CN109495154B - Wireless relay device and wireless relay method - Google Patents

Wireless relay device and wireless relay method Download PDF

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Publication number
CN109495154B
CN109495154B CN201811468892.2A CN201811468892A CN109495154B CN 109495154 B CN109495154 B CN 109495154B CN 201811468892 A CN201811468892 A CN 201811468892A CN 109495154 B CN109495154 B CN 109495154B
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wireless
channel
wireless communication
communication
communication channels
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CN109495154A (en
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塚本贵士
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Yamaha Corp
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Yamaha Corp
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/14—Relay systems
    • H04B7/15—Active relay systems
    • H04B7/155—Ground-based stations
    • H04B7/15528—Control of operation parameters of a relay station to exploit the physical medium
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W72/00—Local resource management
    • H04W72/50—Allocation or scheduling criteria for wireless resources
    • H04W72/54—Allocation or scheduling criteria for wireless resources based on quality criteria
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W84/00—Network topologies
    • H04W84/02—Hierarchically pre-organised networks, e.g. paging networks, cellular networks, WLAN [Wireless Local Area Network] or WLL [Wireless Local Loop]
    • H04W84/10—Small scale networks; Flat hierarchical networks
    • H04W84/12—WLAN [Wireless Local Area Networks]

Abstract

The convenience of the wireless LAN can be improved by measuring the use state of the wireless communication channel during the operation of the wireless relay device and effectively using a plurality of wireless communication channels without degrading the convenience of the wireless LAN. Provided is a wireless relay device provided with: a selection unit that cyclically selects each of a plurality of wireless communication channels; and a communication control unit that communicates with the wireless terminal apparatus via at least one of the wireless communication channels cyclically selected by the selection unit and that performs at least either one of communication via the channel and measurement of the radio wave state of the channel for each of the wireless communication channels cyclically selected by the selection unit, wherein the selection unit selects each of the plurality of wireless communication channels such that the wireless communication channel on which only the measurement of the radio wave state is performed is discontinuously selected among the plurality of wireless communication channels.

Description

Wireless relay device and wireless relay method
This application is a divisional application based on chinese national application No. 201380010041.2 application (wireless relay device, wireless relay method, control program, and recording medium) filed on 28/2/2013, and the contents thereof are cited below.
Technical Field
The present invention relates to a wireless relay apparatus and a wireless relay method that constitute a wireless lan (local Area network) together with a wireless terminal apparatus.
Background
IEEE802.11 is known as a communication standard for wireless LAN. The communication standards are roughly classified into a standard using a communication radio wave of a 2.4GHz band (ieee802.11b and the like) and a standard using a communication radio wave of a 5GHz band (ieee802.11a and the like). The 2.4GHz band and the 5GHz band are each further divided into a plurality of wireless communication channels. For example, in japan, the 2.4GHz band of ieee802.11b is divided into 14 wireless communication channels separated by 5 MHz. In general, a wireless relay device such as a wireless access point device that forms a wireless LAN together with a wireless terminal device corresponds to any one of the 2 frequency bands, and communicates with the wireless terminal device by using any one of wireless communication channels in the frequency band in a fixed manner. Therefore, when a wireless relay device is newly installed, it is necessary to investigate the use state around the installation location of each wireless communication channel in the frequency band corresponding to the wireless relay device (site survey) and select a wireless communication channel with less interference.
However, since the use state of the communication radio wave changes every moment, it is sometimes insufficient to perform the wireless survey only at the time of installation of the wireless relay device. For example, there are cases where: after a wireless relay device is installed, a new wireless LAN or the like is constructed adjacent to the wireless relay device, and an interference source of radio waves appears later, or even if an interference source operating only in a specific time band already exists, the interference source may not operate occasionally at the time of wireless survey. Therefore, various techniques for solving such problems have been proposed, and one example thereof is a technique disclosed in patent document 1.
Patent document 1 discloses a technique of recording, with respect to a wireless relay device during operation, the usage status and the presence or absence of interference of a wireless communication channel around the wireless relay device. The wireless relay device disclosed in patent document 1 transmits a special beacon (monitoring beacon) indicating the start of measurement at a certain timing during operation. A CFP parameter indicating that communication is prohibited for a constant period is set in the monitoring beacon. Each wireless terminal device accommodated in the wireless relay device prohibits a new communication start (transmission of a communication radio wave) in accordance with a period indicated by the CFP parameter when the monitoring beacon is received, and scans radio waves of surrounding BSSs. After the constant time has elapsed since the reception of the monitoring beacon (i.e., after the prohibition is released), each wireless terminal apparatus returns the scanning result to the wireless relay apparatus. The wireless frames received by each wireless terminal device while communication is prohibited are transmitted from neighboring wireless relay devices. By recording information transmitted from each wireless terminal device in the wireless relay device, the usage status and the presence or absence of interference with the wireless communication channel around the wireless relay device can be recorded.
Patent document 1: japanese patent No. 4654507
Patent document 2: japanese patent No. 3821220
Non-patent document 1: "Connecting to Multiple IEEE802.11Networks Using a Single Wireless Card", Ranveer Chandar, Paravir Bahl, PradepBahl, Proceding of IEEE info 2004, March 7-11, 2004, < http:// research. microsoft.com/en-us/um/redmond/project/virtualwifi/m ultinet _ info _ pdf
Disclosure of Invention
However, in the technique disclosed in patent document 1, communication is prohibited for all wireless terminal apparatuses housed in the wireless relay apparatus every time radio waves of a surrounding BSS are scanned, and thus the throughput is reduced. In addition, in the technique disclosed in patent document 1, since CFP is used for monitoring purposes, CFP cannot be used for PCF access (access by polling from a wireless relay device) which is an original use. As described above, the technique disclosed in patent document 1 has the following problems: the convenience (accessibility) of the wireless LAN is reduced due to a decrease in throughput, restrictions imposed on the use of CFPs, and the like.
The present invention has been made in view of the above-described problems, and a first object of the present invention is to measure the usage status of a wireless communication channel during the operation of a wireless relay device without degrading the convenience of a wireless LAN, and a second object of the present invention is to improve the convenience of a wireless LAN by effectively using a plurality of wireless communication channels.
In order to solve the above problem, one aspect of the present invention provides a wireless relay device including: a selection unit that cyclically selects each of a plurality of wireless communication channels; and a communication control unit that performs at least one of communication with a wireless terminal apparatus via the wireless communication channel and measurement of a radio wave state of the wireless communication channel for each of the wireless communication channels selected cyclically by the selection unit, wherein the communication control unit performs communication with the wireless terminal apparatus via at least 1 of the wireless communication channels selected by the selection unit. According to such a wireless relay device, for example, if communication with the wireless terminal device is performed in at least 1 of the plurality of wireless communication channels and the radio wave state is measured in the wireless communication channel including (or excluding) the wireless communication channel, the usage state of the wireless communication channel can be measured during the operation of the wireless relay device. When 1 wireless communication channel is selected cyclically from a plurality of wireless communication channels, the wireless communication channel on which only the radio wave state is measured is selected discontinuously, thereby preventing a large decrease in throughput. Further, it is possible to avoid a large decrease in throughput by reducing the number of channels for which only radio wave state measurement is performed to be less than the number of channels for communication or by suppressing the selection frequency per unit time for wireless communication channels for which only radio wave state measurement is performed to be low. In addition, if communication with the wireless terminal apparatus is performed in a plurality of wireless communication channels, the plurality of wireless communication channels can be effectively used, and the convenience of the wireless LAN can be improved.
Here, the plurality of radio communication channels may belong to 1 frequency band, and the plurality of radio communication channels may belong to a plurality of frequency bands. Further, when each of the plurality of wireless communication channels belongs to one of a plurality of different frequency bands, the communication control unit may be configured to measure only the radio wave state of the wireless communication channel belonging to a predetermined frequency band among the plurality of wireless communication channels. As described above, as communication standards of the current wireless LAN, there are 2 types of standards that use a communication radio wave of a 2.4GHz band and 2 types of standards that use a communication radio wave of a 5GHz band (as an example, there is a possibility that another frequency band is used according to the communication standard). In the case where the plurality of frequency bands different from each other are the above-described 2.4GHz band and 5GHz band, for example, each wireless communication channel of the 2.4GHz band may be used for communication with the wireless terminal device, and only the usage status may be measured for the wireless communication channel of the 5GHz band (or each frequency band may be used in reverse).
