Traffic communication system, traffic communication method, and wireless roadside device

Abstract

To provide a traffic communication system, a traffic communication method, and a wireless roadside apparatus that can properly perform both road-to-vehicle communication and road-to-road communication.SOLUTION: A traffic communication system according to an aspect is a traffic communication system having a first wireless roadside apparatus, an in-vehicle communication apparatus mounted in a vehicle, and a second wireless roadside apparatus capable of wireless communication with the first wireless roadside apparatus as well as wireless communication with the in-vehicle communication apparatus. In the traffic communication system, the second wireless roadside apparatus has a plurality of antennas and a control unit that selects an antenna to be used as a transmission antenna among the plurality of antennas according to a communication partner.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a traffic communication system, a traffic communication method, and a wireless roadside unit. [Background technology]

[0002] In recent years, Intelligent Transport Systems (ITS) have been attracting attention as a technology that can prevent the risk of traffic accidents. Non-Patent Document 1 defines the standard specifications for a transport communication system that has wireless roadside units, which are base stations installed on the roadside, and in-vehicle communication units, which are mobile stations installed in vehicles.

[0003] In the field of traffic communication systems, for example, the following technology exists: That is, among wireless roadside devices that perform road-to-vehicle communication with in-vehicle communication devices, there is a wireless roadside device that performs road-to-road communication, which is wireless communication with other wireless roadside devices (for example, Patent Document 1 below). [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] ARIB STD-T109 Version 1.3 "700MHz Band Intelligent Transport Systems" [Patent documents]

[0005] [Patent Document 1] Patent No. 5071123 Summary of the Invention [Problem to be solved by the invention]

[0006] There is room for improvement in the wireless quality of the wireless roadside device described in Patent Document 1.

[0007] The present disclosure provides a traffic communication system, a traffic communication method, and a wireless roadside unit that can improve wireless quality. [Means for solving the problem]

[0008] A traffic communication system according to a first aspect includes a first wireless roadside device, an on-board communication device mounted on a vehicle, and a second wireless roadside device capable of wireless communication with the first wireless roadside device and also capable of wireless communication with the on-board communication device. In the traffic communication system, the second wireless roadside device includes a plurality of antennas and a control unit that selects an antenna to be used as a transmitting antenna from the plurality of antennas depending on a communication partner.

[0009] A traffic communication method according to a second aspect is a traffic communication method in a traffic communication system having a first wireless roadside device, an on-board communication device mounted on a vehicle, and a second wireless roadside device capable of wireless communication with the first wireless roadside device and also capable of wireless communication with the on-board communication device. The traffic communication method includes a step in which the second wireless roadside device, which has multiple antennas, selects an antenna to be used as a transmitting antenna from the multiple antennas in accordance with a communication partner.

[0010] A wireless roadside device according to a third aspect is a wireless roadside device capable of wireless communication with other wireless roadside devices and with an in-vehicle communication device installed in a vehicle. The wireless roadside device has a plurality of antennas and a control unit that selects an antenna to be used as a transmitting antenna from the plurality of antennas depending on the communication partner. [Effects of the Invention]

[0011] According to the present disclosure, it is possible to provide a traffic communication system, a traffic communication method, and a wireless roadside unit that can improve wireless quality. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a diagram illustrating an example of the configuration of a transportation communication system according to the first embodiment. [Figure 2] FIG. 2 is a diagram illustrating an example of time slot allocation according to the first embodiment. [Figure 3]FIG. 3 is a diagram illustrating an example of the configuration of a wireless roadside device according to the first embodiment. [Figure 4] FIG. 4 is a diagram illustrating an example of operation according to the first embodiment. [Figure 5] FIG. 5 is a diagram illustrating an example of operation according to the first embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] [First embodiment] In ITS, wireless roadside devices may communicate between vehicle-mounted communication devices and roadside vehicles, and may also communicate between other wireless roadside devices and roadside devices.

[0014] The vehicle-mounted communication device is mounted on a vehicle. Therefore, for road-to-vehicle communication, it is preferable that the antenna of the wireless roadside device is installed facing the direction of the road on which the vehicle is traveling.

[0015] On the other hand, wireless roadside devices may be installed in fixed locations, such as traffic lights. Therefore, for road-to-road communication, it is preferable that the antenna of a wireless roadside device be installed facing the direction of other wireless roadside devices.

[0016] However, in some cases, a wireless roadside device uses a single antenna for both road-to-vehicle communication and road-to-road communication. In such cases, if one antenna is pointed toward the road in consideration of road-to-vehicle communication, the wireless quality for other roadside devices may fall below a certain level, and wireless transmission to other roadside devices may not be performed properly. On the other hand, if a wireless roadside device points one antenna toward other wireless roadside devices in consideration of road-to-road communication, the wireless quality for in-vehicle communication devices may fall below a certain level, and wireless transmission to the in-vehicle communication devices may not be performed properly.

[0017] Therefore, the first embodiment aims to appropriately perform both road-to-vehicle communication and road-to-road communication.

