Methods and apparatus for supporting micro-mobility within a radio access network

• US 7,158,497 B2
• Filed: 05/17/2001
• Issued: 01/02/2007
• Est. Priority Date: 08/31/2000
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Nortel Networks Limited (Nortel Networks Corporation)
• Inventors: Xu, Donna D., Janevski, Goran G., Reza, Ahmed Areef, Li, Hongyi, Pieris, Gerard R.
• Primary Examiner(s): To, Doris H.
• Assistant Examiner(s): Elallam, Ahmed
• Application Number:
  US09/858,475
• Publication Number:
  US 20020031107A1
• Time in Patent Office: 2,056 Days
• Field of Search: 370328-350, 455/436
• US Class Current: 370/331
• CPC Class Codes: H04L 12/18 for broadcast or conference , e.g. multicast
• CPC Class Codes: H04L 61/5014 using dynamic host configuration protocol [DHCP] or bootstrap protocol [BOOTP]
• CPC Class Codes: H04W 36/0011 for data sessions of end-to-end connection
• CPC Class Codes: H04W 36/0019 adapted for mobile IP [MIP]
• CPC Class Codes: H04W 40/02 Communication route or path selection, e.g. power-based or shortest path routing
• CPC Class Codes: H04W 40/248 Connectivity information update
• CPC Class Codes: H04W 40/36 due to handover
• CPC Class Codes: H04W 74/00 Wireless channel access
• CPC Class Codes: H04W 8/02 Processing of mobility data, e.g. registration information at HLR [Home Location Register] or VLR [Visitor Location Register]; Transfer of mobility data, e.g. between HLR, VLR or external networks
• CPC Class Codes: H04W 8/087 for preserving data network PoA address despite hand-offs

Abstract

The invention provides a novel protocol suite for supporting micro-mobility within a radio access network (RAN). The protocol suite and comprises three separate protocols, namely a Mobile Registration Protocol, a Handoff Affected Router Discovery Protocol (HARDP) and a Mobile Location Update Protocol. The Mobile Registration Protocol is used to register mobile terminals within a RAN while the Mobile Location Update Protocol is used to update mobile terminal reachability during a handoff. The HARDP protocol is used at network boot-up time to identify a subset of routers that needs to be updated when a mobile terminal handoff occurs between two neighboring radio access nodes.

Claims

1. A system for forwarding data packets to a mobile terminal comprising:

a radio access network comprising at least one externally connected gateway node, a plurality of packet routers, and a plurality of radio access nodes each having a respective coverage area and each for establishing a wireless communications link with mobile terminals within the respective coverage area, each packet router and each radio access node having a respective network address, each packet router associating a next-hop forwarding entry with each of the radio access nodes;

a first protocol to provide an assigned network address to a mobile terminal for a communications session initially through a particular radio access node within whose coverage area the mobile terminal is located and to broadcast the assigned network address and the network address of the particular radio access node to the plurality of packet routers so as to cause each packet router to create a new next-hop forwarding entry for the mobile terminal, the new next-hop forwarding entry for the mobile terminal corresponding with the next-hop forwarding entry for the particular radio access node;

a second protocol to update the next-hop forwarding entries for the mobile terminal for a subset of the packet routers when the mobile terminal moves from the coverage area of the particular radio access node to the coverage area of a subsequent radio access node by causing each packet router in the subset of packet routers to change the next-hop forwarding entry for the mobile terminal to correspond with the next-hop forwarding entry for the subsequent radio access node;

a third protocol to define said subset of the packet routers for each {particular radio access node, subsequent radio access node} pair such that only the subset of packet routers are required to update their next-hop forwarding entries for a mobile terminal handoff from the particular radio access node to the subsequent radio access node.

2. A system according to claim 1 further comprising an address server located within the radio access network;

wherein the first protocol is adapted to obtain the assigned network address for the mobile terminal from the address server.

3. A system according to claim 2 wherein the address server is an extended dynamic host configuration protocol (DHCP) server.

4. A system according to claim 2 wherein the first protocol comprises:

the mobile terminal establishing a wireless communications link with the particular radio access node within whose coverage area the mobile terminal is located;

the mobile terminal sending a first message to the particular radio access node within whose coverage area the mobile terminal is located, the first message requesting said assigned network address;

the particular radio access node receiving the first message and sending a second message to the address server requesting said assigned network address;

the address server responding to the particular radio access node with a third message comprising said assigned network address for the mobile terminal;

the particular radio access node forwarding the third message to the mobile terminal and then broadcasting a fourth message to the plurality of packet routers in the radio access network, the fourth message comprising the network address for the particular radio access node and the assigned network address for the mobile terminal;

each of the plurality of packet routers adding a new next-hop forwarding entry for the mobile terminal corresponding to the next-hop forwarding entry for the particular radio access node within whose coverage area the mobile terminal is located.

