DTV Datacasting Opportunities and Challenges

Nandhu Nandhakumar and Gomer Thomas Triveni Digital, Inc. Princeton Junction, NJ

Abstract significant amount of bandwidth is left over that can be used for various data broadcast applications. DTV data broadcasting provides many opportunities for both terrestrial and satellite TV broadcasters. There are basically two ways in which broadcasters This paper discusses key issues in this emerging can use this leftover bandwidth to generate area. Topics include: additional revenue: • A classification of data broadcasting in terms of • Use the extra bandwidth to broadcast data target audience and application characteristics which enhances the appeal of their TV programming and/or TV advertising in an • An overview of the DVB Specification for Data attempt to attract more viewer-based revenue. Broadcasting • • Challenges in implementing end-to-end data Lease the extra bandwidth to other enterprises broadcast solutions, especially for enterprise-to- who want to distribute data to large numbers of enterprise applications recipients in the broadcaster’s viewing area. One key challenge is managing the end-to-end flow This paper first analyzes the opportunities that arise of data, with suitable architectural support for from both of these approaches, and describes the content providers, broadcasters, and content mechanisms defined in the DVB Data Broadcast recipients. Other challenges include bandwidth Specification that can be used to support these allocation, error correction, compression, and opportunities. It then focuses on the challenges that security. arise in providing end-to-end support for the scenario where extra bandwidth is leased to other enterprises, with special attention to the optimal system architecture. Introduction

TV broadcasters face significant costs in setting up a digital television (DTV) broadcasting network. They Application Classification may find it difficult to recover these costs through their normal revenue sources. While they will be There are a number of axes which can be used to able to offer more channels of TV programming classify datacasting applications. The single most than before, since DTV enables the packing of important of these in terms of both the business multiple standard definition (SDTV) channels into a model and the technological infrastructure is single 8 MHz broadcast band, nonetheless they will whether the broadcast data is targeted to enterprises still be competing for more or less the same viewer- or to the consumer mass market. based revenue sources as before. Consumer Market. For datacasting applications Data broadcasting (or “datacasting” for short) offers targeted to consumers, a key requirement for success the potential for entirely new revenue sources. With is that large numbers of consumers have a DTV modern DTV encoders, even a high definition receiver (a DTV set, DTV set-top box, or PC with (HDTV) broadcast does not require all of the DTV card) which can receive and use the broadcast bandwidth available in the DTV broadcast stream. A data. For this to happen:

