Energy-Efficient Route Optimization for Adaptive MPSK-Based Wireless Sensor Networks

We study a certain route configuration problem via optimization theory. We consider the optimal bit error rate (BER) and transmission rate allocations on each hop, 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 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, a mapping can be used to reduce the dimension of the problem by a factor of two; a numerical optimization algorithm has to be used to find the optimum. Simulation results show that by optimally configuring a chosen route, substantial energy savings could be obtained, especially under tight delay constraints. Simulation also reveals that a performance limit is reached as the number of hops increases. A parameter determining this limit is defined, and physical explanations are given accordingly.