WO2009057930A2

WO2009057930A2 - Method for handover in wireless access system and gateway supporting the same

Info

Publication number: WO2009057930A2
Application number: PCT/KR2008/006354
Authority: WO
Inventors: Jinsoo Park
Original assignee: Posdata Co., Ltd.
Priority date: 2007-10-29
Filing date: 2008-10-28
Publication date: 2009-05-07
Also published as: KR20090043306A; WO2009057930A3; KR100934086B1

Abstract

A method for a handover and a gateway supporting the same is disclosed, which is capable of optimally establishing a data path between a current BS being in contact with an MS and a target ASN-GW as well as a data path between a serving ASN-GW and a home network on the handover between ASNs, wherein the method of the handover between ASNs in the wireless access system after a handover between a previous BS and a current BS by a movement of an MS, comprises, when an ASN-ASN handover request message and first SF Info are transmitted to a target ASN-GW from a serving ASN-GW, establishing a first data path between the target ASN-GW and a home network; transmitting a data path ID of the target ASN-GW to the serving ASN-GW; and establishing a second data path between the current BS and the target ASN-GW through the use of data path ID of the target ASN-GW.

Description

METHOD FOR HANDOVER IN WIRELESS ACCESS SYSTEM AND GATEWAY SUPPORTING THE SAME

Technical Field

[1] The present invention relates to a method for a handover in a wireless access system and a gateway supporting the same, and more particularly, a method for a handover to maintain an optimal data path for a handover between access service networks according to a movement of a mobile station, and a gateway supporting the same. Background Art

[2] Both Wibro technology and Worldwide Interoperability for Microwave Access

Forum Network Working Group (hereinafter, referred to as 'WiMAX NWG') concentrate their efforts on development and standardization of a network architecture for provision of a wireless Internet service of a mobile station based on IEEE 802.16 technology standard. Also, they regulate a handover procedure for stably maintaining a data receiving/transmitting operation when a mobile station moves out of a cell boundary of a corresponding base station connected, and enters a new cell boundary of another base station.

[3] FIG. 1 is a schematic view illustrating a handover procedure between access service networks (hereinafter, referred to as 'ASN') in a general wireless access system. Hereinafter, terms to be described are made based on Wibro, WiMAX Forum Network Architecture (Stage 3: Detailed Protocols and Procedures) Release 1.1.0, or IEEE 802.16 technology standard.

[4] The handover between the ASNs may be referred to as a Connectivity Service

Network (hereinafter, referred to as 'CSN') Anchored Mobility. At this time, the ASN is a network including an Access Service Network Gate Way (hereinafter, referred to as 'ASN-GW), and a Base Station (hereinafter, referred to as 'BS').

[5] The general wireless access system includes a Home Agent (hereinafter, referred to as 'HA') 102, and a plurality of ASNs, for example, two ASNs including a serving ASN-GW 106 and a target ASN-GW 108, wherein the HA 102 and the ASNs reside on a home network of a Mobile Station (hereinafter, referred to as 'MS') 114a. At this time, the serving ASN-GW 106 manages a previous BS 110 before the handover, and the target ASN-GW 108 manages a current BS 112.

[6] When the MS 114a moving from the BS 110 toward the current BS 112 enters the network of the current BS 110, there are requirements for newly establishing data paths from the HA 102 toward an MS 114b, and from the MS 114b toward the target ASN- GW 108. [7] Before changing the data path according to the handover between the ASNs, a data path is previously established between the current BS 112 and the MS 114b by the handover between the BSs, that is, ASN Anchored Mobility. With start of the handover between the ASNs, a data path 116 between the HA 102 and serving ASN-GW 106 through a service provider s network 104 is changed into a data path 118 between the HA 102 and the target ASN-GW 108.

[8] The data path 118 between the HA 102 and the target ASN-GW 108 corresponding a new Foreign Agent (hereinafter, referred to as 'FA can be established, but it does not define a method for changing a data path 122 between the serving ASN-GW 106 and the BS 110 before the handover into a data path 124 between the target ASN-GW 108 and the current BS 112.

[9] For enabling the current BS 112 to receive data from the HA 102 after the handover between the ASNs, data transmitted to the target ASN-GW 108 is unnecessarily transmitted to the serving ASN-GW 106, and is then routed to the current BS 112.

[10] Meanwhile, when the serving ASN-GW 106 transmits a request for the handover between the ASNs to the target ASN-GW 108, a sequential MIP registration procedure for data path set-up and FA relocation is performed. Then, the target ASN-GW 108 notifies the serving ASN-GW 106 that the data path between the HA 102 and the target ASN-GW 106 is set-up. However, since there is no acknowledgement related with whether or not the notice informing that the data path is established is transmitted appropriately to the serving ASN-GW 106, it is difficult to determine whether to retransmit the notice or not. Disclosure of Invention

Technical Problem

[11] Therefore, the present invention has been made in view of the above problems, and it is an object of the present invention to provide a method for a handover between ASNs and a gateway supporting the same, which is capable of preventing one or more problems of the related art.

[12] Another object of the present invention is to provide a method for a handover in a wireless access system under protocol environments of PMIPv6 as well as PMIPv4.

[13] Another object of the present invention is to provide a method for a handover in a wireless access system to decrease a packet-transmission delay on the handover between ASNs, and a gateway supporting the same.

[14] Another object of the present invention is to provide a method for a handover in a wireless access system, which is capable of preventing a packet from being lost when establishing a data path between a current BS and a target ASN-GW, and a gateway supporting the same. [15] A further object of the present invention is to provide a method for a handover in a wireless access system, which enables re-transmission of a response to a request for the handover between ASNs, and a gateway supporting the same. Technical Solution

[16] To achieve these objects and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, a method for a handover in a wireless access system, the handover between ASNs in the wireless access system after a handover between a previous BS and a current BS by a movement of an MS, comprises, when an ASN-ASN handover request message and first SF Info are transmitted to a target ASN-GW from a serving ASN-GW, establishing a first data path between the target ASN-GW and a home network; transmitting a data path ID of the target ASN-GW to the serving ASN-GW; and establishing a second data path between the current BS and the target ASN-GW through the use of data path ID of the target ASN-GW.

