Selection metrics for multihop cooperative relaying

Cooperative relaying enables nodes to actively cooperate to deliver packets to their destination. The best-select protocol (BSP) implements a type of cooperative relaying that generalizes single path routing with sets of nodes (relay-sets) replacing the concept of a single node relay. Thus, while in traditional single path routing, packets hop from node to node, in BSP, packets hop from relay-set to relay-set. Through the exchange of channel gain information between relaysets, the best node within a relay-set is selected to transmit the data packet on behalf of the entire relayset. The node selected depends on the metric used. Any metric that can be posed in a dynamic programming framework can be used. In this paper, performance gains from a number of selection metrics are investigated. Specific selection metrics include maximizing the probability of packet delivery, maximizing the minimum channel gain along the path, maximizing the throughput, minimizing end-to-end delay, minimizing the total power, and minimizing the total energy. It will be shown that BSP can achieve significant gains in all of these metrics, with the possible exception of maximizing the probability of packet delivery. The performance is investigated with several different propagation models and node densities.