ABSTRACT

In wireless sensor network the efficient use of energy leads to enhance the network lifetime. As idle listening, collision, control overhead and over hearing are the main reasons of energy waste. Many typical MAC protocols are designed to conserve energy and enhance network lifetime. In this paper we propose a new contention based energy efficient protocol called Extended S-MAC (EX-SMAC) for wireless sensor networks. It is designed with three main features namely Low duty cycle, less number of collisions and minimum overhearing. As the name indicates it is the extension of S-MAC protocol, so this paper also eliminates the long latency of packets at intermediate nodes which is one of the demerits of SMAC. Sensor nodes in Extended S-MAC have a very short listening time, hence reduces the energy required to communicate with other nodes i.e. idle listening. Also the number of collisions in cases where two or more nodes try to send packets at the same time is minimized in Extended S-MAC, hence retransmission cost for lost packets reduces and also overhearing by other nodes is also minimized by this protocol by having a very short listening time for each node of the sensor network. With such improvements over existing MAC protocol the performance is expected to be much better.