[17] In another aspect of the present invention, a method for a handover in a wireless access system, the handover between ASNs in the wireless access system after a handover between a previous BS and a current BS by a movement of an MS, comprises, when an ASN-ASN handover request message is transmitted to a target ASN-GW from a serving ASN-GW, establishing a first data path between the target ASN-GW and a home network; and establishing a second data path between the current BS and the target ASN-GW.

[18] In another aspect of the present invention, a method for a handover in a wireless access system, particularly in a current BS supporting a handover between ASNs after a handover between a previous BS and the current BS by a movement of an MS, comprises receiving both a data path ID of the target ASN-GW and a second data path set-up request message between the current BS and the target ASN-GW from the serving ASN-GW; establishing a second data path between the current BS and the target ASN-GW by using the data path ID of the target ASN-GW; and transmitting a second data path set-up completion message to the serving ASN-GW.

[19] In another aspect of the present invention, a method for a handover in a wireless access system, particularly in an ASN-GW performing an FA function of the wireless access system, comprises making an ASN-ASN handover request by the serving ASN- GW, the ASN-ASN handover request including MS Info and first SF Info connected with MS; transmitting a request for an MIP registration to an HA during a FA relocation procedure according to the ASN-ASN handover request; and receiving a response to the request for the MIP registration, and responding to the ASN-ASN handover request including second SF Info generated based on the first SF Info. [20] In another aspect of the present invention, a gateway supporting a handover between

ASNs performed after a handover between a previous BS and a current BS by a movement of an MS, comprises a DPF configured to receive first SF Info and a first ASN-ASN handover request message from a first ASN-GW, and to transmit a response message to the first ASN-ASN handover request message and second SF Info generated by using the first SF Info to the first ASN-GW; and an FA configured to transmit a request for registering a temporary address of the MS to a home network of the MS in response to the first ASN-ASN handover request message.

Advantageous Effects

[21] According to the present invention, it is possible to realize a method for a handover between ASNs and a gateway supporting the same.

[22] Also, it is possible to realize a method for a handover between ASNs in a wireless access system under protocol environments of PMIPvβ as well as PMIPv4.

[23] On the handover between the ASNs, a data path directly established between a current BS and a target ASNGW enables optimization of a routing path between an MS and a home network, and decrease of a packettransmission delay.

[24] On the handover between the ASNs, a temporary tunnel is generated during a procedure for setting up the BS and the target ASNGW, thereby decreasing a loss of packet transmitted from the home network during the procedure for establishing the data path between the BS and the target ASNGW.

[25] Also, the method for the handover according to the present invention enables retransmission of a response to a request for the handover between the ASNs, whereby a change of data path between the BS and the ASN-GW can be performed with high reliability, and FA relocation is cancelable. Brief Description of Drawings

[26] FIG. 1 is a schematic view illustrating a handover procedure between ASNs in a general wireless access system.

[27] FIG. 2 is a signal flow diagram illustrating a handover operation between ASNs in a wireless access system embodied as PMIPv4 according to one embodiment of the present invention.

[28] FIG. 3 is a signal flow diagram illustrating a handover operation between ASNs supported with a temporary tunnel in a wireless access system embodied as PMIPv4 according to another embodiment of the present invention.

[29] FIG. 4 is a schematic diagram illustrating a handover procedure between ASNs supported with a temporary tunnel in a wireless access system embodied as PMIPv4 shown in FIG. 3.

[30] FIG. 5 is a signal flow diagram illustrating a signal flow diagram illustrating a handover operation between ASNs in a wireless access system embodied as PMIPvβ according to another embodiment of the present invention.

[31] FIG. 6 is a diagram illustrating a gateway supporting a handover between ASNs in a wireless access system embodied as PMIPv4 according to one embodiment of the present invention. Best Mode for Carrying out the Invention

[32] Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.

[33] Before describing preferred embodiments of the present invention, terms to be used therein will be briefly explained as follows.

[34] A network architecture supporting a Mobile IP (hereinafter, referred to as 'MIP') includes a HA, a FA, and an MS. For operation of the MIP, the following functions are necessarily required.

[35] First, an agent discovery function relates to a method for determining whether or not the MS is currently connected with its own home network or a foreign network. When the MS moves to another network, the movement of MS is recognizable through this method.

[36] A registration function provides a flexible mechanism such that the MS is stably provided with service identical to that of the HA through the use of current location information notified to the HA when it is recognized that the MS is moved to another network.

[37] A proxy mobile IP (hereinafter, referred to as 'PMIP') technology means that a network entity instead of the MS performs an MIP registration procedure. When there is a need to change an IP address (for example, Care of Address) of the MS on an initial network access or handover, an MIP registration message is transmitted to an ASN-GW including an FA function, instead of the MS. After receiving the MIP registration message, the ASN-GW performs the MIP registration procedure by transmitting the MIP registration message to the HA.

[38] If a home address of the MS is generated initially by the network entity performing

PMIP and MIP registration procedure instead of the MS, there is no requirement for directly changing the IP address of the MS even though the MS is moved to a new network included in another subnet, that is, network included in another FA.

[39] An ASN is a group of network functions providing a wireless access to wireless access system subscribers, wherein the ASN includes a BS and the ASN-GW. The ASN performs a network discovery function, a network selection function, a transmission function for a Layer- 3 connection set-up of the MS, and a radio resource management function.

[40] The ASN-GW is located within the ASN. The ASN-GW performs an FA function of

MIP, a data path function (hereinafter, referred to as 'DPF'), DHCP relay/proxy functions, an ASN radio resource management function, a location management function, or a paging function. At needed, these functions may be selectively added.

