluster: three light-emitting elements 211#5, #14, and #15 Seventh cluster: three light-emitting elements 211#6, #17, # 16 Cluster division is performed in this way.

[0073] Since each cluster is composed of adjacent light emitting elements 211, the transmission direction of the optical signal of each cluster can be made different from the transmission direction of the optical signal of the other clusters. When one cluster is assigned to one terminal device 100, the base station device 200 can transmit simultaneously to seven terminal devices 100 by space division multiple access (SDMA). By also using CDMA, the base station device 200 can transmit simultaneously to even more terminal devices 100.

[0074] The base station apparatus 200 transmits the first to second DL slots in DL slot #0. 7 The same optical signal is transmitted from each cluster of the cluster. For example, the base station device 200 performs combined transmission to transmit the same optical signal from three light-emitting elements 211#1, #7, and #18 to one or more terminal devices 100 assigned to the second cluster. Similarly, the base station device 200 performs combined transmission to transmit the same optical signal from three light-emitting elements 211#2, #8, and #9 to one or more terminal devices 100 assigned to the third cluster. The same applies to the other clusters.

[0075] As shown in Fig. 10, in DL slot #1 following DL slot #0, the base station device 200 changes the combination of light-emitting elements 211 that make up each cluster. In the example of Fig. 10, the base station device 200 First cluster: one light-emitting element 211#0 Second cluster: two light-emitting elements 211#7 and #8 Third cluster: Four light-emitting elements 211#2, #3, #9, #10 Fourth cluster: two light-emitting elements 211#11 and #12 Fifth cluster: Four light-emitting elements 211#4, #5, #13, #14 Sixth cluster: two light-emitting elements 211#15 and #16 Cluster 7: The cluster is changed to four light-emitting elements 211#1, #6, #17, and #18.

[0076] The base station equipment 200 has, in DL slot #1, the first to the 7 The same optical signal is transmitted from each cluster of the cluster. For example, the base station device 200 performs combined transmission to transmit the same optical signal from two light-emitting elements 211#7 and #8 to one or more terminal devices 100 assigned to the second cluster. Similarly, the base station device 200 performs combined transmission to transmit the same optical signal from four light-emitting elements 211#2, #3, #9, and #10 to one or more terminal devices 100 assigned to the third cluster. The same applies to the other clusters.

[0077] As shown in Fig. 11, in DL slot #2 following DL slot #1, the base station device 200 changes the combination of light-emitting elements 211 that make up each cluster. In the example of Fig. 11, the base station device 200 First cluster: one light-emitting element 211#0 Second cluster: 4 light-emitting elements 211#1, #2, #7, #8 Third cluster: two light-emitting elements 211#9 and #10 Cluster 4: Four light-emitting elements 211#3, #4, #11, #12 Fifth cluster: two light-emitting elements 211#13 and #14 Sixth cluster: four light-emitting elements 211#5, #6, #15, and #16 Seventh cluster: The cluster is changed to two light emitting elements 211 #17 and #18.

[0078] In DL slot #2, the base station apparatus 200 7 The same optical signal is transmitted from each cluster of the cluster. For example, the base station device 200 performs combined transmission to transmit the same optical signal from four light-emitting elements 211#1, #2, #7, and #8 to one or more terminal devices 100 assigned to the second cluster. Similarly, the base station device 200 performs combined transmission to transmit the same optical signal from two light-emitting elements 211#9 and #10 to one or more terminal devices 100 assigned to the third cluster. The same applies to the other clusters.

[0079] The base station device 200 may allocate only one of the three DL slots, DL slots #0 to #2, to one terminal device 100. Alternatively, the base station device 200 may allocate two or more of the three DL slots, DL slots #0 to #2, to one terminal device 100.

[0080] (6) Example of a communication sequence Next, an example of a communication sequence of the optical communication system 1 according to the embodiment will be described. Fig. 12 is a diagram showing an example of a communication sequence of the optical communication system 1 according to the embodiment. However, the order of steps in this sequence is just an example, and the order of steps may be changed as appropriate.

