The present invention relates in general to telecommunication techniques. More particularly, the invention provides a method and system for foreign agent relocation. In a specific embodiment, the present invention provides a method and system for foreign agents in a network to receive location update signal from mobile stations and perform relocation. Merely by way of example, the invention is described as it applies to WiMAX wireless communication network, but it should be recognized that the invention has a broader range of applicability.
Techniques for wireless communications have progressed through the years. For example, satellite wireless communication networks have been developed where satellites are use to relay voice communication among wireless. There are other techniques as well. Over the recent years, the “cellular” wireless communication networks have become one of the most widely used technique for providing wireless communication.
A wireless network usually includes base stations and mobile stations. For example, a mobile station (MS) refers to a station that is to be used while in motion or during halts at unspecified geographic locations. As an example, the mobile station is a mobile communication device. In another example, the mobile station is a cellular phone. It is understood that the term mobile station is broad define, and may also includes wireless IP devices. A base station (BS) refers to a set of equipment that can provide connectivity, management, and control for one or more mobile stations. Typically, a BS functions as a paging agent (PA). For example, a paging agent refers to a functional entity that handles the interaction between PC and IEEE 802.16e specified Paging related functionality implemented in the Base Station.
As merely an example, a connective service network refers to a set of network functions that provide IP connectivity services to mobile stations. In an exemplary process flow, a MS obtains radio access from a BS. Through the BS, the MS obtains IP services.
In a telecommunication network, a mobile station is typically connected to a local network, which provides, among other things, radio connectivity. The local network also establishes a connection between the mobile station and a network where a variety of services (e.g., routing, Internet protocol routing, etc.) are provided. FIG. 1 is a simplified diagram illustrating a conventional telecommunication network. As an example, the conventional telecommunication network 100 as illustrated in FIG. 1 complies with WiMAX wireless (i.e., IEEE802.16d/e) networks.
In the, a mobile station 101, which is sometimes referred to as mobile subscriber station when the mobile station is subscribed to a specific network service provider, is connected to an access service network. For example, the mobile station 101 is connected to the access service network (ASN) 102. For example, the ASN 102 is configured to provide radio access to the mobile station 101.
In general, the ASNs that participate in HO process can be classified into four types:    a. Serving ASN that hosts Serving HO Function and serves the MS prior to HO.    b. Target ASN that hosts Target HO Function. There might be one or more Target ASNs. One of them is selected as the final HO Target and becomes Serving ASN after HO completion.    c. Anchor ASN that hosts the Anchor DP Function for the MS.    d. Authenticator ASN that hosts Authenticator/Key Distributor Function for the MS.
As an example, the ASN 102 includes a base station (BS) for providing radio access. For example, the BS refers to a generalized equipment set for providing connectivity, management, and control of mobile stations. In addition, the ASN 102 includes a gateway for interfacing with other networks. For example, the gateway allows the mobile station 101 to communicate with other ASNs (e.g., ASN 106). As another example, the gateway allows the mobile station 101 to connect to a connectivity service network (CSN) 104. As an example, the connectivity service network refers to a set of network functions that provide, among other things, IP connectivity service to mobile stations. Often, the CSNs also store policies associated with mobile stations.
Typically, a mobile station connects to a CSN that stores the network policies associated with the mobile station through an ASN. As an example, the CSN is often referred as network service provider from a management perspective. Similarly, the ASN is often referred to as network access provider from a management perspective.
In a Worldwide Interoperability for Microwave Access (WiMAX) network, a mobile station roams through different locations and obtains radio access from different ASNs. For example, a mobile station is initially connected to the WiMAX network through a home agent (HA). The HA typically stored identification and connectivity information for the mobile station. When mobile station moves to a different location, the mobile station obtains radio access from a new access network, which is typically referred as a foreign agent (FA), that is different from the home agent. As an example, a home agent refers to a router on a mobile station's home network, which tunnels datagrams for delivery to the mobile station when the mobile station is not connected to the home agent. In addition, a home station typically maintains current location information for the mobile station. Merely by way of an example, a foreign station refers to a router on a mobile station's visited network which provides routing services to the mobile stations when the mobile station is in the serving area of the visited network. Among other things, the foreign agent detunnels and delivers datagrams to the mobile stations that were tunneled by the mobile station's home agent. For datagrams sent from a mobile station, the foreign agent may also serve as a default router for registered mobile stations. For WiMAX wireless communication system, the FA can be a part of anchor data path function.