[41] For supporting a mobility of the MS, the FA is located within the ASN-GW, and the

FA is a router connected with the network different from the home network. The FA transmits a packet received from the HA to the MS. For supporting the mobility of the MS, the HA is located within a CSN, wherein the HA transmits data, received from a corresponding node being in communication with the MS, to the FA.

[42] A Care of Address (hereinafter, referred to as 'CoA') is a temporary address when the

MS connects to another access router or ASN. Especially, FA-CoA corresponding to the CoA of FA is provided through the use of agent advertisement message by the FA, wherein an IP address of FA is typically used for FA-CoA.

[43] Hereinafter, a method for a handover according to the present invention and a gateway supporting the same will be explained with reference to the accompanying drawings.

[44] FIG. 2 is a signal flow diagram illustrating a handover operation between ASNs in a wireless access system embodied as PMIPv4 according to one embodiment of the present invention.

[45] As shown in FIG. 2, the wireless access system includes an MS 202, a current BS

204, a serving ASN-GW 206 performing a FAl function in an ASNa, a target ASN- GW 208 performing a FA2 function in an ASNb, a PMIP client 210 performing a PMIPv4(Proxy Mobile IPv4) registration procedure, and an HA 212 included in a home network of the current MS 202.

[46] According as the handover occurs with a movement of the MS 202, the MS 202 is connected to the target ASN-GW 208 of the ASNb instead of the serving ASN-GW 206 of the ASNa. Before generating a change in data path according to the handover between the ASNs, that is, CSN Anchored Mobility, a data path between the current BS 204 and the MS 202 is firstly established by the handover between the BSs, that is, ASN Anchored Mobility.

[47] Accordingly, before the handover between the ASNs, the data path between the

ASN-GW and the BS is established by a data path 262 between the serving ASN-GW 206 and the current BS 204, and the data path between the ASN-GW and the HA 212 is established by a data path 272 between the serving ASN-GW 206 functioning as the FAl and the HA 212.

[48] The handover process between the ASNs will be explained in detail. In order to establish the data path between the ASN-GW and the HA 212 by the data path between the target ASN-GW 208 corresponding to the FA2 (hereinafter, referred to as 'first data path') and the HA 212 or perform an FA relocation, the target ASN-GW 208 transmits an ASN-ASN handover trigger message (hereinafter, referred to as 'Anchor_DPF_HO_Trigger') to the serving ASN-GW 206 in step S222.

[49] At this time, an entity initially trying the FA relocation may be the serving ASN-GW

206. Thus, since the serving ASN-GW 206 is capable of trying the FA relocation in the next step S224, the step for initially trying the FA relocation by the target ASN-GW 208 may be a selective step.

[50] Next, the serving ASN-GW 206 transmits an ASN-ASN handover request message

(hereinafter, referred to as 'Anchor_DPF_HO_Req') to the target ASN-GW 208 in step S224. The Anchor_DPF_HO_Req includes FAl-CoA corresponding to a CoA of the serving ASN-GW 206, DHCP information, and service flow information (hereinafter, referred to as 'SF Info') of the serving ASN-GW 206, wherein these information may be included in type of Type Length Value (hereinafter, referred to as 'TLV).

[51] The Anchor_DPF_HO_Req according to one embodiment of the present invention may have TVLs of authenticator ID, FAl-CoA, and Anchor MM context including DHCP-related information. As these TLVs are transmitted to the target ASN-GW 208, the target ASN-GW 208 and the PMIP client 210 can prepare an MIP registration procedure in the HA 212.

[52] Especially, in the case of the present invention, first SF Info corresponding to the SF

Info of the serving ASN-GW 206 or MS Info including the first SF Info is included as the TVL of the Anchor_DPF_HO_Req, and is transmitted together with the Anchor_DPF_HO_Req.

[53] This is to notify the target ASN-GW 208 of all SF Info possessed by the MS 202.

The first SF Info includes sub-TLVs, wherein the sub-TLVs include SF ID corresponding to an SF Identifier generated by the serving ASN-GW 206, Direction corresponding to information related with whether an SF type is an uplink type or a downlink type, and Data Path Info corresponding to information for maintaining the data path.

[54] At this time, downlink SF Info of the first SF Info includes a sub-TLV corresponding to Data Path Info of the current BS 204, wherein the Data Path Info includes sub-TLVs for Tunnel Endpoint and Data Path ID. Thus, the downlink SF Info can be used for establishing the data path between the current BS 204 and the target ASN-GW 208 (hereinafter, referred to as 'second data path').

[55] The Data Path ID, which is among the sub-TLVs of the Data Path Info, corresponds to a Data Path Identifier, for example, GRE Key. Also, the Tunnel Endpoint, which is among the sub-TLVs of the Data Path Info, may be an IP address of a channel recipient. Accordingly, the target ASN-GW 208 can be aware of the GRE Key of the current BS 204 and the IP address of the current BS 204 through the use of first SF Info.

[56] For the FA relocation, the target ASN-GW 208 transmits an FA relocation request message (hereinafter, referred to as 'Anchor_DPF_Relocate_Req') to the PMIP client 210 in step S226. This message includes both FAl-CoA and FA2-CoA, wherein the FAl-CoA corresponds to the CoA of serving ASN-GW 206, and the FA2-CoA corresponds to the CoA of target ASN-GW 208.

[57] Then, the PMIP client 210 checks whether or not the received FAl-CoA is identical to its own database information, generates an FA registration request message (hereinafter, referred to as 'FA_Register_Req'), and transmits the generated FA_Register_Req to the target ASN-GW 208 in step S228.

[58] The FA_Register_Req may include a TLV of Registration Request (hereinafter, referred to as 'RRQ'). At this time, the RRQ is a format defined in RFC 3344. Also, the RRQ has FA2-CoA in a CoA field. Also, the FA_Register_Req including an FA-HA MIP Key used for a mobility authentication extension for the MS enables the FA2-CoA registration in the HA 212.