[0081] In step S101, the base station device 200 transmits a reference optical signal. The reference optical signal is a cluster-specific reference signal and / or a light-emitting element-specific reference signal. The terminal device 100 receives the reference optical signal from the base station device 200.

[0082] In step S102, the terminal device 100 performs a measurement process on the reference optical signal received in step S101 from the base station device 200. For example, the terminal device 100 uses the reference optical signal received from the base station device 200 to perform propagation path estimation and / or reception power measurement (which may be reception quality measurement).

[0083] In step S103, the terminal device 100 generates information to be fed back to the base station device 200 based on the results of the measurement processing in step S102. The terminal device 100 may generate measurement information including measurement report information and / or CSI as feedback information. The measurement information may be measurement information on a cluster basis and / or measurement information on a light-emitting element basis. The terminal device 100 may also generate information indicating the combination of light-emitting elements 211 selected by the terminal device 100 as feedback information.

[0084] In step S104, the terminal device 100 transmits a feedback optical signal including the feedback information generated in step S103 to the base station device 200. The base station device 200 receives the feedback optical signal from the terminal device 100.

[0085] In step S105, the base station device 200 performs scheduling processing for the terminal device 100 based on the feedback information contained in the feedback optical signal received from the terminal device 100 in step S104. For example, in the scheduling processing, the base station device 200 determines a time slot to be allocated to the terminal device 100 and a combination of light-emitting elements 211 that constitute a cluster to be allocated to the terminal device 100 in that time slot. The base station device 200 may also determine a spreading code to be allocated to the terminal device 100 for data communication in the scheduling processing.

[0086] In step S106, the base station device 200 transmits a control optical signal including the scheduling information obtained by the scheduling process in step S105 to the terminal device 100. The scheduling information may include information indicating a time slot assigned to the terminal device 100. The scheduling information may include information indicating a spreading code assigned to the terminal device 100.

[0087] In step S107, the base station device 200 changes the cluster assigned to the terminal device 100 according to the combination of light-emitting elements 211 determined in step S105.

[0088] In step S108, the base station device 200 transmits the same optical signal (specifically, a data optical signal including data addressed to the terminal device 100) from each light-emitting element 211 in the cluster assigned to the terminal device 100 in the time slot assigned to the terminal device 100. The terminal device 100 receives and decodes the data optical signal from the base station device 200 based on the control optical signal received in step S106.

[0089] (7) Example of communication frame configuration Next, a configuration example of a communication frame used in the optical communication system 1 according to the embodiment will be described.

[0090] 13 is a diagram showing a first configuration example of a communication frame used in the optical communication system 1 according to the embodiment. An example in which one communication frame is composed of 10 time slots will be described below, but the number of time slots constituting one communication frame is not limited to 10. Each time slot is composed of a predetermined number of symbol intervals.

[0091] In the first configuration example shown in Fig. 13, a communication frame is composed of one synchronization slot (Sync.), one control slot (Ctrl.), four downlink slots (DL slots) #0 to #3, and four uplink slots (UL slots) #0 to #3. The downlink slots #0 to #3 constitute a downlink communication period. The uplink slots #0 to #3 constitute an uplink communication period.

[0092] The synchronization slot (Sync.) is a time slot in which the base station device 200 transmits a synchronization optical 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 using the synchronization optical signal. The control slot (Ctrl.) is a time slot in which the base station device 200 transmits a control optical signal.

[0093] In the first configuration example, a light-emitting element-specific reference signal (Ref.TxElement) and a data optical signal are arranged in each downlink slot (DL slot) in a time-division manner. In addition to or instead of the light-emitting element-specific reference signal, a cluster-specific reference signal may be arranged in each downlink slot (DL slot).

[0094] FIG. 14 is a diagram showing a second configuration example of a communication frame used in the optical communication system 1 according to the embodiment.