Patent document 2 discloses a wireless relay device that supports both the 2.4GHz band and the 5GHz band. The wireless relay device disclosed in patent document 2 includes a receiving unit and a transmitting unit corresponding to each communication standard, and the receiving unit is configured to operate the receiving unit corresponding to each communication standard at all times, and the transmitting unit is configured to operate only one of the receiving unit and the transmitting unit as necessary. Thereby, reduction in power consumption is achieved. As described above, unlike the present invention, the invention of patent document 2 is different from the present invention in that the wireless relay device disclosed in patent document 2 aims to reduce power consumption by operating only one of the transmission units corresponding to the 2.4GHz band and the 5GHz band, as needed, and the invention of the present application aims to measure the usage status of the wireless communication channel during the operation of the wireless relay device without degrading the convenience of the wireless LAN, thereby effectively utilizing a plurality of wireless communication channels and improving the convenience of the wireless LAN.
In another aspect, the radio communication system further includes a channel load factor measuring unit configured to measure a channel load factor of a radio communication channel used for communication with the radio terminal apparatus among the plurality of radio communication channels, and the selecting unit is configured to adjust a period during which the radio communication channel is in the selected state, for each of the radio communication channels used for communication with the radio terminal apparatus, based on the channel load factor measured by the channel load factor measuring unit. For example, by shortening the selection period of a radio communication channel with a low channel load factor and conversely lengthening the selection period of a radio communication channel with a high channel load factor, each radio communication channel can be used more efficiently.
In addition, as another mode, the following mode can be conceived: the wireless communication system further includes a monitoring result reflecting unit that determines whether or not interference is present in a wireless communication channel used for communication with the wireless terminal device among the plurality of wireless communication channels, and if it is determined that interference is present, changes at least one of a wireless communication channel used for communication with the wireless terminal device, a communication speed, and a transmission power. According to this aspect, when interference is found in a wireless communication channel used for communication with the wireless terminal apparatus, operations for improving the communication status, such as switching of a communication target channel and adjustment of communication parameters (communication speed and transmission power), are automatically performed.
Another aspect is characterized by further comprising: a storage unit; and an authentication control unit that performs authentication in response to receiving an authentication request from a wireless terminal device via any one of the plurality of wireless communication channels, and when the authentication is successful, writes a terminal identifier indicating the wireless terminal device in the storage unit in association with the wireless communication channel, and when data addressed to a wireless terminal device using the wireless communication channel is received while the wireless communication channel is not selected, the communication control unit writes the data in the storage unit in association with the wireless communication channel, and transmits the data to the wireless terminal device in response to the wireless communication channel being selected again by the selection unit. According to this aspect, when the wireless communication channel used for communication with the wireless terminal apparatus is selected again, the data communication performed at the time of the last selection can be resumed.
In another aspect, the communication control unit instructs a wireless terminal device that is communicating using radio waves of a wireless communication channel before switching the wireless communication channel to prohibit a start of new communication until the wireless communication channel is next selected. According to this aspect, it is possible to prevent the radio terminal apparatus from performing unnecessary data transmission while the radio communication channel used for communication with the radio terminal apparatus is not selected. Further, non-patent document 1 discloses the following technique: when a connection destination is switched from a certain wireless network to another wireless network, the entry into the power saving mode is notified to a communication destination (wireless relay apparatus or wireless terminal apparatus) before the switching, and transmission of unnecessary frames to the own apparatus is suppressed. However, only the wireless terminal device is a device capable of notifying the communication destination of the entry into the power saving mode, and the technique disclosed in non-patent document 1 is completely different from the invention of the present application which is an invention relating to a wireless relay device.
Another aspect of the present invention provides a wireless relay method in a wireless relay apparatus, wherein each of a plurality of wireless communication channels is cyclically selected, at least one of communication with a wireless terminal apparatus via the wireless communication channel and measurement of a radio wave state of the wireless communication channel is performed for each of the cyclically selected wireless communication channels, and communication with the wireless terminal apparatus is performed via at least 1 of the selected wireless communication channels.
Another aspect of the present invention provides a control method for a processing unit of a wireless relay device, wherein the processing unit is controlled to operate as a selection means that cyclically selects each of a plurality of wireless communication channels and a communication control means that performs at least one of communication with a wireless terminal device via the wireless communication channel and measurement of a radio wave state of the wireless communication channel for each of the wireless communication channels cyclically selected by the selection means, and the communication control means is controlled to perform communication with the wireless terminal device via at least 1 of the wireless communication channels selected by the selection means.
Another aspect of the present invention provides a control program for causing a processing unit of a wireless relay device to operate as selection means for cyclically selecting each of a plurality of wireless communication channels and communication control means for performing at least one of communication with a wireless terminal device via the wireless communication channel and measurement of a radio wave state of the wireless communication channel for each of the wireless communication channels cyclically selected by the selection means, wherein the communication control means is controlled to perform communication with the wireless terminal device via at least 1 of the wireless communication channels selected by the selection means.
Another aspect of the present invention provides a nonvolatile recording medium for storing the control program.
Drawings
Fig. 1 is a diagram showing a configuration example of a wireless relay device 1A according to embodiment 1 of the present invention.
Fig. 2 is a diagram for explaining the effect of embodiment 1.
Fig. 3 is a diagram showing a configuration example of a radio relay apparatus 1B according to embodiment 2 of the present invention.
Fig. 4 is a diagram showing an example of a modification of embodiment 2.
Fig. 5 is a diagram showing an example of a modification of embodiment 2.
Fig. 6 is a diagram showing a configuration example of a wireless relay apparatus 1C according to embodiment 3 of the present invention.
Fig. 7 is a flowchart showing an example of the operation of embodiment 3.
Fig. 8 is a diagram for explaining the effect of embodiment 3.
Fig. 9 is a diagram showing a configuration example of a wireless relay device 1D according to embodiment 4 of the present invention.
Fig. 10 is a flowchart showing an example of the operation of embodiment 4.
Fig. 11 is a block diagram showing a schematic configuration of a wireless relay device according to each embodiment of the present invention.
Fig. 12 is a flowchart showing an example of communication control executed by the radio relay apparatus according to each embodiment of the present invention.
Detailed Description
(schematic structure)
Fig. 11 is a block diagram showing a schematic configuration of a wireless relay device according to each embodiment of the present invention.
The wireless relay device includes a Processing unit including a cpu (central Processing unit)11, a rom (read Only memory)12, and a ram (random Access memory)13, an operation unit 21, a1 st wireless unit 23, a 2 nd wireless unit 25, and antennas 24 and 26 on a bus 27.
A work area used when the CPU 11 executes the communication control program is set in the RAM 13. The ROM 12 stores a basic program for executing an application program of the wireless terminal apparatus. The ROM 12 is, for example, a flash memory, and can store downloaded application programs and the like in addition to the basic program.
The operation unit 21 detects an operation of transmitting various instructions from the user to the wireless relay apparatus. The configuration of the operation unit 21 is not essential, and the wireless relay apparatus may be configured to receive an instruction from another device. According to a communication control program executed by the CPU 11, communication is performed with other wireless devices via the 1 st RF unit 23 and the antenna 24, or the 2 nd RF unit 25 and the antenna 26.
Fig. 12 is a flowchart showing an example of communication control executed by the radio relay apparatus according to each embodiment of the present invention.
