ABSTRACT
Wireless sensor networks (WSNs) are relatively new technologies used in different civilian and military applications. Typically, a WSN consists of several (hundreds or thousands) sensor nodes, and each node is dedicated to monitor some predefined physical parameter. The sensor nodes can be activated or deactivated dynamically based on the requirements. Figure 1.1 shows a WSN comprising different sensor nodes, access points (i.e., gateways), base station, and servers. A sensor network consists of homogeneous sensors or heterogeneous sensors. In homogeneous sensors, physical properties of all the sensors are the same and dedicated to monitor a particular task. In contrast, a heterogeneous sensor network consists of different sensor nodes having different physical properties and dedicated to perform different tasks in a region. The sensor nodes can be dedicated to perform entity monitoring, area monitoring, and entity-area monitoring. Additionally, a sensor network can perform different tasks in a hierarchical manner, as shown in Figure 1.1. All sensor nodes are homogeneous in nature and send the sensed information directly to the gateways. Similarly, in case of single-tier and heterogeneous sensor nodes, the sensors are heterogeneous and send the sensed information directly to the gateways. In contrast, in multi-tier sensor networks, the sensed information is sent to the gateways in a hierarchical manner, i.e., from one sub-network to another sub-network and eventually, to the gateways. After collecting the sensed information from the WSN nodes, the gateways relay the information to the base stations based on some intelligence. At the server side, the information is computed and processed, and adequate decisions are taken to perform the monitoring task efficiently. The sensor nodes can also communicate with one another to perform the given task in a structured and collaborative manner. Target tracking is one of the applications of sensor networks in which a task is performed in a structured and collaborative manner.
