What is TV White Space? -- Myth and truth explained
“TV White Spaces
(TVWS) are wireless spectrums in the TV bands that are not being fully utilized
by licensed services, such as TV broadcasting, and are made available for other
users on secondary basis provided the secondary users do not interfere with the
licensed services.”
I’ll elaborate more below.
First, let’s start with many questions people typically ask:
·
Is it an unlicensed spectrum? – not quite
·
Is it spectrum left over after analog to digital
TV switchover? – not quite
·
Is it a technology making use of broadcasting
for communication? – no
·
Is it allocated to somebody and only they could
offer TVWS services? – no
During my 11-year involvement in TVWS developments, I
encountered many people trying to define TVWS differently. Even some so-called
TVWS experts misunderstood the whole concept of TVWS. In this article, I
attempt to explain the concept of TVWS in a layman manner and clarify some
doubts. It is hope that with this series of articles, people become clearer
about the concept of TVWS and many more countries will open up TVWS and bring
benefits to the people.
White Space?
Before talking about TVWS, let’s be clear first what is
“White Space”. Without beating the bush, I use the diagram below to clearly
show the difference between white space and other current wireless systems.
On
the right-hand side, the yellow oval is the “Unlicensed Access” category where
systems operating in these spectrums do not need to acquire the spectrum as
long as they meet certain criteria and requirements stipulated by the
regulators. Typical examples of unlicensed access include Wi-Fi, Bluetooth,
ZigBee, etc. Anyone can setup their own Wi-Fi networks at home.
Interestingly
“White Space” falls in between these two categories. In white space, spectrum
is being allocated to “Primary Users” as in the case of licensed access.
However, since the allocated spectrum is not being fully utilized by the
primary users (either typically in time or space), “Secondary Users” are
allowed to use the spectrum on a non-interfering basis. This concept is
interesting as it allows secondary users to co-exist with primary users
dynamically in the same spectrum bands with primary users having priority over
secondary users. This dynamic co-existence results in better utilization of
spectrum, which is a scarce and valuable resource.
As
for TVWS, it is simply white space in the TV bands. Besides TV bands, we have
white spaces in the 3.5 GHz and other bands as well.
Now,
let’s summarize the characteristics of TVWS:
·
It uses wireless spectrum in the TV bands
·
It has primary users operating licensed services
·
The spectrum may not be fully utilized by the
primary users
·
Secondary users may use the underutilized
spectrum
·
Secondary users have to ensure they do not
interfere with the primary users
With
the above, I came out with the definition of TVWS as:
“TV White Spaces
(TVWS) are wireless spectrums in the TV bands that are not being fully utilized
by licensed services, such as TV broadcasting, and are made available for other
users on secondary basis provided the secondary users do not interfere with the
licensed services.”
So,
let’s revisit the four questions I posted above:
·
Is it an unlicensed spectrum?
o
As explained above, it has both licensed and
unlicensed components
·
Is it spectrum left over after analog to digital
TV switchover?
o
With the definition above, it is not necessarily
spectrum left over after digital switch over. In fact, a lot of countries
started to use TVWS even when their analog TV is still in operation. Digital
switchover opens up more opportunities for TVWS.
·
Is it a technology making use of broadcasting
for communication?
o
It has nothing to do with broadcasting except
that it uses the same wireless spectrum as broadcasting.
·
Is it allocated to somebody and only they could
offer TVWS services?
o
As long as the secondary systems meet certain
criteria set by the regulators, they are allowed to use TVWS spectrum. Spectrum
allocation typically happens to licensed services.
Finally, a question to the readers to ponder about. For TV
bands / channels totally freed up (i.e., no primary user) after digital
switchover, do / can they be considered as TVWS or unlicensed spectrum or they
should be licensed out to individual organizations? Which part of the figure
above should they belong to? Blue, green or yellow?
In my next article, I’ll discuss the last question as
opinion piece. Stay tune!
This is a series of articles aimed at sharing my views on
TVWS and other spectrum matters. I encourage the readers to share their views /
comments objectively in the comment section and together let’s promote this
topic to the wider audiences.
About the author:
Ser Wah OH is one of the pioneers in TVWS where he started working on TVWS
since 2006. He led a team and submitted a prototype to the landmark TVWS trial
by FCC in 2008 which indirectly helped FCC to open up TVWS in the US. After
that, he is actively involved in TVWS especially in the Asia Pacific region
where he was a key contributor to Singapore IMDA TVWS regulation, assumed the
role of co-chair of IMDA TVWS task force, sat in the IMDA Telecommunications
Standards Advisory Committee and co-founded the Singapore White Spaces Pilot
Group together with Microsoft and StarHub. He is frequently invited to deliver
keynote, speeches, panel discussions and masterclasses in various events
related to TVWS, spectrum regulations and smart cities. He was also a key contributor
behind many successful TVWS pilots and deployments in Singapore, Philippines, India,
Myanmar, China, Taiwan, Hong Kong, etc. He co-authored a book on TVWS which was
published by Wiley-IEEE Press to share his knowledge and many years of
experience in TVWS. In 2016, he co-founded a company Whizpace Pte Ltd to commercialize TVWS
solutions.
TVWS is allowed under an FCC Part 15 unlicensed rule.
ReplyDeleteIt is not the only unlicensed band shared with primary licensed users or primary federal government assignments (the word"license" is not used int he US for federal spectrum use, it is "assigned"). Indeed, most unlicensed bands have primary users.
TVWS is unusual in that the data base technique is used.
And also the sharing is dynamic instead of the largely static sharing. Thanks for your comments, spectrum guru :)
DeleteAnd also the sharing is dynamic instead of the largely static sharing. Thanks for your comments, spectrum guru :)
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