Construction of trellis codes with a good distance profile

• Published in: IEEE transactions on communications Vol. 42; no. 234; pp. 290 - 298
• Main Authors: Malladi, S.S., Fu-Quan Wang, Costello, D.J., Ferreira, H.C.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: New York, NY IEEE 01.02.1994; Institute of Electrical and Electronics Engineers
• Subjects: Applied sciences; Coding, codes; Computational complexity; Convolutional codes; Decoding; Distributed computing; Exact sciences and technology; Feedback; Information, signal and communications theory; Memory management; Signal and communications theory; Telecommunications and information theory; Phase shift keying; Coding; Amplitude modulation; Trellis code; Quadrature modulation; Algorithm; Sequential decoding
• ISSN: 0090-6778; 1558-0857
• DOI: 10.1109/TCOMM.1994.577033

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/.< >