Energy Efficient Cooperative Routing in Wireless Networks

In this paper, we explore physical layer cooperative communication in order to design network layer routing algorithms that are energy efficient. We assume each node in the network is equipped with a single omnidirectional antenna and that multiple nodes are able to coordinate their transmissions in order to take advantage of spatial diversity to save energy. Specifically, we consider cooperative MIMO at physical layer and multi-hop routing at network layer, and formulate minimum energy routing as a joint optimization of the transmission power at the physical layer and the link selection at the network layer. Using dynamic programming, we compute the energy consumption of the optimal cooperative routing in different network scenarios, which shows energy savings of up to 55%, compared with the optimal non-cooperative routing. As the network becomes larger, however, finding optimal routes becomes computationally intractable as the complexity of the dynamic programming approach increases as O(2), where n is the number of nodes in the network. As such, we develop two greedy routing algorithms that have complexity of O(n), and yet achieve significant energy savings. Simulation results indicate that the proposed greedy algorithms perform almost as good as the optimal algorithm and achieve energy savings of more than 50% in the simulated scenarios.