Communication system, base station, communication method, and program

Abstract

To provide a communication system, a base station, a communication method, and a program that can maintain a high level of communication quality by dynamically changing a connection configuration in accordance with the environment.SOLUTION: An access point 1 includes a hop number updating unit 117 that updates a hop number as its own station's hop number, a transmission control unit 116 that transmits a beacon frame including the updated own station's hop number to an access point 2 of a root or an access point 1 of another repeater, an RSSI calculation unit 111 that calculates the RSSI value of a wireless frame, a connection destination list memory unit 131 that stores the hop number and the RSSI value in association with the SSID of the access point 1 or 2 that is the transmission source of the beacon frame, and a connection destination selection unit 115 that selects a connection destination to be wirelessly connected to the access point 1 of the repeater from among the other access points 1 and 2 based on the RSSI value and the hop number.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a communication system, a base station, a communication method, and a program. [Background technology]

[0002] 2. Description of the Related Art A communication system has been proposed that includes a plurality of base stations each having a WDS (Wireless Distribution System) repeat function and configures a tree-type network (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-47333 A Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, in the communication system described in Patent Document 1, a static communication path may be set for each of a plurality of base stations. In this case, even if the quality of communication in a part of the already set communication path deteriorates due to, for example, the movement of a base station, or the quality of communication between at least one of the plurality of base stations deteriorates, the communication path cannot be changed, and communication may be forced to be performed in a degraded quality state.

[0005] The present invention has been made in consideration of the above, and aims to provide a communication system, base station, communication method, and program that can maintain a high level of communication quality by dynamically changing the connection configuration to suit the environment. [Means for solving the problem]

[0006] In order to achieve the above object, a communication system according to the present invention comprises: A communication system comprising a root base station and a plurality of repeater base stations, The repeater base station comprises: a hop number extraction unit that, when acquiring a beacon frame transmitted from a base station of the route or another base station of the repeater, extracts hop number information indicating a number of hops that reflects the number of base stations of the repeater via which the beacon frame is transmitted from the base station of the route to the base station of the route or another base station of the repeater that transmitted the beacon frame; a hop count update unit that increments the extracted hop count by 1 and updates it as the hop count of the local station, except when the extracted hop count is greater than the hop count of the local station; a transmission control unit that broadcasts a beacon frame including the updated hop count of the own station; a radio wave intensity calculation unit that calculates radio wave intensity of a radio frame arriving from a base station of the route or a base station of another repeater; a connection destination list storage unit that stores the number of hops and the radio wave intensity extracted from the beacon frame in association with an identifier of a base station that is a source of the beacon frame; The device has a connection destination selection unit that selects a connection destination for wirelessly connecting to the repeater's base station from a base station on the route or a base station of another repeater based on the calculated radio wave strength and the hop count indicated by the extracted hop count information. The number of hops referred to in this specification and claims is 0 for a root base station, and for a repeater base station, it means the number of repeater base stations (including the repeater base station) that exist on the path between the root base station and the repeater base station.

[0007] A base station according to another aspect of the present invention comprises: a radio wave intensity calculation unit that calculates radio wave intensity of a radio frame arriving from at least one other base station; a hop number extraction unit that, when receiving a beacon frame transmitted from another base station, extracts hop number information indicating a hop number reflecting the number of other base stations through which the beacon frame has been passed on the way to the own base station; a hop number update unit that, when receiving a beacon frame transmitted from another base station, increments the extracted hop number by 1 and updates it as the hop number of the own station, except when the extracted hop number is greater than the hop number of the own station; a transmission control unit that broadcasts a beacon frame including the updated hop count of the own station; The wireless communication device includes a connection destination selection unit that selects a connection destination for wirelessly connecting to the wireless communication device from among the other base stations based on the calculated radio wave strength and the hop number indicated by the extracted hop number information.

[0008] A communication method according to another aspect of the present invention comprises: A communication method in a communication system including a root base station and a repeater base station, comprising: When the repeater base station receives a beacon frame transmitted from the base station of the route or another base station of the repeater, extracting hop number information indicating the number of hops passed from the base station of the route to the base station of the route or another base station of the repeater that transmitted the beacon frame; incrementing the extracted hop count by 1 and updating it as the hop count of the local station, except when the extracted hop count is greater than the hop count of the local station; broadcasting a beacon frame including the updated hop count of the own station; calculating radio wave intensity of a radio frame arriving from a base station on the route or a base station of another repeater; storing the number of hops and the radio wave intensity extracted from the beacon frame in association with an identifier of a base station that is a source of the beacon frame; The method includes a step of selecting a connection destination for wirelessly connecting to the repeater's base station from among the base stations of the route or base stations of other repeaters based on the calculated radio wave strength and the hop number indicated by the extracted hop number information.

[0009] From another aspect, the program according to the present invention is Computer, a radio wave intensity calculation unit that calculates radio wave intensity of a wireless frame arriving from at least one other base station; a hop number extraction unit that, when receiving a beacon frame transmitted from another base station, extracts hop number information indicating a hop number reflecting the number of other base stations through which the beacon frame has been passed on the way to the own base station; a connection destination selection unit that selects a connection destination to be wirelessly connected to the own station from among the other base stations based on the calculated radio wave intensity and the hop number indicated by the extracted hop number information; a hop number update unit that, when acquiring a beacon frame transmitted from another base station, increments the extracted hop number by 1 and updates it as the hop number of the own station, except when the extracted hop number is larger than the hop number of the own station; a transmission control unit that broadcasts a beacon frame including the updated hop count of the own station; Function as. Effect of the Invention

