Enhanced timing advance in TDM cellular radio systems

The rationale for this Letter is to present a method which would enhance the resolution and accuracy of timing advance (TA) in 2G GSM TDMA and 3G UMTS TDD networks. The method would enable a stationary or slow-moving mobile station (MS) to determine its location using trilateration, with enhanced resolution and accuracy. An outstanding feature of the method is that the only changes required are to software. Low resolution TA samples would be processed into enhanced resolution measurements by applying fractional bit perturbations (dither) over an extended sampled measurement period. The existing TA mechanism and word length for ensuring correct MS uplink arrival times would remain unchanged. It is proposed that enhanced timing advance (ETA) could provide a low risk, low cost alternative to location finding technologies such as angle of arrival, time of arrival, enhanced observed time difference, uplink time difference of arrival and GPS, at the same time satisfying the FCC mobile E-911 accuracy requirement.