KR20100067974A - Channel changing method and apparatus - Google Patents

Abstract

PURPOSE: A channel changing method of an access point and a device thereof are provided to automatically change a channel while detecting a signal interference with the AP, and to determine a wireless communication process with an STA. CONSTITUTION: A wireless communications unit(212) supports wireless communication with a station through a first or a second channel. A control unit(230) receives a wireless signal including a packet through a first channel from A station. The control part measures a retransmission rate of a packet when the intensity of a wireless signal is over a critical value, and determines wireless communications with the station through the second channel of the wireless communication. The control unit determines a second channel by scanning a plurality of the channels supported by an AP(access point).

Description

Channel change method and device {CHANNEL CHANGING METHOD AND APPARATUS}

The present invention relates to a wireless LAN, and more particularly, to a method and apparatus for changing a channel used by a wireless access point (AP) for wireless communication with a station (STA).

The Institute of Electrical and Electronic Engineers (IEEE) 802.11-based wireless local area network (WLAN) may include at least one station (STA) and at least one access point (AP). The AP provides a wireless access service to the STA so that the STA can wirelessly access the Internet through the AP. In order to efficiently utilize the limited radio frequency band (for example, 2.4 GHz or 5 GHz) allocated to the WLAN, the WLAN provides the allocated radio frequency band by dividing it into a plurality of frequency bands, that is, channels. It performs an authentication and association procedure with each STA located in its own area through any one of the channels, establishes an association, and transmits and receives a radio signal with the connected AP. The channel for wireless communication between the AP and the STA determined by the above procedure continues to be used by the AP and the STA until the AP changes it.

However, the conventional channel change method as described above has the following problems. The WLAN may include a plurality of APs, and neighboring APs may each use a channel having the same or adjacent frequency bands. In the above case, when the STA connected to one AP moves to the AP near the area of another AP (hereinafter, referred to as a "neighbor AP"), signal interference due to radio signals from neighboring APs occurs, thereby degrading communication quality. In addition, when a new neighbor AP is installed near the AP or moves the AP near another AP, the above signal interference may occur.To avoid such signal interference, the AP and the STA are currently used by the neighbor AP. The existing channel and other channels whose frequency bands are far from each other should be used, and according to the conventional method, the AP cannot recognize that a signal interference has occurred or change the channel actively. In light of the recent reality of frequent movement, the AP actively detects signal interference and selects a channel with low signal interference. There is a need for a method of automatically inducing a channel change to be used by an STA.

Disclosure of Invention The present invention has been made to solve the above problems, and an object thereof is to provide a method and apparatus for allowing an AP to actively detect a signal interference and automatically change a channel.

According to an aspect of the present invention, a method of changing a channel of an access point (AP) performing wireless communication with an STA (station) is provided. The method includes receiving a wireless signal comprising a packet from a STA over a first channel; Measuring a strength of the received wireless signal and measuring a retransmission rate of the packet if the measured strength of the wireless signal is greater than or equal to a threshold; And determining whether to perform wireless communication with the STA through a second channel different from the first channel based on the measured retransmission rate.

According to another aspect of the present invention, an AP is provided. The AP may include a wireless communication unit supporting wireless communication with a STA through a first channel or a second channel; And receiving a radio signal including a packet from the STA through the first channel of the radio communication unit, and if the strength of the received radio signal is greater than or equal to a threshold value, measures a retransmission rate of the packet, and measures the measured retransmission rate. The control unit may determine whether to wirelessly communicate with the STA through the second channel of the wireless communication unit based on.

According to the present invention as described above, it is possible to provide a method and apparatus for enabling the AP to automatically change the channel by detecting the presence of signal interference.

Reference is now made to the accompanying drawings, which form a part of this specification. In the drawings, like numerals refer to similar constructions unless the context clearly indicates otherwise. The illustrative embodiments described in the detailed description, drawings, and claims are not meant to be limiting. Other embodiments may be utilized, and other changes may be made, without departing from the spirit or scope of the subject matter presented herein. It will be readily understood that the configurations of the present disclosure generally described herein and illustrated in the drawings may be arranged, replaced, or combined in various other configurations, all of which are expressly contemplated, and part of this specification Configure.