[0095] In the second configuration example shown in Fig. 14, the communication frame has a reference signal slot (Ref.) arranged before the downlink communication period. In the reference signal slot (Ref.), cluster-specific reference signals of each cluster are arranged in a time-division manner.

[0096] Here, we assume there are three clusters, and the reference signal slot (Ref.) contains three reference signals, Ref.#0 to #2, arranged in a time-division multiplexing manner. That is, the base station device 200 transmits the cluster-specific reference signal for each cluster in the reference signal slot (Ref.) in a time-division multiplexing manner. The terminal device 100 receives the cluster-specific reference signal for each cluster in the reference signal slot (Ref.) in a time-division multiplexing manner, enabling efficient measurement processing for each cluster-specific reference signal.

[0097] Figure 15 shows a third example of a communication frame configuration used in the optical communication system 1 according to this embodiment.

[0098] In the third configuration example shown in Figure 15, the communication frame has one time slot (Ctrl.+Ref.) shared by the control optical signal and the cluster-specific reference signal. The control optical signal and the cluster-specific reference signal for each cluster are time-division multiplexed within this time slot (Ctrl.+Ref.). The base station device 200 transmits the control optical signal and the cluster-specific reference signal for each cluster in time-division multiplexed within this time slot (Ctrl.+Ref.). The terminal device 100 can efficiently receive the control optical signal and the cluster-specific reference signal for each cluster in time-division multiplexed within this time slot (Ctrl.+Ref.).

[0099] Figure 16 shows a fourth example of a communication frame configuration used in the optical communication system 1 according to this embodiment.

[0100] 16, the communication frame has a reference signal slot (Ref.) arranged before the downlink communication period. In the reference signal slot (Ref.), light-emitting element-specific reference signals and cluster-specific reference signals of each cluster are arranged in a time-division manner.

[0101] Here, it is assumed that the number of clusters is three, and a light-emitting element-specific reference signal (Ref.TxElement) and three reference signals Ref.#0 to #2 are arranged in a time-division manner in the reference signal slot (Ref.). That is, the base station device 200 transmits the light-emitting element-specific reference signal and the cluster-specific reference signal of each cluster in a time-division manner in the reference signal slot (Ref.). The terminal device 100 can efficiently receive the light-emitting element-specific reference signal and the cluster-specific reference signal of each cluster in a time-division manner in the reference signal slot (Ref.).

[0102] FIG. 17 is a diagram showing a fifth configuration example of a communication frame used in the optical communication system 1 according to the embodiment.

[0103] In the fifth configuration example shown in Fig. 17, a communication frame has one time slot (Ctrl.+Ref.) shared by a control optical signal, a light-emitting element-specific reference signal, and a cluster-specific reference signal. In this time slot (Ctrl.+Ref.), the control optical signal (Ctrl.), a light-emitting element-specific reference signal (Ref.TxElement), and the cluster-specific reference signals of each cluster (Ref.#0 to #2) are allocated in a time-division manner. The base station device 200 transmits the control optical signal, the light-emitting element-specific reference signal, and the cluster-specific reference signal of each cluster in a time-division manner in this time slot (Ctrl.+Ref.). The terminal device 100 can efficiently receive the control optical signal, the light-emitting element-specific reference signal, and the cluster-specific reference signal of each cluster in a time-division manner in this time slot (Ctrl.+Ref.).

[0104] (8) Other embodiments In the above embodiment, an example has been described in which the base station device 200 configures each cluster with adjacent light-emitting elements 211. However, when, for example, downlink beamforming or space division multiple access (SDMA) using MIMO (Multiple Input Multiple Output) is applied, the base station device 200 may configure each cluster with light-emitting elements 211 that are not adjacent to each other.

