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Digital Radio Part 5: The Official Australian Start – 6th August 2009 Australia, currently the country with largest population to adopt DAB+, was instrumental in the adoption of the DAB+ as a world standard. Switzerland, Malta, Hungary, Poland and Singapore already have DAB+. It is to be launched in Germany and Italy this year and will be the standard in the Czech Republic, Israel, Malaysia, Indonesia, China, much of Scandinavia and other European and Asian markets. by Alan Hughes W hen FM radio was first being introduced, it wasn’t particularly attractive for the AM broadcasters of the day. For a start, there were very few radio receivers with an FM band, mainly because manufacturers didn’t want to waste money fitting what amounted to a separate front-end for a band which had only a few “experimental” transmissions on it. Second, AM broadcasters saw FM as a threat, something that might go away if ignored. Or that FM would not attract listeners from AM. Around that time, something happened which made them change their minds: imports of receivers with both AM and FM bands flooded in as the Australian radio manufacturing industry collapsed. In more recent years, huge amounts of money have been paid for commercial FM licences; even low-power, restricted area licences have attracted enormous bids, making analysts wonder how on earth these stations can ever be a moneymaking proposition. Today, the commercial stations have seen the error of their ways and have certainly not refused free DAB+ frequencies. In fact the broadcasting industry has been the main force in pushing government to allow DAB+ transmissions. They did not want to be left behind (again!) in the digital race. The advantages of DAB+ are irresistible; 15 – 25 audio services per DAB+ channel and better resistance to errors. There is one transmitter per DAB+ channel. 24  Silicon Chip Many radio manufacturers are developing DAB+ sets which will be progressively marketed in the coming months. Commercial Radio Australia has been supplying manufacturers with disk copies of some transmissions. This is so they can test their designs on DAB+ to optimise the sound quality and to ensure the receivers at the edge of the coverage area mute quietly, unlike some DTV receivers. Commercial Radio Australia has also been in negotiations to convince car makers to include digital radios in new models. Existing car users can use a product like the “Pure Highway” as seen in “Digital Radio part 4”. Receiver Profiles WorldDMB and the European Broadcasting Union have defind three basic receiver profiles. Profile 1 radios are available now; Profile 2 receivers should be available by the end of the year and Profile 3 some time in the future. Profile 1. The simplest radios produce sound, scrolling text display for station name and limited messaging - characteristics present on some FM radios and entrylevel DAB+ radios. Profile 2. As profile 1 with the addition of a colour display to show slide shows of pictures, an electronic program guide and a broadcast website browser so that the user can select pages from the broadcasters’ website. It is also possible that radio stations may allow you to download siliconchip.com.au Significant Australian Dates 1923 AM broadcasting started 1948 ABC Mono FM started 1961 ABC FM stopped, TV ch. 3-5 start 1975 FM stereo offered to the industry. Colour TV starts 1976 Community broadcasting stated 1977 ABC Classic FM started 1980 Commercial FM started 1987 DAB Invented 1992 ACMA started auctioning broadcast licences 1995 DAB Standards first published DAB trials in Canberra 1999 DAB trials started in Sydney 2003 DAB trials expanded and Melbourne added. Broadcast Australia suggests Advanced Audio Coding could be adopted for DAB. 2004 AAC+ V2 standardised. 2007 DAB+ standardised worldwide Aust Digital Radio Legislation passed 2009 Full time digital radio commences in mainland state capitals. 2011 DBCDE/ACMA review of DRM vs DAB+ for regional digital radio. 2029? siliconchip.com.au Closedown of AM & FM transmitters will require an Act of Parliament. The factors controlling this decision are; • The whole country is covered with digital signals. • Sufficient percentage of digital listeners • Greenhouse target August 2009  25 How the signals get to air: The Broadcasting Chain. This was explained in more detail in Parts 1 and 2 of this series (SILICON CHIP, February/March 2009). a music selection for a price. Profile 3. A DAB+ profile 2 radio with the addition of a Digital Mobile Broadcast (DMB) TV receiver. This system is in competition with DVB-Handheld system which has been trialled in Sydney on TV channel 29. Mobile TV You might be wondering why DAB+ would want to be used to transmit TV signals, After all, DAB+ is radio and TV is TV, right? Not quite! The digital age means re-thinking many traditional boundaries between TV and radio when digital technology is being used. One of those changes is mobile TV – or more correctly, TV reception on mobile devices. We’ve all seen the adverts (on TV, of course!) where (some) TV programs can be received by mobile phones and PDAs, etc. These use the 3G phone network, just one way to transmit TV to these devices. Unfortunately 3G is also the most expensive method – and coverage is limited. Another method is DVB-H which is a ruggedised version of our existing TV signal but with less-sharp images than SD TV. It uses MPEG4 compression (as used by Foxtel HD, NZ terrestrial digital TV) so that a total of 20 programs can be transmitted by a single TV transmitter. Some of the programs are encrypted so you have to pay for them. It doesn’t use the phone system – a single 7MHz TV channel is used for this service. 