Research On Key Technology Of Passive Locating Based On Wireless Sensor Network

In order to adapt to various and ubiquitous communication technology in the future,electromagnetic spectrum monitoring is developing along the trend of networking, beingsupported well by the appearance and development of WSN. Passive locating for emitter ofelectromagnetic signal is one of the important components of electromagnetic spectrummonitoring, and implementing passive locating with high precision based on WSN with limitedresource and ability is confronted with numerous difficulties and challenges. This dissertationfocuses on this problem and does researches mainly including four aspects as follows:Firstly, aiming at the demand of limiting data communication amount in TDOA estimationbased on WSN, the TDOA estimation method with low data amount based on phase data hasbeen studied. After analyzing the impact of bad phase unwrapping effect caused by non-flatpower spectrum to TDOA estimation for narrow-band communication signal based ongeneralized phase spectrum method, a modified weighted least squared fitting method isproposed. Then in demand of controlling data transmission amount, a lightweight TDOAestimation procedure combined with the modified phase spectrum method is designed, under thefrequency domain data compression criterion based on extracting sub-band with most signalpower. Taking general digital communication signal as example, simulation and analysis showthat, the modified method has better robustness against phase unwrapping effect, can improveTDOA estimation precision obviously for narrow-band communication signal compared withoriginal phase spectrum method, and the lightweight TDOA estimation produce can implementdata compression for TDOA estimation for narrow-band communication signal, balance welllTDOA estimation precision against energy consumption and time delay in sensor node.Secondly, aiming at the problem that conditions for TDOA locating based on WSN areconstrained, the improved Chan algorithm based on maximum likelihood criterion has beenstudied. Aiming at the problem that Chan algorithm has multiple solutions, a location ambiguityelimination method based on maximum likelihood criterion is proposed. In order to modifylocating performance in bad condition with large TDOA measure noise or short base-line, to beclose to CRB, an approximate maximum likelihood estimation method is proposed to correct thelocating result given by Chan algorithm iteratively. Simulation and analysis show that, theproposed location ambiguity elimination method can select the optimum one from the set ofsolutions when prior information about position of emitter is unkown, and comparing withoriginal Chan algorithm, the improved algorithm has better robustness against TDOA estimationprecision and length of base-line, has also a small calculation amount, so can improve theusability of TDOA locating scheme for application in WSN. Thirdly, aiming at the problem of distributed and cooperative locating with highperformance based on WSN, RSSD/TDOA cooperative locating method based on clusteringWSN has been studied. RSSD locating scheme is the extension of RSS locating scheme inuncooperative locating application, which is not relying on the reference node information, itsCRB is deduced and analyzed, and a least squared locating algorithm is proposed also. Aftersummarizing these works above, a cooperative locating procedure based on clustering WSN isdesigned: in the frist round, making a primary estimation of emitter position by RSSD, andcalculating the CRB of TDOA locating of each cluster, then in the second round, selecting a fewclusters with high expected locating precision to make further estimation by TDOA, and fusingall results. Simulation and analysis show that, RSSD/TDOA cooperative locating scheme canmanage sensor nodes effectively according to dynamic passive locating task, reduce the energyconsumption and time delay for locating obviously, extend the lifecycle of network, improve theperformance of monitoring, while enough locating precision is still achieved.Fourthly, RSSD/TDOA cooperative locating scheme is realized on DSP platform.Cooperative locating scheme is divided into several modules, and programme of each modules isdesigned. The test on hardware platform of electromagnetic spectrum monitoring node confirmsthe feasibility of the cooperative locating scheme.