White spaces can be used to deliver broadband to the parts ADSL cannot reach, writes Julian Clover.
There are a few items in this world that are in short supply, oil, time and spectrum.
A few times recently I’ve heard data described as being “the new oil”, surely the reverse is true, when data is being produced more and more as an essential part of the chain from production to living room.
When it comes to spectrum we have to make do with what we’ve got, live with the decisions of the past, and the legacy that comes with them. Richard Walker, of Cambridge-based The Technology Partnership (TTP) goes to far as to throw out the tried and tested transmitter on the hill concept, suggesting that if we were starting from scratch then we would be better to devote the spectrum to IP.
As it happens TTP is involved in the Cambridge ‘white space’ trial, using spectrum in between that used for broadcast television for the delivery of broadband to rural areas.
Such experiments are not necessarily about the telcos getting hold of spectrum that broadcasters once thought to be their own. This week TTP announced that it had successfully used white space technology to get a 5.4 Mbps broadband connection across 5.6km from its offices to the rural village of Orwell. The connection was then used to stream content from the BBC iPlayer. Despite occasional ‘predictions’ about the health care and educational services that will benefit those connected to broadband, we all know what most of the bandwidth is actually used for.
Its likely that an over the air solution could take at least 2 Mbps a distance between 8 and 10km. ADSL is not only restricted to the distance from the exchange, but this mind bend and curl and the copper wire makes its way through town.
The directional nature of the antenna means that the spectrum assigned to such services can be reused many times over. The consumer just needs to install a second antenna, separate to that used for television services.
But just how much spectrum is available to be reused in this way? According to Walker, across the UK there is some 160 MHz available, depending on how else the spectrum is taken up. Of this 100 MHz is typically reuseable, though for this trial the safe resolution area has been set at 60 MHz.
Walker points out that the available white space capacity is more than all the 3G networks put together. This throws up a rather interesting conundrum: does the release of such spectrum reduce the amount that any spectrum sale could achieve, also devaluing that already in the hands of the telcos, or will that be counterbalanced by the demands of video on all spectrum.
The UK is ahead in working out what can be achieved with the available white spectrum, and with the possibility of a permanent solution in place by 2013, providing an opportunity for any cable operator wanting to go off net.