1 is a conceptual diagram of a wireless LAN (WLAN) system according to an embodiment of the present invention. Referring to FIG. 1, the WLAN system 100 includes at least one terminal (STA) 110, at least one AP 120 that provides a wireless access service to the STA 110, and an external network, for example. It may include a gateway (GW) 130 that provides a connection with the Internet (not shown). In FIG. 1, three STAs 111-113, two APs 121 and 122, and one router 130 are illustrated for convenience of description, but the WLAN system 100 may include one or more of the above components. These components may be interconnected in a variety of ways.

The STA 110 is a terminal for providing a packet data service such as the Internet to a user. The STA 110 establishes a wireless connection by performing an authentication and association procedure with the AP 120, and performs a wireless signal including a packet through a WLAN. The exchange may be performed through any one of a plurality of channels provided by the system 100. The above authentication and connection procedures are described in detail in the Institute of Electrical and Electronic Engineers (IEEE) 802.11 Recommendations. For convenience of description, the WLAN system 100 provides twelve channels (ie, first to twelfth channels), and the STAs 111 and 113 and the STA 112 respectively represent the area of the AP 121 and 122 (see FIG. 1). It is assumed to be located in the circle shown by the dotted line. The STA 111 and the STA 113 are connected to the AP 121 through a first channel, and the STA 112 is connected to the AP 122 through a second channel located in a frequency band close to the first channel. Assume that it is connected. The AP 121 may use various known multiple access algorithms to wirelessly communicate with the plurality of STAs 111 and 113 through one channel (first channel). In an embodiment, the AP 121 may use a carrier sense multiple access / collision avoidance (CSMA / CA) algorithm.

The AP 121 and the AP 122 are adjacent APs (hereinafter referred to as “neighbor APs”), and when the STA 111 moves to an area overlapping with the area of the AP 122 among the areas of the AP 121. The radio signal between the STA 112 and the AP 122 on the second channel interferes with the radio signal between the STA 111 and the AP 121 on the first channel, thereby communicating between the STA 111 and the AP 121. The quality is degraded. The AP 121 monitors the strength of radio signals received from all STAs located in its own area, including the STA 111, and the retransmission rate of packets included in the above radio signals. If the strength of the received radio signal from at least one STA, for example, the STA 111 is equal to or greater than the first predetermined threshold, and the retransmission rate of the packet included in the radio signal is equal to or greater than the second predetermined threshold, Among the first to twelfth channels, a new channel expected to have the least signal interference may be selected, and information on the selected channel may be provided to STAs located in its own area to perform wireless communication with the selected channel. . Here, the retransmission rate is a packet in which the STA 110 requests the AP 121 for retransmission due to an error in the content of a packet in a radio signal transmitted and received for a predetermined period, and / or the STA 121 transmits the STA 110. A value obtained by dividing the number of packets to be retransmitted by requesting retransmission by the predetermined period.

The retransmission rate of packets that the AP 121 receives from the STAs 111 and 113 may be increased by various factors. For example, when the distance between the STAs 111 and 113 and the AP 121 increases, the strength of the radio signal including the packet received by the AP 121 from the STAs 111 and 113 may be weakened, and thus, the packet may be weakened. The retransmission rate can also be high. In one embodiment, the AP 121 may measure the packet retransmission rate only when the strength of the radio signal is greater than or equal to a predetermined threshold, and may discriminate only when the packet retransmission rate is increased due to signal interference from the neighboring AP 122. You can do that.

In an embodiment, the AP 121 may perform the following operation to select a new channel which is expected to have the least signal interference among the first to twelfth channels. The AP 121 sequentially scans the remaining channels except for the first channel, which is used for wireless communication with the STAs 111 and 113, among the first to twelfth channels provided by the WLAN system 100, and then selects another AP among them. For example, the AP 122 may detect which channel is used and the strength of another AP's radio signal in the corresponding channel, and store the detected information. Later, the AP 121 may use the stored information to select a new channel, which is expected to have the least signal interference among the first to twelfth channels.

