Pilotless Frame Synchronization Using LDPC Code Constraints

A method of pilotless frame synchronization has been devised for low-density parity-check (LDPC) codes. Heretofore, it has been conventional practice to add pilot symbols, which serve as frame-synchronization markers, to LDPC codes as well as to some other codes. The reception of a signal modulated by a code accompanied by pilot symbols includes a process, separate from the decoding process, in which a correlation rule is used to estimate an offset between (1) the actual received code frame time and (2) a previous estimate of the code frame time. The estimate of the offset then serves as feedback for correcting the previous estimate of the frame time. On the other hand, in pilotless frame synchronization, there are no pilot symbols; instead, the offset is estimated by exploiting selected aspects of the structure of the code. The advantage of pilotless frame synchronization is that the bandwidth of the signal is reduced by an amount associated with elimination of the pilot symbols. The disadvantage is an increase in the amount of receiver data processing needed for frame synchronization.