KR101466917B1 - METHOD FOR ESTABLISHING SESSION BETWEEN APs AND METHOD FOR CONTROLLING SIGNAL INTERFERENCE BETWEEN APs - Google Patents

Abstract

A method of controlling radio wave interference between APs according to the present invention includes collecting information on neighboring neighbor APs using the same channel using a relay terminal connected to the header AP, Forwarding its IP address to the neighboring AP, establishing a session with the neighboring AP, and changing the channel of the target AP among the neighboring APs through the session established by the header AP. And controlling transmission power of the header AP and the target AP when the APs are using all channels.

Description

METHOD FOR SETTING A SESSION BETWEEN APS AND METHOD FOR CONTROLLING SIGNAL INTERFERENCE BETWEEN APS < RTI ID = 0.0 > APs < / RTI >

The following description relates to a method for establishing a session between APs in a WLAN environment and a method for controlling radio wave interference occurring between APs.

Wireless Local Area Network (WLAN) is a technology designed to compensate for the shortcomings of Ethernet, which is a wired LAN, and has the advantages of minimizing wiring work, maintenance and installation costs. Also, IEEE 802.11n with MIMO can provide high-speed wireless communication of up to 150 Mbps for an indoor terminal within a radius of 70 m, as a wireless access technology using an Industrial, Scientific and Medical (ISM) band.

WLAN is based on competing access based on CSMA / CA (Carrier Sensing Multiple Access with Collision Avoidance) and has a problem that performance is drastically lowered when APs having a large number of access terminals or using the same channel are adjacent to each other. In addition, signal interference and connection competition among APs arranged close to each other in a narrow area have intensified, resulting in frequent degradation of WLAN performance. In order to solve this problem, RRM (Radio Resource Management) technology which utilizes limited radio resources efficiently through interaction between APs is being developed.

Korean Patent Laid-Open No. 10-2012-0071489 discloses a method for selecting an AP capable of optimizing the performance of a wireless network while securing a bandwidth, and Korean Patent Laid-Open No. 10-2012-0097934 discloses a method for selecting an AP It explains how to save.

Cisco has analyzed the various problems that may arise in the installation and operation of APs in the WLAN environment and suggested RRM technologies to solve them. The RRM technologies aim at improving the performance of the WLAN by mitigating radio wave interference between the APs using the same channel by controlling the transmission power and the use channel based on the proximity information between the AP and the wireless channel environment.

In order to apply the efficient RRM technology, the Cisco RRM introduces the RF group concept as shown in FIG. An RF group is a logical collection of a plurality of APs located in a specific area, and indicates a range to which a specific RRM function is applied. Each RF group includes a number of controllers for performing and managing RRM functions, which select group leaders to determine and coordinate RRM operations across the RF group and follow the instructions of the group leader. The RF group formation process is as follows. Adjacent APs using the same channel form their own group through the process of identifying each other. At this time, the APs belonging to the same group periodically exchange the RF group name and the address information of the AP performing the controller role, and the information is transmitted to the controller to which the corresponding APs belong. Based on the information from the APs, the controller judges adjacent controllers corresponding to the same RF group and selects a group leader in this process. The selected group leader performs radio resource management for the entire RF group based on the RRM related information reported from the plurality of controllers.

Cisco's RRM technology is based on the Dynamic Channel Assignment (DCA) and Transmission Power Control (DCA) functions, in which all APs located in the RF group are controlled by the group leader, and the Coverage Hole Detection and Correction Algorithm (CHDCA) ) Function. DCA is a technique for controlling neighboring APs to use different radio channels, and TPC is a technique for controlling transmission power in consideration of communication ranges of APs, all of which are utilized to reduce signal interference between adjacent APs. The CHDCA is a technique for controlling the transmit power of surrounding APs in order to determine a shadow area where a controller can not provide a WLAN service for the communication area managed by the controller and to solve the shadow area.

Conventionally, RRM technologies of Cisco have contributed to improving the performance of a WLAN by systematically managing the operation of a plurality of APs through interoperation between them. However, for the application of the above technologies, a separate controller for controlling the operation of APs is needed. Furthermore, the installation of each AP should be established in consideration of connection with the controller and interworking with neighboring APs. Because of these limitations, Cisco's RRM technology is primarily applied to commercial WLANs managed by enterprise environments or carriers, but not to general AP equipment deployed in homes and offices.

IEEE 802.11 based WLAN APs are often installed unintentionally by individuals because they are easy to install. Therefore, it is necessary to study the ways in which adjacent APs can identify each other's existence and form a mutual communication session.

To solve such a problem, a technique described below attempts to identify different APs and establish a session between APs using a terminal located in a communication area overlapping between APs without a separate controller.

In addition, the technique described below attempts to avoid using the same channel between APs by exchanging information between APs through a connected communication session, and to control transmission power between APs.

The solutions to the technical problems described below are not limited to those mentioned above, and other solutions not mentioned can be clearly understood by those skilled in the art from the following description.

A method for establishing a session between APs for solving the above-mentioned problem is characterized in that the first AP selects a relay terminal among wireless terminals connected to the first AP, the first AP transmits an AP scanning request message to the relay terminal The relay terminal scans the beacon frame of the second AP to which the relay terminal can access using the AP scanning request message, and the relay terminal transmits an AP scanning response message including the beacon frame scanning result of the second AP to the first AP And transmitting the session establishment message including the IP information of the first AP to the second AP through the relay terminal to establish a session between the first AP and the second AP.

The AP scanning request message includes at least one of a scanning target channel, a scanning time point, or a CSMA / CA parameter.

The AP scanning response message includes at least one of the ESSID of the second AP, the BSSID of the second AP, or the strength of the second AP signal received by the relay terminal.

The step of selecting, transmitting, scanning and transmitting the relay terminal is repeatedly performed for all wireless terminals connected to the first AP.

In one aspect of the present invention, a method of controlling radio wave interference between APs includes collecting information on neighboring neighbor APs using the same channel using a relay terminal connected to the header AP, The method comprising the steps of: forwarding its IP address to a neighboring AP and establishing a session with the neighboring AP; and changing a channel of the target AP among the neighboring APs through a session established by the header AP, Is repeatedly performed for all relay terminals connected to the header AP.

 The step of collecting information comprises the steps of: selecting a relay terminal among the wireless terminals connected to the header AP by the header AP; transmitting to the relay terminal an AP scanning request including at least one of a scanning target channel, Scanning a beacon frame of a neighboring AP to which the relay terminal can connect using the AP scanning request message, transmitting the channel information of the neighboring AP, the terminal information connected to the neighboring AP, Transmitting the AP scanning response message including at least one of the strengths of the received neighboring AP signals to the header AP, and storing the information included in the AP scanning response message in the AP table.

The step of changing the channel includes the step of transmitting a channel allocation request message including the channel information of the AP itself, the channel information of the neighboring AP and the terminal information connected to the neighboring AP to the target AP, And changing its own channel using the channel.

In the step of changing the channel, the target AP changes its channel to a channel that is not used by the APs other than the target APs in the neighboring APs and the header APs.

Or changing the channel, the target AP can change its own channel to the channel of the neighboring AP having the smallest number of terminals located in the area overlapped with the neighboring AP using the terminal information connected to the neighboring AP.

According to another aspect of the present invention, there is provided a method of controlling radio wave interference between APs, comprising: collecting information on neighboring neighbor APs using the same channel using a relay terminal connected to the header AP; And establishing a session with the neighboring AP, and controlling the transmission power of the target AP among the neighboring APs through the session established by the header AP. The step of collecting information is repeatedly performed on all relay terminals connected to the header AP.

)가 자신과 중첩된 영역에 위치하는 대상 AP(

)에 전송전력 제어 메시지를 전송하는 단계,

가 자신에게 접속한 단말 중에서

로부터 수신한 신호의 세기가 가장 강한 단말(

)을 선택하는 단계,

가

이

로부터 수신한 신호의 세기(

)를 전달받는 단계,

가 선택한

의 식별자 및

를

에 전송하는 단계 및

는

가 사용할 전송전력(

) 및

가 사용할 전송전력(

)을 결정하고,

을 포함하는 전송전력 제어 실행 메시지를

에 전달하는 단계를 포함한다.The step of controlling the power comprises:

) Is located in the overlapping area of the target AP (

Transmitting a transmission power control message to the base station,

Lt; RTI ID = 0.0 >

The terminal having the highest strength of the signal received from the terminal

),

end

this

The intensity of the signal received from

),

Selected

And

To

; And

The

Transmit power to use (

) And

Transmit power to use (

),

A transmission power control execution message including

.

는

로 결정된다. 여기서,

는

에서

까지의 경로손실값,

는 채널에서의 셀 검색 임계값이다.

The

. here,

The

in

The path loss value up to < RTI ID =

Is the cell search threshold in the channel.

는

로 결정된다. 여기서,

는

에서

까지의 경로손실값,

는 채널에서의 셀 검색 임계값이다.

The

. here,

The

in

The path loss value up to < RTI ID =

Is the cell search threshold in the channel.

The techniques described below perform session establishment with a neighboring AP without the aid of a separate controller in a WLAN environment. Also, it exchanges information through the session and performs radio resource management between APs based on the information. In the session setup process of the below-described technique, a session is established by transmitting an IP address to a neighboring AP through a terminal located in a communication area where the APs are overlapped, and a separate controller is not necessary. do. Also, channel change and transmission power control between APs using the same channel are performed based on the information obtained from the neighbor AP through the session. This makes it possible to control radio interference in areas where communication areas between APs overlap. The transmission frame collision probability of the AP using the same channel decreases through the AP interference control, so that the data transmission rate of the AP can be improved.

The effects of the techniques described below are not limited to those mentioned above, and other effects not mentioned can be clearly understood by those skilled in the art from the following description.

1 is a schematic configuration diagram of an RF group in which RRM technology of Cisco is used.
2 is an example of a WLAN system using the same frequency channel.
Figure 3 is a schematic flow diagram of a method for establishing a session between APs;
FIG. 4 is a configuration diagram illustrating a network configuration operation in which a method of establishing a session between APs shown in FIG. 3 is performed.
5 is a schematic flow chart of a method of changing an AP's channel in a manner of controlling radio interference between APs.
FIG. 6 is a block diagram illustrating an operation between network configurations in which a method of changing an AP's channel shown in FIG. 5 is performed.
7 is a schematic flow chart of a method for controlling the transmission power of an AP in such a manner as to control radio interference between APs.
FIG. 8 is a configuration diagram illustrating a network configuration operation in which a method of controlling the transmission power of the AP shown in FIG. 7 is performed.
FIG. 9 shows experimental results of the AP-supported area for the case where the technique proposed in the present invention is used or not.
FIG. 10 is a graph showing an experiment result of a frame collision probability with and without the technique proposed in the present invention.
FIG. 11 is a graph of experimental data on data throughput for the case of using the technique proposed by the present invention and the case of not using the technique of the present invention.

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that the invention is not intended to be limited to the particular embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

The terms first, second, A, B, etc., may be used to describe various components, but the components are not limited by the terms, but may be used to distinguish one component from another . For example, without departing from the scope of the present invention, the first component may be referred to as a second component, and similarly, the second component may also be referred to as a first component. And / or < / RTI > includes any combination of a plurality of related listed items or any of a plurality of related listed items.

As used herein, the singular " include "should be understood to include a plurality of representations unless the context clearly dictates otherwise, and the terms" comprises & , Parts or combinations thereof, and does not preclude the presence or addition of one or more other features, integers, steps, components, components, or combinations thereof.

Before describing the drawings in detail, it is to be clarified that the division of constituent parts in this specification is merely a division by main functions of each constituent part. That is, two or more constituent parts to be described below may be combined into one constituent part, or one constituent part may be divided into two or more functions according to functions that are more subdivided. In addition, each of the constituent units described below may additionally perform some or all of the functions of other constituent units in addition to the main functions of the constituent units themselves, and that some of the main functions, And may be carried out in a dedicated manner.

Also, in performing a method or an operation method, each of the processes constituting the method may take place differently from the stated order unless clearly specified in the context. That is, each process may occur in the same order as described, may be performed substantially concurrently, or may be performed in the opposite order.

2 is an example of a WLAN system using the same frequency channel. Figure 2 illustrates the interference that occurs between APs using the same channel in an IEEE 802.11 WLAN environment. In FIG. 2, AP # 1 and AP # 2 using Ch.1 have coverage areas in which they can communicate with each other. The area indicated by a circle around each of AP # 1 and AP # 2 corresponds to the support area. On the other hand, in a region where AP # 1 and AP # 2 overlap each other, radio waves are interfered because two APs use the same channel. A terminal located in such an overlapped area has poor communication quality due to radio wave interference.

It is possible to improve the efficiency of the entire WLAN system by controlling the channel or the transmission power allocated to the AP. However, as described above, there is almost no way for an AP installed by an individual, such as a home, to change a channel or control transmission power .

The method according to the present invention described below collects information including channel information of an adjacent AP and intensity of a received signal from the AP through a wireless terminal connected to the AP, and proposes a method of establishing a session between the APs. Furthermore, we propose a method to change the channel or control the transmission power between the APs through the established session.

Hereinafter, a method of establishing a session between APs and a method of controlling radio wave interference between APs will be described in detail with reference to the drawings. Figure 3 is a schematic flow diagram of a method for establishing a session between APs;

A method for establishing a session between APs according to the present invention comprises the steps of (500) selecting a relay terminal among wireless terminals connected to a first AP by the first AP, transmitting the AP scanning request message to the relay terminal In operation 501, the relay terminal scans 502 a beacon frame of a second AP to which the relay terminal can connect using the AP scanning request message. In operation 502, the relay terminal scans APs including the beacon frame scanning result of the second AP Transmitting a response message to the first AP (step 503), and transmitting the session setup message including the IP information of the first AP to the second AP through the relay terminal to transmit a session between the first AP and the second AP (Step 505).

Based on the AP scanning response message received from the relay terminal, the first AP determines whether it is adjacent to the second APs and manages the information in the form of a table.

The first AP selects one relay terminal (STA ₁ ) among the wireless terminals connected to the first AP and scans a beacon frame with respect to another AP (second AP) to which the relay terminal has access or can access. (AP) scanning request message to all the wireless terminals (STA _N ) connected to the first AP, instead of transmitting the AP scanning request message to the one relay terminal (STA ₁ ) Lt; RTI ID = 0.0 > AP < / RTI >

Accordingly, the steps of selecting (500), transmitting (501), scanning (502) and transmitting (503) the relay terminal described above are repeatedly performed )do. The first AP may sequentially transmit the AP scanning request message to all the wireless terminals and receive the AP scanning response message from the second AP or may transmit the AP scanning request message to all the wireless terminals at the same time There will be. It is sufficient to acquire information about an adjacent AP in consideration of a network resource situation and the like. As a result, the second AP is one or more APs, and in a region where a lot of APs are installed, such as a residence, a large number of APs will correspond to a second AP.

The AP scanning request message includes at least one of a scanning target channel, a scanning time point, or a CSMA / CA parameter.

