Title :
Construction of trellis codes with a good distance profile
Author :
Malladi, S.S. ; Fu-Quan Wang ; Costello, D.J., Jr. ; Ferreira, H.C.
Author_Institution :
Dept. of Electr. Eng., Notre Dame Univ., IN, USA
Abstract :
Systematic feedforward trellis codes for 8-PSK and 16-QAM modulation are constructed using a nested step by step algorithm which guarantees a good distance profile. This makes the codes suitable for use with sequential decoding, where a rapidly growing distance profile is needed to reduce the average number of computations. In addition to having a good distance profile, the new codes achieve asymptotic coding gains of up to 6.53 dB. A procedure based upon the Fano (1963) algorithm (FA) is used to calculate the free distance of the new codes. This procedure is very effective for finding the free distances of long trellis codes because of the computational and storage efficiency of the FA. From a comparison of the new systematic feedforward codes with Ungerboeck´s (1982, 1987) systematic feedback codes, the authors conjecture that a systematic feedforward code of constraint length 2/spl nu/ can achieve the same free distance as a systematic feedback code of constraint length /spl nu/.<>
Keywords :
amplitude modulation; decoding; phase shift keying; trellis codes; 16-QAM; 8-PSK; Fano algorithm; asymptotic coding gain; code constraint length; computational efficiency; distance profile; modulation; nested step by step algorithm; sequential decoding; storage efficiency; systematic feedforward codes; systematic feedforward trellis codes; trellis coded modulation; Computational complexity; Convolutional codes; Decoding; Distributed computing; Feedback; Memory management;
Journal_Title :
Communications, IEEE Transactions on
DOI :
10.1109/TCOMM.1994.577033