[59] For the MIP registration of the MS, the target ASN-GW 208 transmits the RRQ received through the FA_Register_Req to the HA 212 in step S230. According as the HA 212 transmits a Registration Reply (hereinafter, referred to as 'RRP'), the new MIP registration is notified to the target ASN-GW 208 in step S232.

[60] Then, the target ASN-GW 208 transmits an FA registration completion response message (hereinafter, referred to as 'FA_Register_Rsp') including the RRP received from the HA 212 to the PMIP client 210, and the PMIP client 210 records the FA2 as the new FA in its own database in step S234.

[61] Next, the PMIP client 210 transmits an FA relocation completion response message

(hereinafter, referred to as 'Anchor_DPF_Relocate_Rsp') to the target ASN-GW 208 in step S236. At this time, the Anchor_DPF_Relocate_Rsp may be a format to notify whether the procedure for establishing the first data path succeeds or fails. This step S236 may be selectively included. Through the aforementioned steps, a first data path 274 between the HA 212 and the target ASN-GW 208 is established.

[62] Next, the target ASN-GW 208 newly generates second SF Info based on the first SF

Info in step S238, wherein the second SF Info is SF Info of the target ASN-GW 208. At this time, sub-TLVs of the second SF Info may be identical to those of the first SF Info.

[63] In one embodiment of the present invention, downlink SF Info of the second SF Info can be used of the downlink SF Info of the first SF Info. This is because the current BS 204 is not changed on the handover between the ASNs after the handover between the BSs. Thus, the downlink SF Info of the first SF Info received from the serving ASN- GW 206 can be utilized for the downlink SF Info of the second SF Info.

[64] At this time, the second SF Info includes sub-TLVs related with information for maintaining the data path, for example, SF ID, Direction, and Data Path Info.

[65] Also, uplink SF Info of the second SF Info is generated based on the first SF Info, wherein the uplink SF Info includes sub-TLV such as the Data Path Info including the Data Path ID of the target ASN-GW 208. At this time, the Data Path ID of the target ASN-GW 208 may be the GRE Key of the target ASN-GW 208 as the Data Path ID corresponding to the sub-TLV of the Data Path Info.

[66] For establishing the second data path, the target ASN-GW 208 generates the Data

Path Info of the second SF Info to be transmitted to the current BS 204 through the serving ASN-GW 206, and more particularly, generates the GRE Key of the target ASN-GW 208 corresponding to a recipient of uplink SF of the second data path.

[67] According as the Data Path Info of the uplink SF Info of the second SF Info may include the sub-TLV of Tunnel Endpoint corresponding to the IP address of channel recipient, the IP address of target ASN-GW 208 may be included.

[68] Next, the target ASN-GW 208 transmits a first data path set-up completion message

(hereinafter, referred to as 'Anchor_DPF_HO_Rsp') to the serving ASN-GW 206 in step S240. The Anchor_DPF_HO_Rsp transmits the second SF Info as well as information related with whether the first data path set-up completion succeeds or fails. This is to transmit the second SF Info to the current BS 204 while using the serving ASN-GW 206 as a proxy, to thereby establish the second data path.

[69] If the Tunnel Endpoint is not included in the sub-TLVs of the uplink SF Info among the second SF Info transmitted together with the Anchor_DPF_HO_Rsp, the tunnel Endpoint is automatically designated as the IP address of the target ASN-GW 208 corresponding to the message transmitter.

[70] The aforementioned embodiment of the present invention discloses that all second

SF Info is transmitted. In a modified embodiment of the present invention, only the uplink SF Info of the second SF Info can be transmitted since the downlink SF Info of the second SF Info can be used of the first SF Info, and the current BS 204 is already aware of the first SF Info.

[71] Next, the serving ASN-GW 206 transmits a second data path set-up request message

(hereinafter, referred to as 'Path_Modification_Req') to the current BS 204 in step S242.

[72] The serving ASN-GW 206 functions as the proxy during the procedure for receiving the Anchor_DPF_HO_Rsp including the second SF Info from the target ASN-GW 208, and transmitting the Path_Modification_Req to the current BS 204. That is, the serving ASN-GW 206 functions as the proxy between the target ASN-GW 208 and the current BS 204 for transmission of the Data Path ID of the target ASN-GW 208.

[73] The Path_Modification_Req includes a TLV of Registration Type, wherein the

Path_Modification_Req may have MS Info or BS Info. At this time, the second SF Info received from the target ASN-GW 208 may be transmitted as a sub-TLV of MS Info or BS Info.

[74] For establishing the second data path, the current BS 204 updates the Data Path Info of uplink direction based on the second SF Info included in the received Path_Modification_Req in step S244. At this time, the IP address and GRE Key of the target ASN-GW 208 corresponding to the channel recipient can be used for the update of the current BS 204 through the use of Tunnel Endpoint and Data Path ID among the sub-TLVs of the Data Path Info included in the second SF Info.

[75] Accordingly, the current BS 204 corresponding to one end of the second data path can be aware of the GRE Key of the target ASN-GW 208 corresponding to the uplink direction recipient. Also, the target ASN-GW 208 corresponding to the other end of the second data path can be aware of the GRE Key of the current BS 204 corresponding to the downlink direction recipient through the use of first SF Info received in step S224. Thus, it is possible to definitely establish the second data path 264 between the target ASN-GW 208 and the current BS 204.

[76] Then, the current BS 204 transmits a second data path set-up completion message

(hereinafter, referred to as 'Path_Modification_Rsp') to the serving ASN-GW 206 in step S246. The Path_Modification_Rsp includes a TLV of Registration Type, which may include MS Info or BS Info. Then, the serving ASN-GW 206 deletes records related with the data path of the MS 202 to be unused from the received Path_Modif ication_Rsp .

