Perfect link routing for energy efficient forwarding in geographic routing

Geographic routing has been widely advocated for use with multihop ad hoc and sensor networks because of its scalability and use of only local information. These types of networks typically have lossy links where the instantaneous quality of a wireless link can vary significantly presenting a trade-off between hop length and link quality. In this paper we revisit the question of energy efficient geographic routing for such networks and argue in favour of Perfect Link Routing, an extreme form of blacklisting with a fall-back option. Existing research has favoured cost-based methods where all links are considered for routing. We argue, however, that a discontinuity exists between the cost of perfect links (those with virtually guaranteed delivery) and other links. This is based on a more careful use of acknowledgements which we suggest ought to be considered a function of individual links. Revisiting the original analysis we find that for energy efficiency, perfect links should be favoured except in low-density networks where such a scheme leads to very poor delivery rates. A hybrid approach is proposed which we call Perfect Link Routing and this method is shown to outperform alternatives for a number of ARQ schemes.