Coherent DS-SS receiver using exponentially weighted despreading function with imperfect power control in multipath Rayleigh fading environment

Abstract

In this paper, a closed-form solution for the average bit error rate (BER) performance of a coherent DS-CDMA system with imperfect power control is derived for a multipath Rayleigh fading channel. The RAKE receiver under consideration employs exponentially weighted despreading function with an adjustable parameter γ optimized for multiple access interference rejection in multipath environment. The results indicate that the number of active users supported at a given BER for the case of γ tuned to maximize the average signal to interference plus noise ratio SINR̄ is much larger than commonly used rectangular despreading function (γ = 0). It is shown that imperfect power control affects the irreducible BER for the case of γ = 0. On the other hand, the effect of imperfect power control on BER performance for γ tuned to maximize SINR̄ is equivalent to a reduction in the average signal to white noise ratio γ̄b and hence system performance can be compensated by increasing the transmitter power.