[0018] A transportation communication system according to an embodiment will be described below with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals.

[0019] (Example of a traffic communication system configuration) First, a configuration example of a transportation communication system according to the first embodiment will be described. The following mainly describes a transportation communication system that performs wireless communication based on the standard of Non-Patent Document 1. However, the transportation communication system according to the first embodiment is not limited to this standard, and may perform wireless communication based on, for example, the V2X (Vehicle-to-Everything) standard of 3GPP (Third Generation Partnership Project) (registered trademark; the same applies hereinafter) or the IAB (Integrated Access Backhaul) standard of 3GPP.

[0020] Fig. 1 is a diagram showing an example of the configuration of a transportation communication system 10 according to the first embodiment. As shown in Fig. 1, the transportation communication system 10 includes wireless roadside units 100-1 to 100-3 and in-vehicle communication units 250-1 to 250-3 mounted on vehicles 200-1 to 200-3, respectively.

[0021] The wireless roadside devices 100-1 to 100-3 are installed near roads. The wireless roadside devices 100-1 to 100-3 may be installed on poles (or utility poles) near roads, or on traffic signal lights (e.g., traffic lights). The wireless roadside devices 100-1 to 100-3 may be connected to a server device via a communication line. The server device may be called a central device, and may collect various types of traffic information based on information received by the wireless roadside devices 100-1 to 100-3, and manage road traffic. The wireless roadside devices 100-1 to 100-3 may also be called base stations. In the following description, when the wireless roadside devices 100-1 to 100-3 are not particularly distinguished from one another, they may also be called wireless roadside devices 100.

[0022] Vehicles 200-1 to 200-3 may be any vehicle that travels on a road. Vehicles 200-1 to 200-3 may be, for example, automobiles such as standard cars or light cars, or motorcycles. Vehicles 200-1 to 200-3 may also be autonomous vehicles. Vehicles 200-1 to 200-3 are each provided with an on-board communication device 250-1 to 250-3. On-board communication devices 250-1 to 250-3 may be stationary communication devices that are fixedly installed in vehicles 200-1 to 200-3, respectively, or may be portable communication devices that are temporarily connected to vehicles 200-1 to 200-3 via cables, respectively. On-board communication devices 250-1 to 250-3 may also be referred to as mobile stations. In the following description, when vehicles 200-1 to 200-3 are not particularly distinguished from one another, they may also be referred to as vehicle 200. In the following description, the in-vehicle communication devices 250-1 to 250-3 may be referred to as the in-vehicle communication device 250 when no particular distinction is made.

[0023] 1 illustrates three wireless roadside devices 100-1 to 100-3, but the number of wireless roadside devices 100 may be one, two, four or more. Also, in the traffic communication system 10 illustrated in FIG. 1, three in-vehicle communication devices 250-1 to 250-3 are illustrated, but the number of in-vehicle communication devices 250 may be one, two, four or more.

[0024] 1, the wireless roadside device 100-1 (e.g., a second wireless roadside device) is capable of wireless communication with the wireless roadside devices 100-2 and 100-3 (e.g., a first wireless roadside device), and is also capable of wireless communication with the in-vehicle communication device 250. That is, the wireless roadside device 100-1 is capable of road-to-road communication with the wireless roadside devices 100-2 and 100-3, and is also capable of road-to-vehicle communication with the in-vehicle communication device 250. The other wireless roadside devices 100-2 and 100-3 may also be capable of both road-to-road communication and road-to-vehicle communication, similar to the wireless roadside device 100-1.

[0025] (Road-to-road communication and road-to-vehicle communication) Here, road-to-road communication and road-to-vehicle communication will be described.

[0026] In the traffic communication system 10, road-to-vehicle communication, road-to-roadside communication, and vehicle-to-vehicle communication are each performed in a time-division manner, taking interference into consideration. Here, road-to-vehicle communication refers to communication between the wireless roadside device 100 and the in-vehicle communication device 250. Furthermore, road-to-roadside communication refers to communication between the wireless roadside devices 100. Furthermore, vehicle-to-vehicle communication refers to communication between the in-vehicle communication devices 250.

[0027] FIG. 2 is a diagram showing an example of time slot allocation used in the transportation communication system 10. As shown in FIG.

[0028] 2, in road-to-vehicle communication, a road-to-vehicle communication period is allocated to the wireless roadside device 100. With 16 μs as one control unit (called a "unit"), up to 16 road-to-vehicle communication periods can be set within a 100 ms cycle (called a "control cycle") at intervals of 390 units (6240 μs) from the beginning of the control cycle.

[0029] On the other hand, in road-to-road communication, wireless communication is also carried out using a road-to-vehicle communication period (or time slot, hereinafter sometimes referred to as a "time slot"). However, when road-to-road communication is carried out, a different time slot is assigned to the road-to-vehicle communication. In the example of FIG. 2, slot number "1" and slot number "2" are assigned as time slots for road-to-vehicle communication, while slot number "15" and slot number "16" are assigned as time slots for road-to-road communication.