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1. There must be substantial penetration of DTV intended for real-time viewing, such as a 24-hour receivers into the consumer market. news headline or weather or stock ticker service, or 2. The datacasting standards must be reasonably they may be data intended for use completely mature, so that ordinary, off-the-shelf DTV outside the DTV context. receivers typically support them. An example of the latter usage would be delivery of It may take a while yet for these conditions to be very large files, such as MP3 music files or PC met. In the meantime, consumers are unlikely to pay software files or DVD video files. A consumer substantial sums for specialized receivers to access might purchase the right to receive such files from a broadcast data. Web site. In this case the files would be inserted into a DTV broadcast in encrypted form, and a purchaser Utilizing broadcast data requires not only standards would receive keys which could be used to decrypt for encoding the data in the broadcast stream, but them. also standards for applications in the receiver to operate on the data. The DVB Multimedia Home Platform (MHP) Specification [3] is a good example Coupling to of such a standard. It supports both declarative Normal TV Sample Applications (HTML) and procedural (Java) applications. Programming The standardization requirement can be relaxed Tight Statistics during sports event somewhat for applications targeted to consumers (program Story details during newscast with PCs and DTV cards, since custom software to enhancement) support such applications can be downloaded from a Interactive component to ads Web site. However, such applications are still only Loose News and/or stock ticker feasible when large numbers of consumers have (program during newscast DTV cards, which is unlikely to be true for quite augmentation) Supplementary materials for some time. educational broadcasts Datacast applications for consumers can be further None 24-hour stock ticker service classified by the degree of coupling to audio/video programming, as shown in Table 1. Delivery of on-line music sales Tightly coupled data are intended to enhance the TV Delivery of software updates programming in real time. The viewer tunes to the Table 1. Datacast Applications for Consumers TV program and gets the data enhancement along with it. In many cases the timing of the display of the broadcast data is closely synchronized with the For most consumer applications the broadcaster’s video frames being shown. revenue would come from advertising. However, in the case of non-coupled data intended for use For example, a data enhancement for a basketball or outside the DTV context, the broadcaster might be football event may allow the viewer to show and paid for the bandwidth by a third party that actually hide the time clock on command. When the clock is runs the business. In a t-commerce (“television showing, the time on the clock must be closely commerce”) application, the payment to the synchronized to the action on the screen. broadcaster may be calculated as a percentage of Loosely coupled data are related to the program, but sales. are not closely synchronized with it in time. For Enterprise-to-Enterprise Market. For datacast example, an educational program might send along applications targeted to enterprises, there is not so in the broadcast some supplementary reading much need for DTV market penetration and materials or self-test quizzes. These might not even standardization. The value of such applications to be viewed at the same time as the TV program. They enterprise customers may easily be large enough to may be saved in the DTV receiver and perused later, justify the cost of specialized receivers. Thus, but they are still closely related to the program. enterprise-to-enterprise applications may be viable Non-coupled data are typically contained in separate from an economic standpoint much sooner than “data-only” virtual channels. They may be data consumer applications.

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Most enterprise-to-enterprise applications involve is completely up to the application how the data are data which is not coupled to the regular TV formatted inside the packets. programming. Examples include: Streaming data (asynchronous, synchronous, or • Distributing information among state and local synchronized) are carried in Packetized Elementary government agencies, such as agricultural Stream (PES) packets. bulletins and police reports In the case of asynchronous streaming data, the PES • Broadcasting training courses to commercial packet headers do not have Presentation Time Stamp customers, in the form of low-bandwidth video (PTS) values. Thus, the only timing information and ancillary materials about the data in a PES packet is implicit in the actual time the PES packet arrives at the receiver. • Distributing tourist information, weather reports, news clips, sports scores, and related advertising In the case of synchronized streaming data, each to kiosks in hotel lobbies, shopping malls, PES packet header contains a PTS value, and the tourist centers, etc. PES packet payload contains a ”data access unit” • (DAU), which is to be presented to the viewer at the Distributing up-to-the-minute railway schedules time specified by the PTS value in the header. The to electronic signs at railway stops across an PTS values are interpreted relative to a clock defined entire region by “Program Clock Reference” (PCR) values that • Distributing educational materials, including appear in the broadcast stream, as specified in the pages from selected web sites, to public schools MPEG-2 Systems standard [2]. These PCR values may be in the data stream itself, or they may be in a different program element, such as a video stream. Data Broadcast Specification This mechanism is often used to synchronize data display with the frames of a video program. The DVB Specification for Data Broadcasting [1] In the case of synchronous streaming data, each PES defines three separate aspects of data broadcasting: packet header contains a PTS value, and the payload • Data broadcast protocols of the PES packet contains a collection of data bytes • Data announcement and discovery protocols that are presented to the data broadcast application at a specified output data rate, starting at the time The data broadcast protocols specify the precise specified by the PTS value. Typically the PTS formats for data inserted into the broadcast stream. values of successive PES packets relative to each The data announcement and discovery protocols tell other are set so as to produce a very steady data rate how to put information in the broadcast stream over a long period of time. which will allow applications running in receivers to Multiprotocol datagram encapsulation provides a identify and locate the broadcast data. mechanism for transporting data network protocols Data Protocols. The DVB Specification for Data on top of an MPEG-2 transport stream. It is Broadcasting [1] defines 7 data broadcast protocols: optimized for Internet Protocol (IP) datagrams, but • Data Pipe can be used for other data network protocols as well. • Synchronized streaming data Data carousels are used to deliver collections of data modules to receivers by cyclically broadcasting the • Synchronous streaming data modules, one or more times. Thus, a receiver does • Asynchronous streaming data not need to be turned on at any particular time to receive the modules, and for applications such as • Multiprotocol datagrams Teletext it may not even need to cache the modules. • Data carousel It can simply acquire them the next time around. The • Object carousel data carousel mechanism is typically used to deliver files in situations where it is not necessary to have a Data piping is intended for proprietary datacasting hierarchical directory structure. applications. The data are simply packed into the payloads of MPEG-2 transport stream packets, and it Object carousels are used to deliver a structured set of objects, where the objects may be directory

