Transcript Satellite Communication

Satellite Communication
Lecture 6
Direct-to-Home Satellite Television
Broadcasting and S-DARS
http://web.uettaxila.edu.pk/CMS/teSCms/
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Introduction
DTH Systems
Overview
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DTH Systems Architecture
Basic Elements of DTH System and Signal Flow
Compression System Arrangement
DTH Considerations
DTH Systems around the world
DTH Service Satellites
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Satellite Radio Broadcast Concept
S-DARS Architecture
WorldSpace
Sirius Satellite Radio
XM Satellite Radio
Issues and Opportunities related to S-DARS
Satellite Digital Audio Radio Service
Introduction
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DTH systems are designed to transmit
entertainment TV programming to home-receiving
Earth terminals (or, simply, home receivers).
This is a natural extension of TV distribution by
satellite, utilizing the area-coverage and single
service provider features of the technology.
DTH systems, also called Direct Broadcast
Satellite, employ either the BSS allocations, which
are intended for this use, or the FSS allocations as
one of a number of possible applications.
This choice has some important implications, yet
the end result is the same to the user
Introduction (contd.)
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We focus on the nature of DTH services and the various
factors that must be addressed to assure a successful
introduction of these services:
• The programming mix, for example, the quantity, variety,
language options, and degree of interactivity, must compete
with other DTH systems and delivery mechanisms (e.g., cable
TV, AM and FM radio, audio CDs, Internet delivered MP3 files,
cassette and DVD rental);
• Receiving equipment - its affordability, convenience of
installation and use, integration with other video and audio
devices, and aesthetics;
• Acceptability of the service price and an effective means to
collect payment;
• Incompatibilities with the other DTH, radio, and cable TV
systems, which are dependent on the nature of the business
plan;
• Conditional access and scrambling in order to deal with
copyrights, privacy, collection, regulations, and content rules
(which may exist in the country markets of interest);
• Uplinking system, including redundancy, strength, program
development and contribution facilities.
DTH Systems
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Experience with DTH systems has shown
that the service must be attractive as
compared to other forms of video
distribution;
and access to the programming by the
consumer must be properly controlled.
The competition between delivery media is
highly variable between countries. e.g.
there is more intense competition in US
while much lesser in UK and Japan
The major elements of a DTH system are
shown in Figure 6.1.
DTH Systems Architecture
DTH System Architecture
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We briefly summarize the overall
architecture of a DTH program delivery
system such as that used for commercial
purposes.
It encompasses the uplink systems for
digitizing, compressing, and transmitting
multiple television programs using the
DVB-S standard, for example.
Other elements are required for the
contribution of the programs, storage and
switching of video signals, and the
management of DTH as a customer service.
Basic Elements of DTH System and
Signal Flow
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The major elements of DTH system are
listed as follows as indicated in Figure 6.1:
• DTH satellites in GEO (one or more):
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Spacecraft construction;
Launch services;
Launch and on-orbit insurance.
• TT&C:
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Controls the space segment and monitors spacecraft
health;
Verifies that transmissions to satellite do not cause
interference;
Provided by satellite operator (usually a separate
company);
Limited communication required between DTH network
operator and satellite operator.
Basic Elements of DTH System and
Signal Flow
• Broadcast center:
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Originates, acquires, and transmits program
material;
Generally centralized, with no or limited
backup;
Part of conditional access system.
• Customer service:
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Billing and customer turn-on-off;
Customer assistance.
Basic Elements of DTH System and
Signal Flow
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These are the major elements, and there
are many vital components and functions
hidden within each.
For example, customer service is involved
with connecting and controlling individual
subscribers.
However, how they obtain their equipment
in the first place and have it installed has
turned into an industry all its own.
Ownership and operation of the satellites
can be internal or taken as a service from a
professional satellite operator.
Basic Elements of DTH System and
Signal Flow
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A more detailed configuration of the operating
components is presented in Figure 6.3.
At the top of the diagram we find the service
management functions of the network.
These manage the interaction with the customer
over the telephone and Internet, and provide the
means to download PPV movie selections on a
monthly basis.
It also ties into the CA segment, which authorizes
individual IRDs over the space segment.
The technical functions at the bottom of the
diagram show the physical production and
transmission facilities, from content input through
baseband processing and on up to the satellite.