In a network, a data path (DP) function refers to a control function in the network which manages the data path setup and includes procedures for data packet transmission between two functional entities. An anchor data path function refers to the data path Function at an end of the data path, which anchors the data path is associated with the mobile station across handovers. For example, in WiMAX wireless communication system, the anchor DP function also includes the FA function.
For effective and reliable communication, mobile stations connect to different foreign agents based on the connectivity afforded by respective foreign agents. When a mobile stations moves from one location to another, the mobile station may switch to a different foreign agent even if the mobile station is in an idle mode. For example, the activities of mobile stations is administered by a paging controller. As an example, a paging controller (PC) refers to a functional entity that administers the activity of idle mode MS in the network. In certain networks, a PC is identified by the PC ID (e.g., 6 bytes) in IEEE 802.16e, which could map to the address of a functional entity. In various applications, the PC also includes location update information associated with mobile stations. For example, a PC performs paging updates, which is a procedure used by the network to seek an MS in idle mode in the coverage area of a predefined set of base station(s) identified by a Paging Group (as per IEEE 802.16e specification). In addition, Paging Update refers to procedures to obtain location update or network entry from an MS in idle mode. Paging procedures are implemented using Paging MAC message exchanges between MS and BS, under the control of a higher-layer paging management functions.
When a mobile station in a WiMAX system roam from one location to another, it sends location update message even if it is in the idle mode. In order for network (PC) to know the location of the MS which is in the idle mode, the MS needs to conduct periodically location update procedure to let anchor PC know which ASN currently the MS is roaming into. The following figure illustrates a procedure for location update.
FIG. 2 is a simplified diagram illustrating a conventional location update process. As shown, the process includes the following steps:                1. MS initiates Location Update (LU), or the Location Update is forced by network if the conditions described in IEEE 802.16e specification are met and as a result, the MS sends RNG_REQ. Ranging Purpose Indication is set as described in IEEE 802.16e specification indicating that the MS intends to update its location. PC ID (which points to PC acting as MS's Anchor PC) also need to be present.        2. PA sends LU Request to the Paging Relay (as shown in the FIG. 2). It contains: MS ID, PCID, BSID.        3. Paging Relay sends LU Request to Anchor PC. It contains: MSID, BSID and recommended paging parameters (PGID, Paging cycle, Paging Offset) etc.        4. If the LU-Request is accepted by Anchor PC and the Paging operation is still continuing, at this step .Paging_Annouce to ‘Stop Page’ may also be sent to the Paging groups defined for the MS. Anchor PC either accepts the recommended paging parameters or assigns new PGID and other paging parameters and sends LU Response message to Paging relay. LU Response includes: MSID, BSID, PGID and paging parameters, Anchor Authenticator ID, PCID, etc.        5. Paging Relay forwards LU Response to PA.        6. BS (where PA resides) determines whether it has a valid AK for the MSID from the indicated Anchor Authenticator. If it does not, the SBS sends AK Request (not shown in the diagram) to the Anchor Authenticator. AK Response (not shown) provides the AK sequence number, as well as the AK for the BS-MS secure association (as specified in 7.20.2 “AK Transfer Protocol”)        7. BS (where PA resides) uses AK to verify the integrity of the RNG-REQ received from MS. If the MS's RNG_REQ is successfully verified, the SBS responds to the MS with RNG_RSP with HMAC/CMAC. If the RNG-REQ could not be verified (such as when the Anchor Authenticator could not provide an AK), the BS begins the “Un-secure Location Update” sequence by initiating re-authentication;        8. In the case where RNG_REQ was verified, PA sends LU Confirm to Paging Relay (incl. MSID, BSID, success indication). It indicates location update from MS has been authenticated and the process is successfully completed.        9. Paging Relay forwards LU Confirm to Anchor PC.        
Anchor PC receives LU Confirm and finally updates MS location in the LR. In the event this location update was triggered by paging the MS, then the PC/LR initiates the cancel paging procedure (as described above). For example, it may send the Paging Announce message to stop the paging operation within the paging groups.
Over the past, various conventional WiMAX techniques relied on the PC to perform location update for mobile stations and foreign agents. Unfortunately, these conventional techniques are inadequate for various reasons.
Therefore, it is understood that an improved system and method for performing location update is desired.