CDMA mobile station location

This paper outlines research that is applicable to mobile station (MS) location, within code division multiple access (CDMA) systems, using direct sequence spread spectrum (DSSS) signals. There are several CDMA systems either in operation, or at the specification stage world-wide, these include IS-95 in the USA, WCDMA and UMTS. A major implementation issue for selection of an MS location technique, is the synchronism of the CDMA system. CDMA systems can be divided into two main groups in this respect, synchronous and asynchronous. Examples of which, are the IS-95, and UMTS systems, respectively. This paper addresses MS location techniques applicable to both systems. It discusses MS location techniques, using time difference of arrival (TDOA) and time of arrival (TOA) techniques. The MS location techniques in this area have already been the subject of research for application to the synchronous IS-95 system. Modifications to this IS-95 based technique is outlined, for application to asynchronous systems. As an alternative method of MS location, TDOA techniques are applied from a single base station. An approach to MS location, using the technique of beamforming, applied with a signal location algorithm (SLA) is outlined. The paper also discusses the benefits of the inclusion of a tracking algorithm (TA) to the SLA.