Which of the following are true about M$-$MIMO? $($select all that apply$)$

$2$ points

Small cells must be used when deploying Massive MIMO

M$-$MIMO can only be used with mmWave deployments

Performance can be enhanced in both Sub$-6$ GHz and mmWave bands when M$-$MIMO is used

M$-$MIMO helps compensate for path loss in mmWave bands