Fading resistant multiuser detection over CDMA fading channels

The authors consider the limitations imposed by interfering fading on detector performance over asynchronous, memoryless, nondispersive, Rician faded CDMA (code division multiple access) channels, as well as mechanisms to alleviate these limitations. They introduce fading resistance and fading susceptance measures that are asymptotic performance characterizations capturing the ability or inability of detectors to withstand fading interference. It is found that the optimum single-user or conventional detection strategy, when employed over the CDMA Rician fading channel, is limited in performance by fading interference in a manner akin to specular or multiple-access interference. Even the multiuser detectors designed for the CDMA AWGN (additive white Gaussian noise) channel, which are known to be able to withstand specular interference, are found to be unable to combat fading interference. The detectors optimized for the Rician fading channel, the optimal faded detector, and the faded decorrelator are found, however, unlike the previous classes of detectors, to be resistant to such interference