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Ofcom moves to protect Freeview interference from 4G mobile devices

Don't worry - Ofcom will ensure that everyone effected by 4G interference will still be able to watch digital television, and at no cost to the affected viewers.

Don't worry - Ofcom will ensure that everyone effected by 4G in
published on UK Free TV

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 location

In 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 factors

Not 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 intervention

Ofcom 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 mitigation

There are several ways to deal with these 760,000 homes that will have problems.

Signal filters

Use 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 adjustment

After 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 Repeaters

The 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 polarization

Because of several factors, Ofcom does not consider that this will help prevent 4G interference of Freeview reception.

4G transmitter power reduction

Ofcom 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 homes

This 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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In this section
Ofcom announces 700 MHz clearance schedule 2017-201
When will I get a new Freeview aerial because of even more mobile broadband? 2
Do not forget that 4G starting soon in 20 cities and towns really soon3
Using UHF channels C61 to C69? Time to retune4
Two final Freeview retunes in Scotland on 24 and 31 July 20135
800MHz band cleared by Digital UK - ready for nationwide 4G use6

Comments
Saturday, 5 May 2012
T
T. N. Thompson
9:57 AM

Yet again, the Government and Ofcom withholding vital information from the general public. It is my opinion that Ofcom are misleading people with their interpretation of how many are going to be effected. With this evil government, the cost of negating this interference will fall on people, allready reeling from Cameron's cuts. This problem is being mishandled as usual by incompetant government ministers and Ofcom operatives.

link to this comment
T. N. Thompson's 1 post GB
Sunday, 6 May 2012
M
michael
sentiment_satisfiedGold

9:37 AM

1. There should be a gap between highest DTT and lowest 4G frequencies sufficient to limit interference and to reduce investment to provide filters etc.

2. Any replacement costs for consumer equipment bought in good faith before 4G inception must be borne quibble-free by the 4G operators.

3. 4G licences should include the obligation to provide low-power SFN DTT PSB and COM relays on 4G masts.

4. Why should demand by the affluent for 4G services disadvantage further less affluent viewers who cannot afford them?

link to this comment
michael's 857 posts GB
Friday, 18 May 2012
Briantist
sentiment_very_satisfiedOwner

3:57 PM

michael: 1. There is - there is a "guard band".

2. No consumer equipment will be effected, only the signals supplied to them.

3. That can't work. There are no frequencies for such services.

4. Because "money talks", of course.

link to this comment
Briantist's 38,844 posts GB
Briantist
sentiment_very_satisfiedOwner

4:00 PM

T. N. Thompson: What "vital information" is being withheld by providing a public consultation? That makes no sense to me at all.

link to this comment
Briantist's 38,844 posts GB
Saturday, 30 June 2012
D
Deeque
5:38 PM

Will Scarborough be affected by a 4G transmitter please, if so, what area.


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Deeque's 1 post GB
Dave Lindsay
sentiment_very_satisfiedPlatinum

5:52 PM

Deeque: It depends on which transmitter is being received from!

There is a retune event scheduled for next May when ArqB (Yesterday etc) from Oliver's Mount will move from C61 to C49.

This is to clear channels 61 to 69 so the spectrum can be sold off to 4G operators.

D3&4 (ITV1, C4 etc) uses C60- which is obviously close, but I've no idea whether this might be a problem.

If you receive Tyne Tees from Bilsdale Moor, then the 4G services shouldn't affect it because it uses lower frequencies (and will continue to do so after it has switched).

link to this comment
Dave Lindsay's 5,724 posts GB
Dave Lindsay
sentiment_very_satisfiedPlatinum

8:00 PM

Deeque: I have thought further about this.

Whilst the likelihood of interference obviously depends on the proximity to a 4G base station, it also depends on other factors such as sensitivity of equipment.

Another factor is how sensitive the receiving TV aerial is to the signal. For example, a TV aerial is most sensitive in the direction it faces and less so at the sides.

We can't know for certain where the mobile operators may choose to site their 4G base stations. However, in Scarborough, it would seem a pretty safe bet that one or more will wish to site their 4G base stations on the mast on Oliver's Mount, after all, it is visible at street level from most of the South side.

In such circumstances, TV aerials will be pointing in the direction of the 4G base station(s). Plus the TV aerials are vertically polarised (I assume that 4G will be vertically polarised). So I suppose that this will increase the likelihood of interference and I guess that this will be the case in other similar places where there is a local TV transmitter, as they often become a haven to the mobile operators due to the fact that they are sited on high ground.

link to this comment
Dave Lindsay's 5,724 posts GB
Tuesday, 3 July 2012
E
E Williams
8:58 PM

hello`, having read through about this new 4G
scaremongering I did not see any referance
to wether it will effect just tv aerial systems
for reception either indoor or outside aerials
or does it also affect CABLE TV entry from a box that is fitted outside your house.
Thank you if response.
E Williams, {roof aerial at present with Freeview]

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E Williams's 1 post GB
M
Mark Fletcher
sentiment_satisfiedGold

9:24 PM
Halifax

E Williams.It is highly unlikely that Cable TV (or Virgin Media) will be suspect to 4G interference as such.
As the saying goes "Believe it when one sees it" !

link to this comment
Mark Fletcher's 673 posts GB
Monday, 24 September 2012
P
Peter Dolman
5:10 PM

A Q for Mike Dimmick: You mentioned that the Mendip power levels had also increased since last week. Which muxes were these and can you tell me what they changed from and to? Are all Mendip muxes now at full power?
Best regards

Peter

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Peter Dolman's 13 posts GB
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