Synchronization to pseudo random number sequence with sign ambiguity in communications systems

摘要

A method is disclosed for synchronizing, in the presence of sign ambiguity, to a pseudo random maximal length sequence having a characteristic polynomial of order k with a coefficients vector A given by: A=[1 a1 a2 . . . ak-1 1]where each of the coefficients a1 to ak-1 is 1 for an intermediate tap location and otherwise is 0. A received symbol sequence is supplied to and shifted through a K=k+1 stage shift register with P intermediate taps in positions determined by a coefficients vector Ain given by: Ain=[1 +E,ovs a+EE 1 (a1(+)a2) (a2(+)a3) . . . (ak-2(+)ak-1) +E,ovs a+EE k-1 1]where +E,ovs a+EE 1 and +E,ovs a+EE k-1 are the inverse of a1 and ak-1 respectively and (+) denotes a modulo-2 sum, whereby the shift register has P intermediate taps where P is a positive integer less than K. A respective correlation signal is recursively added at an input for the received symbol sequence and at each intermediate tap. Each correlation signal is produced by correlating the P+1 signals from said input, intermediate taps, and output other than the signal to which the respective correlation signal is added. The invention is particularly applicable to pilot synchronization in CDMA terminals./!