Detection of a line-of-sight connection to a UMTS base station for increased location accuracy of user terminals

Abstract

The location methods time-of-arrival (TOA) and time-difference-of-arrival (TDOA) become essential for position computation in UMTS networks. During absence of line-of-sight (LOS) propagation, timing errors will occur when these methods are applied. Hence, presence or absence of an LOS connection must be identified. The proposed algorithm detects a LOS connection of a moving user terminal by utilizing the channel coefficients estimated in a UMTS receiver. From the time variations of the first and second path coefficients, measures of the corresponding Doppler bandwidths are calculated. The difference in bandwidth between a reflected path and an LOS path allows a distinction between LOS and non-LOS (NLOS) propagation of the first path. Computer simulations prove the proper operation of the proposed algorithm in typical propagation environments, leading to a reliable indicator for the presence of an LOS connection. Changes in propagation conditions from NLOS to LOS are also tracked quickly.