The AP scanning response message includes at least one of an Extended Service Set ID (ESSID) of the second AP, a Basic Service Set ID (BSSID) of the second AP, and an intensity of the second AP signal received by the relay terminal.

The first AP that has grasped the neighboring second AP transmits a session setup request message including its own IP address to the relay terminal that identifies the corresponding AP in order to establish a session between the second AP and the second AP. The relay terminal having received the session setup request message accesses the second AP and transmits a corresponding session setup request message. The second AP performs session connection to the IP address of the first AP included in the session setup request message through the wired IP network connected to the Internet.

FIG. 4 is a configuration diagram illustrating a network configuration operation in which a method of establishing a session between APs shown in FIG. 3 is performed. In FIG. 4, AP ₁ denotes a first AP, AP ₂ denotes a second AP, and STA denotes a relay terminal.

The first AP (AP ₁ ) selects, as a relay terminal, a wireless terminal capable of supporting the search for an adjacent AP among the wireless terminals connected to the first AP (AP ₁ ). It is preferable that the first AP (AP ₁ ) searches all of the wireless terminals connected to the first wireless access terminal (AP ₁ ) as a relay terminal and searches for an adjacent wireless access point (AP) in order to search all possible APs around the first AP (AP ₁ ). This is because it is a final object of the present invention to control channel change or transmission power for an adjacent AP that can cause radio interference using the same channel. However, it is preferred to claim 1 AP (AP ₁₎ a method for selecting the relay terminal of claim 1 AP preferentially selects a radio terminal of the resources and the available electric power is connected to the terminal (AP _1).

The first AP (AP ₁ ) transmits an AP scanning request message including a radio channel for scanning, a scanning time, and CSMA / CA parameter information for granting access priority to the selected relay terminal. The relay terminal, which has received the response, determines whether to perform the AP scanning in consideration of its buffer status, operation status, and the like.

When the relay terminal decides to perform AP scanning, the relay terminal transmits a beacon frame from the neighboring second APs (AP ₂ ) to the corresponding wireless channel based on the information included in the received AP scanning request message Scanning is performed. Since the relay terminal scanning the neighboring claim ₂ AP (AP 2) of the ESSID and the relay terminal to the AP scanning response message including the strength of a signal received from the AP in the form (Information Element) IE of claim 1 AP (AP ₁ .

Based on the AP scanning response message received from the relay terminal, the first AP (AP ₁ ) determines whether it is adjacent to the neighboring APs and manages the information in the form of a table. The process of searching for the first AP (AP ₁ ) and the second AP (AP ₂ ) through the relay terminal is repeatedly performed for a plurality of relay terminals connected to the first AP (AP ₁ ) ₁ ) can grasp all adjacent second APs (AP ₂ ).

The first AP (AP ₁ ) that has determined the neighboring second AP (AP ₂ ) transmits a session setup request message including its own IP address to the second AP (AP ₂ ) in order to establish a session between the second AP AP ₂ ) to the identified relay terminal. The session setup is such that the first AP (AP ₁ ) is individually set for the adjacent AP. The first AP (AP ₁ ) receives information on all adjacent APs using the relay terminal, but will set the session only for at least one of them.

The relay terminal having received the session setup request message accesses the second AP (AP ₂ ) and transmits a corresponding session setup request message. The second AP (AP ₂ ) performs session connection to the IP address of the first AP (AP ₁ ) included in the session setup request message through the wired IP network connected to the Internet. Also, the second AP (AP ₂ ) may transmit a session setup response message to the first AP (AP ₁ ) in response to the session setup request message.

5 is a schematic flow chart of a method of changing an AP's channel in a manner of controlling radio interference between APs.

Referring to FIG. 5A, a method of controlling radio wave interference between APs according to an embodiment of the present invention includes collecting information on neighboring neighbor APs using the same channel using a relay terminal to which the header AP is connected 610), establishing a session with a neighboring AP by forwarding its IP address to a neighboring AP using the information collected by the header AP (step 630), and changing the channel of the target AP among the neighboring APs (Step 640). Preferably, the step of collecting information is repeatedly performed 620 on all relay terminals connected to the header AP.

Meanwhile, a method of controlling radio wave interference between APs according to the embodiment may further include transmitting (650) the channel information of the target AP to which the target AP has changed, to the APs other than the target AP among the header APs or neighboring APs .

Referring to FIG. 5B, the step 610 of collecting information includes a step 611 of selecting a relay terminal among the wireless terminals connected to the header AP by the header AP, a step 611 of transmitting the scanning target channel, (612) an AP scanning request message including at least one of a CSMA / CA parameter, a scanning step (613) of a beacon frame of a neighboring AP to which the relay terminal is connectable using the AP scanning request message, (614) an AP scanning response message including at least one of the channel information of the neighboring AP, the terminal information connected to the neighboring AP, or the strength of the neighboring AP signal received by the relaying terminal to the header AP, And storing (615) the AP in the AP table the information included in the AP scanning response message.

Step 610 of collecting information and step 620 of establishing a session between the header AP and the neighboring AP correspond to a method of establishing a session between APs shown in FIG.

