Internet Protocol TV: an alternative to cable TV, DTH
Internet Protocol television facilitates real time
access and dynamic streaming
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Services offered in broadcast, on demand modes
The backbone network must carry many channels
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Present day customers may be happy if they are offered
their favourite TV channels in the drawing room
through a telephone cable which is already giving
many other services like internet browsing, voice call
etc.
It has become a reality now. Internet Protocol TV by
the telephone service provider on the land line is an
alternative to cable TV and DTH.
Enhancing quality
Advanced compression techniques like H.264 or MPEG-4
or Windows Media VC1 are used in IPTV to enhance the
quality in delivery and more importantly to pump
in high capacity in a smaller bandwidth home access
links.
IPTV is almost similar to cable TV service,
differentiated only on the payment part as we need to
pay only for viewing time, but also in providing
versatility
in service.
IPTV facilitates real time access and dynamic
streaming. Services are offered in two different modes
broadcast mode and on demand mode.
In broadcast mode, Electronic Programme Guide (EPG )
enables the required TV channel to be selected for
viewing and account processing is done for charging
on the basis of pay per view concept.
On demand type offers include interactive video on
demand, time shifted TV channel viewing, music
downloads, music on demand, games on demand and
interactive
gaming.
The functional components for the operation of IPTV
include: content sources; service nodes; IP networks
or backbone network; access network v. customers
premises equipment (CPE ); client server software. Set
top box (STB) is an intelligent device loaded with
client software used to deliver IP based contents
to the end user either for streaming of TV channels or
for web based browsing.
Picture-in-picture
STB is a programmable device and it supports Video
Codec, MPEG-2, MPEG-4 and Audio Codec. It also
supports unicast, multicast and simultaneous streaming
of two channels to be shown as picture-in-picture.
The IPTV backbone network is required to be of high
capacity to carry a number of SDTV channels, HDTV
channels VOD channels and games on demand channels.
As one SDTV requires roughly 4 MB and HDTV 20 MB, just
for 100 SDTV channels and 20 HDTV channels bandwidth
required is 800 MB.
In the case of subscriber home access link it has been
found that 18 MB bandwidth is enough to cater for 2
SDTV or 1 HDTV besides 2 MB for voice and internet
browsing. Copper loops of up to 3,000 feet length and
one ADSL 2+ link provide the bandwidth.
The TV signals received by dish antenna are fed to the
Integrated Receiver Decoder (IRD), which converts the
RF signals into digital form and its output
in MPEG-2 format is sent to a splitter, which
distributes the digital stream through to an encoder.
Compressed video
The encoder output is compressed video using MPEG-4
format. The output is then fed to DSLAM equipment in
the telephone exchanges.
The MPEG-4 stream in the form of multicast group
continuously flows into the BRAS. BRAS is a
continuously generating general membership query to
all hosts.
As soon as a viewer starts his STB and selects a
particular channel, the STB generates a request for a
particular channel to BRAS (broadband remote access
server) and places a membership report to BRAS. BRAS
will place that specific host in a multicast group,
and start forwarding the replicated copies of
the stream to that specific host.
Cost-effective, efficient
Sun Microsystems India and Tech Mahendra entered into
partnership for roll out of cost-effective and
efficient IPTV services in India and Asia-pacific
region.
Bharti Airtels test runs have been successful and
opening of service is expected this year. BSNL is
launching IPTV services in Chennai, Hyderabad and
Bangalore soon.
A. GANESAN
Former DGM, BSNL Chennai
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