[0010] According to the present invention, the radio wave strength calculation unit calculates the radio wave strength of a wireless frame arriving from at least one other repeater base station that can communicate with the repeater base station, and the hop number extraction unit extracts hop number information included in the acquired beacon frame when it acquires a beacon frame transmitted from the other repeater base station.Then, the connection destination selection unit preferentially selects another repeater base station or a route base station with a high calculated radio wave strength and a low hop number indicated by the extracted hop number information as a connection destination for wireless connection.Therefore, the other repeater base station or the route base station with a high radio wave strength and a low hop number arriving at the repeater base station is preferentially selected, so that the quality of communication between the repeater base station and the other repeater base station or the route base station can be maintained at a high level. [Brief description of the drawings]

[0011] [Figure 1] 1 is a diagram showing a configuration of a communication system according to an embodiment of the present invention; [Diagram 2] FIG. 2 is a diagram illustrating a hardware configuration of a communication system according to an embodiment. [Diagram 3] FIG. 2 is a diagram illustrating a functional configuration of a communication system according to an embodiment. [Figure 4] 11 is a diagram illustrating an example of information stored in a connection destination list storage unit according to the embodiment. FIG. [Diagram 5] FIG. 4 is a sequence diagram showing an operation of the communication system according to the embodiment. [Figure 6] FIG. 4 is a sequence diagram showing an operation of the communication system according to the embodiment. [Figure 7] FIG. 2A is a schematic diagram showing a communication path of a communication system according to an embodiment, and FIG. 2B is a schematic diagram showing another communication path of a communication system according to an embodiment. [Figure 8] FIG. 4 is a sequence diagram showing an operation of the communication system according to the embodiment. [Figure 9] 10 is a flowchart showing an example of the flow of a relay process executed by the access point according to the embodiment. [Figure 10] 10 is a flowchart showing an example of the flow of a relay process executed by the access point according to the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] A communication system according to an embodiment of the present invention will be described in detail below with reference to the drawings. The communication system according to this embodiment is a communication system including a root base station and a plurality of repeater base stations, and when the repeater base station receives a beacon frame transmitted from the root base station or another repeater base station, the repeater base station includes a hop number extracting unit that extracts hop number information indicating the number of hops passed from the root base station to the root base station or another repeater base station that transmitted the beacon frame, and a hop number extracting unit that increments the extracted hop number by 1 and updates it as the hop number of the own station, except when the extracted hop number is larger than the hop number of the own station. The present embodiment has a hop count update unit, a transmission control unit that broadcasts a beacon frame including the updated hop count of the own station, a radio wave strength calculation unit that calculates the radio wave strength of a wireless frame arriving from a base station of a root or a base station of another repeater, a connection destination list storage unit that associates the hop count and radio wave strength extracted from the beacon frame with an identifier of the base station that transmitted the beacon frame and stores them, and a connection destination selection unit that selects a connection destination for wirelessly connecting to the repeater base station from among the base stations of the root or other repeaters based on the calculated radio wave strength and the hop count indicated by the extracted hop count information. Hereinafter, the present embodiment will be described in detail.

[0013] As shown in FIG. 1, the communication system according to the present embodiment includes an access point 2 (corresponding to the "root base station" in the claims) which is a parent device (root), and a plurality of (five in FIG. 1) access points 1 (1A, 1B, 1C, 1D, 1E: corresponding to the "repeater base stations" in the claims) which operate as repeaters, i.e., relay data frames as they are. The root base station and the repeater base stations are also collectively referred to simply as base stations. The access points 1 and 2 are base stations having a WDS (Wireless Distribution System) repeat function, which is adopted, for example, as a home network or an office wireless LAN. The access point 2 and the plurality of access points 1A, 1B, 1C, 1D, 1E are identified by different BSSIDs (Basic Service Set Identifiers). Usually, these BSSIDs refer to the MAC addresses of the access point 2 and the access point 1, respectively. As shown in Fig. 1, the communication system according to the present embodiment shows a situation in which the root access point 2 performs WDS communication with the repeater access point 1A, while also performing WDS communication with the repeater access points 1B, 1C, 1D, and 1E. That is, in Fig. 1, the root access point 2 has two communication paths and performs WDS communication. Note that the WDS communication configured by the access point 2 and the access point 1 uses the same ESSID (Extended SSID).

[0014] 2, the root access point 2 according to this embodiment includes a CPU (Central Processing Unit) 201, a main memory unit 202, an auxiliary memory unit 203, a wireless module 205, and a bus 209 connecting each unit. The main memory unit 202 is composed of a volatile memory such as a RAM (Random Access Memory), and is used as a working area for the CPU 201. The auxiliary memory unit 203 is composed of a non-volatile memory such as a ROM (Read Only Memory), an SSD (Solid State Drive), an HDD (Hard Disk Drive), or the like, and stores a program for controlling the access point 2.

[0015] The wireless module 205 communicates in a communication method conforming to the wireless LAN standard conforming to, for example, IEEE802.11. Each of the wireless modules 205 has 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 an antenna, demodulates the received wireless signal to generate a baseband signal, and outputs the baseband signal to the signal processing unit. The transmitting circuit generates a wireless signal corresponding to a frame to be transmitted by modulating a carrier signal using a baseband signal input from the signal processing unit, and transmits the generated wireless signal via the antenna. The signal processing unit is realized by, for example, a DSP (Digital Signal Processor), and 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 the bus 209. In addition, the signal processing unit generates a baseband signal based on various frames transferred from the main memory unit 202 via the bus 209, and outputs the baseband signal to the transmitting circuit. In addition, the wireless module 205 wirelessly communicates with the access point 1 using a channel belonging to, for example, a 5 GHz frequency band.

