JP7729621B2 - COMMUNICATION SYSTEM, COMMUNICATION DEVICE, COMMUNICATION METHOD, AND PROGRAM - Google Patents

Description

Article 30, Paragraph 2 of the Patent Act applies. Website address: https://www.silex.jp/backnumber/press/press_product_211216_sxpceax.html, published on December 16, 2021

The present invention relates to a communication system, a communication device, a communication method, and a program.

A base station system has been proposed that includes an accommodation station connected to a core network and equipped with a baseband unit that performs baseband processing and other operations in wireless communications, and an RF unit that functions as a wireless base station device that performs radio frequency processing and other operations in wireless communications (see, for example, Patent Document 1). In this base station system, the accommodation station and RF unit communicate via redundant communication lines.

JP 2016-163232 A

Furthermore, as one technology for making communication lines redundant, as described in Patent Document 1, a technology is being provided in which a wireless base station and a wireless terminal are each equipped with a single wireless module capable of wireless communication in multiple different frequency bands, and the same frames are transmitted and received in multiple frequency bands. However, when a wireless base station transmits frames received from a communication device that supports wireless communication technology using such multiple frequency bands to a communication device that does not support that technology, multiple identical frames will be transmitted to the communication device that does not support that technology, wasting the frequency band used for wireless communication between the two communication devices, and making it impossible to discard identical frames that are no longer needed, which could result in reduced throughput.

The present invention has been made in consideration of the above, and aims to provide a communication system, communication device, communication method, and program that can suppress a decrease in throughput even when there is a wireless communication device that does not support wireless communication using multiple frequency bands over multiple communication paths.

In order to achieve the above object, a communication system according to the present invention comprises:
A communication system including a first communication device, a second communication device capable of wireless communication with the first communication device, and a third communication device different from the first communication device capable of wireless communication with the second communication device,
The first communication device
a multiband communication capability notification unit that generates a management frame including multiband communication capability notification information for notifying the second communication device that the first communication device is capable of wireless communication via a plurality of frequency bands;
a first transmission control unit that, after transmitting the multiband communication capability notification information, adds data frame identification information to a data frame destined for the third communication device and transmits the data frame to the second communication device via each of the plurality of frequency bands;
the second communication device,
a multiband communication feasibility determination unit that determines that wireless communication between the first communication device and the first communication device is possible via the multiple frequency bands when the management frame transmitted from the first communication device includes the multiband communication capability notification information;
a frame acquisition unit that acquires, when it is determined that wireless communication with the first communication device is possible via the plurality of frequency bands, the data frames destined for the third communication device and transmitted from the first communication device via each of the plurality of frequency bands;
The communication device has a second transmission control unit that, when a management frame including multi-band communication capability notification information cannot be received from the third communication device and the multi-band communication capability determination unit determines that wireless communication with the third communication device is not possible via the multiple frequency bands, transmits the data frame addressed to the third communication device via one frequency band based on the data frame identification information.
Note that being able to perform wireless communication via multiple frequency bands means that wireless communication via multiple frequency bands is possible simultaneously and in parallel using two wireless communication interfaces, and multiple frequency bands refer to the 2.4 GHz band and the 5 GHz band (W52 band, W53 band, and W56 band), etc.

A communication device according to another aspect of the present invention comprises:
A communication device capable of wireless communication with another first communication device via a plurality of frequency bands, and capable of wireless communication with another second communication device different from the other first communication device,
a multiband communication feasibility determination unit that determines that wireless communication is possible between the other first communication device and the other first communication device via a plurality of frequency bands when multiband communication feasibility notification information that notifies that wireless communication is possible via the plurality of frequency bands is included in a management frame transmitted from the other first communication device;
a frame acquisition unit that acquires, when it is determined that wireless communication with the other first communication device via the plurality of frequency bands is possible, data frames that are transmitted from the other first communication device via each of the plurality of frequency bands and have data frame identification information assigned thereto and that are destined for the other second communication device;
and a transmission control unit that, when a management frame including multi-band communication capability notification information cannot be received from the other second communication device and the multi-band communication feasibility determination unit determines that wireless communication with the other second communication device is not possible via the multiple frequency bands, transmits the data frame having the other second communication device as its destination to the other second communication device via one frequency band based on the data frame identification information.

A communication method according to another aspect of the present invention comprises:
A communication method using a first communication device, a second communication device capable of wireless communication with the first communication device via a plurality of frequency bands, and a third communication device different from the first communication device capable of wireless communication with the second communication device via one frequency band,
generating, by the first communication device, a management frame including multi-band communication capability notification information for notifying the second communication device that the first communication device is capable of wireless communication via the multiple frequency bands;
a step in which, after the first communication device transmits the multiband communication capability notification information, the first communication device generates a data frame having data frame identification information assigned thereto and having the third communication device as a destination, and transmits the data frame to the second communication device via each of the plurality of frequency bands;
determining, by the second communication device, that wireless communication via the plurality of frequency bands is possible with the first communication device when the management frame transmitted from the first communication device includes the plurality of band communication capability notification information;
When it is determined that wireless communication between the second communication device and the first communication device is possible via the plurality of frequency bands, the second communication device acquires the data frames destined for the third communication device and transmitted from the first communication device via each of the plurality of frequency bands;
When the second communication device is unable to receive a management frame including multi-band communication capability notification information from the third communication device and determines that wireless communication with the third communication device is not possible via the multiple frequency bands, the second communication device transmits the data frame destined for the third communication device to the third communication device via one frequency band based on the data frame identification information.

From another viewpoint, the program according to the present invention is
Computer,
a multiband communication feasibility determination unit that determines that wireless communication is possible between the first communication device and another first communication device via a plurality of frequency bands when a management frame transmitted from the first communication device includes multiband communication feasibility notification information that notifies that wireless communication is possible via the plurality of frequency bands;
a frame acquisition unit that acquires, when it is determined that wireless communication with the other first communication device via the plurality of frequency bands is possible, data frames transmitted from the other first communication device via each of the plurality of frequency bands, the data frames including data frame identification information whose destination is a second communication device different from the other first communication device;
a transmission control unit that, when it is determined that a management frame including multi-band communication capability notification information cannot be received from the other second communication device and wireless communication with the other second communication device via the plurality of frequency bands is not possible, transmits the data frame having the other second communication device as a destination to the other second communication device via one frequency band based on the data frame identification information;
Function as.

In the communication system according to the present invention, the multiband communication feasibility determination unit determines that wireless communication using multiple frequency bands with the first communication device is possible when the management frame transmitted from the first communication device includes notification information indicating that multiband communication is possible. Furthermore, when the frame acquisition unit determines that wireless communication using multiple bands with the first communication device is possible, it acquires data frames destined for the third communication device and transmitted from the first communication device via each of the multiple frequency bands. Then, when the second transmission control unit determines that wireless communication using multiple frequency bands with the third communication device is not possible, it transmits data frames destined for the third communication device to the third communication device via a single frequency band. This prevents the second communication device from transmitting the same data frame destined for the third communication device, thereby preventing a decrease in throughput in data frame transmission even when the third communication device does not support wireless communication using multiple frequency bands over multiple communication paths.

1 is a diagram illustrating a configuration of a communication system according to an embodiment of the present invention. FIG. 1 is a diagram illustrating a hardware configuration of a communication system according to an embodiment. FIG. 1 is a diagram illustrating a functional configuration of a communication system according to an embodiment. FIG. 1A is a diagram showing an example of information stored in a specific sequence number storage unit relating to an embodiment, and FIG. 1B is a diagram showing an example of information stored in a redundancy availability information storage unit relating to an embodiment. FIG. 4 is a sequence diagram showing the operation of the communication system according to the embodiment. FIG. 2 is a diagram illustrating an example of a data frame according to an embodiment. FIG. 3 is a sequence diagram illustrating an operation of the communication system according to the embodiment. 1A is a schematic diagram illustrating the flow of data frames in a communication system according to an embodiment, and FIG. 1B is a diagram illustrating the operation of a base station in the communication system according to an embodiment. 10 is a flowchart illustrating an example of the flow of a communication control process executed by a base station according to the embodiment. FIG. 10 is a diagram illustrating a configuration of a communication system according to a modified example. FIG. 10 is a schematic diagram illustrating the flow of data frames in a communication system according to a modified example. FIG. 10 is a sequence diagram showing the operation of a communication system according to a modified example. FIG. 10 is a sequence diagram showing the operation of a communication system according to a modified example.

