In-band on-channel: Difference between revisions

{{refimprovemore citations needed|date=November 2008}}

'''In-band on-channel''' ('''IBOC''') is a hybrid method of transmitting [[digital radio]] and analog radio [[Broadcasting|broadcast]] [[Signalling (telecommunication)|signal]]s [[simulcast|simultaneously]] on the same [[frequency]]. The name refers to the new digital signals being broadcast in the same [[AM radio|AM]] or [[FM radio|FM]] band (in-band), and associated with an existing radio channel (on-channel). By utilizing additional digital [[subcarrier]]s or [[sideband]]s, [[Digital data|digital]] information is [[Multiplexing|multiplexed]] on existing signals, thus avoiding [[frequency allocation|re-allocation]] of the broadcast bands.

IBOCDigital doesradio allowstandards forgenerally allow multiple program channels, thoughto be multiplexed into a single digital stream. In North American FM, this cannormally entailallows takingtwo or three high-fidelity signals combined in one channel, or one high-fidelity signal plus several additional channels at medium-fidelity levels that are much higher quality than AM. For even greater capacity, some existing subcarriers can be taken off the air to makeprovide additional [[Bandwidth (signal processing)|bandwidth]] available in the modulation [[baseband]]. On FM for instance, this could eventuallymight mean removing [[stereophonic sound|stereo]] from the analog signal, relying on the digital signal to provide stereo where desired, thus making room for another digital channel. OnDue to the reduced bandwidth in AM, IBOC is [[wikt:incompatible|incompatible]] with analog stereo, andalthough anythat is rarely implemented, and additional channels are limited to highly compressed voice, such as [[traffic]] and [[weather]]. Eventually, stations can go from [[HD Radio|hybrid]] mode (both analog and digital) to all-digital, by eliminating the baseband [[Monaural|monophonic]] audio.

On FM there are currently three methods of IBOC broadcasting in use, mainlyprimarily in the [[United States]].

The first, and currently only, digital technology approved for use on AM and FM broadcast frequencies by the [[Federal Communications Commission]] in the United States, is the proprietary [[HD Radio]] system developed by [[iBiquity]] Digital Corporation,<ref>{{cite web |url=http://www.fcc.gov/mb/audio/digital.html |title=FCC digital radio broadcasting |work=United States [[Federal Communications Commission]], audio division |access-date=2010-06-29 |archive-url=https://web.archive.org/web/20100615162704/http://www.fcc.gov/mb/audio/digital.html |archive-date=2010-06-15 |url-status=dead }}</ref> which transmits energy beyond the allotted ±100&nbsp;kHz FM channel. This creates potential interference issues with adjacent channels.<ref>{{cite web |url=http://www.nrscstandards.org/SG.asp |title=NRSC 5B of April 2010 |work=[[National Radio Systems Committee]] |access-date=2010-06-29 |archive-url=https://web.archive.org/web/20100528032334/http://www.nrscstandards.org/SG.asp |archive-date=2010-05-28 |url-status=dead }}</ref> This is the most widespreadwidely used system in use, with approximately 1,556560 stations transmitting HD radio in the US,<ref>{{cite web|url=http://licensing.fcc.gov/cgi-bin/ws.exe/prod/cdbs/pubacc/prod/sta_list.pl?Service=FM&digital_status=H |title=FCC digital radio broadcasting FM stations list |work=United States [[Federal Communications Commission]], audio division }}</ref> plus over 800 new multicast channels (as of Jan 2010). There is a one-time license fee to iBiquity Digital, for the use of its intellectual property, as well as costs for new equipment which range from $50,000 to $100,000 US (2010) per station.

The other system is [[FMeXtra]] by Digital Radio Express, which instead uses subcarriers within the existing signal. This system was introduced more recently. The systemFMeXtra is compatible with HD Radio in hybrid mode, but not in all-digital mode, and with [[RBDS]]. The stereo subcarrier can be removed to make more space available for FMeXtra in the modulation baseband. However, the system is not compatible with other existing 67–92&nbsp;kHz subcarriers which have mostly fallen into disuse. The system is far less expensive and less complicated to implement, needing only to be plugged into the existing [[Transmitter#Power output|exciter]], and requiring no licensing fees. FMeXtra has generally all the user features of HD Radio, including multicast capability;, the ability to broadcast several different audio programs simultaneously. It uses the [[aacPlus]] (HE-AAC) codec.

FMeXtra can controlrestrict listening with [[conditional access]] and [[encryption]].

