Subcarrier PIC Scheme for High Capacity CI/MC-CDMA System with Variable Data Rates

Abstract

This paper proposes a high capacity carrier interferometry/multicarrier code division multiple access (CI/MCCDMA)system through the simultaneous support of high and low data rate transmission. High data rate users transmit data through all sub-carriers while alternate odd and even subcarriers are shared by the low data rate users.The usage of alternate sub-carriers suggests to split CI codes in odd and even parts leading to an increase incapacity. The cross-correlations among the code patterns are reduced through the phase shift of even (odd) CI code using odd (even) sub-carriers by an amount of pi/2 and odd (even) CI code using odd (even) sub-carriers by -pi/2,all measured with respect to orthogonal codes assigned to support high data rate transmission. Performance in term of BER (bit error rate) is then analyzed by carrying out simulation on frequency selective Rayleigh fading channel.The MAI (multiple access interference) effect is subtracted at the subcarrier projection domain leading to the reduction in high computation cost inherent in parallel interference cancellation. Performance improvement for different combinations of low and high data rate users are shown compared to the conventional CI/MC-CDMA system as well as block PIC scheme.