Adaptive route configuration for increased energy efficiency in wireless sensor networks

In this paper, we discuss a certain route configuration problem via optimization theory. The problem is potentially relevant for designers of both wireless sensor and wireless ad hoc networks with multihop and link adaptation capability. We consider the optimal bit error rate (BER) and transmission rate allocations subject to overall BER and delay constraints for a designated route. The pivot of the problem lies in the delay constraint, which divides the problem into two cases - the loose delay and the tight delay case. In the former, analytical solutions are obtained by applying the Karush-Kuhn-Tucker (KKT) theorem. Specifically, we discover in this case that for a given target BER, the optimum solutions are only related to the hop lengths in the route. When the delay constraint is tight, there exists a mapping which can be used to reduce the dimension of the problem by a factor of two; however, a numerical optimization algorithm has to be used to find the optimum. The problem can however be shown to be a convex optimization problem, which ensures that any local minimum will be global. Simulation results show that by optimally configuring a chosen route, substantial energy savings could be obtained, especially under tight delay constraints.