Header synchronization detector

Abstract

A pattern detector adapted for wireless communication systems includes an error calculator, a comb filter, an averager, and a threshold detector. The pattern to be detected is a sequence of pilot signal patterns whose error calculation is relatively invariant with respect to frequency offset introduced by Doppler and the local oscillator. The pattern detector processes received input samples y.sub.k to determine an error signal from the input samples y.sub.k and estimated input samples y.sub.k. The estimated input samples y.sub.k are determined using an estimated channel impulse response. When a vector of the received input samples is 'aligned' with the expected header sync input samples, the level of the error signal is about equal to the level of the noise. The pattern detector determines the average level of the error signals for the last K error signals of each sample position E.sub.Kn within a pilot pattern, where K corresponds to the number of pilot patterns in a header sync pattern and n corresponds to the sample position. The pattern detector also determines the average level of the error signals E.sub.L corresponding to the last L received input samples, where L corresponds to the number of samples in a header sync sequence. When E.sub.Kn for a sample position is lower than a preselected threshold percentage of E.sub.L, the header sync pattern is deemed detected. Finally, the end of the header sync pattern is determined by the location of the minimum E.sub.Kn. This minimum is found by calculating, once the header is deemed detected, values for E.sub.Kn that are a certain number of samples past the last minimum.