[0016] CPU 201 loads a program stored in auxiliary storage unit 203 into main storage unit 202 and executes it, thereby functioning as frame acquisition unit 212, connection management unit 215, and transmission control unit 216, as shown in Fig. 3. Main storage unit 202 shown in Fig. 2 also has frame buffer 221 that temporarily stores data frames received by wireless module 205, as shown in Fig. 3.

[0017] The frame acquisition unit 212 acquires wireless frames transmitted from the access point 1. Specifically, when the frame acquisition unit 212 acquires a management frame, that is, a beacon frame, an authentication request frame, or an association request frame, via the wireless module 205, the frame acquisition unit 212 notifies the connection management unit 215 of the acquired management frame. In addition, when the frame acquisition unit 212 acquires a data frame transmitted from the access point 1 via the wireless module 205, the frame acquisition unit 212 stores the acquired data frame in the frame buffer 221.

[0018] When the connection management unit 215 is notified of an authentication request frame from the frame acquisition unit 212, it executes an authentication process, and when the authentication is successful, it notifies the transmission control unit 216 of an authentication response frame whose destination is the source of the authentication request frame. Also, when the connection management unit 215 is notified of an association request frame from the frame acquisition unit 212, it notifies the transmission control unit 216 of an association response frame whose destination is the source of the association request frame in response to this. Furthermore, the connection management unit 215 periodically generates a beacon frame including hop number information indicating the number of hops, and notifies the transmission control unit 216 of the generated beacon frame. The number of hops referred to here indicates the number of access points 1 (including the own device) via which communication is to be performed from the access point 2 of the route to the access point 1 of the repeater (i.e. the own device) with which communication is to be performed.

[0019] When the transmission control unit 216 is notified of a beacon frame by the connection management unit 215, the transmission control unit 216 broadcasts the notified beacon frame via the wireless module 205. Furthermore, when the transmission control unit 216 is notified of an authentication response frame or an association response frame by the connection management unit 215, the transmission control unit 216 transmits the notified authentication response frame or association response frame to the access point 1.

[0020] 2, the repeater access point 1 has the same hardware configuration as the access point 2, and includes a CPU 101, a main memory unit 102, an auxiliary memory unit 103, a wireless module 105, a clock unit 108, and a bus 109 that connects the various units. The main memory unit 102 is made up of a volatile memory, and the auxiliary memory unit 103 is made up of a non-volatile memory, and stores a program for controlling the access point 1.

[0021] The wireless module 105, like the wireless module 205 described above, communicates in a communication method conforming to the wireless LAN standard, for example, IEEE802.11. Like the wireless module 205, the wireless module 105 wirelessly communicates with the access point 2 or other access points 1 using a channel belonging to the 5 GHz frequency band. The timing unit 108 has a timer that is reset repeatedly every predetermined period of time (hereinafter also referred to as a destination update period, for example, 30 seconds) after the power is turned on and a wireless connection with the access point 2 or other access point 1 is completed (i.e., when WDS communication is established) in order to determine the arrival of a destination update period, which will be described later. The destination update period is determined by the user, for example, using an initial setting tool (not shown) before the operation of the access point.

[0022] The CPU 101 loads a program stored in the auxiliary storage unit 103 into the main storage unit 102 and executes it, thereby functioning as an RSSI (Received Signal Strength Indicator) calculation unit 111, a frame acquisition unit 112, a hop count extraction unit 114, a connection destination selection unit 115, a transmission control unit 116, a hop count update unit 117, and a connection management unit 118, as shown in FIG. 3. The auxiliary storage unit 103 shown in FIG. 2 also has a connection destination list storage unit 131, as shown in FIG. 3. The main storage unit 102 shown in FIG. 2 also has a frame buffer 121 that temporarily stores a data frame received by the wireless module 105, as shown in FIG. 3. The connection destination list storage unit 131 stores RSSI information indicating RSSI values ​​corresponding to each of the connection destination candidate access points 1 and 2, and hop count information indicating the number of hops, in association with connection destination SSID information indicating the SSID that identifies the corresponding access points 1 and 2, as shown in FIG. 4, for example. FIG. 4 shows an example of information stored in remote access list storage unit 131 of access point 1E, where BSSID[0] indicates the BSSID of access point 1A, and BSSID[1] indicates the BSSID of access point 1D.

[0023] Returning to FIG. 3, the RSSI calculation unit 111 is a radio wave intensity calculation unit that calculates an RSSI value stored in a wireless frame arriving at the wireless module 105 from each of other nodes (other access points 1 or access point 2) that can communicate with the access point 1 (own device). The RSSI calculation unit 111 stores the calculated RSSI value in the connection destination list storage unit 131 in association with the SSID information of the corresponding access points 1 and 2. The frame acquisition unit 112 acquires a management frame transmitted from the access point 2 or another access point 1, that is, a beacon frame, an authentication response frame, or an association response frame. When the frame acquisition unit 112 acquires a beacon frame transmitted from the access point 2 or another access point 1 via the wireless module 105, the frame acquisition unit 112 notifies the connection management unit 118, the hop number extraction unit 114, and the hop number update unit 117 of the acquired beacon frame. Here, the frame acquisition unit 112 acquires beacon frames periodically transmitted from the receivable access point 2 and other access points 1 at each preset connection destination update period. In addition, when the frame acquisition unit 112 acquires an authentication response frame or an association response frame transmitted from the access point 2 or another access point 1 via the wireless module 105, it notifies the connection management unit 118 of the acquired authentication response frame or association response frame.

