Optimal code rate for wireless sensor networks using IR-UWB and non-coherent detection

In this paper, a cross-layer design approach has been used to evaluate the effect of forward error correction (FEC) on energy consumption of non-coherent energy detector receiver using impulse radio ultra-wideband in the context of wireless sensor networks. The proposed method captures relevant characteristics of the physical and medium access control (MAC) layers, while taking into account bit error probability (BEP) requirement of the application. A two-stage semi-analytical optimization model and code rate selection algorithm has been developed to find out the optimal code rate from the energy efficiency perspective. Firstly, a signal-to-noise ratio (SNR) gap analysis is used to select the code rates, which can provide the same target BEP as uncoded transmission, with lower received SNR. Secondly, an energy consumption model is used to explore which one of the selected code rates provide the highest energy saving, when compared to the uncoded case. In this work, the proposed algorithm has been executed for Reed-Solomon codes using Nakagami-m fading channel model and taking into account the channel access success probability of the Slotted Aloha MAC for different offered traffic loads. The results clearly illustrate the potential energy savings that can be achieved by using FEC and selecting the optimum code rate. The developed model is useful in the selection of code rate for particular communication distances and offered traffic load values.