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objects, file objects, or stream objects. The • Error prevention and recovery transmitted directory and file objects contain the • Security contents of the objects, while the stream objects contain references to other streams in the broadcast. • Compression Files may also be delivered in streams of IP packets, Roles. There are three primary players involved in using the Unidirectional Hyper-text Transfer enterprise-to-enterprise datacasting: Protocol (UHTTP) of the SMPTE Declarative Data • Data Provider (or Service Provider) Essence standards [5] on top of the multiprotocol • encapsulation data broadcast protocol. Broadcaster • The term “data service” is used to refer to any Data Recipient collection of one or more of these data types in an A Data Provider is an enterprise that provides data to MPEG-2 program. be broadcast. It may generate the data itself, or it Data Announcement and Discovery. The may aggregate the data from other sources. The Data DVB Specification for Data Broadcasting [1] Provider is typically the direct customer of the specifies a stream_type value to be used for each Broadcaster, paying the Broadcaster for the data broadcast protocol. These values appear in the bandwidth used to transmit the data. Program Map Table (PMT) defined in the MPEG-2 A Data Recipient is an enterprise that receives data Systems standard [2], to identify the PIDs that and uses it. The Data Recipientr is typically the contain broadcast data. The Specification also direct customer of the Data Provider, paying for the defines the use of a number of descriptors that may data it receives and uses. appear in the PMT, and/or the Event Information A Broadcaster provides the broadcast facilities to Table (EIT) and/or Service Description Table (SDT) transmit the data from Data Providers to Data of the DVB SI standard [4], to give additional Recipients. information about the data service. A fourth player in some situations is a Service These descriptors not only allow receivers to Bureau, an enterprise that handles administration of correctly identify and process data services, they one or more components of the datacast sytem as a also allow receivers to indicate data-enhanced audio- service to Data Providers, Broadcasters, and/or Data video programs and stand-alone data programs in Recipients. their interactive Electronic Program Guides (EPGs). Many viewers may choose to watch data-enhanced The same organization may play more than one role programs in preference to non-enhanced programs, in this scenario. For example, in applications where since they are likely to provide a richer viewing a head office is distributing information to branch experience. offices, the same enterprise may be both Data Provider and Data Recipient.

A datacasting system needs to support all of these Implementation Challenges roles. Data Flow. A very important aspect of datacasting The remainder of this paper focuses on enterprise-to- is managing the flow of data from its source, where enterprise datacasting applications (sometimes it is created or aggregated, to its destination, where it called Business-to-Business or B2B applications), reaches the end user. since these appear to offer the best near term revenue opportunities. The data flow normally occurs in four stages: • There are a number of challenges in implementing Fetching the data from its source end-to-end solutions for enterprise-to-enterprise data • Inserting the data into the broadcast stream broadcast applications. Key considerations include: • Extracting the data from the broadcast stream • Business roles of the key players • Presentating the data to the end user • Data flow management These first two stages, fetching the data from its • Bandwidth management source and inserting the data into the broadcast