[0030] 2 is merely an example, and other slot numbers may be assigned as long as different time slots are used for road-to-vehicle communication and road-to-road communication. That is, different pre-assigned time slots are used for road-to-vehicle communication and road-to-road communication to perform wireless communication. Note that the assignment itself is performed in advance before each communication is performed.

[0031] On the other hand, vehicle-to-vehicle communication is performed in periods other than the road-to-vehicle communication period (or time slot). In the example shown in Figure 2, vehicle-to-vehicle communication is performed in periods other than the periods from slot number "1" to "16".

[0032] (Messages used in road-to-road communications and road-to-vehicle communications) In road-to-vehicle communication, for example, the wireless roadside device 100 broadcasts (announces) a road-to-vehicle message. The road-to-vehicle message includes information about the road-to-vehicle communication period. The road-to-vehicle message has a predetermined format that complies with, for example, the "ITS Wireless Roadside Device Communication Application Common Standard" issued by the Universal Traffic Management System (UTMS) Association. Specifically, the wireless roadside device 100 secures its own transmission time by transmitting (announces) a road-to-vehicle message that includes, as its own transmission information, a transmission time and road-to-vehicle communication period information (number of transfers and road-to-vehicle communication period length) to surrounding in-vehicle communication devices 250.

[0033] The in-vehicle communication device 250 that has received such a road-to-vehicle message synchronizes its time based on the transmission time included in the road-to-vehicle message, stops its own transmission based on road-to-vehicle communication period information included in the road-to-vehicle message, and performs transmission at a timing other than the transmission period of the wireless roadside device 100. Specifically, the in-vehicle communication device 250 broadcasts (announces) the vehicle information message by the CSMA / CA (Carrier Sense Multiple Access / Collision Avoidance) method during times other than the road-to-vehicle communication period allocated to the wireless roadside device 100 and during road-to-vehicle communication periods not allocated to the wireless roadside device 100. The wireless roadside device 100 receives the vehicle information message transmitted from the in-vehicle communication device 250 during the road-to-vehicle communication period that has not been used for transmitting its own road-to-vehicle message.

[0034] Regarding road-to-road communication, for example, the wireless roadside device 100 broadcasts (announces) road-to-road messages. The road-to-road messages also have a predetermined format that conforms to, for example, the "ITS Wireless Roadside Device Communication Application Common Standard" issued by the Universal Traffic Management System (UTMS) Association. The road-to-road messages may include sender information (or identification information) that identifies the wireless roadside device 100 that sent them. The road-to-road messages include information about the road-to-road communication period. The information about the road-to-road communication period is basically the same as the information about the road-to-vehicle communication period, but differs in that it targets road-to-road communication. Specifically, the wireless roadside device 100 secures its own transmission time by broadcasting (announces) to other wireless roadside devices an road-to-road message that includes, as its own transmission information, a transmission time and road-to-road communication period information (number of transfers and road-to-road communication period length). Similarly, the other wireless roadside devices secure their own transmission time by broadcasting road-to-road messages to the wireless roadside device 100. In this case, the wireless roadside device 100 and the other wireless roadside devices will share the time slot for road-to-road communication, but interference can be prevented by transmitting using different time slots (or different frames contained within the time slot).

[0035] In the inter-vehicle communication, the vehicle information message described above is used. The in-vehicle communication device 250 broadcasts the vehicle information message using the CSMA / CA (Carrier Sense Multiple Access / Collision Avoidance) method, similar to the transmission to the wireless roadside device 100.

[0036] In this way, road-to-vehicle communication and vehicle-to-vehicle communication can recognize the status of surrounding vehicles, traffic information, the presence or absence of pedestrians, etc., and provide support to avoid the risk of traffic accidents. Furthermore, road-to-road communication can also improve signal control by transmitting and receiving information about signal control between traffic lights at adjacent intersections, enabling environmentally friendly driving support. Furthermore, combining these types of communication can smooth traffic flow and provide support for safer traffic.

[0037] (Example of wireless roadside unit configuration) Next, a configuration example of the wireless roadside device 100 will be described.

[0038] FIG. 3 is a diagram illustrating an example of the configuration of the wireless roadside device 100. As shown in FIG.

[0039] As shown in FIG. 3, the wireless roadside device 100 includes two antennas 110-1 and 110-2, two radio circuits 120-1 and 120-2, and a control unit .

[0040] Both the antennas 110-1 and 110-2 are capable of transmitting and receiving. However, either of the antennas 110-1 and 110-2 is used as the transmitting antenna depending on the communication partner. When the communication partner is the in-vehicle communication device 250, one of the antennas 110-1 and 110-2, which is determined by the operator (for example, the first antenna), is used as the transmitting antenna. On the other hand, when the communication partner is another wireless roadside device, either of the antennas 110-1 and 110-2 is used as the transmitting antenna depending on the wireless quality when the wireless roadside device 100 performs wireless communication with the other wireless roadside device. The transmitting antenna for road-to-vehicle communication and the transmitting antenna for road-to-road communication may be the same antenna or different antennas.

