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Abstract

The present invention describes a method of estimating the symbol time offset in a received signal of a data modem using only one received synchronization symbol. This estimate of the offset is used for a rapid synchronization during the starting phase or for resynchronization during a micro-interruption. The method estimates the offset by comparing the frequency domain constellation obtained by transforming the received synchronization symbol using the current sample pointer setting with the frequency domain constellations stored as templates. (A constellation point for a channel is phase and magnitude values in frequency domain for the channel). It chooses the template which is closest to the received constellation and declares the offset corresponding to the chosen template as the estimated offset for the received symbol. The templates are obtained by the following process. First, a time domain signal is obtained by transforming a fixed (transmitted) synchronization symbol comprising of several channels each with a constellation point specified for the channel. Next, the time domain signal is shifted by k samples and transformed into a frequency domain constellation. The frequency domain constellation serves as the template for offset value k. The shifting of the time domain signal by other values of k and obtaining the corresponding frequency domain constellations result in the set of required templates.

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