Patent ID: 7302268
Filing Date: 2007-11-27
Classification: H04B,H04L

Abstract:
1. A method for a radio receiver to acquire timing information for a radio transmitter that transmits, in a time-slotted arrangement in which each time slot is divided into chips, a signal which includes a sequence of chips that indicates the slot timing, has a length at least equal to a known minimum length, and is repeated in the signal with a known periodicity, the method comprising the steps of: (i) receiving a number of consecutive chips of the signal that is at least sufficient to include two repetitions of the sequence; (ii) forming a first group of the received chips at least equal in number to the known minimum length and a counterpart group of the same number of received chips but offset from the first group by the known periodicity, each group having a first chip and a last chip; (iii) for each chip in the first group and its corresponding chip in the counterpart group, performing a correlation operation to obtain a correlation value for each of the corresponding pairs of chips; (iv) summing the obtained correlation values to obtain a correlation sum and storing the obtained correlation sum; (v) obtaining a next correlation sum by: (vi) storing the next correlation sum obtained in step (v); (vii) repeating steps (v) and (vi) until a number of correlation sums at least equal to the known minimum length are obtained and stored; and (viii) examining the stored obtained correlation sums to select the sum with the greatest magnitude, this selected sum indicative of the presence of the sequence and thereby indicating the slot timing.