Research Of Location And Tracing Algorithm In Cellular Networks

Frequently, people need for the position information of themselves or some special objects in working and living time, but the ability of current location service and technology can not meet the need. Thus, there exists a great potential prospect for the location technology of cellular networks. Location technology of cellular networks has its own merits such as low expense and high coverage, however, it also suffers from the problem of inadequate precision.The essential reason of the inadequate precision problem in cellular network location is the unpredictable characters of the wireless channel. Firstly, this thesis studies the characteristics of wireless channel to establish the theory basis, and then introduces the prevalent wireless channel models in the filed of radio positioning. The error introduced by Non-Line-Of-Sight (NLOS) is the most important reason in all the factors which degenerate the location precision. This thesis mainly considers how to mitigate the impact of NLOS error and the measurement error by the way of enhancing the robustness and applicability of location algorithm. The achievements of other researchers are summarized, and two kinds of classical location algorithms, Taylor series estimation and Chan estimation, as well as a NLOS mitigation algorithm are presented in details. The merits and flaws of these algorithms are also analyzed. A mended NLOS mitigation algorithm is proposed, and the simulation results have proved that the enhancement of the proposed method is obvious.Tracing is a special occasion in the location service application, and there are some details such as space-time correlation of sequent measurements, prior information of object motion and geographical information could be used to improve the location precision. Because the particle filter is applicable for non-Gaussian and non-linear system, this thesis also introduces the basic principle of the particle filter and the usage of this kind of filter in tracing, and presents a map-aided tracing method based on the particle filter. New method has good performance in accuracy and Real-time ability in simulation circumstance. Finally, this thesis makes a conclusion of problems to be resolved and discusses the research points which are worth to study in future.