Massive MIMO (M-MIMO)
Massive MIMO uses antenna arrays with many elements, often 64 or more, to serve several users at once on the same frequency with separate beams.
What is Massive MIMO (M-MIMO)?
Ordinary MIMO uses a handful of antennas. Massive MIMO scales this up so that the base station can form many narrow beams and also steer "nulls" towards other users to avoid interference. It works best where signals scatter richly (non-line-of-sight), in TDD bands where the uplink can be used to learn the downlink channel, and in the 5G mid-band (FR1). It needs accurate channel knowledge and highly linear, well-calibrated radios, so it costs more than simple beam steering.