Performance of Multiuser Detection for Optical CDMA—Part I: Error Probabilities

Characterization of optimum multiuser performance in intensity-modulation direct-detection optical CDMA channels is addressed. Analysis is based on some simple bounds on optimum performance provided by receivers with side-information or by a linear “decorrelating” receiver. Numerical comparisons of the performance bounds are obtained via application of saddlepoint approximations to the multiuser photocount statistics. General analytical relations comparing these approximations to similar asymptotic approximations based on the Chernoff-bound are also derived. The numerical results illustrate the fundamental importance of two of the performance bounds, which are shown to be asymptotically tight in Part II of this paper. In addition, the numerical error probability results verify the relevance of the asymptotically-based performance analysis for optical CDMA in Part II.