JP2012129889A - Communication apparatus, control method of the same and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a packet loss and a possibility that a communication apparatus leaves a network which are generated by a dual terminal scanning an overlapping basic service set (OBSS).SOLUTION: A communication apparatus which participates in a first network built by a base station and builds a second network requests other communication apparatus which participates in a second network to search a network which does not make communication in a plurality of frequency channels, receives the search result of the network which does not make communication in the plurality of frequency channels from other communication apparatus corresponding to the request, and transmits the received search result to the base station.

Description

  The present invention relates to a communication device that requests a network search.

  In recent years, a wireless LAN (Local Area Network) system represented by IEEE (Institut of Electrical and Electronics Engineers) 802.11 has been widely used. In a wireless LAN, a network is constructed by base stations called access points (hereinafter referred to as APs). A network is configured by this AP and a station (hereinafter referred to as STA) that exists in the radio wave reach of the AP and is in a wireless connection state.

  Furthermore, a Dual terminal that has both an AP function for performing communication as a base station and an STA function for performing communication by connecting to the AP has appeared. Such a device can construct a network as an AP and can participate as a STA in a network constructed by another AP. When such a Dual terminal has only one antenna, it is desirable that the channel of the network constructed as the AP and the channel of the network participating as the STA are the same. This is because it is necessary to switch between the channels used by the AP and the STA for switching, and it is difficult to eliminate the packet loss that occurs when the channels are switched.

  On the other hand, IEEE802.11n standard devices designed to increase the speed of wireless LAN are being widely used. IEEE802.11n supports not only the conventional 20 MHz frequency channel band but also a 40 MHz channel mode using a double frequency channel band for speeding up. However, in the 40 MHz channel mode, a conventional wireless device that does not support IEEE802.11n may not be able to perform carrier sense and frame collisions may occur frequently.

  For this reason, IEEE 802.11n defines OBSS (Overlapping Basic Service Set) Scan. In OBSS Scan, STAs operating in the 40 MHz channel mode periodically search for surrounding networks. Then, when discovering surrounding networks that do not support the 11n standard and networks that do not allow the surrounding network to use the 40 MHz channel mode, the STA has found these networks with respect to the AP of the participating network. Notify that.

JP 2003-348095 A

  However, while the dual terminal is executing OBSS Scan, the dual terminal cannot receive packets from the STA. Therefore, packet loss may occur. Further, since the Dual terminal does not transmit a beacon while the Dual terminal is executing the OBSS Scan, the STA may misrecognize that the network has disappeared and may leave the network.

  An object of the present invention is to reduce packet loss that occurs due to the above-described reason and the possibility that a communication device will leave a network.

  The communication device of the present invention participates in the first network constructed by the base station and also constructs the second network, and other communication devices participating in the second network Searching for a network that does not perform communication on a plurality of frequency channels from requesting means for requesting to search for a network that does not perform communication on a plurality of frequency channels, and the other communication device in response to the request by the requesting unit Receiving means for receiving the result; and transmitting means for transmitting the search result received by the receiving means to the base station.

  According to the present invention, it is possible to reduce the possibility of packet loss and the communication device leaving the network.

Diagram showing network configuration Hardware configuration diagram Software function block diagram flowchart Sequence chart Sequence chart Sequence chart

  FIG. 1 shows a network configuration of a wireless communication system according to the present embodiment. The network 101 is an infrastructure network that conforms to the IEEE 802.11n standard (hereinafter, 11n standard) in which the AP 102 and the dual terminal 103 participate. Here, AP is an abbreviation for an access point, and is a base station that constructs the network 101. The dual terminal is a communication apparatus that can execute an AP function for constructing a network and an STA (station) function for participating in the network in parallel.

  The AP 102 communicates with the STA in the mode (20 MHz channel mode) communicating using the 20 MHz band using the 20 MHz band, and uses the 40 MHz band with the STA in the mode communicated using the 40 MHz band (40 MHz channel mode). connect. In this execution mode, the dual terminal 103 participates in the network 101 as a STA in the 40 MHz channel mode.

  In addition, the AP 102 requests a 40 MHz mode STA participating in the network 101 to periodically execute an OBSS (Overlapping Basic Service Set) Scan compliant with the 11n standard. An execution request for OBSS Scan is made by adding an OBSS Scan Parameters Element compliant with the 11n standard to a notification signal (beacon) or a search response (probe response).

  Here, the OBSS Scan is a search for a network that does not support the 11n standard in the surroundings or a network that does not allow the surrounding network to use the 40 MHz channel mode. When the STA in the 40 MHz mode detects such a network, it notifies this to the AP constructing the network. The STA notifies this by transmitting a 20/40 BSS Coexistence Management Frame compliant with the 11n standard to the AP.

  Further, when the dual terminal 103 connects to the AP 102, it periodically executes the OBSS Scan and notifies the AP 102 to notify the AP 102 of the result. This is done in a predetermined manner in accordance with the 11n standard for connection requests.

