NOMA is a multiple access technique that enables multiple users to access the network simultaneously using the power domain. It allocates more power to cell-edge users and less power to near users. At the receiver side, near users perform SIC to decode and remove far users' signals before detecting their own signals. This allows NOMA to enhance reception capacity and throughput compared to the orthogonal multiple access schemes used in previous generations. NOMA is a promising technique for 5G networks to support massive connectivity.