Investigation Of Location Algorithm Of NLOS Error Mitigation In Cellular Networks

Since FCC submitted E-911 location regulation, corporations all around the world have established their location system schema based on GSM,IS-95 and 3G, due to the compellent demands controlled by the government and the prompting drived by the market itself. Till now, it has made some great progress, but still be with some differences between E-911 demands and the practice in precision. Because of the existence of the nonideal channel condition and no-line-of-sight transmission between the MS and Base Station (BS) in general in the cellular location, NLOS error mitigation has become a key technology and hotspot in the research about Wireless Location.The no-line-of-sight error mitigation is studied in the paper. Firstly, higher-order statistics and second-order statistics estimating methods are expounded and analyzed in order to offer mathematical theory to the following. Secondly, based on deep analysis and numerous discussion of electric wave of NLOS transmitted characteristic and transmitted model, some representative NLOS error mitigation algorithms are compared. After analyzed many based range scale restrained algorithm, an effective method is proposed---NLOS statistical property and range scale restrained algorithm are integrated. We firstly correct TDOA by NLOS statistical property, then use recurrence equation to correct coefficient in order to mitigate NLOS error and to transform NLOS transmitted signal into LOS signal or near to LOS signal. Lastly mobile location is estimated by least square method. This method not only avoids NLOS statistical model's localization, but also lessens the number of repetition of range scale restrained algorithm. Simulation and comparison of performance with other existing methods have shown its effectiveness of no-line-of-sight error mitigation in location estimate and improve location accuracy.Nowadays, some methods have been proposed in some papers to eliminate or mitigation the effect of the no-line-of-sight error. But their effectiveness of no-line-of-sight error mitigation in time of arrival or time difference of arrival is not very valid. Therefore, no-line-of-sight errors have become the crucial factor on the enhancement of location accuracy in the Cellular Network, and it is necessary to make much more investigations.