KR100854866B1 - Method and apparatus for performing handoff of a wireless lan station - Google Patents

Abstract

This application discloses an access point apparatus. According to an embodiment, the access point apparatus detects a wireless LAN terminal associated with a wireless communication unit and another access point apparatus that provides an eavesdrop channel through the same frequency band as the eavesdropping channel through the eavesdropping channel, and And a controller for transmitting a WLAN terminal detection message including information on the WLAN terminal to the other access point. According to the above embodiment, it is possible to detect an STA to be handed off quickly or an adjacent MAP to be handed over effectively in a wireless mesh network, and a frame transmitted to the STA is not lost while the handoff is being performed, A session can be performed that does not disconnect.

Wireless Mesh Network, Handoff, Eavesdropping Channel

Description

TECHNICAL AND APPARATUS FOR PERFORMING HANDOFF OF A WIRELESS LAN STATION

1A is a conceptual diagram of a wireless mesh network system according to one embodiment.

FIG. 1B is an enlarged partial view of the STA and first to third MAPs shown in FIG. 1A; FIG.

2A is a conceptual diagram of an AP initiated handoff of a wireless mesh network system according to an embodiment.

2B is a conceptual diagram of a terminal initiated handoff of a wireless mesh network system according to an embodiment.

3 is a block diagram of a MAP according to one embodiment.

4 is a flowchart illustrating a method for detecting an STA of a third MAP according to an embodiment.

5 is a flowchart illustrating a handoff method of a first MAP according to an embodiment.

6 is a flowchart of a handoff method of a third MAP according to an embodiment.

The present invention relates to a handoff method of a WLAN terminal, and more particularly, to a method and apparatus for performing a handoff by effectively detecting a WLAN terminal belonging to a handoff area.

An IEEE 802.11 based wireless mesh network is a system configured by combining technologies related to wireless access network of WLAN and multiple hop routing, automatic network configuration, and automatic routing rerouting of mesh networks. The wireless mesh network is largely composed of a WLAN (Station) STA and a Mesh Access Point (MAP). The biggest feature of the wireless mesh network is that the wireless sections are connected between MAPs, and various paths exist between neighboring MAPs.

According to IEEE 802.11, an STA establishes an association with one MAP and wirelessly transmits and receives a frame only through the connected MAP. As the STA moves to the outside of the currently connected MAP area, the STA enters an overlapping area (or handoff area) overlapping with the area of another MAP. In this case, the STA is disconnected from the currently connected MAP and connected with another neighboring MAP. A handoff procedure for establishing reassociation is initiated by the STA or the MAP.

In the conventional wireless mesh network, the STA handoff method is largely divided into two methods. One, if the channel used by the STA is the same channel as that used by another neighboring MAP (that is, belongs to the same frequency band), the STA receives a beacon frame transmitted periodically by the neighboring MAP through the corresponding channel. It is a method of confirming that a new MAP is nearby (Passive Scanning), disconnecting from a currently connected MAP, and reconnecting to a new MAP. On the other hand, if the channel used by the STA is different from the channel used by another neighboring MAP (that is, belongs to a different frequency band), the received signal strength (RSS: Received) of the frame received from the MAP to which the STA is currently connected. As signal strength decreases below a preset threshold, there is a method of broadcasting a probe request frame to another channel, receiving a probe response frame for a probe request frame from another MAP, and reconnecting the corresponding MAP. .

However, according to the conventional handoff method, in the case of Active Scanning, a MAP to be handed over is broadcast by broadcasting a frame to several channels, and in the case of Passive Scanning, the STA is limited to a channel used by the STA. Excessive delays may occur. Since the conventional handoff method releases the connection with the currently connected MAP and reconnects with the new MAP, the frame transmitted to the moving STA may be lost, and the existing session is disconnected. There is a problem. In addition, the conventional handoff method does not consider the traffic load and the quality of service (QoS) of the MAP, and thus the problem of failing to provide a method of reconnecting to a MAP suitable for processing a data frame transmitted and received by the STA is not provided. have.

Accordingly, an object of the present invention is to provide a method and apparatus for detecting an STA to be handed off effectively or a neighboring MAP to be handed over in a wireless mesh network.

It is another object of the present invention to provide a handoff method and apparatus which does not lose a frame transmitted to an STA while a handoff is performed, and does not disconnect a previously established session.

It is still another object of the present invention to provide a handoff method and apparatus for reconnecting to an appropriate MAP according to a type of data frame currently transmitted / received by an STA in consideration of traffic load and quality of service (QoS) of the MAP to be reconnected. will be.

According to one embodiment, an access point apparatus is provided. The access point apparatus detects a wireless LAN terminal associated with a wireless communication unit and another access point apparatus that provide an eavesdropping channel through the same frequency band as the eavesdropping channel through the eavesdropping channel, And a control unit for transmitting a WLAN terminal detection message including information to the other access point.

According to another embodiment, an access point apparatus is provided. The access point apparatus includes a wireless communication unit that provides at least one normal channel and / or an eavesdrop channel, and a control unit that periodically transmits a beacon frame through the eavesdrop channel and / or the normal channel.

According to another embodiment, an access point apparatus for connecting to any WLAN terminal and performing wireless communication is provided. The access point device receives a handoff start notification frame from a wireless communication unit, a storage unit, and the wireless LAN terminal to release the connection with the wireless LAN terminal, and a frame destined for the wireless LAN terminal from any other device. And a controller configured to receive the data, buffer the storage unit, and transmit the buffered frame to another access point device reconnected with the WLAN terminal.

