Understanding LTE-Unlicensed // July 2015
Editor's Note
LTE-U Attracts
Controversy and
Industry support
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compete with Wi-Fi but in the same way that other Wi-
Fi competes with LTE.
"Suppose you have five channels and five users,"
Paolini said. "Each user gets a channel. If you have five
channels and ten users, each channel has two users,
on average. Inherently, in this case, LTE and Wi-Fi
compete for that spectrum. But that's no different from
Wi-Fi competing with other Wi-Fi users. So within a
channel you might have two LTE-U users, or one Wi-
Fi and one LTE user, or two Wi-Fi users, and if you
have good coexistence rules you can split the available
resources in a fair way."
What about the operator perspective? "Suppose you're
an operator, and you need more capacity in an airport,"
said Paolini. "Do you use LTE-U or Wi-Fi? You can
use both, but if you have so much money to cover the
airport, some of that money will go to Wi-Fi and some
to LTE-U, or it might go only to one or the other, but
if they do, the same coexistence rules apply. So in that
sense, they compete with each other from an operator
point of view."
Skepticism remains
It's worth mentioning that mobile operators have been
using "unlicensed" spectrum for Wi-Fi for a long time.
"Most traffic that goes over mobile phones is over Wi-
Fi—not cellular," said Paolini. "So, mobile operators
are accustomed to using spectrum they don't own.
They don't have to pay for anything in that scenario.
It's unlicensed Wi-Fi infrastructure—a win-win
situation."
With LTE-U/LAA, however, to use unlicensed
spectrum, the operator has to invest in the
infrastructure. "It's fundamentally different from using
Wi-Fi to support additional access from a phone," said
Paolini. "The operator has to spend money on the
network to support the unlicensed band. This is really
where operators have been skeptical."
Operators can own, manage, and control licensed
spectrum as they see fit. Whatever money they spend
there, they know that the infrastructure is only for them.
When operators invest in unlicensed spectrum, whether
Wi-Fi or LTE-U, they're investing in infrastructure
but they can't control that infrastructure the same way.
They must fit in with others who are using that band.
The more parties that want to use that spectrum, the
lower the performance. So notions such as return on
investment (ROI) are more difficult to gauge.
>> Can LTE and Wi-Fi Coexist in the Same Spectrum Band?
"Most traffic that goes over
mobile phones is over Wi-Fi—not
cellular. So, mobile operators are
accustomed to using spectrum
they don't own. They don't have
to pay for anything in that scenario. It's
unlicensed Wi-Fi infrastructure—a win-win
situation."
MONICA PAOLINI, ANALYST, SENZA-FILA
