Study On The Quality Of Localization Guarantee Strategy In Wireless Sensor Networks

With the fast development in sensor technology, intelligent computing, Micro Electro Mechanical System(MEMS), embedded technology, wireless communication and so on, it is increasingly realistic to implement Wireless Sensor Networks(WSNs) as a novel information acquistion and processing technology in realistic world. WSNs have given voice to academia, industrial community and government. One of main functions of WSNs is sending the collected environment information to users who are interested in it, or processing the data to make the decision whether there is an event in the monitoring area and send the decision to users. In most application in WSNs, it makes no sense if the collected information was not bound with location information. For instance, in event detection applications, we should not only decide whether the event happen correctly, but also know its position precisely. In object tracking, knowing the nodes'locations is the precondition of localizing the traced objects. Consequently, node localization has become one of basic problems which should be solved expectively in WSNs.In static sensor networks with low beacon density, iterative localization(that is the unknown nodes can be localized by their neighbor nodes who have been localized) can enhance node localization ratio, but if the error propagation problem in iterative localization was not delt with properly, node's location precision would be exaggerated remarkable, which couldn't meet the requirement. According to this problem, an iterative node localization algorithm based on Particle Filter with error control strategy is proposed in this paper. First, an elaborate node localization algorithm based on Particle Filter is proposed, in which node's location is estimated by a series of particles along with their weights. The particles are gradually updated by the posterior distribution of node's location. At last, nodes are localized with the centroid of all the sampled particles. Second, in order to suppress, a novel concept called Degree of Inconsistency(DoI) is proposed. Dol makes use of the fact in WSNs that node density is high and the nodes are uniformly and randomly distributed. The number of nodes in an unit area follows Poisson distribution with the mean of node density. The localized nodes with large error could be gradually identified by Dol and the estimated locations are then updated gradually in order to improve accuracy and suppress error propagation.In mobile sensor networks, a novel range-free localization under the circumstance that the mobile beacon is moving under Gauss Markov model is proposed. The algorithm estimates the location of unknown nodes according to two or more groups of bound lines which are formed when the moving beacon enter and leave the communication range of unknown nodes. The algorithm only need to compute the point of intersection of bound lines, which reduces computation complexity. Nodes'locations are the centroid of the points of intersections. What's more, the proposed algorithm can update nodes'estimated location when the precision don't meet requirement, which enhance localization precision gradually.