According to another embodiment, an access point apparatus for connecting to any WLAN terminal and performing wireless communication is provided. The access point apparatus may include a wireless communication unit for receiving a WLAN terminal sensing message for the WLAN terminal from each of a plurality of different access point apparatuses, wherein each WLAN terminal sensing message includes information on the corresponding access point apparatus; And a controller for selecting an access point device for handing over the WLAN terminal based on the information on the access point device included in each WLAN terminal detection message.

According to one embodiment, a method for detecting a WLAN terminal of an access point device is provided. The method includes establishing an interception channel; And detecting the wireless LAN terminal associated with another access point device through the same frequency band as the interception channel through the interception channel.

According to another embodiment, a WLAN terminal detection method of an access point apparatus is provided. The method includes establishing at least one normal channel and / or an intercepting channel; Periodically transmitting a beacon frame on the interception channel and / or the normal channel; And detecting the WLAN terminal by receiving a frame from the WLAN terminal receiving the beacon frame.

According to another embodiment, there is provided a handoff method of an access point apparatus for performing wireless communication by connecting to an arbitrary WLAN terminal. The method includes receiving a handoff start notification frame from the WLAN terminal; Releasing the connection with the WLAN terminal; Receiving a frame destined for the WLAN terminal from any other device; Buffering the received frame; And transmitting the buffered frame to another access point device reconnected with the WLAN terminal.

According to another embodiment, there is provided a handoff method of an access point apparatus for performing wireless communication by connecting to an arbitrary WLAN terminal. The method may further include: first and second WLAN terminal detection messages for the WLAN terminal from other first and second access point devices, respectively, wherein the first and second WLAN terminal detection messages are respectively used for the first and second WLAN terminal detection messages; And including information about the access point device, and selecting an access point device to hand over the WLAN terminal based on the information about the first and second access point devices.

Hereinafter, various embodiments will be described in detail with reference to the accompanying drawings.

1A is a conceptual diagram of a wireless mesh network system according to an embodiment. Referring to FIG. 1A, a wireless mesh network system 100 includes a plurality of mobile access points (MAPs) for providing a wireless access service to a WLAN terminal (STA) 110 and an STA 110. 120a-120e, a RADIUS server 130 that provides authentication services to the STA 110 and the MAP 120a-120e, and a plurality of gateways that provide connectivity with an external network, for example, the Internet 150. GW) 140a, 140b.

The STA 110 performs wireless communication by establishing an association with any one of the plurality of MAPs 120a-120e according to a WLAN protocol, for example, the IEEE 802.11 protocol. Since the IEEE 802.11 protocol is well known in the art, a detailed description thereof will be omitted, and the WLAN protocol may be any suitable WLAN protocol other than the IEEE 802.11 protocol.

The MAPs 120a-120e wirelessly connect not only with the STA 110 but also with other MAPs 120a-120e, and are referred to as WLAN protocol frames (eg, IEEE 802.11 frames, hereinafter referred to as "frames") associated with the STA 110. To route to the appropriate location. The MAPs 120a-120e may operate in a specific radio frequency band and provide a radio access service to the STA 110 through one or more channels that do not overlap each other. In one embodiment, when operating in the 2.4 GHz band, the MAP 120a-120e may provide a radio access service to the STA 110 through three channels in which frequency bands do not overlap each other. In another embodiment, when operating in the 5GHZ band, the MAP 120a-120e may perform wireless communication with the STA 110 through 12 channels in which frequency bands do not overlap each other.

FIG. 1B is a partially enlarged view of the STA and first to third MAPs shown in FIG. 1A. Referring to FIG. 1B, the MAPs 120a-120c provide a plurality of channels including at least one normal channel and one overhearing channel. The normal channel is used for establishing a connection with the STA 110 and transmitting / receiving a general WLAN protocol frame. The eavesdropping channel is used for detecting the STA 110 connected with other MAPs 120a-120c. In the case of FIG. 1B, the first to third MAPs 120a to 120c use the normal channels a1 to a3 and the interception channels b1 to b3, respectively. The frequency bands of the normal channel a1 and the interception channel b1 are set not to overlap each other, and in the channels a2 and b2 and the channels a3 and b3, the normal channel and the interception channel are set not to overlap each other. Each MAP 120a-120c detects a frame of the STA 110 that performs wireless communication with another MAP 120a-120c by using a channel of the same frequency band as its own eavesdropping channel through its own eavesdropping channel. The MAP 120a-120c may periodically change the frequency band of its own eavesdropping channel. For example, when the MAPs 120a-120c operate in the 5GHZ band, the MAPs 120a-120c may sequentially use the remaining channels except for the channel used as the normal channel among the 12 channels as the eavesdropping channel. .

In addition, the MAPs 120a-120c may periodically broadcast beacon frames (eg, MAC PDUs defined in IEEE 802.11) over a normal channel. The beacon frame is used to inform the STA 110 performing wireless communication using the normal channel that the corresponding MAP 120a-120c is located adjacent to the beacon frame.

The STA 110 establishes a connection with the first MAP 120a through the a1 channel and transmits and receives a data frame, for example, an FTP data frame. The STA 110 performs a wireless communication with the first MAP 120a, and a region where the first to third regions overlap in the first coverage area of the first MAP 120a, that is, an overlapping region (or Handoff area). As the STA 110 enters the overlapping region and the distance between the second and third MAPs 120b and 120c is closer, the data frames transmitted by the STA 110 to the first MAP 120a are the second and the third. MAPs 120b and 120c are reached.

