Communication method and communication apparatus

Abstract

The present disclosure relates to a communication method and a communication apparatus. A communication method configured to be executed by a first access point included in a plurality of access points in a communication system configured to communicate with a user apparatus, the communication method comprising: transmitting a first control signal for controlling communication with the user apparatus in a first frequency band; performing data communication with the user apparatus in the first frequency band; and transmitting a second control signal in a second frequency band in the data communication with the user apparatus, the second control signal being a signal for requesting one or more other access points to stop transmitting the first control signal. The user apparatus is a mobile user apparatus.

Description

Technical Field

[0001] This disclosure relates to wireless communication methods and wireless communication devices. Background Technology

[0002] There exists a technology for switching user terminals between multiple access points in a wireless LAN environment (e.g., Japanese Patent Application Publication No. 2023-171664 and "Wi-Fi Easy Mesh", [online], Wi-Fi Alliance, [retrieved November 19, 2024], Internet).<URL:https: / / www.wi-fi.org / ja / discover-wi-fi / wi-fi-easymesh> ). Summary of the Invention

[0003] This disclosure improves communication performance in wireless communication systems that include multiple access points.

[0004] The first aspect of this disclosure is a communication method configured to be performed by a first access point included among the plurality of access points in a communication system configured for communication between a user device and a plurality of access points. The user device is a mobile user device. The communication method includes: transmitting a first control signal in a first frequency band for controlling communication with the user device; performing data communication with the user device in the first frequency band; and, during the data communication with the user device, transmitting a second control signal in a second frequency band, the second control signal being a signal requesting one or more other access points to stop transmitting the first control signal.

[0005] In the communication method of the first aspect of this disclosure, the first access point may also be configured to continuously transmit the second control signal during data communication with the user device.

[0006] The communication method of the first aspect of this disclosure may also further include: stopping the transmission of the first control signal when the first access point is receiving the second control signal from one or more other access points. The first control signal may also include a signal that is periodically transmitted for the purpose of detecting the user equipment.

[0007] In the communication method of the first aspect of this disclosure, the second frequency band may also be a frequency band with a communication range wider than the first frequency band.

[0008] In the communication method of the first aspect of this disclosure, the second control signal may also be an unmodulated signal.

[0009] In the communication method of the first aspect of this disclosure, the communication system may also be a switchable communication system. The second frequency band may be a frequency band used to share information related to the user equipment of the switching target with one or more other access points belonging to the same group.

[0010] The communication method of the first aspect of this disclosure may also further include: transmitting a third control signal in the second frequency band, the third control signal being a signal for sharing information related to the user equipment of the switching object with one or more other access points. The communication system may also be a communication system capable of performing the switching.

[0011] The second aspect of this disclosure is a communication device that functions as a first access point in a communication system configured for communication between a user device and multiple access points. The user device is a mobile user device. The communication device includes a control unit. The control unit is configured to transmit a first control signal in a first frequency band for controlling communication with the user device, to perform data communication with the user device in the first frequency band, and to transmit a second control signal in a second frequency band during data communication with the user device. This second control signal is a signal requesting one or more other access points to stop transmitting the first control signal.

[0012] In the communication device of the second aspect of this disclosure, the control unit may also be configured to continuously transmit the second control signal during data communication with the user device.

[0013] In the communication device of the second aspect of this disclosure, the first control signal may include a signal that is periodically transmitted in order to detect the user device, and the control unit may be configured to stop the transmission of the first control signal when receiving the second control signal from one or more other access points.

[0014] In the communication device of the second aspect of this disclosure, the second frequency band may also be a frequency band with a communication range wider than the first frequency band.

[0015] In the communication device of the second aspect of this disclosure, the second control signal may also be an unmodulated signal.

[0016] In the communication apparatus of the second aspect of this disclosure, the communication system may also be a switchable communication system. The second frequency band may also be a frequency band used to share information related to the user equipment of the switching target with one or more other access points belonging to the same group.

[0017] In the communication device of the second aspect of this disclosure, the communication system may also be a switchable communication system. The control unit may also be configured to transmit a third control signal in the second frequency band, which is a signal for sharing information related to the user device of the switching target with one or more other access points.

[0018] Alternatively, other methods include apparatus for performing the above method, a program for causing a computer to perform the method, or a computer-readable storage medium that non-temporarily stores the program.

[0019] According to this disclosure, communication performance can be improved in wireless communication systems containing multiple access points. Attached Figure Description

[0020] The features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will now be described with reference to the accompanying drawings, in which the same reference numerals denote the same elements, and wherein:

[0021] Figure 1 This is a schematic diagram illustrating the implementation of the communication system.

[0022] Figure 2 This is a hardware structure diagram of the vehicle-mounted device according to the implementation method.

[0023] Figure 3 This is a hardware structure diagram of the roadside device in the implementation method.