  The network 104 is a network constructed by the dual terminal 103 operating as an AP. In the present embodiment, the frequency channel used in the network 101 and the frequency channel used in the network 104 are the same. STA 105 and STA 106 participate in this network 104.

  FIG. 2 shows a hardware configuration of the dual terminal 103. The control unit 201 includes a CPU and an MPU, and controls the entire camera 101 by executing a program stored in the storage unit 202.

  The storage unit 202 includes a ROM and a RAM, and stores various information such as a program executed by the control unit 201 and communication parameters. Various operations to be described later are performed by the control unit 201 executing a program stored in the storage unit 202. The storage unit 202 stores not only memories such as ROM and RAM, but also flexible disks, hard disks, optical disks, magneto-optical disks, CD-ROMs, CD-Rs, magnetic tapes, nonvolatile memory cards, DVDs, and the like. A medium may be used. A user interface unit 203 (hereinafter referred to as a user I / F) displays various information and accepts various operations from the user. Reference numeral 204 denotes a communication unit.

  FIG. 3 shows software function blocks that are realized when the control unit 201 of the dual terminal 103 reads a program stored in the storage unit 202. Note that at least a part of the software functional blocks shown in FIG. 3 may be realized by hardware.

  The AP function unit 301 has a function for the dual terminal 103 to operate as an AP that conforms to the 11n standard. This includes a function for the Dual terminal 103 to construct the network 104 and a function for confirming the presence or absence of STAs participating in the network 104. Also included is a function for inquiring whether an STA participating in the network 104 can execute the OBSS Scan.

  The STA function unit 302 has a function for the dual terminal 103 to perform a STA operation conforming to the 11n standard. This includes a function in which the Dual terminal 103 participates in the network 101 constructed by the AP 102 and a function to perform OBSS Scan.

  The determination unit 303 determines a method for searching for the presence / absence of a network that does not support the 11n standard in the vicinity and the presence / absence of a network that does not allow the 40 MHz channel mode in the surrounding network.

  The absence unit 304 notifies the STAs participating in the network 104 that the dual terminal 103 is temporarily absent from the network 104. Specifically, the dual terminal 103 transmits a channel absence notification frame that conforms to the 11n standard, thereby notifying that the network 104 is temporarily absent. The channel absence notification frame includes information on a period during which the dual terminal 103 is absent. As a result, the STA participating in the network 104 knows that the dual terminal 103 is temporarily absent, and therefore can prevent packet loss and erroneous recognition that the STA has disappeared from the network 104.

  The absence unit 304 also determines whether STAs participating in the network 104 can correctly process the STA when receiving a channel absence notification frame that conforms to the 11n standard. Specifically, the absence unit 304 determines this by notifying the Dual terminal 103 that the STA can correctly process the channel absence notification frame at the time of connection. However, the present invention is not limited to this, and this may be determined by a response from the STA to the channel absence notification frame transmitted by the absent unit 304.

  FIG. 4 shows a flowchart realized when the control unit 201 in 101 reads out a program stored in the storage unit 202. This flowchart is periodically executed by the dual terminal 103.

  In step S401 (hereinafter abbreviated as “step”), the AP function unit 301 confirms the presence or absence of STAs participating in the network 104. If it is confirmed that there is a STA participating in the network 104, the process proceeds to S402. If it is confirmed that there is no STA, the process proceeds to S405.

  In S405, the determination unit 303 determines that the Dual terminal 103 itself performs OBSS Scan to search for a network that does not support the surrounding 11n standard and a network that does not allow the surrounding network to use the 40 MHz channel mode. . A sequence chart in this case is shown in FIG.

  First, the STA function unit 302 of the dual terminal 103 executes OBSS Scan and searches for the presence or absence of a network that does not support the 11n standard in the box and the presence or absence of a network that does not allow the surrounding network to use the 40 MHz channel mode ( S501). Specifically, it is performed by acquiring 20/40 BSS Coexistence information from each STA participating in the surrounding network. At this time, even if the OBSS Scan is executed, there is no STA participating in the network 104, and therefore no packet loss occurs.

  In step S502, the STA function unit 302 notifies the AP 101 of the search result in step S501. Specifically, it is performed by transmitting a 20/40 BSS Coexistence Management frame based on the 11n standard to the AP 102. In this way, the dual terminal 103 can notify the AP 102 of the presence or absence of a network that does not support the surrounding 11n standard and the presence or absence of a network that does not allow the surrounding network to use the 40 MHz channel mode.

  Returning to the description of FIG. In S <b> 402, the STA function unit 302 inquires whether there is an STA that can execute the OBSS Scan in the network 104. As a result of the inquiry, if it is determined that there is at least one STA that can execute the OBSS Scan, the process proceeds to S406. If it is determined that no such STA exists, the process proceeds to S403. In S406, the determination unit 303 determines that the STA that can execute the OBSS Scan performs the OBSS Scan. The Dual terminal 103 notifies the AP 102 of the result of the OBSS Scan executed by the STA. A sequence chart in this case is shown in FIG. Here, it is assumed that the STA 105 performs OBSS Scan.

