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Top1. Introduction
A sensor network is basically an infrastructure comprising of sensing (measuring), computing, as well as communication components that affords an administrator the capability to instrument, speculate, and respond to various events and phenomena in a specific environmental setup. The environment can be the real-life physical world, or a biological system, or an information technology (IT) framework. Sensors are employed in many days to day objects like touch-sensitive elevator buttons as well as lamps that either dim or brighten through touching the base, besides numerous application domains of which most people are never aware. With advancement in micro machinery as well as microcontroller platforms, the usage of sensors have expanded beyond the traditional fields of temperature, pressure or flow measurement. Moreover, analog sensors such as potentiometers and force-sensing resistors are still widely deployed. Many applications include: cars, medicine, robotics, manufacturing machinery, airplanes and aerospace, and many other applications in our day-to-day life. Sensor network comprises of a large number of sensors that are deployed either inside the phenomenon or very closer towards it. Further, the location of sensor nodes need not be predetermined. The sensor nodes are normally scattered in a sensor field. Besides, each of the scattered sensors is capable of collecting as well as routing data back to the sink (Akyildiz et al., 2002). Further, data are routed back to the sink by multi hop. There are diversified application domains of wireless sensor network to tackle several difficult real-life circumstances viz. flood situations, military applications, forest fire, vehicle tracking etc.
Basically, Wireless sensor networks (WSN) consist of spatially distributed autonomous sensors for trapping the physical or environmental parameters like: temperature, sound, pressure, etc. for cooperatively passing their data through the network to a main location. In recent days, the networks are bi-directional, that enables the control of sensor activity. The advancement of WSN was motivated by various military applications like: battlefield surveillance etc. Recently, such networks are deployed in various industrial as well as consumer application domains, such as industrial process tracking and control, machine health monitoring etc. The WSNs consist of nodes – from a few to several hundreds or thousands and every node is connected to one or more number of sensors. Every node consists of many parts such as: a radio transceiver with an internal antenna or connection to a special external antenna, a microcontroller, an electronic circuit for interfacing with the sensors and an energy source, usually a battery or an embedded form of energy harvesting. Moreover, a sensor node may vary in size from that of a shoebox down to the size of a grain of dust. In like manner, the cost of sensor nodes is variable, ranging from a few to hundreds of dollars, depending on the complexity of the sensor nodes. Size and cost constraints on sensor nodes give rise to corresponding restrictions on resources like: energy, memory, computational speed as well as communications bandwidth. Further, the topology of the WSNs can vary from a simple star network to an modern multi-hop wireless mesh network. In recent trends of computer science as well as telecommunications WSNs are active research fields with thousands of workshops and conferences organized each year etc.
The primary goal of Wireless Sensor Network (WSN) is to sense and send the sensed data to the destined user. However, the requirement is to prolong the longevity of the network. Basically, the lifetime of a network is the amount of time that a WSN would be fully in operational mode. In other words, it is the time at which the first network node runs out of energy for sending a packet for losing a node could mean that the network would loss various functionalities. On the contrary, it is also feasible to use a separate definition, where some of the nodes may die or run out of battery power, when the other network nodes would be deployed to trap the desired information or for routing the desired messages to their intended destined destination. Since the devices are having limited amount of battery power, the energy management is highly necessary.