WO2011075467A1

WO2011075467A1 - Method and system for macro base station to wfap handover

Info

Publication number: WO2011075467A1
Application number: PCT/US2010/060248
Authority: WO
Inventors: Jianquan Song; Tricci So; Wen Luo; Li Chu; Yangwei Tu
Original assignee: ZTE USA Inc
Current assignee: ZTE USA Inc
Priority date: 2009-12-14
Filing date: 2010-12-14
Publication date: 2011-06-23
Anticipated expiration: 2012-06-14

Abstract

In a WiMAX handover process, the serving macro base station becomes aware of a list of viable target WFAPs for the mobile station upon the entry of the mobile station into the serving base station. The serving base station uses this information to trigger base station initiated scanning and handover to the appropriate WFAP. Whenever the WFAP Mgmt System server is updated with the CSG Information for the given mobile station, the corresponding H-AAA server of the mobile station is also updated by the WFAP Mgmt System server with the latest CSG configuration information. The serving BS then receives the CSG white list during MS INE from MS-AAA server.

Description

SPECIFICATION

METHOD AND SYSTEM FOR MACRO BASE STATION TO WFAP HANDOVER

PRIORITY

[0001] Priority is claimed to U.S. Provisional Patent Application No. 61/286,249, filed December 14, 2009, the disclosure of which is incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

[0002] The field of the present invention is wireless communication, particularly to processes and systems for a macro base station to WiMAX Femto Access Point handover.

BACKGROUND

[0003] WiMAX (Worldwide Interoperability Microwave Access) is one of the wireless technologies targeting the fourth generation of wireless systems. The basic WiMAX network coverage is provided using an approach similar to other mobile wireless technologies (e.g., using high-power macro base stations).

[0004] Cellular communication systems are typically arranged so that a plurality of base stations are strategically positioned to provide wireless communication service over corresponding geographic areas. The area served by a base station is typically referred to as a cell. For various reasons, it is desirable for the base station to have information regarding nearby base stations, one of these reasons being for facilitating handoffs as mobile stations travel between cells. [0005] A WiMAX Femto Access Point (WFAP) is generally a low power WiMAX Base Station, operating in a licensed band and intended to: be end- user installed without service provider manual configuration (e.g., plug and play); provide service for a limited number of concurrent users over small areas such as the home, the small office, home office (SOHO), and the enterprise environments; use a shared broadband connection for backhaul that may be operated by a different Service Provider; and support limited user mobility (i.e., low speed, infrequent need for handover).

[0006] Generally, the WFAP is connected to a Femto Gateway server and other functional entities in a network through an IP Security tunnel provided by a Security Gateway server, which is responsible for authentication and supporting authorization of the WFAP. The Femto Gateway server generally controls WFAP(s) and performs transmission of user data packets to a Core Service Network. WFAP management includes configuration management which involves setting and changing attributes for proper network operations. A Closed Subscriber Group (CSG) is generally a set of users authorized by the FemtoCell subscriber and/or WFAP service provider to have reserved/privileged access to WiMAX services through a particular WFAP.

[0007] Generally, in cellular systems, system operators manually configure and manage neighbor lists based on the relative locations of base stations. This manual operation may be efficient for a network topology that hardly changes. However, in a femtocell network, WFAPs can be frequently installed or uninstalled by a user, and not just by a system operator, making it difficult for system operators to effectively manage neighbor lists. [0008] Unreliable or out-of-date neighbor information, for example, can create problems within the network. WFAP scanning may be limited to the WFAP's initialization. The WFAP may get neighbor base station information by scanning for nearby base stations or by obtaining a neighbor list from the system operator based on the WFAP's location. However, the constructed neighbor list based upon WFAP initialization may not be reliable for many reasons. For example, a neighbor base station may not have any business relationship with a WFAP's Network Service Provider (NSP) (note too that the NSP ID of a WFAP may not be the same as a neighbor base station); a neighbor base station may not be operational (e.g., powered off); or a neighbor base station may not be accessible by particular a mobile station.

