Decentralized and dynamic route selection in cooperative relay networks

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

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

selecting, in the system 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, in which each node determines the dynamically varying channel state information for nodes that are within h hops of the node, where h is a number of the hops.

2. The method of claim 1 , further comprising:

transmitting a packet from a source node to a destination node of the cooperative relay network along the optimal route 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 channels between the nodes are subject to fast fading and h≦2.

8. The method of claim 1 , in which h depends on a channel coherence time.

9. 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.

10. The method of claim 9 , in which each optimal sub-route has a least cost, and the least cost is associated with the edges in the sub-graph.

11. The method of claim 10 , in which the least cost is determined by dynamic programming.

12. The method of claim 11 , in which the least cost is distributed to neighboring nodes in the super-graph.

13. The method of claim 10 , 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 1 , in which the transmission policy is determined in a decentralized manner by the set of nodes.

15. The method of claim 1 , further comprising:

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

16. 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.

17. The method of claim 16 , in which each optimal sub-route has a least cost, and the least cost is associated with the edges in the sub-graph.

18. The method of claim 16 , in which the channel between the nodes are subject to fast fading.