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Next generation mobile broadband (LTE) could interfere with Digital TV
Friday 03 June 2011 17:54:55 by John Hunt

Ofcom have warned that next-generation mobile broadband services using LTE (Long Term Evolution) could interfere with digital terrestrial TV (DTT), affecting around 3% of users in the UK (760,000 households). The problem exists as the DTT frequencies are so close to those which will be used by the mobile networks and some DTT receivers were designed to receive the whole of the frequency band including that which has been assigned for use for LTE.

Testing carried out by Ofcom found that households which use an amplifier are more prone to this problem as they get overloaded by the mobile signal more easily than a standard TV receiver. Ofcom have various proposals for ways to deal with this interference and that includes deploying satellite or cable services where restoring digital terrestrial TV is not possible. Other mitigation techniques include:

  • Filtering at the DTT receiver - A filter can be installed (between aerial and amplifier if an amplifier is being used) to stop the unwanted signals being received. This may include more advanced filters for communal aerial systems.
  • Filtering at the base station - Additional filtering would result in less interference to DTT services
  • Improvements and alterations to DTT equipment - The quality of DTT receiving equipment could be improved by using, for example, directional antennas and receivers with better immunity to channel interference.
  • Re-orienting DTT aerials
  • - Where more than one DTT signal can be received, re-orienting the aerial to an alternate receiver could decrease the level of interference.
  • Opposite polarisation to DTT
  • - Mobile networks could polarise the signal using vertical polarisation (or horizontal in regions where vertical is used by DTT)
  • Base station power reductions - Reducing the amount of power of the signal transmitted by mobile base stations could reduce interference but could also lead to degradation of mobile services.

Ofcom believe filtering should form a large portion of preferred mitigation options and modelling proposes that the use of receiver filters could decrease the affected households by around 90% and when combined with transmitter filters, this would reduce the amount affected to only 30,000 (down by 95%). Funding for this will be through the mobile network licensees (with receiver filters costing in the region of £10 for homes, but more where a communal aerial system is employed). One could perhaps argue that this should be funded by the digital switchover process which had an underspend of around £250m, but this money has already been appropriated for use for by BDUK (Broadband Delivery UK) for next-generation broadband services (which could include LTE).

The consultation is open for responses until the 11th August and the full document can be found here.


Posted by cyberdoyle over 6 years ago
you have to laugh.
Posted by otester over 6 years ago
Time for DTT to take a hike, I want my LTE!
Posted by Somerset over 6 years ago
So they cleared the frequencies and then discovered the issues?
Posted by timmay over 6 years ago
If you have a problem, which most will not simply get freesat of Sky. Simples.
Posted by timmay over 6 years ago
Really there is no point in Terrestrial TV. It's more expensive to maintain all the transmitters than a solar powered satellite! Scrap DTT and make even more frequencies available mobile broadband.
Posted by otester over 6 years ago

Amen to that.

BBC is already available to stream as well...
Posted by Croftie over 6 years ago
This is ridiculous, LTE needs to be stoped. If you want faster internet just use you landline.
Posted by otester over 6 years ago
"use you landline"

Posted by timmay over 6 years ago
Lol @Croftie

If land lines were good enough this web site wouldn't even exist!
Posted by zyborg47 over 6 years ago
I doubt very much if it will affect me, but it is still pathetic. why is nothing doen right in this country? It is all very well people saying get satellite, but some people have paid a lot of money for their Freeview equipment, so why should they spend out again, anyway why should people have to change again just so the government and mobile phone companies can make money?

anyway, this next generation mobile broadband, will only be available to people with plenty of money for a while. sort 3G out first.
Posted by alwall over 6 years ago
Does Ofcom no longer employ RF Planning/Propagation engineers? This was entirely predictable.
Posted by rizla over 6 years ago
"Does Ofcom no longer employ RF Planning/Propagation engineers?"

No and they haven't employed anyone like that for the best part of a decade. Ofcom "employs" private companies to tell then what they want to hear - and if its at all inconvenient (like the powerline garbage then Ofcom just cover it up.

Ofcom are a total unmitigated waste of time and money.
Posted by Tox-Laximus over 6 years ago
I have noticed all these radio waves are making people really stupid, soon we will all have to live in faraday cages.

