Patent ID: 7352830
Filing Date: 2008-04-01
Classification: H04B

Abstract:
1. An apparatus for detecting a preamble in a message, wherein said preamble comprises symbols having a first transmission rate, f s , each of said symbols is overlaid with a known binary sequence having a second transmission rate, f c , and having low autocorrelation for lags other than zero, said apparatus comprises: a first correlator arranged to correlate a received signal with said known binary sequence producing a sequence of first correlation values, wherein each of said correlation values indicates that correlation between said received signal and said known binary sequence, a second correlator provided to receive said first correlation values from said first correlator and correlate said first correlation values with said symbols producing a corresponding sequence of second correlator values indicating the correlation between said first correlation values and said symbols, a peak selector provided to receive said first and second correlation values and to select a correlation value form a received set of first correlation values having the largest corresponding second correlation value producing a sequence of selected correlation values and a sequence of position values indicating the position of said selected correlation value in said set of first correlation values, and a third correlator provided to receive said selected correlation values and said position values and correlate said received selected correlation values with symbols in said preamble by weighting each selected correlation value depending on the relation between the position of said selected correlation value and the position of other selected correlation values, and combining said weighted selected correlation values to produce a result indicative of the detection of said preamble.