[0024] When the hop number extraction unit 114 is notified of a beacon frame from the frame acquisition unit 112, the hop number extraction unit 114 extracts hop number information included in the notified beacon frame and SSID information of the access point 1 or 2 that is the transmission source of the beacon frame, and stores the extracted hop number information in the connection destination list storage unit 131 in association with the SSID information of the access point. In addition, the hop number extraction unit 114 notifies the extracted hop number information to the hop number update unit 117. When the hop number information is notified from the hop number extraction unit 114, the hop number update unit 117 updates the value of the hop number corresponding to each connection destination BSSID held by the own device in the connection destination list storage unit 131 to a value obtained by incrementing the number of hops indicated by the notified hop number information by 1. (However, if the hop count indicated by the extracted hop count information is larger than the hop count held by the own device, it is not updated. This is because the hop count is that of another access point that is located downstream and farther from access point 2 than the own device.) The hop count update unit 117 then notifies the connection management unit 118 of the updated hop count information.

[0025] When the connection management unit 118 is notified of the authentication response frame from frame acquisition unit 112, it responsively notifies transmission control unit 116 of an association request frame. Also, when the connection management unit 118 is notified of the association response frame from frame acquisition unit 112, it responsively puts frame acquisition unit 112 in a state where it can acquire a data frame and puts transmission control unit 116 in a state where it can transmit a data frame. Furthermore, when the connection management unit 118 acquires updated hop number information from hop number update unit 117, it generates a beacon frame including the acquired hop number information and SSID information of access point 1, and notifies transmission control unit 116 of the beacon frame.

[0026] The connection destination selection unit 115 selects a connection destination access point to be wirelessly connected to the access point 1 (own device) based on the RSSI value indicated by the RSSI information stored in the connection destination list storage unit 131 and the hop number indicated by the hop number information. Specifically, the connection destination selection unit 115 selects another access point whose RSSI value is equal to or higher than a preset reference RSSI. Here, the "reference RSSI" is a reference radio wave intensity set to a certain value, for example, between -65 dBm and -70 dBm. Next, the connection destination selection unit 115 selects, as a connection destination candidate, an access point whose hop number indicated by the hop number information extracted from the beacon frame transmitted from each of the selected other access points is the smallest from among the selected other access points. The number of candidates selected may be one or more. After that, the connection destination selection unit 115 repeatedly executes a process of selecting a connection destination candidate based on the above-mentioned RSSI value and the hop number, and selects one connection destination access point that has been selected a preset number of times (for example, three times) in succession. Then, connection destination selection unit 115 notifies frame acquisition unit 112 and transmission control unit 116 of the SSID information of the selected connection destination access point. Even if a connection has already been established, if a connection destination update period has arrived and (1) the RSSI value, which is the radio wave strength of a wireless frame from currently connected access point 1 or 2, is less than the reference RSSI, or (2) there is an access point whose number of hops extracted from a beacon frame is less than the number of hops of the currently connected access point, selection of a new connection destination access point is started.

[0027] The transmission control unit 116 transmits the data frames stored in the frame buffer 121 to the destination access point identified by the SSID information selected by the destination selection unit 115. Furthermore, when the transmission control unit 116 acquires an association request frame from the connection management unit 118, it transmits the acquired association request frame to the destination access point identified by the SSID information selected by the destination selection unit 116. Furthermore, when the transmission control unit 116 acquires a beacon frame from the connection management unit 118, it broadcasts the acquired beacon frame to other nodes.

[0028] Next, the operation of the communication system according to the present embodiment will be described in detail with reference to Fig. 5 to Fig. 8. Note that transmission and reception of ACK (ACKnowledgement) frames are omitted in Fig. 5, Fig. 6, and Fig. 8. Also, it is assumed that the access points 1A, 1B, 1C, 1D, 1E, and 2 are initially arranged and connected as shown in Fig. 1.

[0029] First, as shown in FIG. 5, the access point 2 periodically generates a beacon frame including the above-mentioned hop number information (step S1). The generated beacon frame is broadcast from the access point 2 shown in FIG. 1, and adjacent access points (e.g., access points 1A and 1B) receive it (steps S2 and S3). When the access point 1A acquires a beacon frame, it generates a beacon frame including updated hop number information in which the hop number indicated by the hop number information included in the acquired beacon frame is incremented by 1 (step S4). At this time, the hop number is set to "1". Then, the generated beacon frame is broadcast from the access point 1A. At this time, as shown in FIG. 1, the adjacent access point 1E also receives it, although it is not connected to the access point 1A (step S5). At that time, when the access point 1E receives the beacon frame, it calculates the RSSI value of the wireless frame arriving from the access point 1A that is the source of the beacon frame, generates RSSI information indicating the calculated RSSI value, and stores the information in the connection destination list storage unit 131 in association with the SSID information of the access point 1A that is the source of the beacon frame (step S6). Next, the access point 1E extracts hop number information included in the acquired beacon frame, and stores the extracted hop number information (hop number "1") in association with the SSID information of the access point 1A that is the source of the beacon frame in the connection destination list storage unit 131 (step S7).

