A High Capacity CI/MC-CDMA System for Reduction in PAPR

This paper proposes a high capacity carrier interferometry/multicarrier code division multiple access (CI/MC-CDMA)system to reduce PAPR (peak-to-average power)through the simultaneous support of high and low data rate transmission. The implementation is done by allocating all sub-carriers to the users who transmit high data rate and alternate odd and even subcarriers are assigned to the other set of users who wish to transmit low data rate. The usage of alternate sub-carriers suggests to split CI codes in odd and even parts leading to an increase in capacity. Reduction in PAPR values is achieved through the phase shift of even CI code using odd sub-carriers by an amount of pi/2 and odd CI code using even sub-carriers by -pi/2, all measured with respect to the orthogonal codes supporting high data rate transmission. Finally, CI code optimization is done for further reduction in PAPR values. The proposed method also improves BER performance compared to the conventiona lCI/MC-CDMA system. Simulation results duly support this claim.