Optimal beacon interval for TDMA-based MAC in wireless sensor networks

An energy-efficient Medium Access Control (MAC) protocol can significantly elongate the lifetime of wireless sensor networks (WSNs), by reducing the duty-cycle of sensor nodes to an ultra-low level. TDMA-based MACs can greatly reduce idle listening, collision, overhearing and therefore are very energy efficient in data transfer at the cost of requiring tight time synchronization through periodically beacon dissemination. The length of the beacon interval may greatly affect the energy efficiency of a TDMA-based MAC. A shorter beacon interval leads to higher synchronization cost due to frequent beacon sending and receiving, while a longer beacon interval will lead to a larger guard time due to clock drift. Therefore, there is a tradeoff between these two parts of energy consumption. In this paper, we investigate the optimal beacon interval for TDMA- based MAC in low duty-cycle sensor networks, and then present a strategy that adaptively utilizing the optimal beacon interval in a TDMA-based MAC protocol (called Opt-TDMA). Experimental results demonstrate that Opt-TDMA is more energy-efficient than SCP-MAC.