IMPROVING THE LIFESPAN OF WIRELESS SENSOR NETWORKS VIA EFFICIENT CARRIER SENSING SCHEME - CSMA/SDF

Wireless Sensor Networks (WSNs) refers to a group of spatially dispersed and dedicated sensors for monitoring and recording the physical conditions of the environment like temperature, sound, pollution levels, humidity, etc. WSNs are deployed where manual intervention and wired infrastructure installation is not feasible. Lifetime of WSNs is of major issue. Energy efficient WSNs are to be deployed to improve the network lifespan instead of replacing nodes frequently which is of high cost. In this paper, we propose CSMA/Shortest Data First (SDF) an energy efficient MAC protocol, to increase the network lifetime. CSMA/SDF modifies existing CSMA/CA protocol which is completely contention - based, by introducing a higher priority to the node with shortest data du ring channel access contention process. CSMA/SDF employs a distributed shortest - data - first scheduling algorithm and Anti - Starvation mechanism to allow nodes with long data also given chance to get channel access. CSMA/SDF thus reduces overall energy consum ption which in turn increases network life. It also efficiently utilizes channel by reducing the probability of occurrence of collisions. The proposed solution is simulated using a discrete event network simulator, ns2.35 on UBUNTU 12.04 LTS 64 bit Operati ng System. The simulated results of CSMA/SDF outperforms CSMA/CA by reducing carrier sense time by 42% and overall energy cost by 24% and improving channel utilization up to 46% and throughput by 36%.