The narrow beam enabled by massive multi-input multi-output (MIMO) brings unprecedented spatial multiplexing. This brings new opportunity for multi-user MIMO (MU-MIMO) in the 5G era. This chapter proposes a new mechanism that jointly coordinates beamforming-based MU-MIMO, non-orthogonal multiple access (NOMA), and device-to-device (D2D) communications in a downlink cellular network. It develops two different precoding schemes. One aims to cancel out the BS to D2D users interference, while the other one aims to minimize interference among cellular users that coordinate with each other through NOMA and MU-MIMO beamforming. Within a NOMA group, cellular user (CU) with a weaker channel is normally allocated a higher downlink transmission power so that the strongest received signal within that NOMA group corresponds to the CU with the weakest channel gain in that group. The chapter solves the user grouping and power allocation problem, in order to maximize the total system throughput, based on the precoding scheme.