Uniquely Decodable Code for Two-User Multiple-Access Channel Using Complex-Valued Signal

Yuan LI  Hidekazu MURATA  Susumu YOSHIDA  

IEICE TRANSACTIONS on Communications   Vol.E84-B   No.3   pp.581-588
Publication Date: 2001/03/01
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: PAPER
Category: Fundamental Theories
multiple-access,  uniquely decodable code,  cochannel interference (CCI),  trellis-coded modulation,  

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This paper discusses a communication system with a multiple-access channel where two users simultaneously send complex-valued signals in the same frequency-band. In this channel, ambiguity in decoding occurs when receiver trying to estimate each users' signal. In order to solve the ambiguity problem, a family of uniquely decodable code is derived in this paper. The uniquely decodable code is designed by using trellis-coded modulation (TCM) pair where the trellis structure of one TCM is a transformation of the other in the pair. It is theoretically proved that, with the proposed coding scheme, the composite received signal can be uniquely decomposed into the two constituent signals for any power ratio and any phase difference between the received two users' signals. Improvement of BER performance over non-uniquely decodable code is illustrated by computer simulation.