of antennas. So Massive MIMO systems would now require
a large number of similar slots as compared to the conventional
MIMO system. Secondly, as the number of base
station antennas increases the number of the channel estimates
also increases for each terminal which in turn needed
hundred times more uplink slots to feedback the channel
responses to the base station. A general solution to this problem
is to work in Time Division Duplexing (TDD) mode
and depend on the reciprocity amid the uplink and downlink
channels [25].
Massive MIMO technology depends on phase coherent
signals from all the antennas at the base station, but the
computational processing of these signals is simple. Below
are certain positives of a massive MIMO system [24]: