Abstract
A detailed analysis of the multiple access interference (MAI) for synchronous downlink CDMA systems is carried out for BPSK signals with random signature sequences in Nakagami-m fading environment with known channel phase. This analysis presents a unified approach as Nakagami-m fading is a general fading distribution that includes the Rayleigh, the one-sided Gaussian, the Nakagami-q, and the Rice distributions as special cases. Consequently, new explicit closed-form expressions for the probability density function (pdf) of MAI and MAI plus noise are derived for Nakagami-m, Rayleigh, one-sided Gaussian, Nakagami-q, and Rician fading. Moreover, optimum coherent reception using maximum likelihood (ML) criterion is investigated based on the derived statistics of MAI plus noise and expressions for probability of bit error are obtained for these fading environments. Furthermore, a standard Gaussian approximation (SGA) is also developed for these fading environments to compare the performance of optimum receivers. Finally, extensive simulation work is carried out and shows that the theoretical predictions are very well substantiated.
Highlights
It is well known that multiple access interference (MAI) is a limiting factor in the performance of multiuser CDMA systems, its characterization is of paramount importance in the performance analysis of these systems
In [6], the pdf of MAI is derived for synchronous downlink CDMA systems in AWGN environment and the results are extended to MC-CDMA systems to determine the conditional pdf of MAI, inter-carrier interference (ICI) and noise given the fading information and pdf of MAI plus ICI plus noise is derived, where channel fading effect is considered deterministic
Optimum coherent reception using maximum likelihood (ML) criterion is investigated based on the derived expressions of the pdf of MAI and expressions for probability of bit error are obtained for these fading environments
Summary
It is well known that MAI is a limiting factor in the performance of multiuser CDMA systems, its characterization is of paramount importance in the performance analysis of these systems. Unlike the approaches in [4, 5], new explicit closed-form expressions for unconditional pdfs of MAI and MAI plus noise in Nakagami-m, Rayleigh, one-sided Gaussian, Nakagami-q, and Rician fading environments are derived. In this analysis, unlike [6], the random behavior of the channel fading is included, and more realistic results for the pdf of MAI plus noise are obtained. Optimum coherent reception using ML criterion is investigated based on the derived expressions of the pdf of MAI and expressions for probability of bit error are obtained for these fading environments.
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