[77] Then, the serving ASN-GW 206 transmits a second data path set-up completion acknowledgement message (hereinafter, referred to as 'Path_Moficiation_Ack') to the current BS 204 in step S248. The Path_Modification_Ack includes a TLV of Registration Type, which may include MS Info.

[78] Then, the serving ASN-GW 206 transmits a data path set-up completion recognition message (hereinafter, referred to as 'Anchor_DPF_HO_Ack') to the target ASN-GW 208 in step S250. This is to ensure that the serving ASN-GW 206 receives the Anchor_DPF_HO_Rsp, to thereby secure the second data path. Also, the Anchor_DPF_HO_Ack notifies that the serving ASN-GW 206 completes the proxy function for establishing the second data path.

[79] In one embodiment of the present invention, the target ASN-GW 208 operates a timer after transmitting the Anchor_DPF_HO_Rsp, so as to repetitively transmit the Anchor_DPF_HO_Rsp until receiving the Anchor_DPF_HO_Ack if Anchor_DPF_HO_Ack is not received from the serving ASN-GW 206 for a pre- determined time period (T ). Also, the target ASN-GW 208 can cancel the

Anchor_DPF_HO_Req

FA relocation based on whether or not the Anchor_DPF_HO_Ack is received.

[80] FIG. 3 is a signal flow diagram illustrating a handover operation between ASNs supported with a temporary tunnel in a wireless access system embodied as PMIPv4 according to another embodiment of the present invention.

[81] The temporary tunnel is temporarily generated between a serving ASN-GW 206 and a target ASN-GW 208, wherein the temporary tunnel is provided for a predetermined period, that is, until establishing a second data path between the target ASN-GW 208 and a current BS 204 after establishing a first data path between the target ASN-GW 208 and an HA 212.

[82] The temporary tunnel prevents a packet loss generated when the HA 212 is connected with the target ASN-GW 208, and the current BS 204 is connected with not the target ASN-GW 208 but the serving ASN-GW 206 for the procedure for establishing the second data path. That is, it is possible to minimize the packet loss between the MS 202 generated during the procedure for establishing the data path on a handover between ASNs, and a Corresponding Node (hereinafter, referred to as 'CN') being in communication with the MS 202.

[83] Referring to FIG. 3, when establishing the first data path and transmitting

Anchor_DPF_HO_Rsp corresponding to a first data path set-up completion message to the serving ASN-GW 206, a temporary tunnel corresponding a temporary data path between the serving ASN-GW 206 and the target ASN-GW 208 is generated in step S302.

[84] The temporary tunnel is maintained until the second data path is set-up. When

Anchor_DPF_HO_Ack corresponding to a data path set-up completion recognition message is transmitted to the target ASN-GW 208, that is, when there is nothing to worry about a packet loss, the temporary tunnel is removed in step S304.

[85] FIG. 4 is a schematic diagram illustrating a handover procedure between ASNs supported with a temporary tunnel in a wireless access system embodied as PMIPv4 shown in FIG. 3.

[86] When the handover between the ASNs occurs with a movement of the MS 202, the serving ASN-GW 206 transmits an ASN-ASN handover request message and first SF Info to the target ASN-GW 208. Also, a data path 272 between the HA 212 and the serving ASN-GW 206 is designated as a first data path 274 between the HA 212 and the target ASN-GW 208.

[87] On the procedure for receiving the Anchor_DPF_HO_Rsp and transmitting

Path_Modification_Rsp, the serving ASN-GW 206 functions as a proxy to transmit second SF Info generated in the target ASN-GW 208 to the current BS 204. At this time, the current BS 204 changes a data path 262 between the current BS 204 and the serving ASN-GW 206 into the first data path 264 through the use of Data Path ID of the target ASN-GW 208 included in the second SF Info. During this procedure, the temporary tunnel 302 is generated to prevent the packet loss, wherein the temporary tunnel 302 is provided for the predetermined period, that is, until completing establishing the second data path 264 after completing establishing the first data path. Thus, the procedure for establishing the data path on the handover between the ASNs is completed.

[88] FIG. 5 is a signal flow diagram illustrating a signal flow diagram illustrating a handover operation between ASNs in a wireless access system embodied as PMIPv6 according to another embodiment of the present invention.

[89] Hereinafter, following terms related with messages and TLVs are used to embody the

PMIPv6, and are defined for convenience of explanation. Thus, if the used terms perform the same function as terms defined in IETF and WiMAX Forum Network Architecture standardization, they are interchangeably used in the same meaning.

[90] As shown in the drawings, the wireless access system includes an MS 402, a current

BS 404, a serving ASN-GW 406 performing a function of Mobile Access Gateway 1 (hereinafter, referred to as 'MAGl') in an ASNa, a target ASN-GW 408 performing a function of Mobile Access Gateway 2 (hereinafter, referred to as 'MAG2') in an ASNb, a Proxy Mobile Agent (hereinafter, referred to as 'PMA') 410 performing a PMIPv6 registration procedure, and a Local Mobility Agent (hereinafter, referred to as 'LMA') 412 included in a home network of the MS 402.

[91] Before the handover between the ASNs, a data path between the ASN-GW and the

BS is established by a data path 462 between the serving ASN-GW 406 and the current BS 404, and a data path between the ASN-GW and the LMA 412 is established by a data path 472 between the serving ASN-GW 406 corresponding to the MAGl and the LMA 412.

[92] A procedure for establishing the data path on the handover between the ANSs will be explained as follows.

[93] In order to establish the data path between the ASN-GW and the LMA 412 by the data path between the target ASN-GW 408 corresponding to the MAG2 and the LMA 412 (hereinafter, referred to as 'first data path, or perform a proxy CoA relocation, the target ASN-GW 408 transmits an ASN-ASN handover trigger message (hereinafter, referred to as 'Anchor_DPF_HO_Trigger' to the serving ASN-GW 406 in step S422.

