BER of DS/CDMA using symbol-aided coherent demodulation over Rician and Rayleigh fading channels

The BER of DS/CDMA systems that use symbol-aided demodulation (SAD) over Rayleigh and Rician fading channels is evaluated. Known symbols are transmitted with a certain frequency together with the data symbols and are used by the receiver to extract a phase reference for demodulation. Different schemes for filtering of the known symbols to obtain the phase reference needed for demodulation are considered and BER comparisons are made. The BER of these SAD DS/CDMA schemes is also compared with that of fully coherent and differentially coherent DS/CDMA systems operating over Rician and Rayleigh fading channels. The important role of filtering in SAD for DS/CDMA networks is studied in detail and it is shown that under some channel and system conditions (such as terrestrial mobile with low data rates) optimum (Wiener) filtering is needed while for other channel and system conditions (such as GEO satellite with higher data rates) simpler low pass filters are sufficient