Frame synchronization in multicarrier transmission systems
First Claim
1. A method of maintaining frame synchronization in a multicarrier modulation transmission system in which a synchronizing frame containing a synchronizing pattern is periodically transmitted, comprising the steps of:
- storing complex amplitudes of the synchronizing frame;
correlating the complex amplitudes of the synchronizing frame with stored information representing the synchronizing pattern, thereby to produce a correlation result; and
determining whether the correlation result falls below a threshold value, indicating a loss of frame synchronization, and in this event;
performing a plurality of correlations between the stored information and the stored complex amplitudes multiplied in each case by a respective complex value representing a respective complex derotation of the stored complex amplitudes, each complex derotation corresponding to a respective time shift of the synchronizing frame, thereby to produce a plurality of correlation results each corresponding to a respective time shift;
determining from the plurality of correlation results a time shift for restoring frame synchronization; and
adjusting a frame boundary in accordance with the determined time shift to restore frame synchronization.
6 Assignments
0 Petitions
Accused Products
Abstract
A discrete multitone modulation transmission system is described in which frame synchronization is monitored at the receiver by correlating frequency domain complex amplitudes of a synchronizing frame with a stored synchronizing pattern. If the correlation result falls below a threshold, indicating a loss of frame synchronization, a plurality of correlations are performed, in each case using the stored complex amplitudes of the synchronizing frame multiplied by a respective complex value representing a respective complex derotation corresponding to a respective possible time shift of the synchronizing frame. The best correlation result, if it exceeds another threshold, indicates a time shift for restoring frame synchronization, this being possible before the next synchronizing frame is received.
-
Citations
21 Claims
-
1. A method of maintaining frame synchronization in a multicarrier modulation transmission system in which a synchronizing frame containing a synchronizing pattern is periodically transmitted, comprising the steps of:
-
storing complex amplitudes of the synchronizing frame; correlating the complex amplitudes of the synchronizing frame with stored information representing the synchronizing pattern, thereby to produce a correlation result; and determining whether the correlation result falls below a threshold value, indicating a loss of frame synchronization, and in this event; performing a plurality of correlations between the stored information and the stored complex amplitudes multiplied in each case by a respective complex value representing a respective complex derotation of the stored complex amplitudes, each complex derotation corresponding to a respective time shift of the synchronizing frame, thereby to produce a plurality of correlation results each corresponding to a respective time shift; determining from the plurality of correlation results a time shift for restoring frame synchronization; and adjusting a frame boundary in accordance with the determined time shift to restore frame synchronization. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
-
-
16. 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. - View Dependent Claims (17, 18)
-
-
19. 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. - View Dependent Claims (20, 21)
-
Specification