Basic Elements of DTH System and
Signal Flow
Basic Elements of DTH System and
Signal Flow
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The basic arrangement of the uplink
compression-encoding-modulation
chain and downlink demodulationdecoding-decompression chain is
presented in Figure 6.4.
Basic Elements of DTH System and Signal
Flow: Compression System Arrangement
Basic Elements of DTH System and Signal
Flow: Compression System Arrangement
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The uplink compression elements are
contained within the broadcast center Earth
station such as that shown in Figure 6.5 for
DIRECTV.
This includes equipment that digitizes and
time division multiplexes the video, audio,
and data information.
In large networks, between 5 and 12 video
channels and their associated audio and
data are combined using TDM onto a single
carrier that would occupy the entire
transponder bandwidth.
Basic Elements of DTH System and
Signal Flow
Basic Elements of DTH System and Signal
Flow: Compression System Arrangement
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The compression systems themselves
fall into two categories:
• (1) those that comply with a standard,
particularly MPEG 2 or DVB-S (which
includes MPEG 2 as a component); or
• (2) those that use a proprietary
algorithm and multiplexing scheme.
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Systems that started out in category
(2) are quickly moving to MPEG 2
because of the rapidly decreasing cost
of the receiving equipment.
DTH Considerations
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DTH is a delivery vehicle for
programming, where the receiver is
located with and probably owned by
the end user.
In the ideal case, specifics like the
type of receiver, size of antenna,
signal format, and satellite design are
secondary.
DTH Considerations
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The emphasis should be on making it easy
and relatively inexpensive for the
subscriber, since their interest is in the
programming and the cost of getting
access to it.
The quality of satellite-delivered digital
video is as good as or superior to cable or
over-the-air broadcasting; hence, the
picture quality will probably not be a
differentiating factor.
DTH Considerations
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The area where quality is seen as a
negative is at C-band where users have to
contend with terrestrial interference.
Ku-band systems, while generally free from
terrestrial interference, are subject to rain
fade, which produces occasional outages.
Once this problem is solved through
adequate link design and margin,
subscribers will next be drawn by a
desirable array of programming.
DTH Considerations
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The Asian environment has many opportunities
because of the primitive nature of the DTH
industry in the region.
Cable TV is a viable business in developed
countries and city-states; China, India, and
Indonesia have large populations that are hungry
for more and better entertainment.
China now has a DTH platform operating on
Sinosat.
Importantly, money flows easily into major
projects and business ventures.
This has fueled the creation of several new
satellite operators and the development of the
largest satellite market in the world.
DTH Systems around the world
DTH Service Satellites
Satellite Digital Audio Radio Service
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S-DARS systems deliver a multiplexed
combination of several audio program
channels transmitted directly to automobile
receivers, portable radios, and homes using
special frequency allocations in the region
of L- and S-bands.
S-DARS overcomes the range limitation of
terrestrial FM radio broadcasting and
provides quality of sound comparable to
other digital formats such as MP3 and
possibly CD.
Satellite Digital Audio Radio Service
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Satellites have been used to deliver audio programming for
decades, but these systems were directed toward fixed
installations at radio stations and commercial buildings.
Additionally, DTH systems typically include a package of
music channels that can be played through the TV set.
What sets the new S-DARS apart is that it provides coverage
to automobiles and portable radios, and offers some unique
program formats not popular enough to sustain themselves
as commercial operations.
Thus, we have a new generation of direct broadcasting
services to provide universal coverage of radio-like services
to the general public.
Begun in Africa as a free, advertiser-supported service by
WorldSpace, S-DARS has been propelled into a potentially
major satellite business for subscribers who are willing to pay
a monthly fee (e.g., pay radio) akin to what is already
standard for cable and DTH TV (e.g., pay TV).
Satellite Radio Broadcast Concept
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Satellite radio broadcasting is not so different from TV
program distribution and in fact shares many of the same
principles and components.
First use of dedicated satellite audio was by Muzak, a
company that delivered elevator music in the 1970s and
moved from tape to satellite.
Subsequently, all DTH TV operators included digital versions
of such service as part of their programming content through
the facilities of Music Choice.
Another form was the private radio broadcast to chains of
retail stores, pioneered by Supermarket Radio Network.
But it was not until Noah Samara created WorldSpace that SDARS really got its start.