Fry some chips instead of frying your brains :P
Posted by fibrebunny over 6 years ago
Oh noes mah brains did go get friededid. Oooosht shinies, look at all the purdy colours momma... =D
Posted by otester over 6 years ago

Operators just haven't been upgrading as demand increased, this is due to them being busy reclaiming the money spent on the ridiculously expensive licenses.

We will see the same thing happen at the next auction (another round of expensive licenses) and the same problems that affected 3.5/3.75G will now affect 3.9G (LTE).

I expect it won't be until 2020 that operators are able to invest enough to keep up with demand (paid of licenses by then).
Posted by AndrueC over 6 years ago
I doubt wireless will ever be a serious alternative to landline business. It's useful as a stop gap or for areas with no or poor service though. Unfortunately the same things that lead to areas having poor landline service also tend to make upgrading masts unlikely.

If a company can't be arsed to roll-out FTTx to a village then it's unlikely they'll bother to upgrade 'their' mast to 4G and/or invest in commensurate backhaul upgrades.
Posted by AndrueC over 6 years ago
Even if the upgrades are applied it still may not help.

Wireless just isn't well suited to singlecast operation. Sure a mast can have a lot of bandwidth but it reduces with distance, obstructions and interference. Then after all that you have to share the bandwidth with hundreds or thousands of other people.

So sure:100Mb/s at 3am standing underneath the transmitter. But at 5pm, a couple of kilometres way inside your house..not so much.
Posted by normcall over 6 years ago
Is it this RF band that the Nordic countries have suddenly found interferes with the railway signalling that uses pan-European assignments enshrined in EU law?
Posted by otester over 6 years ago

On the lower spectrum this will not be an issue, at 2km from the local mast, tonnes of houses between me and it I get a full O2 2G signal.

Dense areas tend to have better land line speeds hence spreading the load.

Operators can adjust price and/or usage to keep the speed up, take Vodafone for instance, expensive but speeds are great.
Posted by Bob_s2 over 6 years ago
OFCOM seem somewhat confused. They start off talking about it overloading the frond end of TV's so most of what they are on about with altering the direction of the TV aerial is largely irrelevent particular when the signal is from a mobile
Posted by Croftie over 6 years ago
That will teach me to post when I'm drunk.. momentarily forgot not everyone enjoys an FTTC connection like me LOL

LTE needs to be stopped. You don't need fast broadband on your phone, what are you going to do, stream HD to your 3" screen LOL
Posted by chriswharrad over 6 years ago
@ Croftie

And there was me thinking you made a rather witty remark about T-Mobile's fair use policy :)
Posted by adslmax over 6 years ago
I don't care about digital TV as it full of rubbish on freeview. I am more happy with Sky!
Posted by Tox-Laximus over 6 years ago
Maybe Aliens monitor all these transmissions, did anyone thinks of that?

And just maybe their favorite entertainment is watching the stupid earthlings cock everything up.
Posted by zyborg47 over 6 years ago
@ Tox-Laximus, all this digital stuff is so we can be spied and tracked. Well that is what someone I know thinks.
Posted by pfvincent over 6 years ago
I bought DTTVs as I don't want to stick a Sky aerial on the side of my house or pay Virgin for what is available free via Freeview, and with DTTV I can have as many TVs and recorders as I want, whereas both Virgin and Sky limit me to one TV, unless I pay extra for additional boxes.

I note that OFCOM say that receiver filters will cost "in the region of £10 for homes", but do not mention the cost of fitting them - I doubt if an aerial fitter would get out of his van for £10!
Posted by Tox-Laximus over 6 years ago
Its possible to network though the mains wiring of a house, so why not though the pylons?
Posted by michaels_perry over 6 years ago
This story has numerous technical errors and is misleading! They should be referring to the signal radiated from DTT and Mobile Pone base stations, all at fixed locations and of significant power output (ERP). Redirecting an aerial so it does not receive as much signal from an unwanted source has been standard TV reception practice for over 40 years. (TBC)
Posted by michaels_perry over 6 years ago
(Contd) Adding suitable filters has also brought benefits to many who suffered interference from other unwanted local sources. TV tuners, whether analogue or digital, are designed to minimise both co-channel and adjacent channel reception, but they are not perfect. Notch filters have helped in the past but have to be designed for a specific usage.
I speak as a retired TV engineer.
Posted by grisleyreg over 6 years ago
We live in a block of flats and very few residents are interested in Sky or freesat so freeview through amplifiers remains our only choice so lets hope nothing is allowed to interfere with that
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