A communication system according to one embodiment of the present invention will be described in detail below with reference to the drawings. The communication system according to this embodiment includes a second communication device capable of wireless communication with a first communication device, and a third communication device different from the first communication device that is capable of wireless communication with the second communication device. The first communication device includes a multiband communication capability notification unit that generates a management frame including multiband communication capability notification information for notifying the second communication device that the first communication device is capable of wireless communication via multiple frequency bands, and a first transmission control unit that, after transmitting the multiband communication capability notification information, adds data frame identification information to a data frame addressed to the third communication device and transmits the data frame to the second communication device via each of the multiple frequency bands. The second communication device has a multiband communication feasibility determination unit that determines that wireless communication with the first communication device is possible over multiple frequency bands when a management frame transmitted from the first communication device includes multiband communication capability notification information; a frame acquisition unit that acquires data frames destined for the third communication device and transmitted from the first communication device over each of the multiple frequency bands when it is determined that wireless communication with the first communication device is possible over multiple frequency bands; and a second transmission control unit that transmits a data frame destined for the third communication device to the third communication device over one frequency band based on data frame identification information when it is unable to receive a management frame including the multiband communication capability notification information from the third communication device and the multiband communication feasibility determination unit determines that wireless communication with the third communication device is not possible over the multiple frequency bands. This embodiment is described in detail below.

As shown in FIG. 1, the communication system according to this embodiment includes two terminal devices 3A and 3B, a relay device 2, and a base station 1. Base station 1 is an access point used, for example, in a home network or an office wireless LAN, and communicates wirelessly with relay device 2 and terminal device 3B. Terminal device 3A is, for example, a general-purpose personal computer connected to relay device 2 via a wired communication network NW0. Relay device 2 is a first communication device that communicates wired with terminal device 3A and wirelessly with base station 1, relaying management frames and data frames transmitted and received between terminal device 3A and base station 1. Terminal device 3B is, for example, a general-purpose personal computer equipped with a wireless module, and functions as a second communication device capable of wireless communication with base station 1. In the following description of the embodiment of the present invention, it is assumed that wireless communication between base station 1 and relay device 2 is possible via multiple frequency bands, while terminal device 3B is unable to transmit and receive frames via multiple frequency bands and is therefore unable to communicate wirelessly with base station 1. Furthermore, relay device 2 and terminal device 3A are connected by wire, and naturally, frames are not transmitted or received over multiple frequency bands. As an alternative embodiment of the present invention, the communication system is not limited to that shown in FIG. 1, and a communication system in which terminal device 3A and relay device 2 are connected over a wireless communication network may also be used. In this case, the following explanation should be understood as an example in which terminal device 3A is unable to transmit or receive frames over multiple frequency bands.

The hardware configuration of the relay device 2 and the functions of the relay device 2 are described in detail below using Figures 2 to 4.

As shown in FIG. 2, the relay device 2 according to this embodiment is a first communication device that includes a CPU (Central Processing Unit) 201, a main memory 202, an auxiliary memory 203, two wireless modules 205A and 205B, a wired communication interface 206, and a bus 209 that connects the various components. The main memory 202 is made up of volatile memory such as RAM (Random Access Memory), and is used as a working area for the CPU 201. The auxiliary memory 203 is made up of non-volatile memory (for example, ROM (Read Only Memory), SSD (Solid State Drive), HDD (Hard Disk Drive), etc.), and stores programs for controlling the relay device 2.

Wireless modules 205A and 205B each communicate using a communication method conforming to a wireless LAN standard, such as IEEE 802.11. Wireless modules 205A and 205B each have an antenna (not shown), a receiving circuit (not shown), a signal processing unit (not shown), and a transmitting circuit (not shown). The receiving circuit receives a wireless signal via the antenna, demodulates the signal corresponding to the received wireless signal, generates a baseband signal, and outputs the baseband signal to the signal processing unit. The transmitting circuit generates a wireless signal corresponding to the frame to be transmitted by modulating a carrier signal using the baseband signal input from the signal processing unit, and transmits the generated wireless signal via the antenna. The signal processing unit, implemented, for example, by a DSP (Digital Signal Processor), generates a frame corresponding to the wireless signal received by the receiving circuit based on the baseband signal input from the receiving circuit and sends it to bus 209. The signal processing unit also generates a baseband signal based on various frames transferred from main memory unit 202 via bus 209 and outputs the baseband signal to the transmitting circuit. Furthermore, the wireless modules 205A and 205B use channels belonging to different frequency bands. For example, the wireless module 205A uses a channel belonging to the 2.4 GHz frequency band, and the wireless module 205B uses a channel belonging to the 5 GHz frequency band. Although the relay device 2 according to the present embodiment is described as including two wireless modules 205A and 205B that use channels belonging to different frequency bands, these wireless modules may be replaced with a wireless IC chip (or a single module including such a chip) capable of simultaneously and independently performing wireless communication on multiple channels belonging to different frequency bands. More specifically, for example, the wireless IC chip may be capable of independently performing wireless communication on a channel belonging to the 2.4 GHz frequency band and a channel belonging to the 5 GHz frequency band. When transmitting and receiving data frames using channels belonging to two frequency bands using the wireless IC chip, two MAC addresses are assigned in the MAC layer, thereby enabling wireless communication equivalent to the wireless modules 205A and 205B. This hardware configuration enables wireless communication over multiple frequency bands. An important example of this implementation is described below, where the same data frame is transmitted over multiple frequency bands for redundancy purposes, ensuring reliable wireless communication even in environments with unstable wireless conditions. Furthermore, for example, wireless module 205A and wireless module 205B can simultaneously achieve wireless communication over multiple frequency bands by using different channels (e.g., channel 36 in the W52 band and channel 100 in the W56 band) belonging to the same frequency band (e.g., the 5 GHz frequency band). However, depending on the frequency band used, considering factors such as a lack of available communication channels and regulatory restrictions (e.g., radar wave monitoring in the 5 GHz frequency band), it is more preferable to use the aforementioned channels belonging to multiple different frequency bands (e.g., channels belonging to the 2.4 GHz frequency band and channels belonging to the 5 GHz frequency band).

By loading the programs stored in the auxiliary memory unit 203 into the main memory unit 202 and executing them, the CPU 201 functions as a redundancy possibility notification unit 215, a frame acquisition unit 211, a type discrimination unit 212, a redundancy possibility determination unit 213, and a transmission control unit 214, as shown in FIG. 3. The auxiliary memory unit 203 shown in FIG. 2 also has a redundancy possibility information storage unit 231, as shown in FIG. 3. The main memory unit 202 shown in FIG. 2 also has a frame buffer 221 that temporarily stores data frames received by the wired communication interface 206 or wireless modules 205A and 205B, and a specific sequence number storage unit 222, as shown in FIG. 3.

Returning to Figure 3, the specific sequence number storage unit 222 stores data frame identification information that identifies a data frame and specific sequence number information in association with the MAC address information of the sender of the data frame, as shown in Figure 4(A), for example. Here, the specific sequence number information is information indicating a sequence number that is added in advance to recognize multiple redundant data frames (i.e., one or more identical multiple data frames). Note that the specific sequence number is different from the number information that indicates the order that is added at the application layer in TCP/IP communication, for example, and is used to rearrange data frames after reception.

The redundancy availability information storage unit 231 stores redundancy availability information indicating whether redundant wireless communication with the relay device 2 is possible, in association with the MAC address information of the sender of the data frame, as shown in FIG. 4(B), for example.

