Enhanced TOA estimation through tap candidate extraction for positioning in multipath channels

Abstract

Positioning systems are essential in most of the current wireless devices applications. For that reason, a seamless positioning service is desired even when global navigation satellite systems (GNSS) are not available. Positioning systems based on observed time difference of arrival (OTDOA) such as Long Term Evolution (LTE) or the incoming 5G, result a good positioning alternative for those GNSS-disabled situations. Errors in the time of arrival (TOA) estimation can arise from non line-of-sight (NLOS) propagation conditions or multipath channels with weak line-of-sight (LOS). This manuscript elaborates on TOA estimation based on considering several first-arriving path candidates per channel. We present a new method for multipath TOA estimation through a statistical analysis of the cross-correlation. The selection of the TOA candidates can be performed with an adaptive or fixed threshold proposal. Performance analysis has been carried out with a LTE setup in terms of the cumulative distribution function (CDF) of the horizontal position error. Simulation results show that the proposed solution improves the position accuracy with respect to a traditional positioning scheme in harsh multipath propagation conditions.