Inter-chip interference cancellation for DS-CDMA with frequency-domain equalization

The bit error rate (BER) performance of DS-CDMA in a frequency-selective fading channel can be significantly improved by the use of frequency-domain equalization (FDE). However, for a small spreading factor (SF), the residual inter-chip-interference (ICI) degrades the BER performance. We propose three types of ICI cancellation and the BER performance improvement is evaluated by computer simulation. The ICI replica is generated and subtracted from the FDE-equalized chip sequence. The reduction in E_b/N₀ for achieving a BER=10^-4 is as much as about 4.2 dB when SF=4. Joint use of antenna diversity combining and ICI cancellation is also presented.