The redundancy capability notification unit 215 is a multi-band communication capability notification unit that generates a management frame including redundancy capability notification information to notify the base station 1 that the relay device 2 is capable of redundant wireless communication via multiple frequency bands. Specifically, the redundancy capability notification unit 215 generates, for example, a probe request frame including redundancy capability notification information. The redundancy capability notification unit 215 then notifies the transmission control unit 214 of the generated management frame. Examples of management frames include management frames and action frames defined by wireless communication standards (for example, the IEEE 802.11 communication standard) for exchanging various types of information between devices in wireless communication.

When the frame acquisition unit 211 acquires a data frame transmitted from the terminal device 3A via the wired communication interface 206, it stores the acquired data frame in the frame buffer 221. Furthermore, when the frame acquisition unit 211 acquires a management frame or a data frame transmitted from the base station 1 via the wireless modules 205A and 205B, it notifies the type determination unit 212 of the various frames it has acquired.

The type determination unit 212 determines the type of frame notified by the frame acquisition unit 211, i.e., whether the frame is a management frame for determining whether redundant wireless communication is possible for the frame's sender, or a data frame. If the type determination unit 212 determines that the frame notified by the frame acquisition unit 211 is the aforementioned management frame, it notifies the transmission control unit 214 and the redundancy availability determination unit 213 of the management frame. On the other hand, if the type determination unit 212 determines that the frame notified by the frame acquisition unit 211 is a data frame, it extracts specific sequence number information and source MAC address information from the data frame. The type determination unit 212 then stores the data frame in the frame buffer 221 and stores the extracted specific sequence number information in the specific sequence number storage unit 222, correlating it with the extracted MAC address information.

The redundancy feasibility determination unit 213 is a multi-band communication feasibility determination unit that, when notified of a management frame by the type determination unit 212, determines whether the management frame includes redundancy feasibility notification information. If the redundancy feasibility determination unit 213 determines that the management frame includes redundancy feasibility notification information, it stores redundancy feasibility information indicating that the sender of the management frame is capable of redundant wireless communication in the redundancy feasibility information storage unit 231, in association with the MAC address information of the sender of the management frame. On the other hand, if the redundancy feasibility determination unit 213 determines that the management frame does not include redundancy feasibility notification information (i.e., it cannot receive a management frame including multi-band communication feasibility notification information), it stores redundancy feasibility information indicating that the sender of the management frame is not capable of redundant wireless communication in the redundancy feasibility information storage unit 231, in association with the MAC address information of the sender of the management frame.

When initiating communication with base station 1, transmission control unit 214 transmits a management frame containing redundancy availability notification information notified by redundancy availability notification unit 215 to base station 1 via wireless module 205A or 205B. After transmitting the management frame containing the redundancy availability notification information, transmission control unit 214 generates a data frame by adding specific sequence number information identifying the data frame to the data frame stored in frame buffer 221 and destined for terminal device 3B. Transmission control unit 214 then transmits the generated data frame to base station 1 via channels belonging to two frequency bands, respectively, via two wireless modules 205A and 205B. Naturally, the data frames transmitted via the two channels are assigned the same sequence number. Preferably, the two frequency bands are, for example, the 2.4 GHz band and the 5 GHz band.

The transmission control unit 214 also determines whether the sequence number included in the data frame stored in the frame buffer 221 differs from the sequence number in the specific sequence number information associated with the data frame identification information of an already acquired data frame stored in the specific sequence number memory unit 222. Here, if the sequence number included in the data frame differs from the sequence number indicated by the sequence number information associated with the data frame identification information of an already acquired data frame stored in the specific sequence number memory unit 222, the transmission control unit 214 newly stores the specific sequence number information corresponding to the data frame identification information of the data frame stored in the specific sequence number memory unit 222. Thereafter, the transmission control unit 214 transmits the data frame stored in the frame buffer 221 to the terminal device 3A or base station 1 that is the destination of the data frame. Furthermore, if the sequence number included in a data frame stored in the frame buffer 221 is the same as the sequence number indicated by the specific sequence number information associated with the data frame identification information of an already acquired data frame stored in the specific sequence number storage unit 222, the transmission control unit 214 first references the redundancy availability information for the destination of the acquired data frame stored in the redundancy availability information storage unit 231 to determine whether redundancy in wireless communication with the destination of the data frame is possible. Here, if the transmission control unit 214 determines that redundancy in wireless communication with the destination of the data frame is possible, it transmits the data frame stored in the frame buffer 221 to the destination of the data frame (e.g., base station 1). On the other hand, if the transmission control unit 214 determines that redundancy in wireless communication with the destination of the data frame is not possible, it discards the data frame stored in the frame buffer 221.

Furthermore, when the transmission control unit 214 receives a beacon frame, which is a management frame, from the frame acquisition unit 211, and the SSID included in the beacon frame is the same as the SSID assigned to the local station, the transmission control unit 214 initiates a series of processes for wireless communication with the MAC address of the sender of the beacon frame. Furthermore, when the transmission control unit 214 receives an authentication request frame, which is a management frame, from the frame acquisition unit 211, the transmission control unit 214 generates an authentication response frame with the MAC address of the sender of the authentication request frame as the destination MAC address and forwards it to the wireless modules 205A and 205B. Here, the authentication request frame and authentication response frame are, for example, frames for performing open system authentication. Furthermore, when the transmission control unit 214 receives an association request frame, which is a management frame, from the frame acquisition unit 211, the transmission control unit 214 generates an association response frame with the MAC address of the sender of the association request frame as the destination MAC address and forwards it to the wireless modules 205A and 205B.

Next, the hardware configuration of base station 1 and the functions of base station 1 will be described in detail, also using Figures 2 to 4.

As shown in Figure 2, base station 1 is a second communication device that includes a CPU 101, a main memory unit 102, an auxiliary memory unit 103, two wireless modules 105A and 105B, and a bus 109 that connects the various units. The main memory unit 102 is composed of volatile memory such as RAM, and is used as a working area for CPU 101. The auxiliary memory unit 103 is composed of non-volatile memory, an SSD, an HDD, etc., and stores programs for controlling base station 1.

Wireless modules 105A and 105B each communicate using a communication method conforming to a wireless LAN standard, such as IEEE 802.11. Wireless modules 105A and 105B each have an antenna (not shown), a receiving circuit (not shown), a signal processing unit (not shown), and a transmitting circuit (not shown). The receiving circuit receives a wireless signal via the antenna, demodulates the signal corresponding to the received wireless signal, generates a baseband signal, and outputs the baseband signal to the signal processing unit. The transmitting circuit generates a wireless signal corresponding to the frame to be transmitted by modulating a carrier signal using the baseband signal input from the signal processing unit, and transmits the generated wireless signal via the antenna. The signal processing unit generates a frame corresponding to the wireless signal received by the receiving circuit based on the baseband signal input from the receiving circuit, and sends the frame to bus 109. Furthermore, the signal processing unit generates a baseband signal based on various frames transferred from main memory unit 102 via bus 109, and outputs the baseband signal to the transmitting circuit. The two wireless modules 105A and 105B use channels belonging to different frequency bands; for example, wireless module 105A uses a channel belonging to the 2.4 GHz frequency band, and wireless module 105B uses a channel belonging to the 5 GHz frequency band. Note that, in the base station 1 according to this embodiment, wireless modules 105A and 105B are described as using channels belonging to different frequency bands, but the wireless modules may also be configured, for example, with a wireless IC chip (or a single module equipped with such a chip) capable of performing wireless communication independently on multiple channels belonging to different frequency bands.

