Cooperative routing and power allocation in ad-hoc networks

We consider the minimum energy unicast problem in ad-hoc wireless networks. A source node wants to transmit a sequence of messages to a single destination node. Other nodes in the network may operate as relay nodes. The problem is to do this with the minimum overall power consumption in the network. In this paper we investigate the power saving that can be achieved by using advanced relay-channel signaling rather than traditional multi-hop routing. Under the assumptions that carrier level synchronization is not available and every intermediate node uses a decode-forward scheme, we show that any optimal relaying structure can be converted to a sequential path, for which we find a simple optimal power-allocation policy. Finding an optimal sequential path is still complex, and we therefore present two polynomial heuristic algorithms to find good cooperative routes. Our simulation results show that they can achieve average power savings of up to 3 dB for a network size of 60 nodes in low attenuation regimes. For high attenuation regimes, cooperative routing exhibits limited gain and traditional multi-hop operation is a reasonable choice