In June, the United Kingdom’s broadcast regulator Ofcom gave the
go-ahead for a series of 10 public trials of low-cost, small-scale, DAB across
small-scale DAB prototype system is under test at Ofcom’s
monitoring station. Photo by Lawrie Hallett
will carry a range of community-based services and commercial stations, initially
for a period of nine months, operating through into early 2016.
For some time
now Ofcom has been exploring new ways of delivering DAB services in a form that
would be more cost-effective for small-scale broadcasters. Existing multiplexes
in the U.K. are typically owned by a third-party technical service operator,
which provides transmission facilities on a for-profit basis to individual
broadcast stations and radio groups.
out technical support to a third party in this way has its advantages, but
inevitably comes at an added cost for the broadcaster. Even when scaled down
for reduced geographical coverage, this traditional approach is still
considered by many operators to be too high for their smaller scale commercial
or community-based, not-for-profit, operations.
a software radio-based approach, building on previous work by organizations
such as Open Digital Radio and the European Broadcasting Union, Ofcom first
trialled a single transmitter software-based DAB system, in Brighton, during
these earlier tests proved that the basic system could work reliably, there
were elements of the prototype system that required more work in order to meet
the operational requirements of professional broadcasting. Since then
considerable technical improvements have been made, for example in the area of
single-frequency network operations, using multiple transmitters at diverse
locations to enhance coverage.
Taking such a
software-based approach has resulted in the capital costs of DAB installations
being dramatically lower than was previously the case when using traditional bespoke
hardware implementations. Typical costs of a software-based multiplexer,
transmitter, filters and antenna for a simple single-site installation are now estimated
to total only around £6,000 (under US$10,000).
is evaluating low-cost approaches to DAB delivery on a time limited basis, even
with such minimal capital outlays being required, the regulator felt it
uneconomically viable to ask potential operators to invest in equipment that
might only be used for a brief period of time.
to the fact that the proposals for these trials fit neatly with government
objectives to promote the uptake of digital broadcasting technologies, most of
the capital infrastructure costs for these trials have been covered by the
Department of Culture Media and Sport, the U.K. government’s ministry
responsible for broadcasting policy.
2014, Ofcom first proposed additional trials of small-scale DAB, the intention
was that these would take place at only three locations. The increase to 10 came
as the result of industry pressure in response to a consultation by the regulator.
the number of trial installations not only allows the regulator to gain more
real-world experience of the operations of software-based DAB transmission
systems, but it also provides opportunities to test more complex operations
such as SFN systems and on-channel repeaters.
As well as
the various single transmitter systems being used, the trials operated by U-DAB
in London and Scrimshaw’s Information Directories in Glasgow will both
broadcast via a two transmitter SFN.
Cambridge, the trial operated by UK Radio Developments (UKRD) will employ an
on-channel repeater to fill specific gaps in predicted coverage from the main
developments aside, Ofcom has also been considering longer-term approaches to
licensing a new smaller tier of DAB services. Part of the reason for running a
diverse range of trials is therefore to explore alternative operating
structures and financial models.
For example, local
community radio service, Angel Radio is operating the trial in Portsmouth
(Hampshire). Conversely, small-scale commercial radio operator, Brighton and
Hove Radio is managing the tests along the coast in Brighton (Sussex).
separate not-for-profit company (Future Digital Norfolk), set up specifically
to operate small-scale DAB facilities in the East of England trials in Norwich
(Norfolk), is managing tests in that city.
justification for completing these trials is the degree to which demand for
small-scale broadcasting opportunities continues to outstrip supply. With
analog (FM) spectrum now filled to capacity in most urban and suburban
locations across the U.K., small-scale DAB offers the potential to help redress
the balance, by improving supply-side capacity.
Ofcom, “If the trials are successful, U.K. listeners could benefit from
hundreds more local and community radio stations on digital radio in the future.”
Across the 10
DAB trials, some 60 individual radio services are to be broadcast. This means
an average of six services per multiplex, an occupancy rate notably below the
average number of services carried on the majority of established
the national BBC multiplex typically carries between nine and 12 services,
(depending on programming demands). The lower number of services carried
provides opportunities for broadcasts at higher bit rates, improving audio
quality as a result.
“Because we’re a
not-for-profit company, using low bit rates to squeeze in as many services as
possible is not our objective,” said Mike Stonard, Future Digital Norfolk’s
managing director. “We believe that listeners appreciate high-quality audio.
All of our permanent services will typically operate at between 128 and 192 kbps.”
licences mid-June and gave operators a maximum of 12 weeks to launch their
respective trial services. Installations were carried out by individual licence
holders, typically with the aid of third-party engineering support and input
from Ofcom engineers.
Each of the
multiplex operators reports to Ofcom on a regular basis and the regulator is
also running a series of its own independent technical compliance checks, for
example to ensure that reception of existing DAB services is not impacted by
receiver overload or ACI (adjacent channel interference) close to any of the
new transmission sites.
expected to make a decision on how best to move forward with long-term
small-scale DAB licensing after the trials are completed in 2016.
Lawrie Hallett reports
on the industry for Radio World from Norfolk, England.