User grouping and adaptive modulation for downlink MC-CDMA systems

In this paper, we propose the user grouping and adaptive modulation algorithms for downlink Multi-Carrier Code Division Multiple Access (MC-CDMA) systems. Under a frequency-selective fading channel, we adaptively assign users into groups by their channel state information (CSI) such that spectrum efficiency is improved and BER is reduced. After grouping, we assign bit loading and allocate transmission power for each user according to its effective channel response. Our scheme aims at maximizing total system data rate under both the total power and the BER bound constraints. Simulation results show that our scheme outperforms at bit error rate and data rate.