26  Silicon Chip Yet another development is DMB (Digital Multimedia Broadcasting) which uses band-3 VHF to transmit a single MPEG4-compressed TV program as above. The receiver may be a specific radio with a screen or a mobile phone/PDA etc with a DMB digital radio receiver. The picture quality is similar to DVB-H. This system is used in Korea and in Norway. The use of band 3 VHF makes the signal more reliable. All new DAB+ receivers can decode the sound but for the TV pictures you need a profile 3 digital radio. The idea is to be able to watch sport at the game or elsewhere while mobile. Australia is not proposing the introduction of DMB at this point. It will need to wait until the analog TV switch off to make more band 3 channels available for radio. The last method, as we alluded to above with Profile 3, is to use DAB+ with its many advantages. Broadcast licence categories There is one transmitter per DAB+ channel, hence one licence. Category 1: Commercial broadcasters are allocated 896kbit/s, so that 7 broadcasters get 128kbit/s each. Wide-area community broadcasters have been allocated a total of 256kbit/s. Category 2: A mixture of commercial, national and community broadcasters. Category 3: All national broadcasters (ABC & SBS). The ABC has 768kbit/s and SBS 384kbit/s. The programs to be available initially will be all existing ABC services, siliconchip.com.au Dig music, Dig Jazz, Dig Country and SBS1 and SBS 2 Brisbane, Sydney & Melbourne have two Category 1 and one Category 3 licences each. Adelaide & Perth only have a Category 1 and a Category 3 licence each. A licence is for 2.25 Mbit/s of which 1.152 Mbit/s is available for data. This gives commercial broadcasters 128kbit/s each. How each broadcaster uses their allocation is up to them. For example some broadcasters will use it for two stereo sound programs at 64kbit/s each. Sport broadcasters may wish to transmit one stereo sound program, results service and a slideshow showing the finish of races. A broadcaster in the future may wish to transmit a single 5.1 surround sound program of higher quality. The broadcaster can change their configuration at will. Sound transmission characteristics All broadcasters are likely to use Spectrum Bandwidth Replication (SBR). We covered this in detail in part 2 but briefly, it is a method where high pitch sounds are not transmitted. They are recreated from the lower pitched sounds through the use of these sounds and a control signal which determines how much high pitched recreation to use. SBR allows you to almost halve the amount of data required for transmission, which in turn allows more programs per radio channel. For rates of 48kbit/s or less Parametric Stereo is a must. Sound bit rates are likely to vary from 48-96kbit/s depending on the broadcaster – although higher and lower rates are technically available if required. These rates can be dynamically configured. Some receivers display the bit rates. Comparison of transmission systems AM radio: • Not available on most DAB+ receivers, portable audio devices & mobile phones. • Sounds duller due to a lack of high frequencies due to inadequate design in virtually all AM tuners and radios. • Limited dynamic range due to the presence of noise • Higher distortion, again due to inadequate tuner design. • Suffers from interference from lightning and electrical switching • Fading at dawn and dusk near the edge of the coverage area. • Co-channel and adjacent channel interference, especially at night • 9kHz whistling (again due to adjacent channel interference).   FM radio: • Most broadcasters process the sound to make it as loud as the other broadcasters. So there is little variation in volume and a lack of “sparkle” on loud sounds because of the pre-emphasis required in an FM transmitter. • Hiss and a lack of sound direction, when signals are weak (weak signals mean the receiver switches to mono). • Fuzzy sound with little spread of sound sources due to reflected FM signals (multipath distortion). DAB+: • Sound processing has to be used with care when combined with an AAC+ V2 encoder, which does its own processing. • More variation of loudness is likely to liven up the programs. • Sound quality is determined by the bit rate used for the DAB+ Digital Radio Receiver – now available from Av-Comm ONL Y $149 PLU .00 S P& P Av-Comm’s Q4000 DAB+ receiver is the result of over 12 months product development and market research. Rather than releasing a non-compatible DAB receiver which could have been used during early on-air testing, the company chose to wait until the DAB+ standard was formalised. Originally intended to combine the features of DAB+, FM with RDS and Internet radio, the results of Av-Comm’s market research indicated that different demographics exist for DAB+ and Internet radio. The result is the Q4000 which is purely a DAB+ receiver. It has a clock and alarm functions, with snooze, allowing it to be used as a bedside clock radio. Priced at just $149 (plus P&P), the receiver represents an affordable entry point into the world of Digital Radio. The unit is capable of running from 6 AA (internal) batteries but is supplied with a bonus 9V regulated DC power supply for mains operation. For those technically minded, the important specs are: RF Input Frequency Range: 174.928-239.2MHz Sensitivity: -100dBm Power supply: 9V DC, 800mA DAB+ channels: 5A,B,C,D, 6A,B,C,D, 7A,B,C,D, 8A,B,D,C, 9A,B,C,D, 10A,N,B,C,D, 11A,B,C,D, 12A,B,C,D, 13A,B,C,D,E,F. EXCLUSIVELY FROM: BE ONE OF THE FIRST T O EXPER IENCE THE BRI LLIANCE OF DAB+! Av-Comm Pty Ltd 24/9 Powells Rd, Brookvale, NSW, Australia (PO Box 225 Brookvale, NSW 2100) Phone: (02) 9939 4377    Fax: (02) 9939 4376   