Performance of multicode DS/CDMA with noncoherent M-ary orthogonal modulation in multipath fading channels

This paper presents the performance analysis and simulation of a multicode DS/CDMA system with noncoherent M-ary modulation, operating over a Rayleigh or Nakagami fading environment. This type of transceiver is specified for the reverse link of the IS-95B and cdma2000 (Radio configurations 1 and 2) systems, and is intended to serve high-rate applications such as data transfer and video communications. After a statistical characterization of the interference terms, we make use of the Gaussian approximation (GA) in order to obtain the bit error rate (BER). However, unlike other analyses relying on the GA, in our derivation we take into account the fact that all the codes transmitted by a mobile user fade in unison. As demonstrated via computer simulations, this fact is crucial to obtain a reliable estimate of the BER, especially when equal-gain combining (EGC) is used at the receiver.