Non-Coherent NOMA With Massive MIMO

By accommodating overlapping transmissions over non-orthogonal resources, non-orthogonal multiple access (NOMA) integrated with massive multiple-input multiple-output (MIMO) can boost spectral efficiency and obtain vast diversity for wireless multiuser systems. However, NOMA requires channel state information (CSI) at the receiver for coherent detection, resulting in unaffordable complexity in the channel estimation as the number of users goes large. Add to that, the introduction of massive MIMO makes the channel estimation even more challenging. In this letter, we propose a blind belief propagation (BP) detection for non-coherent NOMA with massive MIMO, where the transmitter of each user first performs differential modulation on PSK symbols, and then spreads its symbols using low-density spreading (LDS); the receiver of base station (BS) employs differential demodulation and then detects all users' symbols using a blind BP detection without knowledge of CSI. Simulation results show that the proposed blind BP detection can not only support the overloaded users, but also achieve BER performance very close to that of point-to-point systems.