Providing more efficiency on DTT


Industry organisation SADIBA has been at the forefront in examining the digital
technologies required for South Africa’s migration from analogue broadcasting to
digital terrestrial television (DTT).

Speaking at the recent Commonwealth Telecommunications Organisation (CTO)
Digital Broadcasting Switchover Forum in Johannesburg chair of the Southern African
Digital Broadcasting Association (SADIBA) Lynn Mansfield noted that when a country
migrates to DTT, its existing analogue network has to be replicated in digital form.

Mansfield continued: “Public service broadcaster SABC is on the VHF spectrum and
there is enough spectrum in South Africa to accommodate two national DTT
multiplexes to replicate SABC’s coverage. Free-to-air (FTA) commercial channel
is on the UHF spectrum which is more complicated to replicate. So, in the planning
stage of DTT you need to ensure that everyone who has an analogue signal will
receive the digital signal once migration is complete.

“The main driver for migration is a requirement for greater spectrum efficiency.
Government has adopted the European DTT transmission standard DVB-T2 and we’ve
been able to test up to 20 standard definition (SD) services on a single frequency
network (SFN).’

He noted that the digital dividend (the term applied to the analogue spectrum that
will be freed up once migration is complete) is a “thorny issue’ as broadcasters and
telcos will both want it assigned to them.

“Each country in the Southern African Development Community (SADC) region should
plan for the specific DTT outcome they want. The message they need to send out to
consumers is that DTT will result in better sound and images, especially in areas
where people suffer from multi-paths. With DTT the picture is free from interference.
Unfortunately most broadcasters in Africa don’t have the finance to go from one
analogue channel to 18 digital channels,’ explained Mansfield.

The steps in DTT migration are: transmission network roll out; set top boxes (STBs –
specs, manufacturing, distribution, retail, installation and after sales service); dual
illumination (where analogue and digital signals are broadcast during DTT phased roll-
out); consumer uptake of STBs; analogue switch-off; digital dividend allocated by
regulator; and post migration consumer support.

In South Africa the process of finalising the STB specs has been long and arduous
and, at the time of writing, still ongoing. Meanwhile the International
Telecommunications Union (ITU) has set the deadline for Africa’s analogue switch-off
for 2015.

Mansfield elaborated: “If you read the ITU recommendation it says that some
countries won’t be ready by then. After 2015 the analogue signal will no longer be
protected by the ITU and will suffer interference from digital signals.

“Many African countries use Grade C coverage which is marginal at best. In South
Africa we basically work with Grade B but once analogue is switched off you can’t
ignore the Grade C viewers. SADIBA’s work on antennas has revealed that the
segment of the country that sits outside the footprint will need new antennas in
the UHF band. A good antenna and installation will cost as much as an STB and
people will need help with installation.’

DTT implementation planning means: network coverage (transmission standard
implementation); public awareness campaign; compelling content offering; compelling
receiver solutions (an STB standard is required to protect consumer’s investment);
receiver acquisition (retail – STBs need to go through conformance phase before
going on sale); and receiver installation (DIY information, availability of STBs and
installation support).

Early planning for DTT is essential as it took the UK 14 years from the start of DTT
planning to analogue switch-off, while Italy took nine years and Spain 10.

By Joanna Sterkowicz

Screen Africa magazine – May 2012


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