By loading and executing the program stored in the auxiliary memory unit 103 into the main memory unit 102, the CPU 101 functions as a frame acquisition unit 111, a type determination unit 112, a redundancy feasibility determination unit 113, a transmission control unit 114, and a redundancy feasibility notification unit 115, as shown in FIG. 3. The auxiliary memory unit 103 shown in FIG. 2 also has a redundancy feasibility information storage unit 131, as shown in FIG. 3. The main memory unit 102 shown in FIG. 2 also has a frame buffer 121, as shown in FIG. 3, that temporarily stores data frames received by the wireless modules 105A and 105B. The frame buffer 121 temporarily stores acquired data frames. The specific sequence number storage unit 122 is a data identification information storage unit that stores data frame identification information and specific sequence number information that identify data frames, in association with the MAC address information of the sender of the data frame, as shown in FIG. 4(A), for example. Here, in the source MAC address information shown in Figure 4(A), two pieces of source MAC address information are shown for relay device 2, which indicates that two different MAC addresses are assigned to the two wireless modules present in relay device 2. Specifically, as shown in Figure 2, MAC address "00:00:00:00:00:01" indicates the MAC address of wireless module 205A, and MAC address "00:00:00:00:00:02" indicates the MAC address of wireless module 205B.

As shown in FIG. 4(B), for example, the redundancy availability information storage unit 131 stores redundancy availability information indicating whether redundant wireless communication with the base station 1 is possible, in association with MAC address information indicating the MAC addresses assigned to the wireless modules 205A, 205B of the relay device 2, terminal device 3B, and the like that are capable of wireless communication with the base station 1. Specifically, this indicates that wireless modules 205A and 205B of the relay device 2 are capable of redundant wireless communication (F1 (possible)), while terminal device 3B is not capable of redundant wireless communication (F2 (not possible)).

Returning to FIG. 3, when the frame acquisition unit 111 acquires a management frame or a data frame transmitted from the relay device 2 or the terminal device 3B via the wireless modules 105A and 105B, it notifies the type determination unit 112 of the acquired frame. The type determination unit 112 determines the type of the frame notified by the frame acquisition unit 111, i.e., whether the frame is a management frame for determining whether redundant wireless communication is possible for the frame's sender, or a data frame. If the type determination unit 112 determines that the frame notified by the frame acquisition unit 111 is a management frame, it notifies the transmission control unit 114 and the redundancy availability determination unit 113 of the management frame. On the other hand, if the type determination unit 112 determines that the frame notified by the frame acquisition unit 111 is a data frame, it extracts the specific sequence number information included in the data frame and the MAC address information of the sender of the data frame. The type determination unit 112 then associates the data frame with the extracted combination of specific sequence number information and MAC address information and stores it in the specific sequence number storage unit 122.

The redundancy feasibility determination unit 113 is a multi-band communication feasibility determination unit that, when notified of a management frame by the type determination unit 112, determines whether the management frame contains redundancy feasibility notification information. If the redundancy feasibility determination unit 113 determines that the management frame contains redundancy feasibility notification information, it stores redundancy feasibility information indicating that the sender of the management frame is capable of redundant wireless communication in the redundancy feasibility information storage unit 131, in association with the MAC address information of the sender of the management frame. On the other hand, if the redundancy feasibility determination unit 113 determines that the management frame does not contain redundancy feasibility notification information (i.e., it cannot receive a management frame containing multi-band communication feasibility notification information), it stores redundancy feasibility information indicating that the sender of the management frame is not capable of redundant wireless communication in the redundancy feasibility information storage unit 131, in association with the MAC address information of the sender of the management frame.

When initiating communication with relay device 2, transmission control unit 114 transmits a management frame containing redundancy availability notification information notified by redundancy availability notification unit 115 to relay device 2 via wireless module 105A or 105B. After transmitting the management frame containing the redundancy availability notification information, transmission control unit 114 generates a data frame by adding specific sequence number information identifying the data frame to the data frame stored in frame buffer 121 and destined for terminal device 3B. Then, transmission control unit 114 transmits the generated data frame to relay device 2 via channels belonging to two frequency bands, respectively, using two wireless modules 105A and 105B.

The transmission control unit 114 also determines whether the sequence number included in the data frame stored in the frame buffer 121 differs from the sequence number in the specific sequence number information stored in the specific sequence number memory unit 122 and associated with the data frame identification information of an already acquired data frame. Here, if the sequence number included in the data frame differs from the sequence number indicated by the specific sequence number information stored in the specific sequence number memory unit 122 and associated with the data frame identification information of an already acquired data frame, the transmission control unit 114 newly stores the specific sequence number information stored in the specific sequence number memory unit 122 that corresponds to the data frame identification information of the data frame. The transmission control unit 114 then transmits the data frame stored in the frame buffer 121 to the terminal device 3B or relay device 2 that is the destination of the data frame. Furthermore, if the sequence number included in a data frame stored in frame buffer 121 is the same as the sequence number indicated by the specific sequence number information associated with the data frame identification information of an already acquired data frame stored in specific sequence number storage unit 122, the transmission control unit 114 references the redundancy availability information for the data frame's destination stored in redundancy availability information storage unit 131 to determine whether redundancy in wireless communication with the data frame's destination is possible. Here, if the transmission control unit 114 determines that redundancy in wireless communication with the data frame's destination is possible, it transmits the data frame stored in frame buffer 121 to the data frame's destination (e.g., relay device 2). On the other hand, if the transmission control unit 114 determines that redundancy in wireless communication with the data frame's destination is not possible, it discards the data frame stored in frame buffer 121.

Also, suppose that the transmission control unit 114 determines, for example, by referencing the redundancy availability information corresponding to terminal device 3B stored in the redundancy availability information storage unit 131, that terminal device 3B does not support redundant wireless communication. In this case, the transmission control unit 114 transmits to terminal device 3B the data frame that was acquired first of two data frames that contain the same specific sequence number information and have the MAC address of terminal device 3B as the destination MAC address, and discards the other data frame that was acquired later. Here, suppose that the transmission control unit 114 acquires a data frame from relay device 2 via a channel belonging to the 2.4 GHz frequency band, for example, and then acquires a data frame containing the same specific sequence number information via a channel belonging to the 5 GHz frequency band. In this case, the transmission control unit 114 discards the data frame acquired via the channel belonging to the 5 GHz frequency band.

Furthermore, when the transmission control unit 114 receives a probe request frame, which is a management frame, from the frame acquisition unit 111, and if the SSID included in the probe request frame is the same as the SSID assigned to the local station, the transmission control unit 114 generates a probe response frame with the MAC address of the sender of the probe request frame as the destination MAC address and forwards it to the wireless modules 105A and 105B. Furthermore, when the transmission control unit 114 receives an authentication request frame, which is a management frame, from the frame acquisition unit 111, the transmission control unit 114 generates an authentication response frame with the MAC address of the sender of the authentication request frame as the destination MAC address and forwards it to the wireless modules 105A and 105B. Here, the authentication request frame and authentication response frame are, for example, frames for performing open system authentication. Furthermore, when the frame acquisition unit 111 notifies the transmission control unit 114 of an association request frame, which is a management frame, the transmission control unit 114 generates an association response frame in response, with the MAC address of the sender of the association request frame as the destination MAC address, and transfers this frame to the wireless modules 105A and 105B.

The redundancy capability notification unit 115 is a multi-band communication capability notification unit that generates a management frame including redundancy capability notification information to notify the relay device 2 that the base station 1 is capable of redundant wireless communication via multiple frequency bands. Specifically, the redundancy capability notification unit 115 generates, for example, a beacon frame including the redundancy capability notification information and notifies the transmission control unit 114 of the generated management frame. Then, when starting communication with the relay device 2, the transmission control unit 114 transmits to the relay device 2 a management frame including the redundancy capability notification information notified by the redundancy capability notification unit 115. Examples of management frames include management frames and action frames defined by wireless communication standards (for example, the IEEE 802.11 communication standard) for exchanging various types of wireless communication information between devices.

