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Energy Aware Routing in Wireless Sensor Network.


Wireless sensor networks (WSNs), comprising of large numbers of tiny sensor nodes, find their applications in all aspects of human life. Some of these applications are surveillance and monitoring system, structural health monitoring, forest fire monitoring, habitat monitoring, border monitoring, combat zone monitoring, crop monitoring, medical care, security system, nuclear protection and measurement systems, biological applications, health applications, chemical attack recognition and the fields where wires could not be used. Sensor nodes used in WSNs are resource-constrained in terms of their radio range and battery power. In most of the applications it is very difficult to recharge their batteries. Therefore, they need careful energy management. Such energy management is also affected by the way the data from source to sink is routed. Performance metrics of routing protocols in wireless sensor networks are also different from those used in traditional networks. In contrast to traditional networks, energy is the major point of focus in the development of routing protocol in wireless sensor network. Optimized consumption of energy is thought to ensure a long lifetime for a wireless sensor network.

In this dissertation, the main focus of our work is to explore all possible energy efficient approaches for the problem of data routing through energy-constrained sensor nodes in wireless sensor networks. In the first part of the dissertation, a gradient of cost fields is exploited to explore the energy-efficient routes for the delivery of data from any source node to the sink. The proposed, GRAdient Cost Establishment (GRACE), routing strategy is based on two cost factors: energy and link quality. A routing path is selected if it contains both high-power nodes and good-quality wireless links. In other words, GRACE operates on the optimized selection of paths that have lowest costs in terms of energy and link quality. In this way, GRACE reduces both energy consumption and communication-bandwidth requirements and prolongs the lifetime of the wireless sensor network. Using theoretical analyses and computer simulations, it is shown that the proposed dynamic routing, GRACE, helps achieve the desired system performance under dynamically changing network conditions. A comparison of the proposed strategy, GRACE, with one of the best existing energy efficient routing algorithms GRAB has been presented which shows a better performance of GRACE over GRAB. Moreover, it is observed that operation initialization and status updation exert significant impact on the performance of a routing algorithm in a wireless sensor network. For this purpose, various modes of operation for updating status are explored and their impact is shown on the lifetime curves of GRACE strategy.

Although GRACE is an energy-aware routing protocol designed specially for resource constrained wireless sensor nodes, however, limited battery resource at a sensor node coupled with the hostile multi-path fading propagation environment makes the task of the network to provide reliable data services with an enhanced lifetime challenging. The focus of the second part of the dissertation is, thus, to propose an energy-aware routing protocol embedded with transmission power control (TPC) mechanism. In the second part, the main operation of the proposed strategy, Adaptive Power Control-based Energy Efficient Routing (APCEER), is two fold. On one hand, it tries to establish gradient-based energy-efficient routes from source to sink and on the other hand, it forces every node on the route to exploit the minimum possible power level to transmit data to its next-hop neighbor, while maintaining a reliable wireless link. This two-fold operation not only saves the energy of each and every sensor node in the network but it also reduces the network-wide communication interference significantly. This energy-saving results in an overall increase in network lifetime and transmission throughput of the network. Computer simulations and test bed measurements are presented that show that APCEER outperforms the existing energy-aware routing strategies, not equipped with a power control mechanism. It can thus be used in urban applications of wireless sensor networks where ultra-efficient utilization of energy, by power-constrained nodes operating in severe fading conditions, is needed.

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