[0105] In the above-described embodiment, combining transmission in downlink communication has been mainly described. Specifically, an example has been described in which a base station device 200 performs combining transmission to multiple terminal devices 100 from each cluster. However, the operation in the above-described embodiment may also be performed in uplink communication. The terminal device 100 may perform combining transmission to multiple base station devices 200 from each cluster. FIG. 18 is a diagram for explaining operation according to another embodiment. As shown in FIG. 18, the terminal device 100 simultaneously performs visible light communication with two base station devices 200a and 200b. For example, when performing handover of the terminal device 100 between the base station device 200a and the base station device 200b, the terminal device 100 simultaneously performs visible light communication with the two base station devices 200a and 200b.

[0106] Under these assumptions, the terminal device 100 (control unit 130) divides the plurality of light-emitting elements 111 into a plurality of clusters such that each cluster is composed of one or more light-emitting elements 111. The terminal device 100 (control unit 130) transmits the same optical signal from the light-emitting elements 111 in each cluster in each time interval while changing the combination of light-emitting elements 111 that make up each cluster in a time-division manner. Each time interval in which the terminal device 100 performs combined transmission is a time interval included in the uplink communication period. The terminal device 100 (control unit 130) assigns each cluster to the base station device 200. For example, the terminal device 100 (control unit 130) assigns the first cluster to the base station device 200a and the second cluster to the base station device 200b.

[0107] 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.

[0108] 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 a spherical shape (or in a mirror ball shape from another perspective) 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 a light emitting and receiving area, and a pair of a light emitting element and a light receiving element may be arranged on each face. Alternatively, the terminal device 100 and / or the base station device 200 may be configured in a 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 a light emitting and receiving area, and a pair of a light emitting element and a light receiving element may be arranged on each side.

[0109] 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).

[0110] The phrases "based on" and "depending on / in response to" used in this disclosure do not mean "based solely on" or "depending solely on" unless otherwise specified. The phrase "based on" means both "based solely on" and "at least partially on." Similarly, the phrase "depending on" means both "at least partially on" and "at least partially on." The terms "include," "comprise," and their variations do not mean that only the listed items are included, but that they may include only the listed items or may include additional items in addition to the listed items. Furthermore, the term "or" used in this disclosure is not intended to mean exclusive OR. In this disclosure, where articles are added by translation, such as a, an, and the in English, these articles are intended to include multiple items unless it is clearly indicated in the context that this is not the case.

[0111] 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.

[0112] This application claims priority from Japanese Patent Application No. 2022-086951 (filed May 27, 2022), the entire contents of which are incorporated herein by reference.

[0113] (9) Supplementary Notes Additional notes will be given regarding the features of the above-described embodiment.

[0114] (Appendix 1) A plurality of light-emitting elements; a control unit that divides the plurality of light-emitting elements into a plurality of clusters such that each cluster is composed of one or more light-emitting elements; The control unit changing the combination of light-emitting elements constituting each cluster in a time-division manner; controlling the plurality of light-emitting elements so that the light-emitting elements in each cluster transmit the same optical signal within each time interval; Optical communication device.

[0115] (Appendix 2) the optical communication device is a base station device, each of the time intervals is a time interval included in a downlink communication period; The control unit assigns each of the clusters to one or more terminal devices. The optical communication device described in Appendix 1.

[0116] (Appendix 3) a light receiving element for receiving a feedback optical signal from a terminal device; The control unit determines a combination of light-emitting elements constituting a cluster to be assigned to the terminal device based on the feedback optical signal. Optical communication device as described in Appendix 2.

[0117] (Note 4) The feedback optical signal includes information indicating a combination of light-emitting elements selected by the terminal device. Optical communication device as described in Appendix 3.

[0118] (Note 5) The control unit multiplexes a plurality of terminal devices to which the same cluster is assigned within one time period by code division multiple access. 5. An optical communication device according to any one of claims 2 to 4.

[0119] (Note 6) The control unit controls the plurality of light-emitting elements so that the light-emitting elements in each cluster transmit a cluster-specific reference signal. 6. An optical communication device according to any one of claims 2 to 5.

