With almost its applications in every field, WSNs are creating the myriad of opportunities every day. Though WSNs have entered into new application domains, these applications might require stringent requirement in the network design. The monitored sensor field plays an important role in determining the network size, topology and the type of deployment. For example, if the sensor field is a large region in a hazardous environment then a Wireless- Adhoc network is preferred over a preplanned network. Similarly, open sensor fields demand a larger number of nodes to cover a large region whereas the lesser number of nodes is required for closed sensor fields to form a network in a smaller area. Further, each sensor node of the WSN is facilitated with short distance communication, limited energy source, narrow bandwidth, and less processing capacity and limited storage. Each node consists of the sensing unit, the communication unit, and computation unit. Nodes are energized by primary batteries. Therefore the energy is a chief concern. Especially when the sensor fields are enemy zones, impenetrable areas like forests and hilly terrains and other hazardous environments, the only way to deploy them are in a random manner. In such conditions, it is difficult to replace the exhausted batteries.
Further, many a time the sensor nodes are abandoned for the very important reason that their batteries are drained out. However, the rest of the subsystems of the node are in perfect health condition. The significant share of the energy budget is consumed by the communication unit. Therefore the important bottleneck is to ensure lower power consumption in challenging environments of the sensor field where sensor nodes are to be deployed. Hence past and present research work has been focused on the development of protocols for power conservation. These protocols, in general, provide trade-offs to the end user so as to prolong the network lifetime.
Most of the present methods are based on the simulations, and these simulations have assumed homogeneous energy consumption rates of batteries. Further, they are also based on the ideal discharge characteristics of the battery. When theoretical calculations of the lifetime of the sensor network based on the simulations were compared with the practical deployments of the sensor networks, the observed lifetimes are far less than the calculations based on the simulations, owing to battery untimely death.
This is due to the reason that the most of the researchers did not consider battery as one of the important and critical elements which have a decisive role to play while determining the WSNs lifespan. And most importantly there was not enough work seen emphasizing on the Electrochemistry related characteristics of the battery such as Rate capacity effects, Recovery effects, and Thermal effects which get affected by the sensor node parameters like power level of the transmitted data packets, Sampling interval, and Transmission time. Furthermore, most importantly the environmental conditions in which the sensor nodes are placed are not taken into consideration.
The proposed issue invites the papers based on the practical results emphasizing the lifetime extension of the Wireless Sensor Networks.