Cellular Networks, Wireless Positioning Algorithm

Wireless positioning, performed either in network or in mobile station, is to determine the geographic location 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 regulation 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: 1) estimation of the location parameters and 2) 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 the participant base stations.We have done some systematic research work on wireless positioning after referring to many classic or new materials. In the part of location algorithm, we proposed a Kalman filter-based hybrid location method. Taking advantage of the tracking ability of Kalman filter, this method can provide high accuracy and robustness to the variation of the measured parameters. In the research on NLOS (Non-Line of Sight) error mitigation, three NLOS error mitigation methods were proposed. Based on the analysis on the statistical properties of NLOS error in TOA (Time of Arrival) measurement, we modified the iteration of the standard Kalman filter. These three methods can mitigate the NLOS error in TOAeffectively.Furthermore, we have been trying to summarize the methodology of the research on wireless positioning, trying to tamp the base so as to sparkle the new idea. In the last part, the development of indoor location was presented briefly, which introduced the location method to a new direction as a good example.