Energy-Efficient Routing in Ad Hoc Networks Relying on Channel State Information and Limited MAC Retransmissions

In ad hoc networks the nodes actively and voluntarily participate in constructing a network and act as relays for other nodes. As a result of node-mobility, the Channel State Information (CSI) varies and hence a substantial amount of control messages have to be exchanged across the network to maintain reliable communications between certain pairs of nodes, which potentially imposes a high energy-consumption. Therefore, minimizing the energy consumption and maximizing the throughput of ad hoc nodes is extremely important. This paper analyzes both the energy consumption and the achievable throughput of a multihop route by exploiting both the CSI quantified, for example in terms of the Frame Error Ratio (FER), as well as the number of Medium Access Control (MAC) retransmissions and the number of hops. Since using limited number of MAC retransmissions in a hop-by-hop retransmission mode imposes dependencies amongst the links of a multi-hop route, a more accurate objective function may be formulated than that which assumes the availability of an infinite number of retransmissions and which considers the links to be independent. Our simulations confirm the improved accuracy of the proposed Objective Function (OF), especially when the FER and the number of hops are high and the number of MAC retransmissions is low. Additionally, a low-complexity routing algorithm is designed, which carries out routing decisions based on the energy consumption predicted by the OF, and strikes a compromise between having ´few long-distance hops´ and ´many short-distance hops´ for the sake of energy minimization and throughput maximization.