Next, the operation of the communication system according to this embodiment will be described in detail with reference to Figures 5 to 7. Note that Figures 5 and 7 omit illustration of transmission and reception of ACK (ACKnowledgement) frames. Note that in the example shown in Figure 5, a data frame is first transmitted from terminal device 3A to terminal device 3B via relay device 2 and base station 1, and then (step S29 and subsequent steps) a data frame is transmitted from terminal device 3B to terminal device 3A via base station 1 and relay device 2. Also, in the example shown in Figure 5, base station 1 and relay device 2 are devices capable of redundant wireless communication, while terminal devices 3A and 3B are devices incapable of redundant wireless communication. First, as shown in Figure 5, when relay device 2 establishes a wireless connection with base station 1, it generates a probe request frame including redundancy capability notification information to notify base station 1 that the relay device 2 is capable of redundant wireless communication via multiple frequency bands (step S1). Next, the generated probe request frame is transmitted from relay device 2 to base station 1 (step S2). On the other hand, when the base station 1 receives the probe request frame, it transmits a probe response frame to the relay device 2 in response (step S3). If the redundancy capability notification information is included in the probe request frame received from the relay device 2, the base station 1 determines that redundant wireless communication with the relay device 2 is possible, i.e., that wireless communication redundancy is possible (step S4). The base station 1 then stores redundancy capability information indicating that wireless communication with the relay device 2 is possible in the redundancy capability information storage unit 131 in association with the MAC address information of the wireless modules 205A and 205B of the relay device 2 (step S5). Furthermore, when an authentication request frame is transmitted from the relay device 2 to the base station 1 (step S6), an authentication response frame is transmitted from the base station 1 to the relay device 2 in response (step S7). Next, when an association request frame is transmitted from the relay device 2 to the base station 1 (step S8), an association response frame is transmitted from the base station 1 to the relay device 2 in response (step S9). This enables data frames to be sent and received between the relay device 2 and the base station 1.

When terminal device 3B wirelessly connects to base station 1, terminal device 3B transmits a probe request frame that does not include the redundancy capability notification information described above to base station 1 (step S10). On the other hand, when base station 1 acquires the probe request frame, base station 1 transmits a probe response frame to terminal device 3B in response (step S11). Next, if the acquired probe request frame transmitted from terminal device 3B does not include redundancy capability notification information, base station 1 determines that wireless communication redundancy is not possible between terminal device 3B and base station 1 (step S12). Thereafter, base station 1 stores redundancy capability information indicating that wireless communication redundancy with terminal device 3B is not possible in the redundancy capability information storage unit 131, in association with the MAC address information of terminal device 3B (step S13). Furthermore, when terminal device 3B transmits an authentication request frame to base station 1 (step S14), base station 1 transmits an authentication response frame to terminal device 3B in response (step S15). Next, when an association request frame is transmitted from the terminal device 3B to the base station 1 (step S16), an association response frame is transmitted from the base station 1 to the terminal device 3B in response (step S17). This enables transmission and reception of data frames between the terminal device 3B and the base station 1. Although not shown in detail in FIG. 5 , when the base station 1 wirelessly connects to the relay device 2, the base station 1 also generates a beacon frame including redundancy feasibility notification information for notifying the relay device 2 that redundant wireless communication is possible via multiple frequency bands. The generated beacon frame is then transmitted from the base station 1 to the relay device 2. When the relay device 2 determines that the acquired beacon frame transmitted from the base station 1 includes the redundancy feasibility notification information and that redundant wireless communication with the base station 1 is possible, the relay device 2 stores redundancy feasibility information indicating that redundant wireless communication with the base station 1 is possible in the redundancy feasibility information storage unit 231 in association with the MAC address information of the wireless modules 105A and 105B of the base station 1. Thereafter, the aforementioned authentication request frame, authentication response frame, association request frame, and association response frame are transmitted and received between the relay device 2 and the base station 1. As a result, the relay device 2 and the base station 1 are in a state where their respective redundancy capability information storage units have stored information that indicates that they are devices capable of wireless communication redundancy.

Next, when a data frame is transmitted from terminal device 3A to relay device 2 via wired communication network NW0 (step S18), relay device 2 generates a data frame including the specific sequence number information by adding the specific sequence number information to the acquired data frame (step S19). This data frame has a structure in which the specific sequence number information is added to the beginning of the data included in the MAC payload, as shown in FIG. 6, for example. Returning to FIG. 5, the generated data frame is then transmitted from relay device 2 to base station 1 via channels belonging to the two different frequency bands mentioned above (step S20). For example, the data frame is transmitted from relay device 2 to base station 1 via channels belonging to the 2.4 GHz and 5 GHz frequency bands. Meanwhile, base station 1 determines that the previously acquired data frame includes the specific sequence number information (step S21), as shown in FIG. 7. Then, suppose that the base station 1 determines that the sequence number included in the data frame is different from all sequence numbers assigned to data frames acquired within the most recent preset period and stored in the specific sequence number storage unit 122 (i.e., all sequence numbers assigned to data frames that have already arrived) (step S22). In this case, the base station 1 newly stores the specific sequence number information included in the data frame in addition to the specific sequence number information corresponding to the data frame identification information of the data frame already stored in the specific sequence number storage unit 122 (step S23). Next, the data frame is transmitted from the base station 1 to the terminal device 3B (step S24). Immediately after the data frame of step S25, a data frame identical to the data frame transmitted in step S20 is transmitted from the relay device 2 to the base station 1 via a channel belonging to the other of the two frequency bands (step S25). For example, the data frame is transmitted from the relay device 2 to the base station 1 via a channel belonging to the 5 GHz frequency band. Meanwhile, suppose that the base station 1 determines that the acquired data frame includes specific sequence number information (step S26). The base station 1 then determines that the sequence number included in the acquired data frame is the same as the sequence number assigned to one of the data frames acquired within the most recent preset period stored in the specific sequence number storage unit 122 (i.e., the sequence number assigned to one of the data frames that have already arrived) (step S27). In this case, the base station 1 discards the data frame (step S28).

Also, suppose that a data frame addressed to terminal device 3A is transmitted from terminal device 3B to base station 1 (step S29). Then, suppose that base station 1 determines that the acquired data frame does not contain specific sequence number information (step S30). In this case, base station 1 generates a data frame that includes specific sequence number information by adding the specific sequence number information to the acquired data frame (step S31).

The generated data frame is then transmitted from base station 1 to relay device 2 via a channel belonging to one of two different frequency bands (step S32). Meanwhile, assume that relay device 2 determines that the sequence number included in the acquired data frame is different from all sequence numbers assigned to data frames acquired within the most recent preset period stored in the specific sequence number storage unit 222 (i.e., all sequence numbers assigned to data frames that have already arrived) (step S33). In this case, relay device 2 newly stores the specific sequence number information included in the data frame in the specific sequence number information stored in the specific sequence number storage unit 222 that corresponds to the data frame identification information of the data frame (step S34). Immediately after the data frame of step S25, the data frame is transmitted from relay device 2 to terminal device 3A via wired communication network NW0 (step S35).

Also, suppose that a data frame identical to the frame in step S32 is transmitted from base station 1 to relay device 2 via a channel belonging to the other of the two frequency bands (step S36). At this time, relay device 2 determines that the sequence number included in the acquired data frame is identical to the sequence number assigned to one of the data frames acquired within the most recent preset period stored in the specific sequence number storage unit 222 (i.e., the sequence number assigned to one of the data frames that have already arrived) (step S37). In this case, relay device 2 discards the acquired data frame (step S38). This is because relay device 2 and terminal device 3A are connected via a wired communication path, which does not support redundant communication.