FIG. 2 is a detailed block diagram of the AP shown in FIG. 1. Referring to FIG. 2, the AP 121 controls the communication unit 210 to perform wired and wireless communication, the storage unit 220 in which data and operation programs are stored, and the controller 230 to control overall operations of the AP 121. ) May be included.

The communication unit 210 is controlled by the control unit 230 and the wired communication unit 211 and the STA of the WLAN system 100 that support the wired connection with the GW 130 and the like (see FIG. 1) of the WLAN system 100. The wireless communication unit 212 supporting the wireless connection with the 110 and the other AP 122 may be included. The wired communication unit 211 may transmit and receive a packet to and from the GW 130 by wire. The wireless communication unit 212 may transmit and receive a wireless signal with the STAs 111 and 113 through one of channels provided by the WLAN system 100, for example, a first channel. The wireless communication unit 212 may transmit and receive a wireless signal with a neighbor AP of the WLAN system 100, for example, the AP 122, through a channel other than a channel used for transmitting and receiving wireless signals with the STAs 111 and 113. The wireless communication unit 212 may measure the strength of a wireless signal received by the wireless communication unit 212.

The controller 230 scans channels other than the first channel through the wireless communication unit 212 to determine the channels used by each of the neighboring APs and the strength of the wireless signal of the AP using the corresponding channel in each used channel. The scan table may be generated based on the detected information and stored in the storage 220. For each of the first through twelfth channels provided by the WLAN system 100, the scan table indicates whether the corresponding channel is being used by another AP of the WLAN system 100 and a radio signal of the corresponding channel of the other AP using the corresponding channel. It may include at least one of the strength of.

On the other hand, the controller 230 receives a radio signal including a packet from the STA (111, 113) in the region of the AP 121 through the first channel, and if the strength of the received radio signal is greater than or equal to a predetermined first threshold, Measure the retransmission rate of the packet. If the measured retransmission rate is greater than or equal to the second predetermined threshold, the controller 230 determines whether to transmit / receive a radio signal with the STAs 111 and 113 in its own area using another channel instead of the first channel. The controller 230 may retrieve and use information recorded in the scan table in selecting another channel to be used instead of the first channel.

3 is a detailed block diagram of the control unit shown in FIG. 2. Referring to FIG. 3, the controller 230 includes a scan processor 310, a RSS (Received Signal Strength) processor 320, a packet retransmission rate processor 330, and a channel changer 340.

The scan processor 310 is a channel supported by the AP 121 among the channels provided by the WLAN system 100, and is used by the AP 121 to transmit and receive radio signals with the STAs 111 and 113 currently in its own area. The scan signal may be sequentially transmitted through the wireless communication unit 212 for each channel other than the channel (for example, the first channel), and the scan response signal may be received from at least one of the channels transmitting the scan signal. . For example, the AP 122, which is a neighboring AP of the AP 121, may receive a scan signal through a second channel and transmit a scan response signal through the second channel, and the AP 121 may transmit the scan signal. Received to identify that the AP 122 is using the second channel. The scan processor 310 may store identification information indicating a channel for receiving the scan response signal in a scan table. In addition to the above identification information, the scan processing unit 310 may acquire the strength of the scan response signal, that is, RSS through the wireless communication unit 212 and store it in the scan table.

The RSS processor 320 continuously monitors the RSS of the radio signal received from the STAs 111 and 113 in the area of the AP 121. In one embodiment, the RSS processor 320 determines whether the RSS is equal to or greater than a first predetermined threshold. In one embodiment, the RSS processing unit 320 may receive the RSS of the wireless signal from the wireless communication unit 212.

The packet retransmission rate processor 330 measures a retransmission rate of a packet included in a radio signal received from the STAs 111 and 113 when the RSS of the radio signal is greater than or equal to a predetermined first threshold. In one embodiment, if the RSS of the wireless signal is greater than the predetermined first threshold, the packet retransmission rate processing unit 330 records the number of packets retransmitted for a predetermined period in the counter, the number of packets retransmitted during the period If is less than the predetermined number, the counter can be cleared and the retransmission rate of the packet can be measured again.

