Research And Implementation On UWB Indoor Positioning System Based On Asynchronous TOA Estimation

Impulse Radio Ultra-Wideband(IR-UWB) is a newly developed short-rangewireless technology which is quite different with traditional wireless techniques. It hasattracted great intention by researchers from academy and industry in recent years, forits broad application prospects in communication, precise ranging and positioning,detection imaging and so on. IR-UWB uses baseband pulses with very low powerspectral density and very narrow pulse width to carry information, it occupies a greatbandwidth, obtains high time resolution and has a good multipath resolving ability, andalso it can be able to penetrate the barrier, thus it is considered to be a very competitivecandidate achieve in precise positioning of indoors.The subject starts from the demand of indoor high-precision positioning, fully tapto explore the IR-UWB signal strengths in ranging and positioning aspects, find asuitable solution for indoor precise positioning and verify its positioning performanceby actual test. The specific study includes the following aspects:Firstly, focus on the positioning method based on the asynchronous estimated timeof arrival (TOA). Typically TOA or TDOA positioning method will encounter thedifficult problem of clock synchronization, but the two-way ranging mechanism inasynchronous TOA positioning method supplies a good clock synchronization solutionand achieves low complexity. At the same time, contray to the complex anchor nodeaccess mechanism problem in a standard TOA method which based on the two-wayranging, proposing an improved asynchronous TOA positioning method based on thetwo-way ranging, and providing the low complexity anchor node identificationmechanism. Using this method, the TOA measurement and the anchor node codingwork can be finished in one time,and the positioning initiation is completely determinedby the user, all anchors are fully capable of asynchronous work, this is very suitable fordynamic deployment network.Secondly, the positioning performance of the system based on the differentpositioning algorithms are compared for analysis. In a localization system typicallycontains several anchor nodes, the distance equations based on ranging are in generalnonlinear, a computation intensive method is to linearize them first and then solve theequations iteratively. Using the root mean square error of positioning results asperformance indicator, to analyze the impact of the LS, the recursive LS and WLS threedifferent algorithms on the positioning accuracy and compare them with the CRLBbased on TOA estimation. Finally, based on the existing laboratory digitize ultra-wideband systems platform,the UWB positioning prototype system was successfully constructed, conducting theimproved asynchronous method with the real positioningalgorithm and systemperformance actual test. When the anchor node works in the reasonable configurationcircumstances, using recursive LS solving method to deal with distance equations canhave a good performance with the positioning error is less than30cm.