Digital terrestrial television in the United Kingdom

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Digital terrestrial television in the United Kingdom is made up of over fifty primarily free-to-air television channels (including all six non-RSL analogue stations) and over twenty radio channels - primarily from the Freeview branded and Top Up TV services. It is intended that digital terrestrial television will completely replace analogue television in the UK by 2012.

Contents

[edit] Receiving digital terrestrial television in the UK

To receive digital terrestrial television in the UK, a viewer needs a set-top box (prices start at under £30) or an integrated digital television (IDTV). Some set-top boxes are also personal video recorders, allowing viewers to record programmes from digital terrestrial television onto a hard disk.

All services apart from the Top Up TV channels are available for free to everyone with the ability to receive them (though not all services may be available to those with poor reception). The free channels are generally collectively referred to as Freeview, even though not all of them are technically part of the service.

[edit] Features

Digital terrestrial television provides many more channels than analogue television. For many viewers it offers a higher-quality picture (with many channels broadcasting in 16:9 anamorphic widescreen). A number of interactive services, including a newer version of Teletext, are also offered.

An eight-day electronic programme guide (EPG) allows viewers to see the names, descriptions and broadcast times for programmes. As this was not an original feature of digital terrestrial television (it was introduced in 2004), some receivers feature an EPG with details of the current and next programme only.

A third-party proprietary 14-day EPG is also provided by a company called 4TV, who formerly carried a 7-day service when only now and next data was normal. This is only available on boxes which support their format and pay a licence fee, generally resulting in more expensive boxes. The service is carried on Multiplex D, meaning that not all viewers can even receive the data.

[edit] History

[edit] Development and launch

Digital terrestrial television launched in the UK on 15 November 1998 (just after digital satellite television on 1 October 1998). The technology required that the UK government license the broadcast of channels in six groups, or multiplex (usually abbreviated to 'mux') labelled 1, 2, A, B, C, and D[1]. Each multiplex is an error-protected bitstream of 18 or 24 megabits per second, which can be used for almost any combination of digitally-represented video, audio and data. The DVB-T standard provides a multiplex service that can make trade-offs between the number of services and the picture and audio subjective quality.

The Independent Television Commission (ITC) allocated each existing analogue terrestrial channel half the capacity a multiplex each. This meant the BBC got a multiplex to themselves (Multiplex 1), ITV and Channel 4 shared Multiplex 2 (though 10% of the capacity was given to Teletext Limited) and Five and S4C shared Multiplex A. The remaining space (Muliplexes B, C and D) was then auctioned off. A consortium made up of Granada and Carlton (members of the ITV network, which have now merged to form ITV plc) and BSkyB successfully bid for these licences, and set-up the subscription ONdigital service, (though BSkyB left the consortium prior to launch).

The BBC made some use of its multiplex for three of its then four new television services; BBC Choice (which had started on 23 September 1998 with four national variations), BBC News 24 and BBC Parliament (albeit in sound only). ITV initially used their space to house ITV2 (from 7 December 1998) in England and Wales, You2 (later UTV2) in Northern Ireland and S2 in Scotland (now both ITV2), as well as GMTV2 during the early mornings. Channel 4 used their space for subscription channels FilmFour and E4, which though not technically part of ONdigital would be paid for, and were only available through, an ONdigital subscription. It is also worth pointing out that Channel 4's nation-wide coverage on 'mux' 2 enabled it to be received terrestrially throughout Wales for the first time in its history, where previously only S4C had been available. Consequently, S4C's digital service, 'S4C Digidol' carries only Welsh-language programming, in contrast to S4C analogue which also carries English-language programmes commissioned and aired by Channel 4 in other parts of the UK.

Five sold its half of Multiplex A to S4C (who owned the other half of the multiplex) who set up a subsidiary called S4C Digital Networks (SDN) to manage the multiplex and rented most of it out to ONdigital as well as some space to the BBC who launched BBC Knowledge (1 June 1999) - at a time when technical capabilities limited the number of stations it could carry on its own multiplex. S4C chose not to carry S4C Digidol and its newly launched digital Welsh Parliament station, S4C2 outside of Wales, preferring to sell the space instead. Consequently some ONdigital services were not available on Welsh transmitters.