The second and third MAPs 120b and 120c respectively have the same a2 or b2 channel and a3 or b3 channel as the frequency band of the a1 channel that the STA 110 uses (i.e. A1 = a2 or a1 = b1 for the second MAP 120b, a1 = a3 or a1 = b3 for the third MAP 120c, and a data frame transmitted by the STA 110 to the first MAP 120a. Will be received. The second and third MAPs 120b and 120c receiving the data frame transmitted by the STA 110 to the first MAP 120a inform the first MAP 120a that the STA 110 has entered its own area. A handoff procedure of the STA 110 is initiated by sending a regional entry notification message (or WLAN terminal detection message), for example, by broadcasting IAPP-Come.notify.

As described above, the handoff initiated by the MAPs 120b and 120c is referred to as an Access Point Initiated Handoff (AP). However, when the frequency bands of the normal channels between adjacent cells are the same, inter-cell interference may occur. Accordingly, the frequency bands of the channels a1, a2, and a3 are often different from each other, and the AP initiated handoff is performed by the frequency band of the eavesdropping channel b2 or b3 of the MAPs 120b and 120c adjacent to the STA 110. It starts when it is the same as the band.

When the frequency bands of the channels a1, a2, and a3 are the same, the STA 110 enters a beacon frame transmitted by the second and third MAPs 120b and 120c through the a2 and a3 channels, respectively, as they enter the overlapping region. Receive via channel a1. The STA 110 selects any one of the second and third MAPs 120b and 120c, for example, the third MAP 120c according to the received signal strength (RSS) of the received beacon frames, A reassociation request frame is transmitted to the selected third MAP 120c to initiate a handoff procedure. The third MAP 120b transmits a reassocation response frame for the received reassociation request frame to the STA 110 and sends a regional entry notification message (for example, IAPP-Come.notify). Broadcast to perform the handoff procedure of the STA 110 in the first MAP (120a). As described above, the handoff initiated by the STA 110 is called a terminal initiated handoff.

FIG. 2A is a conceptual diagram of an AP initiated handoff of the wireless mesh network system shown in FIGS. 1A and 1B. Referring to FIG. 2A, the STA 110 is connected to the first MAP 120a through an a1 channel to transmit and receive an FTP data frame. Meanwhile, the second and third MAPs 120b and 120c monitor the data frames transmitted by the STA 110 through the b1 and b2 channels, respectively, and monitor whether the STA 110 has entered its own area. The second and third MAPs 120b and 120c may periodically change the frequency bands of the b1 and b2 channels in a predetermined order to monitor a larger number of STAs, respectively. As the STA 110 moves, the STA 110 enters an overlapping region where the first to third regions overlap. In this case, the second and third MAPs 120b and 120c respectively receive FTP data frames transmitted by the STA 110 to the MAP1 120a when the b1 and b2 channels belong to the same frequency band as the a1 channel. When the second and third MAPs 120b and 120c need an authentication procedure to associate with the STA 110, the second and third MAPs 120b and 120c exchange information required for authentication with the STA 110-for example, a MAC address or user information. The authentication procedure is performed with the RADIUS server 130. The authentication procedure is a well-known technology detailed in the IEEE 802.11 recommendation, for example, and thus the detailed description thereof will be omitted. The authentication procedure may be implemented using any suitable authentication procedure other than the IEEE 802.11 recommendation.

When the authentication procedure is completed, the second and third MAPs 120b and 120c respectively broadcast a regional entry notification message to inform the first MAP 120a that the STA 110 has entered its own domain. According to an embodiment, the transmission of the regional entry notification message may be performed by broadcasting IAPP-Come.notify, which is an IAPP message conforming to the IEEE 802.11f, according to the IEEE 802.11f IAPP protocol. In one embodiment, IAPP-Come.notify includes the MAC address of STA 110 and layer 2 information of MAPs 120b and 120c that transmit IAPP-Come.notify. The MAC address of the STA 110 may be included in a data frame transmitted by the STA 110. Layer 2 information of the MAPs 120b and 120c may include information about a basic service set ID (BSSID) and a normal channel of the MAPs 120b and 120c. In another embodiment, IAPP-Come.notify is currently present in the MAP 120b, 120c, information about the Quality of Service (QoS) supported by the MAPs 120b, 120c sending IAPP-Come.notify. The number of connected STAs (STA load) and / or the RSS of the data frame received from the first MAP 120a may be included.

The first MAP 120a is received through each zone entry notification message, and the data service currently performed by the STA 110 requires real-time processing according to the type of data included in the data frame transmitted and received with the STA 110. Determine whether or not the service. The STA 110 may perform an application layer service that may be temporarily delayed in transmitting and receiving data such as FTP or Internet search service, whereas the application layer service in which data should be transmitted and received in real time, such as VoIP or multimedia streaming service. You can also do For example, the data frame may include an IP header, which is a three-layer header, and a TCP or UDP header, which is a four-layer header, as a two-layer PDU among seven OSI layers. In general, the IP header contains a protocol ID that indicates the protocol used by the data transmitted by the data frame. For example, when the protocol ID of the IP header is UDP, when the UDP header is checked together to indicate the RTP protocol used for the VoIP service, the data transmitted by the data frame may be VoIP data. In addition, the TCP or UDP header includes a port number associated with the data. For example, if the UDP header number is 21, it can be seen that the data transmitted by the corresponding data frame is FTP data. The first MAP 120a determines whether a data service currently performed by the STA 110 is a service requiring real-time processing with reference to an IP header or a TCP / UDP header of a data frame transmitted and received with the STA 110.