  First, the Dual terminal 103 requests the STA 105 to perform OBSS Scan when connecting to the STA 105 (S601). Next, the STA 105 executes OBSS Scan (S602). Then, the STA 105 notifies the dual terminal 103 of the execution result of the OBSS Scan (S603). Specifically, the STA 105 notifies the execution result of the OBSS Scan by transmitting a 20/40 BSS Coexistence Management frame to the Dual terminal 103.

  Next, the Dual terminal 103 notifies the AP 102 of the execution result of the OBSS Scan received from the STA 105 (S604). Specifically, the dual terminal 103 performs the 20/40 BSS Coexistence Management frame received from the STA 105 by transferring it to the AP 102.

  In this way, the dual terminal 103 can notify the AP 102 of the presence or absence of a network that does not support the surrounding 11n standard and the presence or absence of a network that does not allow the surrounding network to use the 40 MHz channel mode. Further, since the Dual terminal 103 does not execute the OBSS Scan, it is possible to prevent packet loss and the network 104 from disappearing.

  Returning to the description of FIG. In step S403, the absence unit 304 determines whether all STAs participating in the network 104 can correctly process the channel absence notification frame that conforms to the 11n standard. If it is determined that all STAs can correctly process the channel absence notification frame, the process proceeds to S407. If it is determined that at least one STA cannot correctly process the channel absence notification frame, the process proceeds to S404.

  In S404, the determination unit 303 determines not to execute the OBSS Scan. Therefore, the STA function unit 302 reconnects to the AP 102 as an STA that cannot execute the OBSS Scan. In S407, the determination unit 303 determines that the Dual terminal 103 executes the OBSS Scan after transmitting the channel absence notification frame. A sequence chart in this case is shown in FIG.

  First, the Dual terminal 103 transmits (broadcasts) a channel absence notification frame to all STAs participating in the network 104 (S701). This channel absence notification frame includes information on the time required for the OBSS Scan as the time when the channel 104 is absent. The STA that has received the frame temporarily stops transmission of the packet to the dual terminal 103 during that time. Furthermore, even if a control signal such as a beacon cannot be received from the dual terminal 103 during that time, the STA does not recognize that the network 104 has disappeared and does not leave the network 104.

  Thereafter, the Dual terminal 103 performs OBSS Scan (S702). As described above, while the OBSS Scan is being performed, the STA temporarily stops transmitting packets and continues to participate in the network 104. Then, the Dual terminal 103 notifies the AP 102 of the result of OBSS Scan (S703).

  After the elapse of the time included in the channel absence notification frame information, the STA can transmit a packet, and can receive a beacon transmitted from the AP / STA Dual 103.

  As described above, the execution method of the OBSS Scan can be switched according to the capabilities of other communication apparatuses participating in the network. Further, it is possible to prevent packet loss caused by the communication device executing the OBSS Scan and disconnection of other communication devices from the network.

101 Network constructed by AP 102 102 AP
103 Dual terminal 104 Network constructed by Dual terminal 103 105 STA participating in network 104
106 STA participating in network 104

Claims (9)

A communication device that participates in a first network constructed by a base station and constructs a second network,
Request means for requesting other communication devices participating in the second network to search for a network that does not perform communication using a plurality of frequency channels;
Receiving means for receiving a search result of a network that does not perform communication on a plurality of frequency channels from the other communication device in response to the request by the request means;
Transmitting means for transmitting the search result received by the receiving means to the base station;
A communication apparatus comprising: A search means for searching for a network that does not perform communication on a plurality of frequency channels;
The communication apparatus according to claim 1, wherein the transmission unit transmits a search result obtained by the search unit to the base station. Obtaining means for obtaining function information of the other communication device;
Based on the function information acquired by the acquisition means, the transmission means transmits the search result searched by the search means to the base station or received from the other communication device according to the request by the request means Switching means for switching whether the transmission means transmits the search result to the base station;
The communication device according to claim 2, further comprising: First notification means for notifying the other communication device that the communication device is temporarily absent from the second network;
The communication apparatus according to claim 2, wherein a search by the search unit is performed after the notification by the first notification unit. The first notification means further notifies the time information when the communication device is absent from the second network,
The communication device according to claim 4, wherein the search unit searches within the time.   According to the function information acquired by the acquisition means, further comprising a second notification means for notifying the base station that a network that does not communicate with a plurality of frequency channels cannot be searched. The communication apparatus according to any one of claims 3 to 5.   The search for a network that does not perform communication using a plurality of frequency channels is an OBSS (Overlapping Basic Service Set) Scan compliant with IEEE802.11n. Communication device. A method for controlling a communication apparatus that joins a first network constructed by a base station and constructs a second network,
A requesting step for requesting other communication devices participating in the second network to search for a network that does not perform communication on a plurality of frequency channels;
A receiving step of receiving a search result of a network that does not perform communication on a plurality of frequency channels from the other communication device according to the request in the request step;
A transmission step of transmitting the search result received in the reception step to the base station;
A control method characterized by comprising:   The program for operating a computer as a communication apparatus of any one of Claims 1 thru | or 8.

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