Website: www.avcomm.com.au siliconchip.com.au August 2009  27 sound program channel. Noise in the transmission path is not audible; if it causes too many errors the receiver mutes itself. • It is a typical digital system. It is either good quality, it breaks up or is non-existent. Coverage area The coverage area will be limited to the licence area designated by the ACMA. So for the mainland capitals it will be limited to the metropolitan areas. This means that the coverage is designed to minimise spillover into the adjacent licence areas such as: Sunshine Coast, Gold Coast, Central Coast, Illawarra, Geelong, and Mandurah. Once analog TV is switched off in the mainland capitals then these non-metro areas can get DAB+ local stations. All transmissions in a given licence area are radiated from a single antenna so all programs will have the same coverage area. The terrain in Sydney and the skyscrapers in Sydney and Melbourne are producing some areas of poor reception. So a low-power TV transmitter will be used to repeat all DAB+ channels in these areas. This will produce a Single Frequency Network. SFNs are used in digital TV on some of the same sites. How the signals get to air This was covered in much more detail in parts 1 & 2 but for readers who missed those parts, a brief recap. Read this in conjunction with the diagram on page 26. The microphones pick up the sound and/or uncompressed pre-recorded sound is fed into the mixing desk. The on-air studio desk output is AAC+ V2 compressed and the Program Associated Data is added. A sound program from other on-air studios or recorded content can be added in the same DAB+ encoder system. The resulting signal is called “Service Transport Interface” (STI) and contains all the signals from a single broadcaster. If the transmitter is in the same city as the Master Studio then the STI signal is fed into a local Ensemble Multiplexer. If the transmitter is in a remote city then the STI signal is delayed to match the time zone and is fed into a redundancy switch. The switch allows the remote studio to be out of the circuit when the program is coming from the master studio. If a local program is being inserted then the redundancy switch is told to switch inputs. Another redundancy switch can be used to bypass the delay for live inserts. The remote studio is identical to the master studio including the data server. The reason for using a Redundancy switch is that it will ensure the time stamp is correct and the switch occurs at the end of a super frame. If this is not done the receiver will have to re-synchronise which will cause silence for four seconds. The Ensemble multiplexer continuously, sequentially switches through 32 audio/data streams and adds the synchronising signals, Fast Information Channel Data (Inputs not shown), generates and inserts all the error correction data as well as performing the data shuffling. The transmitter contains the COFDM modulator, frequency up-converter to the transmission frequency and the 28  Silicon Chip power amplification. The signal is then fed to the antenna at the top of the tower. Redundancy The system shown on the diagram is duplicated so that in event of failures the worst that can happen is a small drop of power. This assumes that the transmitter building and/or tower are not destroyed. At strategic points in the chain after the DAB+ encoder, more redundancy switches are used to switch around faulty units. Monitoring the system. The Service Provider Controller computer on each “TXA” transmitter site collects the alarm status and data of the equipment on that site. The status is sent to Broadcast Australia’s control centre in Sydney, via a wide area network. This control centre can also send commands to the redundancy switches and all other equipment on the site. Transport monitor This device will measure the error rates in the signal and check the error correction coding so that the SPC can report problems. It also contains a broadcast standard decoder, which can be used to feed analog signals to either an FM or an AM transmitter. Signal distribution If you wish to send your signals interstate you have two choices: (A) An uncompressed signal such as 3.072Mbit/s for a single AES stereo audio and no programme associated data. (B) A compressed signal, such as 128kbit/s for an STI signal containing one or two stereo programs and embedded program associated data. This reduces you link costs. The only warning is that you cannot encode/decode/encode again, hence the use of switching mentioned above. Signal storage 1.3824TByte/hour for a single AES Stereo sound signal without embedded PAD (Program Associated Data). 57.6Mbyte/hour for an AAC+ V2 signal of 128kbit/s and containing embedded PAD data. The advantage of embedded data is that it always matches the surrounding program and is appropriate to the time when the sound was sampled. The use of DAB+ signals in STI or ETI form for distribution drastically reduces the distribution costs and stereo sound is included. Conclusion City listeners can now enjoy the benefits of digital radio. The next trial sites are likely be Hobart or Townsville. As the analog TV shutdown will commence next year and be completed by the end of 2013 it is hoped that some rollout of DAB+ transmissions will be possible during this timetable in non-metro areas. Remote area listeners may have to wait for the results of the DRM review sometime in 2011. As the use of DAB+ and DRM expands worldwide (except in the USA), then the price of receivers should keep dropping after the development costs have been returned to the manufacturers. For up to date information on digital radio check www. digitalradio.com.au SC siliconchip.com.au