[0030] Furthermore, when the access point 1B receives a beacon frame broadcast by the access point 2, the access point 1B generates a beacon frame including updated hop number information updated by incrementing the hop number indicated by the hop number information included in the acquired beacon frame by 1 (step S8). At this time, the hop number is set to "1". Next, the generated beacon frame is broadcast from the access point 1B and the access point 1C receives it (step S9). On the other hand, when the access point 1C receives a beacon frame, the access point 1C generates a beacon frame including updated hop number information updated by incrementing the hop number indicated by the hop number information included in the received beacon frame by 1 (step S10). At this time, the hop number is set to "2". After that, the generated beacon frame is broadcast from the access point 1C and the access point 1D receives it (step S11). On the other hand, when the access point 1D receives a beacon frame, the access point 1D generates a beacon frame including updated hop number information updated by incrementing the hop number indicated by the hop number information included in the received beacon frame by 1 (step S12). At this time, the number of hops is set to "3". After that, the generated beacon frame is broadcast from the access point 1D, and the access point 1E receives it (step S13). Here, the access point 1E extracts hop number information included in the received beacon frame, and stores the extracted hop number information in the connection destination list storage unit 131 in association with the SSID information of the access point 1D that is the transmission source of the beacon frame (step S14). In addition, when acquiring the beacon frame, the access point 1E calculates the RSSI value of the radio waves arriving from the access point 1D that is the transmission source of the beacon frame, generates RSSI information indicating the calculated RSSI value, and stores the information in the connection destination list storage unit 131 in association with the SSID information of the access point 1D that is the transmission source of the beacon frame (step S15).

[0031] Next, the access point 1E refers to the hop number information stored in the connection destination list storage unit 131 and determines whether or not there is an access point with a smaller hop number than the current connection destination access point (1D), and determines that there is an access point with a smaller hop number than the current connection destination access point (1D) (step S16). Then, the access point 1E further determines that the RSSI value indicated by the RSSI information for the current connection destination access point (1D) is less than the reference RSSI (step S17). In this case, the access point 1E refers to the RSSI information and the hop number information stored in the connection destination list storage unit 131, and since the hop number indicated by the hop number information is "3" for the current connection destination (1D) and is "1" smaller than that for the candidate access point 1A, the access point 1E selects the access point 1A as a new connection destination candidate (step S18). As described above, a specific policy for starting the step of changing the access point of the connection destination is when either of the following conditions is satisfied: (1) the RSSI value, which is the radio wave strength of the wireless frame arriving from the current connection destination, becomes less than a reference value; or (2) an access point whose hop count extracted from the beacon frame is less than the hop count of the current connection destination access point is found. For example, when the access point 1E stores RSSI information and hop count information as shown in FIG. 4, the access point 1E selects the access point 1A whose hop count is the minimum "1". Thereafter, a series of processes from steps S1 to S18 are repeated, so that the access point 1E repeatedly selects connection destination candidates as shown in FIG. 6 (step S18). In this way, by repeating a series of processes from steps S1 to S18, it is possible to avoid a situation in which both the above-mentioned conditions (1) and (2) are accidentally satisfied, and the connection destination change process for changing from the current connection destination to a new connection destination is unnecessarily repeated, or an inappropriate access point that should not be selected as a connection destination is selected. When the access point 1E determines that there is an access point 1A that has been selected as a connection destination candidate N times (N is a positive integer) in succession (step S19), the access point 1E selects the access point 1A as the connection destination (step S20).Here, N is set to "3", for example.

[0032] Next, an authentication request frame is transmitted from the access point 1E to the access point 1A (step S21), and if the authentication is successful at the access point 1A, an authentication response frame is transmitted from the access point 1A to the access point 1E (step S22). After that, an association request frame is transmitted from the access point 1E to the access point 1A (step S23), and when the access point 1A receives the association request frame, in response, an association response frame is transmitted from the access point 1A to the access point 1E (step S24). As a result, the access points 1A and 1E are wirelessly connected, as shown by the thick dashed line in FIG. 7(A).

[0033] 6, next, when a data frame is transmitted from access point 2 to access point 1A (step S25), the data frame is transmitted from access point 1A to access point 1E (step S26). Also, when a data frame is transmitted from access point 1E to access point 1A (step S27), the data frame is transmitted from access point 1A to access point 2 (step S28).

[0034] After that, the wireless environment changes, and as shown in FIG. 7(B), the communication between the access point 1A and the access point 1E is interrupted by an obstacle BA, and the positions of the access points 1C and 1D move as indicated by the arrows. Due to this situation, the beacon frame broadcast by the access point 1A can no longer be received by the access point 1E, or its RSSI value becomes less than the reference value. Under this situation, as shown in FIG. 6, it is assumed that the connection destination update period arrives again. In this case, when the above-mentioned beacon frame is broadcast from the access point 2 and received by the access point 1B (step S29), the access point 1B generates a beacon frame including updated hop number information in which the hop number indicated by the hop number information included in the acquired beacon frame is updated by incrementing it by 1 (step S30). At this time, the hop number is set to "1". Next, the generated beacon frame is broadcast from the access point 1B, and the access point 1C receives it (step S31). When the access point 1C receives the beacon frame, the access point 1C generates a beacon frame including updated hop number information obtained by incrementing the hop number indicated by the hop number information included in the received beacon frame by 1 (step S32). At this time, the hop number is set to "2". After that, as shown in FIG. 8, the generated beacon frame is broadcast from the access point 1C, and the adjacent access points 1D and 1E receive it (steps S33 and S34). When receiving the beacon frame, the access point 1E calculates the RSSI value of the wireless frame arriving from the access point 1C that is the source of the beacon frame, generates RSSI information indicating the calculated RSSI value, and stores it in the connection destination list storage unit 131 in association with the SSID information of the access point 1C that is the source of the beacon frame (step S35). Thereafter, the access point 1E extracts the hop count information and the SSID information of the access point 1C that transmitted the beacon frame contained in the acquired beacon frame, and stores the extracted hop count information and SSID information in the connection destination list memory unit 131 in association with each other (step S36).Next, the access point 1D that has received the beacon frame from the access point 1C generates a beacon frame including updated hop number information obtained by incrementing the hop number indicated by the hop number information included in the acquired beacon frame by 1 (the same process as in step S12). At this time, the hop number is set to "3". The generated beacon frame is then broadcast from the access point 1D (the same process as in step S13), and the access point 1E receives it, extracts the RSSI information, hop number information, and SSID information of the access point 1D that is the source of the beacon frame, which are included in the acquired beacon frame, and stores the extracted RSSI value, hop number, and SSID in the connection destination list storage unit 131 in association with each other (not shown). When this series of processes is executed, the access point 1E refers to the RSSI information and hop number information stored in the connection destination list storage unit 131, and selects the access point 1C, whose RSSI value is equal to or greater than a preset reference RSSI and whose hop number indicated by the hop number information is the smallest, as a connection destination candidate (step S37). In addition, since the signal from 1A, which is the current connection destination, can no longer be received, the RSSI information and the hop number information cannot be referenced for selection. Then, the series of processes from steps S29 to S37 are repeated, so that the access point 1E repeatedly selects connection destination candidates (step S37). After that, when the access point 1E determines that there is an access point 1C that has been selected as a connection destination candidate N times in a row (step S38), it selects the access point 1C as the connection destination (step S39).

