Television broadcasting through terrestrial transmission has been ongoing since the 1920s. Typically these transmissions use the UHF and VHF part of the electromagnetic spectrum (RF), where multiple channels are arranged next to each other, separated by a guard band – called the white-space.
After nearly 80 odd years, this method of transmission – which has, over the years continued as the cheapest way of delivering programs, and has been favoured by Governments in some parts because of this – is being sunset.
The Digital Dividend
As we are all aware, traditional analog TV transmission over the air, focused on modulating the UHF/VHF band frequencies by deliveriing intelligence about rasterised image snapshots from realtime arranged in sequence timewise to deliver the desired result on the human visual apparatus.
Obviously, there was a lot of inefficiencies in this approach – scenes, sometimes don’t change much between two snapshots but the transmission carried an entire snapshot. This is why modern video coding techniques have focused on what is called “Entropy Coding” – crudely stated, this refers to the mechanism by which only the differences between the snapshots is transmitted once an initial full snapshot is transmitted.
Anyone with a basic Information Theory background can see that this would result in a very efficient coding and which, in turn can be delivered using lesser bandwidth. Coupling this with more modern advances in Channel Coding principles, we can see that there is a lot of spectrum that can be reclaimed from the analog TV providers if they change to Digital Transmission.
This is what is being termed as the “Digital Dividend”.
It is with reclaiming the spectrum and putting it to good use that EU, in alignment with ITU, had taken a decision that they would turn off all analog transmissions by 2012. As of time of this post, I understand that all EU countries except two have complied.
I have also come across initiatives in the US, Australia and some parts of the Middle East where these initiatives were undertaken.
In the UK too, the industry has taken up freeing up the spectrum and earning the Digital Dividend. A recent consultation from Ofcom on reuse of the spectrum has the following diagram to indicate the amount of white-space that has been created through the process of moving from Analog to Digital Transmission.
Reinvesting the Dividend
How can this reclaimed be put to use? In the UK, Ofcom proposes to open up this spectrum to unlicensed use by devices – for various solutions ranging from M2M requirements to others. The only condition that has been imposed is that the devices maintain integrity within the band of operation and ensure that they don’t interfere with the commercial bands in the vicinity.
To achieve this, they propose to have in place a database – that would be recognized by Ofcom – which maintains location-wise availability of spectrum and currently assigned usage. All devices intending to use them can discover the database and request for free spectrum to be used. The figure that they have provided is as given below.
I was quite thrilled by looking at this idea because of its resemblance to what I had posted earlier – see http://wp.me/pAb4X-2X (A Spectrum Management Idea, August 8, 2012).
Gazing Into The Future
I feel that in the absencee of any immediate integrated devices coming out in the market in the immediate future, there would be products that act as gateways that will come up first. This would enable that legacy equipment are not forced to upgrade to support the Ofcom framework.
I also feel that beyond the communication needs for M2M, there would be certain new class of services – including some personalized ones that would come up. Looking forward to readers of this post to comment on any ideas they can get.
Lastly, while this is fairly easy to offer in an unlicensed spectrum, I wonder how easy it would be to make such a dynamic spectrum allocation happen for licensed spectrum as outlined in my previous post.