A Spectrum Efficient Multi-User Transmission Scheme for 5G Systems With Low Complexity

To maximize the system throughput for downlink multi-user transmission considering fairness among the users, superposition coding (SC) with all the users scheduled simultaneously is optimal. But it would also lead to high implementation complexity at receivers. In this paper, a simplified downlink multi-user transmission scheme is proposed via combining SC and time division multiplexing (TDM). All the users are divided into multiple user groups and only the users within each user group are scheduled simultaneously via SC. Closed-form expression for the system throughput by the proposed scheme is derived and numerical results are provided to demonstrate the difference in the system throughputs by the proposed scheme and the optimal SC as well as TDM. With the proposed scheme, a good tradeoff between performance and complexity can be achieved. It is shown that the proposed scheme can reduce the implementation complexity considerably at the cost of a little system throughput loss.