A 256 QAM Digital Radio System with a Low Rolloff Factor of 20% for Attaining 6.75 bps/Hz

Hiroshi NAKAMURA  Eisuke FUKUDA  Noburu IIZUKA  Yoshimasa DAIDO  Sadao TAKENAKA  

IEICE TRANSACTIONS (1976-1990)   Vol.E71   No.1   pp.43-50
Publication Date: 1988/01/25
Online ISSN: 
Print ISSN: 0000-0000
Type of Manuscript: PAPER
Category: Radio Communication

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This paper describes a newly-developed 4 GHz 135 Mbps 256 QAM system with a rolloff factor of 20%, which can attain a spectrum efficiency of 6.75 bps/Hz. The key techniques are theoretically investigated to realize this system. It was predicted theoretically that the simultaneous incorporation of 7-tap transversal equalizers (TEQL) and a recursive slope equalizer (SEQL) would be required as countermeasure for multipath fading. The 256 QAM system was designed considering the results of the theoretical investigation. Excellent BER performance was obtained with the aid of forward error correction and pilot carrier injection. Since remarkable improvement in the signature was obtained by the simultaneous user of TEQL and SEQL, the 256 QAM system with a very low rolloff factor is promising.