Whilst the BBC was addressing quality of service issues, other broadcasters valued quantity (hence choice) of channels over service reliability and picture quality.[2]

[edit] ITV Digital

Main article: ITV Digital

ONdigital suffered from the start and even renaming the service ITV Digital on 11 July 2001 could not save it. All subscription services except E4 and FilmFour went off-air on 1 May 2002 after the consortium collapsed, the reason given being overpaying for the television rights for The Football League. However, the choice of 64QAM broadcast mode, 40%+ of aerials needing replacing, a high churn rate, awful point of sale marketing, no technical support for customers, a recently cracked hackable encryption system, the cost of having to provide set-top boxes for free and aggressive competition from BSkyB added to ITV digital's spiralling costs.

[edit] Freeview

Main article: Freeview

As ITV Digital had collapsed, the rights reverted to the regulator and the ITC invited bids for the space on Multiplexes B, C and D. The Freeview consortium was formed by the BBC, transmitter company National Grid Wireless (known at the time as Crown Castle UK) and BSkyB. This consortium won and launched a new service. Junking the ITV Digital failed business model, Freeview launched on 30 October 2002 with just free television channels, and made digital radio stations available on the platform for the first time. The new service operated with the BBC acquiring control of one Multiplex (B) for its own services and Crown Castle/National Grid the other two (C & D) for commercial services, though the Community Channel also operates on Multiplex B. The BBC's second multiplex has allowed it to provide BBC Parliament 'in-vision' where it had previously only been available in sound, allowed BBC Knowledge and its successor, BBC4 to no longer rely on renting space from SDN for coverage and allowed for special video screens in its interactive service BBCi, for use during sporting events such as Wimbledon and carrying loops of news headlines and weather, (services already provided on digital satellite)

On 11 October 2005, ITV plc and Channel 4 joined the Freeview consortium and in the same year ITV plc also bought SDN and hence full control of Multiplex A.

[edit] Top Up TV

Main article: Top Up TV

The space ITV Digital rented on other multiplexes initially became empty again, but some was rented out to allow new channels to launch. In May 2004, Top Up TV was launched to provide subscription content in unused space on Multiplexes 2 (rented by Top Up TV from Channel 4) and multiplex A, rented from Five[3]. TCM however purchased its own slot from the multiplex owner, SDN, directly throughout England, Scotland and Northern Ireland, but rents from Sit-up Ltd in Wales, timesharing with bid tv. Multiplex A is ultimately owned by ITV Plc via its SDN acquisition, however ITV only has involvement with Top Up TV channels via Five[4]. In September of the same year, Top Up TV began operating solely on Multiplex A, as Channel 4 reclaimed the bandwidth on Multiplex 2 for their own services, namely More 4, E4 and most recently Film4.

Top Up TV hours from Autumn 2006
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Top Up TV hours from Autumn 2006

In October 2006, Five launched two new free-to-air digital channels, Five Life and Five US, using capacity currently previously leased out to Top Up TV[5]. This left Top Up TV with a reduced number of video streams. Consequently the company launched Top Up TV Anytime, in November 2006. The service will rely on broadcasting overnight "downloads", which are recorded by a proprietary Top Up TV Anytime personal video recorder (PVR).

[edit] The future

On 19 April 2006, Ofcom ruled that, on request of each multiplex operator, the 'free-to-air channels only' requirement put in place at the launch of Freeview in 2002 may be lifted on Multiplex B, C and D. The effect of this ruling is that if a Mux operator requests the restriction to be lifted, their multiplex may carry pay TV services. Ofcom says that the digital television market has changed significantly since 2002. Consequently, it believes that this restriction is no longer required. Although Multiplex 2 and A have always been allowed to carry pay services, Ofcom believes that the free-to-air only restriction and the current state of DTT artificially damages the growth of pay tv on the platform.