[0041] The radio circuits 120-1 and 120-2 convert (down-convert) radio signals received by the antennas 110-1 and 110-2, respectively, into received signals in the baseband, and output the converted received signals to the control unit 130. The radio circuits 120-1 and 120-2 also convert (up-convert) transmission signals output from the control unit 130 into radio signals in the radio band, and output the converted radio signals to the antennas 110-1 and 110-2, respectively.

[0042] The radio circuit 120-1 may measure the radio quality of a radio signal transmitted from another radio roadside device and received by the antenna 110-1. The radio circuit 120-1 outputs the measured radio quality to the control unit 130. The radio circuit 120-2 may also measure the radio quality of a radio signal transmitted from another radio roadside device and received by the antenna 110-2. The radio circuit 120-2 also outputs the measured radio quality to the control unit 130. The radio quality may be at least any of a received signal strength indicator (RSSI), a signal-to-interference ratio (SIR), a signal-to-interference-plus-noise ratio (SINR), a reference signal received power (RSRP), and a reference signal received quality (RSRQ).

[0043] The control unit 130 performs various controls in the wireless roadside device 100. The control unit 130 includes at least one memory (or storage unit) and at least one processor electrically connected to the memory. The memory stores programs executed by the processor and information used in processing by the processor. The memory may also store communication history information related to wireless quality. The processor executes the programs stored in the memory to perform various functions and processes. For example, by the processor executing the programs, the control unit 130 can execute a wireless control function unit 131, a slot determination function unit 132, a reception quality determination function unit 133, and a transmitting antenna determination function unit 134. The wireless control function unit 131, the slot determination function unit 132, the reception quality determination function unit 133, and the transmitting antenna determination function unit 134 may represent functions executed by the control unit 130.

[0044] The wireless control function unit 131 controls wireless communication in the wireless roadside device 100. The wireless control function unit 131 may perform control so that wireless communication is performed in accordance with ARIB STD-T109 (Non-Patent Document 1). The wireless control function unit 131 may perform control so that wireless communication is performed according to the V2X standard for road-to-vehicle communication, and may perform control so that wireless communication is performed according to the IAB standard for road-to-road communication.

[0045] The slot determination function unit 132 determines for each time slot whether it is a time slot for road-to-vehicle communication or a time slot for road-to-road communication. For example, the slot determination function unit 132 determines, based on the time slot number representing each time slot, whether it is a time slot for road-to-vehicle communication (i.e., the communication partner is the in-vehicle communication device 250) or a time slot for road-to-road communication (i.e., the communication partner is another wireless roadside device). The wireless control function unit 131 can perform road-to-vehicle communication or road-to-road communication in each time slot determined by the slot determination function unit 132.

[0046] The reception quality judgment function unit 133 stores the wireless quality in road-to-road communication in a memory (or storage unit). Specifically, the reception quality judgment function unit 133 associates the wireless quality of each of the antennas 110-1 and 110-2 for a wireless signal received from another wireless roadside device with transmission source information (or identification information) of the other wireless roadside device, and stores the associated information in the memory (or storage unit) as communication history information. For example, in the example of FIG. 1, the following applies: That is, the reception quality judgment function unit 133 of the wireless roadside device 100-1 stores the wireless quality of each of the antennas 110-1 and 110-2 for a wireless signal received from the wireless roadside device 100-2, and associates the associated information with transmission source information (or identification information) of the wireless roadside device 100-2. Furthermore, the reception quality determination function unit 133 of the wireless roadside device 100-1 stores the wireless quality of each of the antennas 110-1 and 110-2 for the wireless signal received from the wireless roadside device 100-3 in association with the transmission source information (or identification information) of the wireless roadside device 100-3.

[0047] The transmitting antenna determination function unit 134 selects the antenna 110-1 or 110-2 to be used as the transmitting antenna from the antennas 110-1 and 110-2 depending on the communication partner. Specifically, the process is as follows.

[0048] First, when the communication partner is an in-vehicle communication device, the transmitting antenna determination function unit 134 selects an antenna (for example, the first antenna) determined by the operator from among the multiple antennas 110-1 and 110-2 as the transmitting antenna.

[0049] Second, when the communication partner is another wireless roadside device (e.g., a first wireless roadside device), the transmitting antenna determination function unit 134 selects one of the multiple antennas 110-1 and 110-2 as a transmitting antenna depending on the wireless quality when the wireless roadside device 100 (e.g., a second wireless roadside device) performed wireless communication with the other wireless roadside device. In this case, the transmitting antenna determination function unit 134 selects the transmitting antenna based on communication history information stored in memory. In other words, when the communication partner is another wireless roadside device, the transmitting antenna determination function unit 134 selects the antenna 110-1 or 110-2 with the best wireless quality among the wireless qualities for the other wireless roadside device as a transmitting antenna for the other wireless roadside device.