The concept is indicated in Figure 7.1, where a broadcast
center obtains audio content from a variety of sources: tape,
local studio, audio CD, and existing radio stations and
networks.
S-DARS Architecture
S-DARS Architecture
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The actual broadcast transmission is
fairly standard, as in TV, using
analog-to-digital conversion,
compression appropriate to the
content, forward error correction,
modulation, and RF amplification.
The satellite to be used may be a
bent-pipe design with sufficient EIRP
to allow the use of portable or
vehicular receivers.
First Introduction of S-DARS—
WorldSpace
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WorldSpace was founded in 1990 and represents an
interesting startup venture in the commercial satellite
industry.
Initial financial support made it possible for WorldSpace to
build and launch satellites under contracts placed with Alcatel
and other major companies.
The WorldSpace system was the first S-DARS system and
therefore was the innovator in applying L-band spectrum to
audio broadcasting.
Of critical importance are the size of the coverage areas in
relation to the cost of the satellites, advanced low bit rate
audio coding, and simple satellite uplinking arrangements.
However, WorldSpace is less suitable for mobile reception
than XM or Sirius because of low elevation angles in some
areas served.
Without any form of diversity, signal fades and dropouts
make reception extremely problematic in moving vehicles.
Sirius Satellite Radio
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Sirius Satellite Radio is a commercial radio broadcasting
company, publicly traded and headquartered in the heart of
New York City.
Both Sirius and XM provide a programming package within a
total of about 5 Mbps comprising 100 total audio channels,
half of which are music formats and half of which are talk
radio.
Using advanced digital recording systems, the music may be
assembled off-line for later playback and without advertising.
The talk formats include standard services like Fox News
Channel and CNN along with a variety of shows to appeal
across a spectrum of interests.
Talk channels that are taken from existing program sources
may include advertising.
Sirius has assembled a large suite of studios and editing
facilities in New York to allow them to originate a substantial
number of the audio channels.
XM Satellite Radio
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XM Satellite Radio was first to market in the United States,
providing a comparable programming package to Sirius but
using the standard GEO satellite approach.
The two high-power Boeing 702 S-DARS satellites, named
Rock and Roll, were launched on March 18, 2001, and May 8,
2001, by Boeing.
Positioned at 115º W and 85º W, respectively, Rock and Roll
each transmit two carriers (total of four for the system) that
contain half of the channels each.
Due to elevation angle constraints of using GEO, there are a
multitude of terrestrial repeaters throughout the United
States.
Unlike Sirius, delivery of the broadcast channels to the
repeaters is accomplished using the X-band downlink from
Rock and Roll.
The exact same content is transmitted three times in three
different signals: once on each of two satellites and a third
time by repeaters.
Issues and Opportunities related to
S-DARS
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Satellite-based S-DARS has many advantages in
the market, some of which are apparent and some
of which are underlying.
From a practical perspective, services like XM and
Sirius offer more audio programming options than
one can possibly receive by AM/FM radio at any
given time.
Coupled with this is the added feature that the
same channel complement is available throughout
the country according to a constant name and
number assignment.
Audio quality is comparable to clear FM reception
and the radios have the added feature of
displaying the channel number and specific piece
being played.
Perhaps the biggest issue in front of S-DARS is
that a subscription fee seems to be needed to
offset the costs of operation and programming.
Issues and Opportunities related to
S-DARS
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There are risks in this market, as
many such projects failed.
Becoming a mainstream service taken
by millions of paying subscribers is
still only an expectation at best or
dream at worst.
Today, there are about 20 million DTH
Service subscribers in the United
States.
Issues and Opportunities related to
S-DARS
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The true potential of S-DARS lies in the need to change the
attitude of the radio listener, who is now accustomed to free
service (supported through a continuous stream of
advertising or requests for donations).
Being able to get the specific channels that interest you,
possibly without commercial interruption, represents a new
kind of market that at times seems a luxury.
Consider, for example, that people in the United States are
willing to pay more for bottled water than for gasoline.
The nominal $10 per month charge for S-DARS would not set
many people back and in fact is well below the threshold of
$50 one associates with “new” services like DSL and the
pricey subscription packages on DTH.
If equipment costs are to be reduced to around $100 (or
provided nearly free as an already installed feature in new
automobiles), the subscriber take-up would accelerate.
Q&A
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