MIMO systems consist of multiple antennas at
both the transmitter and receiver. By adding
multiple antennas, a greater degree of freedom
(in addition to time and frequency dimensions)
in wireless channels can be offered to accommodate
more information data. Hence, a significant
performance improvement can be
obtained in terms of reliability, spectral efficiency,
and energy efficiency. In massive MIMO
systems, the transmitter and/or receiver are
equipped with a large number of antenna elements
(typically tens or even hundreds). Note
that the transmit antennas can be co-located or
distributed (i.e., a DAS system) in different
applications. Also, the enormous number of
receive antennas can be possessed by one device
or distributed to many devices. Besides inheriting
the benefits of conventional MIMO systems,
a massive MIMO system can also
significantly enhance both spectral efficiency
and energy efficiency [9]. Furthermore, in massive
MIMO systems, the effects of noise and
fast fading vanish, and intracell interference
can be mitigated using simple linear precoding
and detection methods. By properly using multiuser
MIMO (MU-MIMO) in massive MIMO
systems, the medium access control (MAC)
layer design can be simplified by avoiding complicated scheduling algorithms [14]. With MUMIMO,
the BS can send separate signals to
individual users using the same time-frequency
resource, as first pro. Consequently, these main
advantages enable the massive MIMO system
to be a promising candidate for 5G wireless
communication networks.
MIMO systems consist of multiple antennas atboth the transmitter and receiver. By addingmultiple antennas, a greater degree of freedom(in addition to time and frequency dimensions)in wireless channels can be offered to accommodatemore information data. Hence, a significantperformance improvement can beobtained in terms of reliability, spectral efficiency,and energy efficiency. In massive MIMOsystems, the transmitter and/or receiver areequipped with a large number of antenna elements(typically tens or even hundreds). Notethat the transmit antennas can be co-located ordistributed (i.e., a DAS system) in differentapplications. Also, the enormous number ofreceive antennas can be possessed by one deviceor distributed to many devices. Besides inheritingthe benefits of conventional MIMO systems,a massive MIMO system can alsosignificantly enhance both spectral efficiencyand energy efficiency [9]. Furthermore, in massiveMIMO systems, the effects of noise andfast fading vanish, and intracell interferencecan be mitigated using simple linear precodingand detection methods. By properly using multiuserMIMO (MU-MIMO) in massive MIMOsystems, the medium access control (MAC)layer design can be simplified by avoiding complicated scheduling algorithms [14]. With MUMIMO,the BS can send separate signals toindividual users using the same time-frequencyresource, as first pro. Consequently, these mainadvantages enable the massive MIMO systemto be a promising candidate for 5G wirelesscommunication networks.
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