Multiple Access Systems with QPSK Modulation

Ha H. NGUYEN  Huy G. VU  David E. DODDS  

IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences   Vol.E87-A   No.7   pp.1833-1835
Publication Date: 2004/07/01
Online ISSN: 
Print ISSN: 0916-8508
Type of Manuscript: LETTER
Category: Spread Spectrum Technologies and Applications
CDMA,  interference cancellation,  QPSK modulation,  

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This letter considers multiple access systems without bandwidth expansion. To improve the spectral efficiency, each user employs a QPSK modulation. The orientation of QPSK constellations is designed to maximize the minimum distance of the superimposed symbol constellation. The upper and lower bounds for the error performance of the proposed design demonstrate its advantage.