The step 640 of changing the channel includes a step 641 of transmitting a channel allocation request message including the channel information of the AP itself, the channel information of the neighboring AP and the terminal information connected to the neighboring AP to the target AP, (642) of changing its channel using the channel allocation request message.

In step 640 of changing the channel, the target AP may change its own channel to a channel not used by the APs other than the target APs in the neighboring APs and the header APs.

Or changing the channel (step 640), the target AP can change its own channel to the channel of the neighboring AP having the smallest number of terminals located in the area overlapped with the neighboring AP using the terminal information connected to the neighboring AP. This channel change method may be applied when all of the APs use all the channels and there is no channel to be changed by the neighboring APs.

는 헤더 AP,

는 이웃 AP 중 채널 변경 대상이 되는 대상 AP이고, STA는

와

의 중첩 영역에 위치하는 무선단말을 의미한다.FIG. 6 is a block diagram illustrating an operation between network configurations in which a method of changing an AP's channel shown in FIG. 5 is performed. 6

The header AP,

Is a target AP to be a channel change target among neighbor APs, and the STA

Wow

The wireless terminal is located in the overlapping area of the wireless terminal.

)는 자신과 동일채널을 사용하는 인접한 이웃 AP들로부터의 간섭을 완화하기 위해 AP간 연결된 세션을 통한 정보교환을 기반으로 협력 RRM을 수행한다. 본 발명에서 무선자원 관리를 위해 고려되는 환경으로 AP가 동일한 주파수 채널을 사용하는 경우 중첩된 통신영역 내 존재하는 전파간섭을 제어하기 위해 인접한 AP간 협력 기반의 무선자원관리가 가능하다.Header AP (

Performs a cooperative RRM based on information exchange through a connected session between APs to mitigate interference from neighboring neighboring APs using the same channel as itself. In the present invention, when an AP uses the same frequency channel as an environment to be considered for radio resource management, cooperative base radio resource management between adjacent APs is possible to control radio interference existing in the overlapped communication area.

)와 인접한 대상 AP(

)들이 동일 채널을 사용하지 않도록 대상 AP(

)들의 채널을 변경하기 위해 헤더 AP는 앞서 세션설정 과정에서 작성된 동일채널을 사용하는 인접한 AP들에 대한 테이블을 이용한다. Header AP (

) And an adjacent AP (

) Do not use the same channel.

), The header AP uses a table for adjacent APs using the same channel created in the session establishment process.

)는 자신이 사용하는 채널번호 및 자신의 중첩된 통신영역 내에 위치하는 단말의 수를 포함하는 채널배치 요청 메시지를 동일채널을 사용하는 대상 AP(

)로 전송한다. 채널배치 요청 메시지를 수신한 대상 AP(

)는 헤더 AP(

) 및 다른 인접 AP들이 사용하지 않는 채널을 자신이 변경할 채널로 결정한다. Based on the information created in the table, the header AP (

Transmits a channel allocation request message including the channel number used by itself and the number of terminals located in the overlapped communication area of its own to the target AP

). The target AP (< RTI ID = 0.0 >

) Includes a header AP (

) And a channel that is not used by other neighboring APs as a channel to be changed.

)는 헤더 AP(

) 및 인접한 AP들과 통신영역이 중첩지역에 위치한 단말 수가 가장 적은 AP가 사용하는 채널을 사용함으로써 동일채널 사용으로 인한 간섭의 피해를 받는 단말들의 수를 최소화한다. 채널변경을 수행한 후 대상 AP(

)는 헤더 AP(

) 및 인접한 AP들에게 자신이 사용하기로 결정한 채널을 알리는 메시지를 광고한다.
If all channels are being used by the header AP and neighbor APs, the target AP

) Includes a header AP (

) And the number of terminals affected by interference due to the use of the same channel is minimized by using the channel used by the AP having the smallest number of terminals located in the overlapping area with the adjacent APs. After performing the channel change, the target AP (

) Includes a header AP (

) And advertises a message informing adjacent APs of the channel that it has decided to use.

7 is a schematic flow chart of a method for controlling the transmission power of an AP in such a manner as to control radio interference between APs. A method of controlling radio interference includes a channel changing method and a method of changing the coverage of an AP as described in FIG. Also, the method of controlling the transmission power of the AP can be used when there is an adjacent AP using the same channel even after the channel change of the AP is performed.

)가 자신에게 접속된 중계단말(

)을 이용하여 동일한 채널을 이용하는 인접한 이웃 AP에 대한 정보를 수집하는 단계(710), 헤더 AP(

)가 수집한 정보를 이용하여 자신의 IP 주소를 이웃 AP에 전달하고 이웃 AP와 세션을 설정하는 단계(730) 및 헤더 AP(

)가 설정된 세션을 통해 이웃 AP 중에서 대상 AP(

)의 전송전력을 제어하는 단계(740)를 포함한다. 정보를 수집하는 단계(710)는 헤더 AP(

)에 접속된 모든 중계단말에 대해 반복적으로 수행(720)된다.Referring to FIG. 7A, a method for controlling radio wave interference between APs according to another embodiment of the present invention includes a header AP (

) Is connected to the relay terminal (

Collecting information on neighboring neighbor APs using the same channel 710,

(730) of establishing a session with a neighboring AP by forwarding its IP address to a neighbor AP using information collected by the AP

) Is set to the target AP (

(Step 740). ≪ / RTI > The step of collecting information 710 may include collecting information from the header AP (

(720) repeatedly for all relay terminals connected to the relay terminal.

