Method for rerouting and route optimization for handoff management in a communications network

• US 6,654,361 B1
• Filed: 09/22/1998
• Issued: 11/25/2003
• Est. Priority Date: 09/22/1997
• Status: Expired due to Fees

• Current Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Original Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Inventors: Dommety, Gopal K., Veeraraghavan, Malathi
• Primary Examiner(s): Yao, Kwang Bin
• Assistant Examiner(s): NGUYEN, HANH N
• Application Number:
  US09/158,402
• Time in Patent Office: 1,890 Days
• Field of Search: 370/338, 370/384, 370/328, 370/408, 370/396, 370/331-336, 370/238.1, 370/341, 370/351, 370/360, 370/310, 370/400, 370/238, 370/352, 370/395.52, 370/397, 370/395.64, 370/395.65, 370/395.5, 455/433-439, 455/400, 455/445
• US Class Current: 370/331
• CPC Class Codes: H04L 45/04 Interdomain routing, e.g. hierarchical routing
• CPC Class Codes: H04W 36/12 Reselecting a serving backbone network switching or routing node
• CPC Class Codes: H04W 40/00 Communication routing or communication path finding
• CPC Class Codes: H04W 40/36 due to handover

Abstract

A handoff scheme for a communications network is disclosed. In a first embodiment a procedure for finding an optimal path between an originating network node and a destination network node is integrated in the handoff procedure. An optimally routed connection is obtained by first determining an optimal “crossover node” along the existing path and then the handoff is effected by altering the existing connection route so that it travels along the existing path until it reaches the crossover node, where the path then varies from the original route, and a new segment between the crossover node and the new location is established. Then the call is switched to the new segment and the corresponding old segment on the old connection is released. In an alternative embodiment, the handoff procedure is performed first by completing a fast reroute connection using a prior art path extension method. This results in a quick, but sub-optimal handoff connection. Once the handoff is completed, the route is optimized by selecting a segment on the sub-optimal connection for rerouting and then utilizing the method of the first embodiment to establish an optimally routed connection.

Claims

1. A method for managing the handoff of a call on a hierarchical connection-oriented mobile network, said connection-oriented mobile network comprising a plurality of interconnectable access points and network switches, wherein a connection exists between a first access point and a second access point, and a new connection is desired between said first access point and a third access point, said method comprising:

determining a crossover node, said crossover node being a network switch located along the path of said existing connection, said step of determining the crossover node including selecting a level in said hierarchical connection-oriented mobile network at which ancestors of said second access point and third access points are siblings;

setting up a new connection path between said crossover node and said third access point; and

connecting the call between said first access point and said third access point by switching the call along said new connection path.

2. The method as set forth in claim 1, further comprising the steps of:

determining an old segment path between said crossover node and said second access point; and

releasing said old segment path back.

3. The method of claim 1, and wherein said step of determining a crossover node further comprises the steps of:

determining a shortest path between said first access point and said third access point along said plurality of interconnectable access points;

determining a portion of said shortest path and said existing connection that coincide; and

determining a network switch on said coinciding portion of said shortest path and said existing connection that is farthest from said first access point, said network switch being said crossover node.

4. The method of claim 1, wherein said crossover node is said first access point.

5. The method of claim 1, wherein said step of determining said crossover node comprises the step of selecting said third access point or said second access point for initiation of said crossover node determination.

6. The method of claim 1, wherein said step of determining said crossover node is initiated at said second access point.

7. The method of claim 6, wherein said step of determining said crossover node further comprises the step of tracing back the path of said existing connection from said second access point to said crossover node.

8. The method of claim 1, wherein said step of determining said crossover node is initiated at said third access point.

9. The method of claim 1, wherein said of determining a crossover node further comprises the steps of:

determining a provisional crossover node;

determining whether a hierarchical path is available in said hierarchical network;

determining whether another network switch can further modify the existing path; and

determining an optimal crossover node.

10. The method of claim 9, wherein said provisional crossover node is an ingress border of a peer group in which ancestors of said second access point and said third access point are siblings, and said provisional crossover node is said crossover node.

11. The method of claim 9, said provisional crossover node is the first access point.

12. The method of claim 9, said provisional crossover node is said crossover node.

13. The method of claim 9, said optimal crossover node is said crossover node.

14. The method of claim 9, wherein said step of determining optimal crossover node further comprises the steps of:

(ii) determining a shortest path between said first access point and said third access point along said plurality of interconnectable access points and network nodes;

(iii) determining a portion of said shortest path and said existing connection that coincide;

(iv) determining a network switch on said coinciding portion of said shortest path and said existing connection that is farthest from said first access point, said network switch being said crossover node;

(v) selecting the next lower level in said hierarchical network and apply the iteration of step (ii), (iii), (iv); and

(vi) iteratively repeating steps (ii)-(v) until the lowest physical level in the hierarchical network has been reached.