In step S1, the CPU 21 selects 1 wireless communication channel from the plurality of wireless communication channels. The CPU 21 determines whether or not the selected wireless communication channel is a channel for communicating with the wireless terminal apparatus via the channel, or a channel for measuring the radio wave state of the selected channel (step S2). When the selected wireless communication channel is a channel for communicating with the wireless terminal apparatus via the channel, the CPU 21 performs communication with the wireless terminal apparatus via the wireless unit (the 1 st RF unit 23 and the antenna 24, or the 2 nd RF unit and the antenna 26) corresponding to the selected wireless communication channel (step S3). On the other hand, when the selected wireless communication channel is a channel for measuring the radio wave state of the selected channel, the CPU 21 measures the radio wave state of the selected channel (step S4). Then, a channel switching determination is made (step S5), and if it is the timing for switching, the process returns to step S1 again, and another wireless communication channel is selected to perform the same communication control. Thus, each of the plurality of wireless communication channels is cyclically selected, and at least one of communication and radio wave state measurement is performed for each wireless communication channel. Further, communication with the wireless terminal apparatus is performed using at least 1 wireless communication channel out of the cyclically selected wireless communication channels.
Each of the components and units of the wireless terminal apparatus described in the following embodiments is mainly implemented as a functional block of a processing unit including the CPU 21, but may be implemented by providing a processing unit other than the CPU 21 (without limitation to any hardware or software), or by providing dedicated hardware.
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(A: embodiment 1)
Fig. 1 is a diagram showing an example of a hardware configuration of a radio relay apparatus 1A as a first embodiment of the radio relay apparatus according to the present invention. The wireless relay device 1A is a so-called dual-band-compatible relay device (switching hub) that is compatible with both the 2.4GHz band and the 5GHz band. The wireless relay device 1A is configured to cyclically select 1 wireless communication channel (hereinafter, referred to as ch (a)) in the 2.4GHz band and 1 wireless communication channel (hereinafter, referred to as ch (b)) in the 5GHz band, and to communicate with the wireless terminal devices corresponding to the respective bands via the selected wireless communication channels. Hereinafter, as in ch (a) and ch (b) in the present embodiment, a radio communication channel actually used in communication with a radio terminal apparatus is referred to as a "target channel for communication".
The antenna 101 and the RF unit 103 constitute a wireless communication unit corresponding to a 2.4GHz band, and the antenna 102 and the RF unit 104 constitute a wireless communication unit corresponding to a 5GHz band. Antenna 101 receives and transmits communication radio waves of 2.4GHz band, and antenna 102 receives and transmits communication radio waves of 5GHz band. The RF unit 103 converts the communication radio wave received and transmitted by the antenna 101 into an internal signal, and the RF unit 104 converts the communication radio wave received and transmitted by the antenna 102 into an internal signal.
The RF selection unit 105 selects one of the RF unit 103 and the RF unit 104 in accordance with a selection instruction transmitted from the channel selection control unit 123, and switches the frequency band (channel) of the reception/transmission signal. The RF selection unit 105 transmits the internal signal transmitted from the modulation and coding unit 126 to one of the RF unit 103 and the RF unit 104 selected in accordance with the selection instruction. Further, the RF selection unit 105 transmits, to the carrier signal detection unit 130, an internal signal output from one of the internal signals (i.e., signals indicating data received via the wireless section of each frequency band) output from the RF units 103 and 104, respectively, the internal signal being selected in accordance with the selection instruction.
The carrier signal detection unit 130 analyzes the frequency component of the signal (i.e., the received signal) transmitted from the RF selection unit 105, and extracts the carrier signal of the radio communication channel instructed by the channel selection control unit 123. When the signal strength of the extracted carrier signal is equal to or greater than a constant value, the carrier signal detection unit 130 transmits the carrier signal to the demodulation and decoding unit 106. The demodulation/decoding unit 106 demodulates and decodes the carrier signal transmitted from the carrier signal detection unit 130, and extracts a frame (more precisely, a MAC frame) superimposed on the carrier signal. Then, the demodulation/decoding unit 106 transmits the MAC frame extracted from the carrier signal to the frame assigning unit 107.
The frame assigning unit 107 determines which of the control frame and the data frame is used for each MAC frame (hereinafter, referred to as a received MAC frame) transmitted from the demodulation/decoding unit 106, and transmits the control frame to the radio control unit 108 and the data frame to the bridge function unit 116. Here, the control frame refers to a frame related to control of communication with the target device, and the data frame refers to a frame for transmitting data received/transmitted with the target device. The determination of whether the MAC frame is a control frame or a data frame may be made by referring to frame type information included in the header of the received MAC frame.
The radio control unit 108 is a radio communication controller that performs communication control of a radio MAC layer (i.e., a data link layer). As shown in fig. 1, the wireless relay device 1A according to the present embodiment includes 2 types of wireless communication units corresponding to the 2.4GHz band and the 5GHz band, but only 1 wireless control unit 108 is provided for a wireless communication controller that performs communication control in the wireless MAC layer. In a conventional dual-band-compatible radio relay device (for example, a radio relay device disclosed in patent document 2), a dedicated radio communication controller is generally provided for each radio communication unit corresponding to each communication standard. According to the wireless relay device 1A of the present embodiment, the number of wireless controllers can be reduced, and the manufacturing cost can be reduced as compared with the conventional dual-band compatible wireless relay device.
The radio control unit 108 analyzes the control frame transmitted from the frame assigning unit 107, and extracts context information used for communication control of the radio MAC layer. The context information extracted in this manner is stored in a control information storage unit such as a RAM corresponding to each communication object channel. To describe in more detail, the context information of ch (a) is held by the ch (a) control information holding unit 109, and the context information of ch (b) is held by the ch (b) control information holding unit 110. In the communication control at the MAC layer, means for generating various control timings is required to perform the periodic transmission of a beacon for notifying the BSS of the radio relay apparatus 1A and the timing control according to CSMA/CA. CSMA/CA is a mechanism for avoiding collision of communication waves in a wireless LAN, and is defined in detail in IEEE 802.11. For the details of this CSMA/CA, IEEE802.11 can be referred to. In the present embodiment, means for generating various control timings is also provided for each communication target channel. Ch (a) timing generating section 111 generates control timing concerning ch (a), and ch (b) timing generating section 112 generates control timing concerning ch (b).
The radio control unit 108 generates a control frame related to a beacon frame and communication control of the MAC layer, and transmits the control frame to the control frame queue 120. The control frame is generated only for the communication target channel selected at that time. Therefore, the control frame queue 120 is not set for each communication object channel. When the control frame transmitted from the frame assigning unit 107 is an authentication request frame transmitted from a wireless terminal apparatus, the wireless control unit 108 inquires of the authentication control unit 113 whether or not the wireless terminal apparatus can be accepted. When making this inquiry, the radio control unit 108 acquires channel information indicating the communication destination channel that has received the authentication request frame from the selected channel storage unit 125, and transmits the channel information to the authentication control unit 113. The authentication request frame is a frame in which a communication packet for requesting permission of use of the wireless relay apparatus 1A (that is, data communication via the wireless relay apparatus 1A) is written.
The authentication control unit 113 performs authentication as follows: whether or not a wireless terminal device that is the source of the authentication request frame can be accommodated in the wireless communication channel that has received the authentication request frame. For example, the authentication is not successful when the wireless communication channel on which the authentication request frame is received is not the communication target channel, and the authentication is not successful when the wireless terminal apparatus that is the transmission source of the authentication request frame is not a pre-registered apparatus even when the wireless communication channel is the communication target channel. Then, if the authentication is successful, the authentication control section 113 transmits a reply indicating the successful authentication to the wireless control section 108, and adds information (MAC address in the present embodiment) indicating the wireless terminal device to the authentication list. As shown in fig. 1, the authentication list is provided for each communication destination channel, and the authentication control unit 113 adds a terminal identifier (for example, a MAC address of the wireless terminal device) indicating a wireless terminal device that has succeeded in authentication to either the ch (a) authentication list 114 or the ch (b) authentication list 115, based on channel information transmitted when the inquiry is received. Thus, the terminal identifier of the wireless terminal device permitted to use ch (a) and performing data communication via the wireless relay device 1A is stored in the ch (a) authentication list 114, and the terminal identifier of the wireless terminal device permitted to use ch (b) and performing data communication via the wireless relay device 1A is stored in the ch (b) authentication list 115. The ch (a) authentication list 114 and the ch (b) authentication list 115 are stored in a storage unit (not shown in fig. 1) such as a RAM, together with a ch (a) data frame queue 118, a ch (b) data frame queue 119, and a control frame queue 120, which will be described later. Then, if a response to the above-described inquiry is received from the authentication control unit 113 (that is, if the authentication is possible, the wireless control unit 108 generates a control frame (authentication response frame) corresponding to the response result, and transmits the control frame to the control frame queue 120.
