Digital Audio Broadcasting: An Interactive Services Architecture Pythagoras Karampiperis
Technical University of Crete, Telecommunications Laboratory, 73 100, Chania, Greece
[email protected]
Technical University of Crete, Telecommunications Laboratory, 73 100, Chania, Greece
[email protected]
Abstract. Digital Media Technologies offer enhanced multimedia signal broadcasting and description of the signal on content. Digital Audio Broadcasting (DAB) is a media standard with extended multimedia capabilities, offering novel services to users worldwide. Each digital broadcasting standard though, cannot be separately viewed from the development of Internet radio broadcasting. In this paper we introduce a multi-agent based system architecture, specially designed to provide and support advanced interactive services between users and digital media broadcasting systems, such as DAB and Internet radio broadcasting.
format through networks, either the Internet or DAB. Additionally, digitalisation of data makes it possible today to transport information on content and not only data itself, as exemplified by the MPEG-7 project. The question of identifLing content is not just restricted to database retrieval applications such as digital libraries, but extends to areas like broadcast channel selection, multimedia editing and multimedia directory services. That means that more and more user guided or automated intelligent systems will operate on digital audiovisual data, trying to extract or manipulate information for some specific purpose. These operations do not fall in the usual categories of rational decision making, leading us thus in embedding new structures of decision aid systems into ordinary broadcasting platforms.
O
SI
ER
1 Introduction
N
Nikos Manouselis
FT
V
During the past few years, new trends have been developed in the field of Media Broadcasting Technologies. Throughout the world digital communication techniques have successfully been developed, making so one thing certain: the conventional world of radio broadcasting is highly transformed by the arrival of novel digital media services like Digital Audio Broadcasting.
In this paper we present an agent based decision support architecture, offering interactive services and advanced content selection and transmission. Throughout Section 2, a brief introduction to the main features of the DAB system is made. Section 3 outlines the basic characteristics of the proposed architecture. In Section 4 some basic conclusions from our research are stated.
The Eureka DAB system [4] is designed to provide reliable, multi-service, digital sound broadcasting for reception by mobile, portable and fixed receivers, using a simple, nondirectional antenna. It can be operated at any frequency up to 3 GHz for mobile reception (and even higher for fixed reception) and may be used on terrestrial, satellite, hybrid (satellite with complementary terrestrial), and cable broadcast networks. In addition to supporting a wide range of sound coding rates (and hence qualities), DAB is also designed to have a flexible, general-purpose digital multiplexer, which can support a wide range of source and channel coding options, including soundprogram associated data and independent data services.
Progress in networking transmission, compression of audio and protection of digital data allows services like delivering quickly and safely music to users in a digital
The feasibility of current and future applications like DAB greatly depends on the use of data compression techniques that reduce the data transmission rate and memory storage
D
R
A
The telecommunication market is expected to be one of the most crucial markets of the future [9]. It is already one of the most rapidly developing areas, especially in terms of deregulation and strategic impact. As a consequence, network providers are forced to develop to service providers that offer the customer not only simple network use, but complete value added services within the network, i.e. the Internet. A secure, reliable and integrated approach to provide services and operation is required. The agentoriented approach seems to be one of the most promising ones in order to fulfil these criteria. Only with autonomous, dynamic entities (agents) it is possible to adapt to the differences and requirements in the heterogeneous networks of different providers during runtime.
0-7803-7080-5/01/$10.00 02001 IEEE
2 The DAB System
666
Moreover, the ISO/IEC MPEG standardization group adopted a set of requirements in order to provide extended features both to end-users and to content creators. Some of these fimctionalities [2] are:
O
-
-
-
a new kind of interactivity, with dynamic objects rather than just static ones; the integration of natural and synthetic audio and visual material; the possibility to influence the way audiovisual material is presented; reusability of both tools and data a coded representation hiding lower layers to the application developer; the simultaneous use of material coming from different sources and support of material going to different destinations; the integration of real-time and non-real time (stored) information in a single representation.
N
-
ER
DAB uses the MPEG Audio Layer I1 system ([3], [5]) to achieve a compression ratio of 7: 1 without perceptible loss of quality. This system is modelled on the working of the human ear, and retains only the audible components of the sound. The signal is then encoded at a bit rate of 8-384 Kbdsec, depending on the desired sound quality and the available bandwidth. Program Associated Data (PAD) is incorporated and the signal is individually error protected and labelled prior to multiplexing. Independent data services are similarly encoded.
generation replacement for existing, long established communications media, as the telephone system, radio and TV. In all three cases, the basic functionality of these communications systems has not changed in several decades; addition of extra features is difficult. Digital Audio Broadcasting simply replaces the transmission infrastructure, without actually offering significant new services. It does not also change the fundamental issue that only a very small number of stations can transmit at any given time, at a specific region.
