Direct Sequence Code Division Multiple Access With Optical Multicarriers and Parallel FEC Codes

Raziq Pervez YAQUB  Masao NAKAGAWA  

Publication
IEICE TRANSACTIONS on Communications   Vol.E81-B   No.4   pp.785-797
Publication Date: 1998/04/25
Online ISSN: 
DOI: 
Print ISSN: 0916-8516
Type of Manuscript: PAPER
Category: Mobile Communication
Keyword: 
CDMA,  optical communication,  multicarrier transmission,  parallel FEC,  

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Summary: 
We propose Direct Sequence CDMA with Optical Multicarriers and Parallel Forward Error Correcting (PFEC) coding technique. Proposed DS-CDMA with OPTICAL MULTICARRIERS, is new in lightwave systems and its alliance with PARALLEL FEC codes, makes it further unique. Optical multicarriers approach is effective to increase throughput by combating dispersion and ISI (Intersymbol Interference), whereas FEC is effective to increase reliability by diluting interactions among optical multicarriers. Till now, both the techniques in lightwave systems have been discouraged. The former because of the wandering effect of optical multicarriers owing to unstability of laser diodes and later because it involves insertion of parity bits that changes data rate and results in insertion distortion that is not desirable in optical systems. To avoid change due to spreading code we also propose to take spreading code equal to serial to parallel converted streams. It bounds initial data (before S/P conversion) to data per carrier (after S/P conversion and spreading) on one hand and relaxes the requirement of high speed electronics on the other. The alliance of optical multicarriers with suitably applied FEC that we refer as Parallel FEC (PFEC) is effective as the beneficial aspects of each mitigate the shortcomings of the other and make the system practicable. Theoretical treatment confirms that the proposed approach is fundamentally sound and holds the potential for promising network performance.