Performance analysis of linear multiuser detectors for randomlyspread CDMA using Gaussian approximation
Seokhyun Yoon; Bar-Ness, Y.
Selected Areas in Communications, IEEE Journal on
Volume 20, Issue 2, Feb 2002 Page(s):409 - 418
Digital Object Identifier 10.1109/49.983364
Summary:The performance of a linear decorrelating detector (LDD) and a
minimum mean square error (MMSE) detector is analyzed for random
spreading waveforms. The performance of the LDD and MMSE detectors is
expressed in terms of the so-called near-far resistance, defined by a
reciprocal of a diagonal component of inverse matrix. For random code
division multiple access, which employs random spreading waveforms, the
near-far resistance can be regarded as a random variable. Many papers
have dealt with the analysis of multiuser detectors for random spreading
sequences. In most cases, however, these analyses derived only the
expectations or bounds for the near-far resistance. In this paper, we
directly derive the approximate probability density function (PDF) of
the near-far resistance and corresponding bit error rate expression for
random spreading sequences. It is based on Gaussian approximation of the
cross correlation between any two randomly generated spreading codes.
The resulting PDF turned out to be a reversed-and-scaled version of
chi-square distribution. The approximate expressions, both the PDF and
the corresponding bit error rate expression, were verified via Monte
Carlo simulations. The results showed that the approximation is quite
close to the simulation results when the number of users is less than
half the processing gain
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