Frequency-Domain Interchip Interference Cancelation for DS-CDMA Downlink Transmission

The use of frequency-domain equalization (FDE) based on minimum-mean-square-error criterion can significantly improve the bit-error-rate (BER) performance of orthogonal multicode direct-sequence code-division multiple access downlink signal transmission in a frequency-selective fading channel. However, the presence of residual interchip interference (ICI) after FDE produces the orthogonality distortion among the spreading codes, and the BER performance degrades as the number of multiplex order increases. In this paper, we propose a frequency-domain ICI cancellation scheme, in which the residual ICI replica in the frequency domain is generated and subtracted from each frequency component of the received signal after FDE. Three types of ICI cancelation scheme are presented, and the effectiveness of the proposed ICI cancelation scheme is confirmed by computer simulation