A Study on Multi-User Interference Cancellers for Synchronous Optical CDMA Systems — Decision Distance and Bit Error Rate —


IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences   Vol.E100-A   No.10   pp.2135-2145
Publication Date: 2017/10/01
Online ISSN: 1745-1337
DOI: 10.1587/transfun.E100.A.2135
Type of Manuscript: PAPER
Category: Spread Spectrum Technologies and Applications
optical CDMA,  modified prime sequence code (MPSC),  multi-user interference (MUI),  interference canceller,  decision distance,  

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Several kinds of techniques for excellent multi-user interference (MUI) cancellation have been proposed for direct-detection synchronous optical code division multiple access (OCDMA) systems. All these techniques utilize modified prime sequence codes (MPSCs) as signature codes and can remove MUI errors efficiently. In this paper, the features of three typical MUI cancellers are studied and compared in detail. The authors defined the parameter “decision distance” to show the feature of MUI cancellers. The bit error rate performance of each canceller is investigated by computer simulation and compared with that of the basic on-off keying (OOK) scheme without cancellation. Then, we investigate the relationship between the decision distance and the bit error rate performance. It is shown that every canceller has a better bit error rate performance than the basic OOK scheme. Especially, the equal weight orthogonal (EWO) scheme, whose decision distance is the largest, has the best error resistance property of the three MUI cancellers. The results show that the decision distance is a useful index to evaluate the error resistance property of MUI cancellation schemes.