The bridge function section 116 performs bridging (transfer control) of the data frame transmitted from the frame assigning section 107. The following conditions apply: for example, a data frame received via ch (a) is transmitted via ch (b) (or vice versa). When the wireless relay device 1A includes the wired LAN i/F and is also connected to a wired LAN, the bridging function unit 116 also bridges the wired LAN and the wireless LAN.
The frame output from the bridge function section 116 (i.e., a data frame to be transmitted to the wireless section, hereinafter referred to as a transmission data frame) is transmitted to the data frame queue selection section 117. In the present embodiment, 2 types of queues for accumulating transmission data frames, that is, a ch (a) data frame queue 118 and a ch (b) data frame queue 119, are provided for each communication target channel. The data frame queue selecting unit 117 searches the authentication list of each communication destination channel using the transmission destination MAC address of the head of the transmission data frame as a key, determines which authentication list is registered in, and transmits the transmission data frame to the data frame queue of the communication destination channel corresponding to the authentication list. In addition, when the transmission data frame is a broadcast frame, it is sufficient to transmit the broadcast frame to both transmission data queues. In addition, in the case where the transmission destination MAC address of the transmission data frame does not coincide with any MAC address of the authentication list, the data frame queue selecting section 117 discards the transmission data frame without transmitting it to any queue.
The transmission frame selector 121 takes out frames from the ch (a) data frame queue 118, the ch (b) data frame queue 119, and the control frame queue 120, and transmits the frames to the modulation/coding unit 126. Here, the radio control unit 108 instructs the timing of frame extraction from each queue. Further, from which queue a frame is to be taken out is determined based on the following points. First, the frame stored in the control frame queue 120 is preferentially fetched over the frames stored in the ch (a) data frame queue 118 and the ch (b) data frame queue 119. That is, only when the control frame queue 120 is empty at the fetch timing instructed by the radio control unit 108, frames stored in the ch (a) data frame queue 118 and the ch (b) data frame queue 119 are fetched. As described above, the reason why the control frame is preferentially taken out is to prevent an obstacle from being generated in the communication control of the MAC layer.
When a frame is extracted from any one of the ch (a) data frame queue 118 and the ch (b) data frame queue 119, the transmission frame selection unit 121 extracts the frame from the data frame queue corresponding to the communication destination channel selected at that time, based on the information stored in the selected channel storage unit 125. The modulation/coding unit 126 codes the frame transmitted from the transmission frame selection unit 121, including encryption, into a radio frame, and superimposes the radio frame on the carrier of the communication target channel specified by the channel selection control unit 123. Then, the modulation/coding unit 126 transmits the internal signal corresponding to the superimposition result to the RF selection unit 105.
The channel switching timing generating unit 122 in fig. 1 is, for example, an interval timer or the like having a cycle of 10ms (milliseconds), generates a periodic timing having an interval of 50ms, 100ms, 150ms, or the like, and outputs a timing signal indicating the timing. The channel selection control unit 123 determines the timing of switching the communication target channel with the timing indicated by the timing signal output from the channel switching timing generation unit 122 as the basic timing, and transmits a selection instruction to the RF selection unit 105. For example, when the beacon period is 150ms, the period of channel switching (hereinafter, referred to as a channel switching period) may be 50ms or the like. Each time the timing signal is received, the channel selection controller 123 cyclically switches the communication destination channel so that ch (a) → ch (b) → ch (a) ·. That is, in the radio relay apparatus 1A according to the present embodiment, the RF selection unit 105, the channel switching timing generation unit 122, and the channel selection control unit 123 function as selection means for cyclically selecting ch (a) and ch (b) as channels to be communicated.
To describe in more detail, the channel selection control section 123 that has received the timing signal first transmits a CTS frame transmission instruction To the CTS (clear To send) frame transmission control section 124. Here, the CTS frame is a frame for transmitting a CTS message specified in IEEE802.11 in order to avoid a hidden terminal problem in the wireless LAN. The CTS message is a communication message that transmits data transmission permission to 1 of the wireless communication apparatuses in the BSS and instructs to prohibit the start of communication with another wireless communication apparatus. The CTS message is provided with an address field in which a communication address of a wireless communication apparatus to which data transmission permission is given is set, and a duration field in which data having a length indicating a period for which communication with another wireless communication apparatus is prohibited is set. For details of the CTS message and rts (request to send)/CTS, which is a mechanism for avoiding the hidden terminal problem by using the CTS message, please refer to IEEE 802.11.
The CTS frame transmission control unit 124 generates a CTS frame in which the MAC address of the wireless relay device 1A is set in the address field and a time corresponding to the channel switching cycle is set in the duration field, and transmits the CTS frame to the control frame queue 120. If the CTS frame is taken out by the transmission frame selector 121, the control frame queue 120 discards all other control frames queued at that time. This is because, if switching of the communication subject channel occurs, the control frame related to control of communication via the communication subject channel before the switching is invalidated at the earliest. The channel selection control unit 123, if notified from the CTS frame transmission control unit 124 that the CTS frame has been transmitted, instructs the RF selection unit 105, the demodulation/decoding unit 106, and the modulation/coding unit 126 to new communication target channels after setting a predetermined guard time. Here, the guard time may be selected to have an appropriate value according to the time required for switching the communication destination channel, and may be, for example, 10 ms. In this way, if the switching of the communication destination channel is completed, the selected channel holding section 125 holds the channel number of the currently selected communication destination channel.
The above is the configuration of the wireless relay apparatus 1A.
Next, the effects of the present embodiment will be described with reference to fig. 2.
Fig. 2(a) is a diagram showing a case of a wireless LAN when ch (a) is selected in the wireless relay apparatus 1A, and fig. 2(B) is a diagram showing a case of a wireless LAN when ch (B) is selected in the wireless relay apparatus 1A. In each of fig. 2(a) and 2(B), the wireless terminal apparatus a and the wireless terminal apparatus c are apparatuses corresponding to the 2.4GHz band, and perform frame reception/transmission with the wireless relay apparatus 1A via ch (a). On the other hand, the wireless terminal apparatus b and the wireless terminal apparatus d are apparatuses corresponding to the 5GHz band, and perform frame reception/transmission with the wireless relay apparatus 1A via ch (b). In the following, the beacon period is 100ms and the channel switching period is 50ms for both the ch (a) and ch (b) radio communication channels.
As shown in fig. 2(a), when ch (a) is selected, the wireless terminal apparatus a and the wireless terminal apparatus c request authentication, respectively, and if the authentication succeeds, the MAC addresses of the wireless terminal apparatus a and the wireless terminal apparatus c are registered in the ch (a) authentication list 114 of the wireless relay apparatus 1A, respectively. In this way, if the authentication by the wireless relay apparatus 1A is successful, the wireless terminal apparatus a and the wireless terminal apparatus c can transmit the frame to the wireless relay apparatus 1A through ch (a), respectively. For example, a data frame transmitted from the radio terminal apparatus a to the radio terminal apparatus c is bridged by the radio relay apparatus 1A and transferred to the radio terminal apparatus to which the data frame is to be transmitted (that is, the radio terminal apparatus c) via the ch (a) data frame queue 118.
If a channel switching cycle (50ms in this operation example) has elapsed after ch (a) is selected as the channel to be communicated, the radio relay apparatus 1A transmits a CTS frame and prohibits the radio terminal apparatus from communicating via ch (a). As shown in fig. 2C, the prohibition period is a period (i.e., 60ms) obtained by adding a guard time (10ms) to a time (50ms) until ch (a) is selected next. In the prohibition period, even if a frame is transmitted to the radio section, the radio terminal apparatus a and the radio terminal apparatus c wait for the frame to be queued, and the transmission of the frame is retained until the prohibition period ends.
