Ofcom moves to protect Freeview interference from 4G mobile devices
Ofcom has estimated it will cost £100m to deal with Freeview users who are located near to the transmitters for the next generation of mobile broadband services, which will use the frequencies (791 to 862 MHz) previously used for analogue television.
Once switchover is complete, over 10 million homes in the UK will use Freeview for their only television reception, and almost all of the remaining 17 million homes will use the terrestrial digital television service on their secondary TV sets.
The signals are provided from two types of transmitter. First there are around 80 high power transmitters located on hills that serve very large areas, such as the Crystal Palace transmitter (4.5 million homes in London), Winter Hill (2.7 million homes in the North West of England) and Sutton Coldfield (1.8 million homes in Birmingham). In addition there will be over 1,000 fill-in Freeview light transmitters, such as Boddam, which serves just 600 homes.
In contrast, the new 4G mobile services will use around 9,000 smaller transmitters located near where the services are required, which follows the current model for mobile phone networks.
4G transmitter interference locationIn places where the 4G transmitter is located close to homes receiving Freeview, it is likely that Freeview viewers will experience to forms of interference:
Signal overload - when a Freeview receiver is overloaded because the total input signal level is more than a certain level, the whole receiver will stop working and all television services will be lost.
Signal-Interference Noise Ratio degradation: this is where reception breaks down because the receiver can no longer decode the digital information in the transmission. This could affect a single multiplex or could take out all services.
The "overload zone" will occur for Freeview viewers located close to the 4G transmitter, with the "degradation zone" will affect those slightly further from the 4G transmitter:
Interference factorsNot all 4G transmitters will cause problems for Freeview reception, the other factors are:
The types of Freeview installation, with single unamplified aerials to a single set have the best resilience, with communal and systems with amplifiers more likely to suffer. The 4G transmissions are capable of overloading most types of TV amplifier.
The frequencies used for the DTT services being received, with those on the adjacent C60 being worst, C52 to C59 second worst and those on lower frequencies having the best chance of avoiding interference.
The strength of the Freeview signal received is another factor, with those with weaker signals due to being distant from the Freeview transmitter, having the most potential for 4G interference.
Not all 4G transmitters will use the same frequency, those that happen to use the lower frequency allocation having the most potential to cause Freeview interference, and those that transmit at higher power levels having more effect than low power 4G transmitters.
Homes affected by 4G interference without interventionOfcom calculate that:
Of the 16.3 million UK homes with a standard (unamplified, unshared) Freeview reception, 110,000 (0.67%) would be effected.
Of the 5.2 million homes using communal aerials systems, 550,000 (10.6%) will have problems.
Of the 5.6 million homes using amplified Freeview reception, 100,000 (1.8%) will experience problems.
Prevention and mitigationThere are several ways to deal with these 760,000 homes that will have problems.
Signal filtersUse of signal filters for the Freeview reception combined with Fitting of filters at 4G transmitters.
Ofcom's modelling finds that this is the most effective way of dealing with the 4G interference problems. Of the 110,000 standard Freeview installation homes, 87,000 will have their reception restored this way, almost 100% of the 550,000 homes with communal systems will be mitigated with filtering and 93% of the 100,000 domestic installations with amplifiers.
The total cost will be £20m for the Freeview filters and £33m for fitting of the filters in homes. Also, for the domestic filtering to be effective, the 4G providers will also have to spend around £11 fitting filters at the 4G transmitters when they are being installed.
Freeview equipment adjustmentAfter the provision of filters, there will still be 23,000 homes with unamplified and 7,000 homes with amplified Freeview reception equipment that are unable to receive their services.
Some of these homes will simply need a new Freeview box for each TV set. Whilst these boxes cost around £15, the requirement to fit these and provide for each set could come to as much as £200.
Another option, for at least 20% of homes, is to receive the Freeview services from an alternative transmitter. However, this could lead to the provision of the 'wrong' version of BBC One, BBC Two, ITV1 and Channel 4/S4C to the home. Ofcom is unsure if this will be an effective mitigation.
On Channel RepeatersThe use of On Channel Repeters (OCR) to rebroadcast the Freeview signals at higher power levels in the interference area was considered by Ofcom, but the high cost and unknown effectiveness has caused them to be distrgarded as a viable option.
Ensure 4G polarization is opposite to Freeview polarizationBecause of several factors, Ofcom does not consider that this will help prevent 4G interference of Freeview reception.
4G transmitter power reductionOfcom have concluded that causing service reception problems for the new 4G mobile services is undesirable for the services to be successful.
Provision of Freesat or free Virgin Media services for affected homesThis leaves providing a replacement Freesat installation (including multiple sets and Freesat+ boxes) for the 30,000 homes with their Freeview reception disabled, or the funding of a basic Virgin Media package. The total cost for this is £10m.
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Experience since the beginnings of DSO strangely gives rise to the audacious suspicion that sell-off profit is the main priority and that interference and reception issues are an irritation to be ignored as far as possible, with the odd sop dispensed to appease the masses. The auction-off of the 600 and 800MHz bands portends more excitement to come.
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Where are these transmitters. Are they the phone transmitters. How close is close to transmitter and how far is far from the transmitter? How about some raw technical information. Who pays for the upkeep of new freeview box or replacement equipment when it needs replacing that is supplied because you can't get freeview.
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Will this second digital switch over take care of this 4G problem?
International agreement ramps up pressure for another TV switchover | SourceWire
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Nothing is truly free someone has to pay for someone else's error, and then pass the cost on to their customers. And so this time it is the mobile providers, who are merely using the frequencies they were allocated ? IMO I think it should be out of the bank balances of those who messed up on the frequency allocation. Why should mobile users end up paying for OFCOM admin mess-ups ?
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bought a full hd setup , I wonder if it will be a similar farce that happened with freeview boxes that were bust by freeview changes and rendered useless ? seems stupid to me to even contemplate rolling out 4g so close to the tv bandwith , tv is crap enough without interference from mobile phones , no doubt the lure of a payout for those affected will indeed pacify some people , it amazes me the ordinary person gets fleeced right left and centre true things have to change and cant stay static but commonsense should prevail and frequencies that dont clash or other solutions should be sort , well if it messes up my tv i will scap the tv I wont miss it i will then not have to fork out for a tv licence as i wont have one! with my compensation i would buy a monitor and blu ray player and abandon freeview if everyone did same I would bet a better solution would soon be forthcoming
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the source info OFCOM works from must be suspect. For example, digitaluk sent my motherin-law confusing information, saying her Sudbury transmitter is stopping analogue transmissions. However, walking down her road, the 100 or so homes all have antenna pointing to crystal palace. The local phone mast is directly in line (and only 100 yds from my home) with an application already in pace for 12 antennae. So, if the source data on those using any particular base is wrong, what hope is there for anywhere else?
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neil: As there will be no changes to any of the television broadcasts when the LTE services start, you will never need a new box. If you have your own aerial, then you have a one-in-a-hundred chance of needing to fit a small filter which will be done at no charge to you!
There's a huge amount of allocation in the radio spectrum - have you ever seen http://ukfree.tv/styles/i….jpg ?
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