[0024] Figure 4 This is a software structure diagram of the vehicle-mounted device according to the implementation method.

[0025] Figure 5 This is a software structure diagram of the roadside device in the implementation method.

[0026] Figure 6 It is a flowchart illustrating the stages of execution of each device.

[0027] Figure 7 It is a sequence diagram that represents the flow of data in the connection and transmission / reception phases.

[0028] Figure 8 It is a timing diagram that represents the flow of data during the switching phase. Detailed Implementation

[0029] In wireless LAN environments such as Wi-Fi (registered trademark), there exist systems capable of switching user terminals between multiple access points. In such systems, for example, the authentication results of the user terminal are shared among multiple access points. Therefore, even if the user terminal moves or the access point to the connection destination changes, the authentication process can be omitted, and reconnection can be achieved in a short time.

[0030] Furthermore, there is a growing desire to apply Wi-Fi-based communication methods to high-speed mobile devices. For example, mobile communication could be achieved at a low cost by configuring multiple access points along main roads and switching between them.

[0031] Wi-Fi access points typically send two types of frames: control frames for communication with user terminals and data frames. However, when multiple Wi-Fi access points are configured at short intervals, interference can occur between data frames sent by one access point and control frames sent by adjacent access points, potentially leading to increased error rates or reduced data communication speeds.

[0032] The communication method disclosed herein solves such a problem.

[0033] One aspect of the communication method disclosed herein is performed by a first access point included among the multiple access points in a communication system in which a mobile user device communicates with multiple access points. The communication method performs the following actions: transmitting a first control signal in a first frequency band for controlling communication with the user device; performing data communication with the user device in the first frequency band; and during the data communication with the user device, transmitting a second control signal in a second frequency band, the second control signal being a signal requesting other access points to stop transmitting the first control signal.

[0034] The first access point is one of a plurality of access points capable of communicating with a mobile user device. The plurality of access points could also be, for example, a plurality of roadside devices positioned at predetermined intervals along a road.

[0035] The first access point transmits and receives both control frames (first control signals) and data frames in the first frequency band for controlling communication with user equipment.

[0036] On the other hand, when multiple access points are configured close together, problems such as interference between control frames and data frames may occur. For example, during data communication between the first access point and the user equipment, interference may occur in control frames (first control signals) sent from the adjacent second access point.

[0037] To solve this problem, during data communication with the user equipment, the first access point sends a signal in the second frequency band requesting other access points to stop sending the first control signal, namely the second control signal.

[0038] The first access point can also continuously transmit the second control signal during data communication with the user equipment. Other access points stop transmitting the first control signal while receiving the second control signal.

[0039] The second frequency band is, for example, a frequency band used for information sharing among multiple access points belonging to the same group, and is a sub-frequency band different from the frequency band (first frequency band) used for the main data communication with user equipment.

[0040] Typically, the first frequency band is a lower frequency band than the second frequency band. For example, if the second frequency band is a gigahertz band, the first frequency can be set to a megahertz band.

[0041] The transmission of the second control signal stops, for example, when communication with the user device ends at the first access point.

[0042] This structure reduces electromagnetic interference between adjacent access points. In particular, since the transmission of the first control signal is stopped using a frequency band different from the frequency band used for data communication, it does not affect the main data communication, thus reducing interference.

[0043] Alternatively, the second frequency band can also be a frequency band with a communication range wider than the first frequency band.

[0044] The second frequency band is used for information sharing among multiple access points, and therefore is preferably a frequency band with a wider communication range than the first frequency band. For example, the second frequency band can be a frequency band less than 5 GHz, while the first frequency band can be a frequency band greater than 5 GHz.

[0045] It should be noted that the second control signal can also be transmitted as an unmodulated signal as long as it can request the first control signal to stop transmitting.

[0046] The second frequency band may also be a frequency band for transmitting a third control signal used to share information related to the user equipment with other access points.

[0047] The third control signal can be configured, for example, as a signal for sharing the authentication results of a user device among access points, or as a signal for sharing information related to the user device of an object among multiple access points during a handover.

[0048] The following describes specific embodiments of this disclosure based on the accompanying drawings. Unless otherwise specified, the hardware structures, module structures, and functional structures described in each embodiment are not intended to limit the scope of the disclosed technology to them.

[0049] First Implementation Method

[0050] System Overview

[0051] Reference Figure 1An overview of the communication system according to the first embodiment will be described. The communication system of this embodiment is configured to include an on-board unit 10 mounted on a vehicle and a plurality of roadside units 20 disposed along the road. The roadside units 20 are an example of "access points".

[0052] It should be noted that, in Figure 1 In the examples, roadside devices 20A, 20B, and 20C are shown, but when there is no need to distinguish them, they are collectively referred to as "roadside device 20".