SUMMARY OF THE INVENTION

[0009] The present invention is directed toward processes and systems associated with handover of a mobile station from a macro base station to WFAP base station. Upon attachment of the mobile station to the macro base station, whether by initial network entry or by handover, the macro base station requests and receives a list of viable target WFAPs for the mobile station. The macro base station uses this information to handover the mobile station to an appropriate WFAP.

[0010] In a first separate aspect of the present invention, a MS-AAA server includes closed subscriber group information for a mobile station as part of the mobile station context information. An anchor authenticator server transfers the closed subscriber group information to a serving base station, and during handover procedures, the serving base station transfers the closed subscriber group information to a target base station. [0011] In a second separate aspect of the present invention, a mobile station attaches to a serving base station, either by initial network entry or by hand over. The serving base station sends a closed subscriber group configuration information request to a WFAP management system server and receives the closed subscriber group configuration information from the WFAP management system server.

[0012] Any of the above aspects may be implemented alone or in combination.

[0013] Additional aspects and advantages of the improvements will appear from the drawings and the description of the preferred embodiment.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Embodiments of the present invention are illustrated by way of the accompanying drawings, in which:

[0015] Fig. 1 illustrates a process for the Serving BS receiving the MS White List during MS initial network entry (INE).

[0016] Fig. 2 illustrates a process for the control flow of the WFAP Mgmt System to maintain the CSG White List for an MS.

[0017] Fig. 3 illustrates a process for the Serving Base Station (SBS) obtaining the CSG white list after the MS accomplishes INE.

[0018] Fig. 4 illustrates a process for the MS-AAA updating the CSG Configuration Information to the SBS.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0019] A handover procedure for a mobile station may be intra-NAP (network access provider) or inter-NAP, depending on whether the WFAP and the overlay macro base station (BS) belong to the same NAP or not. The macro BS advertises the open WFAPs in its neighbor advertisement (NBR- ADV) broadcast. The macro BS does not advertise the closed subscriber group-closed (CSG-Closed) WFAPs in the NBR-ADV message due to the overhead that would be associated with such a broadcast. Hence, for triggering a handover to CSG-Closed WFAP, scanning may be used, and the scanning may be mobile station (MS) initiated or BS initiated.

[0020] The handover procedures may be the same as the baseline mobility scenario, with the following enhancement: the serving macro BS becomes aware of the list of viable target WFAPs for the MS upon the entry of the MS into the serving BS (taking into account CSG memberships of the MS). The serving BS uses this information to trigger BS-initiated scanning and handover to the appropriate WFAP.

[0021] The Serving BS may obtain the list of BS ID(s) for WFPAs of which the MS is the member of their CSGs via, for example, MS CSG Information Download during the MS Network Entry.

[0022] In the MS CSG Information Download during the MS Network Entry operating scenario, the MS-authentication, authorization, and accounting (AAA) server receives the CSG Information for the given MS from the WFAP Mgmt System server. Whenever the WFAP Mgmt System server is updated with the CSG Information for the given MS, the corresponding Home AAA (H-AAA) of the MS is likely to also be updated by the WFAP Mgmt System server with the latest CSG configuration information. The exact mechanism on how these two servers are synchronized on the CSG information configuration is outside the scope of this specification. The serving BS will then receive the CSG white list during MS initial network entry (INE) from MS-AAA.

[0023] The WFAP Mgmt System server may maintain the CSG White List for the given MS, and the BS may be pre-configured with the list of the WFAP Mgmt System servers. Whenever the MS is attached to the serving BS, for example, by INE or handover (HO), the serving BS may search for the corresponding WFAP Mgmt System server that may have the record of the given MS to be the member of its WFAP's CSG in order to derive the list of possible target WFAP BS ID(s) of which the MS is the member of their CSGs.

