IEEE Spectrum January, 2014 - 40

tHe lte-advanced
advantage

Up to 8x download speed

Up to 20 MHz

Up to
100 MHz

Known as "true 4G," LTEAdvanced includes a menu of
wireless technologies that will
boost the capacity of current
4G LTE networks and make
possible mobile download rates
as high as 3 gigabits per second.
Here are five key features that
distinguish the new standard
from its predecessors.

Macrocell

Up to 4x upload speed

WiDEr banDWiDth
Using a technology called carrier
aggregation, operators can
combine up to five LTE frequency
channels, or carriers, as wide as
20 megahertz that reside in different
parts of the radio spectrum.

morE Data strEams
LTE-Advanced supports more sophisticated multiple
input, multiple output (MIMO) techniques, which
enable several antennas to send and receive data. One
use of MIMO, called spatial multiplexing, separates
transmissions into many parallel streams, increasing
data rates in proportion to the number of antennas used.

Advanced relay

Expansion zone
smartEr rElays
Conventional radio repeaters, such as those used
in LTE networks, simply amplify transmissions
from a base station. LTE-Advanced allows for more
advanced relays, which first decode the signals
and then forward only those meant for nearby users,
increasing the total number each relay can serve.

support for small cElls
A protocol called enhanced inter-cell interference
coordination (eICIC) alleviates interference to a
small cell-a low-power base station whose coverage
zone lies inside a traditional macrocell. The two cells
can dynamically coordinate their use of spectrum,
letting the small cell expand its transmission range.

more consistent connections,
and cheaper data.
As its name implies,
LTE-Advanced is meant
to enhance LTE. The two
standards are mutually
compatible, which is great
for consumers. New LTEAdvanced phones will still
work on LTE networks, and
old LTE phones will connect
to LTE-Advanced networks.
Operators will benefit as well.
Those wishing to upgrade
to LTE-Advanced won't

need to scrape together new
radio spectrum or build out
new infrastructure as they
did to make the leap from
3G to LTE.
But here's the catch:
Carriers won't roll out all of
LTE-Advanced's capabilities
at once. Like LTE before
it, the new standard isn't
a single technology but
rather a grab bag of many
technologies, and operators
will pick and choose items
as they're needed. For

jan 2014

north american

Small cell

SPectrUm.ieee.orG

Fiber link
coorDinatED transmissions
To improve reception, LTE-Advanced introduces
coordinated multipoint (CoMP). It permits several
base stations to form a single cell, allowing a mobile
unit to connect with all of them at the same time. For
example, the unit could receive downloads from highpower towers while uploading to a nearby small cell.

instance, the South Korean
telcos that now claim to have
LTE-Advanced networks
are really talking about
just one of LTE-Advanced's
capabilities, known as
carrier aggregation.
This feature increases
the bandwidth available
to a mobile device by
stitching together frequency
channels, or carriers, that
reside in different parts
of the radio spectrum.
Ordinary LTE can deliver

data using a contiguous
block of frequencies up to
20 megahertz wide. But as
more and more companies
and devices vie for radio
spectrum, such wide swaths
are increasingly scarce. Most
operators, having bought
bits and pieces of spectrum
wherever they could, have
fragmented collections.
Carrier aggregation solves
that problem. It allows
operators to combine their
narrow, disjointed channels
illustration by

James Provost

http://SPectrUm.ieee.orG

Table of Contents for the Digital Edition of IEEE Spectrum January, 2014