Research On The Techniques Of CDMA Territorial Cellular Subscriber Position Location

There has been a long history with wireless position location techniques. The fast development in techniques and the rapid growth in demand for cellular communications services have been encouraging research into the deployment of wireless position location techniques in civilian applications. In June 1996, the Federal Communications Commission (FCC) of United States created rules that require cellular service providers to provide the position of cellular 911 callers to Public Safety Answering Points. The accuracy requirement of the E-911 mandate was initially set to within 125 metres for 67% of users and within 300 metres for 95% of users. In the final phase of E-911 mandate, these numbers are subsequently reduced to within 50 metres and 150 metres for handset-based solutions, 100 metres and 300 metres for network-based solutions, respectively. In many applications with special purposes, such as emergency, national security and military deployment, subscriber position location is very necessary.This dissertation addresses problems of locating cellular subscribers and focuses on the theory and applications of position location techniques in cellular networks, especially in the widely deployed cdma2000 1x and IS-95 CDMA systems. These key issues include signal hearability on reverse channels, bounds on parameter and location estimations, location algorithms with LOS or NLOS measurements and the implementation of a third party(passive) subscriber position location system based on TDOA measurements.First of all, signal hearability is thoroughly analyzed with cdma2000 1x signal as an example. "Average accquisition probability" and "average accumutive accquisition probability" are introduced and used as performance criteria for the capability of location system coverage. The analysis shows that hearability is poor for location purposes. To improve signal hearability, a scheme is proposed that signal interception and subscriber position location are implemented on reverse access because larger time-bandwidth production can be achieved. Simulation results show that there is great performance improvement in signal interception probability.A key aspect of subscriber location is the estimation of the channel and channel parameters whose estimation accuracy determines the reliability of location estimation. The channel parameters of interest include the strength of arrival(SOA), angle of arrival (AOA), time of arrival(TOA) and time difference of arrival(TDOA). After presenting the temporal and specular propagation model, the CRLB on channel parameter estimation is derived. Then the CRLBs for the estimation of subscriber location under two scenerios ---- single user and multiple users ---are derived and thoroughly analyzed. Analysis results show that the CRLB under circumstances where many cellular phones work simultaneously is independent on multiple access interference.The subscriber position is normally obtained by solving nonlinear equations. However, it represents a high computational burden and may suffer from a convergence problem. Different...