What will we all soon be using the spaces in Freeview for?
You might get the Internet, or a better road trip ? all due to white spaces. Photograph: Shutterstock
The traditional 21 to 68 channel allocation for UHF television signal has been familiar for most readers I'm sure. It's not that long ago that we were twiddling our knobs (pardon the expression!) to tune in channel 4 (and channel 5 if you could receive it) in the analogue days; I hesitate to use the phrase "good old days" though!
Allocating this amount of spectrum for 4 or 5 television channels seems over the top but the innovators back in the early days really had their work cut out for them to fit a monochrome television signal into as small transmission bandwidth as possible; this was compounded further with the introduction of PAL colour television which also had to fit into the existing spectrum. The intricacies of the PAL system and how they managed to do this I think is incredible; signal interleaving, delay lines, colour difference signals and many other innovative techniques was human ingenuity at its best. Enough reminiscing though?
So now we are in the digital television age with hundreds of television channels to choose from (I do sometimes wonder whether there has been a backwards step in programme content though!) all having to co-exist with the analogue signals in the transition period of digital switchover but now solely providing our television viewing experience still in this vast bandwidth spectrum - albeit reduced with the implementation of 800MHz 4G transmissions last year. Do we really need this entire spectrum for digital television signals? Well the answer as we should already be aware is an emphatic "NO"!
4G is here to stay and the next spectrum clearance is just around the corner which will eat into the TV UHF spectrum at 700MHz with the potential for future mobile broadband (5G) services projected for around 2018. This will reduce the television spectrum further giving us Ch21 to Ch48 for television broadcasts but not for a few years. However, interesting things are also happening already in the Ch21 to Ch60 DTT spectrum with the advent of white space technology.
The DTT spectrum is very much sought after because it combines a wide coverage area with high bandwidth - exactly why broadcasters decided to use these frequencies for analogue television decades ago! Now, white space technology and white space devices (WSDs) are very clever; WSDs use frequencies that, in the locality of the device, are unused. This means that they can be interleaved in the DTT spectrum and can co-exist with DTT signals. This means that you could plonk WSDs in any area in the UK and they will work quite happily alongside DTT signals and shouldn't interfere with television signals. Time will tell on the latter point but if the impact of interference caused by 4G signals is anything to go by then we shouldn't be too worried.
OFCOM are currently road testing white space technology in various parts of the UK with various applications and with support from organisations including Microsoft, BT, Neul, Click4Internet, KTS and SineCom with the testing scheduled to be completed in spring this year. Impact on the signal reception industry of this testing appears to be minimal - as it should be due to the white space devices utilising unused DTT frequencies available in their locale.
The testing gives a good insight into how WSDs and the technology is likely to develop and how it is likely to emerge into all areas of the UK;
- Road traffic management - BT and Neul are working with the Department for Transport to transmit data on traffic volume, conditions and congestion on part of the A14 between Cambridge and Felixstowe
- Glasgow currently has the lowest use of broadband services in the UK and Microsoft are working with the University of Strathclyde to test how white spaces can enable access to wifi and to create a "smart city". Microsoft are also working with MediaTek and 6Harmonics to develop an international standard for WSDs called IEEE 802.11af
- Conventional broadband reception in very rural areas can be very challenging and Click4Internet, KTS and SineCom are using white space technology in areas including Hampshire, West Sussex, Dorset and IoW to enable broadband reception
- LoveHz and MLL Telecom are developing a white space network in Oxford for applications that monitor the environment and manage the efficiency of buildings
Due to the nature of white space devices and the frequencies that they use, even though they are in the conventional UHF TV spectrum, they should not cause any interference to DTT reception as they utilise local frequencies that are unused by DTT signals. However, if any form of DTT interference is suspected (including from white space devices), then the RDI recommends that this is confirmed using a spectrum analyser before any remedial action is attempted.
More information can be found at www.rdi-online.co.uk Ofcom
and Centre for White Space Communications