Research On Distributed Topology Controlalgorithm For Energy Saving And Fault Tolerant In Heterogenerous Wireless Sensor Networks

With the rapid development of the Internet of things, wireless sensor networks received widespread attention both home and abroad. Due to the cost and size limitations, the energy of the sensor nodes is always an important issue worthy of attention. Topology control is a key technology to save energy and increase the running time in wireless sensor networks, which can reduce the communication interference between nodes and balance the energy consumption to achieve the purpose of prolonging network lifetime ultimately, while ensuring the network connectivity. In addition, the nodes may be deployed in danger or unattended areas, which are very vulnerable to failure due to the external factors. As a result, the fault tolerance should also be concerned during the energy saving process. When some nodes failed, how to maintain the normal operation of the network is another important topic in wireless sensor networks.In this dissertation, topology control are researched mainly focus on energy saving and fault torelant problem in the heterogeneous wireless sensor network due to the characteristics of sensor nodes that have different computing ablity, communication ablility, and energy level.Energy saving topology control research start with topology construction method, and integrate with topology maintenance strategy to show how to construct and maintain the network topology for the whole topology control process. Then, research the energy balanced routing protocol for energy saving and high coverage on the optimized network topology,which plays an important role for extending the network lifetime. Finally, fault torelant topology control algorithms are respectively researched based on theory research and practical application two aspects due to the characteristics of nodes that are prone to failure, which can save network energy as much as possible while ensuring the fault torelance. The main work and results of this thesis are introduced as follows:(1) In view of the problem that existing topology control methods mainly research ontopology construction or topology maintenance separately, a heuristic algorithm combimed with both processes is presented, which firstly tries to find an optimal minimum connected dominated set for the NP-Hard problem by improving the fitness function, sending message format, and the process of A3 G algorithm during topology construction. Then, a toplogy maintenance algorithm A3 GM combined with topology construction process is proposed by defining three different triggering mechanism, which including time, energy and node failure.When the existing network performance degrades significantly, the Sink node decides to perform local topology repair or global topology maintenance strategies to ensure the stable operation of the network.(2) To reduce the path energy consumption and balance the energy consumption of the dominating node on the optimized topology, an energy-balanced distributed routing protocol EEVB which starting with the Sink node is proposed to solve the problem of the ViTAMin protocol that can only adjust to the homogeneous network, generate too many dominating nodes, cause non-connected network and consume the energy of the dominating nodes not equally. Furthermore, considering the scene with high coverage ratio requirement, a routing protocol EEVBCov meet with high coverage need is extended from EEVB, which tries to cover more network monitoring areas as much as possible while turning off some network nodes.(3) According to the characteristic of topology is prone to be reconstructed in the real environment frequently, a distributed topology control algorithm HELM with low communication overhead is proposed in the hetegenerous wireless sensor network. The algorithm is able to construct connected dominating set quickly with each node only sends one message, which has higher energy efficiency. In addition, the HELMCov algorithm can be extended to get higher network coverage based on HELM to meet with high coverage requirement application scenes.(4) According to the requirement connected dominating set should also have a certain degree of fault tolerance to cope with node failure or link error problem, fully distributed algorithm(k,m)-HELM and(k,m)-HELMCov are proposed for fault tolerance which constructing k-connected m-dominated set for arbitrary k and m values.K-connected guarantees the fault tolerance among the dominating nodes in the network, and m-dominated ensures fault tolerance between ordinary nodes and dominating nodes. The algorithm construct connected dominating set for energy saving or high coverage requirement with low communication firstly, and then make all common nodes m-dominating based on the idea of maximum independent set, finally extend the dominating nodes k-connectivity by thecommon neighbor nodes in the local topology.(5) Research on fault tolerant topology control algorithms in the newly heterogeneous wireless sensor network model which contains a few nodes with self-energized, and propose distributed fault tolerant topology control algorithm EBFT and EBFTCov for both energy-saving and high coverage requirement in view of the problem that the algorithm of(k,m)-HELM and(k,m)-HELMCov produce too much active nodes. The algorithm which not requiring the position information of the nodes choose the larger weight nodes to construct connected dominating set firstly, then select better degree of fault tolerance nodes as backup nodes, and balance the energy consumption of the dominated nodes in the data gathering process finally. It not only reduces the number of active nodes, but also ensures fault torelrance and balances the energy consumption of the nodes to prolong the lifetime of the network.Theoretical analysis and simulation experiments results have proved the efficiency on research all of above. Compared with congeneric protocols or algorithm, the proposed algorithm in this paper can reduce the number of the active nodes produced and decrease more communication overhead, effectively promote the load balance of all the nodes and prolong the lifetime of the network finally.