“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 TV WS 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.
The yellow oval refers to “Licensed Access” which means the wireless spectrum is licensed to some organizations and only these licensed users have the rights to the spectrum, e.g., 3G or 4G cellular communications. The users could ‘use’ the spectrum by subscribing to the telecom operator who owned the spectrum but the users are not allowed to own the networks.
On the right-hand side, the orange 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!