During the consultation, 9 of the 12 responses from broadcasters were in favour of removing the restriction. These, perhaps surprisingly, included the BBC. The BBC agreed that the digital television market had changed substantially since 2002, and that Top Up TV probably couldn't afford the current cost of DTT slots anyway. The BBC suggested that the deregulation should be conditional on a number of further changes to regulation. These included that Ofcom changes the transmission mode of broadcast on all multiplexes from 16QAM to 64QAM so more services could be squeezed onto the digital terrestrial platform. However, Ofcom rejected these suggestions, saying they were outside the scope of the consultation.

Out of the three that opposed, one was Channel 4, which has been putting in place a portfolio of free-to-air channels, among them Film4 which was made free-to-air across all platforms on 23 July 2006. Channel 4 argued that the number of free channels available has been the major driving force behind the massive success of the platform - there are now more than 10 million Freeview boxes in use.

A number of broadcasters requested that their replies were kept confidential. These include ITV and BSkyB. However, it is believed that ITV opposed the plan and BSkyB supported it[6]. In addition to replies from broadcasters, there were 21 replies from individuals. Of these, 20 opposed the change.

The channels on Multiplexes B, C and D are those owned by the Freeview consortium and include the three Sky channels on the platform and the UKTV channels. However, Ofcom believes that in the short to medium term, it is unlikely existing free-to-air channels will convert to pay-tv. This is because, firstly, Multiplex B is run by the BBC, who is not expected to request the removal of the free-to-air requirement. Secondly, due to the nature of the contracts the channel broadcasters hold with multiplex operators and content providers, it is unlikely a channel will be able to change to pay TV.

[edit] List of digital terrestrial channels

Unless noted otherwise, channels may broadcast twenty-four hours a day (though not all use all of this available time)

[edit] Television channels

LCN1 Channel Notes Multiplex
1 BBC One Includes regional variations 1
2 BBC Two Includes regional variations; digital variations from analogue in Wales and Northern Ireland 1
3 ITV1 In England, Wales, Southern Scotland, the Isle of Man and the Channel Islands2 2
STV In Central and Northern Scotland2
UTV In Northern Ireland2
4 Channel 4 Except Wales 2
S4C Digidol Wales only A3
5 Five A3
6 ITV2 2
7 BBC Three Broadcasts 1900-0600 1
8 Channel 4 Wales only 2
TeleG Scotland only; broadcasts 1800-1900 A
9 BBC Four Broadcasts 1900-0600 B
10 ITV3 2
11 Sky Three C
12 UKTV History Broadcasts 0500-0100 C
13 More4 2
14 E4 2
15 ABC1 Not available in Wales; broadcasts 0600-1800 A
16 QVC Reduced hours in Wales (not broadcast 0900-1700 Tuesday-Thursday) A
17 UKTV Gold Top Up TV; broadcasts 1600-0100 A
18 The Hits D
19 UKTV Bright Ideas Broadcasts 0600-1800 D
20 Ftn Broadcasts 1800-0600 D
21 TMF D
22 Ideal World D
23 bid tv Reduced hours in Wales (only broadcasts 0600-1900) A
24 price-drop tv A
25 TCM Top Up TV; broadcasts 1900-0055 A
26 UKTV Style Top Up TV; broadcasts 1300-1600 A
27 Discovery Channel Top Up TV; broadcasts 1800-2300 A
28 ITV4 Broadcasts 1800-0600 2
29 Film4 D
30 E4+1 C
31 ITV Play D
32 Film4+1 2
33 British Eurosport Top Up TV; broadcasts 1300-1800 A
34 Setanta Sports 1 Pay-per-view service (from Top Up TV); broadcasts dependent on SPL match times 2
35 Five US A
36 Five Life Broadcasts 0500-2300 A
37 SmileTV Broadcasts 0100-0500 C
38 Top Up TV Anytime 1 Subscription service; not yet launched A
39 Top Up TV Anytime 2 Subscription service; not yet launched A
40 Top Up TV Anytime 3 Subscription service; not yet launched A
42 Discovery Real Time Top Up TV; broadcasts 0600-1200 A
43 Top Up TV Promo Not yet launched A
70 CBBC Channel Broadcasts 0600-1900 1
71 CBeebies Broadcasts 0600-1900 B
72 Cartoon Network Top Up TV; broadcasts 0900-1100 A
75 CITV Channel Broadcasts 0600-1800; not broadcast while Setanta Sports 1 is on air 2
80 BBC News 24 1
81 BBC Parliament B
82 Sky News C
83 Sky Sports News C
86 S4C2 Wales only; broadcasts 0900-1700 Tuesday-Thursday A3
87 Community Channel Broadcasts 0600-0900 B
88 Teachers' TV Broadcasts 1100-1300 A
97 Television X Top Up TV (additional subscription); broadcasts 2300-0500 A
98 Red Hot TV Pay-per-view service; placeholder (no longer broadcasting) A
501 BBC HD Trial BBC High Definition Test Channel; London only CH31
503 ITV HD Trial ITV High Definition Test Channel; London only CH27
504 Channel 4 HD Trial C4 High Definition Test Channel; London only CH27
505 Five HD Trial Five High Definition Test Channel; London only CH27
  1. Logical Channel Number
  2. ITV1 is the brand name for 12 of the 15 regional ITV Network franchises for England, Wales, southern Scotland, the Isle of Man and the Channel Islands. Each of these 12 franchises has a separate brand name used prior to local programming, see ITV1. STV is the brand name for the franchises for central and northern Scotland. UTV operates the franchise for Northern Ireland. All 15 franchises broadcast 0925-0600; GMTV operates the franchise for national breakfast television and broadcasts 0600-0925.
  3. Five, S4C and S4C2 will move to a public service multiplex at the start of digital switchover, using the bandwidth created by switching from 16QAM to 64QAM mode, so will be transmitted from all 1,154[7] UK transmitters. Multiplexes A, C and D will only be transmitted from the current 80 transmitters after switchover but with higher powered signals (and in 64QAM mode).

