Performance of the Decorrelating Detector in Correlated Rayleigh Fading

Abstract — Consider a code-division multipleaccess system in a correlated Rayleigh fading environment in which the fading gains are independent among the users but correlated among the receive diversity branches, and which uses the decorrelating multiuser detector. The branches are combined using maximal-ratio combining, which requires channel estimation. The channel is estimated by means of pilot symbols. From the characteristic function of the detector decision variable, a closed-form expression for the bit error probability (BEP) of this system is obtained. For the case of exponentially correlated branches and equicorrelated signature waveforms, numerical results show that (1) the signature cross-correlation has a stronger effect on the performance than the branch correlation, (2) the BEP steadily decreases with increase in the number of branches, and increases with increase in the number of users, rapidly tending to reach saturation as the number of users becomes large.