[0053] The communication system of this embodiment is a system that performs wireless communication through communication procedures specified by IEEE 802.11. Multiple roadside devices 20 have a common group address for identifying the group and a local address specific to each device. The group may also correspond to a mobility domain in the IEEE 802.11 standard.

[0054] Multiple roadside devices 20 can also belong to a common BSS (Basic Service Set). The on-board unit 10, as a user device, can access any roadside device 20 and accept authentication using common identifiers such as group address and BSSID. The authentication result is shared among multiple roadside devices 20, so the on-board unit 10 can change the roadside device 20 to the destination without having to perform authentication procedures again.

[0055] Roadside devices 20A, 20B, and 20C each have a range (e.g., a radius of approximately 100 meters) capable of data communication with the vehicle-mounted device 10. Figure 1 (The dashed line diagram).

[0056] The vehicle-mounted device 10 can connect to and communicate with any roadside device 20 while in motion. Furthermore, during communication, it can switch to connect to the roadside device 20 at its destination.

[0057] In a Wi-Fi communication system, an access point (roadside device 20) periodically sends beacon frames (an example of the “first control signal” in this disclosure) to discover user devices (vehicle-mounted devices 10). Upon receiving the beacon frame, the user device (vehicle-mounted device 10) determines the access point (roadside device 20) as a candidate connection destination.

[0058] However, when beacon frames are transmitted in the same frequency band (band 1) as those used for data communication, interference sometimes occurs between multiple access points.

[0059] For example, when the vehicle-mounted device 10 is communicating with the roadside device 20A, beacon frames sent by the roadside device 20B may sometimes reach the vehicle-mounted device 10. In this case, since both devices use the same communication channel, interference may occur, potentially leading to problems such as increased error rates or reduced data communication speeds.

[0060] Therefore, in this embodiment, during data communication with the vehicle-mounted device 10, each roadside device 20 sends a signal requesting the cessation of beacon frame transmission (referred to as the "second control signal" in this disclosure, hereinafter referred to as the stop request signal) to surrounding roadside devices 20. Upon receiving this signal, the roadside device 20 stops the periodic transmission of beacon frames. The transmission of the stop request signal ends when the source roadside device 20 terminates data communication.

[0061] Furthermore, in the communication system of this embodiment, each roadside device 20 is configured to communicate with the vehicle-mounted device 10 in both the first and second frequency bands, and the stop request signal is transmitted in the second frequency band.

[0062] The first frequency band is used for primary data communication, typically 5GHz or higher, such as 5GHz or 60GHz. This band is characterized by its ability to perform high-speed data communication, but its communication range is relatively short, ranging from tens to hundreds of meters.

[0063] The second frequency band is used for subordinate data communication, typically a sub-5GHz band such as 2.4GHz. The sub-5GHz band has the following characteristics: the data communication speed is lower than that of bands above 5GHz (e.g., the 60GHz band), but the communication range is several times greater (e.g., several hundred meters).

[0064] exist Figure 1 In the example, the dashed line represents the communicable range of the first frequency band. The communicable range of the second frequency band is wider than the range shown by the dashed line.

[0065] In this embodiment, the roadside device 20 has the function of data communication with the vehicle-mounted device 10 in a first frequency band. Additionally, the roadside device 20 has the function of sharing information with other roadside devices 20 using a second frequency band. Signals transmitted and received in the second frequency band (the third control signal in this disclosure) can be configured, for example, as signals for sharing the authentication results of the vehicle-mounted device 10 among roadside devices, and signals for sharing and switching information related to the vehicle-mounted device 10 among multiple roadside devices 20.

[0066] By using a second frequency band with a communication range greater than that of the first frequency band to send a stop request signal, it is possible to request the cessation of beacon frame transmission from more roadside devices 20.

[0067] Hardware Structure

[0068] Next, the hardware structure of each device that makes up the system will be described.

[0069] Figure 2 This is a schematic diagram illustrating an example of the hardware structure of an onboard device 10 that can be mounted on a vehicle.

[0070] The vehicle-mounted device 10 can be configured as a computer with a processor (CPU, GPU, etc.), main storage (RAM, ROM, etc.), and auxiliary storage (EPROM, hard disk drive, removable media, etc.). The auxiliary storage stores an operating system (OS), various programs, various tables, etc. By executing the programs stored therein, various functions (software modules) that meet a predetermined purpose can be achieved, as described later. Some or all of these functions can also be implemented as hardware modules using hardware circuits such as ASICs or FPGAs.

[0071] The vehicle-mounted device 10 is configured to include a control unit 101, a storage unit 102, a communication unit 103, a location information acquisition unit 104, and an input / output unit 105.

[0072] The control unit 101 is a computing unit that executes predetermined programs to implement various functions of the vehicle-mounted device 10. The control unit 101 can be implemented, for example, by a hardware processor such as a CPU. Alternatively, the control unit 101 may be configured to include RAM, ROM (Read Only Memory), cache memory, etc.