[edit] Text and interactive services

LCN Channel Notes Multiplex
100 Teletext Text service 2
101 Teletext Holidays Text service A; 2 in Wales
102 Teletext Cars Text service 2
103 Teletext Games Not yet launched A
104 Teletext on 4 Text service 2
105 BBCi Text service 1
107 Top Up TV Active Text/Audio service A
108 Sky Text Text service C
300 4TVInteractive EPG service; compatible set-top-box required for full functionality; broadcasts 0300-0400 D
301 BBCi Interactive service; press red button on BBC channels for full functionality B
302 BBCi Interactive service; press red button on BBC channels for full functionality; broadcasts 0900-0600 B
303 BBCi Carries data for BBC News 24, BBC Parliament and CBeebies (appears as blank screen) B
304 Tvtv digital EPG/recording service; compatible set-top-box required for full functionality (not yet launched) C
305 BBC Parliament The defunct ¼ screen service, replaced on LCN 81 by a full screen service [8] B

[edit] Radio stations

LCN Channel Notes Multiplex
700 BBC Radio 1 A
701 BBC 1Xtra B
702 BBC Radio 2 A
703 BBC Radio 3 A
704 BBC Radio 4 FM version A
705 BBC Radio Five Live B
706 BBC Five Live Sports Extra B
707 BBC 6 Music B
708 BBC 7 B
709 BBC Asian Network B
710 BBC World Service English language European version D
711 The Hits Radio D
712 Smash Hits D
713 Kiss 100 D
714 Heat A
715 Magic 105.4 D
716 Q D
717 Oneword D
718 102.2 Smooth FM D
719 BBC Radio Wales Wales only 1
BBC Radio Scotland Scotland only 1
BBC Radio Ulster Northern Ireland only 1
720 BBC Radio Cymru Wales only 1
BBC Radio nan Gaidheal Scotland only 1
BBC Radio Foyle Northern Ireland only 1
721 Mojo A
722 Kerrang! D
723 talkSPORT C
724 3C C
725 Premier Christian Radio C
726 U105 Northern Ireland only 2
727 Virgin Radio C
728 Heart Not yet launched 2
729 Radio Music Shop 2