5. A system according to claim 1 wherein the third protocol is adapted to include in the subset only those packet routers having different next-hop forwarding entries for the particular and subsequent radio access nodes.

6. A system according to claim 5 further comprising an address server located within the radio access network;

wherein the third protocol adapted to define said subset of the packet routers for each {particular radio access node, subsequent radio access node} pair comprises;

the particular radio access node broadcasting a first message to the subsequent radio access node;

the subsequent radio access node in response to the first message sending a second message to the address server identifying the particular radio access node and the subsequent radio access node;

the address server assigning a single multicast address to represent said subset of packet routers and sending the multicast address in a third message to the subsequent radio access node;

the subsequent radio access node sending a fourth message to the particular radio access node containing the multicast address assigned to said subset of packet routers;

the particular radio access node broadcasting a fifth message to each of said plurality of packet routers, the fifth message comprising the network address of the particular radio access node, the network address of the subsequent radio access node and the multicast address assigned to said subset of packet routers;

each of said plurality of packet routers comparing the next-hop forwarding entry for the particular radio access node to the next-hop forwarding entry for the subsequent radio access node and in the event that the next-hop forwarding entries are different, issuing a request message to join the subset of packet routers to which the multicast address is assigned.

7. A system according to claim 5 further comprising an address server located within the radio access network;

wherein the third protocol adapted to define said subset of the packet routers for each particular radio access node, subsequent radio access node pair comprises;

the particular radio access node sending a first message to the subsequent radio access node;

the subsequent radio access node in response to the first message sending a second message to the address server identifying the particular radio access node and the subsequent radio access node;

the address server assigning a single multicast address to represent said subset of packet routers and sending the multicast address in a third message to the subsequent radio access node;

the subsequent radio access node sending a fourth message to the particular radio access node, the fourth message comprising the multicast address assigned to said subset of packet routers and a virtual handoff mobile address;

the particular radio access node broadcasting a fifth message to each of said plurality of packet routers, the fifth message comprising the network address of the particular radio access node and the virtual handoff mobile address;

each of said plurality of packet routers receiving the fifth message and adding a first next-hop forwarding entry for the virtual handoff mobile address, the first next-hop forwarding entry for the virtual handoff mobile address corresponding to the next-hop forwarding entry for the particular radio access node;

the particular radio access node sending a sixth message to the subsequent radio access node, the sixth message triggering the subsequent radio access node to broadcast a seventh message to each of said plurality of packet routers, the seventh message comprising the virtual handoff mobile address, the network address of the subsequent radio access node and the multicast address assigned to said subset of packet routers;

each of said plurality of packet routers computing a second next-hop forwarding entry for the virtual handoff mobile address;

each of said plurality of packet routers comparing the second next-hop forwarding entry for the virtual handoff mobile address to the first next-hop forwarding entry for the virtual handoff mobile address and in the event that the next-hop forwarding entries are different, issuing a request message to join the subset of packet routers to which the multicast address is assigned;

the particular radio access node broadcasting an eighth message the said plurality of packet routers so as to cause each packet router to remove the next-hop forwarding entry for the virtual handoff mobile address.

8. A system according to claim 1 wherein the first protocol pre-allocates a set of addresses to each radio access node and sets up routes for these addresses in the routers before the addresses are actually assigned to mobile terminals.

9. A system according to claim 1 wherein the second protocol comprises:

the particular radio access node sending a first message to the mobile terminal indicating that a wireless communications link to the subsequent radio access node should be established;

the mobile terminal receiving the first message and sending a second message to the subsequent radio access node in order to establish a wireless communications link to the subsequent radio access node, the second message identifying the mobile terminal and the particular radio access node whose coverage area the mobile terminal is leaving;

the subsequent radio access node receiving the second message and sending a third message to said subset of packet routers, the third message comprising the network address of the subsequent radio access node and the network address of the mobile terminal;

each packet router in said subset of packet routers receiving the third message and changing the next-hop forwarding entry for the mobile terminal to correspond to the next-hop forwarding entry for the subsequent radio access node.

10. A system according to claim 1 wherein the network addresses are Internet Protocol (IP) addresses.

11. A system according to claim 1 wherein the data packets are Internet Protocol (IP) packets.

12. A system according to claim 11 adapted for use with IP version 4 or IP version 6.

13. A system according to claim 1 wherein the first, second and third protocols together provide a protocol suite adapted to function as a mobile routing protocol for updating a mobile terminal'"'"'s reachability in an overlay network that comprises mobility agents connected by IP tunnels over network routers.

