ANALYSIS OF ADAPTIVE MULTISTAGE INTERFERENCE CANCELLATION FOR CDMA USING AN IMPROVED GAUSSIAN APPROXIMATION

We consider a simple model for adaptive multistage interference cancel lation within a code-division multiple-access (CDMA) system, and seek to develop an accurate analytical expression for the performance of th is system, Previous work on interference cancellation has relied heavi ly on simulation techniques or a simple Gaussian approximation (GA), T he standard GA can lead to bit-error rate (BER) results which are opti mistic for the conventional receiver, and this also occurs when the ap proximation is applied to the interference cancellation problem, Addit ionally, this approximation does not allow the second order effects of the multiple access interference (MAI) to be included in the performa nce estimates, Recently, several improvements on the standard GA have been suggested which result in accurate performance results for a stan dard CDMA receiver, This paper presents an analytical expression for t he probability of bit error for an adaptive multistage interference ca nceller, using an improved Gaussian approximation (IGA) for MAI, The B ER at any stage of interference cancellation can be recursively comput ed from the signal-to-noise ratio (SNR), the statistics of the random powers of users, and the processing gain of the CDMA system, The perfo rmance of the resulting BER expression is compared with simulation res ults, Since the second order effects of MAI can be included, the analy tical framework presented here can also be used to evaluate the perfor mance of multistage interference cancellation in arbitrary fading envi ronments, and we present results for the performance of interference c ancellation in lognormal fading environments.