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stream, may or may not be closely coupled in time. priority level associated with it (with the price For example: In a weather report application new charged to the Provider presumably depending on data may be retrieved from the source at prescribed the priority level). intervals and immediately broadcast. In an These allocations may depend on time of day and agricultural bulletins application new data may be day of the week. received from various sources periodically during the day and broadcast overnight for local agents to A datacasting system should support the allocations examine the next day. In a tourist information of bandwidth to different Data Providers, application the data may be retrieved from the enforcement of the allocations, and in many cases source at random times and then broadcast metering and billing for the actual bandwidth used. continuously. Error Prevention/Recovery. The impact of Retrieval of the data from its source may be based errors may vary widely from one application to on a “push” or a “pull” paradigm. The data may be another. Moreover, a datacasting system needs to be pushed from the source whenever it is created or resilient to the occasional failure of computers or updated, or it may be pulled from the source at other network components in the system, as well as prescribed intervals. to errors arising from corruption of the broadcast stream. Any individual data item may be inserted into the broadcast stream just once, or it may be broadcast The situation is complicated by the fact that DTV some prescribed number of times over some broadcasts are a one-way communications channel. prescribed period of time. If a receiver wants to report errors and ask for a retransmission, it must do so through a separate back The second and third stages, inserting the data into channel. the broadcast stream and extracting the data by a receiver, are inherently closely coupled in time. The In general, some degree of error prevention and/or data must be extracted at the time when it appears, recovery is almost certain to be needed for certain which is essentially the same as the time when it applications. In some cases it may be adequate was inserted. simply to rebroadcast each data item multiple times at prescribed intervals. In other cases a more The third and fourth stages, extracting the data and elaborate forward error recovery scheme may be presentating the data to the end user, may or may needed (above and beyond the forward error not be closely coupled in time. In some cases the recovery scheme that is already a part of DTV data is presented to the end user as soon as it modulation). In some cases a back channel must be arrives. In other cases it is stored and presented to used to check that critical data items have been the end user at some later prescribed time, or received, and perhaps in extreme cases to deliver perhaps only when the end user asks for it. some missing portions to receivers. A datacasting system should support the scheduling A datacasting system should provide appropriate and implementation of these data flows. error prevention and recovery mechanisms. Bandwidth Management. Depending on how the Compression. Given that bandwidth is a valuable Broadcaster makes the trade-offs, the amount of resource, in many applications it is worth while to bandwidth available for datacasting may be constant compress the data before transmission and or may vary from time to time during the day. It may uncompress it upon receipt. This should typically be even vary on a second to second basis, depending on invisible to the end users. the detailed characteristics of the current TV programming, if the Broadcaster really makes an A datacasting system should provide facilities for effort to maximize datacasting revenue. such compression and uncompression. The Broadcaster may choose to allocate this Security. End-to-end security may be very bandwidth among multiple Data Providers, possibly important for enterprise-to-enterprise applications. with different priorities. Each Data Provider may be In some cases it is simply a matter of assuring that allocated a certain amount of guaranteed bandwidth, no one gets the data unless they have paid for it. In plus a certain additional amount on a “best effort” other cases, such as distributing police reports and basis. The “best effort” bandwidth may have a other government information, it may be essential to

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protect the data from disclosure to unauthorized number of facilities in order to support enterprise-to- persons for privacy reasons. enterprise data broadcasting properly. A key factor This means that it may be necessary to maintain in the ability of a system to provide these diverse security for the data at every step of the way: facilities is the underlying system architecture. • During fetch from the source The ideal system architecture should mirror the problem space. In particular, it should explicitly • While in cache waiting for transmission recognize and support the roles of Data Provider, • During transmission in the broadcast stream Broadcaster, and Data Recipient. • While in the receiver waiting for use An architecture for a datacasting system which meets this need very well is shown in Figure 1 In some cases the data must be kept confidential below. It consists of three primary components: even from the Broadcaster. In other cases the Broadcaster must be allowed to inspect the data to • Data Scheduler assure that it meets suitable standards for the type of • Data Hub data the Broadcaster is willing to transmit. • Data Receiver A datacasting system should provide an appropriate framework within which encryption/decryption and In a typical deployment scenario there would be passcode mechanisms can be accommodated, to many Data Scheduler components for different Data provide an appropriate level of security. Providers, scheduling data for one or many Data Hubs, and there would be a large number of Data Receivers. Three-Component Architecture It is clear from the discussion in the preceding section that a datacasting system must provide a

