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A class of errorless codes for overloaded synchronous wireless and optical CDMA systems

Pad, P ; Sharif University of Technology | 2009

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  1. Type of Document: Article
  2. DOI: 10.1109/TIT.2009.2018181
  3. Publisher: 2009
  4. Abstract:
  5. In this paper, we introduce a new class of codes for overloaded synchronous wireless and optical code-division multiple-access (CDMA) systems which increases the number of users for fixed number of chips without introducing any errors. Equivalently, the chip rate can be reduced for a given number of users, which implies bandwidth reduction for downlink wireless systems. An upper bound for the maximum number of users for a given number of chips is derived. Also, lower and upper bounds for the sum channel capacity of a binary overloaded CDMA are derived that can predict the existence of such overloaded codes. We also propose a simplified maximum likelihood method for decoding these types of overloaded codes. Although a high percentage of the overloading factor1 degrades the system performance in noisy channels, simulation results show that this degradation is not significant. More importantly, for moderate values of Eb/N0 (in the range of 6-10 dB) or higher, the proposed codes perform much better than the binary Welch bound equality sequences. © 2009 IEEE
  6. Keywords:
  7. Binary code-division multiple-access (CDMA) ; Overloaded code-division multiple-access (CDMA) ; Welch bound equality ; Bandwidth reductions ; Chip rate ; Downlink wireless systems ; Fixed numbers ; Lower and upper bounds ; Maximum likelihood decoder ; Maximum likelihood methods ; Moderate value ; New class ; Noisy channel ; Optical CDMA ; Optical code division multiple access ; Simulation result ; Upper Bound ; Welch bound equality ; Welch bound equality sequences ; Binary codes ; Binary sequences ; Block codes ; Channel capacity ; Code division multiple access ; Decoding ; Maximum likelihood
  8. Source: IEEE Transactions on Information Theory ; Volume 55, Issue 6 , 2009 , Pages 2705-2715 ; 00189448 (ISSN)
  9. URL: https://ieeexplore.ieee.org/abstract/document/4957640