FUJITSU TEN's Approach to Digital Broadcasting ● Mitsuru Sasaki ● Kazuo Takayama 1. Introduction Digital broadcasting offers viewers numerous There has been a notable increase recently in the advantages, including the following: number of television commercials advertising television • High broadcast quality (audio quality and image sets that can receive broadcasts in digital format. In a quality) move reminiscent of the shift from the analog record to • Efficient utilization of frequencies (increased number the compact disc (CD) and the mini disc (MD), the of channels) broadcasting industry is gradually moving toward • High number of value-added services (multimedia digitization. services) This technical note gives an overview of, and NHK Science & Technical Research Laboratories introduces the current state of affairs surrounding digital presented concepts of digital broadcasting services in broadcasting worldwide, and Fujitsu TEN's efforts in this their annual exhibition in 1999. The key concept was field. "useful digital broadcasting," or a shift from "viewing" to "using." The following figure illustrates the concept: 2. Understanding Digital Broadcasting Conventional broadcast systems that transmit signals EPG� that are continuous over time through amplitude (program guide) modulation (AM) or frequency modulation (FM) were Detailed local � News � weather � on demand once common. In contrast to these analog broadcast forecast systems, digital broadcasting uses a variety of encoding From "viewing" � and multiplexing technologies for transmission. to "using" Emergency � Program-� broadcasting � linked � services (local) Home server for � recording programs Analog * Weather: Enables users to retrieve local weather forecasts by � modulation entering a postal code or telephone number.� * EPG: Provides program guides that enable users to select, find, � or reserve programs.� Analog broadcasting * News: Enables users to view news without having to select a � particular news program.� Can transmit multiple voice and * Emergency: Overlays the current displays with relevant � data signals simultaneously emergency information during regular programming.� * Server: Enables users to view a program from the beginning even � if it has already started.� Digital * Linkage: Provides details about programs, such as the names of � modulation featured personalities.� � Digital Fig. 2 Useful digital broadcasting ↑�↑�↑� broadcasting Sampling Advantages So that mobile receivers can also offer the above Analog-to-digital • High quality and high definition conversion • Increased number of channels advantages, some mobile broadcast systems have a • Multimedia services variety of features, including the following: Fig. 1 Analog broadcasting and digital broadcasting • Synchronization for reliably capturing radio waves as 43 M. Sasaki et al.: FUJITSUN TEN's Approach to Digital Broadcasting the receiver moves MPEG2 is widely used as the technology for Video • Powerful error correction to eliminate errors caused and Audio compression. The MPEG2-Systems standard, by noise or other factors however, also stipulates a method of multiplexing. • Selection of transmission parameters considering the MPEG2-TS (transport stream) is a variation for possibility of multipath reception. broadcast use. Its data structure is included in MPEG2- Systems, and it is also an international standard. Fig.4 3. Technologies Used in Digital Broadcasting illustrates the concept of MPEG2-TS. Digital broadcasting is implemented with a variety of technologies. They can be classified into the major Contents Video Audio Data (MPEG) categories given below, which differ slightly depending Split on the broadcasting method and the conditions specific to the country that developed the method: Small • Information source encoding technologies elements� Technologies for encoding (digitizing) audio and ・�・�・� ・�・�・� ・�・�・� image data. Moving Picture Experts Group (MPEG) and other high-efficiency compression technologies are often Rearrange used. • Multiplexing technologies TS ・�・�・�・� Technologies for integrating several encoded →� →� information sources into a single data item so that the 188 bytes sources can be linked to each other Fig. 4 Concept of MPEG2-TS • Transmission path encoding technologies (modulation and error correction) 3.2 Transmission Path Encoding Technologies Error correction using a pre-appended code to correct Before reaching the receiver for reproduction, errors which might occur in the transmission path, and multiplexed data (information) may be exposed to many modulation technologies for superimposing data on radio types of interference that might result in loss of data. To waves prevent this problem, the broadcast system uses error correction technology