An Efficient Duty Cycle Mac Protocol for Wireless Sensor Networks

Abstract

The problem of idle listening is one of the most significant sources of energy consumption in wireless sensor nodes. Many techniques have been proposed based on duty cycling to reduce this idle listening. This thesis presents Adaptive Scheduling Predictive-Wakeup MAC (AS-PW-MAC), a new MAC protocol based on asynchronous duty cycling. AS-PW-MAC uses receiver-initiated data transmission in order to efficiently and effectively operate over a wide range of traffic loads. AS-PW-MAC attempts to minimize the time a sender and its intended receiver occupy the wireless medium to find a rendezvous time for exchanging data, while still decoupling the sender and receiver‟s duty cycle schedules. In AS-PW-MAC, nodes wake up to receive at randomized and asynchronous times. AS-PW-MAC introduces RTE and RAS messages for pending data transmission. These messages are called Request to Extend and Resilient Active Scheduling. RAS is the time duration of nodes to stay awake for extended amount of time. RTE and RAS are beneficial for varying traffic loads. We evaluate the performance of AS-PW-MAC through detailed ns-2 simulation and compare it to RI-MAC and PW-MAC, two well-known MAC protocols. Our evaluation includes clique, grid and random network scenarios. In all experiments, AS-PW-MAC significantly out performs RI-MAC and PW-MAC protocols. AS-PW-MAC achieves higher packet delivery ratio under a wide range of traffic loads compared to RI-MAC and PW-MAC. Especially, when there are contending flows, such as bursty traffic or transmissions from hidden nodes, AS-PW-MAC significantly improves the packet delivery ratio and delivery latency. For example, with 15 concurrent transceivers in the network, the delivery latency for AS-PW-MAC is less than 21% compared to RI-MAC and PW-MAC. In all experiments, AS-PW-MAC maintained approximately 100%.