A Novel Spectrally Efficient Wireless CDMA Transmission Scheme: System Design and Robustness to Channel Imperfections

When compared to the traditionally considered Gaussian capacity limit, creating appropriate non-Gaussian multiuser interference in CDMA transmission with single-user decoding can increase the channel capacity limit several times. We have recently designed a coded M-ary CDMA transmission scheme that can practically achieve large part of this capacity increase and improve significantly spectral efficiency of CDMA systems. The main objective of this paper is to explore the robustness of this scheme to wireless channel imperfections. We consider two potential CDMA channel impairments, i.e., imperfect power control at the transmitter and power-limited amplifiers at the receiver. Simulation results for 16-ary CDMA network transmission show that under ideal conditions, spectral efficiency of 1.45 bits per CDMA chip (i.e., more than twice the conjectured Gaussian capacity limit) is achieved. The simulation results also show that the scheme is robust to 1 dB power control error and a power limit at the receiver amplifier