14. A system according to claim 13 wherein the protocol suite runs in the mobility agents.

15. A method for forwarding data packets to a mobile terminal within a radio access network comprising a plurality of packet routers and a plurality of radio access nodes each having a respective network address, the method comprising:

providing each packet router with a respective next-hop forwarding table populated with next-hop forwarding entries for each of the plurality of radio access nodes;

providing an assigned network address to a mobile terminal for a communications session initially through a particular radio access node within whose coverage area the mobile terminal is located;

broadcasting the assigned network address and the network address of the particular radio access node to the plurality of packet routers so as to cause each packet router to create a new next-hop forwarding entry for the mobile terminal, the new next-hop forwarding entry for the mobile terminal corresponding with the next-hop forwarding entry for the particular radio access node;

updating the next-hop forwarding tables of a subset of the plurality of packet routers when the mobile terminal moves from the coverage area of the particular radio access node to the coverage area of a subsequent radio access node by causing each packet router in the subset of packet routers to change the next-hop forwarding entry for the mobile terminal to correspond to the next-hop forwarding entry for the subsequent radio access node.

16. A method according to claim 15 further comprising for each {particular radio access node, subsequent radio access node} pair, defining the subset of packet routers whose next-hop forwarding tables need to be updated when the mobile terminal moves from the coverage area of the particular radio access node to the coverage area of the subsequent radio access node such that only the subset of packet routers are required to update their next-hop forwarding tables.

17. A method according to claim 16 further comprising each router updating its membership in the subset for a {particular radio access node, subsequent radio access node} pair when the next-hop forwarding entry for either or both of the particular radio access node and the subsequent radio access node changes.

18. A method according to claim 15 further comprising radio access nodes learning a neighboring relationship with other radio access nodes in terms of common coverage areas.

19. A method according to claim 15 wherein the data packets are Internet Protocol (IP) packets.

20. A method according to claim 15 wherein the network addresses are Internet Protocol (IP) addresses.

21. A packet router comprising:

a next-hop forwarding table populated with a next-hop forwarding entry for each of a plurality of mobile terminals and a plurality of radio access nodes;

an input to receive a message identifying a network address for a mobile terminal and a network address for a particular one of said plurality of radio access nodes within whose coverage area the mobile terminal is located;

a message processor to process said message by;

in the event no next-hop forwarding entry exists for the mobile terminal, adding a new next-hop forwarding entry to the next-hop forwarding table for the mobile terminal, the new next-hop forwarding entry corresponding to the next-hop forwarding entry already in the table for the particular radio access node;

and in the event a next-hop forwarding entry exists for the mobile terminal, changing the next-hop forwarding entry for the mobile terminal to correspond to the next-hop forwarding entry already in the table for the particular radio access node;

wherein a data packet to be routed contains a destination network address of a mobile terminal to which the packet is to be routed, and the packet router forwards the packet according to the next-hop forwarding entry for the destination network address contained in the packet.

22. A packet router according to claim 21 wherein the next-hop forwarding table is organized as an array indexed with network addresses for each of the plurality of mobile terminals and radio access nodes.

23. A packet router according to claim 21 wherein the next-hop forwarding table is organized as an array and associates a network address for each of the plurality of mobile terminals and radio access nodes with a network address for a next-hop forwarding device.

24. A packet router according to claim 21 further comprising host route summarization and de-summarization algorithms adapted to compress the routing table.

25. A packet router according to claim 24 wherein host route summarization algorithm summarizes common forwarding paths into a single path identified by a common address prefix of destination network addresses.

26. A packet router according to claim 24 wherein the de-summarization algorithm de-summarizes a common forwarding path identified by a common address prefix into separate paths due to a mobile terminals forwarding path departing from the common path.

27. A packet router according to claim 21 adapted to route Internet Protocol (IP) packets.

28. A packet router according to claim 27 wherein the network addresses are Internet Protocol (IP) addresses.

29. A mobility agent connected with other mobility agents using IP tunnels, the mobility agent to provide a protocol suite comprising:

a first protocol to provide an assigned network address to a mobile terminal for a communications session initially through a particular radio access node within whose coverage area the mobile terminal is located and to broadcast the assigned network address and the network address of the particular radio access node to a plurality of packet routers so as to cause each packet router to create a new next-hop forwarding entry for the mobile terminal, the new next-hop forwarding entry for the mobile terminal corresponding with the next-hop forwarding entry for the particular radio access node;

a second protocol to update the next-hop forwarding entries for the mobile terminal for a subset of the packet routers when the mobile terminal moves from the coverage area of the particular radio access node to the coverage area of a subsequent radio access node by causing each packet router in the subset of packet routers to change the next-hop forwarding entry for the mobile terminal to correspond with the next-hop forwarding entry for the subsequent radio access node;

a third protocol to define said subset of the packet routers for each {particular radio access node, subsequent radio access node} pair such that only the subset of packet routers are required to update their next-hop forwarding entries for a mobile terminal handoff from the particular radio access node to the subsequent radio access node.