[[Digital Radio Mondiale]] allows for simultaneous transmission of multiple data streams alongside an audio signal. The DRM mode for VHF provides bandwidths from between 35 &nbsp;kbit/s to 185 &nbsp;kbit/s and up to four simultaneous data streams, allowing 5.1 surround [[DVD]] quality audio to be broadcast alongside other multimedia content - images, video or HTML content are typical examples.<ref>{{Cite web|url=http://www.owdjim.gen.nz/chris/radio/DRM/|title = DRM - Digital Radio Mondiale - Reception in New Zealand}}</ref>

While it is not backwardly[[backwards compatible]] with existing FM receiver equipment, with broadcasts digitally encoded using HE-AAC or [[xHE-AAC]], this ability to operate within the internationally agreed FM spectrum of 88-108&nbsp;MHz makes DRM a viable candidate for future adoption whenif countries begin to switch offeliminate their analogueanalog broadcasts.

iBiquity also created a [[mediumwave]] HD Radio system for AM, which is the only system approved by the Federal Communications Commission for digital AM broadcasting in the United States.<ref>{{cite web |url=http://www.fcc.gov/mb/audio/digital.html |title=FCC digital radio broadcasting |work=United States [[Federal Communications Commission]], audio division |access-date=2010-06-29 |archive-url=https://web.archive.org/web/20100615162704/http://www.fcc.gov/mb/audio/digital.html |archive-date=2010-06-15 |url-status=dead }}</ref> The HD Radio system employs use of injected digital sidebands above and below the audible portion of the analog audio on the primary carrier. This system also phase modulates the carrier in [[quadrature phase|quadrature]] and injects more digital information on this phase-modulated portion of the carrier. It is based on the principle of [[AM stereo]] where it puts a digital signal where the [[C-QUAM]] system would put the analog stereo decoding information.

Digital Radio Mondiale has had much more success {{Citation needed|date=October 2008}} in creating an AM system, and one that could be much less expensive to implement than any [[Proprietary protocol|proprietary]] HD Radio system, although it requires new frequency. It is the only one to have been accepted mediumwave but also [[shortwave]] (and possibly [[longwave]]) by the [[International Telecommunication Union]] (ITU) for use in regions I and III, but not yet in region II, the [[Americas]]. The HD Radio system has also been approved by International Telecommunication Union.

[[CAM-D]] is yet another method, though it is more of an extension of the current system. Developed by AM stereo pioneer [[Leonard R. Kahn]], It encodes the [[Clef#Treble clef|treble]] on very small digital sidebands which do not cause interference to adjacent channels, and mixes it back with the analog baseband. Unlike the other two, it is not intended to be capable of multichannel, opting for quality over quantity. Unlike the HD system iBiquity calls "hybrid digital" the CAM-D system truly is a direct hybrid of both analog and digital. Some engineers believe that CAM-D may be compatible with analog AM stereo with the right engineering.

While the United Kingdom and many other countries have chosen the Eureka 147 standard of digital audio broadcasting (DAB) for creating a digital radio service, the United States has selected IBOC technology for its digital AM and FM stations. The band commonly used for terrestrial DAB is part of VHF band III, which does not suffer from L-band's significant line-of-sight problems. However, it is not available in North America since that span is occupied by TV channels 7 to 13 and the amateur radio 1.25 meter (222&nbsp;MHz) band. The stations currently occupying that spectrum did not wish to give up their space, since VHF offers several benefits over UHF: relatively lower power, long distance propagation (up to 100 miles (160&nbsp;km) with a rooftop antenna), and a longer wavelength that is more robust and less affected by interference. In Canada, the Canadian Radio-television and Telecommunications Commission (CRTC) is continuing to follow the analog standard, so the channels remain unavailable there as well. HD Radio testing has been authorized in Canada, as well as other countries around the world.

There was also concern that AM and FM stations' branding, using their current frequencies, would be lost to new channel numbers, though virtual channels such as on digital television would eliminate this. Also, several competing stations would have to share a transmitter that multiplexes them all into one ensemble with the same coverage area (though many FM stations are already diplexed in large cities such as New York). [https://web.archive.org/web/20110725192711/http://www.esbnyc.com/tourism/tourism_facts_broadcasting.cfm] A further concern to FM station operators was that AM stations could suddenly be in competition with the same high audio quality, although FM would still have the advantage of higher data rates (300 &nbsp;kbit/s versus 60 &nbsp;kbit/s in the HD Radio standard) due to greater bandwidth (100&nbsp;kHz versus 10&nbsp;kHz).

