| In recent years, wireless sensor networks(WSNs) are widely used in the military area, medical care, environment monitoring、remote control in the hazardous areas and so on. Since the sensor nodes are energy constrained, and after the nodes are deployed, they cannot be recharged. So the research work on how to increase the energy efficiency of wireless sensor networks is always a hot research area. In general, there are many ways to increase the network lifetime. One way is to decrease the total communication traffic by using the data aggregation, data compression, data prediction and duty cycling techniques. The second solution is to design effective network protocols to increase the network lifetime. The last way is to utilize mobility to improve network lifetime. We can also divide this method into two categories:one is to use mobile agent to collect data in order to conserve energy consumption, another way is to balance the energy consumption by introducing the mobile sink.In this paper we made thorough research work on how to increase the energy efficiency of wireless sensor networks, and we’ve proposed many method to increase the network lifetime, the main contributions of my paper are:(1) We have proposed a cross-layer clustering protocol-LEACH-SC which considers the sink’s position and energy.In this paper, we have proposed a novel cross-layer clustering protocol-LEACH-SC(LEACH-selective cluster)) protocol which considers the sink’s position and energy. LEACH-SC first solve the problem of uneven distribution of cluster-head of LEACH protocol. We design a new cluster-head election algorithm which considers the network density, energy and link quality etc. When cluster heads are elected, LEACH-SC, it changed the principle of choosing a communicating cluster head. The nodes choose the cluster head which is the most closest to center point between the node itself and the sink. Therefore the total distance will be shorter, and the total energy consumption will be conserved too. By analysis and through simulation, we found that compared with LEACH, LEACH-SC protocol can greatly reduce the overall network energy consumption, balancing the energy consumption among all the nodes in the network, extending the lifetime of the network. It significantly improved the network’s performance, with the good scalability and robustness.(2)An Energy Efficient Backoff Hierarchical Clustering Algorithms for Multi-hop Wireless Sensor Networks was proposed.As we all known, energy efficiency can be obtained by multi-hop communication., and multi-hop Clustering can decrease the number of "forced cluster-head". In this paper, we integrate the multi-hop technique with a backoff-based clustering algorithm to organize the sensors in wireless sensor networks. The adaptive backoff clustering algorithm not only considers the residual energy, but also realizes load balance among sensor node and achieves fairly uniform cluster head distribution across the network. So the new proposed algorithm is able to significantly prolong system life. At the same time the protocol incurs low overhead in terms of processing cycles and messages exchanged. Based on the energy model in a clustered sensor network, we proved that by choosing appropriate parameters, the volunteer cluster-heads can be evenly distributed in the working region. In addition, simulation results also demonstrate our algorithm is more energy-efficient than the classical ones. In order to meet the requirement of large-scale sensor networks, our algorithm is also extended to generate a hierarchy of cluster heads to obtain better network management and energy-efficiency. By analysis, we can get optimal parameters. And by simulations, we found out that the hierarchical networks have better performance than single-level clustering networks in terms of system life when the network scale is very big and the sink is located far away from the monitoring region.(3) We used the simulated annealing algorithm to solve the routing problem of mobile Agent which is responsible for data fusion.When mobile Agents which are responsible for data fusion are introduced into the wireless sensor networks, the system lifetime can be greatly increased because the communication distance is greatly decreased. But the order and number of nodes on the route traversed by a mobile agent will determine the energy consumption and hence it is desired to choose an optimal route to minimize the total energy consumption so that the system lifetime can be extended to the maximum. The routing problem of the mobile agent in multi-hop networks can be modeled as a traveling salesman problem. So this problem is also NP-complete problem. Taking account of the limited computation ability and limited energy of wireless sensor networks, we present an approximation algorithm which is based on simulated annealing to solve this NP-Complete problem. Simulation experiments demonstrate that the proposed heuristic is more energy-efficient.(4) A new mobile sink strategy called restricted self-determination mobility algorithm (restricted self-determination mobility algorithm, RSMA) is proposed to solve the network hole problem.By introducing the mobile sinks into the wireless sensor networks can balance the energy consumption and prolong the lifetime of the networks. In this paper, we come up with a new mobile sink strategy called restricted self-determination mobility algorithm(RSMA). The new algorithm RSMA control the moving range of all sinks, so the average routing hops can be reduced. When sink nodes decided the moving location, in order to find the more reasonable target location, the RSMA considers the energy, nodes’density etc,which can prolong the lifetime of the networks. Meanwhile, the emergency rescue method, which has been added into our new strategy is able to solve the energy hole problem. In order to further improve the performance of the networks, we propose a new effective routing protocol for wireless sensor networks with multiple mobile sinks which is called Energy balanced and efficient Routing(EBER) protocol. The protocol balance the energy consumption between every branch’s nodes when setting up the routing trees. At the same time, it constrained the maximum forwarding number of every nodes so that it can balanced the energy consumption among the whole tree. Therefore, the system lifetime of wireless sensor networks can be extended greatly. By setting up the simulation platform, we make some comparisons between the UPDA, RSMA and RSMA with the new routing protocols. Simulation results show that RSMA with the new routing protocols can reduce the overall network energy consumption, balancing the energy consumption among all the nodes in the network, prolong the lifetime of the network effectively.This paper’s work are supported by the National Natural Science Foundation of China(60503021,60872018), Jiangsu Province Science and Technology Project(BG2006027, BG2006039) and National S&T Dedicated Mega-Project2011ZX03005-004-03and2011ZX03005-005. |
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