[edit] The multiplexes

[edit] Multiplex 1

Operated by the BBC; broadcasts nationwide in 16QAM mode at 18 megabits/second

  • TV: BBC One (regional variation), BBC Two (national variation), BBC Three, CBBC Channel, BBC News 24
  • Radio: BBC Radio Wales (Wales only), BBC Radio Scotland (Scotland only), BBC Radio Ulster (Northern Ireland only), BBC Radio Cymru (Wales only), BBC Radio nan Gaidheal (Scotland only), BBC Radio Foyle (Northern Ireland Only)
  • Text/Interactive: BBCi, The Engineering Channel

[edit] Multiplex 2

Operated by Digital 3&4 (an ITV/Channel 4 consortium); broadcasts nationwide in 64QAM mode at 24 megabits/second

  • TV: ITV1 (regional service), Channel 4, ITV2, ITV3, More4, E4, ITV4, Film4+1, Setanta Sports 1*, CITV Channel
  • Radio: U105 (Northern Ireland only), Heart, Radio Music Shop
  • Text/Interactive: Teletext, Teletext Holidays (Wales only), Teletext Cars, Teletext on 4, Teletext on ITV

[edit] Multiplex A

Operated by SDN (owned by ITV plc); broadcasts nationwide in 64QAM mode at 24 megabits/second

  • TV: S4C Digidol (Wales only), Five, TeleG (Scotland only), ABC1 (except Wales), QVC, UKTV Gold*, bid tv, price-drop tv, TCM*, UKTV Style*, Discovery Channel*, British Eurosport*, Five US, Five Life, Top Up Anytime 1, Top Up Anytime 2, Top Up Anytime 3, Discovery Real Time*, Cartoon Network*, S4C2 (Wales only), Teachers' TV, Television X*
  • Radio: BBC Radio 1, BBC Radio 2, BBC Radio 3, BBC Radio 4, Mojo, Heat
  • Text/Interactive: Teletext Holidays (except Wales), Teletext Games, Top Up TV Active

[edit] Multiplex B

Operated by the BBC; broadcasts nationwide in 16QAM mode at 18 megabits/second

  • TV: BBC Four, CBeebies, BBC Parliament, Community Channel
  • Radio: BBC 1Xtra, BBC Radio Five Live, BBC Five Live Sports Extra, BBC 6 Music, BBC 7, BBC Asian Network
  • Text/Interactive: BBCi (301, 302, 303), BBC Parliament (redundant ¼ screen service), The Engineering Channel

[edit] Multiplex C

Operated by National Grid Wireless; broadcasts nationwide in 16QAM mode at 18 megabits/second

  • TV: Sky Three, UKTV History, E4+1, SmileTV, Sky News, Sky Sports News
  • Radio: talkSPORT, 3C, Premier Christian Radio, Virgin Radio
  • Text/Interactive: Sky Text, TVTV Digital

[edit] Multiplex D

Operated by National Grid Wireless; broadcasts nationwide in 16QAM mode at 18 megabits/second

  • TV: The Hits, UKTV Bright Ideas, Ftn, TMF, Ideal World, Film4, ITV Play
  • Radio: BBC World Service, The Hits Radio, Smash Hits, Kiss 100, Magic 105.4, Q, Oneword, 102.2 Smooth FM, Kerrang!
  • Text/Interactive: 4TVInteractive

* Pay TV service

[edit] Use of multiplexing technology

Some of these multiplexes carry a much larger number of services than others for various reasons. Firstly, a number of services share bandwidth — so some channels turn off when others are on (for example one will never see CBeebies and BBC Four on air at the same time, as they use the same space in Multiplex B, with CBeebies broadcasting from 6am until 7pm and BBC Four from 7pm onwards; the situation is the same for CBBC and BBC Three). In addition, some multiplexes have fewer channels so as to allocate more data to fewer services, thus ensuring higher quality (for example, BBC One on Multiplex 1 is carried as a 4.4 Megabit stream, while Sky Sports News typically uses 2 Megabits per second).

On top of this, the modulation of the multiplexes can be varied to squeeze higher digital bitrates out of the same portion of the electromagnetic spectrum. This comes at the cost of making it harder to get a good signal. There are three basic modulation schemes currently in use in the UK; in order of bandwidth efficiency, they are: QPSK (only used for tests in the Oxford and London areas), 16 QAM and 64 QAM, each with a progressively higher bitrate, at the cost of progressively higher likelihood of signal degradation. Currently multiplexes 2 and A use 64 QAM (and are consequently more prone to poor reception) while the other multiplexes all currently use 16 QAM.