Broadcast Station Media Data Receiver Encoded Player (SkyScraperTM Video MUX Xmitter DataReceiver) Local File

Data Hub Web Network (SkyScraperTM DataHub) Server Server

LAN IP Network

Web Media Network Data Scheduler Data Browser Player Client (SkyScraperTM DataFab) Source(s)

Content Provider Content Recipient

Figure 1. Data Broadcast System Three Component Architecture

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Data Scheduler. The Data Scheduler allows the It then renders the data items with a suitable player, Data Provider to identify the data items that are to be stores them on local or network disk, retransmits broadcast, and to specify the detailed scheduling for them on a local LAN, or stores them in a database, fetch and broadcast of individual data items. The depending on the nature of the data. specifications are transferred automatically from the Data Specifier to the Data Hub for use by the Data Hub as needed. A system that allows the Data Summary Provider to do this scheduling function directly has Data broadcasting presents a potentially very advantages for both Data Provider and Broadcaster. valuable revenue opportunity for DTV broadcasters. The Data Provider can change the scheduling at any Enterprise-to-enterprise applications are likely to be time without involving the Broadcaster in the the best way in the near term to take advantage of process and going through a lot of red tape. The this opportunity. Broadcaster does not have to devote any clerical Implementation of such applications presents a resources to this task. number of challenges in such areas as data flow Data Hub. The Data Hub receives specifications management, bandwidth allocation, security, data from one or more Data Specifiers, fetches the data compression, and error recovery. directly from the data source locations (which may A three-component architecture is presented which or may not be different from the Data Specifier supports the three primary roles of Data Provider, locations), and inserts the data into the broadcast Broadcaster, and Data Recipient. This architecture stream, following the schedules in the specifications facilitates efficient, robust solutions to the system received from the Data Specifiers. requirements. If compression, encryption, and/or forward error correction encoding are needed, they may be applied to the data at the data source, or they may be applied References by the Data Hub after the data are fetched. [1] Digital Video Broadcasting (DVB): DVB The Data Hub allows the Broadcaster to specify the specification for data broadcasting, ETSI Document bandwidth allocations and priorities of the various EN 301 192 v1.2.1 (1999-06), Jun 1999. Data Providers, and it enforces these allocations. If [2] Information technology – Generic coding of the detailed schedule specified by a Data Provider moving pictures and associated audio information: causes an overrun of the Provider’s allocated Systems, ISO/IEC 13818-1:2000, Dec 2000. bandwidth, the Data Hub throttles it down to keep it [3] Digital Video Broadcasting (DVB): Multimedia within the allocation, and notifies the Provider that it Home Platform (MHP) Specification, v1.0.1, ETSI has done so. Document TS 101 812 V1.1.2 (2001-10), Oct 2001. The Data Hub also meters bandwidth usage and can [4] Digital Video Broadcasting (DVB):Specification generate billing reports as needed. for Service Information (SI) in DVB systems, ETSI Data Receiver. The Data Receiver extracts the Document EN 300 468 V1.4.1 (2000-11), Nov 2000. data from the broadcast stream and applies [5] Declarative Data Essence - Unidirectional decryption, uncompression, and forward error Hypertext Transport Protocol, SMPTE standard recovery as needed. It provides the Data Subscriber 364M-2001. with a menu of the authorized items in the broadcast stream (generated from specifications provided by the Data Specifiers, which are transmitted in the broadcast stream), and allows the Data Recipient to select which ones to actually extract and which ones to ignore.

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