[0050] The transmitting antenna determination function unit 134 may determine whether the communication partner is the in-vehicle communication device 250 (i.e., road-to-vehicle communication) or another roadside device (i.e., road-to-road communication) by using the time slot determined by the slot determination function unit 132. Then, the radio control function unit 131 may perform road-to-vehicle communication or road-to-road communication by using the transmitting antenna selected in the transmitting antenna determination function unit 134 according to the communication partner.

[0051] (Operation example according to the first embodiment) Next, an example of operation according to the first embodiment will be described.

[0052] The operation example according to the first embodiment is an operation example (first operation example) during wireless reception in which the wireless roadside device 100-1 receives a wireless signal transmitted from another wireless roadside device 100-2 or 100-3. The operation example according to the first embodiment also includes an operation example (second operation example) during wireless transmission in which the wireless roadside device 100-1 selects either the antenna 110-1 or 110-2 as a transmitting antenna and performs wireless transmission. First, the first operation example will be described, and then the second operation example will be described.

[0053] (1. First operation example) Fig. 4 is a flowchart showing a first operation example. In the first operation example, an example will be described in which the wireless roadside device 100-1 shown in Fig. 1 receives a wireless signal from the wireless roadside device 100-2 or 100-3 through road-to-road communication.

[0054] As shown in FIG. 4, in step S10, the wireless roadside device 100-1 starts the process of the first operation example.

[0055] In step S11, the control unit 130 of the wireless roadside device 100-1 determines whether the received signal is a signal received via road-to-road communication. The control unit 130 (slot determination function unit 132) makes this determination based on the slot number of the time slot of the received signal. Specifically, the control unit 130 determines that the received signal is received via road-to-road communication if the slot number is a time slot for road-to-road communication. On the other hand, if the slot number is not a time slot for road-to-road communication, the control unit 130 determines that the received signal is not received via road-to-road communication. The control unit 130 may determine the slot number by counting the slot number for each time slot period from the start of the control cycle. In step S11, if the received signal is a signal received via road-to-road communication (Yes in step S11), the process proceeds to step S12. On the other hand, if the received signal is not a signal received via road-to-road communication (No in step S11), the process proceeds to step S13.

[0056] In step S12, the control unit 130 (reception quality determination function unit 133) acquires the wireless quality of the received signal, associates the transmission source information with the wireless quality, and stores them in the memory. For example, when the control unit 130 receives a wireless signal from the wireless roadside device 100-2, the control unit 130 associates the transmission source information (or identification information) of the wireless roadside device 100-2 with the wireless quality of the wireless signal for each of the antennas 110-1 and 110-2 and stores them in the memory. Also, for example, when the control unit 130 receives a wireless signal from the wireless roadside device 100-3, the control unit 130 associates the transmission source information (or identification information) of the wireless roadside device 100-3 with the wireless quality of the wireless signal for each of the antennas 110-1 and 110-2 and stores them in the memory. The transmission source information and the wireless quality are stored in the memory in association with each other as communication history information. The control unit 130 may acquire the transmission source information (or identification information) of each of the wireless roadside devices 100-2 and 100-3 from the received signal.

[0057] In step S13, the wireless roadside device 100 ends the first operation example.

[0058] According to the first operation example, the memory of the wireless roadside device 100-1 stores the wireless quality of each of the antennas 110-1 and 110-2 for the wireless roadside device 100-2 and the wireless quality of each of the antennas 110-1 and 110-2 for the wireless roadside device 100-3. The wireless qualities stored in the memory may be updated (or overwritten) every time the wireless roadside device 100-1 receives wireless signals from the other wireless roadside devices 100-2 and 100-3 and the wireless qualities are measured. At least the latest wireless qualities are stored in the memory.

[0059] (2. Second operation example) Next, a second operation example will be described.

[0060] 5 is a flowchart illustrating a second operation example. The second operation example will be described using an example in which the wireless roadside device 100-1 selects either the antenna 110-1 or 110-2 as a transmitting antenna for road-to-vehicle communication, and the wireless roadside device 100-1 selects either the antenna 110-1 or 110-2 as a transmitting antenna for road-to-vehicle communication.

[0061] As shown in FIG. 5, in step S20, the wireless roadside device 100-1 starts the processing of the second operation example.

[0062] In step S21, the control unit 130 of the wireless roadside device 100-1 determines whether the transmission slot used for wireless transmission is a transmission slot for road-to-road communication. That is, the control unit 130 checks the slot number of the transmission slot to determine whether it is road-to-road communication (or whether the communication partner is the wireless roadside device 100-2 or 100-3) or road-to-vehicle communication (or whether the communication partner is the in-vehicle communication device 250). When the slot number of the transmission slot is a slot number for road-to-road communication, the control unit 130 (slot determination function unit 132) determines that it is a slot number for road-to-road communication (Yes in step S21). In this case, the process proceeds to step S22. On the other hand, when the slot number of the transmission slot is a number other than a slot number for road-to-road communication, the control unit 130 determines that it is not a slot number for road-to-road communication (No in step S21). In this case, the process proceeds to step S26.

