The Study Of Mobile Location Algorithm Based On Cellular Network

Wireless location, performed either in network or mobile station, is to determine the position of mobile station through the estimated time/angle measurements with the help of location algorithms. The researchers' passion on this field was stimulated by E-911 location rules submitted by FCC in 1996 and promoted further by the inexhaustible commercial potential.Nowadays, each of the communication standards in 3GPP or 3GPP2 has already specified their own location strategy. TD-SCDMA, proposed by China, also performed location as one of its important functions. More and more research results and patents have appeared in recent years.Two main modules are required in an entire location process: estimation of the location parameters and operation of the location algorithms. The time or angle information, which is indispensable to location, is abstracted from the received signal through some parameter estimation algorithms and then input to the location module to yield the location estimation. The primary difficulties lie in the resistance against the estimating errors caused by the severe wireless channel, and the solution to the nonlinear equations which exhibit the geometric relation between the mobile station and participant base stations.Some systematic research work on wireless location has been done after referring to many classic and new materials. This thesis has improved some location algorithms aimed at the key issues. On one hand, this thesis has proposed an improved mobile location estimator based on Kalman filtering. The improved algorithm adopts Kalman filtering to estimate both the measurements and NLOS error, and restructure the real measurements. On the other hand, a Kalman-based interacting multiple model (IMM) smoother is proposed for mobile location estimation. In this thesis, the line-of-sight (LOS), rural, suburban and urban conditions in cellular networks are considered as a Markov process with four interactive modes. Then this thesis proposes a Kalman-based IMM smoother to accurately estimate smooth range between the corresponding base station (BS) and mobile station (MS) Simulation results demonstrate that the performance of the two proposed algorithms suit for the NLOS environment and have higher precision. In addition, in the part of the estimation of the location parameters, DOA estimation with uniform circular arrays via interpolated arrays is proposed. The algorithm is based on interpolated arrays to realize 1-D DOA estimation and can deal with coherent signals. Furthermore, this thesis has summarized the methodology of the research on wireless location. Finally, the summary of all the research content is given, as well as the next step work.