[0073] The storage unit 102 is a component for storing information and is composed of storage media such as RAM, disk, and flash memory. The storage unit 102 stores the program executed by the control unit 101 and the data used by the program.

[0074] The communication unit 103 is a wireless communication interface for transmitting and receiving wireless signals. The communication unit 103 is configured to transmit and receive wireless signals conforming to standards such as wireless LAN. Furthermore, the communication unit 103 can transmit and receive these wireless signals in two different frequency bands. In this embodiment, the communication unit 103 can transmit and receive wireless signals in two frequency bands: a frequency band above 5 GHz (first frequency band) and a frequency band below 5 GHz (second frequency band).

[0075] The location information acquisition unit 104 acquires the location information of vehicle 1. The location information acquisition unit 104 includes a GPS antenna and a positioning module for locating the location information. The GPS antenna is an antenna that receives positioning signals transmitted from positioning satellites (also known as GNSS satellites). The positioning module is a module that calculates the location information based on the signals received by the GPS antenna. It should be noted that the location information acquisition unit 104 can also determine the direction of travel of vehicle 1 based on the shift of the location information.

[0076] The input / output unit 105 is a unit that receives input from vehicle occupants and provides them with information. Specifically, the input / output unit 105 consists of a touch panel and its control components, and a liquid crystal display and its control components. In this embodiment, the touch panel and the liquid crystal display are combined into a single touch panel display.

[0077] Next, the hardware structure of the roadside device 20 will be explained. Figure 3 This is a diagram that schematically illustrates an example of the hardware structure of the roadside device 20.

[0078] Like the vehicle-mounted device 10, the roadside device 20 can be configured as a computer with a processor (CPU, GPU, etc.), main storage device (RAM, ROM, etc.), and auxiliary storage device (EPROM, hard disk drive, removable media, etc.).

[0079] The roadside device 20 is configured to include a control unit 201, a storage unit 202, and a communication unit 203.

[0080] The control unit 201 is a computing unit that executes predetermined programs to realize various functions of the roadside device 20. The control unit 201 can be implemented, for example, by a hardware processor such as a CPU. Alternatively, the control unit 201 may be configured to include RAM, ROM (Read Only Memory), cache memory, etc.

[0081] The storage unit 202 is a component for storing information and is composed of storage media such as RAM, disk, and flash memory. The storage unit 202 stores programs executed by the control unit 201 and the data used by those programs.

[0082] Communication unit 203 is a wireless communication interface for transmitting and receiving wireless signals between itself and the vehicle-mounted device 10. Communication unit 203 is configured to transmit and receive wireless signals conforming to standards such as wireless LAN. Like communication unit 103, communication unit 203 can transmit and receive these wireless signals in two different frequency bands.

[0083] Software Structure

[0084] Next, the software structure of each device that makes up the system will be explained. Figure 4 This diagram schematically illustrates the software structure of the vehicle-mounted device 10 according to this embodiment. The hardware structure of the vehicle-mounted device 10 is as follows: Figure 2 As shown.

[0085] In this embodiment, the control unit 101 of the vehicle-mounted device 10 is configured to have a communication control unit 1011 as a software module. This software module can also be implemented by the control unit 101 (CPU, etc.) executing a program stored in the storage unit 102. It should be noted that information processing performed by the software module is synonymous with information processing performed by the control unit 101 (CPU, etc.).

[0086] The communication control unit 1011 establishes a connection with any one of the multiple roadside devices 20 and performs data transmission and reception processing (including handover processing).

[0087] First, the communication control unit 1011 detects the presence of the roadside device 20 included in the communication system and executes a step of requesting a connection to the communication system. In this step, the communication control unit 1011 receives a beacon frame sent from the roadside device 20, and in response, performs authentication procedures using pre-stored authentication information. Authentication information refers to, for example, an identifier used to uniquely identify the vehicle-mounted device 10, a key used to connect the vehicle-mounted device 10 to the communication system, or an electronic certificate. It should be noted that the authentication information stored in the vehicle-mounted device 10 and the authentication information sent to the roadside device 20 may be different. For example, if the vehicle-mounted device 10 stores a private key, a hash value generated based on that private key may also be sent to the roadside device 20. Thus, a connection is established between the vehicle-mounted device 10 and the communication system.

[0088] Second, the communication control unit 1011 performs data transmission and reception between the vehicle-mounted device 10 and the roadside device 20, and performs handover of the connection destination with other roadside devices 20 as needed.

[0089] The specific control methods will be described later.

[0090] Next, the software structure of the roadside device 20 will be explained. Figure 5 This diagram schematically illustrates the software structure of the roadside device 20 according to this embodiment. The hardware structure of the roadside device 20 is as follows: Figure 3 As shown.

