Study Of Mobile Station Positioning Technology In CDMA Networks

With the rapid development of the wireless technology, the value-added service related to mobile unit positioning is becoming more and more important. Recently, mobile unit positioning becomes an import part in 3GPP, therefore, the study of mobile unit positioning in a CDMA network is very significant.In many location methods given in 3GPP, the one based on Time Difference Of Advance (TDOA) is used widely. Many methods, studied by scholars at home and abroad, are feasible, however, their precisions are degraded due to the Multipath Effect and Non Line Of Sight (NLOS). The state equations and statistic characteristics of signals are difficult to get, therefore, there is no ideal model for relatively precise positioning available.A new approach is proposed in the thesis. The cellular cells is considered as a Complex Adaptive System (CAS), and Evolutionary Computation is used to obtain solutions and location information. A Particle Swarm Optimization algorithm (PSO), which used to simulate the action of birds assembling and flying to the habitat, is applied to solve the positioning problem. Then the thesis adopts a Vector Evaluated PSO algorithm and improves it by selecting different step length in different situations. The simulation results show that the improved algorithm is robust and relatively accurate.