In the communication system according to this embodiment, as shown in FIG. 8(A), when consecutive data frames DFA and DFB are transmitted from terminal device 3A to relay device 2, specific sequence number information is added by relay device 2. The same consecutive data frames DFA and DFB are then transmitted from relay device 2 to base station 1 via a channel belonging to the 2.4 GHz band and a channel belonging to the 5 GHz band. Since terminal device 3B is not capable of redundancy, base station 1 transmits only one of the identical consecutive data frames DFA and DFB acquired via each of the two channels to terminal device 3B and discards the other. In this case, base station 1 transmits only the consecutive data frames DFA and DFB that arrived at base station 1 first, out of the identical consecutive data frames DFA and DFB acquired via each of the two channels, to terminal device 3B and discards the other. For example, as shown in FIG. 8(B), assume that a data frame DFA acquired via a channel belonging to the 2.4 GHz band arrives at time T0, and a data frame DFA acquired via a channel belonging to the 5 GHz band arrives at base station 1 at time T1, which is later than time T0. In this case, the data frame DFA acquired via the channel belonging to the 2.4 GHz band is transmitted to terminal device 3B, and the data frame DFA acquired via the channel belonging to the 5 GHz band is discarded. Conversely, when transmitting a data frame DFB, if the data frame DFB acquired via the channel belonging to the 5 GHz band arrives at time T2, and the data frame DFB acquired via the channel belonging to the 2.4 GHz band arrives at base station 1 at time T3, which is later than time T2, the data frame DFB acquired via the channel belonging to the 5 GHz band is transmitted to terminal device 3B, and the data frame DFB acquired via the channel belonging to the 2.4 GHz band, which arrived later, is discarded.

Next, the communication control process executed by the base station 1 according to this embodiment will be described in detail with reference to FIG. 9. This communication control process is initiated, for example, when the base station 1 or relay device 2 is powered on. Note that FIG. 9 describes the communication control process executed by the base station 1, and omits the communication control process executed by the relay device 2. Also, the process by which the base station 1 acquires an authentication request frame and an association request frame, as well as the process by which the base station 1 transmits an ACK frame, an authentication response frame, and an association response frame, are not shown. Also, the process by which the base station 1 acquires management frames other than probe request frames, authentication request frames, and association request frames, as well as the process by which the base station 1 transmits management frames other than probe response frames, authentication response frames, and association response frames are not shown. These processes are executed separately from part of the communication control process shown in FIG. 9 (steps S103 to S117), as appropriate. As mentioned above, the probe request frame includes redundancy capability notification information.

First, the redundancy capability notification unit 115 determines whether a wireless connection event for establishing a wireless connection with the relay device 2 has occurred (step S101). Examples of wireless connection events include the completion of startup processing after powering on the base station 1, or reconnection after the wireless connection with the relay device 2 has been interrupted. If the redundancy capability notification unit 115 determines that the wireless connection event has not occurred (step S101: No), the processing of step S103 described below is executed. On the other hand, if the redundancy capability notification unit 111 determines that the wireless connection event has occurred (step S101: Yes), the redundancy capability notification unit 115 generates a probe request frame including redundancy capability notification information, and the transmission control unit 114 transmits the generated probe request frame to the relay device 2 (step S102). Then, once the frame acquisition unit 111 and transmission control unit 114 have completed sending and receiving the aforementioned probe response frame, authentication request frame, authentication response frame, association request frame, and association response frame with the relay device 2, the device is ready to send a data frame to the relay device 2.

Next, the frame acquisition unit 111 determines whether or not it has acquired a frame transmitted from the relay device 2 or the terminal device 3B (step S103). Here, the frame acquisition unit 111 repeatedly executes the process of step S103 unless it has acquired a frame (step S103: No). On the other hand, if the frame acquisition unit 111 determines that it has acquired a frame (step S103: Yes), it notifies the type determination unit 112 of the acquired frame. Next, the type determination unit 112 determines whether the frame notified by the frame acquisition unit 111 is a management frame for determining whether redundant wireless communication is possible for the frame's sender (step S104). Here, if the type determination unit 112 determines that the frame is the aforementioned management frame (step S104: Yes), it notifies the transmission control unit 114 and the redundancy feasibility determination unit 113 of the management frame.

Then, based on the management frame notified by the type discrimination unit 112, the redundancy determination unit 113 determines whether redundancy of wireless communication with the sender of the management frame is possible (step S105). Here, the redundancy determination unit 113 determines whether redundancy notification information is included in the management frame, and if it determines that redundancy notification information is included in the management frame, it determines that redundancy of wireless communication with the sender of the management frame is possible. Here, if the redundancy determination unit 113 determines that redundancy with the sender of the management frame is possible (step S105: Yes), it stores redundancy information indicating that redundancy of wireless communication with the sender of the management frame is possible in the redundancy information storage unit 131 in association with the MAC address information of the sender of the management frame (step S106). Next, the processing of step S103 is executed again. On the other hand, if the redundancy feasibility determination unit 113 determines that redundancy of wireless communication with the sender of the management frame is not possible (step S105: No), it stores redundancy feasibility information indicating that redundancy of wireless communication with the sender of the management frame is not possible in the redundancy feasibility information storage unit 131 in association with the MAC address information of the sender of the management frame (step S106). Then, the processing of step S103 is executed again.

Furthermore, if the type determination unit 112 determines in the aforementioned step S102 that the frame notified by the frame acquisition unit 111 is not the aforementioned management frame (step S104: No), it determines whether the frame is a data frame (step S108). Here, if the type determination unit 112 determines that the frame is not a data frame (step S108: No), the processing of step S103 is executed again. On the other hand, if the type determination unit 112 determines that the frame is a data frame (step S108: Yes), after storing the data frame in the frame buffer 121, the transmission control unit 114 determines whether the data frame stored in the frame buffer 121 includes specific sequence number information (step S109). For example, if the data frame was transmitted from terminal device 3B, it does not include specific sequence number information. If the transmission control unit 114 determines that the data frame stored in the frame buffer 121 does not contain specific sequence number information (step S109: No), it references the redundancy availability information for the data frame's destination stored in the redundancy availability information storage unit 131 to determine whether redundancy in wireless communication with the data frame's destination is possible (step S110). If the transmission control unit 114 determines that redundancy in wireless communication with the data frame's destination is not possible (step S110: No), it transmits the data frame to the destination as is (step S113). On the other hand, if the transmission control unit 114 determines that redundancy in wireless communication with the relay device 2, which is the destination of the data frame, is possible (step S110: Yes), it generates a data frame including the specific sequence number information by adding the specific sequence number information to the data frame (step S111). Next, the transmission control unit 114 transmits the generated data frame to the relay device 2 via a channel belonging to one of the two frequency bands (step S112). At the same time, the transmission control unit 114 transmits the same data frame to the base station 1 via a channel belonging to the other of the two frequency bands (step S113). Then, the processing of step S103 is executed again.

Let us also assume that the transmission control unit 114 determines in step S109 described above that the data frame stored in the frame buffer 121 contains specific sequence number information (step S109: Yes). In this case, the transmission control unit 114 determines whether the sequence number contained in the data frame stored in the frame buffer 121 is different from all of the sequence numbers assigned to any of the data frames acquired within the most recent preset period stored in the specific sequence number storage unit 122 (i.e., all of the sequence numbers assigned to data frames that have already arrived) (step S114). Here, let us assume that the transmission control unit 114 determines that the sequence number contained in the data frame is different from all of the sequence numbers assigned to data frames acquired within the most recent preset period stored in the specific sequence number storage unit 122 (i.e., all of the sequence numbers assigned to data frames that have already arrived) (step S114: Yes). In this case, the transmission control unit 114 newly stores the specific sequence number information stored in the specific sequence number storage unit 122, which corresponds to the data frame identification information of the data frame, as the specific sequence number information included in the data frame (step S115). Next, the transmission control unit 114 transmits the data frame stored in the frame buffer 121 to the terminal device 3B or relay device 2, which is the destination of the data frame (step S113). Then, the processing of step S103 is executed again.

On the other hand, the transmission control unit 114 determines that the sequence number included in the data frame stored in the frame buffer 121 is identical to one of the sequence numbers assigned to data frames acquired within the most recent preset period, stored in the specific sequence number storage unit 122 (step S114: No). In this case, the transmission control unit 114 references the redundancy availability information for the data frame's destination stored in the redundancy availability information storage unit 131 to determine whether redundancy in wireless communication with the data frame's destination is possible (step S116). Here, if the transmission control unit 114 determines that redundancy in wireless communication with the data frame's destination is possible (step S116: Yes), it transmits the data frame stored in the frame buffer 121 to the relay device 2 that is the destination of the data frame (step S113). However, the data frame is transmitted via a frequency band different from the frequency band used for the previous transmission. On the other hand, if the transmission control unit 114 determines that redundant wireless communication with the destination of the data frame is not possible (step S116: No), it discards the data frame stored in the frame buffer 121 (step S117). Then, the processing of step S103 is executed again.

