(A) look-ahead scheduling MAC protocol for large-scale wireless sensor networks

Abstract

Energy is the most important resource in wireless sensor networks (WSNs) because they are operated by built-in batteries. One of the major causes of wasted energy comes from an always-on wireless network interface to accept possible traffic, so many Medium Access Control (MAC) protocols have taken a periodic sleeping scheme for energy saving, though they sacrificed a latency and throughput instead. Moreover, their latencies increase more with multi-hop forwarding which is basic nature of WSNs. In this paper, we suggest Look-Ahead Scheduling MAC Protocol (LAS-MAC) that aims to high performance as well as energy efficiency. LAS-MAC reserves channel schedules of multi-hop nodes before their corresponding data transmission, and then the sensor nodes wake up and transmit data by following the schedules. In addition, LAS-MAC consecutively reserves the next channel schedule for throughput by piggy-backing the next schedule information in data packet, and gives an energy-efficient congestion control algorithm. The performance of LAS-MAC is evaluated through ns-2 simulations. The results show that, with a relatively small packet-error rate, the latency of LAS-MAC is as low as that of an 802.11-like MAC without sleeping and the energy consumption of LAS-MAC is more efficient than that of Sensor-MAC. Moreover, LAS-MAC (TC-MAC) achieves better throughput than 802.11-like MAC without sleeping with efficient congestion control and fairness management.