Recent developments in wireless systems and electronics have led to design of low cost, low power and tiny sensor nodes with sensing, processing and transmission capabilities. These sensor nodes have energy, memory and process limitations. These sensor nodes might be used to monitor different environmental parameters such as temperature, humidity, pressure, vibration intensity, pollutant levels or vital body functions. Other applications of Wireless Sensor Networks (W) include military systems, health care monitoring, environment and habitat monitoring, home automation, space exploration, chemical processing and traffic control. The most important constraint of these sensor nodes are their limited available source of energy. Therefore, sensor processes such as routing algorithms should make the best use of this limited resource. A number of energy aware routing algorithms have been proposed in the literature to increase the network lifetime. These routing algorithms usually try to find the path with minimum energy usage. However, using these paths for a long period of time may result in rapid energy depletion of some nodes. To overcome the above problem, in this thesis, we propose an Energy Aware Routing Algorithm for wireless sensor network. The proposed algorithm is named Enhanced Lifetime Maximization Algorithm (ELMA) for Wireless Sensor Networks. This algorithm tries to distribute the traffic loads over the entire network and avoids rapid energy depletion of the nodes on the shortest path using alternate paths. ELMA uses two simultaneous strategies to achieve this goal. First, it calculates or estimates the average energy of the network and only the nodes whose energies are greater than this calculated or estimated average energy of the network can participate in relaying the messages. Second, the proposed algorithm selects the path with maximum ratio of energy to a function of hop count in each transmission round, which tries to ensure using alternate paths. In comparison to LMAWSN (Lifetime Maximization Algorithm for Wireless Sensor Network), ELMA simultaneously maximizes both the network lifetime and the number of received data packet to the sink. This ensures that the lifetime maximization will not happen at the cost of network packet delivery. ELMA has three different versions which differ on the calculation or estimation method of the average network energy. As the size of the network increases, the simulation results indicate that those sensors close to the sink node will consume their energies faster than other sensor nodes, since, they need to forward a larger number of messages to the sink node. Therefore, to extend the lifetime of the network, using multiple Keywords: Wireless sensor network, Routing Algorithm, Energy Aware Routing, Load balancing technique, Lifetime, Multi sink.