The most significant advantage for IBOC is its relative ease of implementation. Existing analog radios are not rendered obsolete and the consumer and industry may transition to digital at a rational pace. In addition, the technology infrastructure is in place: most major broadcast equipment manufacturers are implementing IBOC technology and 60+ receiver manufacturers are selling IBOC reception devices. In the UK, Denmark, Norway and Switzerland, which are the leading countries with regard to implementing DAB, the first-generation [[MPEG-1 Audio Layer II]] (MP2) codec stereo radio stations on DAB have a lower sound-quality than FM, prompting a number of complaints.<ref>{{cite web|url=http://wo.uio.no/as/WebObjects/theses.woa/wa/these?WORKID=52348 |last=Holm |first=Steve |publisher=Digitale Utgivelser ved UiO |title=Lydkvalitetet i DAB digitalradio |year=2007 |access-date=2009-01-03 |url-status=dead |archive-url=https://web.archive.org/web/20080501073857/http://wo.uio.no/as/WebObjects/theses.woa/wa/these?WORKID=52348 |archive-date=2008-05-01 }} ([[Nynorsk|Norwegian]])</ref> The typical bandwidth for DAB programs is only 128 &nbsp;kbit/s using the first generation CODEC, the less-robust MP2 standard which requires at least ''double'' that rate to be considered near-CD quality.<ref>{{cite web |url=http://www.david.robinson.org/commsbill/#1_2_3 |work=OFCOM: Regulation in digital broadcasting: DAB digital radio bitrates and audio quality; Dynamic range compression and loudness |title=DAB sound quality |last=Robinson |first=David J. M. |date=2002-07-09 |access-date=2009-01-03 |url-status=dead |archive-url=https://web.archive.org/web/20080708211612/http://www.david.robinson.org/commsbill#1_2_3 |archive-date=2008-07-08 }}</ref><ref>{{cite conference |url=http://www.ebu.ch/CMSimages/en/tec_doc_t3296_tcm6-10497.pdf |format=PDF|title=EBU subjective listening tests on low-bitrate audio codecs |publisher=EBU * UER |last=Kozamernik |first=Franc |date=June 2003 |access-date=2009-01-03 |archive-date=2007-02-16 |archive-url=https://web.archive.org/web/20070216071801/http://www.ebu.ch/CMSimages/en/tec_doc_t3296_tcm6-10497.pdf |url-status=dead }}</ref>

An updated version of the Eureka-147 standard called DAB+ has been implemented. Using the more efficient high quality MPEG-4 CODEC HE-AAC v2, this compression method allows the DAB+ system to carry more channels or have better sound quality at the same bit rate as the original DAB system. It is the DAB+ implementation which will be under consideration for new station designs and not the earlier DAB scheme using the MUSICAM CODEC. The DAB+ system was coordinated and developed by the World DAB Forum, formed in 1997 from the old organization. It gives the Eureka-147 system a similar quality per bit rate as the IBOC system and hence (arguably) a better sound quality than FM.<ref>{{Cite web |url=http://www.worlddab.org/introduction_to_digital_broadcasting/dab_plus_digital_radio |title=DAB+ - Upgrade to DAB Digital Radio - The World DAB Forum |access-date=2009-10-21 |archive-url=https://web.archive.org/web/20091015132028/http://www.worlddab.org/introduction_to_digital_broadcasting/dab_plus_digital_radio |archive-date=2009-10-15 |url-status=dead }}</ref>

AM IBOC in the United States still faces some serious technological challenges of its own, including nighttime interference with other stations. iBiquity wasinitially used an audio compression system previouslyknown usingas PAC (also used at a higher bitrate in Sirius satellite radio, see [[Digital Audio Radio Service]]), but in August 2003 a switch to HDC (based-upon ACC) was made to rectify these problems. HDC has been customized for IBOC, and it is also likely that the patent rights and royalties for every transmitter and receiver can be retained longer by creating a more proprietary system. Digital Radio Mondiale is also developing an IBOC system, likely to be used worldwide with AM shortwave radio, and possibly with broadcast AM and FM. Neither of those have been approved yet for ITU region 2 (the Americas). The system, however, unlike HD Radio, does not permit the existing analog signal and the digital signal to live together in the same channel. DRM requires an additional channel to maintain both signals.

Both AM and FM IBOC signals cause interference to adjacent-channel stations, but not within the station’sstation's interference-free protected contours designated by the U.S. [[Federal Communications Commission]] (FCC). It has led to derogatory terms such as IBAC (In-band adjacent-channel) and IBUZ (since the interference sounds like a buzz.) The range of a station on an HD Radio receiver is somewhat less than its analog signal. However, inIn June, 2008, a group of US broadcasters and equipment manufacturers requested that the U.S. FCC increase the permissible FM IBOC power from 1% (currently) to a maximum of 10% of the analog power. On January 29, 2010, the FCC approved the request.<ref>{{cite web |url=http://www.fcc.gov/fcc-bin/audio/DA-10-208A1.pdf |archive-url=https://wayback.archive-it.org/all/20140523212426/http://www.fcc.gov/fcc-bin/audio/DA-10-208A1.pdf |url-status=dead |archive-date=2014-05-23 |author=FCC |title=Digital power increase for FM stations approved. MM Docket No. 99-235, DA 10-208. |date=2010-01-29 |access-date=2010-02-26 }}</ref> In addition, tropospheric ducting and e-skip can reduce the range of the digital signal, as well as the analog.

