An effective interference mitigation scheme for downlink NOMA heterogeneous networks

Non-orthogonal multiple access (NOMA) is a promising technique to improve spectral efficiency in the fifth generation (5G) mobile communication networks. However, as multiple users are multiplexed on the same subchannel, the interference becomes more serious in NOMA heterogeneous networks than in OFDMA heterogeneous networks. Eliminating interference is an emergency issue, especially for cell edge users. In this paper, an effective interference mitigation scheme is proposed to improve spectrum efficiency for the downlink NOMA heterogeneous networks, which takes advantage of both coordinated multipoint (CoMP) transmission and load balance, including coordinated beamforming (BF) and joint transmission (JT). In order to reduce inter cell interference, beamforming matrix is designed according to maximum signal to leakage noise ratio criterion. Joint transmission is adopted to convert intra cell interference into signal. Simulation results show that the proposed scheme can improve spectrum efficiency obviously.