[94] At this time, an entity initially trying the proxy CoA relocation may be the serving

ASN-GW 406. Thus, since the serving ASN-GW 406 is capable of trying the proxy CoA relocation in the next step S424, the step for initially trying the proxy CoA relocation by the target ASN-GW 408 may be a selective step.

[95] Next, the serving ASN-GW 406 transmits an ASN-ASN handover request message (hereinafter, referred to as 'Anchor_DPF_HO_Req') to the target ASN-GW 408 in step S424. At this time, the Anchor_DPF_HO_Req includes a TLV, wherein the TLV includes first SF Info corresponding to SF Info of the serving ASN-GW 406, or MS Info including the first SF Info. At this time, TLVs for the first SF Info may be information necessary for maintaining the data path, for example, SF ID, Direction, and Data Path Info.

[96] At this time, the target ASN-GW 408 can be aware of all SF Info possessed by the

MS 402 through the first SF Info, a GRE Key of the current BS 404, and an IP address of the current BS 404.

[97] Then, the target ASN-GW 408 transmits a CoA relocation request message

(hereinafter, referred to as'Anchor_DPF_Relocate_Req') to the PMA 410 in step S426. This message may include a Proxy Home Address (hereinafter, referred to as 'pHoA').

[98] Thereafter, the PMA 410 transmits a PMIP6 handover request message (hereinafter, referred to as 'PMIP6_HO_Req') to the target ASN-GW 408 in step S428, whereby an MIP registration procedure is started by the PMA 410 and the target ASN-GW 408.

[99] Next, the target ASN-GW 408 transmits a Proxy Binding Update (hereinafter, referred to as 'PBU') message to the LMA 412 in step S430. At this time, the PBU message may include pHoA, and Proxy Care of Address (hereinafter, referred to as 'pCoA') of the target ASN-GW 408. Thus, the LMA 412 responds by a Proxy Binding Acknowledgement (hereinafter, referred to as 'PBA') message, to thereby notify the target ASN-GW 408 of the MIP registration in step S432.

[100] Then, the target ASN-GW 408 transmits a PMIP6 handover response message (hereinafter, referred to as 'PMIP6_HO_Rsp') to the PMA 410, and the PMA 410 records the target ASN-GW 408 of the MAG2 as the new proxy in its own database in step S434.

[101] Next, the PMA 410 transmits a CoA relocation completion response message

(hereinafter, referred to as 'Anchor_DPF_Relocate_Rsp') to the target ASN-GW 408 in step S436. At this time, the Anchor_DPF_Relocate_Rsp may be a format to notify whether the process for setting the first data path succeeds or fails. Through the aforementioned steps, the first data path 474 is established between the LMA 412 and the target ASN-GW 408.

[102] The target ASN-GW 408 newly generates second SF Info based on the first SF Info in step S438. In one embodiment of the present invention, downlink SF Info of the second SF Info may be used of the downlink SF Info of the first SF Info. At this time, the second SF Info may include sub-TLVs with information necessary for maintaining the data path, for example, SF ID, Direction, and Data Path Info.

[103] For setting the second data path, the target ASN-GW 408 generates the Data Path

Info of the second SF Info to be transmitted to the current BS 404 through the serving ASN-GW 406, and more particularly, generates the GRE Key of the target ASN-GW 408 corresponding to an uplink direction recipient of the second data path.

[104] Also, Data Path Info of uplink SF Info of the second SF Info includes a sub-TLV of Tunnel Endpoint corresponding to a channel recipient IP address, whereby the Data Path Info may include the IP address of the target ASN-GW 408.

[105] Next, the target ASN-GW 408 transmits a first data path set-up completion message (hereinafter, referred to as 'Anchor_DPF_HO_Rsp') to the serving ASN-GW 406 in step S440. At this time, the Anchor_DPF_HO_Rsp includes the second SF Info as well as information related with whether a completion of the first data path set-up succeeds or fails.

[106] If the Tunnel Endpoint is not included in the sub-TLVs of the uplink SF Info of the second SF Info transmitted together with the Anchor_DPF_HO_Rsp, the tunnel Endpoint is automatically designated as the IP address of the target ASN-GW 408 corresponding to the message transmitter.

[107] The aforementioned embodiment of the present invention discloses that all second SF Info is transmitted. In a modified embodiment of the present invention, only the uplink SF Info of the second SF Info can be transmitted since the downlink SF Info of the second SF Info can be used of the first SF Info, and the current BS 404 is already aware of the first SF Info.

[108] Next, the serving ASN-GW 406 transmits a second data path set-up request message (hereinafter, referred to as 'Path_Modification_Req') to the current BS 404 in step S442.

[109] The serving ASN-GW 406 functions as a proxy during the procedure for receiving the Anchor_DPF_HO_Rsp including the second SF Info, and transmitting the Path_Modification_Req. At this time, the Path_Modification_Req includes SF Info as TLV for transmission of the second SF Info.

[110] For establishing the second data path, the current BS 404 updates the Data Path Info of uplink direction based on the second SF Info included in the received Path_Modification_Req in step S444. At this time, the IP address and GRE Key of the target ASN-GW 408 corresponding to the channel recipient can be used for the update of the current BS 404 through the use of the Tunnel Endpoint and Data Path ID among the sub-TLVs of the Data Path Info included in the second SF Info.

[I l l] Accordingly, the current BS 404 corresponding to one end of the second data path can be aware of the GRE Key of the target ASN-GW 408 corresponding to the uplink direction recipient. Also, the target ASN-GW 408 corresponding to the other end of the second data path can be aware of the GRE Key of the current BS 404 corresponding to the downlink direction recipient through the use of first SF Info received in step S424. Thus, it is possible to definitely established the second data path 464 between the target ASN-GW 408 and the current BS 404.