As a result of the determination, when the data service currently performed by the STA 110 is not a service requiring real-time processing such as an FTP service, the first MAP 120a may transmit a regional status report request message to the STA 110 in a neighboring MAP. Broadcast to 120b-120e. In one embodiment, the transmission of the global status report request message may be performed by broadcasting a newly defined, IEEE 802.11f compliant IAPP-Come-report.request to the neighboring MAP 120b-120e according to the IEEE 802.11f IAPP protocol. Can be. The neighboring MAP, for example, the second to fifth MAPs 120b-120e that received the regional status report request message, transmits the regional status report response message to the first MAP 120a. For example, the global status report response message may be IAPP-Come-report.response newly defined in this embodiment and conforming to IEEE 802.11f. In one embodiment, the IAPP-Come-report.response may include the RSS of the data frame received from the STA 110, the MAC address of the STA 110, the STA load and QoS information of the MAP 120b-120e. .

The first MAP 120a receives the regional status report response message from each of the second to fifth MAPs 120b-120e, and handovers the STA 110 (that is, the STA 110). Selects an optimal MAP based on the RSS, STA load and / or QoS information included in the global status report response message. According to an embodiment of the present invention, the process of selecting the optimal MAP will be described in detail. The first MAP 120a may be a QoS condition required by a data service currently performed by the STA 110 based on QoS information. Select a MAP that satisfies the transmission bandwidth. The first MAP 120a multiplies each of the STA load and the RSS of the MAP that satisfies the QoS condition by a predetermined weight, and then adds the MAPs with the highest values to optimize the MAP having the highest value, for example, the third MAP 120c. Select with MAP. As the first MAP 120a broadcasts the regional status report request message to the neighbor MAPs 120b-120e and selects one of the neighbor MAPs 120b-120e, the candidate group of the MAP to be handed over is made larger. Handover to the appropriate MAP.

On the other hand, as a result of the determination, for example, if the data service currently performed by the STA 110 is a service requiring real-time processing such as an FTP service, the first MAP 120a may be the second and third MAPs 120b and 120c. The optimal MAP for handing over the STA 110 is determined according to the RSS of the regional entry notification message received from For example, an MAP with a large RSS may be selected as an optimal MAP. Rather than broadcasting a regional status report request message, the time delay can be reduced by selecting an optimal MAP directly from one of the MAPs that have transmitted the regional notification message.

The first MAP 120a transmits a MAP selection notification frame to the STA 110 to the STA 120. The MAP selection notification frame may be, for example, a Gratuitous Probe that is newly defined and conforms to the IEEE 802.11 MAC frame format according to one embodiment. The MAP selection notification frame includes information about normal channel information of the third MAP 120c (that is, a3) that the STA 110 can use to perform a handoff procedure (ie, a reconnection procedure) with the third MAP 120c. Information about a physical layer) of the third MAP 120c. The first MAP 120a may generate the MAP selection notification frame based on the information included in the regional status report response message.

When the STA 120a receives the MAP selection notification frame from the first MAP 120a, the STA 120a transmits a handoff start notification frame to the first and third MAPs 120a and 120c through the a1 and a3 channels, respectively. In one embodiment, the handoff start notification frame may be a Handoff Initiation newly defined in this embodiment and conforming to the IEEE 802.11 MAC frame format. The handoff start notification frame may include a BSSID of the first MAP 120a and a BSSID of the third MAP 120a. Upon receiving the handoff start notification frame, the first MAP 120c receives and buffers a data frame destined for the STA 110 from another MAP 120b-120e.

Meanwhile, the STA 120a that has transmitted the handoff start notification frame releases a connection with the first MAP 120a and transmits a reassociation request to the third MAP 120c to perform a handoff procedure or reconnection. Initiate the procedure. The third MAP 120c receives the handoff start notification frame and the reassociation request, transmits a reassociation response to the reassociation request to the STA 110, and performs the reassociation procedure with the STA 110. To complete.

The third MAP 120c that has completed the reconnection procedure transmits a movement completion notification message to the first MAP 120a informing that the handoff to the third MAP 120c is completed. For example, the movement completion notification message may be IAPP-Move.notify newly defined in this embodiment and conforming to IEEE 802.11f. Receiving the movement completion notification message, the first MAP 120a transmits a movement completion response message for the movement completion notification message to the third MAP 120c. For example, the mobile completion response message may be IAPP-Move.response newly defined in this embodiment and conforming to IEEE 802.11f. In addition, the first MAP 120a transmits a data transfer message including the buffered data frame to the third MAP 120c. For example, the data transfer message may be IAPP-Packet.forward newly defined in this embodiment and conforming to IEEE 802.11f.

The third MAP 120c receives the data transfer message, extracts the buffered data frame, and transmits the extracted data frame to the STA 110. Accordingly, after the STA 110 releases the connection with the first MAP 120a, the STA 110 receives the data frame destined for the STA 110 received by the first MAP 120a without being lost. Thus, problems such as session dropout or frame loss and delay can be prevented. After receiving the buffered data frame through the third MAP 120c, the STA 110 receives frame data subsequent to the data frame to normally perform wireless communication.

FIG. 2B is a conceptual diagram of a terminal initiated handoff of the wireless mesh network system shown in FIGS. 1A and 1B. First, detailed descriptions of the same parts as those shown in FIG. 2A are omitted from the contents shown in FIG. 2B, and the following description will be mainly given based on differences between the embodiments shown in FIGS. 2B and 2A. Referring to FIG. 2B, the STA 110 is connected to the first MAP 120a through an a1 channel to transmit and receive an FTP data frame. Meanwhile, the second and third MAPs 120b and 120c periodically broadcast beacon frames through a2 and / or b2 and a3 and / or b3 channels, respectively.

