Massive MIMO Channel Models: A Survey

Table 1

Features of massive MIMO.

	Feature	Main reason
Advantages	High spectrum efficiency [6, 9]	Large multiplexing gain and array gain
	High energy efficiency [6, 9]	Radiated energy can be concentrated on UE
	High reliability [9]	Large diversity gain
	Efficient linear precoder/detector [9]	Favorable propagation condition for i.i.d. Rayleigh channel
	Weak interuser interference and enhanced physical security [6]	Orthogonal UE channels and extremely narrow beam
	Simple scheduling scheme [16]	Channel harden phenomenon averages out the fast fading
	Robust to individual element failure [6]	Large number of antenna array elements
Disadvantages	Pilot contamination [8]	Limited orthogonal pilots as of bounded coherent interval and bandwidth
	High signal processing complexity [9]	Large number of antennas and multiplexing UE
	Sensitive to beam alignment [6]	Extremely narrow beam is sensitive to UE moving or antenna array swaying
	Poor broadcast channel [6]	Be blind to UE positions