Decentralized and dynamic route selection in cooperative relay networks

• US 20080075007A1
• Filed: 09/25/2006
• Published: 03/27/2008
• Est. Priority Date: 09/25/2006
• Status: Active Grant

• Current Assignee: Mitsubishi Electric Research Laboratories, Inc. (Mitsubishi Electric Corporation)
• Original Assignee: Mitsubishi Electric Research Laboratories, Inc. (Mitsubishi Electric Corporation)
• Inventors: Zhang, Jinyun, Molisch, Andreas F., Mehta, Neelesh B., Madan, Ritesh
• Granted Patent: US 7,706,283 B2
• Time in Patent Office: Days
• US Class Current: 370/238
• CPC Class Codes: H04B 7/15592 Adapting at the relay station communication parameters for supporting cooperative relaying, i.e. transmission of the same data via direct - and relayed path cooperative diversity H04B7/024
• CPC Class Codes: H04L 45/12 Shortest path evaluation
• CPC Class Codes: H04L 45/24 Multipath
• CPC Class Codes: H04W 40/08 based on transmission power
• CPC Class Codes: H04W 40/22 using selective relaying for reaching a BTS [Base Transceiver Station] or an access point
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

A method selects an optimal route in a cooperative relay network including a set of nodes. For each node in a set of nodes of a cooperative relay network, dynamically varying channel state information is determined. A transmission policy based on the dynamically-varying channel state information is selected, in which the transmission policy includes selected nodes forming an optimal route, a transmission mode for each selected node, and a transmission power for each selected node.

Claims

1. A method for selecting an optimal route in a cooperative relay network including a set of nodes, comprising the steps of:

determining, at each node in a set of nodes of a cooperative relay network, dynamically varying channel state information; and

selecting dynamically a transmission policy based on the dynamically varying channel state information, in which the transmission policy includes selected nodes forming an optimal route, a transmission mode for each selected node, and a transmission power for each selected node.

2. The method of claim 1, further comprising:

transmitting a packet from a source node to a destination node of the cooperative relay network according to the selected transmission policy.

3. The method of claim 1, in which channels between the nodes are subject to time-varying fading.

4. The method of claim 1, in which the transmission modes include broadcasting and beamforming.

5. The method of claim 1, in which the optimal route is a least cost route, and the least cost is based on an amount of energy required to transmit a packet along the optimal route.

6. The method of claim 5, in which the amount of energy includes energy required to acquire the dynamically varying channel state information.

7. The method of claim 1, in which each node determines the dynamically varying channel state information for nodes that are within h hops of the node.

8. The method of claim 7, in which channels between the nodes are subject to fast fading and h≦

2.

9. The method of claim 7, in which h depends on a channel coherence time.

10. The method of claim 1, further comprising:

representing the set of nodes of the cooperative relay network by a graph, in which an edge in the graph represents a channel between two adjacent nodes;

constructing a super-graph from the graph, in which an edge in the super-graph represents a virtual channel between two nodes are separated by at most h hops in the graph;

constructing, for each node in the super-graph, a sub-graph of a subset of the nodes that are separated by at most h hops from the node and the edges that connect the nodes;

determining for every unique pair of nodes in the sub-graph an optimal sub-route; and

selecting the transmission policy based on the optimal sub-routes.

11. The method of claim 10, in which each optimal sub-route has a least cost, and the least cost is associated with the edges in the sub-graph.

12. The method of claim 11, in which the least cost is determined by dynamic programming.

13. The method of claim 11, in which the least cost includes a cost of transmitting a packet, a cost of receiving the packet, and a cost of acquiring the channel state information.

14. The method of claim 12, in which the least cost is distributed to neighboring nodes in the super-graph.

15. The method of claim 1, in which the transmission policy is determined in a decentralized manner by the set of nodes.

16. The method of claim 1, further comprising:

distributing the dynamically varying channel state information among the set of nodes.

17. A method for selecting an optimal route in a cooperative relay network including a set of nodes, comprising the steps of:

representing a set of nodes of a cooperative relay network by a graph, in which an edge in the graph represents a channel between two adjacent nodes;

constructing a super-graph from the graph, in which an edge in the super-graph represents a virtual channel between two nodes are separated by at most h hops in the graph;

constructing, for each node in the super-graph, a sub-graph of a subset of the nodes that are separated by at most h hops from the node and the edges that connect the nodes;

determining for every unique pair of nodes in the sub-graph an optimal sub-route; and

selecting the optimal route based on the optimal sub-routes.

18. The method of claim 17, in which each optimal sub-route has a least cost, and the least cost is associated with the edges in the sub-graph.

19. The method of claim 17, in which the channel between the nodes are subject to fast fading.