[0091] In this embodiment, the control unit 201 of the roadside device 20 is configured with two software modules: a communication control unit 2011 and an authentication unit 2012. Each software module can also be implemented by the control unit 201 (CPU, etc.) executing a program stored in the storage unit 202. It should be noted that information processing performed by the software modules is synonymous with information processing performed by the control unit 201 (CPU, etc.).

[0092] The communication control unit 2011 performs data communication with the vehicle-mounted device 10. Specifically, the communication control unit 2011 performs the following processing.

[0093] (1) Broadcast a signal for discovering the vehicle-mounted device 10, and perform authentication processing based on the request from the vehicle-mounted device 10.

[0094] The communication control unit 2011 periodically broadcasts beacon frames for discovering the vehicle-mounted device 10. Upon receiving a response from the vehicle-mounted device 10, the communication control unit 2011 performs a handshake with the vehicle-mounted device 10, including authentication processing. Authentication processing is performed by the authentication unit 2012, described later. It should be noted that if authentication results regarding the target vehicle-mounted device 10 have already been received from other roadside devices 20, the authentication processing (described later) is omitted. The transmission of beacon frames and authentication processing are performed using the first frequency band.

[0095] (2) Data communication processing with the vehicle-mounted device 10

[0096] Upon completion of the handshake with the vehicle-mounted device 10, the communication control unit 2011 initiates data communication with the vehicle-mounted device 10. Data communication takes place in the first frequency band. Data communication can also be performed, for example, by repeatedly transmitting multiple data blocks and receiving block Acks.

[0097] Furthermore, the communication control unit 2011 has the function of controlling the switching between multiple roadside devices 20. For example, based on the communication status with the vehicle-mounted device 10, the communication control unit 2011 decides to switch the connection destination of the vehicle-mounted device 10 to another roadside device 20 (switching). For example, the communication control unit 2011 determines another roadside device 20 that becomes the new connection destination of the vehicle-mounted device 10 and sends information related to that roadside device 20 to the vehicle-mounted device 10. This information includes information related to the candidate roadside device 20 that becomes the connection destination. This information is transmitted using the first frequency band. The vehicle-mounted device 10 can use this information to switch the roadside device 20 to the connection destination. In addition, the communication control unit 2011 sends information related to the vehicle-mounted device 10 to other roadside devices 20 that become candidates for switching destinations. This information is transmitted using the second frequency band.

[0098] In addition, during data communication with the vehicle-mounted device 10, the communication control unit 2011 continuously transmits stop request signals using the second frequency band. The stop request signal can be broadcast or unicast to other roadside devices 20 that may cause interference.

[0099] The communication control unit 2011 terminates the transmission of the stop request signal when the data communication between this device and the vehicle-mounted device 10 ends.

[0100] It should be noted that the communication control unit 2011 stops sending the aforementioned beacon frames while receiving a stop request signal from other roadside devices 20.

[0101] The authentication unit 2012 performs authentication of the vehicle-mounted device 10 based on a request from the communication control unit 2011. The authentication unit 2012 may also perform authentication based on a PSK (Pre-Shared Key). In this case, the authentication information becomes a key generated based on a passphrase. Alternatively, the authentication unit 2012 may also perform IEEE 802.1x authentication. In this case, the authentication information becomes a combination of a username and password or an electronic certificate.

[0102] Furthermore, if the on-board unit 10 successfully authenticates, the authentication unit 2012 sends the authentication result to other roadside units 20 belonging to the same communication system. This information is transmitted using the second frequency band. Therefore, other roadside units 20 can continue communication without re-authenticating in the event of a handover.

[0103] Processing flowchart

[0104] Next, the processing flow in the communication will be explained. Figure 6 This diagram illustrates the stages of processing performed by the vehicle-mounted device 10 and the roadside device 20 in this embodiment. In this example, the scenario is described as a vehicle equipped with the vehicle-mounted device 10 traveling on a road where multiple roadside devices 20 are provided.

[0105] The initial phase (P1) is the connection phase (connection phase) in which the on-board unit 10 identifies the presence of the roadside unit 20 and initiates a handshake with the communication system. During the connection phase, the on-board unit 10 receives a beacon frame from the roadside unit 20 and, in response, requests a handshake from the communication system. The handshake is performed via the transmission of probe requests, authentication requests, association requests, etc. This data is transmitted in the first frequency band. The roadside unit 20, having established a connection with the on-board unit 10 after receiving a handshake request from it, performs authentication of the on-board unit 10. The authentication result is shared with the other roadside units 20 included in the communication system via the second frequency band.

[0106] Multiple roadside devices 20 can each identify that the vehicle-mounted device 10 has been authenticated by the communication system based on the acquired authentication results.

