Presentation on theme: "Satellite Communication"— Presentation transcript:
1 Satellite Communication Lecture 6Direct-to-Home Satellite TelevisionBroadcasting and S-DARS
2 Overview Introduction DTH Systems DTH Systems ArchitectureBasic Elements of DTH System and Signal FlowCompression System ArrangementDTH ConsiderationsDTH Systems around the worldDTH Service SatellitesSatellite Digital Audio Radio ServiceSatellite Radio Broadcast ConceptS-DARS ArchitectureWorldSpaceSirius Satellite RadioXM Satellite RadioIssues and Opportunities related to S-DARS
3 IntroductionDTH 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 userBroadcasting Satellite Service (BSS): A service in which signals transmitted or retransmitted by space stations are intended for direct reception by the general public. In the BSS, the term “direct reception” shall encompass both individual reception and community reception.Fixed Satellite Service (FSS): between Earth stations at given positions, when one or more satellites are used; the given position may be a specified fixed point or any fixed point within specified areas; in some cases this service includes satellite-to-satellite links, which may also be operated in the inter-satellite service.
4 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 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.
5 DTH SystemsExperience 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 JapanThe major elements of a DTH system are shown in Figure 6.1.
7 DTH System Architecture 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.DVB-S is the original Digital Video Broadcasting forward error coding and modulation standard for satellite television. : DVB-S is used in both MCPC and SCPC modes for broadcast network , as well as for direct broadcast satellite services like Sky Digital (UK) via Astra in Europe, Dish Network and Globecast in the U.S. and Bell TV in Canada. The transport stream delivered by DVB-S is mandated as MPEG-2. This technology uses 11/12 GHz Frequency band.
8 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 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.A Tracking, Telemetry, and Command (TT&C) ground station. 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);
9 Basic Elements of DTH System and Signal Flow Broadcast center:Originates, acquires, and transmits program material;Generally centralized, with no or limited backup;Part of conditional access system.Customer service:Billing and customer turn-on-off;Customer assistance.
10 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 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.
11 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.IRD:Integrated Receiver/Decoder:A satellite TV system receiver with a built-in decoder for unscrambling subscription channels. Serves as receiver and decoder for compressed digital TV signals.PPV: Pay per view: A system of viewing individual television programmes for an additional charge over and above that for the standard service; normally used on cable and satellite systems.CA: Conditional Access: In recent years, broadcasting and information society services (IS services) have been making ever-increasing use of conditional access devices. This trend is expected to gather pace as the market for these services develops. The conditional access device (CA) provides the user with a technical facility which allows him to determine who has access to electronically-distributed services and under which conditions. In order to improve the legal situation of providers of broadcasting and IS services, the European Commission has recently drafted and adopted a Directive on the legal protection of services based on, or consisting of, conditional access (CAD)This Directive introduces a common standard of legal protection for conditional access devices. However, it focuses exclusively on conditional access devices that serve the remuneration interest of service providers and makes no provision for CA devices that serve other interests.
13 Basic Elements of DTH System and Signal Flow The basic arrangement of the uplink compression-encoding-modulation chain and downlink demodulation- decoding-decompression chain is presented in Figure 6.4.
14 Basic Elements of DTH System and Signal Flow: Compression System Arrangement
15 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 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.
17 The compression systems themselves fall into two categories: Basic Elements of DTH System and Signal Flow: Compression System ArrangementThe 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.
18 DTH ConsiderationsDTH 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.
19 DTH ConsiderationsThe 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.
20 DTH ConsiderationsThe 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.
21 DTH ConsiderationsThe 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.
24 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.
25 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).
26 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 networks.
28 S-DARS ArchitectureThe 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.
29 First Introduction of S-DARS—WorldSpace 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.
30 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 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.
31 XM Satellite RadioXM 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.
32 Issues and Opportunities related to S-DARS 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.
33 Issues and Opportunities related to S-DARS 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.
34 Issues and Opportunities related to S-DARS 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.