On geographic collaborative forwarding in wireless ad hoc and sensor networks

In this paper, we study the geographic collaborative for-warding (GCF) scheme, a variant of opportunistic routing, which exploits the broadcast nature and spatial diversity of the wireless medium to improve the packet delivery ef-ficiency. Our goal is to fully understand the principles, the gains, and the tradeoffs of the node collaboration and its as-sociated cost, thus provide insightful analysis and guidance to the design of more efficient routing/forwarding protocols. We first identify the upper bound of the expected packet ad-vancement (EPA) that GCF can achieve and prove the con-cavity of the maximum EPA. With energy efficiency as a ma-jor concern, we propose a new metric, EPA per unit energy consumption, which balances the packet advancement, reli-ability and energy consumption. By leveraging the proved properties, we then propose an efficient algorithm which se-lects a feasible candidate set that maximizes this local met-ric. We validate our analysis results by simulations, and justify the effectiveness of the new metric by comparing the performance of GCF with those of the existing geographic and opportunistic routing schemes.