On Alleviating Starvation in Wireless Sensor Networks

Current CSMA-based MAC protocols for wireless sensor networks (WSNs) do not support prioritized channel access and often suffer from varying degrees of starvation and fairness problems. That is, with a little bad luck, a sensor node might have to wait arbitrarily long to send its frame, and thus results in the invisibility of some sensed area. In this paper we introduce a simple, but yet well performing starvation-free backoff scheme based on sensor MAC (S-MAC) protocol for wireless sensor networks. The proposed scheme allows a sensor node to adjust its backoff window size according to its re-transmission times. An analytical analysis is carried out to study the saturation throughput of proposed scheme under backlogged conditions. In addition to the theoretical analysis, simulations were also conducted to analyze the proposed scheme and the results show that our scheme can effectively alleviate the starvation and fairness problem and achieve better performance in high density sensor networks.