NOTE Digital broadcasting in the world Hidenori Gohara Kazuo Takayama ・Advanced functions (data broadcasting / two-way 1 Introduction capability) The history of broadcasting began with radio broad- Digital broadcasting's data broadcasting capability can casts in the USA in the 1920s. Since then it has enable viewers to, for example, check out player sta- advanced to TV broadcasting, color TV broadcasting, tistics and get weather forecasts, news and other and latterly digital broadcasting. information while watching a baseball program. And This technical note examines the global trends in its two-way transmission capability can enable them digital broadcasting, the technology for digital broadcast- to buy tickets or respond to polls, etc., during the pro- ing, and the problems for reception by mobiles gram. 2. What "digital broadcasting" is 3. Global trends in digital broadcasting 2 What "digital broadcasting" is 3 Global trends in digital broadcasting As opposed to transmission of continuous signals in [Europe] conventional analog broadcasting, digital broadcasting Digitalized terrestrial audio broadcasting was the uses various encoding and multiplexing techniques to first digital broadcasting to be brought into practical use transmit signals. in Europe. DAB (digital audio broadcasting), which is Digitalization of broadcasting permits realization of broadcasting via terrestrial transmission of digitalized new services such as those listed below. audio signals, began here in 1996. It permits users to ・High visual and sound quality enjoy services such as: Digital broadcasting permits enjoyment of more ・High quality, CD-equivalent sound even in situations attractive and strongly realistic visuals and sound. where multipath interference (reflected and other And for radio it permits high sound quality with clari- waves from hills and buildings, etc) is present. ty on a par with CD. ・High quality reception even in mobiles such as cars. ・Large number of channels The following year saw the start of satellite digital TV Thanks to its highly efficient frequency utilization, (DVB-S) and terrestrial digital TV (DVB-T) in Europe. digital broadcasting can transmit many more pro- Table 1 Digital broadcasting in the world grams in a given bandwidth than analog broadcasting. System name Broadcasting Starting year Mobile reception Europe DVB-T TV Terrestrial 1998 △ DVB-S TV Satellite 1998 × ・What's the news today? Coming up soon DAB Audio Terrestrial/Satellite 1996 ○ USA Japan IBOC Audio Terrestrial 2003 ○ 2:00 Drama serial ... ・What are the ball game Sirius Audio Satellite 2001 ○ results? Baseball League Bulletin XM Audio Satellite 2001 ○ G 1-0 C H 5-0 L ISDB-S TV Satellite 2000 × ・What's on TV later? T 3-2 S Bu 9-7 B ISDB-T TV/Audio Terrestrial 2003 ○ D 0-3 YB F 3-4 M MSB Audio Satellite 2003 ○ News Headlines ※ Starting years in the future are projected DVB : Digital Video Broadcasting Earlier this afternoon, ... DAB : Digital Audio Broadcasting IBOC : In-Band On Channel Sirius : Sirius Satellite Radio XM : XM Satellite Radio ISDB : Integrated Service Digital Broadcasting ISDB-T : ISDB-Terrestrial ISDB-S : ISDB-Satellite Fig.1 Concept of digital broadcasting MSB : Mobile Satellite Broadcasting 41 FUJITSU TEN TECHNICHAL JOURNAL [USA] all wavebands, with the aim of providing a higher grade The USA has a fully developed road network that of sound quality for both AM and FM. enables car travel over long distances inconceivable in The basis of the above-mentioned IBOC hybrid Japan. The network has also however posed a problem method is analog and digital streams with identical con- for radio in that travelers could not continue listening to tent. Analog broadcasts can be received with conven- the same programs as they crossed into different ser- tional radio tuners, but the hybrid method differs some- vice areas. The response to that problem is digital radio what between AM and FM (refer to Fig. 3). broadcasting via satellite, which can be received over AM bands the entire territory of the USA. This satellite digital The method is to apply low-level digital signals with- radio is very much in the limelight, and has the follow- in the current analog signal wavebands and flanking ing features: both their side bands. This will give digital audio signals ・It broadcasts using the new waveband 2320-2345 of equivalent quality to current FM signals. MHz, via either 2 or 3 broadcasting satellites. Transmission of simple data is also planned. In blind areas it uses terrestrial retransmission facili- FM bands ties called "repeaters," thus permitting broadcasting The method is to flank both side bands of current over the entire national territory. analog signals with low-level digital signals. This gives ・As of now 2 companies have entered the satellite digi- digital audio signals of equivalent quality to CD. As with tal radio arena: XM (XM Satellite Radio company) and hybrid AM, transmission of simple data will also be pos- Sirius (Sirius Satellite Radio company). The former sible. began broadcasting in 2001 and latter in 2002. FM Hybrid FM All-Digital 0dBc/kHz 