AN ENERGY-EFFICIENT MAC PROTOCOL FOR DELAY SENSITIVE WIRELESS SENSOR NETWORKS

Abstract

Energy is the most critical resource in the life of a wireless sensor node. Therefore, its usage must be optimized to maximize the network life. MAC layer has a significant impact on energy efficiency as it directly controls radio activities. However, lowering the energy consumption may result in higher latency. To address such a tradeoff, there is need to design a MAC protocol having good latency performance with the energy consumption at a reasonable level. Several solutions to MAC problem have been proposed. S-MAC is proposed which is specifically designed to reduce energy wastage on IEEE 802.11 based sensor nodes. The fixed duty cycle design in SMAC trades off latency for saving the energy consumption. It is efficient for energy utilization, but not suitable for delay-sensitive sensor applications such as medical, battlefields, disaster relief. In this dissertation work, a new energy efficient Dynamic Duty Cycle MAC (DDC-MAC) and Unified Dynamic Duty Cycle MAC are proposed. DDC-MAC minimizes the latency by tuning a duty cycle to the node according to traffic of the node and average latency experienced by that node. In DDC-MAC, each sensor node follows multiple listen and sleep schedules. Therefore they switch into the listen state frequently and reduce the network lifetime. To minimize energy consumption due to multiple listen and sleep schedules, UDDC-MAC is proposed in which Schedule Unifying Algorithm (SUA) is integrated with DDC-MAC so that multiple listen and sleep schedules into a single unified sub-optimal schedule. We study the performance of the proposed protocols by simulating it using NS-2 and compare it with D-SMAC, S-MAC (Full), S-MAC (10%) in terms of average energy consumption of a node and average end to end latency experienced by the packet. The simulation results show that UDDC-MAC achieves improved latency performance and is more energy efficient than DDC-MAC, S-MAC and DS-MAC.