Block Demodulation for Trellis Coded Modulation

Yutaka MIYAKE  Masafumi HAGIWARA  Masao NAKAGAWA  

IEICE TRANSACTIONS (1976-1990)   Vol.E73   No.10   pp.1674-1680
Publication Date: 1990/10/25
Online ISSN: 
Print ISSN: 0000-0000
Type of Manuscript: Special Section PAPER (Special Issue on Communication Theory and Its Applications)
Category: Modulation and Demodulation

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Trellis-Coded Modulation (TCM) schemes become popular in digital transmission systems to improve error performance. However, demodulation of Trellis-Coded signal is rather difficult. Because TCM schemes need many signal points compared with the uncoded schemes. This leads to a comparatively high probability of cycle slips. In addition, large loop delay caused by decoding can not be avoided when decision feed back type demodulators are used. This paper proposes a novel demodulation method for TCM signal using block demodulation. The block demodulation scheme is a kind of off-line demodulation, which has many advantages. The Viterbi decoder in the proposed block demodulator is used not only for Viterbi decoding but also for carrier estimation. Such a combined processing is done twice for high performance. In addition, a block demodulation scheme is not affected by processing delay. Therefore in the proposed system, carrier estimation becomes accurate, and Viterbi decoding also becomes correct. As a result, it can get coding gains which cannot be obtained by conventional block demodulation methods. And the proposed system can demodulate not only PSK signal but also QAM signal. The performance of the proposed demodulator is confirmed by computer simulation.