15. The method of claim 14, wherein said crossover determination is initiated from said second access point.

16. The method of claim 15, wherein said crossover determination is initiated from said third access point.

17. The method of claim 1, wherein said hierarchical connection-oriented mobile network is a PNNI hierarchical network and said step of determining a crossover node comprises the steps of:

determining whether said second access point is closer to said first access point or to said third access point; and

determining a crossover node under PNNI constraints.

18. The method of claim 17, wherein said first access point is said crossover node.

19. The method of claim 18, wherein said second access point is closer to said third access point than to said first access point, and said crossover node is an ingress border of a peer group in which ancestors of said second access point and said third access point are siblings.

20. A method for rerouting an existing connection in a hierarchical connection-oriented communications network to a new desired connection, wherein said existing connection is between a first network switch and a second network switch, and said new connection is desired between said first network switch and a third network switch, said connection-oriented communications network comprising a plurality of interconnectable network switches, said method comprising the steps of:

determining a crossover node, said crossover node being a network switch located along the path of said existing connection, said step of determining the crossover node including selecting a level in said hierarchical connection-oriented mobile network at which ancestors of said second access point and third access points are siblings; and

setting up a new connection path between said crossover node and said third network switch.

21. The method as set forth in claim 20, further comprising the step of determining an old segment path between said crossover node and said second network switch.

22. The method of claim 20, and wherein said step of determining a crossover node further comprises the steps of:

determining a shortest path between said first network switch and said third network switch along said plurality of interconnectable network switches;

determining a portion of said shortest path and said existing connection that coincide; and

determining a fourth network switch on said coinciding portion of said shortest path and said existing connection that is farthest from said first network switch, said fourth network switch being said crossover node.

23. The method of claim 20, said crossover node is said first network switch.

24. The method of claim 20, wherein said step of determining said crossover node comprises the step of selecting whether to use said third network switch or said second network switch for initiation of said crossover node determination.

25. The method of claim 20, wherein said step of determining said crossover node is initiated at said second network switch.

26. The method of claim 25, wherein said step of determining said crossover node further comprises the step of tracing back the path of said existing connection from said second network switch to said crossover node.

27. The method of claim 20, wherein said step of determining said crossover node is initiated at said third network switch.

28. The method of claim 20, wherein said hierarchical connection-oriented communications network is a hierarchical network, and said step of determining a crossover node further comprises the steps of:

determining a provisional crossover node;

determining whether a hierarchical path is available in said hierarchical network;

determining whether another network switch can further modify the existing path; and

determining an optimal crossover node.

29. The method of claim 28, wherein said provisional crossover node is an ingress border of a peer group in which ancestors of said second network switch and said third network switch are siblings.

30. The method of claim 28, said provisional crossover node is said first network switch.

31. The method of claim 28, said provisional crossover node is said crossover node.

32. The method of claim 28, said optimal crossover node is said crossover node.

33. The method of claim 28, wherein step of determining optimal crossover node further comprises the steps of:

(ii) determining a shortest path between said first network switch and said third network switch along said plurality of interconnectable network switch;

(iii) determining a portion of said shortest path and said existing connection that coincide;

(iv) determining a fourth network switch on said coinciding portion of said shortest path and said existing connection that is farthest from said first network switch, said fourth network switch being said crossover node;

(v) selecting the next lower level in said hierarchical network and apply the iteration of step (ii), (iii), (iv); and

(vi) iteratively repeating steps (ii)-(v) until the lowest physical level in the hierarchical network has been reached.

34. The method of claim 33, wherein said crossover determination is initiated from said second network switch.

35. The method of claim 33, wherein said crossover determination is initiated from said third network switch.

36. The method of claim 20, wherein said hierarchical connection-oriented communications network is a PNNI hierarchical network and said step of determining a crossover node comprises the steps of:

determining whether said second network switch is closer to said first network switch or to said third network switch; and

determining a crossover node under PNNI constraints.

37. The method of claim 36, wherein said first network switch is the crossover node.

38. The method of claim 36, wherein said second network switch is closer to said third network switch than to said first network switch, and said crossover node is an ingress border of a peer group in which ancestors of said second network switch and said third network switch are siblings.

39. The method of claim 20, wherein said hierarchical connection-oriented communications network is a mobile network and said network switches are access points in said mobile network.

40. The method of claim 20, wherein said hierarchical connection-oriented communications network is a mobile network and said network switches are base stations in said mobile network.

41. The method of claim 20, wherein said hierarchical connection-oriented communications network is a mobile ATM network.

42. The method of claim 20, wherein said hierarchical connection-oriented communication network is a mobile IP network.