Layered CSMA- A MAC protocol for multi- hop wireless sensor networks

A Wireless Sensor Network is a network of numerous wireless sensor nodes where every node is equipped with capability of receiving and forwarding the data to the other nodes by using radio frequency. The sensor nodes receive data packets from different nodes and forward these packets towards a central location called sink (Base station). These nodes consume energy for sensing, computations and communications purposes. The nodes have a limited power backup in form of battery, so the MAC protocols for WSNs aim to minimize the energy consumption of nodes. In WSN, the network performance is mainly measured by energy efficiency and lifetime of sensors. The MAC layer is responsible for the establishment of a reliable and efficient communication link between WSN nodes and is responsible for energy waste. The newly proposed contention based MAC protocol Layered-CSMA in this paper uses an improved variant of CSMA which had major problems like hidden/exposed nodes. The proposed protocol is aimed at minimizing the energy consumption in network thereby increasing the network lifetime. The proposed method divides the network area into different layers based on their geographical locations. Each layer is assigned a different status. The lower status means the layer is at a greater distance from the base station. The results confirm that the proposed scheme outperforms the existing LCSMA technique in multiple ways. The energy consumption is greatly reduced and the constraint to work only in linear topology is also removed. The key idea of this model is creating multiple layers wherein a node with lower status always sends data to another node with higher status and ultimately making it reach the central location base station. The methodology has been simulated in matlab and graphical results generated to establish validity of the model.