Circular viterbi decoder

Details Circular viterbi decoder Circular viterbi decoder

1993-02-11

1994-10-11

Smith, Jerry

Excavating

G06F 1110

Patent

active

053553764

ABSTRACT:
Branchwood signals are generated by a tailbiting convolutional coder. The receiver stores received branchword signals in memory such that the branchword signals are accessible in a logically circular sequence. The receiver then performs Viterbi updates on the logically circular sequence of branchwords, the sequence comprising more than N branchwords. The receiver stops performing Viterbi updates in response to an indication that update decisions have become repetitive. A set of generated decision vectors resulting from the Viterbi updates is then modified in response to the indication. A decoded signal is generated by performing a Viterbi traceback procedure using the modified set of decision vectors. The indication that Viterbi update decisions have become repetitive may be provided by a predetermined fixed number of Viterbi updates, the number reflecting an estimate of when said update decisions will likely become repetitive. The indication may also be provided by a comparison of decision vectors generated by Viterbi updates on the same stored branchword to determine whether the vectors are substantially equal. Or, the indication may be provided by a comparison of a pair of path metric vectors generated by Viterbi updates on the same stored branchword to determine whether differences between metric signals of one or more respective trellis state pairs of the path metric vectors are substantially equal. Modification of the set of generated decision vectors may include replacing a one or more decision vectors of the set with one or more later-determined decision vectors of the set.

REFERENCES:
patent: 5182753 (1993-01-01), Dahlin
patent: 5208816 (1993-05-01), Seshardi et al.
patent: 5287374 (1994-02-01), Parr
H. H. Ma and J. K. Wolf, "On Tail Biting Convolution Codes", IEEE Transactions on Communications, vol. 34, 104-111, Feb. 1986.
Q. Wang and V. K. Bhargava, "An Efficient Maximum Likelikhood Decoding Algorithm for Generalized Tailbiting Convolutional Codes Including Quasicyclic Codes," IEEE Transactions on Communications, vol. 37, No. 8, 875-879, Aug. 1989.
G. Solomon and H. C. A. van Tilborg, "A Connection Between Block and Convolutional Codes," SIAM Journal on Applied Mathematics, vol. 37, No. 2, 358-369, Oct. 1979.
R. S. LeFever, "A New Class of Powerful, Viterbi Decodable, Block Codes," 1988 Tactical Communications Conference, Fort Wayne, Ind., Conf. Rec. 304-307.
K. Sh. Zigangirov and V. V. Chepyshov, "Study of Decoding Tailbiting Convolutional Codes," Proceedings, Fourth Joint Swedish-Soviet International Workshop on Information Theory, Aug. 1989, Gotland, Sweden, 52-55.
Clark and Cain, Error-Correction Coding for Digital Communications, Ch. 6 on "Convolutional Code Structure and Viterbi Decoding" pp. 227-266, 1981.

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