)가 헤더 AP(

)에 접속된 무선단말 중에서 중계단말()을 선택하는 단계(711), 헤더 AP(

)가 중계단말(

)에 스캐닝 대상 채널, 스캐닝 시점 또는 CSMA/CA 파라미터 중 적어도 하나를 포함하는 AP 스캐닝 요청 메시지를 전송하는 단계(712), 중계단말(

)이 AP 스캐닝 요청 메시지를 이용하여 중계단말(

)이 접속가능한 이웃 AP의 비콘 프레임을 스캐닝하는 단계(713), 중계단말(

)이 이웃 AP의 채널정보, 이웃 AP에 접속한 단말정보 또는 중계단말(

)이 수신한 이웃 AP 신호의 세기 중 적어도 하나를 포함하는 AP 스캐닝 응답 메시지를 헤더 AP(

)에 전송하는 단계(714) 및 헤더 AP(

)가 AP 스캐닝 응답 메시지에 포함된 정보를 AP 테이블에 저장하는 단계(715)를 포함한다. 도 7(a)에 도시된 정보를 수집하는 단계(710)는 도 5(b)에 도시된 단계와 동일한 단계이다.The step of collecting information 710 may include collecting information from the header AP (

) Is the header AP (

Selecting (711) a relay terminal () among the wireless terminals connected to the header AP

) To the relay terminal (

(712) an AP scanning request message including at least one of a scanning target channel, a scanning time point, and a CSMA / CA parameter,

) Using the AP scanning request message to the relay terminal

Scanning 713 the beacon frame of the connectable neighbor AP,

) Of the neighboring AP, channel information of the neighboring AP, terminal information connected to the neighboring AP,

The strength of the neighbor AP signal received by the header AP

(Step 714) and a header AP

(715) storing the information included in the AP scanning response message in the AP table. The step 710 of collecting the information shown in Fig. 7 (a) is the same as the step shown in Fig. 5 (b).

)가 자신과 중첩된 영역에 위치하는 대상 AP(

)에 전송전력 제어 메시지를 전송하는 단계(741),

가 자신에게 접속한 단말 중에서

로부터 수신한 신호의 세기가 가장 강한 단말(

)을 선택하는 단계(742),

가

이

로부터 수신한 신호의 세기(

)를 전달받는 단계(743),

가 선택한

의 식별자 및

를

에 전송하는 단계(744) 및

는

가 사용할 전송전력(

) 및

가 사용할 전송전력(

)을 결정하고,

을 포함하는 전송전력 제어 실행 메시지를

에 전달하는 단계(745)를 포함한다.The step of controlling power 740 may include controlling the power of the header AP (

) Is located in the overlapping area of the target AP (

Transmitting (741) a transmission power control message to the base station

Lt; RTI ID = 0.0 >

The terminal having the highest strength of the signal received from the terminal

(Step 742), < RTI ID = 0.0 >

end

this

The intensity of the signal received from

(Step 743),

Selected

And

To

(Step 744) and

The

Transmit power to use (

) And

Transmit power to use (

),

A transmission power control execution message including

Lt; RTI ID = 0.0 > 745 < / RTI >

)가 이웃 AP 및 자신의 전송전력을 결정하기 위해서는 헤더AP(

)와 중계단말(

) 사이의 경로손실, 중계 단말(

)이 헤더AP(

)로부터 받은 신호세기, 그리고 헤더AP(

)의 전송전력 값을 알아야한다. 우선 헤더 AP(

)는 중계단말(

)의 경로손실 값을 측정한다. 아래의 수학식 1을 통해 헤더 AP(

)와 중계단말(

) 사이의 경로손실값(

)이 산출된다.
In the process, the header AP (

To determine the neighbor AP and its transmission power, the header AP

) And the relay terminal

), The path loss between the relay terminal

) This header AP (

), And the header AP (

) Of the transmission power. First, the header AP (

) Is a relay terminal

) Is measured. The header AP (

) And the relay terminal

) ≪ / RTI >

) Is calculated.

는 헤더 AP의 전송전력값이고,

는 중계단말이 헤더 AP로부터 수신하는 신호의 세기값이다.
here,

Is the transmission power value of the header AP,

Is the strength value of the signal received by the relay terminal from the header AP.

)은 아래의 수학식 2와 같이 표현된다.
After the transmission power is controlled in the header AP, the intensity value of the signal received by the relay terminal (

) Is expressed by the following equation (2).

는 전송전력이 제어된 헤더 AP의 전송전력값이다.
here,

Is the transmission power value of the header AP whose transmission power is controlled.

) 및 전송전력이 제어된 후 중계단말이 대상 AP로부터 수신하는 신호의 세기(

)를 연산할 수 있다.
The path loss value from the target AP to the relay terminal in the same manner as in Equations (1) and (2)

) And the strength of a signal received by the relay terminal from the target AP after the transmission power is controlled

) Can be calculated.