As the STA 110 moves, the STA 110 enters an overlapping region where the first to third regions overlap. At this time, when the a1 channel of the STA 110 has the same frequency band as any one of the a2 or b2 channels of the second MAP 120b and the a3 or b3 channel of the third MAP 120c, the STA 110 ) Receive the beacon frame from the second and third MAP (120b, 120c), respectively. The STA 110 transmits a reassociation request to the MAP, for example, the third MAP 120c, which broadcasts the RSS high beacon frame among the beacon frames. Receiving the reconnection request, the third MAP 120c may use the RADIUS server 130 and the STA 110 using the user login ID and password of the STA 110 or the MAC address of the STA 110 before the reconnection establishment if necessary. Perform the authentication procedure of.

When the authentication procedure is completed, the third MAP 120c broadcasts a regional entry notification message to inform the first MAP 120a that the STA 110 has entered its own regional area. The subsequent procedure is the same as the procedure described with reference to FIG. 2A and will not be described in detail below.

Hereinafter, the configuration of IEEE 802.11f IAPP messages and IEEE 802.11 MAC frames described with reference to FIGS. 2A and 2B will be described in detail. First, IAPP messages newly defined and compliant with IEEE 802.11f according to an embodiment of the present invention will be described.

* IAPP-Come.notify

category Sub-field Remarks IAPP version - Display IAPP Version of Corresponding IAPP Message command IAPP-Come.notify - Identifier - - Length - Indicate the length of this IAPP message       data MAC address MAC address of the STA associated with the MAP to be handed off  RSS RSS of data frames received from the STA associated with the MAP to be handed off  STA load The number of STAs associated with the MAP sending IAPP-Come.notify  QoS Information QoS supported by MAP sending IAPP-Come.notify  Tier 2 Information Contains information used to create gratuitous probes (see Gratuitous Probe Table)

IAPP-Come.notify is a message for notifying that the STA has entered its own area by transmitting to the MAP currently connected to the STA when the MAP recognizes that a new STA has entered its own area. IAPP-Come.notify includes an IAPP version, command, identifier, length, and data items, which may be subdivided back into MAC address, RSS, STA load, QoS information, and layer 2 information items. The MAP to be handed off is a MAP currently connected with the STA.

* IAPP-Come-report.request

category Sub-field Remarks IAPP version - Display IAPP Version of Corresponding IAPP Message command IAPP-Come-report.request  Identifier  - Instructs the IAPP-Come-report.response corresponding to the IAPP-Come-report.request Length - Indicate the length of this IAPP message data MAC address MAC address of the STA included in the data frame

IAPP-Come-report.request is a message that the MAP to be handed off broadcasts to an adjacent STA in order to secure a candidate group of MAPs to be handed over (ie, MAPs to which the STA is newly connected) to the STA currently connected to it. .

* IAPP-Come-report.response

category Sub-field Remarks IAPP version - Display IAPP Version of Corresponding IAPP Message command IAPP-Come-report.response -  Identifier  - Instructs the IAPP-Come-report.response corresponding to the IAPP-Come-report.request Length - Indicate the length of this IAPP message        data MAC address MAC address of the STA associated with the MAP to be handed off  RSS RSS of data frames received from the STA associated with the MAP to be handed off  STA load The number of STAs associated with the MAP sending IAPP-Come.notify  QoS Information QoS supported by MAP sending IAPP-Come.notify  Tier 2 Information Contains information used to create gratuitous probes (see Gratuitous Probe Table)

IAPP-Come-report.request is a message in which the neighbor MAP that has received the IAPP-Come-report.response responds with the MAP to be handed off. Except for the command entry, the configuration is the same as for IAPP-Come.notify.

* IAPP-Packet.forward

category Sub-field Remarks IAPP version - Display IAPP Version of Corresponding IAPP Message command IAPP-Packet.forward - Identifier - - Length - Indicate the length of this IAPP message   data Sequence number Display order of IAPP-Packet.forward  Subsequent message indicators Indication of presence of IAPP-Packet.forward following the corresponding IAPP-Packet.forward Data frames Data frames buffered in the MAP to be handed off

IAPP-Packet.forward is the buffered frame data to the MAP to be handed over when the MAP to be handed over completes movement after the MAP to be handed off buffers and stores a data frame destined for the STA. This is a message for sending. The buffered frame data may be divided into predetermined lengths and transmitted to a plurality of IAPP-Packet.forwards. At this time, the order of IAPP-Packet.forward is indicated by the sequence number. Meanwhile, whether the corresponding IAPP-Packet.forward is the last IAPP-Packet.forward for transmitting the buffered frame data is indicated by the subsequent message indicator.

Hereinafter, a look at MAC frames newly defined and compliant with IEEE 802.11 according to an embodiment.

Gratuitous Probe

category Sub-field Remarks  MAC header  - Contains MAC header information defined in IEEE 802.11, such as the BSSID of the MAP sending the Gratuitous Probe.       Frame bodybuilder Time stamp - Specification Information Includes QoS information of MAP to be handed over to STA BSSID BSSID of the MAP to which the STA will be handed over Support rate Indicate the baud rate supported by the MAP to be handed over FH parameter set Physical layer information of MAP to be handed over DS parameter set Physical layer information of MAP to be handed over CF parameter set Physical layer information of MAP to be handed over FCS - CRC

The gratuitous probe is a frame used to transmit information about the MAP to be handed over to the STA, which is required for the MAP to be handed off to perform a handoff procedure. Items included in the above-described frame body are included in IAPP-Come.notify and IAPP-Come-report.response. The frequency hopping (FH) parameter set and the direct sequence (DS) parameter set are information related to a physical transmission scheme of the MAP to be handed over, and the CF (Coorination Function) parameter set is carrier sensing operation of the MAP to be handed over. Information about the method. The content of the items included in the above-described frame body is a well-known technology that is defined in detail in IEEE 802.11, and thus the detailed description thereof will be omitted. FCS stands for Frame Check Sequence, which stands for Frame Check Sequence, and CRC stands for Cyclic Redundancy Check. Both FCS and CRC are well known techniques known to those skilled in the art, and thus detailed descriptions are omitted.

