A Study On Realization Of Mobile Location Using Downlink Of CDMA Communications Systems

Along with rapid development of mobile communication technology and the increase of subscriber number, the mobile communication network have developed into a huge communications network, and a big market of mobile communication is formed. The extension of market, increment in number of users and rapid development of INTERNET let the requirement of users changes continuously , more and more users want mobile communications systems to provide not only voice service but also multimedia, INTERNET and location services .Because of the demand of location service in civil area, researchers began to develop technology used for location service in mobile communication system. The driven force behind the development of this technology is a US Federal Communication Commission (FCC) mandate issued on July 1997 stating that by 1 October 2001 all wireless carriers must provide the geolocation of an emergency 911 caller to the appropriate public safety answering point. After this, mobile location technology was developed very rapidly, applications for the location of subscribers of wireless services continue to expand , many company and academe invested heavily to research and develop this technologyDue to a lot of inherent advantage of it, CDMA have became the main multi access method for the 3 generation mobile communication system(3G), so technologies base on CDMA system attracted more and more attention. Because of neglect of location function in the design of mobile communication system and Multi-Access Interference (MAI), there are a lot of problems still remain in the realization of mobile location in CDMA communication system. In this dissertation, based on the analysis of CDMA system and location techniques the author proposes several method to resolve these problems, the main contributions include1. Two common used channel models have been analyzed, these two channel models are very useful for the research, simulation and assessment of mobile location techniques.2. To decrease the interference of serving base station downlink signal, we propose a method which using Serial Interference Cancellation (SIC) to suppress downlink signal of serving base station. This method is very useful for the realization of mobile location technology in narrow-band CDMA communication system.3. Based on the analysis of the effect of MAI when using OTDOA-IPDL method to position mobile station, we get an decision algorithm through mathematical derivation. Using this algorithm we can calculate the reliability of the estimation of Time of Arrive of downlink signal, get rid of the result that is not reliable, improve the veracity of location estimation.4. For the sake of increasing the number of attended base station to improve the accuracy of location and to mitigate NLOS error, we propose Partial Parallel Interference Cancellation (PPIC) algorithm based on decision method to reduce interference between neighbor base station downlink signals.5. Based on the analysis of NLOS error, we propose using slide and accumulation to increase the performance of NLOS error detector. The purpose of this method is to decrease false alarm probability when mobile terminal near the area between LOS situation and NLOS situation.6. Based on the method proposed by other researchers, we propose using decision, linear regress and adaptive noise cancellation to predict TOA when the measurement result contain NLOS error, and to reduce wide-band fast change error.