Contention Window-Based MAC Protocol for Wireless Sensor Networks

Existing duty-cycle MAC protocols for wireless sensor networks(WSNs), such as S-MAC, mostly do not consider the influence of inherent traffic distribution characteristic derived from network infrastructure, leading to significant end-to-end delivery latency and poor medium contention handling in data gathering. To mitigate these drawbacks, we propose a novel duty-cycle MAC protocol, called RL-MAC (location-based RMAC). Firstly RL-MAC exploits a location-based configuration strategy to configure nodes with un-uniform CWmin (minimum contention window) values during network initialization, in order to optimize application-level medium access fairness, avoiding packet loss and buffer overflow incurred by mismatches between un-uniform payload distribution over nodes in different position and node-level equal medium access scheme adopted by current protocols. Secondly like RMAC, RL-MAC can forward data packets over multiple hops per cycle through intermediate nodes according to cross-layer routing information, significantly reducing end-to-end delivery latency. Our simulation results obtained on ns-2 show that RL-MAC can better accommodate data gathering applications, providing high throughput and packet delivery ratio without sacrificing energy efficiency.