Patent ID: 6201828
Filing Date: 2001-03-13
Classification: H04B

Abstract:
In a spread-spectrum radio communication system in which transmitted signals are spread according to one or more pseudonoise (PN) code sequences into PN chips of predetermined duration, the system having a searcher for estimating transmission delay of a transmission by:receiving the signal;correlating the received signal against a plurality of sequences of local replicas of said PN codes, each local replica sequence starting at an offset a predetermined positive real number ""delta"" of PN chip durations later than its predecessor;accumulating a correlation value corresponding to each local replica sequence; andestimating the transmission delay as a number of PN chip durations equal to a delay of a local replica sequence associated with a greatest one of said correlation values,a method of refining the transmission delay estimate comprising the steps of:determining a magnitude Co being a magnitude of said greatest one of said correlation values;determining a magnitude Ce being a magnitude of a correlation value associated with offset of a local replica sequence immediately prior to said local replica sequence associated with said greatest one of said correlation values;determining a magnitude Cl being a magnitude of a correlation value associated with offset of a local replica sequence immediately after said local replica sequence associated with said greatest one of said correlation values;determining a transmission delay increment equal to ##EQU4##and adjusting the transmission delay estimate by the amount of the transmission delay increment.