* Handoff Initiation

category Sub-field Remarks  MAC header  - Contains MAC header information defined in IEEE 802.11, such as the MAC address of the STA that sends the Handoff Initiation.  Frame bodybuilder Time stamp - Old BSSID BSSID of MAP Being Handed Off New BSSID BSSID of the MAP being handed over FCS - CRC

Handoff Initiation is a frame transmitted by the STA that receives the Gratuitous Probe to the MAP to be handed off and to the MAP to be handed over.

3 is a block diagram of a MAP according to an embodiment. Referring to FIG. 3, the MAP 300 includes a wireless communication unit 310 performing wireless communication with an STA and another MAP, a storage unit 320 storing a data frame, and a controller 330 performing a handoff procedure for the STA. ).

The wireless communication unit 310 provides a plurality of channels including at least one normal channel and at least one interception channel to perform the wireless communication.

The storage 320 temporarily stores information generated while performing the wireless communication, such as an operating system program of the MAP 300, first layer (ie, physical layer) and second layer information, and the like. In particular, the storage unit 320 stores a data frame destined for the STA received through the normal channel of the wireless communication unit 310.

The controller 330 senses another STA, for example, the STA 110 connected to the first MAP 120a through the same frequency band as the interception channel through the interception channel, as shown in FIG. 1B. A WLAN terminal detection message (for example, IAPP-Come.notify) including information about 110 is transmitted to the first MAP 120a. The controller 330 may sequentially use the remaining channels except for the channel used as the normal channel among the plurality of channels provided by the wireless communication unit 310 as the eavesdropping channel. The controller 330 periodically transmits a beacon frame through the normal and / or interception channel, and includes a frame including information on the STA from the STA that has received the beacon frame, for example, a reassocation request frame. ), A WLAN terminal detection message is transmitted to the first MAP 120a. The WLAN terminal detection message may further include information about the MAP 300. In addition, the WLAN terminal detection message may include at least one of the information on the MAP (300), the RSS of the frame received from the first MAP (120a), STA load for the MAP (330) and QoS information. The information about the STA 110 may include a MAC address of the STA 110.

The control unit 330 transmitting the WLAN terminal detection message transmits a WLAN terminal report request message (eg, IAPP-Come-report.request) including the MAC address of the STA 110 from the first MAP 120a. Receive. The controller 330 detects the STA 110 once again through the normal or communication channel, and includes a WLAN terminal report response message (for example, IAPP-Come-) containing the same type of information as the WLAN terminal detection message. report.response) is transmitted to the first MAP 120a.

When the first MAP 120a selects the MAP 330 as the MAP to handover, the controller 330 selects a handoff start notification frame (eg, a handoff initiation) and a reconnection request frame from the STA 110. Receive sequentially over the channel. Upon receiving the reconnection request frame, the controller 330 transmits a reconnection response frame to the STA 110 through the normal channel to establish a reconnection. Accordingly, the STA 110 is handed over to the MAP 330. The control unit 330 transmits a movement completion notification message (for example, IAPP-Move.notify) to the first MAP 120a, and a movement completion response message (for example, IAPP-Move) from the first MAP 120a. .response). In one embodiment, the mobile completion notification message and the mobile completion response message includes context information to be exchanged between MAPs when reconnecting according to IEEE 802.11. Since the context information is defined in detail in IEEE 802.11, a detailed description thereof will be omitted.

Upon receiving the movement completion response message, the controller 330 receives a data frame destined for the STA 110 buffered in the first MAP 120a from the first MAP 120a and transmits the data frame to the STA 110. The controller 330 transmits / receives a frame subsequent to the buffered data frame with the STA 110 according to a general WLAN transmission / reception scheme.

While reconnecting with the STA 110 and normally transmitting and receiving data frames, the controller 330 may receive a WLAN terminal detection message for the STA 110 from another MAP, for example, the third MAP 120c. Can be. Since the operation of the controller 330 is the same as the operation of the first MAP 120a described with reference to FIGS. 2A and 2B, a detailed description thereof will be omitted below.

Receiving a MAP selection notification frame (eg, a gratuitous probe) from the first MAP 120a, the STA 110 connected to another MAP, for example, the first MAP 120a and the interception channel, is connected to the STA 110. The WLAN terminal detects the signal through the eavesdropping channel and transmits a WLAN terminal detection message including information on the STA 110 to the first MAP 120a.

4 is a flowchart illustrating a method for detecting an STA of a third MAP according to an embodiment. First, the third MAP 120c may perform wireless communication through N non-overlapping channels. Referring to FIG. 4, the third MAP 120c sets the interception channel number n to 0 (S400) and sets the nth channel as the interception channel (S410). Thereafter, the third MAP 120c starts a timer (S420). In step S430, the third MAP 120c determines whether the STA 110 has received a frame transmitted by the STA 110 to a neighbor MAP, for example, the first MAP 120a, through the interception channel. In operation S430, when the STA 110 receives the frame transmitted to the first MAP 120a, the third MAP 120c extracts the MAC address of the STA 110 included in the received frame. In addition, the third MAP 120c broadcasts a regional entry notification message (eg, IAPP-Come.notify) including the extracted MAC address of the STA 110 (S450) and terminates the procedure.

As a result of determining in step S430, when the STA 110 does not receive a frame transmitted to the first MAP 120a, the third MAP 120c determines whether the timer has expired (S460). If it is determined in step S460 that the timer has expired, the process moves to step S430. As a result of the determination in step S460, when the timer has not expired, the third MAP 120c sets the value of n plus 1 to n (S470) and whether n is equal to or less than the total number N of channels. Determine (S480). As a result of the determination of step S480, when n is equal to or less than the total number N of channels, the process moves to step S410. As a result of the determination of step S480, when n is greater than the total number of channels N, the process moves to step S400.