to ensure that the data can be Transmission path encoding Information Multiplexing restored if the degree of the error remains below a source encoding Error correction Modulation specified level. Data with an error correction code appended is Correction Digital modulation Encoding image code digitally modulated using a method such as Phase Shift Keying (PSK), Quadrature PSK (QPSK), and Quadrature Super- Amplitude Modulation (QAM: Fig.5). Encoding voice Multiplexing imposing （0.1）�（0.0）� Encoding data Fig. 3 Outline of technologies used in digital broadcasting The following subsections describe the major （1.1）�（1.0）� multiplexing technologies and transmission technologies (modulation systems). QAM symbol positions 16QAM symbol positions 3.1 Multiplexing Technologies Fig. 5 QAM symbol positions Most broadcast systems have chosen to use MPEG2- The digitally modulated data is superimposed on Systems (ITU-T H.222.0 and ISO/IEC 13818-1) for carrier waves for broadcasting. Some systems use a multiplexing. single carrier wave (single-carrier systems) and others FUJITSU TEN TECH. M., NO.15 (2000) 44 M. Sasaki et al.: FUJITSUN TEN's Approach to Digital Broadcasting use multiple carrier waves (multicarrier systems). Many Table 2 DAB coverage in major countries multicarrier systems use orthogonal frequency division Covered� Covered� multiplexing (OFDM), described later. Country population Country population Belrium 80% Canada 30% 4. Digital Broadcasting Worldwide Denmark 30% Germany 30% The digitization of broadcasting is a worldwide Finland 40% Poland 8% trend. Europe is moving ahead of other countries, having France 26% Suth Africa 28% already implemented satellite and terrestrial broadcasting Italy 10% Sweden 80% via digital modulation. Spain 30% Singapore 100% Table 1 Digital broadcasting in major countries digitization in accordance with the specific conditions of Mobile � each broadcasting station. Fig.6 illustrates the system, Name Broadcasting Started in reception called In-Band On Channel (IBOC). DVB-T TV Terrestrial 1998 △� Europe U.S. Conventional DVB-S TV Satellite 1998 ×� analog broadcasting DAB Audio Terrestrial� ○� Satellite 1997 IBOC Audio Terrestrial To be determined ○� Sirius Audio Satellite 2001 ○� � XM Audio Satellite 2001 ○� ISDB-S TV Satellite 2000 ×� Japan ISDB-T TV� Terrestrial 2003 ○� Audio Superimposed digital broadcasting MSB TV� Satellite 2002� ○� Audio � Fig. 6 Concept of IBOC Note: Future years indicate planned schedules.� * DVB: Digital Video Broadcasting� * DAB: Digital Audio Broadcasting (Eureka-147)� In addition, the U.S. has a well-developed road * IBOC: In-Band On Channel� network, which allows people to drive very long * Sirius: Sirius Satellite Radio� distances that are almost impossible to visualize in Japan. * XM: XM Satellite Radio� When people drive across a service area, they cannot * ISDB: Integrated Service Digital Broadcasting� * MSB: Mobile Satellite Broadcasting continue to view or listen to the same program being broadcast in that particular area. Currently, attention is being focused on digital radio broadcasting via satellite Europe was the first to implement digital terrestrial that, as a service that can be received anywhere in the broadcasting by applying a method called Digital Audio country, is expected to solve this kind of problem. Broadcasting (DAB). The Eureka-147 project in Europe, Currently, two companies (XM Satellite Radio and which has been leading the development of DAB, started Sirius Satellite Radio) are developing digital satellite broadcasting in 1997. In the U.K., this broadcasting radio broadcasting and will start broadcasting in 2001. currently covers 65% of the population. With the In Japan, digital terrestrial television broadcasting exception of the U.S. and Japan, numerous countries will start in the three metropolitan areas (Tokyo, Nagoya, outside Europe have also adopted this method and are and Osaka) in about 2003. Digital terrestrial audio moving toward implementation. broadcasting will start a little earlier. The U.S. is developing a digital broadcast system Japanese digital terrestrial broadcasting (ISDB-T) using a method different from DAB. will have the following features: The U.S. has an extraordinarily large number of FM • Less susceptible to ghosts (interference) and other radio stations that are relatively small in terms • Supporting a single-frequency network (SFN) of business scale. The country is, therefore, developing a • Allowing for mobile reception system that allows digitization within the frequency band • Providing layered transmission enabling selection of assigned to analog broadcasting, and promoting a modulation system FUJITSU TEN TECH. M., NO.15 (2000) 45 M. Sasaki et al.: FUJITSUN TEN's Approach to Digital Broadcasting