Frame synchronization in multicarrier transmission systems

A multicarrier modulation transmission system receiver comprising:

• a demodulation unit for transforming time domain values into complex amplitudes in the frequency domain;
• a buffer for supplying received time domain values to the demodulation unit in accordance with a frame boundary;
• a correlator for correlating complex amplitudes of a synchronizing frame of the system with a synchronizing pattern stored at the receiver to produce a correlation result;
• and
• a control unit responsive to the correlation result being below a threshold value to adjust the frame boundary by a time shift determined by performing a plurality of correlations between the stored synchronizing pattern and the complex amplitudes multiplied in each case by a respective complex value representing a respective complex derotation of the complex amplitudes corresponding to a respective time shift of the synchronizing frame, and then selecting the best correlation result.

A method of monitoring frame synchronization in a multicarrier modulation transmission system in which a synchronizing frame containing at least a synchronizing pattern is transmitted, said method comprising:

• (a) receiving values of the synchronizing frame, the values of the synchronizing frame being complex amplitudes;
• (b) comparing the values of the synchronizing frame with corresponding stored values of the synchronizing pattern to produce a comparison result;
• (c) comparing the comparison result with at least one threshold value to provide an indication of existence or loss of frame synchronization;
• (d) determining an adjustment amount to restore frame synchronization when said comparing (c) indicates that the frame synchronization has been lost, said determining (d) including the operations of (d1) derotating of the complex amplitudes of the synchronizing frame in accordance with respective time shifts to produce a plurality of derotated complex amplitudes, and (d2) correlating the stored values of the synchronizing pattern with respective ones of the derotated complex amplitudes of the synchronizing frame to produce a plurality of correlation results;
• and
• (e) adjusting a frame boundary in accordance with the adjustment mount to restore frame synchronization.