Furthermore, multiplexes can make use of statistical multiplexing at the MPEG video coder whereby the bitrate allocated to a channel within the multiplex can vary dynamically depending on how difficult it is to code the picture content at that precise time, and how much demand there is for bandwidth from other channels. In this way, complex pictures with lots of detail may demand a higher bitrate at one instant and this can result in the bitrate allocated to another channel in the same multiplex being reduced if the second channel is currently transmitting pictures which are easier to code, with less fine detail. The only channel on the DTT system not to use statistical multiplexing, i.e. has a constant bit rate, is BBC One. This is so the English Regions and Nations can perform a simple transmultiplex, or T-Mux, operation and insert their local version of BBC One over the London feed straight into the existing BBC Multiplex 1 without having to re-code the entire multiplex at each regional centre, requiring specialist (and costly) equipment at several locations.

[edit] New compression technology

Better implemented compression technology has provided for two additional television stations on the National Grid Wireless multiplex using the same bandwidth, with the possibility of more to follow on this and some other multiplexes.

This technique is only suitable for the multiplexes that are identical nationwide. On Multiplex 1 where BBC One is one of 15 regional versions, and BBC Two is one of four national variants (England, Scotland, NI and BBC 2W in Wales) it has proved harder to increase the number of channels carried. The same problem applies to Multiplex 2 with its 19 ITV1 regions and six Channel 4 variations (used for advertising rather than programming).[9]

The additional capacity has been achieved by developments in statistical multiplexing that allows the broadcaster more additional channels using the same bandwidth. The two slots were made available for bidding earlier this year, and due to the limited capacity on the DTT service in the UK, broadcasters bid in millions in order to gain bandwidth. ITV won the bidding for the first slot (on which it launched Men & Motors on 2 May 2005 which has subsequently been replaced by ITV Play), and Channel 4 the second. Channel 4 launched E4 +1, as opposed to its new channel More4, on the multiplex when the slot became available on June 1 (E4 launched on Freeview on 27 May 2005). National Grid Wireless have made a new slot available on Multiplex D using the same compression techniques as above. The 18 hour channel, running from 6am to midnight, became available on 1 December 2005. Companies interested had until November 1 to submit their bids, with bids said to have reached £10 million, from a set entry bid level of £5.5 million, with 12 separate bidders covering all sectors of broadcasting. This slot was won by Channel 4; it was occupied by More4 +1 until live coverage of Big Brother replaced it on 18 May 2006. Film4 took over the slot 23 July 2006.

The latest compression technology, as now available in codecs like MPEG4, H.264 or Microsoft's WMV could in principle enable most existing programmes to be converted to high-definition, without any need for more bandwidth. However this would render obsolete all existing receivers as new decoder set-top boxes or integrated digital televisions would be required, (unless they are able to be reprogrammed for additional codecs which is widely not the case). Backwards compatibility is a common technology issue, one faced by digital terrestrials audio counterpart, DAB which has a new AAC codec option.

The BBC, who would like to broadcast high-definition television on at least some Freeview channels, is considering an alternative method utilising spare capacity at night to allow the download of high definition programmes for later replay.

[edit] Digital switchover

Areas covered by transmitters that will change frequency group and will require a new aerial to view TV after switchover
Enlarge
Areas covered by transmitters that will change frequency group and will require a new aerial to view TV after switchover
Areas covered by transmitters only carrying public service multiplexes after switchover
Enlarge
Areas covered by transmitters only carrying public service multiplexes after switchover
Ratio of homes with Freeview after switchover
Enlarge
Ratio of homes with Freeview after switchover

The British Government has given Ofcom and Digital UK the joint task of switching off the analogue signals. The switchoff will occur on an ITV sub-region basis. The first area to switch was the March 2005 trial site at Ferryside, Wales. In November 2007 the Whitehaven, Eskdale Green and Gosforth transmitters will switch off their analogue signals. In November 2008 the full rolling program will start with the Border Television Selkirk[10] region, then Caldbeck, Westcountry Television[11] Beacon Hill, Stockland Hill, Huntshaw Cross, Redruth, Caradon Hill, Wales[12] Preseli, Carmel, Granada Television[13] whole region, Wales Llanddona, Moel-Y-Parc, Blaenplwyf, Long Mountain, Wenvoe eventually finishing in the Channel TV region in 2013[14].

