4
5
MASSIVE MIMO AND 4X4 MIMO
5G will enable the connection of many more devices
to the network. Consequently, 5G will require ample
capacity to support the massive volumes of data
passing through the network. This is where and
why massive MIMO and 4-by-4 MIMO will play
an important role. MIMO is defined as “Multiple
In-Multiple Out” and it simply refers to multiple
antennas that send and receive wireless signals in
order to provide more capacity and faster speeds.
MASSIVE MIMO essentially constitutes a
lot of antennas at a base station serving many
users simultaneously. A recent iBwave whitepaper
suggests that 44 antennas may reside inside a single
panel3 rather than the one or two antennas that are
commonly found inside panels today. Because this
34 I ICT TODAY
technology will increase capacity for base stations at
cell towers, massive MIMO will be deployed mainly
for outdoor coverage. It will not likely be deployed for
in-building networks due to the sheer size and cost.
4X4 MIMO, on the other hand, will be deployed
for in-building networks. In fact, 4x4 MIMO is
already being designed and deployed for some
in-building networks. 4X4 MIMO is similar to a
present-day MIMO system, except instead of having
two infrastructure layers, it has four layers: four
headend units, four remotes, and, consequently, four
cable runs from the remotes to the antennas for each
sector. 4X4 MIMO can provide much more capacity
to serve tomorrow’s wireless needs throughout
many venues.
CBRS
Citizens Broadband Radio Service (CBRS) uses time
division LTE (TD-LTE) to provide a wireless voice and
data service at 3.5 GHz (3550 MHz to 3700 MHz). The
radio interface is identical to LTE at other frequencies,
thereby supporting voice, text and data services with
seamless mobility. It is governed by a three-tiered
spectrum authorization framework to accommodate a
variety of commercial uses on a shared basis with
incumbent federal and non-federal users of the band.
Access and operations will be managed by a dynamic,
tiered, spectrum access system. The three tiers are
Incumbent Access, Priority Access, and General
Authorized Access:
• INCUMBENT ACCESS includes mainly U.S.
Naval Radar.
• PRIORITY ACCESS means an organization can
pay a fee for a Priority Access License (PAL). Each
PAL is defined as a non-renewable authorization to
use a 10-megahertz channel in a single census tract
for three years.
• GENERAL AUTHORIZED ACCESS (GAA)
is licensed-by-rule to permit open and flexible
access to the band for the widest possible group of
potential users. This GAA tier is slated for use by
enterprise customers.
In the future, OEMS will develop cloud-RAN solutions where
virtualized servers and software drive down further the overall
cost and complexity of in-building networks.