Research On Method For Survivable Topology Control In Wireless Sensor Networks

The survivable topology control is one of the important supporting technologies of wireless sensor networks. It can enhance survivability of topology of wireless sensor networks when working in adverse or hostile environment, and extend the working lifetime of sensor networks application system. The topology improves quality of service of wireless sensor networks. Aiming at topology division caused by node failure in wireless sensor networks deployed in harsh environment, survivable topology control takes into account how to maintain survivability of topology to reduce the impact on survivability of topology due to node failure.In recent years, with the rapid development of MEMS technology, hardware performance of a sensor node continues to increase, and there is considerable enhancement in the node computing power, power supplying capacity, the capability of communication and so on. However, the cost of the replacement of power supplying module of node in harsh or hostile environment is still larger, and longer working lifeime of the wireless sensor networks application system still has practically great significance to ender users. On the other hand, while peocessing the survivability of topology for wireless sensor networks, the current efforts to survive topology control of sensor networks only make a qualitative assessment, lacking of quantitative evaluation mechanism of topology survivability. Therefore, the current works can’t effectively guide the further operation of topology maintenance. Based on the summary of survive technologies of topology control in WSNs and the other related works, the thesis focuses on research of survivable technology of energy-efficient topology control in sensor networks using redundant multiplexing and the quantitative evaluation of topology control survivability. The main works of the thesis are as follows:(1) The related research works on survivable topology control in wireless sensor networks are comprehensively investigated and analyzed from three aspects of energy-efficient topology control, fault-tolerant topology control and intrusion-tolerant topology control. And the ideas of these works are summarized and their advantages and disadvantages are presented. Finally, we point out the challenges existing in survivable topology control of WSNs.(2) We propose survivable topology control mechanism based on energy-aware cluster-head election and active node using time-slice in a cluster. The thesis takes into account the situation where the randomness of the number of cluster heads generated and the randomness of the distribution of cluster heads can’t guarantee balanced energy consumption of nodes in WSNs. The mechanism avoids nodes with low energy to be elected as cluster head by means of using the energy factor during cluster-head selecting. At the same time, the thesis uses redundant time-multiplexing mechanism to share the task of cluster head in a cluster in order to realize balanced energy load of each node in a cluster. Simulation results show that the mechanism effectively overcomes the uneven energy consumption of nodes in LEACH protocol and avoids the problem that the energy depletion of a single node leads to degradation of survivability of sensor networks while having much energy in the whole networks. It can postpone the time of nodes’death and enhance survivability of topology in WSNs.(3) In order to provide decision-making guidance for sensor networks to launch a new round of topology update or self-regeneration operation, we propose a quantitative evaluation model of topology intrusion-tolerance capability based on semi-Markov process (SMP). When WSNs launch topology update or self-regeneration due to node failure caused by fault or intrusion, topology survivability must be correctly evaluated. Taking into account many restrictions such as weak node computing, scarce storage and communication capabilities, we avoid describing the complexity of modeling for different threats of invasion and simply model in the unified level of invasion results. We define three properties of topology intrusion-tolerance for evaluation, including availability, stability and service rates, and use the embedded DTMC model to solve these three indexes. By designing Bayesian network inferring model of intrusion tolerance indexes, we improve the assessment accuracy of intrusion-tolerance ability of topology. We analyze two survivable topology control mechanisms, and simulation experiments verify validity of the model proposed.(4) We propose topology coverage hole-patching method (PATT) that gradually adds mobile nodes to repair coverage holes triangle by triangle. For the hybrid sensor networks having a small amount of mobile nodes, we are inspired by the triangular mesh model in computer graphics and study mobile-node-supported topology self-regeneration method. Coverage holes must be repaired when sensor networks topology is separated due to node death in order to make the nodes distributing as evenly as possible to cover the monitored area and to ensure networks topology to survive long. We theoretically prove an optimal location of mobile nodes and it has more than 90% sensing coverage by deploying mobile nodes to appropriate location. Using auxiliary information provided by border nodes of coverage holes and triangular patch, the thesis gradually adds mobile nodes to improve the ability of sesnsing coverage and communication coverage. It enhances survivability of sensor networks topology and is proved to be optimal theoretically.(5) We design a multi-hop routing algorithm based on survivable clustering topology control in wireless sensor networks. We choose agricultural precision irrigation as application background of survivable topology control, and design multi-hop routing algorithm based on survivable clustering topology to enhance survivability of sensor networks application system. On the other hand, we use adaptive weighted data fusion algorithm to improve processing accuracy of collected data. A prototype application system of survivable sensor networks for agricultural precision irrigation is implemented. Simulation experiments show the prototype system can setup correctly and run distributed, possessing many advantages, such as strong survivability, good extensibility, and so forth.The survivable topology control method proposed can further apply in wireless multimedia sensor networks and is able to evaluate quantitatively survivability of wireless multimedia sensor networks. When designing a routing algorithm, we can also exploit the method proposed by the thesis.