Apparatus and method for estimating the time of arrival of a spread spectrum signal in a wireless communication system

摘要

A threshold tracking loop (TTL) (400) for detecting the time of arrival of a spread spectrum wireless communication signal includes a pseudo-noise (PN) generator (440) for generating a receive PN code for use in spread spectrum decoding and a series of time delay units (401-408) for adjusting a phase offset of the PN code. A first PN despreader (423) is coupled to the time delay units and PN generator for despreading an early pilot signal (413). A second despreader (425) is coupled to the time delay units and PN generator for despreading a late pilot signal (415). A first comparison circuit (443) is coupled to the first PN despreader for comparing a signal value of the early pilot signal with a preselected threshold value (322) and for advancing the PN code phase offset if the early signal value is greater than the threshold value. A second comparison circuit (445) is coupled to the second PN despreader for comparing a signal value of the late pilot signal with the preselected threshold value and for retarding the PN code phase offset if the late signal value is less than the threshold value. The TTL is completed by a loop filter coupled to the PN generator and the first and second comparison circuits.