With IP at the heart of broadcasting’s future, codecs are increasingly the gateways of content assimilation and distribution
LONDON — The ongoing development of small-scale DAB in the United Kingdom continues apace with the first new multiplexes now operational. Others are nearing launch, and the broadcast regulator, Ofcom, is offering additional licenses through a third round of licensing that opened on Jan. 25.
The second round of licensing, which closed to applications last September, received over 30 applications for 18 geographical locations in northwest England, including the major metropolitan areas of Liverpool and Manchester. Ofcom expects to announce the successful applicants for these areas imminently.
The third round of licensing, which closed April 25, included a further 25, widely spread, geographical locations. These included, for the first time, locations in Northern Ireland (Belfast and Lisburn), Wales (Llandudno and Betws-y-Coed, as well as Swansea) and the first non-trial areas in Scotland (North Aberdeen and Dundee). Other locations spread across England include city locations such as Coventry, Leicester, Nottingham, Oxford and York. When the small-scale DAB trials started in 2015, Ofcom provided each multiplex operator with transmission equipment based on open-source software developed by Open Digital Radio. This solution has generally worked well and is continually updated.
However, it tends to require high levels of technical competence to implement and maintain, particularly if operating a single frequency network of two or more transmitters. As a result, some small-scale DAB operators are choosing not to carry out transmission-related work in-house, as has largely been the case during the trial operations of the past few years.
Instead, some opt for various commercial solutions from specialist broadcast transmission providers.
MUX ONE, the first non-trial small-scale multiplex to become operational, serves some 380,000 adults in Tynemouth and South Shields in northeast England. The multiplex operates a single frequency network employing two TX Digicast TX-DAB200 transmitters.
John Bibby is a director of both MUX ONE and TX Digicast, who previously supplied DAB power amplifiers for some of the Ofcom trial multiplexes. He explains that TX Digicast transmitters are made in the U.K. and cost less than other brands from Europe. “When all sums are done, they cost little more than the software approach used in Ofcom’s trials and also have proper broadcast modulators with pre-correction,” Bibby says. “So, we were able to launch this multiplex in total confidence and within a very reasonable budget.”
Other small-scale multiplex operators are considering a variety of technical approaches. Rashid Mustapha, the former Ofcom employee who drove the evolution of the regulator’s small-scale DAB policy, is now the U.K. representative of the Anglo-Swiss DAB service company, Digris. Recognizing that some multiplex operators may wish to delegate technical operations to a third party, Digris is offering a comprehensive installation and long-term support package at a typical cost of just under US$60.00 per service, per month, including all capital costs involved. The original trial multiplex operators — some of which will be transitioning to permanent licensed operations in the coming months — use various solutions, including those based on GatesAir and RadioScape gear. Audessence, another U.K.-based company, has been running the trial London SFN for several years and is preparing to launch new DAB-related products, later this year.
Transmission site considerations
In addition to equipment considerations, small-scale multiplex operators are also taking innovative steps in selecting transmitter sites. Because small-scale DAB operations offer low-cost broadcast capacity to community radio services and smaller commercial broadcasters, the sector is also developing a new tier of economically viable broadcast transmission sites, such as the tops of residential tower blocks and existing communication masts not previously used for radio broadcasting.
Acquiring and implementing such infrastructure can be both complex and time-consuming. Ofcom requires applicants to secure agreements in principle for the use of proposed sites. However, translating such agreements into contractual agreements is not always straightforward, particularly where site owners lack prior knowledge of broadcasting technicalities.
A good example of the practicalities of site selection is that of MUX ONE. Neither of the two transmitter sites it employs has been used for broadcasting. One is at the top of a floodlight tower at Whitley Bay football stadium.
The other is on a disused water tower at Cleadon in South Shields, but because the building is a Victorian structure with protected status under law, negotiating access and, in particular, installing the required broadcast transmission antenna, was a complex process. It required both listed building consent and the removal of a considerable amount of redundant communications infrastructure as part of the deal.
One important consideration at new transmitter sites is security, not only in terms of safety for the general public, but in reducing the risks of vandalism. Coaxial cable can have considerable scrap value, and metal thieves target unsecure communications sites.
Moreover, deliberate sabotage is an issue, as MUX ONE discovered soon after launch. At its Cleadon Water Tower site, someone severed the coaxial cable to the antenna one evening in early January. Engineers worked through the night to identify the problem and get services back on air soon after 9 a.m. the following day.
Commissioning new multiplexes
Before any new DAB operations can begin, Ofcom must approve the various parameters of the proposed transmissions and ensure that existing DAB multiplex operators are not impacted by the addition of new DAB transmissions locally.
Once Ofcom has approved the individual technical parameters, it is the responsibility of the small-scale multiplex operator to liaise with other broadcasters, typically the BBC and, in the case of commercial multiplexes, Arqiva. If any third party objects, the small-scale multiplex operator must measure before and after switch-on to ensure the coverage of other existing multiplexes is not materially degraded.
Ofcom has been proactive in assisting this process and developing an itemized commissioning procedure to make sure that the new multiplexes are compliant with wider spectrum planning considerations such as the protection of emergency frequencies.
The various elements involved in the initial rollout of this new tier of U.K. DAB broadcasting constitute a learning curve. As practical knowledge and experience grow, so should competence and capacity within the sector.
Because of the work by early licensees and Ofcom, future small-scale multiplex operators should benefit from clearer and more established routes to launch as the process of small-scale DAB continues to move ahead.
Dr. Lawrie Hallett is a senior lecturer in radio and journalism and a director of the small-scale multiplex operator, Future Digital Norfolk Limited.