LOS estimation in overlapped multipath WCDMA scenarios via adaptive threshold

Mobile positioning is a topic of high interest in current mobile communication systems. The position location is usually derived from the estimates of the distances between mobile and the base stations, which are obtained from the time-of-arrival of the line-of-sight (LOS) component. In time-varying multipath fading channels, the LOS component is not always present, and even when it is present, it might be obstructed by one or several components arriving within short delay (i.e., shorter than the width of the main lobe of the pulse shaping function). This situation of overlapped paths is one of the main sources of error in LOS estimation. We introduce here an adaptive threshold for estimating the LOS component in the presence of overlapped multipath components for wideband CDMA (WCDMA) positioning applications. Our threshold technique is used in conjunction with Teager-Kaiser (TK) based delay estimation. The TK estimator was previously introduced in the context of RAKE receiver and it was shown to be an efficient method for solving closely spaced multipaths.