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Introducing 4G services in the 800 MHz band in the United Kingdom
Last February, the communications regulator Ofcom announced that the telecom operators Everything Everywhere (EE), Telefonica UK, Three and Vodafone had acquired licenses to operate 4G services in the 800 MHz band. These licenses were awarded as a result of the spectrum auction for licenses in the 800 MHz and 2.6 GHz bands that generated £2.3 billion in revenue. Services are now set to launch this summer.
Across Europe, national administrations have agreed to allocate the 800 MHz band to 4G services in a harmonized way. However, the use of the 800 MHz band for two-way communication services, such as wireless telecom services, risks causing disturbances to the reception of DTT services. Viewers may find that their television reception is blocky, without sound or missing altogether.
As a result, telecom operators in the United Kingdom with services operating in the 800 MHz band were required to set up and fund an organization to provide corrective support to households whose DTT reception could be affected by the launch of 4G services. In anticipation of the spectrum auction, telecom operators set up Digital Mobile Spectrum Limited (DMSL) in October 2012 with a funding of £180 million. The organization is overseen by a board with representatives from broadcasters, Ofcom, the Department for Culture Media and Sport as well as viewers. The organization is made known to the public using the trademark ‘at800’ and has a public and industry website portal ‘at800.tv’. It is presently sending out tens of thousands of postcards in the 4G pilot launch areas with the headline ‘at800 – Here to sort out Freeview disruption’.
4G@800 MHz trials
In anticipation of the roll-out of 4G services as of mid-2013, at800 has begun to undertake pilots in select parts of the country to better understand how the provision of 4G services operating in the 800 MHz band affects DTT reception. A total of 5 trials have taken place or are currently ongoing with the cooperation of broadcasters.
The first trial took place in Cradley Heath and Rowley Regis (Dudley) in the West Midlands from 18 to 30 March. In anticipation of the trial, 22,000 households located near the 4G transmission masts were sent information about the planned trial. Forecasting models predicted that 120 households would be affected by 4G interference. However, only 15 households reported problems and only 100 calls in total were made to the at800 call centre. The trial showed that reception issues caused by 4G services operating in the 800 MHz band were in households using signal amplifiers, whether from a communal antenna or a domestic installation.
Two separate trials are currently underway in London and initial results have confirmed that there is a low risk of 4G interference to DTT reception. This is due partially to the strong DTT signal transmitted from the Crystal Palace tower that reduces the need for households to use signal pre-amplifiers, and to the large separation between the frequencies used by the DTT platform and the 4G platform (the highest frequency used by the DTT platform is 540 MHz while the 4G platform begins at 791 MHz).
The trial in West London has sent free filters to 27,000 households located in areas that could potentially have DTT reception problems in an attempt to better understand whether receiving such a filter improves public awareness of the issue, and if viewers have problems in fitting the filters. Because the other trials did not proactively send filters to viewers, this trial will also help determine subsequently whether fewer problems will be reported.
The trial in Brighton, which began in mid-May, is testing for potential 4G interference in an area with a varied terrain and where the DTT platform uses frequencies much closer to those used by 4G services. A total of 80,000 letters were send to household and businesses as were 2,424 free filters. A trial is also underway in York to help refine at800's approach to predicting where interference may occur.
Trial results so far indicate that fewer households than previously estimated may experience interference to their DTT reception once 4G services are launched in the 800 MHz band. Currently, at800 estimates that about 90,000 households will experience some disruption, which represents less than 1% of all television households that rely on DTT for their primary television services.
Support provided to households
at800 has stated that it will not undertake a massive advertisement campaign, as had been done as part of digital switchover, so as not to be alarmist. Instead, its communications efforts will be targeted to those most likely to be impacted including viewers, housing associations, retailers, and manufacturers.
Specifically, information postcards will be sent to households between 12 and 3 weeks prior to the launch of the 4G services in their area. The trial is also determining the best way to make filters available to homes, whether to pro-actively send them to households located in areas of potential interference or to wait for viewers to contact the at800 call center. Households with a rooftop aerial amplifier used to boost the DTT signal can request to have an installer fit an outdoor filter. In cases where it is not possible to restore DTT services, at800 will provide support in helping households switch to another service such as free-to-view satellite. Property managers will be sent appropriate filters for communal antennas used by 5 or more households.
at800 has set aside £20 million of its funding to provide additional support to vulnerable segments of the population. Those aged 75 years or older, registered as disabled, blind, or living in a care home can receive home visits from local volunteer and community organizations to help fit filters and address any issues with DTT reception.
Extensive information is available from the at800 web portal, including guides targeting households, property managers, local authorities as well as retailers and qualified installers.
Making filters available
Different types of filters are available depending on the equipment needs of viewers. They are made available free-of-charge to all households affected by 4G interference and that use the DTT platform for their primary television services. Only one filter is available per household. While informative postcards are sent to business addresses that could potentially be affected by 4G interference, filters are not provided.
Most households will be able to use filters that resolve interference on frequency channel 59 and below. However, some households will need more selective filters that can resolve interference on channel 60. Weatherproof filters are available for viewers with rooftop amplifiers.
Since 18 March, DTG Testing has provided testing for filters to ensure that they meet the specification developed by at800. Approved filters are branded with the at800 logo. Currently, filters are made available from Filtronic, Link Microtek, Philex, Radio Design, Televes, Triax and Vision.
at800 has successfully taken a pro-active approach in helping viewers that could potential face problems with their DTT reception as the result of the launch of 4G services in the 800 MHz band. During its trials, at800 has sent postcards and in some cases free filters to numerous households that could potentially encounter DTT reception problems. And initial trial results suggest that fewer DTT households may be impacted by 4G services than had been initially estimated.
However, it will not be until 4G services are fully launched by all telecom operators that it will be possible to comprehensively measure interference problems caused to DTT reception. Ironically, current trials have shown that tests conducted in the 'fully loaded' mode, when all available spectrum is in use by 4G services to mobile terminals, have caused fewer problems to DTT reception compared to tests conducted in the 'idle' mode when there is no traffic but the base station is scanning for active mobile devices.
And, regardless of how 4G services operating in the 800 MHz band affect the DTT platform, the future discussions on the allocation of the 700 MHz band to further telecom services will be impacted.
Source: Natalie Mouyal, on behalf of the DigiTAG Project Office
DigiTAG is an association of stakeholders in the digital terrestrial TV industry and has members from broadcasting, network operators, regulatory, and professional equipment and consumer electronics manufacturing organisations throughout the world. DigiTAG has recently re-launched with new Statutes and the mission of defending and promoting digital terrestrial television on a worldwide basis, and, notably, will work tirelessly to protect spectrum for broadcasting, regardless of the technical standard used on the DTT platform.
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