Cooperative geographic routing has emerged as an efficient, scalable routing scheme that exploits the merits of physical-layer cooperation to enhance the network performance. In terms of the hop efficiency, an existing scheme called Relay-Aware Cooperative Routing (RACR) investigated how to make use of cooperative diversity for coverage extension, under the strategy of equal power allocation for the source and the relay. The effect of coverage extension, however, dramatically varies with the power allocation over a cooperating pair. In this paper, we address a power-optimized cooperative geographic routing problem based on the RACR scheme. With the joint optimal relaying position and power allocation, the maximum cooperative transmission range is derived. We then, according to the result, present a cross-layer routing protocol toward a fully stateless scheme. Simulation results show that the proposed scheme effectively improves the coverage extension performance as well as reduces the average number of hops.

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