[0063] In step S22, the control unit 130 determines whether or not there is communication history information with the destination wireless roadside device 100 (wireless roadside device 100-2 or wireless roadside device 100-3). For example, when the destination is the wireless roadside device 100-2, the control unit 130 (reception quality determination function unit 133) determines whether or not communication history information having the wireless roadside device 100-2 in the source information is stored in memory. If communication history information having the source information is stored in memory, the control unit 130 (reception quality determination function unit 133) determines that there is communication history information with the destination wireless roadside device 100 (Yes in step S22). In this case, the process proceeds to step S23. On the other hand, if communication history information having the source information is not stored in memory, the control unit 130 (reception quality determination function unit 133) determines that there is no communication history information with the destination wireless roadside device 100 (No in step S22). In this case, the process proceeds to step S26.

[0064] In step S23, the control unit 130 selects the antenna 110-1 or 110-2 with the best wireless quality for wireless communication with the wireless roadside unit 100, based on the communication history information with the destination wireless roadside unit 100. That is, if the communication partner is another wireless roadside unit 100-2 or 100-3 (Yes in step S21) and there is communication history information with the destination wireless roadside unit 100-2 or 100-3 (Yes in step S22), the control unit 130 selects the antenna 110-1 or 110-2 with the best wireless quality for wireless communication with the destination wireless roadside unit 100-2 or 100-3, based on the communication history information. For example, when the destination is the wireless roadside device 100-2, the control unit 130 (transmitting antenna determination function unit 134) selects the antenna (e.g., antenna 110-1) with the best wireless quality for wireless communication with the wireless roadside device 100-2 based on communication history information that includes the wireless roadside device 100-2 in the source information. It is preferable that the control unit 130 makes the selection using the most recent communication history information when this process is performed.

[0065] In step S24, the control unit 130 (radio control function unit 131) uses the selected antenna 110-1 or 110-2 to perform radio transmission to the other wireless roadside device 100-2 or 100-3, which is the transmission destination.

[0066] Then, in step S25, the wireless roadside device 100-1 ends the second operation example.

[0067] On the other hand, in step S26, the control unit 130 performs wireless transmission to the destination using the antenna 110-1 or 110-2 determined by the operator. That is, if the transmission slot is a time slot for road-to-vehicle communication (No in step S21), in other words, if the communication partner is the in-vehicle communication device 250, the control unit 130 (transmitting antenna determination function unit 134) selects the antenna determined by the operator (e.g., antenna 110-1) as the transmitting antenna. Also, if the communication partner is another wireless roadside device 100 and there is no communication history information with that other wireless roadside device 100 (No in step S22), in other words, if wireless transmission is to be performed to a wireless roadside device from which the wireless roadside device 100-1 has not received a wireless signal in the past (e.g., a third wireless roadside device), the control unit 130 (transmitting antenna determination function unit 134) selects the antenna determined by the operator (e.g., antenna 110-2) as the transmitting antenna. Then, the control unit 130 (radio control function unit 131) will use the selected antenna to perform radio transmission to the destination.

[0068] Then, in step S25, the wireless roadside device 100-1 ends the second operation example.

[0069] (Effects of the first embodiment) 1, it is assumed that the antenna 110-2 of the wireless roadside device 100-1 is installed facing the road direction, and that the antenna 110-1 is closer to the wireless roadside device 100-2 than the antenna 110-2. It is also assumed that the antenna 110-2 is used as a transmitting antenna for road-to-vehicle communication, and the antenna 110-1 is used as a transmitting antenna for road-to-road communication, and that they are both fixed and operated.

[0070] In such a case, the antenna 110-2 is set facing the road direction, and therefore can appropriately perform wireless transmission to the in-vehicle communication device 250. Furthermore, the antenna 110-1 is also closer to the wireless roadside device 100-2 than the antenna 110-2, and therefore can appropriately perform wireless transmission to the wireless roadside device 100-2.

[0071] However, for road-to-road communication with the wireless roadside device 100-3, although the antenna 110-2 is installed facing the road direction, the antenna 110-2 is closer to the wireless roadside device 100-3 than the antenna 110-1. Therefore, there are cases where the antenna 110-2 has better wireless quality with respect to the wireless roadside device 100-3 than the antenna 110-1. In such a case, it is not necessarily appropriate to use the antenna 110-1 as a transmitting antenna for road-to-road communication.

[0072] In the first embodiment, the wireless roadside device 100 is configured to be able to select the antenna 110-1 or 110-2 to be used as a transmitting antenna depending on the communication partner. Therefore, the wireless roadside device 100-1 can select the antenna 110-2 as a transmitting antenna for the wireless roadside device 100-3. Furthermore, the wireless roadside device 100-1 can select the antenna 110-2 as a transmitting antenna for the in-vehicle communication device 250 (i.e., road-to-vehicle communication). Furthermore, the wireless roadside device 100-1 can select the antenna 110-1 as a transmitting antenna for the wireless roadside device 100-2. This allows the wireless roadside device 100-1 to appropriately perform both road-to-vehicle communication and road-to-road communication.

