Satellite Communication Satellite Communication Lecture 6 Direct to Home Satellite Television Broadcasting by xiuliliaofz

VIEWS: 401 PAGES: 35

									Satellite Communication
                     Lecture 6

     Direct-to-Home Satellite Television
         Broadcasting and S-DARS
   Introduction
   DTH Systems
    •   DTH Systems Architecture
    •   Basic Elements of DTH System and Signal Flow
    •   Compression System Arrangement
    •   DTH Considerations
    •   DTH Systems around the world
    •   DTH Service Satellites
   Satellite Digital Audio Radio Service
    •   Satellite Radio Broadcast Concept
    •   S-DARS Architecture
    •   WorldSpace
    •   Sirius Satellite Radio
    •   XM Satellite Radio
    •   Issues and Opportunities related to S-DARS
   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.)
   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
    • 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
   Experience with DTH systems has shown
    that the service must be attractive as
    compared to other forms of video
   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
   We briefly summarize the overall
    architecture of a DTH program delivery
    system such as that used for commercial
   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
   The major elements of DTH system are
    listed as follows as indicated in Figure 6.1:
    • DTH satellites in GEO (one or more):
          Spacecraft construction;
          Launch services;
          Launch and on-orbit insurance.
    • TT&C:
          Controls the space segment and monitors spacecraft
          Verifies that transmissions to satellite do not cause
          Provided by satellite operator (usually a separate
          Limited communication required between DTH network
           operator and satellite operator.
Basic Elements of DTH System and
           Signal Flow
 • Broadcast center:
      Originates, acquires, and transmits program
      Generally centralized, with no or limited
      Part of conditional access system.
 • Customer service:
      Billing and customer turn-on-off;
      Customer assistance.
Basic Elements of DTH System and
           Signal Flow
   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
   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
   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
   The basic arrangement of the uplink
    chain and downlink demodulation-
    decoding-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
   The uplink compression elements are
    contained within the broadcast center Earth
    station such as that shown in Figure 6.5 for
   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
   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.
   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
   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
           DTH Considerations
   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
   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
   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
   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
   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
   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
   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 S-
    DARS 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
S-DARS Architecture
         S-DARS Architecture
   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 was founded in 1990 and represents an
    interesting startup venture in the commercial satellite
   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
   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
   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
   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
   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
   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
   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
    Issues and Opportunities related to
   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.
   ????

To top