If the number of retransmitted packets is greater than or equal to a predetermined number during the above period, the channel changing unit 340 may determine to transmit / receive a radio signal with the STAs 111 and 113 in its own area using another channel instead of the first channel. have. According to an embodiment, the channel changer 340 may select to use a channel that is not used by the neighboring AP of the AP 121 among the first to twelfth channels provided by the WLAN system 100. In another embodiment, the channel changer 340 may additionally select the RSS of the scan response signal to use the smallest channel. In the above selection, the channel changer 340 may retrieve and refer to the scan table stored in the storage 220.

The channel changer 340 generates a channel change message including information on a channel determined to be newly used, and transmits, for example, multicasts the generated channel change message to the STAs 111 and 113 in its own area. . When the channel change is completed by the channel changer 340, the AP 121 transmits / receives a radio signal with the STAs 111 and 113 in its own area through the newly determined channel.

4 is a flowchart illustrating a scan table generating method according to an embodiment of the present invention. Referring to FIG. 4, in block 400, the scan processor 310 of the AP 121 controls the wireless communicator 212 to transmit a scan signal through a plurality of channels provided by the WLAN system 100, and the wireless communicator 212. Receives a scan response signal for the scan signal from at least one AP of the WLAN system 100 over at least one of the plurality of channels (block 410). In block 420, the wireless communication unit 212 measures the RSS of each scan response signal, and in block 430, the scan processing unit 310 scans each channel that receives the scan response signal, including the identification information and the RSS of the corresponding channel. Create a table and complete the procedure. In the above-described example, although the wireless communication unit 212 has been described as measuring RSS, other components of the AP 121 may measure RSS.

5 is a flowchart illustrating a channel change method according to an embodiment of the present invention. Referring to FIG. 5, in block 500, the wireless communication unit 212 of the AP 121 transmits and receives a wireless signal to and from the STAs 111 and 113 in its own area through the n-th channel, and receives the wireless signal received from the STAs 111 and 113. Measure the RSS of the block (block 505). In block 510, the RSS processing unit 320 of the AP 121 determines whether the measured RSS is greater than or equal to a predetermined threshold RSSTH. If the determination determines that the measured RSS is less than the predetermined threshold RSSTH, the procedure moves to block 510.

If the measured RSS is greater than or equal to the predetermined threshold RSSTH, the packet retransmission rate processing unit 330 of the AP 121 initializes the counter inside the packet retransmission rate processing unit 330 (block 515), and is transmitted and received for a predetermined period. Among the packets in the radio signal, there is an error in the contents of the packets that are requested to be retransmitted from the STA 110 and / or the number of packets that are requested to be retransmitted to the STA 110 and re-received (Packet Return Number: PRN). Write to the counter (block 520). In block 525, the packet retransmission rate processing unit 330 determines whether the PRN recorded in the counter is equal to or greater than the predetermined threshold PRNTH. If the result of the determination is that the PRN recorded in the counter is less than the predetermined threshold PRNTH, the procedure moves to block 515.

If the PRN recorded in the counter is greater than or equal to the predetermined threshold PRNTH, the channel changing unit 340 may select a channel to be used instead of the nth channel among the channels provided by the WLAN system 100 based on the information recorded in the scan table. Select (block 530). According to an exemplary embodiment, a channel not used by the neighboring AP of the AP 121 is selected among the channels provided by the WLAN system 100, and the scan response signal when all the channels provided by the WLAN system 100 are used. You can select the channel with the smallest RSS.

In block 545, the channel changer 340 generates a channel change message including information about the selected channel, and transmits the generated channel change message to the STAs 111 and 113 in its own domain. In block 550, the channel changer 340 transmits / receives a wireless signal with the STAs 111 and 113 in its own area through the newly selected channel and ends the procedure.

Those skilled in the art will appreciate that in the processes described above and other processes, interactions, and methods, the functions performed within the processes, interactions, and methods may be implemented in a different order. In addition, the steps and operations described are provided by way of example only. That is, some of the steps and actions may be optional and may be combined into fewer steps and actions or extended to additional steps and actions without compromising the nature of the disclosed embodiments.