SI
requirements. Given the existence of such techniques, terrestrial or satellite transmission channels can be economically employed for single or multi-channel audio data transmission, and also data storage media can be efficiently utilized for storing lengthy segments of acoustic signals. The storage and transmission of such highquality audio data (as reference we consider the compact disc format, based on a 44.1 kHz sampling rate and 16b resolution) results in the relatively high bit-rate of 706 kb/s per data channel. This data rate can be technically or economically prohibited for many applications, and this necessitates the introduction of data compression, preferably by using low-complexity methods and without he insertion of perceptually detectable distortions [8].
D
R
A
FT
V
Multiplexing fits the labelled packages from each signal into a standard ‘outer container’ to ensure efficient use of the radio spectrum. Broadcasters can dynamically adjust the composition of the multiplexed signal to provide any desired combination of services, from 6 highquality stereo programs to as many as 20 mono programs. Information about the current configuration of the multiplexed signal together with additional error protection data is also included. By employing Coded Orthogonal Frequency Division Multiplexing (COFDM), the 2.3 million bits of the multiplexed signal are spread out in time and across 1,536 distinct frequencies within the 1.5 MHz band, so that even if some frequencies are affected by interference, the receiver will still be able to recover the original signal.
Apart from distortion-free reception and highquality sound, DAB offers further advantages, since it has been designed especially for the needs of the multimedia age. DAB embodies audio as well as text., pictures, additional data and even videos. However, two matters have given rise to much concern. The first one is the difficulty of achieving a smooth replacement of the analogue FM broadcasting systems with the new digital ones. The second matter has not been widely discussed, but is concerned with the effect that the vast explosion of Internet radio broadcasting will have on the establishment of Digital Radio Broadcasting. Recently there has been wide interest in having the Internet serve as next-
-
-
The added value of the ISOAEC MPEG standards becomes apparent with the possibility to provide interactive content using the broadband -networks of the new media technologies. 3 Proposed Architecture 3.1 Agent based architecture
Agent-based software components have been proposed [6] to help with service deployment in today’s increasingly complex open telecommunications market. We address here an agent based decision support system, which is providing interactive services and advancing the existing DAB services to a higher level. This system, combined with several proposed bi-directional service standards (like the MEMO system [l]), can offer advanced deviceembedded interactive services, extending so the interactivity of services beyond the World Wide Web. This decision support system utilizes several models with ascending customisation degrees, which reflect the shareout of intelligence between the users and the service
667
support system, as well as ever growing user involvement in the service customisation process [6].
shown in Figure 2, these applications include all the subsystems analysed in the previous sub-section, and are the following:
Our research was towards an architectural structure that could offer to the radio station the tool to identify and monitor the users accessing its network, in order to personalize the broadcasted multimedia signal according to their demands and preferences. This kind of interaction requires bidirectional communication between the service provider and the user (supported by various proposed enhancements of the DAB system, as it was mentioned above) and a decision making modelling process, so that the preferences and demands can be aggregated into a personalized profile.
-
V FT
ArdrtantAgmt
R
A
Figure 1: Listener’s systems connecting to the Radio Stations Database
-
D
The basic reasons for such a multi criteria modeling of the users demands and preferences are stated below:
-
O
N
f
ER
AsdstarbAsnt
-
-
SI
The agent-based proposed architecture (Figure 1) utilizes several multi-attribute utility models [7] in order to construct a concrete preference model of the connected user. In this way we achieve a full modelling of the connected listeners, providing to the radio station with an overview of its customers and their preferences.
-
A Database Management Application that handles the audio signals, and supports all relevant functions such as encoding of audio samples, association of multimedia objects to audio signals, controlling RDS and DAB enhanced services, etc. A Server Application that keeps the audio signals and associated multimedia objects always available for broadcasting. A Client Application for each remote listener, which receives the broadcasted signal.
introduction of both quantitative and qualitative criteria that a listener takes into consideration, in the evaluation process of a radio station; transparency in the evaluation, allowing good argumentation in decisions; introduction of sophisticated and realistic scientific methods in such fields of practical interest.