5 is a flowchart illustrating a handoff method of a first MAP according to an embodiment. Referring to FIG. 5, the first MAP 120a receives a regional entry notification message (eg, IAPP-Come.notify) from the second and third MAPs 120b and 120c (S500), and the STA 110. In step S505, it is determined whether or not the transmission and reception of the data frame to be transmitted and received may be temporarily delayed. If it should not be temporarily delayed as a result of the determination in S505, one of the second and third MAPs 120b and 120c is selected as a new MAP to be handed over (S520), and the process moves to S525 to be described later.

As a result of the determination in S505, when temporarily delayed, the first MAP 120a broadcasts a regional status report request message (eg, IAPP-Come-report.request) (S510). In addition, the first MAP 120a receives a regional status report response message (for example, IAPP-Come-report.response) from neighboring MAPs (S515), and performs a new handover based on the regional status report response message. MAP is selected (S520). In step S525, the first MAP 120a transmits a MAP selection notification frame (eg, a gratuitous probe) to the STA 110, and sends a handoff start notification frame (eg, a handoff initiation) from the STA 110. It receives (S530). The first MAP 120a receives and buffers the data frame destined for the STA 110 from the neighbor MAP (S540). In step S545, the first MAP 120a receives a movement completion notification message (eg, IAPP-Move.notify) from the selected MAP, and moves a response message (eg, IAPP-Move) to the selected MAP. .response) is transmitted (S550). The first MAP 120a transmits a data transfer message (eg, IAPP-Packet.forward) including the buffered data frame to the selected MAP (S555) and terminates the procedure.

6 is a flowchart of a handoff method of a third MAP according to an embodiment.

Referring to FIG. 6, the third MAP 120c receives a handoff start notification frame (for example, Handoff Initiation) from the STA 110 (S600) and performs a handoff procedure with the STA 110 to perform an STA ( Reconnect with 110) (S610). Thereafter, the third MAP 120c transmits a movement completion notification message (for example, IAPP-Move.notify) to the first MAP 120a (S620), and then the movement completion response message from the first MAP 120a. (Eg, IAPP-Move.response) is received (S630). The third MAP 120c receives a data transfer message (eg, IAPP-Packet.forward) from the first MAP 120a (S650), and transmits the data frame included in the data transfer message to the STA 110. Transmit (S650) and end the procedure.

Although the methods have been described through specific embodiments, the methods may also be embodied as computer readable code on a computer readable recording medium. Computer-readable recording media include all kinds of recording devices that store data that can be read by a computer system. Examples of computer-readable recording media include ROM, RAM, CD-ROM, magnetic tape, floppy disks, optical data storage devices, and the like, which are also implemented in the form of carrier waves (for example, transmission over the Internet). Include. The computer readable recording medium can also be distributed over network coupled computer systems so that the computer readable code is stored and executed in a distributed fashion. In addition, functional programs, codes, and code segments for implementing the above embodiments can be easily inferred by programmers in the art to which the present invention belongs.

In the above described the present invention with reference to the embodiments shown in the drawings for clarity, but this is merely exemplary, those skilled in the art that various modifications and equivalent other embodiments are possible from this. Will understand. Therefore, the true technical protection scope of the present invention will be defined by the appended claims.

According to the above embodiments, there is an effect that can provide a method and apparatus for detecting an STA to be handed off effectively or a neighbor MAP to be handed over in a wireless mesh network. In addition, it is possible to provide a handoff method and apparatus in which a frame transmitted to an STA is not lost while a handoff is performed, and a previously established session is not disconnected.

Further, according to the embodiments, in consideration of the traffic load and the quality of service (QoS) of the MAP to be reconnected, a handoff method and apparatus for reconnecting to the appropriate MAP according to the type of data frame currently being transmitted and received by the STA There is an effect that can be provided.

Claims (30)