[112] The current BS 404 transmits a second data path set-up completion message

(hereinafter, referred to as 'Path_Modification_Rsp') to the serving ASN-GW 406 in step S446. Then, the serving ASN-GW 406 receives the Path_Modification_Rsp, and deletes records related with the data path of the MS 202 to be unused from the received Path_Modification_Rsp. Thereafter, the serving ASN-GW 406 transmits a second data path set-up completion acknowledgement message (hereinafter, referred to as 'Path_Moficiation_Ack') to the current BS 404 in step S448.

[113] The serving ASN-GW 406 transmits a data path set-up completion recognition message (hereinafter, referred to as 'Anchor_DPF_HO_Ack') to the target ASN-GW 408 in step S450. This is to re-transmit the Anchor_DPR_HO_Rsp when the second data path is not generated according as the serving ASN-GW 406 is not capable of receiving the Anchor_DPF_HO_Rsp.

[114] As mentioned above, when the handover occurs between the ASNs, the serving

ASN-GW 406 transmits the ASN-ASN handover request message and first SF Info to the target ASN-GW 408; sets up the first data path; receives the

Anchor_DPF_HO_Rsp; and transmits the Path_Modification_Rsp in sequence. During this procedure, the serving ASN-GW 406 transmits the second SF Info generated in the target ASN-GW 408 to the current BS 404, whereby the second data path is established.

[115] FIG. 6 is a diagram illustrating a gateway supporting a handover between ASNs in a wireless access system embodied as PMIPv4 according to one embodiment of the present invention.

[116] As shown in FIG. 6, the gateway 502 supporting the handover between the ASNs includes a DPF 504, an FA 506, and a PMIP client 508. At this time, the gateway 502 includes an authentication unit (not shown) for managing procedures of authentication and subscriber access as ASN-GW; a DHCP processing unit (not shown) for managing procedures of DHCP detection, request, and release; or a paging control unit (not shown).

[117] The DPF 504 performs functions for generating, correcting and deleting both data path and service flow information.

[118] When the gateway 502 supporting the handover between the ASNs performs the serving ASN-GW function, the DPF 504 transmits the Anchor_DPF_HO_Req including the TLVs of the first SF Info of serving ASN-GW or the MS Info including the first SF Info to the target ASN-GW (not shown). That is, when transmitting the Anchor_DPF_HO_Req to the target ASN-GW, the MS Info or the information of data path connected with MS can be transmitted together. At this time, the MS Info may include FA-CoA of the serving ASN-GW, and the information of data path connected with MS may include SF ID and Data Path ID.

[119] Also, the DPF 504 receives both the Anchor_DPF_HO_Rsp between the HA of the MS and the target ASN-GW, and the second SF Info. The DPF 504 transmits the Path_Modification_Req between the current BS (not shown) and the target ASN-GW including the second SF Info to the current BS.

[120] At this time, the Anchor_DPF_HO_Rsp is a response to the ASN-ASN handover request, and the second SF Info is data including the Data Path Info of the target ASN- GW.

[121] In this case, the gateway 502 supporting the handover between the ASNs functions as a proxy to transmit the second SF Info to the current BS. When the gateway 502 receives the Path_Modification_Rsp from the current BS, the gateway 502 transmits the Path_Modification_Ack to the current BS.

[122] When the gateway 502 supporting the handover between the ASNs performs the target ASN-GW function, the DPF 504 transmits the Anchor_DPF_Relocate_Req to the PMIP client 508. At this time, the PMIP client 508 may reside in the serving ASN- GW, the target ASN-GW, or the other ASN-GW. In response to the ASN-ASN handover request, the DPF 504 transmits the Anchor_DPF_HO_Rsp including the SF Info of the target ASN-GW to the serving ASN-GW.

[123] When the gateway 502 supporting the handover between the ASNs performs the target ASN-GW function, the FA 506 performs a procedure for registering a temporary address of the MS in the HA 510 of the MS in response to the ASN-ASN handover request. That is, the FA 506 transmits an RRQ to the HA 510 of the MS, and receives an RRP.

[124] The PMIP client 508 performs a FA relocation procedure of the MS in response to the ASN-ASN handover request. That is, on the ASN-ASN handover request, when the PMIP client 508 receives the Anchor_DPF_Relocate_Req including FAl-CoA and FA2-CoA, the PMIP client 508 checks whether or not the received FAl-CoA is identical to its own database information, generates the FA_Register_Req, and transmits the generated FA_Register_Req to the target ASN-GW. At this time, the FAl-CoA is a temporary address in the serving ASN-GW of the MS, and the FA2-CoA is a temporary address in the target ASN-GW.

[125] It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the inventions. Thus, it is intended that the present invention covers the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.

Claims

[1] A method for an ASN handover in a wireless access system, after a BS handover is completed between a previous BS and a current BS by a movement of an MS, comprising: establishing a first data path between the target ASN-GW and a home network if an ASN-ASN handover request message and first SF Info are transmitted to a target ASN-GW from a serving ASN-GW; transmitting a data path ID of the target ASN-GW to the serving ASN-GW; and establishing a second data path between the current BS and the target ASN-GW through the use of data path ID of the target ASN-GW.

[2] The method of claim 1, wherein the data path ID of the target ASN-GW, together with a second data path set-up request message generated by the serving ASN-

GW, is transmitted to the current BS through a proxy function of the serving

ASN-GW.

[3] The method of claim 1, wherein establishing the second data path comprises: receiving the second data path set-up request message including the data path ID of the target ASN-GW in the current BS from the serving ASN-GW; updating data path Info related with ASN-GW by using the data path ID of the target ASN-GW; and transmitting a second data path set-up completion message to the serving ASN-

GW.

[4] The method of claim 1, wherein the data path ID of the target ASN-GW is included in second SF Info generated by the target ASN-GW according to the

ASN-ASN handover request message.

