An Efficient Downlink Transmission Scheme for 5G Wireless Networks

Recent studies have shown that frequency quadrature amplitude modulation (FQAM), a combination of frequency shift keying and quadrature amplitude modulation, can be an attractive modulation scheme to enhance the performance of the cell-edge users in cellular systems. In this paper, we propose an efficient downlink transmission scheme for future 5G systems based on FQAM that further improves the system performance compared to the classical FQAM-based scheme. In the proposed scheme, a cell-edge user will be served with FQAM scheme and the inactive subcarriers in each FQAM symbol are used to serve a cell-centre user with lower transmission power. We show that, with proper selection of the power levels on the active and inactive subcarriers, the non-Gaussian distribution of the interference at the cell-edge can be maintained, which is essential to achieve good performance with FQAM scheme. Furthermore, while maintaining the non-Gaussian distribution, the use of unused carriers by the second user results in a significant throughput increase. Our results show that the proposed scheme maintain the performance of the cell-edge user and provide an increase of 130%-140% in the overall throughput compared with conventional transmission schemes.