There remain numerous decisions to make, including how to deal with people who have no desire to receive more than the four or five channels they presently have, and those who may find the new technology confusing. Also they will be reluctant to buy a digital box in order to view the channels they have had for free for so long. The BBC has been discussing plans with the government to pay for the equipment (and replacement aerials) for the over 75s by asking for an above inflation increase in the licence fee.

Another issue is that the "98.5 per cent of the population" are only reached "via rooftop aerials"[15], however Section 134 of the Communications Act (2003) sets out the principle "that no person should unreasonably be denied access to an electronic communications network or to electronic communications services"[16]. This is taken to mean that you have the right to mount a television aerial on your roof, according to Ofcom: Digital switchover: an audit of viewers’ priorities, §6.31.

At each transmitter, three of the analogue transmission channels will be reallocated to a digital multiplex, but at a power level about 10dB less than the current analogue signals. First of all, the analogue BBC Two signal will be replaced with Multiplex 1[17]. At the same time, scrolling messages will appear on the remaining analogue channels reminding viewers of the impending switchover. One month later, the remaining channels will be switched off, with the analogue ITV1 signal being replaced with Multiplex 2, and the analogue BBC One signal with Multiplex B. At some locations, BBC One, Channel 4 or ITV1 may close first, due to the fact that the BBC Two UHF channel is being deallocated. Another possibility is that, for the last month of broadcast, that the analogue BBC Two frequency will be used for BBC One, ITV1 or Channel 4 where that channels frequency is required for the digital transmission.

It is expected that whole transmitter regions will switch together [18]. None of the multiplex operators have asked Ofcom to extend the commercial multiplexes to any of the 1,074¹ relay transmitters so these multiplex will broadcast only from the existing 80 that carry all the multiplexes after switchover. Those which don't will only broadcast multiplexes 1, 2 and B, and therefore will broadcast a cut-down service.

At switchover the transmission mode will change from 16QAM to 64QAM on Multiplexes 1 and B (Multiplex 2 is already 64QAM). This will increase the amount of bandwidth on each multiplex, and will allow Five, S4C and S4C2 to move to Multiplex B. The switch to 64QAM mode will also provide valuable extra bandwidth on Multiplexes C and D.

Alternative post-switchover multiplex designations have been used on internal documentation by the BBC switchover contractor Arqiva[19], however changing the designations of the multiplexes requires changes to legislation[20] and to the multiplex licences issued by Ofcom and is not in the current draft Ofcom - Switchover–related Changes to DTT Licences.


Three multiplexes will be for public service broadcasting and contain all the television channels from the BBC, ITV (except ITV Play), Channel 4 (except Film4 and E4+1), S4C (in Wales only) and Five (except Five Life and Five US). As noted above, these multiplexes will be available from all transmitters. The other three multiplexes will be for the existing commercial owners and will be broadcast from only the current 80 transmitters[21] at high power, increasing the national coverage from the current 73%[22] of the population to an estimated 90% by 2012. Note that the names of the multiplexes have never officially been used by Ofcom.

When digital switchover is complete, whole tracts of the UHF spectrum will be clear, leaving only channels 21-30 and 41-62 for digital television multiplexes. This "digital dividend"[23] will require millions of homes to upgrade their aerials to the wideband type to receive some or all of the Freeview multiplexes. [24] This spectrum is useful because of its tradeoff between bandwidth and range. The deallocated frequencies could be used for:

¹ At the switchover it is planned that Caldbeck will broadcast both England and Scotland muliplexes to better serve viewers north of the border and Sandale will cease to broadcast TV.

[edit] See also

[edit] External links

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