[0107] The next stage (P2) is the stage where the on-board unit 10 and the roadside unit 20 transmit and receive data (transmission and reception stage).

[0108] Once the connection between the on-board unit 10 and the roadside unit 20 is established and authentication of the on-board unit 10 is completed, data communication begins between the on-board unit 10 and the roadside unit 20. During the transmission and reception phase, for example, multiple data blocks can be repeatedly transmitted and block Acks can be received.

[0109] When predetermined conditions are met during the transmission and reception phase, the process transitions to the phase of determining a handover. Predetermined conditions could include, for example, a communication quality between the vehicle-mounted device 10 and the roadside device 20 falling below a predetermined value.

[0110] During the handover determination phase (P3), the roadside device 20 communicating with the on-board unit 10 determines that there are other roadside devices 20 capable of handover. If handover is possible, the roadside device 20 sends information to the on-board unit 10 related to other roadside devices 20 that could become the handover destination, and the on-board unit 10 performs the connection to the destination handover. If no roadside device 20 is capable of handover, communication ends.

[0111] Next, the processing performed by each device in each of the aforementioned stages will be explained in detail.

[0112] Figure 7 This is a timing diagram of the data transmitted and received between the vehicle-mounted device 10 and the roadside device 20 during the connection and transmission / reception phases. It should be noted that, in this example, the access point for the initial communication of the vehicle-mounted device 10 is set as the roadside device 20A, and the access point for switching destinations is set as the roadside device 20B.

[0113] First, roadside devices 20A and 20B begin periodically transmitting beacon frames. A beacon frame is data broadcast by roadside device 20 in the first frequency band to notify of the device's presence.

[0114] When the vehicle-mounted device 10 receives a beacon frame from the roadside device 20, the vehicle-mounted device 10 begins the procedures for connecting to the roadside device 20.

[0115] The beacon frame contains the identifier of the roadside device 20, and the vehicle-mounted device 10 sends a probe request to the roadside device 20 containing the identifier of the roadside device 20 to which it wishes to connect.

[0116] It should be noted that when receiving beacon frames from multiple roadside devices 20, the vehicle-mounted device 10 can also select the roadside device 20 with the strongest signal strength. Here, it is assumed that the vehicle-mounted device 10 selects roadside device 20A as the connection destination and sends a detection request to roadside device 20A.

[0117] When the roadside device 20A receives a detection request sent to it, the roadside device 20A stops sending beacon frames (step S12) and sends a detection response containing network information of the roadside device 20A to the vehicle-mounted device 10.

[0118] Upon receiving the detection response, the vehicle-mounted device 10 sends an authentication request to the roadside device 20A. The authentication request may also include authentication information (key information, etc.) possessed by the vehicle-mounted device 10.

[0119] Upon receiving an authentication request, the roadside device 20A proceeds to the step of authenticating the on-board device 10 (step S13). In step S13, the roadside device 20A (authentication unit 2012) authenticates the on-board device 10 based on the authentication information received from the on-board device 10. Authentication may be based on, for example, a PSK (Pre-Shared Key) or IEEE 802.1x authentication.

[0120] When the authentication of the vehicle-mounted device 10 is completed, the roadside device 20A performs processing to share the authentication result with other roadside devices 20 included in the communication system (step S14). For example, the roadside device 20A (authentication unit 2012) sends the authentication result performed in step S13 to the roadside device 20B belonging to the same communication system (e.g., roadside device 20B with the same group address as roadside device 20A). Thus, each roadside device 20 does not need to independently authenticate the vehicle-mounted device 10.

[0121] It should be noted that for the on-board unit 10 of the object, if the authentication unit 2012 has already received the shared authentication result from other roadside units 20, the authentication process is skipped.

[0122] Then, roadside device 20A begins broadcasting a signal requesting the cessation of beacon frame transmission (stop request signal) (step S15). The stop request signal is continuously transmitted until the cessation occurs. The stop request signal can also be an unmodulated signal (e.g., a pulse signal with a defined pulse width). Upon receiving the stop request signal, roadside device 20B stops the periodic transmission of beacon frames until the continuous transmission of the stop request signal is interrupted (step S16).

[0123] The aforementioned authentication results and stop request signals are transmitted via the second frequency band.

[0124] The second frequency band is a lower frequency band than the frequency band used for primary data communication (the first frequency band). Generally, as the frequency of radio waves decreases, the communication range increases due to diffraction attenuation characteristics. Therefore, the roadside device 20A can stop the transmission of beacon frames by the roadside device 20B before the vehicle-mounted device 10 enters the communication range of the roadside device 20B based on the first frequency band.

[0125] Upon completion of the aforementioned processing, a notification indicating that authentication is complete (authentication completion notification) is sent from the roadside device 20A to the vehicle-mounted device 10.

