Enhanced Sensor Medium Access Control Protocol for Wireless Sensor Networks in the ns-2 Simulator

One of the most challenging tasks for a wireless sensor network (WSN) is reducing energy waste to increase battery life. This paper examines a popular medium access control (MAC) protocol, i.e., sensor MAC (S-MAC) in the ns-2 network simulator, which has been frequently adopted as a performance benchmark in this field. This paper first proposes a new mechanism for proactive exchanging the status between sensor nodes to prevent unnecessary idle listening by a cross-layer approach that fully utilizes the information from the physical (PHY) layer. Because fatal bugs cause substantial performance degradation, the simulation results of the original module in ns-2 are strongly distorted. Another contribution of this paper is to develop a bug-fixed module. Several graphical illustrations are provided to demonstrate the operation of S-MAC and the effects of improper implementation. Major improvements are addressed in the main text and minor changes are provided in Appendix A. The simulation results show that the actual saturated throughput of S-MAC is approximately two times higher than that of the defect module in the case with bidirectional traffic. In addition, the proposed mechanism can save up to 47% and 25% of the energy for unidirectional and bidirectional traffic, respectively, in a line topology when the traffic is light.