Energy Efficient Communication Protocols for Wireless Sensor Networks

Energy saving is a paramount issue in wireless sensor networks (WSNs) as the sensor nodes are expected to have typical life of few years. WSN distributed autonomous devices using sensors to cooperatively monitor physical or environmental conditions, such as temperature, sound, vibration, pressure, motion or pollutants. One of the limitations of wireless sensor nodes is their inherent limited energy resource. Since these devices rely on battery power and may be placed in hostile environments replacing them becomes a tedious task. Besides maximizing the lifetime of the sensor node, it is preferable to distribute the energy dissipated throughout the wireless sensor network in order to minimize maintenance and maximize overall system performance. In this paper various energy-efficient routing protocols were simulated using ns2 and compare among themselves and analyze the energy-efficiency of the system on the basis of the network lifetime. Results show that study the LEACH minimizes energy dissipation by exploiting the data-gathering aspect of micro sensor networks. INTRODUCTION Wireless sensor networks (WSNs) have a wide spectrum of civil and military applications that call for security, e.g., target surveillance in hostile environments. Typical sensors possess limited computation, energy, and memory resources. Over the last half a century, computers have exponentially increased in processing power and at the same time decreased in both size and price. These rapid advancements led to a very fast market in which computers would participate in more and more of our society’s daily activities. In recent years, one such revolution has been taking place, where computers are becoming so small and so cheap, that single purpose computers with embedded sensors are almost practical from both economical and theoretical points of view. Wireless sensor networks are beginning to become a reality, and therefore some of the long overlooked limitations have become an important area of research [1]. A wireless sensor network (WSN) is a wireless network consisting of spatially distributed autonomous devices using sensors to cooperatively monitor physical or environmental conditions, such as temperature, sound, vibration, pressure, motion or pollutants. In addition to one or more sensors, each node in a sensor network is typically equipped with a radio transceiver or other wireless communications device, a small microcontroller, and an energy source, usually a battery. The envisaged size of a single sensor node can vary from shoebox-sized nodes down to devices the size of grain of dust. Eventually, the data being sensed by the nodes in the network must be transmitted to a control center or base station, where the end-user can access the data. Distinguished from traditional wireless networks, sensor networks are characterized by severe power, computation, and memory constraints. Due to the strict energy constraint, energy efficiency for extending network lifetime is one of the most important issues. Sensor nodes are likely to be battery powered, and it is often very difficult to change or recharge batteries for these nodes. Prolonging network lifetime for these nodes is a critical issue. Therefore, all aspects of the node, from hardware to the protocols, must be designed to be extremely energy efficient. The Routing protocol is a set of rules defining the way for router machines to find the way that packets containing information have to follow to reach the intended destination [2, 4]. ENERGY CONSIDERATIONS IN WSNS: The sensor nodes due to their small form factor have limited power. In order to prolong the life of the wireless sensor networks, the routing protocols apart from being robust and scalable, needs to be highly energy efficient. A lot of research has taken place in this direction and various routing protocols are proposed to achieve these objectives. In a fully connected network, all nodes can directly access the base station. However, wireless being a broadcast medium, the congestion in such a network is very high. Typically, each node in a multihop WSN would discover a path to the base station and route its data through this path. This causes the nodes near the base station to be used more frequently than the nodes away from the base station. The reason is the former set of nodes not only send their own sensed data, but are also responsible for forwarding the packets from the far off nodes in the network. This results in a bottleneck around the base station. If the nodes around the base station go dead, then the nodes away from base station will be unable to send the data unless they increase their transmission ranges. Figure 1: Typical sensor network Figure1 shows an example of a typical sensor network. The filled black node is the base station. The lines depict the connectivity and the filled gray nodes are the normal sensing nodes. In this example node-2 and node-3 are one hop nodes. Node-2 is responsible not only for sending its own data but also for forwarding the data from nodes-4, 5, 6, 9 and 10. Similarly, node-3 is responsible for sending its own data and as well as forwarding data of nodes-7, 8, 11 and 12. Thus the nodes situated at a distance of one hop from base station are used more often than the other nodes. It causes such nodes to dissipate energy at a substantially higher rate than the rest of Rakesh Poonia et al, / (IJCSIT) International Journal of Computer Science and Information Technologies, Vol. 2 (4) , 2011, 1697-1699