Research Of Energy Balanced Directional Transmission Opportunistic Routing Protocol For Wireless Sensor Networks

As one of the most important technologies in the 21 st century, wireless sensor networks(WSNs) have attracted a lot of attention. WSNs have been used for many long-term applications such as military surveillance, disaster and scientific exploration, environmental monitoring. WSNs are composed of a great number of battery-powered sensor nodes which are distributed in a certain area and they communicate with each other over the radio. Traditional wireless network routing protocols try to find the shortest path, and send data along this path. They face difficulties in coping with unpredictable and unreliable wireless medium and cannot adapt to the unreliability nature of the WSNs. Sensor node has limited available energy. It is usually difficult to recharge or replace the battery. When designing routing protocols for wireless sensor networks, energy efficiency is one of the core concerns in order to extend the network lifetime.Opportunistic routing protocols make full use of the broadcast nature of wireless channel to allow multiple forwarders to opportunistically deliver packets from a source to a destination, which is different from traditional routing protocols. Opportunistic routing protocols can better cope with the lossy, unreliable and varying link qualities of wireless networks and effectively improve network performance. However, this kind of protocols also faces some problems, such as forwarder list selection, duplicate transmission, diverging paths, energy efficiency and so on.In this dissertation, a new routing protocol, called Energy Balanced Directional Transmission Opportunistic Routing Protocol(EBDTOR) is proposed. It combines the geographical position of sensor nodes with the opportunistic routing. In EBDTOR the sensor area is divided into grids of fixed size. When a source node tries to send a packet to the destination node, the source node draws a virtual line to the destination node on behalf of the transmission direction. Only the nodes near the virtual line can participate in data forwarding. Limiting the locations of nodes can avoid diverging path and reduce the control overhead. When choosing the forwarder node for the received packet, residual energy of all the candidate nodes is also taken into consideration. The node having higher residual energy and closer to the destination at the same time will have a higher probability to be selected as the forwarding node. Simulations results show that EBDTOR can effectively prolongs the network lifetime and reduce the end to end delay.