와

는 아래의 수학식 3과 같은 조건을 갖는다. 여기서,

는 채널에서의 셀 검색 임계값(cell searching threshold)

Wow

Has the same condition as the following Equation (3). here,

Cell searching threshold < RTI ID = 0.0 >

) 및 대상 AP의 전송전력값(

)은 각각 아래의 수학식 4 및 수학식 5와 같다.
The transmission power value of the header AP whose transmission power is controlled under the condition of Equation (3)

) And the transmission power value of the target AP (

Are respectively represented by the following equations (4) and (5).

FIG. 8 is a configuration diagram illustrating a network configuration operation in which a method of controlling the transmission power of the AP shown in FIG. 7 is performed. The method shown in Fig. 8 is one method for controlling radio wave interference between APs according to the present invention. Although it is possible to use a method of controlling an independent radio wave interference, it is also possible to use an AP in which all the available channels of the AP are used or the same channel is used after changing the channel according to FIG. 5 It may be a radio wave interference method that is additionally performed when it is present.

)는 자신과 동일채널을 사용하며 통신영역이 중첩되는 대상 AP (

)을 탐지하면 해당 대상 AP (

)에게 전송전력 제어 요청메시지를 전송한다. 전송전력 제어요청 메시지를 수신한 대상 AP (

)은 앞서 수행한 이웃 AP 탐색절차에서 얻은 정보를 바탕으로, 자신에게 접속한 단말들 중 헤더 AP(

)로부터의 RSS가 가장 강한 단말을 전송전력 제어 기준단말(

) 로 선택하고, 해당 단말(

)이 헤더 AP(

)로부터 수신한 신호세기(

)를 보고받는다. Header AP (

) Uses the same channel as itself and the target AP (

), The target AP (

And transmits a transmission power control request message to the base station. The target AP (s) that received the transmit power control request message

Based on the information obtained from the neighbor AP search procedure performed previously, the header AP

) To the transmission power control reference terminal (

), And the terminal (

) This header AP (

) ≪ / RTI >

).

)는

와

를 전송전력 제어 응답메시지를 통해 헤더 AP(

)에게 전송한다. 전송전력제어 응답 메시지를 수신한 헤더 AP(

)는 자신 및 대상 AP (

)가 사용할 전송전력 값을 결정하고, 전송전력 결정 결과를 알리는 전송전력 제어 실행 메시지를 대상 AP (

)에게 전송한다. 이 후 헤더 AP(

)와 대상 AP (

)은 결정된 전송전력을 이용하여 통신을 수행한다.
Then,

)

Wow

Through the transmission power control response message to the header AP (

. The header AP (< RTI ID = 0.0 >

) ≪ / RTI >

) And determines a transmission power control execution message indicating the transmission power determination result to the target AP

. The header AP (

) And the target AP

Performs communication using the determined transmission power.

FIGS. 9 to 11 illustrate the results of experiments on the technique proposed by the present invention. In the present invention, a simulator based on C language was built to evaluate the performance of the proposed technique. The simulator considers the IEEE 802.11g environment and the maximum data rate of AP is 54Mbps. The initial transmission power value of the AP and the UE is set to 20 dBm. Although the transmission power control of the AP is considered in the simulation, the transmission power control of the UE is not considered.

 As an experiment of the present invention, the scenario is divided into two. The first scenario measures the change in the number of APs and the communication area of the AP per channel due to the use of the present invention. The second scenario measures the performance of the network, which is changed due to the use of the technique proposed in the present invention. The results for the first scenario are shown in FIG. 9, and the results for the second scenario are shown in FIG. 10 and FIG.

The first scenario was performed proposed scheme in the present invention after the randomly distributed twenties AP 100 and one terminal on the square area of 100m ^2. After using the proposed scheme, the AP allocation is uniformly formed, and the communication area of the AP is controlled for inter-AP interference control. Through this, the use of the same channel between APs with overlapping communication areas is avoided, and overlapping areas between APs using the same channel are reduced.

FIG. 9 is a graph illustrating experimental results on coverage of an AP with and without the technique proposed in the present invention. In FIG. 9, an area indicated by a circle is a support area where each AP can detect a terminal. As shown in FIG. 9, since the transmission power of the AP is not separately controlled, the supporting areas have the same size.

9 (a) and 9 (b) show the case where channel 1 is used, and FIGS. 9 (c) and 9 ) Is the case where channel 11 is used. The proposed technique is labeled "Proposed" and the control group to which the technique of the present invention is not applied is labeled "Conventional".

Since the APs shown in Figs. 9A, 9C, and 9E use random channels, the AP coverage is greatly overlapped. 9 (b), 9 (d) and 9 (f) show a case where a channel is changed by applying the radio interference control method proposed in the present invention, and when the same channel exists after the channel is changed, The results are shown in Fig. After the present invention has been applied, overlapping areas have been significantly reduced. The power of some APs is turned off because the transmission power determined by Equations (4) and (5) becomes lower than the minimum transmission power of the AP.

The second scenario was placed uniformly in a square area of 40m ² AP 2-by-2 grid in order to evaluate the performance of the transmission power control scheme of the AP as the interference control method between the AP. Two of the four APs (# 1 and # 2) allocated channel 6 and the remaining two (# 3 and # 4) channels # 1 and # 11.