0dBc/kHz Analog Side-Band 2320MHz～2345MHz -25dBc/ k -25dBc/ k Music / Visuals / Data kHz kHz Center Channel Center Channel AM Hybrid AM All-Digital 0dBc/kHz 0dBc/kHz Broadcasting over entire USA Analog Side-Band -44dBc Digital Band -30dBc -20dBc/ k Repeaters -220kHz cover blind areas kHz kHz Fig.2 Concept of North American satellite digital radio Fig.3 Image of IBOC Table 2 Comparison of XM and Sirius companies [Japan] Broadcasting company XM Sirius Following on the CS and BS satellite digital broad- 2 stationary orbit satellites, 3 elliptical orbit satellites, casts that appeared in 1997 and 2001 respectively, Japan Broadcasting satellites each with output 15 kW each with output 8 kW is currently moving ahead with preparations for mobile Terrestrial repeaters 1700 units 100-200 units broadcasts (satellite digital radio) that are scheduled to Broadcast content Music + voice (100 channels) 50 music channels + 50 voice channels begin in fiscal 2003. Compared to the existing CS and BS broadcasting this will be a completely new service since Reception fee Around $10 / month Around $10 / month it will be possible to receive it while moving at high However there is also the fact that the USA has speed anywhere in the country. It will use the S (2.6 many FM and other radio stations that use terrestrial GHz) band. Through terrestrial retransmission facilities waves, serving small areas. Therefore efforts are being called "gap fillers" it is planned to provide multimedia made to develop for practical use a method (IBOC: In- broadcasting combining high-quality music, visuals and Band On Channel) that will permit digitalization within data to cars and other mobiles. the frequency bands assigned to analog broadcasting. As regards digitalized terrestrial broadcasting, in This method employs hybridization by adding digital 2003 the major cities of Tokyo, Nagoya and Osaka will signals within analog broadcasting wavebands; later it is begin receiving ISDB-T digitalized terrestrial TV broad- planned to make a transition the all-digital method for casts, which are expected to develop into nationwide FUJITSU TEN TECH. J. NO.19(2002) 42 Digital broadcasting in the world ・Reception by mobiles thanks to employment of a S band method that is robust against multipath interference and fading. Gap fillers Music / Visuals / Data ・Broadcasting of 2 or 3 programs using the same band- width that conventional analog broadcasting needs for a single channel. ・Users will be able to search for information on their screens and find with ease the channels they want to Mobiles watch. And by storing text and static image data on Homes their receiver they will be able to view news and ・Nationwide broadcasting ・High quality audio (comparable to CD) event information etc., whenever desired. Fig.4 Concept of mobile (pay) broadcasting Preparations are also underway for the start of digi- talized terrestrial audio broadcasting, which will use nar- broadcasts in the years from 2006 onward. ISDB-T uses row-band. As a rule digitalized terrestrial audio broad- UHF (470-770 MHz) waves, which it broadcasts with the casting uses VHF bands, but due to the deployment of same bandwidth as conventional analog broadcast the current analog TV channels it is planned to use waves (around 6 MHz) but divided into 13 segments. By channel 7 (188-192 MHz) for this broadcasting. using 12 or all 13 of these segments it can implement The broadcasting configuration will employ 1 seg- high visual quality HD (high definition) TV broadcasts. ment or 3 segments to provide enjoyment of audio with Alternatively it can split the 13 segments into up to 3 CD-level high quality plus simple visuals. And since it layers to provide multiple SDTV (standard definition will be mandatory to provide a partial reception seg- TV) programs, or partial receptioni broadcasting of sin- ment in 3-segment broadcasting, users with 1-segment gle programs (simulcastsii using MPEG4iii) for mobiles. receivers will be able to enjoy a part of 3-segment Digitalized terrestrial TV broadcasts will eventually broadcasts. replace conventional analog terrestrial broadcasting, which is scheduled to end in July 2011. The introduction of digitalized terrestrial TV broad- 7ch casting will permit realization of services such as the fol- Music Homes Simple motion pictures High sound quality sound radio, data broadcasting lowing: Simple data ・High quality visuals and audio thanks to employment (Partial reception) of a method that is not susceptible to the influence of noise and is robust against ghost signals. Mobile receivers Partial reception Service configuration (example) HDTV Homes SDTV HDTV, SDTV, data broadcasting 3segment method 1segment method Data broadcasting B A B A Partial reception Mobiles Partial reception (simulcasts using MPEG4) 1- / 3-segment receiver 1-segment receiver Service configurations (examples) Fig.6 Concept of digitalized terrestrial audio broadcasting 13segments 12segments 1segments 5～11segments 1～7segments 1segments AACACB The next section presents the technology used in Japan's digitalized terrestrial broadcasting.