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Matched Design Method for Concatenated TrellisCoded Modulation
Tadashi WADAYAMA Koichiro WAKASUGI Masao KASAHARA
Publication
IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences
Vol.E79A
No.11
pp.19111917 Publication Date: 1996/11/25 Online ISSN:
DOI: Print ISSN: 09168508 Type of Manuscript: PAPER Category: Information Theory and Coding Theory Keyword: trelliscoded modulation, concatenated code, weight distribution,
Full Text: PDF(573.7KB)>>
Summary:
A new design method, which is referred to as the matched design method, for concatenated trelliscoded modulation (TCM) is presented. Most of the conventional concatenated TCM employs TCM designed to maximize the minimum squared Euclidean free distance, d^{2}_{free}. With the matched design method, we maximize d^{2}_{1}(t) instead of d^{2}_{free}, where d^{2}_{1}(t) is the effective minimum squared Euclidean distance (MSED) when the outer code has a terror correcting capability. The effective MSED is derived from the Euclidean/Hamming (E/H) joint weight distribution of terminated TCM. We here assume the concatenated TCM whose transmitted symbol corresponds to a symbol of outer code. The new classes of 2dimensional (2D) and 4dimensional (4D) codes are found by a computer search. Under the performance measures of the effective MSED or the effective multiplicity, these codes are superior to the conventional codes such as the Ungerboeck's 2Dcodes when those are used as an inner code. We disclose an interesting fact that the new class of codes using rate1/2 encoder is superior to the class of codes using rate2/3 encoder. This fact implies that the codes using rate1/2 encoder have two advantages: 1) better overall decoding performance and 2) less decoding complexity.

