Pre-equalization by Virtual-user Introduction on Downlink MC-CDMA Systems
Shu-Hong Lee, Ho‐Lung Hung · 2007
The loss of orthogonality of spreading codes due to the frequency selective fading on downlink MC-CDMA systems causes multiple access interference (MAI), which considerably degrades system performance. A great deal of effort has been made on tackling that problem at the receiver of mobile station. This paper proposes a pre-equalization method based on virtual user introduction to mitigate MAT for all active users at the transmitter of base station. A closed-form pre-equalizer is presented based on known transmitted data, spreading codes, and the channel information derived from all active users. In addition, optimization problem on the pre-equalizer is also discussed. Simulation results show that the proposed method offers a better performance in terms of bit error rate (BER) than that of several typical methods (such as ORC, MRC, EQC and MMSEC) adopted at the receiver of mobile stations.