After transmitting the CTS frame, the wireless relay apparatus 1A switches the channel to be communicated to ch (b). As shown in fig. 2(B), when ch (B) is selected, the wireless terminal apparatus B and the wireless terminal apparatus d request authentication, respectively, and if the authentication succeeds, the MAC addresses of the wireless terminal apparatus B and the wireless terminal apparatus d are registered in the ch (B) authentication list 115 of the wireless relay apparatus 1A, respectively. In this way, if the authentication by the radio relay apparatus 1A is successful, the radio terminal apparatus b and the radio terminal apparatus d can transmit the frame to the radio relay apparatus 1A by using ch (b), respectively. For example, a data frame transmitted from the radio terminal apparatus b to the radio terminal apparatus d is bridged by the radio relay apparatus 1A, and is transferred to the radio terminal apparatus to which the data frame is to be transmitted (that is, the radio terminal apparatus d) via the ch (b) data frame queue 119. When frames are transmitted from the wired LAN to the wireless terminal apparatus a or the wireless terminal apparatus c (i.e., a terminal using an unselected communication destination channel) while ch (b) is selected, the frames are queued in the ch (a) data frame queue 118 based on the ch (a) authentication list 114 and are kept transmitted.
If a channel switching cycle elapses after ch (b) is selected, the wireless relay device 1A transmits a CTS frame and prohibits the wireless terminal device from communicating via ch (b), and switches the communication target channel to ch (a) after the CTS frame is transmitted. If the prohibited period of ch (a) ends, the radio relay apparatus 1A first transmits a frame waiting for queuing in the ch (a) data frame queue 118 while ch (b) is selected. Similarly, the radio terminal apparatus a and the radio terminal apparatus c sequentially transmit the frames when the frames to be transmitted are stored in the communication prohibition period. Further, although it is possible that frames remaining to be transmitted are buoyed immediately after the end of the prohibition period, it is sufficient if transmission control is performed on these frames according to the mechanism of CSMA/CA.
As described above, according to the wireless relay device 1A of the present embodiment, in one wireless relay device, the wireless terminal device corresponding to the 2.4GHz band and the wireless terminal device corresponding to the 5GHz band can perform communication in parallel, and thus, a plurality of wireless communication channels can be effectively used, and the convenience of the wireless LAN can be improved.
(B: embodiment 2)
Next, a radio relay apparatus 1B according to embodiment 2 of the present invention will be described. The wireless relay device 1B makes a round and selects a plurality of wireless communication channels (ch (a), ch (c), and ch (d) in the present embodiment) belonging to the 2.4GHz band one by one, and performs at least one of communication with the wireless terminal device using the selected wireless communication channel or detection of the electric field intensity of the wireless communication channel (i.e., wireless survey). To explain in more detail, in the present embodiment, communication via the channel and monitoring of the electric field strength are performed for ch (a), and only the electric field strength is monitored for ch (c) and ch (d), respectively. Here, the electric field strength is measured for ch (a) which is a communication target channel, in order to detect the presence or absence of interference in the channel. Further, ch (c) and ch (d) may be wireless communication channels in the 5GHz band, respectively. If ch (c) and ch (d) are wireless communication channels of 5GHz bands, respectively, the electric field intensity is monitored only for the 5GHz band.
As the selection order of the radio communication channels in the present embodiment, it is conceivable to select the radio communication channels in the order of ch (a), ch (c), and ch (d). However, since communication via a communication target channel is prohibited while a wireless communication channel (hereinafter, referred to as a monitoring target channel) for monitoring only the electric field intensity is selected, it is preferable to discontinuously select the monitoring target channel so as to shorten the prohibition period as much as possible. For example, in the present embodiment, channel selection may be performed so as to be ch (a) → ch (c)) → ch (a)) → ch (d)) → ch (a)) → ch (c) …. In the state where ch (a) is selected, communication is first performed via the wireless communication channel, and then the channel is monitored.
Fig. 3 is a diagram showing a configuration example of a radio relay apparatus 1B according to embodiment 2 of the present invention. In fig. 3, the same components as those in fig. 1 are denoted by the same reference numerals. As is clear from a comparison between fig. 3 and fig. 1, the configuration of radio relay device 1B differs from that of radio relay device 1A in that it includes electric field strength measurement section 127, electric field strength measurement control section 128, and measurement result storage section 129. In the present embodiment, since ch (c) and ch (d) are both radio communication channels of 2.4GHz, ch (a) timing generation section 111 may be used to generate various control timings for ch (c) and ch (d).
When transmitting the CTS frame transmission instruction to the CTS frame transmission control unit 124, the channel selection control unit 123 in fig. 3 notifies the electric field strength measurement control unit 128 of the channel number of the channel to be switched when the channel is the channel to be monitored (or the channel to be monitored and the channel to be communicated), and issues an instruction to start monitoring. The electric field strength measurement control unit 128, which is instructed to start monitoring, measures the electric field strength by the electric field strength measurement means 127, and stores the measurement result in the measurement result storage means 129. The operation manager of the wireless relay device 1B can check whether or not there is a wireless communication channel in a better radio wave situation by referring to the measurement results stored in the measurement result storage unit 129, and can check whether or not the communication destination channel can be changed to the wireless communication channel when there is a wireless communication channel in a better radio wave situation.
The above is the configuration of the radio relay apparatus 1B.
As described above, in the radio relay apparatus 1B according to the present embodiment, the communication target channel and the monitoring target channel are cyclically selected, communication with the radio terminal apparatus is performed using the communication target channel while the communication target channel is selected, and the electric field intensity is measured with respect to the monitoring target channel while the monitoring target channel is selected. While all communications of the wireless terminal apparatuses accommodated in the wireless relay apparatus 1B are prohibited during the selection of the channel to be monitored, if the channel to be monitored is not selected continuously or the frequency of selection of the channel to be monitored is suppressed to be lower than the frequency of selection of the channel to be communicated per unit time, the usage state of the channel to be monitored can be measured during the operation of the wireless relay apparatus 1B without significantly degrading the convenience of the wireless LAN.
In the present embodiment, ch (a) belonging to the 2.4GHz band is used as a communication target channel, and ch (c) and ch (d) belonging to the 2.4GHz band are used as monitoring target channels. However, similarly to embodiment 1, ch (a) belonging to the 2.4GHz band and ch (b) belonging to the 5GHz band may be set as communication target channels, and both data communication with the wireless terminal apparatus and monitoring of the electric field intensity may be performed on one channel, and only data communication with the wireless terminal apparatus may be performed on the other channel. For example, when both data communication and monitoring of electric field strength are performed for ch (a) and only data communication with the radio terminal apparatus is performed for ch (b), as shown in fig. 4, channel switching may be performed such that data communication via ch (a) → data communication via ch (b) → monitoring of electric field strength of ch (a) → data communication via ch (a). In this case, the channel switching may be performed such that data communication via ch (a) → monitoring of the electric field strength of ch (b) → data communication via ch (a). Further, ch (a) belonging to the 2.4GHz band and ch (b) belonging to the 5GHz band may be used only for data communication as communication target channels, and ch (c) belonging to the 2.4GHz band may be used only for monitoring the electric field intensity as a monitoring target channel. In this case, as shown in fig. 5, channel switching may be performed such that data communication via ch (a) → data communication via ch (b) → monitoring of the electric field strength of ch (c) → data communication via ch (a). The key point is that each of the plurality of wireless communication channels is cyclically selected, communication is performed with the wireless terminal apparatus via at least 1 of the selected wireless communication channels, and at least one of communication via the selected wireless communication channel and measurement of the radio wave state of the selected wireless communication channel is performed.
Further, whether to use for data communication or to measure the electric field strength may be predetermined for each frequency band. For example, there are cases where: a channel (for example, ch (a)) belonging to the 2.4GHz band is used for data communication as a communication target channel, and only the electric field intensity is measured for a channel (for example, ch (b)) belonging to the 5GHz band. According to this method, for example, although the 2.4GHz band is used in the current wireless LAN, when a shift to the 5GHz band is considered in the future, the wireless LAN can be operated, the radio wave condition of the 5GHz band can be grasped, and reference can be made to the determination of whether the shift is possible and the selection of a channel to be used in the 5GHz band to be shifted.
(C: embodiment 3)
Next, embodiment 3 of the present invention is performed.
