Performance analysis of DS-CDMA systems using improved Gaussian approximation method

We present an accurate bit error rate (BER) expression for direct sequence code division multiple access (DS-CDMA) communication systems over Nakagami multipath fading channels. This problem has been considered by Trabeisi and Yongacoglu (1995). However, the receiver of Trabeisi et al. only extracted the first path and regarded the other multipaths as interference. Our BER analysis in this paper use a RAKE receiver to exploit all the multipaths in a maximal ratio combiner. We adopt an improved Gaussian approximation (IGA) method proposed by Holtzman (1992), which takes into account the second moment effect of the multiple-access interference (MAI) variance, to derive the error performance expression. We show by Monte Carlo (MC) simulation that the derived formula gives a more accurate prediction of the error performance as compared with that obtained by using the standard Gaussian approximation (SGA) method.