In-band on-channel

In-band on-channel

In-band on-channel (IBOC) is a method of transmitting digital radio and analog radio broadcast signals simultaneously on the same frequency.

By utilizing additional digital subcarriers or sidebands, digital information is "piggybacked" on a normal AM or FM analog signal, thus avoiding any complicated extra frequency allocation issues. However, by putting extra RF energy beyond the edge of the station's normally-defined channel, interference with adjacent channel stations is increased when using digital sidebands.

IBOC does allow for multiple program channels, though this can entail taking some existing subcarriers off the air to make additional bandwidth available in the modulation baseband. On FM, this could eventually mean removing stereo. On AM, IBOC is generally incompatible with analog stereo at all, and any additional channels are limited to highly-compressed voice, such as traffic and weather. Eventually, stations can go from hybrid mode (both analog and digital) to all-digital, by eliminating the baseband monophonic audio.

FM methods

On FM there are currently two methods of IBOC broadcasting in use, mainly in the United States.

HD Radio(TM) Broadcasting

The first, the only digital technology approved for AM and FM broadcasting by the Federal Communications Commission in the United States, is the HD Radio system developed by iBiquity Digital Corporation, which uses sidebands beyond the normal ±100 kHz FM channel. This is the most well-known and widespread system in use: with over 1,700 stations on the air int the US, plus over 800 new multicast channes (as of June 2008), 83 percent of Americans have access to HD Radio stations. It costs FM stations approximately $50,000 to $100,000 in new equipment to broadcast with the HD Radio system. There is also a one-time license fee to iBiquity Digital for the use of its intellectual property that varies around $25,000.


The other system is FMeXtra by Digital Radio Express, which instead uses subcarriers within the existing signal. This was introduced more recently, and consumer receivers are expected in 2008. The system is completely compatible with HD Radio in hybrid mode (but not in all-digital mode, which is not expected to be implemented for a very long time), 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 subcarriers, which are normally not used by the general public anyhow. The system is far less expensive and less complicated to implement, needing only to be plugged in to the existing 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 control listening with conditional access and encryption, though it has been officially implemented (as of May 2007).


Digital Radio Mondiale is in the initial stages of creating an open-source system for FM, though it may be too late to make a third system viable with two others already in place.

AM methods

HD Radio Broadcasting

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. The HD Radio system employs use of injecting 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 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 in creating an AM system, and one that could be much less expensive to implement than any 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 Kahn, It encodes the 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.

Critics of CAM-D point to several drawbacks: (a), being primarily analog, the system will be just as subject to artificial interference and noise as the current AM system; (b), there are virtually no receivers available for the system and at present, no major manufacturer has announced even the intention to begin production of them; and (c), the cost of retrofitting with CAM-D is more than that of simply buying a new, HD-ready solid state transmitter.


While the United Kingdom has 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 used for terrestrial DAB in the UK is 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. 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 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 among 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). [] A further concern to FM stations 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 kbit/s versus 60 kbit/s in the HD Radio standard) due to greater bandwidth (100 kHz versus 10 kHz).

The most significant advantage to 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.


AM IBOC in the United States still faces some serious technological challenges of its own, including nighttime interference with other stations. iBiquity was previously using 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’s FCC-designated interference-free protected contours. 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, in June, 2008, a group of US broadcasters and equipment manufacturers requested that the U.S. Federal Communications Commission (FCC) increase the permissible FM IBOC power from 1% (currently) to a maximum of 10% of the analog power. In addition, tropospheric ducting and e-skip can reduce the range of the digital signal, as well as the analog.

In-band on-channel 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. Federal Communications Commission (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.

IBOC around the world


HD Radio technology was tested in 2004 with initial trials in Buenos Aires. Further testing of the technology began in early 2007.


Trial and tests of HD Radio technology began in Sarajevo in March 2007.


