Towards Balancing Medium Access Energy Trade-offs in Wireless Sensor Networks

In this paper we explore the design of multi-modal MAC for wireless ad hoc and sensor networks that dynamically adapt its behavior in order to minimize the energy to delivery ratio under a wide variety of network loads. The prime motivation is to balance the inherent trade-off between the energy wasted in collisions and the energy expended by collision avoidance handshake mechanisms. Towards this objective, the study goes through two phases. First, we explore the space of MAC modes subject to the constraint that different access schemes can inter-operate. Accordingly, we limit our attention to modes within the non-slotted random access paradigm. Second, we analyze, with the aid of detailed network simulations, the energy performance trade-offs of four variations of the CSMA/CA access scheme. Finally, we shed some light on the problem of dynamically switching between different modes depending on the network loading conditions and application QoS requirements. Initial results reveal interesting observations related to the energy/delivery contribution of channel reservation and single-hop acknowledgment packets under a wide variety of temporal network loads