[0035] Next, an authentication request frame is transmitted from the access point 1E to the access point 1C (step S40), and if the authentication is successful at the access point 1C, an authentication response frame is transmitted from the access point 1C to the access point 1E (step S41). Subsequently, an association request frame is transmitted from the access point 1E to the access point 1C (step S42), and when the access point 1C receives the association request frame, in response, an association response frame is transmitted from the access point 1C to the access point 1E (step S43). As a result, the access points 1C and 1E are wirelessly connected, as shown by the thick dashed line in FIG. 7(B).

[0036] Next, the relay process executed by the access point 1 according to the present embodiment will be described in detail with reference to Fig. 9 and Fig. 10. This relay process is started, for example, when the power supply to the access point 1 is turned on. Note that Fig. 9 and Fig. 10 omit illustration of the process of transmitting an ACK frame and the process of acquiring an ACK frame by the access point 1.

[0037] First, as shown in FIG. 9, the frame acquisition unit 112 judges whether or not a preset connection destination update period has arrived based on the elapsed time measured by the timer unit 108 (step S101). If the frame acquisition unit 112 judges that the connection destination update period has not yet arrived (step S101: No), the process of step S114 shown in FIG. 10 described later is executed. On the other hand, if the frame acquisition unit 112 judges that the connection destination update period has arrived (step S101: Yes), the frame acquisition unit 112 judges whether or not a beacon frame has been acquired (step S102). Here, as long as the frame acquisition unit 112 judges that a beacon frame has not been acquired (step S102: No), the process of step S101 is executed again. On the other hand, if the frame acquisition unit 112 judges that a beacon frame has been acquired (step S102: Yes), the frame acquisition unit 112 notifies the connection management unit 118, the hop number extraction unit 114, and the hop number update unit 117 of the acquired beacon frame. Then, the RSSI calculation unit 111 calculates the RSSI value of the wireless frame arriving from each of the other nodes that can be received by the access point 1 (own device).The RSSI calculation unit 111 also stores the calculated RSSI value in the connection destination list storage unit 131 in association with the SSID information included in the beacon frame transmitted from the corresponding access point 1 or 2 (step S103).

[0038] Next, the hop number extraction unit 114 extracts the hop number information included in the beacon frame notified from the frame acquisition unit 112 and the SSID information of the transmission source access point 1 or 2 included in the beacon frame, and stores the extracted hop number information and SSID information in the connection destination list storage unit 131 in association with each other (step S104). Next, the connection destination selection unit 115 refers to the RSSI information in the connection destination list storage unit 131 and determines whether the RSSI value of the current connection destination access point 1 or 2 is less than the reference RSSI (step S105). Here, if the connection destination selection unit 115 determines that the RSSI value of the current connection destination access point 1 or 2 is less than the reference RSSI (step S105: Yes), a process of selecting connection destination candidates is executed in step S107 described later. On the other hand, if the connection destination selection unit 115 determines that the RSSI value of the currently connected access point 1 or 2 is not less than the reference RSSI (step S105: No), it then refers to the hop count information stored in the connection destination list storage unit 131 and determines whether or not there is an access point 1 or 2 with a fewer hop count than the currently connected access point (step S106).Here, if the connection destination selection unit 115 determines that there is no access point 1 or 2 with a fewer hop count than the currently connected access point (step S106: No), it does not perform the process of selecting connection destination candidates and returns to the process of step S101.

[0039] On the other hand, when the connection destination selection unit 115 determines that there is an access point (1 or 2) with a smaller number of hops than the current connection destination access point (1 or 2) (step S106: Yes), the connection destination selection unit 115 selects, from the other access points 1 and 2, the other access point 1 or 2 with a larger RSSI value indicated by the extracted RSSI information than the RSSI value of the current connection destination and with the smallest number of hops indicated by the hop number information based on the beacon frames transmitted from each of the selected other access points 1 and 2, as a connection destination candidate (step S107). After that, the connection destination selection unit 115 determines whether the selected connection destination candidate is a connection destination candidate that has been selected N times in a row (N is a positive integer) (step S108). Here, when the connection destination selection unit 115 determines that the selected connection destination candidate is not a connection destination candidate that has been selected N times in a row (step S108: No), the process of step S101 is executed again. On the other hand, if the connection destination selection unit 115 determines that the selected connection destination candidate is a connection destination candidate that has been selected N consecutive times (step S108: Yes), it selects the selected connection destination candidate as a new connection destination access point 1 (step S109).