FIG. 10 is a graph showing an experiment result of a frame collision probability with and without the technique proposed in the present invention. In order to evaluate the network performance change according to the number of terminals, the number of terminals was increased to 100 to 40 terminals. Prior to controlling transmission power, interference between APs using the same channel occurs and the frame collision probability is about 0.32. However, after transmission power control, interference between APs using the same channel is reduced, and the frame collision probability is reduced to about 0.4.

FIG. 11 is a graph of experimental data on data throughput for the case of using the technique proposed by the present invention and the case of not using the technique of the present invention. In order to evaluate the network performance change according to the number of terminals, the number of terminals was increased to 100 to 40 terminals. After the transmission power control, the influence of the interference between the same APs is reduced, and the data throughput of the AP is improved by about 45% compared to that before the transmission power control.

It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. It will be understood that variations and specific embodiments which may occur to those skilled in the art are included within the scope of the present invention.

Claims (15)

delete delete delete delete A method for controlling radio interference between APs in a WLAN environment,
Collecting information on an AP adjacent to the header AP using a relay terminal connected to the header AP as a relay device;
The collected information includes channel information for the neighboring AP. The header AP uses the collected information to transmit its IP address to a neighboring AP that uses the same channel as the header AP among the APs, Establishing a session with the AP; And
And changing the channel of the target AP among the neighbor APs through the established session,
Wherein collecting the information is performed repetitively for all relay terminals connected to the header AP. 6. The method of claim 5,
The step of collecting the information
Selecting a relay terminal among the wireless terminals connected to the header AP by the header AP;
Transmitting, by the header AP, an AP scanning request message including at least one of a scanning target channel, a scanning time, and a CSMA / CA parameter to the relay terminal;
Scanning the beacon frame of the neighboring AP to which the relay terminal is connectable using the AP scanning request message;
Transmitting, to the header AP, an AP scanning response message including at least one of channel information of the neighboring AP, terminal information connected to the neighboring AP, and strength of the neighboring AP signal received by the relaying terminal ; And
And wherein the header AP stores information included in the AP scanning response message in an AP table. The method according to claim 6,
The step of changing the channel
Transmitting a channel assignment request message including the channel information of the AP, the channel information of the neighbor AP, and the terminal information connected to the neighbor AP to the target AP; And
And changing the channel of the target AP using the channel allocation request message. 8. The method of claim 7,
The step of changing the channel
Wherein the target AP controls radio wave interference between the AP excluding the target AP and the AP changing its channel to a channel not used by the header AP in the neighbor AP. 8. The method of claim 7,
The step of changing the channel
And the target AP controls the radio wave interference between the APs that change its own channel to the channel of the neighboring AP having the smallest number of terminals located in the area overlapping the target AP using the terminal information connected to the neighboring AP. 6. The method of claim 5,
And transmitting the changed channel information of the AP to the AP other than the AP of the header AP or the neighboring AP. A method for controlling radio interference between APs in a WLAN environment,
Collecting information on an AP adjacent to the header AP using a relay terminal connected to the header AP as a relay device;
The collected information includes channel information for the neighboring AP. The header AP uses the collected information to transmit its IP address to a neighboring AP using the same channel as the header AP among the APs, Establishing a session with the AP; And
The header AP controlling at least one of a transmission power of the header AP or a transmission power of a target AP among the neighbor APs through the established session,
Wherein collecting the information is performed repetitively for all relay terminals connected to the header AP. 12. The method of claim 11,
The step of collecting the information
Selecting a relay terminal among the wireless terminals connected to the header AP by the header AP;
Transmitting, by the header AP, an AP scanning request message including at least one of a scanning target channel, a scanning time, and a CSMA / CA parameter to the relay terminal;
Scanning the beacon frame of the neighboring AP to which the relay terminal is connectable using the AP scanning request message;
Transmitting, to the header AP, an AP scanning response message including at least one of channel information of the neighboring AP, terminal information connected to the neighboring AP, and strength of the neighboring AP signal received by the relaying terminal ; And
And wherein the header AP stores information included in the AP scanning response message in an AP table. 12. The method of claim 11,
The step of controlling the power comprises:
The header AP (

) Is located in the overlapping area of the target AP (

Transmitting a transmission power control message to the base station;
remind

Of the terminals connected to the terminal

The terminal having the highest strength of the signal received from the terminal

);
remind

Gt;

In this case,

The intensity of the signal received from

);
remind

Selected

And

Gt;

; And
remind

Quot;

Transmit power to use (

) And the above

Transmit power to use (

),

A transmission power control execution message including

RTI ID = 0.0 > 1, < / RTI > 14. The method of claim 13,
remind

Is a method for controlling radio interference between APs determined by the following equation.

(here,

The

in

The path loss value up to < RTI ID =

≪ / RTI > is the cell search threshold in the channel) 14. The method of claim 13,
remind

Is a method for controlling radio interference between APs determined by the following equation.

(here,

The

in

The path loss value up to < RTI ID =

≪ / RTI > is the cell search threshold in the channel)

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