Page 30 - ITU Kaleidoscope 2016

2016 ITU Kaleidoscope Academic Conference

Production

coding

BBC iPlayer
Servers

Content Delivery
Network
Core
Network

Edge
Network
Figure 11: Emissions from video on demand.

DSLAM video & audio formats (such as 4k or HDR) were in regular use.
As audiences increase their use of these on-line platforms and use
higher quality formats, then the energy consumption will grow in
proportion. This supports the work of Professor Andrew Ellis of
Home Aston University in the UK who has suggested that in 2015 the
router internet accounted for at least 8% of the UKs power consumption
(with up to 3% of the UK power consumption being used by the
major Telcos alone) and that this was expected to double over the
TV Display next four years if current behaviors and technologies remained
unchanged. All this presents some real challenges, not only for
sustainability but for other prized concepts like Net Neutrality. It
also demonstrates the continued importance of video, in a TV type
Figure 10: A typical Video on demand distribution chain. format, for modern audiences. Consumption in these sort of
numbers seems to suggest that people are still interested in long
form story telling but what is perhaps less well understood is how
phase is where BBC programmes are encoded especially for on- they find and share this content and the importance of social
line distribution and placed on hosting servers, which form part of media in this process. A topic for another paper perhaps?
the BBC’s iPlayer and the BBC’s wider online services. The
Content Delivery Network (CDN) is made up of the servers
necessary to meet user requests for content and is partly the 4.3 Comparing DTT & On-Line
BBC’s own BIDI [BBC Internet Distribution Infrastructure] and
partly those of service providers. These CDN services carry the Figure 11 shows us how the carbon footprint of the on-line
content of a large number of content providers and are scaled to distribution is made up. Once again we can see the significant
meet peaks as demand varies across the day (with the peaks impact of a small technology component being replicated across
usually occurring at midday and late evening). From the CDN millions of households as the home router is responsible for nearly
content is delivered to the home across the internet, which for three quarters of the overall footprint, although once again you
these purposes has been divided in to three components: the core could argue that this router would be present and powered to
network and the edge or metro network sits within the telcos and deliver all the other data & telephony services the modern
the last, consisting of digital subscriber line access multiplexer household requires, but even so it probably going to need to be of
(DSLAM) used to connect via ADSL, is provided by Internet higher specification, work harder and be switched on for longer if
Service Providers (ISP). Lastly all consumers will need to power a used for serving video to the home.
home modem/router. With a better understanding of the way the broadcast and on-line
Not only is it difficult to know which components are in use for carbon footprints are made up we would now like to understand
VOD at any one time, as the whole infrastructure is shared across how the two platforms compare. If we use the metric of
a range of on-line activities and multiple users simultaneously, but CO 2 e/viewer-hour again and start with a DTT implementation
the nature, make up and technology of all these components is with good coverage where the viewer doesn’t require additional
changing continuously and relatively rapidly, especially compared UHF amplification, then the emissions are shown in figure 12. As
to the much more stable transmission infrastructure discussed we might expect the programmes with large audiences operate
earlier. This has meant that BBC R&D have had to make a range very efficiently and, with the exception of BBC Parliament, they
of assumptions to be able to develop a usable model and these are produce typically a half to a third less CO 2 e/viewer-hour.
documented in White Paper WHP 189 [10]. However if an aerial amplifier is required, as shown in figure 12,
The scale of what is happening with on-line traffic is dramatic and then this advantage is removed and the current model shows that
well described in Sandvine’s 2015 [11] report that claims that IP distribution (including the local router) is still more CO 2 e
Netflix use consumes 36.5% of all downstream Internet bandwidth efficient for certain services.
during peak periods in North America, compared with just 2.7%
for Facebook. This is serving a user base, which is only about 12%
of the US population and was calculated before higher quality

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