Open Access

Analysis of Optical CDMA Signal Transmission: Capacity Limits and Simulation Results

  • Aminata A. Garba1Email author,
  • Raymond M.H. Yim2,
  • Jan Bajcsy1 and
  • Lawrence R. Chen1
EURASIP Journal on Advances in Signal Processing20052005:230735

https://doi.org/10.1155/ASP.2005.1603

Received: 5 April 2004

Published: 30 June 2005

Abstract

We present performance limits of the optical code-division multiple-access (OCDMA) networks. In particular, we evaluate the information-theoretical capacity of the OCDMA transmission when single-user detection (SUD) is used by the receiver. First, we model the OCDMA transmission as a discrete memoryless channel, evaluate its capacity when binary modulation is used in the interference-limited (noiseless) case, and extend this analysis to the case when additive white Gaussian noise (AWGN) is corrupting the received signals. Next, we analyze the benefits of using nonbinary signaling for increasing the throughput of optical CDMA transmission. It turns out that up to a fourfold increase in the network throughput can be achieved with practical numbers of modulation levels in comparison to the traditionally considered binary case. Finally, we present BER simulation results for channel coded binary and -ary OCDMA transmission systems. In particular, we apply turbo codes concatenated with Reed-Solomon codes so that up to several hundred concurrent optical CDMA users can be supported at low target bit error rates. We observe that unlike conventional OCDMA systems, turbo-empowered OCDMA can allow overloading (more active users than is the length of the spreading sequences) with good bit error rate system performance.

Keywords and phrases:

optical CDMA communicationmultiple-access channelsM-ary modulationchannel capacityturbo codes

Authors’ Affiliations

(1)
Department of Electrical and Computer Engineering, McGill University, Montreal, Canada
(2)
Division of Engineering and Applied Sciences, Harvard University, Cambridge, USA

Copyright

© Aminata A. Garba et al. 2005

This article is published under license to BioMed Central Ltd. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.