Study On Fault-tolerant Mechanism And Algorithms In Wireless Sensor Networks

Wireless sensor network (WSNs), composed by a large number of randomlydeployed sensor nodes in the detection area, is a multi-hops self-organization networksystem in wireless communication way. It can real-time monitor, perceive and acquirethe monitored object’s information. Wireless sensor network is an important carrier ofInternet of Things (IOT) and the key technology of future extension of Internetcoverage and pervasive computing. Its rapid development leads to the comprehensivepromotion of Internet of Things in information awareness, information interoperabilityand intelligent decision-making. It shows great widespread application in many fieldsand becomes the hot spot in present study.As a new distributed computing platform of information acquisition and processingtechnology, wireless sensor network has characteristics of no center distributed network,dynamic topology changes, restriction of communication, computing power and energysupply. Additionally, unpredictability exists in the working scenario of network due tothe environmental interference of vibration, electromagnetism, system noise, randomnoise and so on which can lead to incorrect perception packets. Owing to movingbeyond the scope of communication, objects blocking, channel interference and datacollision, it will lead to link quality variation, temporary or permanent network fault orfailure in data transmission. Therefore, the transmission reliability and working stabilitywill be affected in wireless sensor networks. More challenges are brought toself-organization ability, adaptability and robustness of the network. High reliability andstability are still the difficult technical issues in the present study on wireless sensornetworks.Fault tolerant strategy can improve the operation robustness and transmissionreliability of wireless sensor networks. The nature of fault tolerance is to seek thereasonable fault-tolerant control scheme, adaptively process a variety of networkanomalies and continues to provide high credible computing services when somethinggoes wrong with the network system. However, the fixed structure based network cannot meet the large-scale extensible requirements of wireless sensor networks. Inaddition, the network has characteristics of complexity and diversity and is restricted bythe conditions of practical application. Existing fault-tolerant models simply extract fault features and lack of the ability of independent online learning to new failurecharacteristics. This seriously affects the accuracy and robustness of fault tolerance.Aiming at the new failure characteristics, further study should be carried out based onthe framework structure establishment of dynamic-adaptive and online fault-tolerantdesign.Therefore, for the issues that the fault of nodes or links and the working scenariowill affect the transmission stability and reliability in the network layer, This studyadopts the initiative fault prevention strategies before the abnormity and fault tolerantstrategies after the abnormity to improve the network reliability mainly in network layer.These strategies include the optimization of multi-path transmission routing algorithm,joint-control optimization on cross layers, introduction of modern intelligent bionicalgorithms which are based on the mechanism of bionics and immune to study the faulttolerance and reliable transmission in network layer. The details are as follows:(1) According to the inspiration of bionic intelligent algorithm of ant colony to thefault routing establishment in wireless sensor networks, a non-uniform clusteringrouting algorithm is presented with the function of fault tolerance. According to thecharacteristics of vascular network, mathematical model and network topology areestablished. Improved particle swarm optimization (IPSO) is studied and adopted to dothe non-uniform gradient static clustering. Best and worst ant system (BWAS) isintroduced to create fault toerant transmission paths between the neighbor hierarchicalclustering heads. Normalized values of ant pheromone are adopted to be as the pathselecting probability of transmission path. Performance of fault tolerance and algorithmcomplexity are theoretical analyzed. Packet receving rate, average transmission delayand energy consumption balance are simulated.(2) For the issues that the coding mechanism can affect the transmission reliabilityin wireless sensor networks, multi-paths and erasure encoding based reliabletransmission strategy (MPE2S) is presented. Nodes in the network are hierarchicaldetermined and pheromone values are calculated by BWAS. According to thepheromone normalized values by BWAS which reflect the links quality, a transmissionfault-tolerant mechanism of disjoint multi-paths is established among the adjacenthierarchical clustering heads. The algorithm optimizes erasure coding and establisheserasure coding based multi-path load balance mechanism. It allocates the erasure-codedfragments from source packet to multiple paths for transmission. Mathematical model is established to do the theoretical analysis. Simulations are carried out to test performanceof load balance and fault tolerance.(3) For the issues that the gradient can affect the performance of transmissionreliability and fault tolerance, a gradient based multi-path reliable transmission strategywith fault tolerance is presented for wireless sensor networks. Firstly non-uniformclustering topology is established in non-equal clustering probability based on twiceK-means algorithm. Then it calculates the comprehensive measurements (CM) ofclustering heads by the quality evaluation function and establishes the contour lines.Finally gradient based multiple disjoint transmission paths are established by themechanisms of load balance and linear erasure coding. It establishes the transmissionmathematical model to analyze the network performance. Simulation shows that thisstrategy has good performance of fault tolerance. It improves the transmission reliabilityof the network and energy efficiency.(4) For the inspiration of immune system mechanism to improve fault toleranceand transmission reliability for improving the overall performance of wireless sensornetworks, mechanism of immune system based multi-path fault tolerant routingalgorithm is presented. It studies mechanism of the immune system, artificial immunesystem model and properties associated with fault-tolerance in wireless sensor networks.Basic issues are defined such as immune clustering, immune multi-path and so on.Mechanism of immune system is adopted to establish the hierarchical clusteringtopology with optimal performance of clustering compactness. Mechanism of immunesystem is also applied to do the variation and optimization on the initial antibodypopulation, namely the multiple disjoint paths, to establish the final optimaltransmission paths. Mathematical model is established to do the theoretical analysis onthe performance of the algorithm. Through the simulation on the packet receiving rate,accuracy rate and energy efficiency, the algorithm improves the transmission reliabilityandenergy efficiency of the network. It shows superior performance of fault tolerance.In conclusion, this study aims at improving the transmission reliability and runningstability in wireless sensor networks. It establishes theories and methods related withfault tolerance based on the previous studies. Furthermore, bionic intelligentfault-tolerant system is established to improve transmission reliability and stability. Itprovides theoretical and technical support to warning system by wireless sensornetworks in the domains requiring high reliability performance such as industrial monitoring, mine safety monitoring and agricultural biological environmental protection,etc.