[0040] Next, the connection management unit 118 notifies the transmission control unit 116 of the authentication request frame, and the transmission control unit 116 transmits the notified authentication frame to the other access points 1 and 2 of the new connection destination (step S110). Next, when the frame acquisition unit 112 acquires an authentication response frame (step S111), the frame acquisition unit 112 notifies the connection management unit 118 of the acquired authentication response frame. Then, the connection management unit 118 notifies the transmission control unit 116 of an association request frame, and the transmission control unit 116 transmits the notified association request frame to the other access points 1 and 2 of the new connection destination (step S112). Next, when the frame acquisition unit 112 acquires the association response frame (step S113), the frame acquisition unit 112 notifies the connection management unit 118 of the acquired association response frame. At this time, the connection management section 118 puts the frame acquisition section 112 in a state in which it is possible to acquire a data frame, and puts the transmission control section 116 in a state in which it is possible to transmit a data frame.

[0041] 10, frame acquisition unit 112 determines whether or not a beacon frame has been acquired (step S114). If frame acquisition unit 112 determines that a beacon frame has not been acquired (step S114: No), the process of step S117 described below is executed. On the other hand, if frame acquisition unit 112 determines that a beacon frame has been acquired (step S114: Yes), it notifies hop number extraction unit 114 of the acquired beacon frame. Then, hop number extraction unit 114 extracts hop number information included in the beacon frame notified by frame acquisition unit 112 (step S115), and notifies hop number update unit 117 of the extracted hop number information. Next, if the hop number indicated by the hop number information notified by the hop number extraction unit 114 is smaller than the hop number of the own station, the hop number update unit 117 updates it by incrementing it by 1, and the connection management unit 118 acquires the updated hop number information and generates a beacon frame including the acquired hop number information and the SSID information of the own station. Then, the transmission control unit 116 broadcasts the generated beacon frame (step S116).

[0042] Next, frame acquisition unit 112 determines whether or not a data frame has been acquired (step S117). If frame acquisition unit 112 determines that a data frame has not been acquired (step S117: No), the process of step S101 is executed again. On the other hand, if frame acquisition unit 112 determines that a data frame has been acquired (step S117: Yes), frame acquisition unit 112 stores the acquired data frame in frame buffer 121. Then, transmission control unit 116 transmits the data frame stored in frame buffer 121 to the other connected access point 1 or 2 (step S118). Thereafter, the process of step S101 shown in FIG. 9 is executed again.

[0043] As described above, according to the access point 1 according to the present embodiment, the RSSI calculation unit 111 calculates the RSSI value of the radio wave frame arriving from each of the other access points 1 and 2. In addition, when the hop number extraction unit 114 acquires a beacon frame transmitted from the other access point 1 or 2, it extracts the hop number information included in the acquired beacon frame. Then, the connection destination selection unit 115 starts to specifically select a new connection destination when either (1) the RSSI value, which is the radio wave strength of the radio frame arriving from the current connection destination, becomes less than a reference value, or (2) an access point with a smaller hop number than the current connection destination access point is found, and as a result, the other access point 1 or 2 with a larger calculated RSSI value and a smaller hop number indicated by the extracted hop number information than the hop number of the current connection destination is preferentially selected as the connection destination for wireless connection. As a result, the other access point 1 or 2 with a larger RSSI value of the radio wave arriving at the access point 1 and a smaller hop number is preferentially selected, so that the quality of communication between the access point 1 and the other access point 1 or 2 can be maintained at a high level.

[0044] In a tree-shaped network constructed by an access point having a conventional WDS repeat function, the communication path from the root access point to each access point functioning as a repeater is static. Therefore, even if the communication quality deteriorates in the initial path setting of the network, the initially set communication path is maintained, and it is difficult to update the communication path to improve the communication quality. Therefore, for example, even if an obstacle is inserted between the access points and the communication quality deteriorates, it is difficult to dynamically change the communication path. In response to this, there is IEEE802.11s as a wireless LAN (Local Area Network) standard that provides redundancy to the communication path and enables dynamic change of the communication path. However, in a network constructed by multiple access points compatible with IEEE802.11s, it is necessary to periodically transmit a dedicated wireless frame in order to update the communication path to maintain good communication quality. Therefore, there is a risk that the wireless band will be compressed by the amount of wireless band used for transmitting the wireless frame. In addition, there is a risk that the communication state will become unstable due to frequent updates of the communication path.

[0045] In contrast, the communication system according to the present embodiment realizes a dynamic communication path to improve communication quality, while eliminating the need for dedicated wireless frames in IEEE802.11s. Therefore, the number of frames using the wireless band can be reduced, and the wireless band can be effectively used for transmitting data frames.

[0046] Although the embodiments of the present invention have been described above, the present invention is not limited to the configurations of the above-mentioned embodiments. For example, in each embodiment, instead of a beacon frame including hop count information, another management frame including hop count information may be adopted.

[0047] In the embodiment, an example has been described in which the mutual communication between the root access point 2 and the multiple access points 1 functioning as repeaters is performed using a channel belonging to the 5 GHz frequency band. However, this is not limiting, and the mutual communication between the root access point 2 and the multiple access points 1 functioning as repeaters may be performed using a channel belonging to the 2.4 GHz frequency band or a channel belonging to the 6 GHz frequency band.

[0048] The various functions of the access points 1 and 2 according to the present invention can be realized by using a computer system equipped with a wireless communication module, without using a dedicated system. For example, the access points 1 and 2 that execute the above-mentioned processes may be configured by distributing a program for executing the above-mentioned operations to a computer connected to a network by storing the program in a non-transitory recording medium (such as a CD-ROM) that can be read by the computer system, and installing the program in the computer system.

