Patent ID: 7522679

Claim:
A method for receiving a first series of trellis-encoded symbols transmitted with a first constellation density and a second series of trellis-encoded symbols transmitted with a second constellation density less than the first, wherein a plurality of the second series of symbols comprises a terminating pad of a predetermined length, comprising: receiving and decoding the first series of trellis-encoded symbols in a trellis decoder; determining if one of the decoded symbols corresponds to an end-of-data marker identifying when the terminating pad will be transmitted; receiving the second series of trellis-encoded symbols comprising the terminating pad; and responsive to receiving a last symbol in the terminating pad, decoding all symbols remaining in a Viterbi traceback buffer by selecting a start state based on the last symbol, and repeatedly tracing back through a reduced number of symbols in the traceback buffer using the same selected start state on each trace cycle while reducing the number of symbols by one each trace cycle.