Residual energy-based transmission schemes for event reporting wireless sensor networks

WSNs are complex systems that are mainly limited by the battery life of the nodes in order to have an adequate performance. In most cases, it is possible to have a re-deployment of new nodes in order to prolong the systems lifetime. This leads to a situation where some nodes have a low energy level while other nodes (the majority of nodes instants after the re-deployment procedure) have high energy levels. In this environments, it is clear that ancient nodes, those with low energy level, have to contend for the shared medium against the majority of high energy nodes. As such, the remaining battery life of low energy nodes would be rapidly consumed. In this paper, we propose to extend the battery life of low energy nodes by means of assigning prioritized access to the shared channel to those nodes in order to content among a low population of such nodes, while delaying the contention access of high energy nodes which can support higher number of collisions before energy depletion. This is done by studying two different transmission strategies referred to as “hard” and “soft” transmission probabilities. Results show that, a soft transmission strategy achieves better results in terms of reduced energy consumption than both the conventional protocol or a hard transmission assignment.