[0024] The WFAP Mgmt System server may maintain the CSG Information for the MS, and the BS may be pre-configured with the list of the WFAP Mgmt System server. The serving BS may then obtain the list of CSG Information from WFAP Mgmt System server after MS INE. The serving BS may append this information as one part of MS context.

[0010] Referring to Fig. 1 , steps 1-1 1 are well known to those of skill in the art as those steps associated with MS INE. In step 12, upon successful authentication, the MS-AAA server includes the MS's CSG information as one part of the MS context to be downloaded to the Anchor Authenticator server. In step 25, the Anchor Authenticator (AA) server transfers the MS CSG information as one part of the MS context to the Serving BS. In steps 26-28, the MS CSG information is transferred from the Serving BS to the Target BS during Handover procedures.

[0011] Referring to Fig. 2, after the MS is attached to the serving BS, for example, by INE or HO, the serving BS inquires about the CSG configuration information request from the WFAP Mgmt System(s) to obtain the list of target CSG WFAP BS ID(s) of which the MS may be the member of their CSGs. The WFAP Mgmt System server responds with the CSG configuration information response to the serving BS. This message may include the list of viable target CSG-Closed WFAP or nothing. This depends on whether CSG WFAP(s) exist which may be associated with both the MS and overlap with this Macro BS:

[0012] Referring to Fig. 3, after the MS completes INE, the serving BS sends the CSG configuration information request to the WFAP Mgmt System server to obtain the CSG information. The WFAP Mgmt System server sends the CSG configuration response to the serving BS. This message may include CSG Information for the given MS, if present. If there is CSG Information retrieved for the MS, such information may be one part of the MS context. As one part of the MS context, the CSG White List is transferred from the Serving BS to the Target BS during the handover procedures.

[0013] Referring to Fig. 4, the CSG Information may be modified after the serving BS obtains the CSG Information. Once the MS-AAA server receives the update of the CSG configuration for the given MS, it sends the updated CSG information to the AA server of the MS. Upon reception of the R3 message from MS-AAA server, the AA server relays the content of this message to the serving BS over R6 and possibly over R4. Then, the serving BS updates the CSG context information for the MS based on the information received from the AA server.

[0014] For the WFAP Mgmt System server, it may not trigger an update the CSG White List to the serving BS. [0015] While embodiments of this invention have been shown and described, it will be apparent to those skilled in the art that many more modifications are possible without departing from the inventive concepts herein. The invention, therefore, is not to be restricted except in the spirit of the following claims.

Claims

CLAIMS WHAT IS CLAIMED:

1. A method of handover in a WiMAX system comprising:

including, by a MS-AAA server, closed subscriber group information of a mobile station as part of mobile station context information;

transferring, by an anchor authenticator server, the closed subscriber group information of the mobile station to a serving base station; and

transferring, by the serving base station, the closed subscriber group information of the mobile station to a target base station during handover procedures.

2. The method of claim 1 , further comprising:

receiving, by the serving base station, of a list of target WiMAX Femto Access Points for the mobile station upon entry of the mobile station into the serving base station; and

using the list of target WiMAX Femto Access Points, by the serving base station, to trigger base station-initiated scanning and handover.

3. A method of control flow in a WiMAX system comprising:

attaching to a serving base station by a mobile station;

sending, by the serving base station, a closed subscriber group configuration information request to a WFAP Mgmt System server; and

receiving, by the serving base station, the closed subscriber group configuration information from the WFAP Mgmt System server.

4. The method of claim 3, wherein the mobile station attaches to the serving base station by handover.

5. The method of claim 3, wherein the mobile station attaches to the serving base station by initial network entry.

6. The method of claim 3, wherein the closed subscriber group configuration information includes a list of one or more target closed subscriber group WFAP base station identification.

7. The method of claim 3, wherein the closed subscriber group configuration information includes closed subscriber group information for the mobile station and is part of mobile station context information.

