The Research Of Energy Efficient Routing Protocols For Wireless Sensor Networks

Wireless sensor networks consist of massive sensor nodes which are randomly deployed in monitoring region, forming multi-hop self-organized network systems through wireless communication. Due to the limited energy of sensor nodes, how to effiectively use energy to prolong networks lifetime is one of the most important research topics for sensor networks.We emphasize on wireless sensor networks routing technology aiming to improve the energy efficiency. At first, we investigate the system structure, the characteristic and the key technologies of wireless sensor networks. According to specific application demands in wireless sensor networks, we classify the existing typical routing protocols, and analyzed their design characteristics.The clustering protocols can decrease the transmission of redundant data and increase energy efficiency though data aggregation. LEACH is a typical clustering protocol, and it has some disadvantages such as random selection of cluster heads and large cost of inter-cluster communications. We propose two improved algorithms: MST-LEACH and MDT-LEACH. These two algorithms adopt the same strategy of choosing cluster heads. The value of every node's available energy is mapped into time delay, and the node priority of being cluster head depends on its available energy. Hence, the node with sufficient energy will be chosen as cluster head in every region, and cluster heads are uniformly distributed in the whole network. At the stage of inter-cluster communications, we adopt multi-hop communications and determine the routes according to the dada aggregation requirements. The minimum spanning tree is used in the communications of cluster heads when the inter-cluster data aggregation is needed (MST-LEACH), while the minimum distance tree is used when the inter-cluster data aggregation is not needed (MDT-LEACH). Simulation results show that these improved algorithms has better energy efficiency than LEACH.To alleviate the cluster head dependence of existing clustering protocols, we propose a novel ring-based topology, and designed an energy-efficient ring-based hierarchy routing protocol: RHR. This protocol divides the whole network into many homocentric rings, and maintains many energy sufficient routes between neighboring rings. The regular updating of key nodes leads to more balanceable energy consumptions. Every bland node has many key nodes for transmission, which increase the robustness. Furthermore, we optimize the network's parameters for constant bit rate (CBR) applications, so that the updating cycle is optimized and the updating overhead is minimized. Simulation results prove that this new protocol can prolong network lifetime efficiently, and its energy efficiency is better than LEACH, especially in large scale wireless sensor networks.In order to solve the problem of "energy tundish" in multi-hop communications, and balance node energy consumption over the whole network, we propose a novel multi-hop communication algorithm with redundant cluster heads. This new algorithm groups all cluster heads into a grid-mesh network. We calculate the energy consumptions of different communication modes base on the mesh network, and prove that the multi-hop communications is the one with least communication cost. Then we deploy the redundant cluster head nodes in every position of the grid, and calculate the optimal number of redundant cluster head nodes according to the relay payload. The cluster head nodes work/sleep in turn to balance the energy consumptions. Simulation results show that this algorithm can effectively balance the cluster heads' energy consumptions and prolong the network lifetime.