The delayed symbol combining interference canceller for multi rate DS-CDMA

Tn mobile and personal radio, direct sequence code division multiple access (DS-CDMA) systems are atracting attention because of their inherently high capacity. Furthermore, the DS-CDMA system is a flexible system which can accommodate various user rates easily. As many user will occupy the same frequency band simultaneously, the traffic capacity of a DS-CDMA system is determined by interference power. Interference cancellation is one of the important techniques in decreasing interference power and increasing traffic capacity. In this paper, we propose the delayed symbol combining interference canceller which can suppress the interference from various users sending at different information rates. Its performance is calculated by computer simulations from the view point of bit-error-rate (BER). In the flat fading environment, it is found that E(d)/N-o degradation by the interference is suppressed to 3 dB at BER of 10(-3) with 24 users. In the frequency selective fading environment, it is found that the required Eb/No of the frequency selective fading canceller is about 11 dB better than that flat fading canceller to establish the BER of 10(-3).