A Closed-form BER Expression for Differentially Modulated DS-CDMA Signals with Frequency-domain Differential Detection and Equalization

摘要

Recently, we have proposed frequency-domain differential detection and equalization (FDDDE) for the reception of differentially encoded DS-CDMA signals in a time- and frequency-selective fading channel. It was shown by computer simulation that FDDDE using an IIR filter with decision feedback can provide better BER performance than coherent frequency-domain equalization (FDE) with pilot-assisted channel estimation in a fast fading channel. In this paper, a closed-form BER expression is derived for the FDDDE reception of DQPSK-modulated DS-CDMA signals as a function of the normalized root mean square (rms) delay spread and the normalized Doppler frequency. Using the derived BER expression, an optimum IIR filter coefficient is found under different channel conditions and the theoretical BER performance is confirmed by the computer simulation.