[5] The method of claim 4, wherein the target ASN-GW uses downlink SF info of the first SF Info for downlink SF Info of the second data path, and wherein the current BS uses uplink SF Info of the second SF Info for uplink SF

Info of the second data path.

[6] The method of claim 4, wherein the second SF Info includes sub TLVs of SF ID,

Direction, and Data Path Info.

[7] The method of claim 1, further comprising generating a temporary tunnel between the serving ASN-GW and the target ASN-GW, wherein the temporary tunnel is maintained for a predetermined period, that is, until completing establishing the second data path after completing establishing the first data path.

[8] The method of claim 1, further comprising transmitting a data path set-up completion recognition message from the serving ASN-GW to the target ASN- GW, wherein the target ASN-GW repetitively transmits the first data path set-up completion message until receiving the data path set-up completion recognition message when it is not received in the target ASN-GW.

[9] The method of claim 1, wherein the serving ASN-GW and target ASN-GW include network entities serving as FAs, wherein the target ASN-GW, together with a PMIP client and an HA of the home network, performs a procedure for establishing the first data path.

[10] The method of claim 9, further comprising transmitting a message, which notifies that the procedure for establishing the first data path succeeds or fails, from the PMIP client to the target ASN-GW.

[11] The method of claim 1, wherein the serving ASN-GW and target ASN-GW include network entities serving as MAGs, wherein the target ASN-GW, together with a PMA and an LMA of the home network, performs a procedure for establishing the first data path.

[12] The method of claim 11, further comprising transmitting a message, which notifies that the procedure for establishing the first data path succeeds or fails, from the PMA to the target ASN-GW.

[13] The method of claim 1, wherein establishing the first data path comprises: transmitting a PBU message from the target ASN-GW to the home network; and responding to the PBU message received in the home network by a PBA message.

[14] A method for performing an ASN handover after a handover is completed between a previous BS and a current BS by a movement of an MS in a wireless access system, comprising: establishing a first data path between the target ASN-GW and a home network if an ASN-ASN handover request message is transmitted to a target ASN-GW from a serving ASN-GW; and establishing a second data path between the current BS and the target ASN-GW.

[15] The method of claim 14, wherein the ASN-ASN handover request message includes first SF Info of the serving ASN-GW, and downlink SF Info of the first SF Info is used for downlink SF Info of the second data path.

[16] The method of claim 15, further comprising generating second SF Info by the target ASN-GW in response to the ASN-ASN handover request message, wherein uplink SF Info of the second SF Info is used for uplink SF Info of the second data path.

[17] The method of claim 16, wherein the second SF Info is transmitted to the current

BS through a proxy function of the serving ASN-GW. [18] The method of claim 17, wherein establishing the second data path comprises: transmitting a second data path set-up request message including the second SF

Info from the serving ASN-GW to the current BS; updating data path Info related with ASN-GW in the current BS by using the uplink SF Info of the second SF Info; and transmitting a second data path set-up completion message to the serving ASN-

GW. [19] The method of claim 14, further comprising determining whether or not a data path set-up completion recognition message is received in the target ASN-GW from the serving ASN-GW, wherein the target ASN-GW repetitively transmits the first data path set-up completion message until receiving the data path set-up completion recognition message when it is not received in the target ASN-GW. [20] A method for supporting an ASN handover in a current BS after a handover is performed between a previous BS and the current BS by a movement of an MS in wireless communication system, comprising: receiving both a data path ID of the target ASN-GW and a second data path setup request message between the current BS and the target ASN-GW from the serving ASN-GW; establishing a second data path between the current BS and the target ASN-GW by using the data path ID of the target ASN-GW; and transmitting a second data path set-up completion message to the serving ASN-

GW. [21] The method of claim 20, wherein the data path ID of the target ASN-GW is included in second SF Info generated by the target ASN-GW. [22] The method of claim 21, wherein the current BS uses uplink SF Info of the second SF Info for uplink SF Info of the second data path. [23] The method of claim 20, further comprising receiving a second data path set-up completion acknowledgement message from the serving ASN-GW. [24] A method for performing a handover , in an ASN-GW including an FA function of the wireless access system, comprising: making an ASN-ASN handover request by the serving ASN-GW, the ASN-ASN handover request including MS Info and first SF Info connected with MS; transmitting a request for an MIP registration to an HA during a FA relocation procedure according to the ASN-ASN handover request; and receiving a response to the request for the MIP registration, and responding to the ASN-ASN handover request including second SF Info generated based on the first SF Info. [25] The method of claim 24, wherein the MS Info includes FA-CoA of the serving

ASN-GW. [26] The method of claim 24, wherein the first SF Info includes an SF ID and a data path ID connected with the MS. [27] A gateway for supporting a handover between ASNs after a handover is performed between a previous BS and a current BS by a movement of an MS, comprising: a DPF configured to receive first SF Info and a first ASN-ASN handover request message from a first ASN-GW, and to transmit a response message to the first

ASN-ASN handover request message and second SF Info generated by using the first SF Info to the first ASN-GW; and an FA configured to transmit a request for registering a temporary address of the

MS to a home network of the MS in response to the first ASN-ASN handover request message. [28] The gateway of claim 27, further comprising a PMIP client configured to perform an FA relocation procedure of the MS on the ASN-ASN handover. [29] The gateway of claim 27, wherein the DPF transmits second SF Info and a second ASN-ASN handover request message to a second ASN-GW; receives a response message to the second ASN-ASN handover request message and third

SF Info based on the second SF Info from the second ASN-GW; and transmits the third SF Info and a request message for establishing a data path between the second ASN-GW and the current BS to the current BS. [30] The gateway of claim 27, wherein the DPF uses downlink SF Info of the first SF

Info for downlink SF Info of the second SF Info, and uses its own data path ID for uplink SF Info of the second SF Info. [31] The gateway of claim 27, wherein the second SF Info includes sub-TLVs of SF

ID, Direction, and Data Path Info.