Fig. 6 is a diagram showing a configuration example of the radio relay apparatus 1C according to the present embodiment. In fig. 6, the same components as those in fig. 1 are denoted by the same reference numerals. As is clear from comparison between fig. 6 and fig. 1, the configuration of the radio relay apparatus 1C differs from that of the radio relay apparatus 1A in that the channel load factor measurement unit 131 is provided. A radio relay apparatus 1C in fig. 6 is the same as the radio relay apparatus 1A in embodiment 1 in that one of a plurality of radio communication channels (ch (a) and ch (b) in the present embodiment) is cyclically selected to perform data communication with a radio terminal apparatus. However, the wireless relay apparatus 1C is different from the wireless relay apparatus 1A in that: during a period in which each channel is selected (hereinafter referred to as a selection period), the load factor of the wireless communication channel is measured by the channel load factor measuring unit 131, and the length of the selection period for the channel (in other words, a channel switching cycle) is dynamically changed based on the channel load factor of each wireless communication channel at each timing of channel switching.
To describe in more detail, the modulation/coding unit 126 in the wireless relay device 1C according to the present embodiment notifies the channel load factor measuring unit 131 of the internal signal indicating the transmission frame each time the internal signal is transmitted to the RF selecting unit 105. Similarly, when the carrier signal obtained by analyzing the received signal is transmitted to the demodulation and decoding unit 106, the carrier signal detection unit 130 notifies the channel load factor measurement unit 131 that the carrier signal has been detected. The channel load factor measuring section 131 measures the time after the transmission of the communication frame when the notification is received from the modulation/coding section 126. The channel load factor measuring unit 131 measures the time after the reception of the carrier signal is detected, in response to the notification from the carrier signal detecting unit 130. The channel load factor measuring unit 131 notifies the channel selection control unit 123 of the ratio of the sum of the time after the transmission of the communication frame and the time after the detection of the received carrier signal to the channel selection period of the channel as the channel load factor of the wireless communication channel selected at that time. The channel selection control unit 123 writes the channel load factor notified from the channel load factor measurement unit 131 into a ring buffer provided for each channel (for example, a ring buffer storing the channel load factors of the latest 5 selection periods: not shown in fig. 6).
The channel selection controller 123 of the radio relay apparatus 1A alternately switches ch (a) and ch (b) (that is, the length of the selection period of each of ch (a) and ch (b) is fixed, and the length thereof is 50ms) at 50ms intervals. On the other hand, the channel selection control unit 123 of the radio relay apparatus 1C basically alternately switches ch (a) and ch (b) at 50ms intervals, but determines whether or not the selection period of each channel needs to be changed based on the channel load rate notified from the channel load rate measurement unit 131 at each timing of channel switching and the channel load rate stored in the ring buffer for each channel, and dynamically changes the period when it is determined that the change is necessary. To describe this in more detail, the channel selection control unit 123 of the radio relay apparatus 1C determines the selection period of each channel according to the flowchart shown in fig. 7.
As shown in fig. 7, the channel selection control unit 123 of the radio relay apparatus 1C first acquires the channel load rate notified from the channel load rate measurement unit 131 (step SA100), compares the channel load rate of ch (a) with the channel load rate of ch (b) in the immediately preceding selection period (i.e., the immediately preceding selection period of ch (b)), and determines whether or not the former is 2 times or more the latter (step SA 110). If the determination result in step SA110 is yes, the channel selection control unit 123 further determines whether or not the state in which the channel loading rates are all equal to or greater than 2 times the channel loading rate of ch (b) continues in the last 5 selection periods for ch (a) (step SA 120). If the determination result in step SA120 is yes, the channel selection controller 123 multiplies the selection period for ch (a) by 1.2 and multiplies the selection period for ch (b) by 0.8 (step SA 130). Conversely, if the determination result in step SA120 is "no", the channel selection control unit 123 returns the selection period of each channel to the initial value (for example, 50ms) and ends the processing.
On the other hand, if the determination result in step SA110 is "no", the channel selection control unit 123 of the radio relay apparatus 1C determines whether or not the channel load factor of ch (b) is greater than or equal to 2 times the channel load factor of ch (a) (step SA 140). If the determination result in step SA140 is yes, the channel selection control unit 123 further determines whether or not the state in which the channel load rate is 2 times or more the channel load rate of ch (a) continues for ch (b) in the last 5 selection periods (step SA150), and if the determination result is yes, sets the selection period of ch (b) to 1.2 times and the selection period of ch (a) to 0.8 times (step SA 160). On the contrary, if the determination result in step SA150 is "no", the channel selection control unit 123 returns the selection period of each channel to the initial value (50ms) and ends the processing.
That is, in the present embodiment, when the ratio of the load ratios between the channels is 2 times or more and the state continues for the most recent 5 selection periods for the more heavily loaded channel, the selection period for the less heavily loaded channel is reduced to 80%, and instead the selection period for the more heavily loaded channel is increased to 120%, and this process is repeatedly executed until the ratio of the load ratios is less than 2 times. For example, if the channel switching cycle is 50ms, if the state in which the load factor of ch (a) is 20% or more and the load factor of ch (b) is less than 10% continues in the last 5 selection periods for ch (a), the process of changing the selection period of each channel is performed until the ratio of the load factors of the two channels is less than 2 times. That is, the selection period of ch (a) is 50ms × 1.2 to 60ms, and the selection period of ch (b) is 50ms × 0.8 to 40 ms. As a result, as shown in fig. 8, the communication prohibition period of the CTS is 50ms obtained by adding the selection period 40ms of the CTS to the guard time 10ms of the ch (b) for ch (a), and is 70ms for ch (b).
As described above, according to the wireless relay device 1C of the present embodiment, the following effects can be obtained in addition to the same effects as those of embodiment 1: by shortening the selection period of a radio communication channel with a low channel load factor (i.e., a radio communication channel with a low usage rate) and conversely, by lengthening the selection period of a radio communication channel with a high channel load factor (i.e., a radio communication channel with a high usage rate), each radio communication channel can be used more efficiently.
(D: embodiment 4)
Fig. 9 is a diagram showing a configuration example of a wireless relay device 1D according to embodiment 4 of the present invention. In fig. 9, the same components as those in fig. 3 are denoted by the same reference numerals. As is clear from comparison between fig. 9 and fig. 3, the configuration of the radio relay apparatus 1D is different from that of the radio relay apparatus 1B in that ch (a) frame error rate storage section 132, ch (B) frame error rate storage section 133, monitoring result reflection section 134, monitoring result reflection timing generation section 135, and communication speed switching mode storage section 136 are provided.
In the wireless relay device 1D, the demodulation/decoding unit 106 checks the accuracy of the MAC frame when extracting the MAC frame from the received signal. More specifically, the demodulation/decoding unit 106 calculates a CRC value with reference to the payload portion of the received frame, and determines whether or not the CRC value matches the CRC value stored in the CRC field in the header portion of the received frame. When the CRC values do not match, the demodulation/decoding unit 106 discards the frame as a frame including error data. The demodulation/decoding unit 106 calculates the ratio of the number of frames in which a CRC error (i.e., the above-described inconsistency of the CRC value) is detected to the number of received frames for each wireless communication channel, and outputs the calculated ratio as the frame error rate of each wireless communication channel. The frame error rates of ch (a) are saved in ch (a) frame error rate saving unit 132, and the frame error rates of ch (b) are saved in ch (b) frame error rate saving unit 133.
The monitoring result reflection timing generation unit 135 generates a basic timing (for example, a timing of 1 time in 1 hour) for reflecting a periodic electric field strength monitoring result to a communication parameter (a wireless communication channel, a switching pattern of a communication speed, and a transmission power). The monitoring result reflection unit 134 is started at this basic timing, and the reflection of the monitoring result on the communication parameter is realized. The monitoring result reflecting unit 134 performs adjustment for further improving the communication condition based on the periodic electric field strength monitoring result. Hereinafter, similarly to embodiment 2, a case where an attempt is made to improve the communication situation in the 2.4GHz band will be described by taking, as an example, a case where ch (a) belonging to the 2.4GHz band is a channel to be communicated and ch (c) and ch (d) are channels to be monitored.
