TDOA Positioning in Downlink versus Uplink of a W-CDMA Network

Inhalt:
The wide deployment of cellular communication systems has opened great potential for location-based services. In particular, in the 3GPP standardization community, investigations have been started to introduce an uplink-based positioning method in addition to the already standardized downlink alternative. In this paper the time difference of arrival (TDOA) positioning in the downlink versus uplink for a W-CDMA network is investigated. A systemlevel environment is presented for comparison of the positioning accuracy. For various estimation algorithms with varying degrees of accuracy and complexity described in the literature, a generic performance assessment in terms of the Cramer-Rao lower bound (CRLB) is carried out. Specifically, the well-known single-path CRLB concept is extended to a multi-path environment and an improved 2-dimensional shadowing model is introduced. The analysis and simulations show that the downlink estimation method has several advantages and outperforms its uplink counterpart.