As an access point device, A wireless communication unit providing an eavesdropping channel, and Detecting a wireless LAN terminal associated with another access point device through the same frequency band as the interception channel through the eavesdropping channel, and receiving another WLAN terminal detection message including information on the wireless LAN terminal. Control to send to point Access point device comprising a. The method of claim 1, The wireless communication unit provides a plurality of channels including at least one normal channel, The controller sequentially sets the remaining channels except for the normal channel among the plurality of channels as the eavesdropping channel. Access point device. The method of claim 1, The wireless communication unit provides at least one normal channel, The control unit receives a handoff start notification frame from the WLAN terminal through the normal channel and reconnects with the WLAN terminal through the normal channel. Access point device. As an access point device, A wireless communication unit providing at least one normal channel and / or an eavesdropping channel, and A control unit periodically transmitting a beacon frame on the interception channel and / or the normal channel Access point device comprising a. The method of claim 4, wherein When the control unit receives the frame from the WLAN terminal receiving the beacon frame, the controller transmits a WLAN terminal detection message including information on the WLAN terminal to another access point device connected to the WLAN terminal to the other access point. doing Access point device. The method according to claim 1 or 5, The WLAN terminal detection message further includes information about the access point device. Access point device. The method according to claim 1 or 5, The information on the WLAN terminal includes the MAC address of the WLAN terminal, The information on the access point device includes at least one of the RSS of the frame received from the detected WLAN terminal, the information on the access point device WLAN terminal load and QoS information. Access point device. The method of claim 5, The control unit receives a handoff start notification frame from the WLAN terminal through the normal channel and reconnects to the WLAN terminal through the normal channel. Access point device. The method according to claim 3 or 8, The control unit receives a reconnection request frame from the WLAN terminal through the normal channel, and transmits a reconnection response frame for the reconnection request frame to the WLAN terminal to establish the reconnection. Access point device. The method according to claim 3 or 8, The controller transmits a movement completion notification frame to the other access point device after establishing the reconnection, receives a data frame destined for the WLAN terminal buffered by the other access point, from the other access point device. Transmitting to the WLAN terminal through a normal channel Access point device. An access point apparatus for establishing wireless communication by connecting to one or more WLAN terminals, Wireless Communications Department, Storage, and Receives a handoff start notification frame from the WLAN terminal to release the connection with the WLAN terminal, receives a frame destined for the WLAN terminal from another device, buffers the storage unit, and stores the WLAN. Control unit for transmitting the buffered frame to another access point device reconnected with the terminal Access point device comprising a. The method of claim 11, The control unit transmits the buffered frame to another access point device reconnected with the WLAN terminal when receiving the movement completion notification frame from the other access point device. Access point device. An access point apparatus for establishing wireless communication by connecting to one or more WLAN terminals, A wireless communication unit for receiving a WLAN terminal detection message for each of the WLAN terminals from a plurality of different access point devices, wherein each WLAN terminal detection message includes information on a corresponding access point device; and A control unit for selecting an access point device to handover the WLAN terminal based on information on the access point device included in each WLAN terminal detection message; Access point device comprising a. The method of claim 13, The controller, upon receiving the WLAN terminal detection message, broadcasts a WLAN terminal report request message for the WLAN terminal through the wireless communication unit, and includes a plurality of other access point devices and / or a plurality of other access point devices. A wireless LAN terminal report response message for each of the wireless LAN terminal report request messages, wherein each of the wireless LAN terminal report response messages includes information on a corresponding access point device, and transmit the wireless LAN terminal report response message to the wireless terminal, Selecting an access point device for handing over the WLAN terminal based on information on the access point device included in the LAN terminal report response message; Access point device. The apparatus of claim 13, wherein the information about the access point device includes at least one of RSS of a frame received from the detected WLAN terminal, WLAN terminal load and QoS information for the access point device. Access point device. The method of claim 13, The control unit transmits an access point selection notification frame indicating the selected access point device to the WLAN terminal through the wireless communication unit. Access point device. A method for detecting a WLAN terminal of an access point device, Setting an interception channel, and Detecting a wireless LAN terminal associated with another access point device through the same frequency band as the interception channel through the interception channel, WLAN terminal detection method comprising a. The method of claim 17, Transmitting a WLAN terminal detection message including information on the WLAN terminal to the other access point; WLAN terminal detection method further comprising. The method of claim 17, Setting at least one normal channel, and Receiving a handoff start notification frame from the WLAN terminal through the normal channel and reconnecting with the WLAN terminal through the normal channel; WLAN terminal detection method further comprising. A method for detecting a WLAN terminal of an access point device, Setting at least one normal channel and / or an intercepting channel, Periodically transmitting a beacon frame on the interception channel and / or the normal channel, and Detecting the WLAN terminal by receiving a frame from the WLAN terminal receiving the beacon frame WLAN terminal detection method comprising a. The method of claim 20, Transmitting a WLAN terminal detection message including information about the WLAN terminal to another access point device connected to the WLAN terminal to the other access point; WLAN terminal detection method further comprising. The method of claim 21, Receiving a handoff start notification frame from the WLAN terminal through the normal channel; And Establishing a reconnection with the WLAN terminal through the normal channel; WLAN terminal detection method further comprising. The method of claim 19 or 22, The step of establishing the reconnection Receiving a reconnection request frame from the WLAN terminal through the normal channel, and Establishing a reconnection by transmitting a reconnection response frame for the reconnection request frame to the WLAN terminal; WLAN terminal detection method comprising a. The method of claim 19 or 22, After the step of establishing the reconnection, Transmitting a movement completion frame to the other access point device; Receiving a data frame destined for the WLAN terminal buffered at the other access point from the other access point apparatus, and Transmitting the received data frame to the WLAN terminal through the normal channel WLAN terminal detection method further comprising. A handoff method of an access point device for establishing wireless communication by establishing a connection with an arbitrary WLAN terminal, Receiving a handoff start notification frame from the WLAN terminal; Releasing the connection with the WLAN terminal; Receiving a frame destined for the WLAN terminal from any other device; Buffering the received frame, and Transmitting the buffered frame to another access point device reconnected with the WLAN terminal Handoff method of the access point device comprising a. The method of claim 25, Transmitting the buffered frame Receiving a movement completion frame from the other access point apparatus, and Transmitting the buffered frame to another access point device reconnected with the WLAN terminal Handoff method of the access point device comprising a. A handoff method of an access point device for establishing wireless communication by establishing a connection with an arbitrary WLAN terminal, First and second WLAN terminal detection messages for the WLAN terminal from other first and second access point devices, respectively-The first and second WLAN terminal detection messages are respectively the first and second access point devices Includes information about-receiving, and Selecting an access point device for handing over the WLAN terminal based on the information on the first and second access point devices; Handoff method of the access point device comprising a. The method of claim 27, The information on the access point device includes at least one of RSS of a frame received from the detected WLAN terminal, WLAN terminal load and QoS information for the access point device. Method for handoff of an access point device. The method of claim 27, Transmitting an access point selection notification frame indicating the selected access point device to the WLAN terminal; The handoff method of the access point device further comprising. 28. A computer readable storage medium storing computer executable instructions for performing the method of any one of claims 17, 20, 25 or 27.

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