Fig. 10 is a flowchart showing the flow of the monitoring result reflection processing executed by the monitoring result reflection unit 134. As shown in fig. 10, the monitoring result reflection unit 134 first determines whether or not radio waves from other than the self BSS are detected in the communication target channel (ch (a) in the present embodiment) (step SB 100). If the determination result in step SB100 is "no", the monitoring result reflection unit 134 immediately ends the monitoring result reflection processing. This is because if a radio wave from a BSS other than the own BSS is not detected (i.e., there is no interference), it is not necessary to improve the communication condition. On the other hand, if the determination result in step SB100 is yes, the monitoring result reflection unit 134 determines whether ch (c) is an idle channel (step SB 110). To describe in more detail, if the monitoring result reflection unit 134 does not detect other radio waves in the monitoring result for ch (c) for the past 24 hours, it determines that ch (c) is an idle channel.
If the determination result at step SB110 is yes, the monitoring result reflection unit 134 changes the communication destination channel to ch (c) (step SB120), and ends the monitoring result reflection process. When the channel to be communicated is changed, the monitoring result reflecting unit 134 clears the authentication list of ch (a) in the same 2.4GHz band and instructs the channel selection control unit 123 to change the channel. If the determination result in step SB110 is "no", the monitoring result reflection unit 134 determines whether ch (d) is an idle channel (step SB 130). If the determination result in step SB130 is yes, the monitoring result reflection unit 134 changes the communication destination channel to ch (d) (step SB140), and ends the monitoring result reflection process. If the determination result at step SB130 is "no", the monitoring result reflection unit 134 executes the processing at step SB150 and beyond.
In step SB150 executed when the determination result in step SB130 is "no" (that is, when neither ch (c) nor ch (d) is an idle channel), the monitoring result reflection unit 134 acquires the frame error rate from the ch (a) frame error rate storage unit 132, and determines whether or not the frame error rate is greater than or equal to a predetermined threshold value. The reason for determining whether the frame error rate is equal to or higher than the predetermined threshold value is as follows. When the interference source is also an IEEE802.11 wireless LAN and the radio wave of the other party arrives at a sufficient intensity, the interference sources operate according to CSMA/CA, and therefore the communication speed is reduced, but the frame error rate is also reduced. On the other hand, when the interference source is not the IEEE802.11 wireless LAN, or when the radio wave of the other party does not arrive at a sufficient intensity even in the IEEE802.11 wireless LAN, collision of the radio wave occurs in the communication medium, and the frame is broken, and the frame error rate increases. That is, in order to determine whether the interference source is an IEEE802.11 wireless LAN and the radio wave of the other party arrives at a sufficient intensity, or whether the interference source is not an IEEE802.11 wireless LAN (or the radio wave of the wireless LAN does not arrive at a sufficient intensity although the interference source is an IEEE802.11 wireless LAN), the frame error rate is compared with a predetermined threshold value.
If the determination result at step SB150 is "no", the monitoring result reflection unit 134 generates a mail notifying that the interference source is the IEEE802.11 wireless LAN and that the radio wave of the other party has arrived with sufficient strength, and transmits the mail to the system administrator by the mail transmission unit 137 (step SB 160). This is because improvement cannot be made in this case by itself. The system administrator who receives the mail may take improvement measures such as reconfiguration of channels including surrounding systems.
On the other hand, if the determination result at step SB150 is yes, the monitoring result reflection unit 134 determines whether or not the currently selected communication speed is the lowest communication speed (step SB170), and if the determination result is no, the modulation and coding unit 126 is instructed to switch the communication speed to a lower communication speed (step SB 180). In general, the communication speed (link speed) on the communication medium is changed as needed in accordance with the communication status, and a high communication speed is selected in a state where the radio wave status is good. In the present embodiment, a plurality of communication speed modes are prepared in advance, and these modes are stored in communication speed switching mode storage section 136. Modulation/coding unit 126 determines the communication speed at the time of modulation based on the communication speed pattern stored in communication speed switching pattern storage section 136. When the determination result at step SB150 is yes, the communication speed is further reduced because the possibility of frame reproduction can be increased even if the radio wave interferes.
If the determination result at step SB170 is "yes" (that is, if the radio wave situation is not improved even if the communication speed is reduced to the extremely low limit), the monitoring result reflection unit 134 determines whether or not the current transmission power reaches the upper limit value (step SB190), and if the determination result is "no", the transmission power is increased (step SB 200). The reason for this is that if the interference source is an IEEE802.11 wireless LAN, it can be expected to cope with CSMA/CA contention control on the interference source side by increasing the transmission power. In addition, when the determination result at step SB190 is yes, since improvement of the monitoring result reflection unit 134 itself cannot be expected, a mail for requesting improvement is transmitted to the system administrator by the mail transmission unit 137 (step SB 210).
As described above, according to the wireless relay device 1D of the present embodiment, when interference is found based on the electric field strength monitoring result of the communication target channel, operations for further improving the communication status, such as switching of the communication target channel and adjustment of the communication parameters, are automatically executed. In the present embodiment, when the frame error rate exceeds the predetermined threshold (when the determination result at step SB150 is yes), first, whether or not the communication speed can be switched is determined (step SB170), and when the communication speed cannot be switched (when the determination result at step SB170 is yes), whether or not the transmission power can be increased is determined (step SB 190). However, when the frame error rate exceeds a predetermined threshold, it may be determined whether or not the transmission power can be increased first, and when the transmission power cannot be increased, it may be determined whether or not the communication speed can be switched (that is, in fig. 10, the steps SB170 and SB190 may be interchanged).
In addition, in the present embodiment, the following processing may be performed: when interference is found (when the determination result at step SB100 is yes), first, a process of attempting to change to the idle channel (the process from step SB110 to step SB140) is performed, but the process from step SB110 to step SB140 may be omitted, and when interference is found, the process at step SB150 is immediately performed. Instead of omitting the processes from step SB110 to step SB140, either one or both of the process of attempting to decrease the communication speed (the processes at step SB170 and SB180) and the process of attempting to increase the transmission power (the processes at step SB190 and SB200) may be omitted. If both the process of attempting to decrease the communication speed and the process of attempting to increase the transmission power are omitted, the processes in SB150 and SB160 can be omitted. In this case, in the case where there is no free channel, the process of sending the mail to the administrator is immediately executed (step SB 210).
(E: modification)
Although the embodiments of the present invention have been described above, it is needless to say that the following modifications can be made to the embodiments.
(1) In the above embodiments, the example in which the present invention is applied to the wireless relay device corresponding to the dual band corresponding to both of the 2.4GHz band and the 5GHz band is described, but it is needless to say that the present invention can be applied to the following wireless relay devices: each of a plurality of radio communication channels within a certain 1 frequency band is cyclically selected, and at least one of measurement of radio wave conditions and communication with a radio terminal apparatus using radio waves of the radio communication channel is performed for each of the selected radio communication channels. In addition, the present invention can be applied to a wireless relay apparatus corresponding to a frequency band greater than or equal to 3. This is because 2 types of frequency bands of communication waves of the wireless LAN currently exist, namely, 2.4GHz band and 5GHz band, but other frequency bands may be used in the future. In the above embodiments, an example in which the present invention is applied to a wireless relay device that houses a wireless terminal device and functions as a switching hub has been described. However, the present invention can be applied to a wireless relay apparatus that houses a wireless terminal apparatus and functions as a router, and in this case, an IP address may be used instead of a MAC address as a terminal identifier for identifying the wireless terminal apparatus.
(2) In each of the above embodiments, an instruction to prohibit communication for a predetermined period (that is, until the wireless communication channel is selected next) is issued to the wireless terminal apparatus that transmits the CTS message at the time of channel switching and performs communication using the wireless communication channel before switching, but a new message (for example, an application layer message) that performs the same function as the CTS message may be defined, and the wireless relay apparatuses 1A, 1B, 1C, and 1D may be caused to broadcast the new message instead of transmitting the CTS message. In addition, the following effects are exhibited: by performing the above-described communication prohibition, it is avoided that the wireless terminal apparatus performs unnecessary data transmission while the wireless communication channel for performing communication with the wireless terminal apparatus is not selected, but the communication prohibition (that is, transmission of the CTS message) as described above may not be performed when there is no problem of unnecessary data transmission.
