System and method for handoff processing

• US 7,272,123 B2
• Filed: 09/13/2005
• Issued: 09/18/2007
• Est. Priority Date: 09/13/2004
• Status: Active Grant

• Current Assignee: Nextel Communications (Deutsche Telekom AG)
• Original Assignee: Nextel Communications (Deutsche Telekom AG)
• Inventors: Wall, Stephen B.
• Primary Examiner(s): Pham; Chi
• Assistant Examiner(s): HOM, SHICK C
• Application Number:
  US11/226,126
• Publication Number:
  US 20060056351A1
• Time in Patent Office: 735 Days
• Field of Search: 370/310, 370/331, 370/332, 370/346, 370/352, 370/395.52, 455/436, 455/437, 455/438, 455/439, 455/440, 455/442, 455/443
• US Class Current: 370/331
• CPC Class Codes: H04W 36/0016 Hand-off preparation specially adapted for end-to-end data sessions
• CPC Class Codes: H04W 36/0033 with transfer of context information
• CPC Class Codes: H04W 36/08 Reselecting an access point
• CPC Class Codes: H04W 8/26 Network addressing or numbering for mobility support
• CPC Class Codes: H04W 80/04 Network layer protocols, e.g. mobile IP [Internet Protocol]
• CPC Class Codes: H04W 88/08 Access point devices

Abstract

A system and method for optimizing handoff processing in networks with fully collapsed base station routers is disclosed. In accordance with exemplary embodiments of the present invention, handoff processing is optimized by allowing base station routers to automatically discover, and maintain lists of, their neighbor base station routers. Using the list of discovered neighbor base station routers, a base station router polls its neighbors for a list of all active users. The base station router then polls the Context Transfer Server (CTS) database for these users'"'"' contexts. Accordingly, instead of polling the CTS database during handoff, the present invention allows a base station router to activate the context from local memory.

Claims

1. In a wireless communications network having a plurality of base stations and a context transfer server, a method for processing handoff requests between a source base station and a destination base station, comprising the steps, performed by the destination base station, of:

requesting, from the source base station, an identifier associated with each of a plurality of active mobile nodes registered on the source base station;

retrieving, from the context transfer server, a context associated with each identified mobile node;

storing the retrieved contexts in a local cache;

receiving a handoff request from a first mobile node, the first mobile node having an associated context stored in the local cache; and

applying the stored context to the first mobile node,

wherein the destination base station discovers an Internet Protocol (IP) address of the source base station by performing a handoff process with the source base station, the handoff process including the IP address of the source base station, and storing the IP address of the source base station in the local cache.

2. In a wireless communications network having a plurality of base stations and a context transfer server, a method for processing handoff requests between a source base station and a destination base station, comprising the steps, performed by the destination base station, of:

requesting, from the source base station, an identifier associated with each of a plurality of active mobile nodes registered on the source base station;

retrieving, from the context transfer server, a context associated with each identified mobile node;

storing the retrieved contexts in a local cache;

receiving a handoff request from a first mobile node, the first mobile node having an associated context stored in the local cache; and

applying the stored context to the first mobile node,

wherein the step of storing the retrieved contexts comprises storing a local IP address and a home IP address for each identified mobile node.

3. In a wireless communications network having a plurality of base stations and a context transfer server, a method for processing handoff requests between a source base station and a destination base station, comprising the steps, performed by the destination base station, of:

requesting, from the source base station, an identifier associated with each of a plurality of active mobile nodes registered on the source base station;

retrieving, from the context transfer server, a context associated with each identified mobile node;

storing the retrieved contexts in a local cache;

receiving a handoff request from a first mobile node, the first mobile node having an associated context stored in the local cache;

applying the stored context to the first mobile node; and

for each identified mobile node, setting a timer after an associated context is received and subsequently deleting the stored context for the mobile node after the timer expires.

4. In a wireless communications network having a plurality of base stations and a context transfer server, a method for processing handoff requests between a source base station and a destination base station, comprising the steps, performed by the destination base station, of:

requesting, from the source base station, an identifier associated with each of a plurality of active mobile nodes registered on the source base station;

retrieving, from the context transfer server, a context associated with each identified mobile node;

storing the retrieved contexts in a local cache;

receiving a handoff request from a first mobile node, the first mobile node having an associated context stored in the local cache; and

applying the stored context to the first mobile node, including the steps of;

establishing a temporary communications tunnel with the source base station;

receiving, at the destination base station through the temporary communications tunnel, IP packets directed to a first local IP address of the first mobile node;

instructing a home agent to direct IP communications addressed to the first local IP address to the destination base station; and

removing the temporary communications tunnel.

5. In a wireless communications network having a plurality of base stations and a context transfer server, a method for processing handoff requests between a source base station and a destination base station, comprising the steps, performed by the destination base station, of:

requesting, from the source base station, an identifier associated with each of a plurality of active mobile nodes registered on the source base station;

retrieving, from the context transfer server, a context associated with each identified mobile node;

storing the retrieved contexts in a local cache;

receiving a handoff request from a first mobile node, the first mobile node having an associated context stored in the local cache; and

applying the stored context to the first mobile node, including the steps of;

designating a second local IP address for the first mobile node, the second local IP address providing a care of address on the destination base station; and

instructing the home agent to direct IP communications to the second local IP address on the destination base station.

6. In a communications network facilitating wireless Internet Protocol (IP) communications, a base station router having a fully collapsed architecture comprising:

a base transceiver system for facilitating wireless communications with a plurality of mobile nodes;

a packet data serving node facilitating communications with an external packet data network, the packet data serving node including a foreign agent function for assigning local IF addresses to roaming mobile nodes;

a storage means for storing contexts of mobile nodes active on identified neighboring base stations;

a program memory including program logic for instructing a processor to poll neighboring base stations for identifiers associated with the active mobile nodes, request from the context transfer server the contexts of the identified active mobile nodes, and store contexts received from the context transfer server in the storage means;

a base station controller for processing a handoff request from a first mobile node, including registering the first mobile node for communication with the base station router and applying a corresponding stored context to the first mobile node; and

an interface facilitating data communication with a home agent.

7. The base station of claim 6 wherein the program memory further comprises a neighbor discovery function for retrieving a neighbor base station IP address from a handoff process and storing the retrieved neighbor base station IP address in the storage means.

8. The base station of claim 6 wherein the program memory further comprises a neighbor discovery function for retrieving a neighbor base station IP address from a domain host control protocol (DHCP) service discovery.

9. The base station of claim 6 wherein the mobile node identifiers include IP addresses associated with the active mobile nodes.

10. The base station of claim 9 wherein the foreign agent function is further adapted to receive, from a home network, data communications directed to an IP address of the first mobile node.

11. The base station of claim 6 wherein the storage means is adapted to store a local IP address and a home IP address for each identified mobile node.

12. The base station of claim 6 wherein the program memory further comprises a timer function including setting a timer for each identifier mobile node when associated context information is received and deleting the mobile node identifier and associated context from the cache when the timer expires.

13. The base station of claim 6 wherein the base station controller is further adapted to establish a temporary communications tunnel with the source base station, receive, at the destination base station through the temporary communications tunnel, IP packets directed to the first mobile node, instruct the home agent to direct IP communications directed to the first local IP address to the destination base station, and remove the temporary communications tunnel.