An overview of Digital Radio in 2018
Britain entered the digital radio age with a system called DAB Digital Audio Broadcasting as long ago as 1995, using a technical format known as Eureka 147 on some 'Band III' frequencies vacated when 405 line TV was discontinued. After some experiments with utilisation of the much higher L band frequencies, both the format and the frequency band went on to be utilised by other early DAB adopters around the world, particularly in Europe but also in some other regions including Australia. In some parts of the world, notably the USA and parts of south America, an alternative known as HD digital radio, which operates "in band" and "on channel" alongside FM broadcasts, has been adopted rather than the DAB system.
At a technical level DAB radio operates in a "multiplex" arrangement, delivering 'bouquets' or groups of stations, available in the UK within either "national" or "local" multiplexes. Some temporary licences have also been granted in recent years for "small scale" DAB broadcasts, which have in general been well received. Whilst there is potential for high quality audio reproduction using the original DAB transmission medium, pressure for more channel allocations in the UK has led to compromises over both audio quality and stereo capability for broadcasts in most existing national and many local multiplexes.
DAB technical parameters were originally defined in the 1990's using a then widely accepted and reliable data compression technique known as MPEG2. A typical fully utilised national UK multiplex operating to the original standard might contain up to perhaps 30 stations, each with a data channel, allowing a text display on suitably equipped receivers in addition to the actual programme material. However, the more high audio quality (and stereo) stations there are, the lower the total number of stations that will fit within the available bandwidth for that particular multiplex. Conversely, as more stations are accommodated, audio quality declines, and in recent years numbers of stereo FM stations have reverted to mono DAB broadcasts.
Though Digital radio is now seeing wider acceptance and listener growth, commercial viability has in the past proven elusive, and many promising digital stations have fallen by the wayside since UK services began. Behind the scenes, with regulatory, financial and spectrum efficiency pressures leading to inclusion of as many stations as possible, resultant audio quality from DAB transmissions has been a longstanding matter of engineering and listener concern. Various other issues have had an impact on slow growth, ranging from high broadcast transmission costs to patchy or non-existent reception in buildings, poor coverage in some areas, and relatively slow network expansion. Reception limitations often directly relate to the inherent nature of digital transmission systems in general, where signal quality at a given point is determined by the receiver on a good/no good basis. Thus a signal is either present in good quality or entirely absent, with no "grey areas" in between like FM - where reception remains possible if variable and rather 'scratchy.'
Though planning for best reception is a much more complex affair than for equivalent FM coverage, the UK DAB transmitter network has expanded greatly in recent years, bringing much enhanced national and local coverage. Low signal strengths can still be a problem in buildings and some urban areas, but with many more transmitters, and a much wider choice of (relatively) modestly priced receivers now readily available, along with near-universal DAB receiver fitment in new cars, audiences are showing slow but consistent growth, and after many false starts, several digital-only stations have built up a loyal following.
British Government proposals to remove existing UK-wide network services from FM on a very tight timetable by 2015 (subject to certain DAB service criteria and listener penetration levels being met) were not carried through, and though service and audience levels are closing in on the original criteria, no alternative date has yet been suggested.
Across Europe, digital radio licensing by governments and take-up by broadcasters has been quite uneven, with individual countries progressing at their own speed and with varying levels of enthusiasm. Trials are continuing in a number of European and worldwide markets, and some have warmly embraced the potential. Norway has become the first country to go all-digital, with phased switch-off of its national FM networks, but equally there are others which have trialled DAB and decided not to continue - and yet others who have no plans, or remain undecided.
Other alternatives exist. Satellite radio, exemplified by the US SiriusXM operation, could yet come to Europe, providing a direct challenge to today's Digital Radio landscape. However, one such system, intended for launch in 2014, has already fallen by the wayside, and the way appears clear for further DAB services to develop in coming years.
Since the 1990's a newer, updated version of DAB called DAB+ has been developed, and is rapidly gaining ground as the preferred system in Europe and some other parts of the world. It uses a more efficient data compression system, known as AAC MPEG4. Depending on exact technical implementation, this offers distinct benefits in perceived audio quality and/or the actual numbers of channels broadcast in a given multiplex - or even both. There are also data transmission advantages. However introducing this newer system in countries where the earlier system is on air and long established brings inevitable problems of 'backwards compatibility.' Although dual standard receivers have become the norm in recent years, many "old" DAB receivers presently in use cannot decode newer DAB+ transmissions. Some countries - seeing the available benefits - have decided to switch to the newer standard anyway, and others, including the UK, have begun running some DAB+ services alongside existing DAB channels.
Since the launch of the British DAB service in 1995, an entirely different non-multiplex digital radio system called Digital Radio Mondiale (DRM) has been developed and introduced, for use in the long, medium and shortwave bands, at frequencies up to around 30 MHz. For technical reasons the first generation DRM system cannot be used above that approximate frequency, though experimental systems operating on DRM principles have been demonstrated using the FM band, and up to the same band III frequencies used by DAB. This system has been called DRM+, and there has been speculation that such alternative digital technology might one day entirely replace analogue FM broadcasting.
Though not without some known reception foibles, especially at night, on established AM wavebands DRM allows generally more consistent and reliable reception than conventional AM transmissions over long distances. DRM also delivers notably better audio quality than has traditionally been possible under the established international technical standards applied for many years to broadcasting in the long- medium- and short- wavebands.
International broadcasters are increasingly taking advantage of these benefits by radiating DRM services at high power on short wave, and some long and medium wave services are also operating. The most notable medium wave network to date is on-air in India, where significant numbers of high power medium wave DRM transmitters were deployed in 2016-2017, in a network intended to provide near-complete national coverage. Neighbouring Pakistan is reported to be following suit with another DRM-based service.
The advent of these new networks in the highly populated Indian sub-continent has resulted in major DRM receiver manufacturing facilities being established in the region, while car makers supplying new vehicles for these markets are beginning to initiate production-line installation of suitable receivers. These moves could eventually bring DRM receiver production to the point where export potential is available to overcome the shortage of suitable cost-effective receivers, which has heavily restricted advancement of DRM transmissions for national and local services on increasingly underutilised AM wavebands in general.
Readers should be aware that this is intended only as an overview of the general Digital Radio situation. The Digital Broadcasting transmission medium allows for a number of technical possibilities, including transmission of additional data and pictures, offering a good deal of flexible potential which in the "connected age" is beginning to be explored in a number of ways. One of the most innovative concepts so far developed is "hybrid radio." More details on this at www.radiodns.org
Various websites provide information on digital radio developments, news, product and technical information and background, DAB and DRM reception and programming information. These include:
www.ofcom.org.uk
www.getdigitalradio.com
www.radio-now.com
www.ukdigitalradio.com
www.bbc.co.uk/digitalradio
www.localdigitalradio.co.uk
www.worlddab.org
www.dab-digital-radio.com
www.wohnort.org
www.ebu.ch
www.drm.org
www.radiodns.org
Please note: Websites may be taken down at any time, and Moss Media accepts no responsibility for the existence or content of any site listed.
This is not an exhaustive list; to request that your digital radio website is added, please e-mail enquiries@mossmedia.co.uk