(3) In the above embodiments, the following cases are explained: when a frame addressed to a wireless terminal device using another wireless communication channel is transmitted while the wireless communication channel is selected, the frame is stored in a queue and transmitted to the wireless terminal device when the wireless communication channel is selected again. However, if the communication performed by each wireless terminal apparatus is a communication that does not require saving of the state, such as browsing a Web page, it is not necessary to perform the queue waiting as described above.
(4) In each of the above embodiments, the selection means and the communication control means are respectively configured by hardware, wherein the selection means cyclically selects each of the plurality of wireless communication channels (the RF selection unit 105, the channel switching timing generation unit 122, and the channel selection control unit 123 in each embodiment), the communication control means communicates with the wireless terminal apparatus via at least 1 of the wireless communication channels selected by the selection means, and performs at least one of communication via the channel and measurement of radio wave state of the channel for each of the wireless communication channels selected by the selection means (the transmission frame selection unit 121 and the CTS frame transmission control unit 124 in embodiments 1 and 3 (in addition, if the transmission of the CTS frame is not performed, the CTS frame transmission control unit 124 is not required), and the electric field strength measurement means 127, the electric field strength measurement means, and the electric field strength measurement means are further included in embodiments 2 and 4, Electric field strength measurement control unit 128 and measurement result storage section 129), and the wireless relay apparatus according to each of the above embodiments is realized by combining these hardware components. However, a program may be provided that executes, on a computer, a communication control method including: a step of cyclically selecting each of a plurality of wireless communication channels; and communicating with the wireless terminal apparatus via at least 1 of the selected wireless communication channels, and performing at least one of communication via the selected wireless communication channel and measurement of a radio wave state of the selected wireless communication channel. As a method of providing such a program, a method of distributing the program by writing the program in a computer-readable recording medium such as a CD-ROM or a method of distributing the program by downloading the program through an electric communication line such as the internet can be considered.
Description of reference numerals:
1A, 1B, 1C, 1D … wireless relay device
101. 102 … antenna
103 … 2.4G band RF part
104 … 5GHz band RF section
105 … RF selection part
106 … demodulation/decoding unit
107 … frame distributing part
108 … Wireless control part
109 … CH (A) control information storage unit
110 … CH (B) control information holding unit
111 … CH (A) timing generation unit
112 … CH (B) timing generation unit
113 … authentication unit
114 … CH (A) authentication List
115 … CH (B) authentication List
116 … bridge function
117 … data frame queue selection part
118 … CH (A) data frame queue
119 … CH (B) data frame queue
120 … control frame queue
121 … Transmission frame selection part
122 … channel switching timing generating unit
123 … channel selection control part
124 … CTS frame transmission control part
125 … selecting channel holding unit
126 … modulation and coding part
127 … electric field strength measuring unit
128 … electric field strength measurement control part
129 … measurement result storage means
130 … carrier signal detection unit
131 … channel load rate measuring part
132 … CH (A) frame error rate storage unit
133 … CH (B) FRAME ERROR STORAGE UNIT
134 … monitoring result reflection unit
135 … monitoring result reflection timing generation unit
136 … communication speed switching mode holding unit
137 … mail sending unit

Claims (14)

1. A wireless relay device of a wireless LAN according to IEEE802.11 standard, comprising:
a selection unit that cyclically selects each of a plurality of wireless communication channels; and
a communication control unit that communicates with the wireless terminal apparatus via at least one of the wireless communication channels selected by the selection unit and performs at least one of communication via the channel and measurement of a radio wave state of the channel for each of the wireless communication channels selected by the selection unit,
the selection unit selects each of the plurality of wireless communication channels in such a manner that a wireless communication channel that performs only measurement of an electric wave state is discontinuously selected among the plurality of wireless communication channels.
2. A wireless relay device of a wireless LAN according to IEEE802.11 standard, comprising:
a selection unit that cyclically selects each of a plurality of wireless communication channels; and
a communication control unit that communicates with the wireless terminal apparatus via at least one of the wireless communication channels selected by the selection unit and performs at least one of communication via the channel and measurement of a radio wave state of the channel for each of the wireless communication channels selected by the selection unit,
the selection means suppresses a selection frequency per unit time of a wireless communication channel, which performs only measurement of a radio wave state, of the plurality of wireless communication channels to be lower than a selection frequency per unit time of a wireless communication channel which performs communication via the channel.
3. The wireless relay according to claim 1 or 2,
the plurality of wireless communication channels include more wireless communication channels for communication with the wireless terminal device than wireless communication channels for which only the measurement of the radio wave state is performed.
4. The wireless relay according to claim 1 or 2,
the communication control unit performs communication with a wireless terminal device corresponding to each frequency band in a plurality of wireless communication channels belonging to a certain frequency band of a plurality of frequency bands different from each other.
5. The wireless relay according to claim 1 or 2,
the communication control unit may measure only a radio wave state of a radio communication channel belonging to a predetermined frequency band among the plurality of radio communication channels, the radio communication channel belonging to each of the plurality of different frequency bands.
6. The wireless relay according to claim 1 or 2,
the wireless communication system further includes a monitoring result reflecting unit that determines whether or not interference is present in a wireless communication channel used for communication with the wireless terminal device among the plurality of wireless communication channels, and if it is determined that interference is present, changes any one of a wireless communication channel, a communication speed, and a transmission power used for communication with the wireless terminal device.
7. The wireless relay according to claim 1 or 2,
the communication control unit instructs a wireless terminal device, which is communicating using radio waves of a wireless communication channel before switching, to prohibit a start of new communication until the wireless communication channel is selected next time.
8. A wireless relay method of a wireless relay device of a wireless LAN in IEEE802.11 standard,
each of the plurality of wireless communication channels is selected on a round-robin basis,
communicating with a wireless terminal apparatus via at least one of the cyclically selected wireless communication channels, and performing at least one of communication via the channel and measurement of a radio wave state of the channel for each of the cyclically selected wireless communication channels,
each of the plurality of wireless communication channels is selected in such a manner that a wireless communication channel that performs only measurement of the electric wave state is discontinuously selected among the plurality of wireless communication channels.
9. A wireless relay method of a wireless relay device of a wireless LAN in IEEE802.11 standard,
each of the plurality of wireless communication channels is selected on a round-robin basis,
communicating with a wireless terminal apparatus via at least one of the cyclically selected wireless communication channels, and performing at least one of communication via the channel and measurement of a radio wave state of the channel for each of the cyclically selected wireless communication channels,
the selection frequency per unit time of a wireless communication channel, which is only measured for radio wave conditions, among the plurality of wireless communication channels is suppressed to be lower than the selection frequency per unit time of a wireless communication channel which performs communication via the channel.
10. The wireless relay method according to claim 8 or 9,
the plurality of wireless communication channels include more wireless communication channels for communication with the wireless terminal device than wireless communication channels for which only the measurement of the radio wave state is performed.
11. The wireless relay method according to claim 8 or 9,
communication with a wireless terminal device corresponding to each frequency band is performed in a plurality of wireless communication channels belonging to a certain frequency band among a plurality of frequency bands different from each other.
12. The wireless relay method according to claim 8 or 9,
each of the plurality of wireless communication channels belongs to one of a plurality of different frequency bands, and only the radio wave state of the wireless communication channel belonging to a predetermined frequency band among the plurality of wireless communication channels is measured.
13. The wireless relay method according to claim 8 or 9,
the method includes determining whether or not interference exists in a wireless communication channel used for communication with a wireless terminal device among the plurality of wireless communication channels, and if it is determined that interference exists, changing any one of a wireless communication channel, a communication speed, and a transmission power used for communication with the wireless terminal device.
14. The wireless relay method according to claim 8 or 9,
a wireless terminal device, which is communicating using a radio wave of a wireless communication channel before switching a wireless communication channel, issues an instruction to prohibit a start of new communication until the wireless communication channel is selected next time.
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