8. A method of modifying closed subscriber group information comprising: receiving an R3 message by an anchor authenticator, wherein the R3 message includes updated closed subscriber group information for a mobile station; and

relaying one of an R4 and R6 message, by the anchor authenticator to a serving base station, wherein the one of an R4 and R6 message includes updated closed subscriber group information.

9. The method of claim 8, wherein the serving base station updates closed subscriber group context information for the mobile station based on the updated closed subscriber group information.

10. A system of handover in a WiMAX system comprising:

means for including closed subscriber group information of a mobile station as part of mobile station context information;

means for transferring the closed subscriber group information of the mobile station to a serving base station; and means for transferring the closed subscriber group information of the mobile station to a target base station during handover procedures.

1 1. The system of claim 10, further comprising:

means for receiving a list of target WiMAX Femto Access Points for the mobile station upon entry of the mobile station into the serving base station; and

means for using the list of target WiMAX Femto Access Points to trigger base station-initiated scanning and handover.

12. A system of control flow in a WiMAX system comprising:

means for attaching a mobile station to a serving base station;

means for sending a closed subscriber group configuration information request to a WFAP Mgmt System server; and

means for receiving the closed subscriber group configuration information from the WFAP Mgmt System server.

13. The system of claim 12, wherein the means for attaching is configured for handover.

14. The system of claim 12, wherein the means for attaching is configured for initial network entry.

15. The system of claim 12, wherein the closed subscriber group configuration information includes a list of one or more target closed subscriber group WFAP base station identification.

16. The system of claim 14, wherein the closed subscriber group configuration information includes closed subscriber group information for the mobile station and is part of mobile station context information.

17. A system of modifying closed subscriber group information comprising: means for receiving an R3 message, wherein the R3 message includes updated closed subscriber group information for a mobile station; and

means for relaying one of an R4 and R6 message to a serving base station, wherein the one of an R4 and R6 message includes updated closed subscriber group information.

18. The system of claim 17, wherein a serving base station is configured to update closed subscriber group context information for the mobile station based on the updated closed subscriber group information.

19. A WiMAX handover network comprising:

an MS-AAA server configured to include closed subscriber group information of a mobile station as part of mobile station context information; an anchor authenticator server configured to transfer the closed subscriber group information of the mobile station to a serving base station; and

a serving base stations configured to transfer the closed subscriber group information of the mobile station to a target base station during handover procedures.

20. The network of claim 19, wherein the serving base station is further configured to (i) receive a list of target WiMAX Femto Access Points for the mobile station upon entry of the mobile station into the serving base station; and (ii) use the list of target WiMAX Femto Access Points to trigger base station-initiated scanning and handover.

21. A WiMAX control flow network comprising a mobile station configured to attach to a serving base station, wherein the serving base station is configured to (i) send a closed subscriber group configuration information request to a WFAP Mgmt System server; and (ii) receive the closed subscriber group configuration information from the WFAP Mgmt System server.

22. The network of claim 21 , wherein the mobile station is further configured to attach to the serving base station by handover.

23. The network of claim 21 , wherein the mobile station is further configured to attach to the serving base station by initial network entry.

24. The network of claim 21 , wherein the closed subscriber group configuration information includes a list of one or more target closed subscriber group WFAP base station identification.

25. The network of claim 23, wherein the closed subscriber group configuration information includes closed subscriber group information for the mobile station and is part of mobile station context information.

26. A network for modifying closed subscriber group information comprising an anchor authenticator server configured to (i) receive an R3 message, wherein the R3 message includes updated closed subscriber group information for a mobile station; and (ii) relay one of an R4 and R6 message to a serving base station, wherein the one of an R4 and R6 message includes updated closed subscriber group information.

27. The network of claim 26, wherein the serving base station is configured to update closed subscriber group context information for the mobile station based on the updated closed subscriber group information.