3.2 Radio Broadcasting Platform The different parts that the radio broadcasting platform consists of, are implemented in three autonomous, but cooperatively working, software applications. As it is
-PLATFORM
TYPES OF USTENERS
6 USTENER
Figure 2: Software modules Each way of broadcasting demands its own client application for receiving, decoding and presenting the
signal to the usedlistener. The FM and DAB receivers include this particular software in their own embedded software applications. In the case of Internet listeners, a special client application was designed and implemented, in order for the user to connect with the server and start receiving the audio signal and the associated multimedia objects from the broadcaster. The system is designed in such a way that its database contents and handling capabilities can be located at different locations. The Server Application is the one that has to be located at the radio station, which fetches the audio samples and the multimedia objects associated with them from the locations indicated by the Database Management Application. In this way distribution of the applications working together is accomplished, and thus restrictions regarding the location of the system and of the users working with it are eliminated. The system that was implemented consists of software libraries and executable software components, created with
668
various programming tools like Delphi, Visual Basic and C++. The software libraries contain applicationindependent components, such as the MPEG encodeddecoder or the COFDM multiplexer/ demultiplexer. These modules are described in the following sub-section. The software executables implement the modules embedded into the sub-systems described and use the software libraries in order to perform all tasks regarding handling, storing and broadcasting the multimedia signals. The platform was designed to work under all operating systems, but its prototype version is currently working under Microsoft Windows NT, 2000,98 or Millennium editions.
[4] European Telecommunication Standard Institute, ETSI: Radio broadcast systems; Digital Audio Broadcasting (DAB) to mobile, portable and fixed receivers, ETS 300 401, May 1997. [5] ISODEC, Coding of Moving Pictures and Associated Audio for Digital Storage Media at up to about 1.5 Mbit/s - Part 3:Audio, 1 1172-3 (1993-08), August 1993. [6] Maknavicius L., Koscielny G., Znaty S., “Customizing Telecommunication Services: Patterns, Issues and Models”, H. Zuidweg et al. (Eds.), IS&N’99, pp. 194-209, LNCS 1597, Springer-Verlag, 1999.
4 Conclusions
O
N
[7] Manouselis N., Matsatsinis N., “Introducing a MultiAgent, Multi-Criteria Methodology for Modeling Electronic Consumer’s Behavior: The Case of Internet Radio”, submitted for presentation, CIA 200 1, Modena, Italy.
SI
[8] Paraskeuas M., Mourjopoulos J., “A Differential Perceptual Audio Coding Method with Reduced Bitrate Requirements”, IEEE Transactions on Speech and Audio Processing, Vol. 3, No. 6, November 1995.
[9] Wieczorek D., Albayrak S., “Open Scalable Agent Architecture for Telecommunication Applications”, S . Albayrak and F.J. Garijo (Eds.), in IATA’98, pp. 233-249, Springer-Verlag, 1998.
A
FT
V
ER
This paper presented an interactive multimedia platform capable of analogue, digital andor Internet broadcasting. We introduced an especially designed architecture, aiming in intelligent decision support to the user and enhancing the interactive services that digital media technology can offer. This system provides any radio station with a powerful software tool that exploits all available resources with the minimum possible cost. It is compatible with the European specification for DAB systems and it is especially designed to meet user demands. The system is flexible enough to encompass any audio coding algorithms. It has the capability to process, in a digital fashion, every kind of audio or multimedia signals. It offers multiplexing on the logic level and has the ability to fully exploit all enhancements provided by the Digital Audio Broadcasting standard. Moreover, it enhanced the original DAB system’s facility of one-way, high bandwidth, downlink broadcasting in the logic level, supporting so systems like MEMO [I].
R
References
D
[ I ] Alty J., Bridgen A., Duncumb I., Ebenhard J., Ruottinen P, “MEMO: The Specification of a Hybrid System for Interactive Broadcast and Internet Access using DAB and G S M , H. Leopold and N. Garcia (Eds.), ECMAST’99, pp. 534-55 1, LNCS 1629, Springer-Verlag, 1999.
[2] Becchini R., De Petris G., “Java Enabled MPEG-4 Services: The MPEG-J Framework”, H. Zuidweg et al. (Eds.), in IS&N’99, LNCS 1597, pp. 373-384, SpringerVerlag, 1999. [3] De Gaudenzi R., Luke M., Stoll G., “The New ISOMPEG Standard for Low Bitrate Audio Coding and its importance for DAB”, Audio and Video Digital Radio Broadcasting Systems and Techniques, Elsevier, 1994.
669
