A New Branch Metric Generation Method for Soft-Decision Viterbi Decoding in Coded OFDM-SDM Systems Employing MLD over Frequency Selective MIMO Channels

Satoru HORI  Masato MIZOGUCHI  Tetsu SAKATA  Masahiro MORIKURA  

IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences   Vol.E85-A   No.7   pp.1675-1684
Publication Date: 2002/07/01
Online ISSN: 
Print ISSN: 0916-8508
Type of Manuscript: Special Section PAPER (Special Section on Multi-dimensional Mobile Information Networks)
wireless LAN,  OFDM-SDM,  MLD,  Viterbi decode,  branch metric,  

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MIMO communication systems have been studied as a way to increase system capacity and to improve spectrum efficiency. This paper proposes a novel branch metric generation method for soft-decision Viterbi decoding in coded OFDM systems employing SDM (OFDM-SDM) systems, one form of MIMO communication, that employ the maximum likelihood decision (MLD) algorithm. In coded OFDM systems, the branch metric for forward error correction (FEC) is normally calculated based on received sub-carrier power level and the constellation point likelihood. This conventional approach fails in OFDM-SDM systems. In the proposed method, branch metric is derived based on the likelihood calculated by MLD algorithm, which improves FEC performance effectively. Then, availability of coded OFDM-SDM to realize wireless LANs with data rate above 100 Mbit/s in a bandwidth of 20 MHz is evaluated in office environments using required CNR calculated by computer simulation. The evaluation indicates that OFDM-SDM has the possibility of realizing 100 Mbit/s in office environments.