[0120] (Note 7) a light receiving element for receiving a feedback optical signal from a terminal device; The feedback optical signal includes cluster-level measurement information obtained by the terminal device performing measurement processing on the cluster-specific reference signal. 7. The optical communication device of claim 6.

[0121] (Appendix 8) The control unit controls the plurality of light-emitting elements to transmit the cluster-specific reference signals of each cluster in a time-division manner within a single time interval not included in the downlink communication period. 8. The optical communication device according to claim 6 or 7.

[0122] (Note 9) The control unit controls the plurality of light-emitting elements so that each light-emitting element within each cluster transmits a light-emitting element-specific reference signal. An optical communication device as described in any of Appendix 2 to 8.

[0123] (Note 10) a light receiving element for receiving a feedback optical signal from a terminal device; The feedback optical signal includes measurement information for each light-emitting element obtained by the terminal device performing measurement processing on the light-emitting element's inherent reference signal. The control unit derives cluster-level measurement information from the measurement information of the light-emitting element unit. 10. The optical communication device of claim 9.

[0124] (Note 11) The control unit controls the plurality of light-emitting elements to transmit the cluster-specific reference signal and the light-emitting element-specific reference signal in a time-division manner within a single time interval not included in the downlink communication period. An optical communication device as described in any of Appendix 2 to 10.

[0125] (Note 12) The plurality of light-emitting elements are arranged such that the angle between the optical axis of one light-emitting element and the optical axis of the other light-emitting element increases as the distance between them increases. An optical communication device as described in any of the appendices 1 to 11.

[0126] (Note 13) When one cluster is configured with two or more light-emitting elements, the control unit configures the one cluster with light-emitting elements adjacent to each other. Optical communication device as described in Appendix 12.

[0127] (Note 14) An optical communication method used in an optical communication device having a plurality of light-emitting elements, dividing the plurality of light emitting elements into a plurality of clusters, each cluster consisting of one or more light emitting elements; changing the combination of light-emitting elements constituting each cluster in a time-division manner; and controlling the plurality of light-emitting elements so that the light-emitting elements in each cluster transmit the same optical signal within each time interval. Optical communication method.

[0128] (Appendix 15) An optical communication device having a plurality of light-emitting elements, dividing the plurality of light emitting elements into a plurality of clusters, each cluster consisting of one or more light emitting elements; a step of changing a combination of light-emitting elements constituting each cluster in a time-division manner; controlling the plurality of light-emitting elements so that the light-emitting elements in each cluster transmit the same optical signal within each time interval; Optical communication program. [Explanation of symbols]

[0129] 1: Optical communication system 100: Terminal device 110: Light-emitting part 111: Light-emitting element 112: Transmitter 120: Light receiving part 121: Photodetector 122: Receiver 130: Control unit 131: Processor 132: Memory 150: Light receiving and emitting unit 151: Light receiving and emitting area 160: Main body 200:Base station equipment 210: Light-emitting part 211: Light-emitting element 212: Transmitter 220: Light receiving section 221: Photodetector 222: Receiver 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 251: Light receiving and emitting area 260: Main body

Claims

1. A plurality of light-emitting elements; a control unit that divides the plurality of light-emitting elements into a plurality of clusters such that each cluster is composed of one or more light-emitting elements; The control unit changing the combination of light-emitting elements constituting each cluster in a time-division manner; controlling the plurality of light-emitting elements so that the light-emitting elements in each cluster transmit the same optical signal within each time interval; An optical communication device, the optical communication device is a base station device, each of the time intervals is a time interval included in a downlink communication period; The control unit assigns each of the clusters to one or more terminal devices. Optical communication equipment.

2. a light receiving element for receiving a feedback optical signal from a terminal device; The control unit determines a combination of light-emitting elements constituting a cluster to be assigned to the terminal device based on the feedback optical signal.

2. The optical communication device according to claim 1.

3. The feedback optical signal includes information indicating a combination of light-emitting elements selected by the terminal device.

