Modeling optimum ETSP protocol for WSN

A fundamental design issue for wireless sensor network (WSN) protocols, applications and services is to introduce energy-efficiency to extend network lifetime. In this paper, we mathematically model and optimize our proposed energy-efficient time synchronization protocol (ETSP [21]) that provides significant energy improvements over compared time-synchronization protocols, namely reference broadcast synchronization (RBS [15]) and time-sync protocol for sensor networks (TPSN [16]). ETSP switches between RBS and TPSN based on the network density and improve over RBS and TPSN respectively. In the proposed protocol, we identify the conditions to switch between RBS and TPSN based on a threshold value of the number of neighbors at given node. We experimentally and mathematically derive an optimal value of the switching threshold for sensor motes hardware. It is shown that our proposed protocol results in reduced number of transmissions (message exchange) and is therefore, energy-efficient as compared to its existing counterparts. Moreover, we assess the performance of our protocol on the bit error traces collected over a WSN testbed to verify the analytical results.