[0126] Once authentication is complete, the association request is sent from the vehicle-mounted device 10 to the roadside device 20A, and the association response is sent from the roadside device 20A to the vehicle-mounted device 10. It should be noted that additional procedures for encrypted communication can also be performed. Through the processes described above, the handshake between the vehicle-mounted device 10 and the communication system is completed.

[0127] When the handshake between the vehicle-mounted device 10 and the communication system is completed, data communication begins in step S17. Data communication can also be performed, for example, by sending data collected in the vehicle from the vehicle-mounted device 10 to the roadside device 20A. Data communication can also be carried out by repeatedly sending multiple data blocks and receiving block Acks.

[0128] It should be noted that, Figure 7 The order of some of the processes shown can also be changed. For example, the process of step S15 (the process of starting to send the stop request signal) can also be performed at any time before the process of step S17 is executed.

[0129] Figure 8 This is a timing diagram of the data transmitted and received between the on-board unit 10 and the roadside unit 20 during the handover phase. The process illustrated begins when the roadside unit 20A determines when to hand over communication from the on-board unit 10 to another roadside unit 20B. Whether a handover has been implemented can be determined, for example, based on the location information of the on-board unit 10, the electric field strength of the radio waves, the error rate of the communication, etc.

[0130] First, in step S21, the communication control unit 2011 begins the handover process. In this step, for example, based on information related to the movement of the vehicle-mounted device 10, the location information of the vehicle-mounted device 10, and the location information of other roadside devices 20, a candidate roadside device (in this example, roadside device 20B) is determined as the next access point (handover destination) to which the vehicle-mounted device 10 will connect. It should be noted that there can be multiple candidates for roadside devices.

[0131] When a roadside device is selected as a candidate for switching destination, the communication control unit 2011 of roadside device 20A terminates the transmission of the stop request signal, which was continued from step S15 (step S22). Upon detecting this situation, roadside device 20B resumes the transmission of beacon frames (step S23).

[0132] Additionally, the communication control unit 2011 of the roadside device 20A sends information related to the vehicle-mounted device 10 to the communication control unit 2011 of the roadside device 20B in the second frequency band. This information may also include the identifier of the vehicle-mounted device 10, its movement status, etc.

[0133] Additionally, the communication control unit 2011 of the roadside device 20A sends information related to the candidate roadside device as the switching destination to the vehicle-mounted device 10. Thus, the vehicle-mounted device 10 is able to identify the roadside device 20 that should be connected next.

[0134] When the identifier of the roadside device 20B, which serves as the destination for switching, is notified to the vehicle-mounted device 10, the vehicle-mounted device 10 initiates a connection with the roadside device 20B in response to a beacon frame sent from the roadside device 20B. It should be noted that when there are multiple candidate roadside devices for switching destinations, the vehicle-mounted device 10 can also determine the next roadside device to connect to based on factors such as radio wave conditions.

[0135] The connection procedures, starting with the reception of the beacon frame, are as follows: Figure 7 As explained. It should be noted that if the authentication result of the vehicle-mounted device 10 has been shared in advance, the authentication process is omitted and communication begins immediately.

[0136] As explained above, in communication with the vehicle-mounted device 10 utilizing the first frequency band, the roadside device 20 of the first embodiment requests the cessation of beacon frame transmission from a nearby roadside device 20 using the second frequency band.

[0137] According to this structure, interference between data communication frames and control frames can be avoided between adjacent roadside devices, enabling faster and more reliable data communication.

[0138] Variations

[0139] The above-described implementation is merely one example, and this disclosure can be implemented with appropriate modifications without departing from its spirit.

[0140] For example, the processes and components described in this disclosure can be freely combined and implemented as long as they do not create technical contradictions.

[0141] Furthermore, while the embodiment provides an example of sharing the authentication results and handover information of the vehicle-mounted device 10 among multiple roadside devices using the second frequency band, other information related to the vehicle-mounted device 10 can also be shared using the second frequency band. Such information could include, for example, the location information, attribute information, and information related to speed and direction of movement of the vehicle-mounted device 10.

[0142] Furthermore, while the embodiment provides an example of sending (uploading) data from the vehicle-mounted device 10 to the communication system, the direction of communication is not limited to this. Data can be sent from the communication system to the vehicle-mounted device 10, and data can be freely sent and received during communication periods.

[0143] In addition, in the implementation, the second frequency band is set to a frequency band less than 5 GHz, and the first frequency band is set to a frequency band greater than 5 GHz, but other frequency bands may also be used.

[0144] Furthermore, the implementation example provides an example of transmitting a beacon frame (first control signal) in the first frequency band and a stop request signal (second control signal) in the second frequency band. However, as long as the frequencies are different, the frequency bands (e.g., megahertz band and gigahertz band, 2.4 GHz band and 5 GHz band, etc.) do not necessarily need to be different. For example, the channels in a wireless LAN can be different.