[0049] The method of 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 starts up 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 the access points 1 and 2 that execute the above-mentioned processes.

[0050] Although the embodiment and the modified examples of the present invention have been described above, the present invention is not limited to these. The present invention includes appropriate combinations of the embodiment and the modified examples, and appropriate modifications thereto. [Industrial Applicability]

[0051] The present invention is suitable for a communication system in which a tree-type network is constructed using access points having a WDS repeater function. [Explanation of symbols]

[0052] 1, 1A, 1B, 1C, 1D, 1E, 2: Access point, 101, 201: CPU, 102, 202: Main memory, 103, 203: Auxiliary memory, 105, 106, 205, 206: Wireless module, 108: Timer, 109, 209: Bus, 111: RSSI calculator, 112, 212: Frame acquisition unit, 114: Hop count extractor, 115: Connection destination selector, 116, 216: Transmission controller, 117: Hop count updater, 118, 215: Connection manager, 121, 221: Frame buffer, 131: Connection destination list memory, BA: Obstacle

Claims

1. A communication system comprising a root base station and a plurality of repeater base stations, The repeater base station comprises: a hop number extraction unit that, when acquiring a beacon frame transmitted from a base station of the route or another base station of the repeater, extracts hop number information indicating a number of hops that reflects the number of base stations of the repeater via which the beacon frame is transmitted from the base station of the route to the base station of the route or another base station of the repeater that transmitted the beacon frame; a hop count update unit that increments the extracted hop count by 1 and updates it as the hop count of the local station, except when the extracted hop count is greater than the hop count of the local station; a transmission control unit that broadcasts a beacon frame including the updated hop count of the own station; a radio wave intensity calculation unit that calculates radio wave intensity of a radio frame arriving from a base station of the route or a base station of another repeater; a connection destination list storage unit that stores the number of hops and the radio wave intensity extracted from the beacon frame in association with an identifier of a base station that is a source of the beacon frame; and a connection destination selection unit that selects a connection destination for wirelessly connecting to the base station of the repeater from a base station of the route or a base station of another repeater based on the calculated radio wave strength and the hop number indicated by the extracted hop number information. Communication systems.

2. When a connection destination update period arrives, the connection destination selection unit (1) The signal strength of the wireless frame arriving from the currently connected base station is less than a reference value, or (2) there is a base station whose hop count extracted from the beacon frame is less than the hop count of the currently connected base station. selecting at least one other base station whose radio wave strength is equal to or greater than a preset reference radio wave strength, and selecting, from the at least one other base station selected, an other base station whose hop count indicated by the hop count information extracted from the beacon frame transmitted from each of the at least one other base station selected, as a new connection destination; The communication system according to claim 1 .

3. the connection destination selection unit selects at least one other repeater base station having the radio wave strength equal to or greater than a preset reference radio wave strength and capable of communicating with the own station, and when repeating the process of selecting, from the at least one other base station selected, a base station of the other repeater having the smallest hop count indicated by the hop count information extracted from the wireless frame transmitted from each of the at least one other base station selected, selects the other base station selected consecutively a preset number of times as a new connection destination. The communication system according to claim 2 .

4. a radio wave intensity calculation unit that calculates radio wave intensity of a radio frame arriving from at least one other base station; a hop number extraction unit that, when receiving a beacon frame transmitted from another base station, extracts hop number information indicating a hop number reflecting the number of other base stations through which the beacon frame has been passed on the way to the own base station; a hop number update unit that, when receiving a beacon frame transmitted from another base station, increments the extracted hop number by one and updates it as the hop number of the own station, except when the extracted hop number is greater than the hop number of the own station; a transmission control unit that broadcasts a beacon frame including the updated hop count of the own station; a connection destination selection unit that selects a connection destination to be wirelessly connected to the own station from among the other base stations based on the calculated radio wave intensity and the hop number indicated by the extracted hop number information. Base station.

5. A communication method in a communication system including a root base station and a repeater base station, comprising: When the repeater base station receives a beacon frame transmitted from the base station of the route or another base station of the repeater, extracting hop number information indicating the number of hops passed from the base station of the route to the base station of the route or another base station of the repeater that transmitted the beacon frame; incrementing the extracted hop count by 1 and updating it as the hop count of the local station, except when the extracted hop count is greater than the hop count of the local station; broadcasting a beacon frame including the updated hop count of the own station; calculating radio wave intensity of a radio frame arriving from a base station on the route or a base station of another repeater; storing the number of hops and the radio wave intensity extracted from the beacon frame in association with an identifier of a base station that is a source of the beacon frame; and selecting a connection destination for wirelessly connecting to the base station of the repeater from among a base station of the route or a base station of another repeater, based on the calculated radio wave intensity and the hop number indicated by the extracted hop number information. Communication methods.

6. Computer, a radio wave intensity calculation unit that calculates radio wave intensity of a radio frame arriving from at least one other base station; a hop number extraction unit that, when receiving a beacon frame transmitted from another base station, extracts hop number information indicating a hop number reflecting the number of other base stations through which the beacon frame has been passed on the way to the own base station; a connection destination selection unit that selects a connection destination to be wirelessly connected to the own station from among the other base stations based on the calculated radio wave intensity and the hop number indicated by the extracted hop number information; a hop number update unit that, when acquiring a beacon frame transmitted from another base station, increments the extracted hop number by one and updates it as the hop number of the own station, except when the extracted hop number is larger than the hop number of the own station; a transmission control unit that broadcasts a beacon frame including the updated hop count of the own station; A program to function as a

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