[0073] (Another example of the first embodiment) In the first embodiment, an example in which the wireless roadside device 100 has two antennas 110-1 and 110-2 has been described, but implementation is also possible in cases in which there are three or more antennas. Even in cases in which there are three or more antennas, the wireless roadside device 100 can appropriately perform both road-to-vehicle communication and road-to-road communication, as in the first embodiment, by selecting an antenna to be used as a transmitting antenna depending on the communication partner. In cases in which there are three or more antennas, the wireless circuit 120 will also have three or more wireless circuits depending on the number of antennas.

[0074] [Other embodiments] A program may be provided that causes a computer to execute each process according to the above-described embodiments. The program may be recorded on a computer-readable medium. The computer-readable medium can be used to install the program 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. Such a recording medium may be included in the control unit 130. The control unit 130 may realize each function described in the above-described embodiments by reading and executing the program from the recording medium. Therefore, the control unit 130 may be configured as a processor or controller such as a CPU (Central Processing Unit) or a DSP (Digital Signal Processor).

[0075] Although the embodiments have been described in detail above with reference to the drawings, the specific configuration is not limited to the above, and various design changes can be made without departing from the spirit of the invention. Furthermore, it is also possible to combine the embodiments, operation examples, or processes within a consistent range.

[0076] (Addendum) (Appendix 1) a first wireless roadside unit; an in-vehicle communication device mounted on the vehicle; a second wireless roadside device capable of wireless communication with the first wireless roadside device and the in-vehicle communication device, The second wireless roadside device A plurality of antennas; a control unit that selects the antenna to be used as a transmitting antenna from among the plurality of antennas in accordance with a communication partner. Transportation communication systems.

[0077] (Appendix 2) The communication partner is either the first wireless roadside device or the in-vehicle communication device. 1. A transport communication system as described in Appendix 1.

[0078] (Appendix 3) The control unit When the communication partner is the in-vehicle communication device, a first antenna determined by an operator is selected as the transmitting antenna from among the plurality of antennas; When the communication partner is the first wireless roadside device, the second wireless roadside device selects one of the plurality of antennas as the transmitting antenna according to wireless quality when the second wireless roadside device performs the wireless communication with the first wireless roadside device. 10. A transport communication system according to claim 1 or 2.

[0079] (Appendix 4) the second wireless roadside device has a storage unit that stores communication history information related to the wireless quality, The control unit selects the transmitting antenna based on the communication history information. 4. A transportation communication system according to any one of claims 1 to 3.

[0080] (Appendix 5) the control unit associates the wireless quality of each antenna with respect to the wireless signal received from the first wireless roadside device with the first wireless roadside device and stores the wireless quality as the communication history information in the storage unit; The control unit selects, based on the communication history information, the antenna having the best wireless quality for the first wireless roadside device as the transmitting antenna for the first wireless roadside device. 5. A transportation communication system according to any one of claims 1 to 4.

[0081] (Appendix 6) When performing wireless transmission to a third wireless roadside device that has not received the wireless signal in the past, the control unit selects an antenna determined by an operator from among the plurality of antennas as the transmitting antenna. 6. A transportation communication system according to any one of Supplementary Note 1 to Supplementary Note 5.

[0082] (Appendix 7) The wireless quality is at least one of a received signal strength indicator (RSSI), a signal-to-interference ratio (SIR), a signal-to-interference-plus-noise ratio (SINR), a reference signal received power (RSRP), and a reference signal received quality (RSRQ). 7. A transportation communication system according to any one of Supplementary Note 1 to Supplementary Note 6.

[0083] (Appendix 8) the wireless communication between the second wireless roadside device and the first wireless roadside device is road-to-road communication, and the wireless communication between the second wireless roadside device and the in-vehicle communication device is road-to-vehicle communication, The road-to-road communication and the road-to-vehicle communication are performed by using different pre-assigned time slots, respectively; The control unit determines whether the communication partner is the first wireless roadside device or the in-vehicle communication device based on a time slot number representing each time slot. 8. A transportation communication system according to any one of Supplementary Note 1 to Supplementary Note 7.

[0084] (Appendix 9) A traffic communication method in a traffic communication system having a first wireless roadside device, an in-vehicle communication device mounted on a vehicle, and a second wireless roadside device capable of wireless communication with the first wireless roadside device and also capable of wireless communication with the in-vehicle communication device, comprising: a step in which the second wireless roadside device having a plurality of antennas selects the antenna to be used as a transmitting antenna from among the plurality of antennas in accordance with a communication partner. Transportation and communication methods.