As described above, in the base station 1 according to this embodiment, the redundancy feasibility determination unit 113 determines that redundant wireless communication with the relay device 2 is possible when redundancy feasibility notification information is included in the probe request frame transmitted from the relay device 2. The frame acquisition unit 111 also acquires data frames from the relay device 2, the destination of which is terminal device 3B, via channels belonging to each of the two frequency bands. When forwarding data frames to terminal device 3B, for which redundant wireless communication is not possible, the transmission control unit 114 transmits one data frame of multiple data frames containing the same specific sequence number information to terminal device 3B and discards the other data frames. This prevents the base station 1 from repeatedly transmitting the same data frame destined for terminal device 3B to terminal device 3B. This reduces the frequency band used for wireless communication between the base station 1 and terminal device 3B, thereby preventing a decrease in throughput in data frame transmission.

Note that the communication system according to this embodiment has been described primarily in terms of a case in which a data frame is transmitted from terminal device 3A to terminal device 3B via relay device 2 and base station 1. However, as shown in FIG. 3, for example, by including base station 1 as a redundancy availability notification unit 211 and relay device 2 as a type determination unit 112, redundancy availability determination unit 113, and redundancy availability information storage unit 131, the system can also be applied to a case in which a data frame is transmitted from terminal device 3B to terminal device 3A, for which redundant wireless communication is not possible, via base station 1 and relay device 2. This prevents duplicate transmission of the same data frame from relay device 2 to terminal device 3A. This reduces the frequency band used for wireless communication between relay device 2 and terminal device 3A, thereby preventing a decrease in throughput in data frame transmission. In other words, the communication system according to this embodiment is also effective when data frames are transmitted between terminal device 3A and terminal device 3B via base station 1 and relay device 2.

(Modification)
Although the embodiments of the present invention have been described above, the present invention is not limited to the configurations of the above-described embodiments. Next, a first variation of the embodiment of the present invention will be described in detail with reference to FIGS. 10 to 13. For example, as shown in FIG. 10, terminal devices 3A and 3B may communicate via two base stations 1 (1A and 1B). FIG. 10 is a diagram illustrating the configuration of a communication system according to the variation. In addition, in the communication system according to the variation shown in FIG. 10, the base stations 1A and 1B and the relay device 2 are devices capable of redundant wireless communication, and the terminal devices 3A and 3B are described as devices incapable of redundant wireless communication. FIG. 11 is a schematic diagram illustrating the flow of data frames in a communication system according to the variation. As shown in FIG. 11, when consecutive data frames DFA and DFB are transmitted from the terminal device 3A to the relay device 2, specific sequence number information is added in the relay device 2. Thereafter, the same consecutive data frames DFA and DFB are transmitted from the relay device 2 to the base station 1A via a channel belonging to the 2.4 GHz band and a channel belonging to the 5 GHz band, respectively. Meanwhile, the base station 1A transmits the same consecutive data frames DFA and DFB acquired via each of the two channels to the base station 1B via a channel belonging to the 2.4 GHz band and a channel belonging to the 5 GHz band, respectively.Then, the base station 1B transmits only one of the identical consecutive data frames DFA and DFB acquired via each of the two channels to the terminal device 3B, and discards the other.Here, of the identical data frames DFA and DFB acquired via each of the two channels, the base station 1B transmits only the consecutive data frames DFA and DFB that arrived at the base station 1 first to the terminal device 3B, and discards the other.

The operation of the communication system according to this modified example will now be described in detail with reference to Figures 12 and 13. Figures 12 and 13 are sequence diagrams showing the operation of the communication system according to the modified example. Figures 12 and 13 also show the operation of the communication system in chronological order within the same sequence. Note that in Figures 12 and 13, the same processes as those shown in Figures 5 and 7 are denoted by the same reference numerals. Also, in Figures 12 and 13, as in Figures 5 and 7, the transmission and reception of ACK frames are not shown.

As shown in FIG. 12, when a data frame is transmitted from terminal device 3A to relay device 2 (step S18), relay device 2 adds specific sequence number information to the acquired data frame (step S19). Then, the data frame including the specific sequence number information is transmitted from relay device 2 to base station 1A (step S20). Meanwhile, suppose base station 1A determines that the acquired data frame includes specific sequence number information (step S2001). Then, suppose base station 1A determines that the sequence number included in the data frame differs from the sequence number indicated by the specific sequence number information stored in the specific sequence number storage unit 122 (step S2002). In this case, base station 1A newly stores the specific sequence number information corresponding to the data frame identification information of the data frame stored in the specific sequence number storage unit 122 in the specific sequence number information included in the data frame (step S2003). Next, the data frame is transmitted from base station 1A to base station 1B (step S2004). Meanwhile, base station 1B determines that the acquired data frame contains specific sequence number information (step S21) and that the sequence number contained in the data frame differs from the sequence number indicated by the specific sequence number information stored in specific sequence number storage unit 122 (step S22). In this case, base station 1B newly stores the specific sequence number information corresponding to the data frame identification information of the data frame stored in specific sequence number storage unit 122 as the specific sequence number information contained in the data frame (step S23). Next, the data frame is transmitted from base station 1B to terminal device 3B (step S24).

For redundancy, the same data frame as that transmitted in step S20 is transmitted from relay device 2 to base station 1A via a channel with a different frequency band than that transmitted in step S20 (step S25). Meanwhile, base station 1A determines that the acquired data frame contains specific sequence number information (step S2005) and determines that the sequence number contained in the data frame is the same as the sequence number indicated by the specific sequence number information stored in the specific sequence number memory unit 122 (step S2006). In this case, as shown in FIG. 12, base station 1A does not newly store the specific sequence number information stored in the specific sequence number memory unit 122. Then, moving to FIG. 13, the data frame is transmitted from base station 1A to base station 1B via a channel with a different frequency band than that transmitted in step 2004 (step S2007). Meanwhile, base station 1B determines that the acquired data frame contains specific sequence number information (step S26) and that the sequence number contained in the data frame is the same as the sequence number indicated by the specific sequence number information stored in the specific sequence number storage unit 122 (step S27). In this case, base station 1B discards the data frame, taking into account that the destination terminal device 3B is not capable of redundant wireless communication (step S28).

This configuration allows data frames to be sent and received between terminal devices 3A and 3B via multiple base stations 1A and 1B, making it possible to exchange data even when terminal devices 3A and 3B are separated by a relatively long distance.

In the embodiment, an example in which one relay device 2 is provided has been described, but this is not limiting, and it may also be possible to provide, for example, multiple relay devices 2 capable of communicating with the base station 1.

In addition, in the modified embodiment, an example was described in which two base stations 1 were provided, but this is not limiting. The communication system may also include, for example, multiple base stations 1 that can communicate with base station 1. Specifically, the system may include multiple base stations (with access point functions and station functions), and be configured as a wireless mesh network in which adjacent base stations are connected to each other via wireless communication.

In the embodiment, an example has been described in which the relay device 2 includes redundancy capability notification information in a probe request frame and transmits it to the base station 1, but the management frame that includes the redundancy capability notification information is not limited to a probe request frame. For example, the relay device 2 may generate a management frame other than a probe request frame that includes redundancy capability notification information and transmit it to the base station 1. Examples of such management frames include management frames and action frames defined by wireless communication standards (e.g., the IEEE 802.11 communication standard) for exchanging various types of information between devices in wireless communication.

In the embodiment, an example has been described in which data frames are transmitted and received between the base station 1 and the relay device 2 via channels belonging to two frequency bands. However, this is not limited to this, and data frames may be transmitted and received between the base station 1 and the relay device 2 via channels belonging to three or more frequency bands (for example, the 2.4 GHz, 5 GHz, and 6 GHz frequency bands). Furthermore, in the embodiment, an example has been described in which data frames are transmitted and received between the base station 1 and the relay device 2 via channels belonging to the 2.4 GHz frequency band and the 5 GHz frequency band. However, the frequency bands used are not limited to these, and two frequency bands selected from the 2.4 GHz frequency band, the 5 GHz frequency band, and the 6 GHz frequency band may be used, for example.

