NOMA in multiuser MIMO systems with imperfect CSI

This paper considers the use of NOMA in multiuser MIMO systems in practical scenarios where CSI is acquired through pilot signaling. A new NOMA scheme that uses shared pilots is proposed. Achievable rate analysis is carried out for a pilot signaling scheme including both uplink and downlink pilots. The achievable rate of the proposed NOMA scheme with shared pilots in each NOMA group is compared with the traditional orthogonal access scheme with orthogonal pilots. Numerical results show that when estimated downlink CSI is available at the users, our proposed NOMA scheme outperforms orthogonal schemes. With increasing number of antennas at the base station, the gain from our proposed NOMA scheme is also increasing. This shows that there is a benefit of applying the proposed NOMA scheme in massive MIMO systems.