[0085] (Appendix 10) A wireless roadside device capable of wireless communication with other wireless roadside devices and wireless communication with an in-vehicle communication device mounted on a vehicle, A plurality of antennas; a control unit that selects the antenna to be used as a transmitting antenna from among the plurality of antennas in accordance with a communication partner. Wireless trackside machine. [Explanation of symbols]

[0086] 10: Traffic communication system 100: Wireless roadside unit 110(110-1,110-2): Antenna 120(120-1,120-2): Radio circuit 130: Control unit 131: Wireless control function unit 132: Slot determination function unit 133: Reception quality determination function unit 134: Transmitting antenna determination function unit 200 (200-1, 200-2, 200-3): Vehicle 250 (250-1, 250-2, 250-3): In-vehicle communication device

Claims

1. a first wireless roadside unit; an in-vehicle communication device mounted on the vehicle; a second wireless roadside device capable of wireless communication with the first wireless roadside device and the in-vehicle communication device, The second wireless roadside device A plurality of antennas; Memory and a control unit that selects the antenna to be used as a transmitting antenna from among the plurality of antennas in accordance with a communication partner, The control unit When the communication partner is the in-vehicle communication device, a first antenna determined by an operator is selected as the transmitting antenna from among the plurality of antennas; When the communication partner is the first wireless roadside device, selecting one of the plurality of antennas as the transmitting antenna in accordance with wireless quality when the second wireless roadside device performs the wireless communication with the first wireless roadside device, the wireless communication between the second wireless roadside device and the first wireless roadside device is road-to-road communication, and the wireless communication between the second wireless roadside device and the in-vehicle communication device is road-to-vehicle communication, The road-to-road communication and the road-to-vehicle communication are performed by using different pre-assigned time slots, respectively; The control unit determining whether the communication partner is the first wireless roadside device or the in-vehicle communication device based on a time slot number representing each of the time slots; When it is determined that the communication partner is the first wireless roadside device, information indicating the wireless quality is stored in the memory; If it is determined that the communication partner is the in-vehicle communication device, the process ends without acquiring the wireless quality of the received signal. Transportation communication systems.

2. the second wireless roadside device has a storage unit that stores communication history information related to the wireless quality, The control unit selects the transmitting antenna based on the communication history information.

2. The transportation communication system according to claim 1.

3. the control unit associates the wireless quality of each antenna with respect to the wireless signal received from the first wireless roadside device with the first wireless roadside device and stores the wireless quality as the communication history information in the storage unit; The control unit selects, based on the communication history information, the antenna having the best wireless quality for the first wireless roadside device as the transmitting antenna for the first wireless roadside device.

3. The transportation communication system according to claim 2.

4. When performing wireless transmission to a third wireless roadside device that has not received the wireless signal in the past, the control unit selects an antenna determined by an operator from among the plurality of antennas as the transmitting antenna.

2. The transportation communication system according to claim 1.

5. The wireless quality is at least one of a received signal strength indicator (RSSI), a signal-to-interference ratio (SIR), a signal-to-interference-plus-noise ratio (SINR), a reference signal received power (RSRP), and a reference signal received quality (RSRQ).

5. A transportation communication system according to claim 1.

6. A traffic communication method in a traffic communication system having a first wireless roadside device, an on-board communication device mounted on a vehicle, and a second wireless roadside device capable of wireless communication with the first wireless roadside device and having a plurality of antennas and a memory capable of wireless communication with the on-board communication device, comprising: the wireless communication between the second wireless roadside device and the first wireless roadside device is road-to-road communication, and the wireless communication between the second wireless roadside device and the in-vehicle communication device is road-to-vehicle communication, The road-to-road communication and the road-to-vehicle communication are performed by using different pre-assigned time slots, respectively; a step in which the second wireless roadside device determines whether a communication partner is the first wireless roadside device or the in-vehicle communication device based on a time slot number representing each of the time slots; when the second wireless roadside device determines that the communication partner is the first wireless roadside device, storing information indicating the wireless quality in the memory, and selecting one of the plurality of antennas as a transmitting antenna according to the wireless quality when the second wireless roadside device performs the wireless communication with the first wireless roadside device; and when the second wireless roadside device determines that the communication partner is the in-vehicle communication device, the second wireless roadside device selects a first antenna, which is determined by an operator, from the plurality of antennas as a transmitting antenna, and ends the process without acquiring wireless quality of the received signal. Transportation and communication methods.

7. A wireless roadside device capable of wireless communication with other wireless roadside devices and wireless communication with an in-vehicle communication device mounted on a vehicle, A plurality of antennas; Memory and a control unit that selects the antenna to be used as a transmitting antenna from among the plurality of antennas in accordance with a communication partner, the wireless communication with the other wireless roadside device is road-to-road communication, and the wireless communication with the in-vehicle communication device is road-to-vehicle communication, The road-to-road communication and the road-to-vehicle communication are performed by using different pre-assigned time slots, respectively; The control unit determining whether the communication partner is the other wireless roadside device or the in-vehicle communication device based on a time slot number representing each of the time slots; when it is determined that the communication partner is the other wireless roadside device, storing information indicating wireless quality when the wireless communication is performed with the other wireless roadside device in the memory, and selecting one of the plurality of antennas as the transmitting antenna in accordance with the wireless quality; If it is determined that the communication partner is the in-vehicle communication device, a first antenna determined by an operator is selected as the transmitting antenna from among the plurality of antennas, and the processing is terminated without obtaining the wireless quality of the received signal. Wireless trackside machine.

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