Apparatus and method for improved handover in mesh networks

• US 20070019598A1
• Filed: 06/22/2006
• Published: 01/25/2007
• Est. Priority Date: 06/30/2005
• Status: Active Grant

• Current Assignee: NTT Docomo Incorporated (Nippon Telegraph and Telephone Corporation)
• Original Assignee: NTT Docomo Incorporated (Nippon Telegraph and Telephone Corporation)
• Inventors: Prehofer, Christian
• Granted Patent: US 8,023,465 B2
• Time in Patent Office: Days
• US Class Current: 370/338
• CPC Class Codes: H04W 36/0055 Transmission or use of information for re-establishing the radio link
• CPC Class Codes: H04W 36/0064 of control information between different access points
• CPC Class Codes: H04W 84/18 Self-organising networks, e.g. ad-hoc networks or sensor networks

Abstract

A method for performing a handover in a mesh network for a plurality of nodes (A, A′, B) of said mesh network from a first access point (AP1) to a second access point (AP2), whereas said plurality of nodes (A, A′, B) forms a tree of nodes, said tree comprising a root node (B) and one or more further nodes (A,A′) connected to said root node either directly or via intermediate nodes, and said handover being performed for said tree of nodes in a coordinated fashion, said method comprising:

• forwarding to said members of said tree (A, A′, B) information about said second access point (AP2) and timing information to enable a coordinated handover of said nodes of said tree; switching said root node (B) and said further (A,A′) nodes from said first access point to said second access point according to said timing information.

Claims

1. A method for performing a handover in a mesh network for a plurality of nodes (A, A′

, B) of said mesh network from a first access point (AP1) to a second access point (AP2), whereas said plurality of nodes (A, A′

, B) forms a tree of nodes, said tree comprising a root node (B) and one or more further nodes (A,A′

) connected to said root node either directly or via intermediate nodes, and said handover being performed for said tree of nodes in a coordinated fashion, said method comprising;

forwarding to said members of said tree (A, A′

, B) information about said second access point (AP2) and timing information to enable a coordinated handover of said nodes of said tree;

switching said root node (B) and said further (A,A′

) nodes from said first access point to said second access point according to said timing information.

2. The method of claim 1, wherein said handover comprises:

determining said root (B) of said tree and said second access point (AP2);

sequentially switching said nodes of said tree starting with said root node (B) followed incrementally by said further nodes according to their sequence into downstream direction.

3. The method of claim 1, further comprising:

generating a handover request message by a node (A) in said mesh network;

forwarding said request message starting from said node into upstream direction up until an authority can determine said root of said tree (B) and said first access point (AP1), and

in response to said handover request message, determining said root node (B) and said second access point (AP2).

4. The method of claim 3, further comprising:

in each intermediate node through which said handover request message passes on its way upstream, collecting information about the access points which are visible to said intermediate nodes and adding said information to said handover request message.

5. The method of one of claim 4, wherein

the various access points in said mesh network or a deciding authority respectively maintain a table about the different access points and the relevant parameters for determining said second access point as a handover candidate.

6. The method of claim 5, wherein said table is fed by information collected by said handover request messages on their way in upstream direction.

7. The method of claim 6, further comprising:

determining said second access point (AP2) based on said information contained in said handover request message.

8. The method of claim 2, wherein the selection of the second

access point (AP2) and the root node (B) of said tree (A, A′

, B) to be handed over is made based on radio resource management considerations.

9. The method of claim 1, wherein

the nodes which are located downstream towards the leafs of the tree either connect to said second access point (AP2) as does said root (B) or maintain connection to their old access point (AP1).

10. An apparatus for performing a handover in a mesh network for a plurality of nodes (A, A′

, B) of said mesh network from a first access point (AP1) to a second access point, whereas said plurality of nodes forms a tree of nodes (A, A′

, B), said tree comprising a root node (B) and one or more further nodes (A, A′

) connected to said root node either directly or via intermediate nodes, and said handover being performed for said tree of nodes (A, A′

, B) in a coordinated fashion, said apparatus comprising;

a forwarding unit for forwarding to said members of said tree (A,A′

) information about said second access point (AP2) and timing information to enable a coordinated handover of said nodes of said tree for switching said root node (B) and said further nodes (A,A′

) from said first access point (AP1) to said second access point (AP2) according to said timing information.

11. The apparatus for performing a handover in a mesh network of claim 10, further comprising:

a determining unit for determining said root (B) of said tree and said second access point (AP2).

12. The apparatus of claim 10, further comprising:

a switching unit for sequentially switching said nodes of said tree starting with said root node (B) followed incrementally by said further nodes according to their sequence into downstream direction.

13. The apparatus of claim 10, further comprising:

a unit for generating a handover request message by a node (A) in said mesh network;

a unit for forwarding said request message starting from said node into upstream direction up until an authority can determine said root of said tree (B) and said first access point (AP1), and

a unit for in response to said handover request message, determining said root node (B) and said second access point (AP2).

14. The apparatus of claim 13, further comprising

a collecting unit for collecting in each intermediate node through which said handover request message passes on its way upstream, information about the access points which are visible to said intermediate nodes and adding said information to said handover request message.

15. The apparatus of claim 14, further comprising:

a maintaining unit for maintaining in an access point in said mesh network or a deciding authority respectively a table about the different access points and the relevant parameters for determining said second access point as a handover candidate, said table being fed by information collected by said handover request messages on their way in upstream direction.

16. The apparatus of claim 10, wherein said apparatus comprises one of the following:

a mobile node adapted to be able to connect to a mesh network;

an access point adapted to operate as an access point in a mesh network.