In-band on-channelIBOC digital radios using iBiquity's standard are being marketed under the brand "HD Radio" to highlight the purported quality of reception. As of June 2008, over 60 different receiver models have been made, and stations have received blanket (no longer individual and experimental) authorization from the U.S. FCC to transmit in a multiplexed multichannel mode on FM. Originally, the use of HD Radio transmission on AM was limited to daytime only, and not allowed at night due to potential problems with skywave radio propagation. The FCC lifted this restriction in early 2007. DRM, however, is being used across Europe on shortwave, which is entirely AM skywave, without issue. With the proper receiver, many of those stations can be heard in North America as well, sans the analog signal.

Government broadcaster BETAR began broadcasting HD Radio on their 100.0&nbsp;MHz frequency on 9 November 2016 from their Agargaon site in Dhaka. The transmission uses a 10&nbsp;kW GatesAir system. The 100.0&nbsp;MHz carries programs from [[BBC World Service]] amongst others. HD 1, 2, 3 and 4 are configured. A second transmission will also have HD radio added on 88.8&nbsp;MHz from the same site.

=== Brazil ===

After having [[L-band]] DAB for several years, the [[Canadian Radio-Television and Telecommunications Commission]] (CRTC) and [[Canadian Broadcasting Corporation]] (CBC) have also looked at the use of HD Radio, given its gradual progress in the neighbouring U.S. The CBC began HD Radio testing in September 2006, focusing on transmissions from [[Toronto]] and [[Peterborough, Ontario]].{{citation needed|date=November 2013}} The CRTC has since revised its policy on digital radio to allow HD Radio operations.<ref>[http://www.crtc.gc.ca/eng/archive/2006/pb2006-160.htm Public Notice CRTC 2006-160]</ref>

All Mexican radio stations [[Border blaster|within 320 km of the U.S. border]] are allowed to transmit their programs on the AM and FM bands utilizing HD Radio technology. Approximately six Mexican AM and FM stations are already operating with HD Radio technology along Mexico’s border area with the US. Grupo Imagen commenced HD Radio transmissions on XHDL-FM and XEDA-FM as well as Instituto Mexicano de la Radio on XHIMR-FM, XHIMER-FM and XHOF-FM in Mexico City in June 2012.

HD Radio transmission in Auckland, New Zealand was started on October 19, 2005. The frequency of IBOC HD radio is 106.1&nbsp;MHz. The transmitter is located at Skytower. Following successful testing, the Radio Broadcasters Association (RBA) initiated a comprehensive trial of HD Radio technology in December 2006. The aim of the trial was to assess the coverage potential of the HD Radio system and to make a recommendation on the suitability of the technology for adoption.

WPRM FM is the first station in San Juan, Puerto Rico (part of the US) to adopt HD Radio, in April 2005. WRTU in San Juan has also commenced broadcasting in HD Radio technology in 2007.

Radio Sunshine has now switched to DAB+ <ref>{{cite web |url=http://www.sunshine.ch/dynasite.cfm?dsmid=98472 |title=Radio Sunshine :: Mehr Musik - mehr Abwechslung! |website=www.sunshine.ch |url-status=dead |archive-url=https://web.archive.org/web/20110510142126/http://www.sunshine.ch/dynasite.cfm?dsmid=98472 |archive-date=2011-05-10}} </ref>

DAB+ penetration in Switzerland has now reached 99.5% as of 2018.<ref>{{Cite web |url=http://www.worlddab.org/country_information_/switzerland |title=ArchivedWorldDMB copy- Country Information for DAB, DAB+ and DMB - Switzerland |access-date=2013-05-09 |archive-url=https://web.archive.org/web/20130808131645/http://www.worlddab.org/country_information_/switzerland |archive-date=2013-08-08 |url-status=dead }}</ref>

The first FM HD Radio broadcasts in KievKyiv went on the air in October 2006 on two FM stations operated by the First Ukrainian Radio Group.

As of May 2007, FMeXtra is on several dozen stations. Several hundred stations belonging to the [[Idea Bank]] [[consortium]] will also have FMeXtra installed. [http://www.dreinc.com/company/pr/4_14_06.html]