Bit error probability of linear decorrelating detector for random signature sequences

The BER performance of linear decorrelating detectors (LDD) is analyzed for random signature sequences for random CDMA systems. The performance of LDD could be expressed in terms of the so-called noise enhancement factors, the diagonal components of inverse cross-correlation matrix for one symbol period of signature sequences. However, when each component of the cross-correlation matrix varies from symbol to symbol, it should be regarded as a random variable. And, in this case, the PDF of the noise enhancement factors should be determined first to evaluate the performance of LDD. In this paper, the approximate PDF of the noise enhancement factor for random signature sequences and the corresponding BER expression of LDD are derived for both AWGN and fading channels. The approximate BER is verified via Monte-Carlo simulations