Non-orthogonal multiple access with weighted sum-rate optimization for downlink broadcast channel

This paper presents a novel non-orthogonal multiple access (NOMA) scheme applicable to the multiple-input multiple-output (MIMO) downlink broadcast system. An optimal iterative beamforming design is utilized to the NOMA scheme. The weighted sum rate is used as the objective criterion to design the beamforming matrix at the base station (BS). The users in a typical cluster located in the same radiation beam are precoded in the same weighting factors. We propose an algorithm to schedule the users into clusters to achieve a higher sum-rate. The signals of users in one cluster are precoded in the NOMA scheme. The successive interference cancelation (SIC) technique is used at the receiver to extract the desired signal from a superposition signal. To take advantage of the SIC, a power allocation algorithm is proposed to further increase the sum-rate of this system and guarantee the performance of users with the weak channel condition. Numerical results show that the proposed NOMA scheme, together with the beamforming, user scheduling, and power allocation, can significantly improve the system performance.