Cross-layer energy efficiency analysis and optimization in WSN

Energy conversation is a critical problem in wireless sensor networks (WSNs) so that the energy consumption must be minimized while satisfying application requirements. The energy efficiency can be supported across all layers of the protocol stack. In this paper, we propose and analyze a cross-layer energy efficiency model, which takes routing layer, MAC layer, data link layer, hardware circuitry, and battery discharge nonlinearity into account. For successfully delivering all data generated by source nodes to the sink node with minimal network energy consumption, we consider two orthogonal modulation schemes of M-ary pulse position modulation (PPM) and frequency shift keying (FSK), and distribute an appropriate time slot to every link so that the optimal routing can be obtained. Based on the model, we formulate the optimization problem of minimizing network energy consumption and solve it by existed approaches. The numerical results show that, if PPM scheme is adopted, the cross-layer energy efficiency model with optimal routing has up to 99% lower network energy consumption than that with a uniform single-hop routing in general WSN, and the optimal model also exists 93% energy saving if FSK is used. Multi-hop routing is more energy efficiency than single-hop routing in general WSN, while single-hop routing is more preferable in dense WSN.