Techniques to Improve Ground-Based Wireless Location Performance Using a Cellular Telephone Network

The primary objective of this thesis is to seek a ground-based location scheme suitable for mobile positioning in cellular phone networks. To this end, several techniques are proposed to handle issues that may occur in a cellular network and which may deteriorate wireless location performance. These issues include the lack of signal availability due to co-channel interference, the inefficiency in mobile location calculations, and the significant Non-Line-of-Sight (NLOS) errors resulting from multipath propagation. With the IS-95 CDMA pilot signal as an example, signal availability or hearability is thoroughly analyzed. The analysis shows that hearability is poor for location purposes. To improve signal hearability, two methods that are known to be effective the enhanced signal processing method and the idle period down link (IPDL) method are fully discussed. Another promising solution in poor signal hearability environments is the combination of cellular network-based methods with other positioning methods. As an example, the integration of GPS and a cellular network is proposed. Better location performance can be obtained by epoch-by-epoch Least Squares (LS)-based integration schemes or by Kalman filter-based integration schemes. The position of a mobile handset is normally obtained by solving non-linear equations. However, it represents a high computational burden and may suffer from a convergence problem. To resolve these issues, an enhanced two-step LS solution is proposed for hybrid time difference of arrival (TDOA)/angle of arrival (AOA) wireless location schemes. This method can provide