[0145] Furthermore, the modulation scheme and bit rate of the signal transmitted in the first frequency band and the signal transmitted in the second frequency band can be different. The modulation scheme and bit rate can also be set in a way that widens the coverage area of ​​the signal transmitted in the second frequency band compared to the signal transmitted in the first frequency band.

[0146] Furthermore, while the embodiment illustrates sending the authentication result of the vehicle-mounted device 10 from roadside device 20A to roadside device 20B, it is also possible for three or more roadside devices to relay the received information to each other. Thus, information related to the vehicle-mounted device 10 can be shared among all roadside devices 20 included in the communication system.

[0147] In another embodiment, each roadside device 20 authenticates the vehicle-mounted device 10, but the authentication of the vehicle-mounted device 10 can also be performed by an external authentication server. In this case, the authentication server and each roadside device 20 can communicate wirelessly or via a wired connection. Even in this case, the authentication result of the vehicle-mounted device 10 is shared among all roadside devices 20 included in the communication system.

[0148] Furthermore, a process described as being performed by a single device can also be executed by multiple devices. Alternatively, a process described as being performed by different devices can also be executed by a single device. In a computer system, the hardware architecture (server architecture) used to implement each function can be flexibly changed.

[0149] This disclosure can also be implemented by supplying a computer program with the functions described in the above embodiments to a computer, which has one or more processors that read and execute the program. Such a computer program can be provided to the computer either by a non-transitory computer-readable storage medium connectable to the computer's system bus or via a network. Non-transitory computer-readable storage media include, for example, any type of disk such as a hard disk (floppy disk, hard disk drive (HDD), etc.), an optical disk (CD-ROM, DVD, Blu-ray disc, etc.), a read-only memory (ROM), a random access memory (RAM), an EPROM, an EEPROM, a magnetic card, a flash memory, an optical card, or any type of medium suitable for storing electronic instructions.

Claims

1. A communication method configured to be performed by a first access point included in a communication system configured for a user device to communicate with a plurality of access points, wherein the user device is a mobile user device, the communication method being characterized by comprising: A first control signal for controlling communication with the user equipment is transmitted in the first frequency band; Data communication with the user equipment is conducted in the first frequency band; as well as In data communication with the user equipment, a second control signal is transmitted in the second frequency band. This second control signal is a signal that requests one or more other access points to stop transmitting the first control signal.

2. The communication method according to claim 1, characterized in that, The first access point is configured to continuously transmit the second control signal during data communication with the user equipment.

3. The communication method according to claim 1, characterized in that, Also includes: If the first access point is receiving the second control signal from one or more other access points, the transmission of the first control signal is stopped, wherein the first control signal includes a signal that is periodically transmitted to detect the user equipment.

4. The communication method according to claim 1, characterized in that, The second frequency band is a frequency band with a communication range wider than the first frequency band.

5. The communication method according to claim 1, characterized in that, The second control signal is an unmodulated signal.

6. The communication method according to claim 1, characterized in that, The communication system is a switchable communication system; and The second frequency band is used to share information related to the user equipment of the switching object with one or more other access points belonging to the same group.

7. The communication method according to claim 1, characterized in that, Also includes: A third control signal is transmitted in the second frequency band. This third control signal is a signal for sharing information related to the user equipment of the switching object with one or more other access points, wherein the communication system is a communication system capable of performing the switching.

8. A communication device, in a communication system configured for a user device to communicate with multiple access points, the communication device functioning as a first access point, the user device being a mobile user device, characterized in that it includes a control unit configured to: A first control signal for controlling communication with the user equipment is transmitted in the first frequency band. Data communication with the user equipment is conducted in the first frequency band, and In data communication with the user equipment, a second control signal is transmitted in the second frequency band. This second control signal is a signal that requests one or more other access points to stop transmitting the first control signal.

9. The communication device according to claim 8, characterized in that, The control unit is configured to continuously transmit the second control signal during data communication with the user device.

10. The communication device according to claim 8, characterized in that, The first control signal includes signals that are periodically transmitted to detect the user equipment, and The control unit is configured to stop the transmission of the first control signal when it is receiving the second control signal from one or more other access points.

11. The communication device according to claim 8, characterized in that, The second frequency band is a frequency band with a communication range wider than the first frequency band.

12. The communication device according to claim 8, characterized in that, The second control signal is an unmodulated signal.

13. The communication device according to claim 8, characterized in that, The communication system is a switchable communication system; and The second frequency band is used to share information related to the user equipment of the switching object with one or more other access points belonging to the same group.

14. The communication device according to claim 8, characterized in that, The communication system is a switchable communication system, and The control unit is configured to transmit a third control signal in the second frequency band, the third control signal being a signal for sharing information related to the user device of the switching object with one or more other access points.

Images