Investigation Of CDMA Mobile Location In Multiuser Environment

In CDMA communication system, because of the inherent multi-access interference and near-far effect, radio measurements like TDOA and TOA, which is ralated to the position of mobile station can be biased, this leads to the performance of location algorithms may be significantly degraded and the position estimation of MS is inevitably biased. Therefore, this dissertation aims at the studying the influence that MAI takes on location accurancy and searches for the method of suppressing MAI when GCC method is employed to estimate TDOA measurement.Based on the study of a lot of related literatures, First of all in this thesis, the research status of wireless location techniques and positioning systems based on cellular networks are summarized. Based on the analysis of several positioning techniques, the thesis focus on the investigation of TDOA location techniques. Then, the cross correlation algorithm to estimate TDOA measurement is introduced and the mathematical model of TDOA hyperbolic equations is established. By analyzing the advantages and disadvantages of several major TDOA location algorithms in detail, Chan's algorithm is selected in location simulation. Besides, among the main factors that reduce location accuracy, MAI and near-far problem are focused on and anti-MAI techniques based on linear multiuser detection and interference cancellation are intruduced, and the performance of this techniques are also compared by MATLAB simulation, the simulation results show that, both techniques can restrain MAI in various simulation environments to some degres. Moreover, the location inplement scheme and simulation results based on SIC, PIC and TDOA techniques are provided. In order to roundly evaluate the prefermance of SIC and PIC techniques, the influences of several parameters to location accuracy are studied by simulation. It's shown that, both methods can effectively suppress MAI, improve the accuracy of TDOA...