Those skilled in the art will also appreciate that the devices and methods described herein may be implemented in hardware, software, firmware, middleware, or combinations thereof, and may be used in systems, subsystems, components, or subcomponents thereof. Will know. For example, a method implemented in software can include computer code for performing the operations of the method. Such computer code may be stored on a machine readable medium, such as a processor readable medium or a computer program product, or transmitted over a transmission medium or communication link as a computer data signal embodied as a carrier wave or a signal modulated by a carrier wave. . Machine-readable media or processor-readable media can include any medium that can store or convey information in a form that can be read and executed by a machine (eg, processor, computer, etc.).

From the foregoing, various embodiments of the present disclosure have been described for purposes of illustration, and may be implemented in various modified forms without departing from the scope and spirit of the present disclosure. Accordingly, the various embodiments described herein are not to be taken in a limiting sense, and the true scope and spirit of the specification are indicated by the following claims.

1 is a conceptual diagram of a wireless LAN system according to an embodiment of the present invention.

FIG. 2 is a detailed block diagram of the AP shown in FIG. 1. FIG.

3 is a detailed block diagram of the controller shown in FIG. 2;

4 is a flowchart illustrating a scan table generation method according to an embodiment of the present invention.

5 is a flowchart illustrating a channel change method according to an embodiment of the present invention.

Claims (14)

A channel changing method of an access point (AP) performing wireless communication with an STA (Station), Receiving a radio signal including a packet from the STA via a first channel; Measuring a strength of the received wireless signal and measuring a retransmission rate of the packet if the measured strength of the wireless signal is greater than or equal to a threshold; And Determining whether to perform wireless communication with the STA through a second channel different from the first channel based on the measured retransmission rate; How to include. The method of claim 1, Determining whether to perform wireless communication with the STA through a second channel different from the first channel, Detecting at least one channel used by at least one AP neighboring the AP by scanning a plurality of channels supported by the AP; How to include more. The method of claim 2, Detecting at least one channel used by at least one AP neighboring the AP, Setting a channel not used by at least one AP neighboring the AP among the plurality of channels as the second channel; How to include more. The method of claim 2, Detecting at least one channel used by at least one AP neighboring the AP, Transmitting a scan signal to at least one of the plurality of channels; Receiving a response signal to the scan signal through at least one channel transmitting the scan signal from at least one AP neighboring the AP; And Measuring the strength of the response signal How to include. The method of claim 4, wherein Determining whether to perform wireless communication with the STA through a second channel different from the first channel, Determining any one of the plurality of channels as the second channel based on the strength of the response signal How to include. The method of claim 1, wherein the retransmission rate of the packet signal is measured. Recording the number of packets retransmitted for a predetermined period in a counter; And If the number of retransmitted packets is less than a predetermined number, clearing the counter How to include. The method of claim 1, Transmitting channel change information to the STA to the second channel How to include more. As an access point (AP), A wireless communication unit supporting wireless communication with a STA (Station) through a first channel or a second channel; And Receiving a radio signal including a packet from the STA through the first channel of the radio communication unit, and if the strength of the received radio signal is greater than or equal to a threshold, measure the retransmission rate of the packet, based on the measured retransmission rate To determine whether to communicate wirelessly with the STA via a second channel of the wireless communication unit AP including. The method of claim 8, wherein the control unit And an AP detecting at least one channel used by at least one AP neighboring the AP by scanning a plurality of channels supported by the AP. The method of claim 9, wherein the control unit, An AP which determines, as the second channel, a channel not used by at least one AP neighboring the AP among the plurality of channels. The method of claim 9, wherein the control unit Transmitting a scan signal to at least one of the plurality of channels, receiving a response signal to the scan signal through at least one of the channels transmitting the scan signal from at least one AP neighboring the AP, and receiving the response signal To measure the strength of the AP. The method of claim 11, wherein the control unit, And determine one of the plurality of channels as the second channel based on the strength of the response signal. The method of claim 8, wherein the control unit, The AP records the number of retransmitted packets in a counter for a predetermined period, and clears the counter when the number of retransmitted packets is less than a predetermined number. The method of claim 8, wherein the control unit An AP for transmitting channel change information to the STA.

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