3. The optical communication device according to claim 2.

4. The control unit multiplexes a plurality of terminal devices to which the same cluster is assigned within one time period by code division multiplexing.

2. The optical communication device according to claim 1.

5. The control unit controls the plurality of light-emitting elements so that the light-emitting elements in each cluster transmit a cluster-specific reference signal.

2. The optical communication device according to claim 1.

6. a light receiving element for receiving a feedback optical signal from a terminal device; The feedback optical signal includes measurement information in units of clusters obtained by the terminal device performing measurement processing on the cluster-specific reference signal.

6. The optical communication device according to claim 5.

7. The control unit controls the plurality of light-emitting elements to transmit cluster-specific reference signals of the clusters in a time division manner within one time period that is not included in the downlink communication period.

6. The optical communication device according to claim 5.

8. The control unit controls the plurality of light-emitting elements so that each light-emitting element in each cluster transmits a light-emitting element-specific reference signal.

2. The optical communication device according to claim 1.

9. a light receiving element for receiving a feedback optical signal from a terminal device; the feedback optical signal includes measurement information for each light-emitting element obtained by the terminal device performing a measurement process on the light-emitting element-specific reference signal, The control unit derives cluster-based measurement information from the light-emitting element-based measurement information.

9. The optical communication device according to claim 8.

10. The control unit controls the plurality of light emitting elements to transmit a cluster-specific reference signal and a light emitting element-specific reference signal in a time division manner within one time period that is not included in the downlink communication period.

2. The optical communication device according to claim 1.

11. A plurality of light-emitting elements; a control unit that divides the plurality of light-emitting elements into a plurality of clusters such that each cluster is composed of one or more light-emitting elements; The control unit changing the combination of light-emitting elements constituting each cluster in a time-division manner; controlling the plurality of light-emitting elements so that the light-emitting elements in each cluster transmit the same optical signal within each time interval; The plurality of light emitting elements are arranged such that as the distance between one light emitting element and another light emitting element increases, the angle formed between the optical axis of the one light emitting element and the optical axis of the other light emitting element increases. Optical communication equipment.

12. When one cluster is configured with two or more light-emitting elements, the control unit configures the one cluster with light-emitting elements adjacent to each other. The optical communication device according to claim 11.

13. An optical communication method used in an optical communication device having a plurality of light-emitting elements, dividing the plurality of light emitting elements into a plurality of clusters, each cluster consisting of one or more light emitting elements; changing the combination of light-emitting elements constituting each cluster in a time-division manner; and controlling the plurality of light-emitting elements so that the light-emitting elements in each cluster transmit the same optical signal within each time interval.

1. An optical communication method, comprising: the optical communication device is a base station device, each of the time intervals is a time interval included in a downlink communication period; In the step of controlling, each of the clusters is assigned to one or more terminal devices. Optical communication method.

14. An optical communication device having a plurality of light-emitting elements, dividing the plurality of light emitting elements into a plurality of clusters, each cluster consisting of one or more light emitting elements; a step of changing a combination of light-emitting elements constituting each cluster in a time-division manner; controlling the plurality of light-emitting elements so that the light-emitting elements in each cluster transmit the same optical signal within each time interval; An optical communication program, the optical communication device is a base station device, each of the time intervals is a time interval included in a downlink communication period; The controlling step includes a step of assigning each of the clusters to one or more terminal devices. Optical communications program.

15. A plurality of light-emitting elements; a control unit that divides the plurality of light-emitting elements into a plurality of clusters such that each cluster is composed of one or more light-emitting elements; The control unit changing the combination of light-emitting elements constituting each cluster in a time-division manner; controlling the plurality of light-emitting elements so that the light-emitting elements in each cluster transmit the same optical signal within each time interval; An optical communication device, the optical communication device is a terminal device, each of the time intervals is a time interval included in an uplink communication period, The control unit assigns each of the clusters to one or more base station devices. Optical communication equipment.

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