The various functions of the relay device 2 and base station 1 according to the present invention can be realized using a computer system equipped with a wireless communication module, rather than a dedicated system. For example, a program for executing the above operations can be stored on a non-transitory recording medium (such as a CD-ROM) that can be read by the computer system and distributed to a computer connected to the network. The relay device 2 and base station 1 that perform the above-described processing can then be configured by installing the program on the computer system.

Furthermore, the method for providing the program to the computer is arbitrary. For example, the program may be uploaded to a server on a communication line and distributed to the computer via the communication line. The computer then launches the program and executes it under the control of the OS in the same way as other applications. In this way, the computer functions as a relay device 2 and base station 1 that executes the above-mentioned processing.

The above describes embodiments and variations of the present invention, but the present invention is not limited to these. The present invention also includes appropriate combinations of the embodiments and variations, as well as appropriate modifications thereto.

The present invention is suitable for use as a base station with dual-band simultaneous connection functionality.

1, 1A, 1B: Base Station, 2: Relay Device, 3A, 3B: Terminal Device, 101, 201: CPU, 102, 202: Main Memory, 103, 203: Auxiliary Memory, 105A, 105B, 205A, 205B: Wireless Module, 109, 209: Bus, 111, 211: Frame Acquisition Unit, 112, 212: Type Identification Unit, 113, 213: Redundancy Availability Determination Unit, 114, 214: Transmission Control Unit, 115, 215: Redundancy Availability Notification Unit, 121, 221: Frame Buffer, 122, 222: Specific Sequence Number Storage Unit, 131, 231: Redundancy Availability Information Storage Unit, 206: Wired Communication Interface, NW0: Wired Communication Network

Claims (7)

A communication system including a first communication device, a second communication device capable of wireless communication with the first communication device, and a third communication device different from the first communication device capable of wireless communication with the second communication device,
The first communication device
a multiband communication capability notification unit that generates a management frame including multiband communication capability notification information for notifying the second communication device that the first communication device is capable of wireless communication via a plurality of frequency bands;
a first transmission control unit that, after transmitting the multiband communication capability notification information, adds data frame identification information to a data frame destined for the third communication device and transmits the data frame to the second communication device via each of the plurality of frequency bands;
the second communication device,
a multiband communication feasibility determination unit that determines that wireless communication between the first communication device and the first communication device is possible via the multiple frequency bands when the management frame transmitted from the first communication device includes the multiband communication capability notification information;
a frame acquisition unit that acquires, when it is determined that wireless communication with the first communication device is possible via the plurality of frequency bands, the data frames destined for the third communication device and transmitted from the first communication device via each of the plurality of frequency bands;
a second transmission control unit that, when a management frame including multiband communication capability notification information cannot be received from the third communication device and the multiband communication capability determination unit determines that wireless communication with the third communication device via the plurality of frequency bands is not possible, transmits the data frame addressed to the third communication device via one frequency band based on the data frame identification information.
Communication system. the multiple band communication feasibility determination unit generates a management frame including redundancy capability notification information for notifying the second communication device that redundant wireless communication via the multiple frequency bands is possible for the first communication device,
after transmitting the redundancy enablement notification information, the first transmission control unit generates the data frame including data identification information whose destination is the second communication device, and transmits the data frame to the second communication device via each of the plurality of frequency bands;
the multiband communication feasibility determination unit determines that the redundant wireless communication with the first communication device is possible when the redundancy feasibility notification information is included in the management frame transmitted from the first communication device,
when it is determined that the redundant wireless communication with the first communication device is possible, the frame acquisition unit acquires the data frames destined for the third communication device and transmitted from the first communication device via each of the plurality of frequency bands,
the second transmission control unit transmits one of the plurality of data frames, which include the same data identification information and are destined for the third communication device, to the third communication device, and discards the other data frames.
The communication system of claim 1 . the second transmission control unit transmits to the third communication device one of the data frames that includes the same data identification information and has the third communication device as a destination, the first acquired data frame, and discards the other data frames.
The communication system according to claim 2 . the second communication device further includes a data identification information storage unit that stores the data identification information in association with data frame identification information that identifies the data frame;
The second transmission control unit
(a) if the data identification information stored in the data identification information storage unit and corresponding to the data frame identification information of the acquired data frame differs from the data identification information included in the acquired data frame, updating the data identification information stored in the data identification information storage unit to the data identification information included in the acquired data frame, and then transmitting the data frame to the third communication device;
(b) discarding the acquired data frame when the data identification information stored in the data identification information storage unit and corresponding to the data frame identification information of the acquired data frame is identical to the data identification information included in the acquired data frame and the redundant wireless communication with the third communication device is not possible.
The communication system according to claim 3 . A communication device capable of wireless communication with another first communication device via a plurality of frequency bands, and capable of wireless communication with another second communication device different from the other first communication device,
a multiband communication feasibility determination unit that determines that wireless communication is possible between the other first communication device and the other first communication device via a plurality of frequency bands when multiband communication feasibility notification information that notifies that wireless communication is possible via the plurality of frequency bands is included in a management frame transmitted from the other first communication device;
a frame acquisition unit that acquires, when it is determined that wireless communication with the other first communication device via the plurality of frequency bands is possible, data frames that are transmitted from the other first communication device via each of the plurality of frequency bands and have data frame identification information assigned thereto and that are destined for the other second communication device;
a transmission control unit that, when a management frame including multiband communication capability notification information cannot be received from the other second communication device and the multiband communication capability determination unit determines that wireless communication with the other second communication device via the multiple frequency bands is not possible, transmits the data frame having the other second communication device as a destination to the other second communication device via one frequency band based on the data frame identification information.
Communication equipment. A communication method using a first communication device, a second communication device capable of wireless communication with the first communication device via a plurality of frequency bands, and a third communication device different from the first communication device capable of wireless communication with the second communication device via one frequency band,
generating, by the first communication device, a management frame including multi-band communication capability notification information for notifying the second communication device that the first communication device is capable of wireless communication via the multiple frequency bands;
a step in which, after the first communication device transmits the multiband communication capability notification information, the first communication device generates a data frame having data frame identification information assigned thereto and having the third communication device as a destination, and transmits the data frame to the second communication device via each of the plurality of frequency bands;
a step of determining, by the second communication device, that wireless communication via the plurality of frequency bands with the first communication device is possible when the management frame transmitted from the first communication device includes the plurality of band communication possible notification information;
When it is determined that wireless communication between the second communication device and the first communication device is possible via the plurality of frequency bands, the second communication device acquires the data frames destined for the third communication device and transmitted from the first communication device via each of the plurality of frequency bands;
and when the second communication device is unable to receive a management frame including multi-band communication capability notification information from the third communication device and determines that wireless communication with the third communication device via the plurality of frequency bands is not possible, transmitting the data frame addressed to the third communication device via one frequency band based on the data frame identification information.
Communication method. Computer,
a multiband communication feasibility determination unit that determines that wireless communication is possible between the first communication device and another first communication device via a plurality of frequency bands when a management frame transmitted from the first communication device includes multiband communication feasibility notification information that notifies that wireless communication is possible via the plurality of frequency bands;
a frame acquisition unit that acquires, when it is determined that wireless communication with the other first communication device is possible via the plurality of frequency bands, data frames transmitted from the other first communication device via each of the plurality of frequency bands, the data frames including data frame identification information whose destination is a second communication device different from the other first communication device;
a transmission control unit that, when it is determined that a management frame including multi-band communication capability notification information cannot be received from the other second communication device and wireless communication with the other second communication device via the plurality of frequency bands is not possible, transmits the data frame having the other second communication device as a destination to the other second communication device via one frequency band based on the data frame identification information;
A program that functions as a