HD Radio transmission in Brazil was started on September 26, 2005. The radio stations that use IBOC HD in Brazil are Radio Bandeirantes, Radio Globo, and RBS Group. A total of six stations – one FM and one AM from each group – are now transmitting in HD Radio. KISS FM in São Paulo is the first HD Radio station in Brazil. A total of 24 stations are broadcasting in Brazil as of June, 2008. A joint study by the government (ANATEL) and broadcasters’ associations (ABERT, AESP) is completed and awaiting government action to regulate HD Radio broadcasting in 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. The CRTC has since revised its policy on digital radio to allow HD Radio operations pursuant to Public Notice CRTC 2006-160.

Czech Republic

Initial testing of the HD Radio system commenced in Prague in February 2007.


In China, Hunan Broadcasting Company started FMeXtra transmissions in Changsha in April 2007, and plans to put others throughout the Hunan province. [1] SARFT (State Administration for Radio, Film and Television) is currently testing HD Radio in Beijing in contemplation for acceptance in that country.


Caracol Radio began testing of the HD Radio technology in both the AM and FM bands in early 2008.


In September 2007 the European HD Radio Alliance (EHDRA) was formed by broadcasters and other interested groups to promote the adoption of HD Radio technology by European broadcasters, regulators and standards organizations.


France began broadcasting an HD Radio signal in March 2006 and plans to multicast two or more channels. The radio stations that use IBOC HD in France are SIRTI and NRJ Group. The owner of the transmitter is Towercast. The frequency of IBOC HD radio is 88.2 MHz. In May 2006, The Towercast group added a single channel of digital audio on 93.9 MHz.


Radio Regenbogen began HD Radio operations on 102.8 MHz in Heidelberg on December 3, 2007 pursuant to government testing authority.


Forum Radio Jaringan Indonesia had tested IBOC HD transmission from March 2006 to May 2006. The IBOC HD station in Jakarta was Delta FM (99.1 MHz). In April 2006, Radio Sangkakala (in Surabaya), the first AM HD radio station in Asia, went on the air on 1062 kHz.


Radio Jamaica began operating full time with both HD Radio AM and FM signals in the city of Kingston in 2008.


All Mexican radio stations 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. Groupo Imagen commenced HD Radio transmissions on XHDL and XEDA in Mexico City in June 2008.

New Zealand

HD Radio transmission in Auckland, New Zealand was started on October 19, 2005. The frequency of IBOC HD radio is 106.1 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.


The first HD Radio station in the Philippines began broadcasting on November 9, 2005. The Philippines National Telecommunications Commission finalized its rules for FM digital radio operations on November 11, 2007.


An HD Radio trial began in Warsaw in 2006 in order to demonstrate the technology to local radio stations.

Puerto Rico

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.


FM testing sponsored by Radio Sunshine and Ruoss AG began in Lucerne in April 2006. HD Radio operations in Switzerland continue and are spotlighted each year during “HD Radio Days”, an annual gathering in Lucerne of European broadcasters and manufacturers for the purpose of discussing the rollout of the technology in Europe.


HD Radio transmission in Thailand was started in April 2006. Radio of Thailand had created a public IBOC HD radio network targeting mass transit commuters in Thailand's capital of Bangkok. To receive the broadcasts, more than 10,000 HD Radio receivers were installed in buses.


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


Voice of Vietnam (VOV) commenced AM and FM HD Radio transmissions in Hanoi in June, 2008 including multicasting, in anticipation of making HD Radio technology a standard.

United States

As of June 2008, more than 1,700 HD Radio stations were broadcasting 2,432 HD Radio channels. HD Radio technology is the only digital technology approved by the FCC for digital AM and FM broadcsting in the US. Over 60 different HD Radio receivers are on sale in over 12,000 stores nationwide, including Apple, Circuit City, Best Buy, Target, and Wal-Mart.

As of May 2007, FMeXtra is on several dozen stations. Several hundred stations belonging to the Idea Bank consortium will also have FMeXtra installed. []

ee also

* Digital Audio Broadcasting
* Digital Audio Radio Service

External links

* [ FCC info on IBOC]
* [ NSRC-5A IBOC Standard Specification]
* [ Stop IBOC Now!]
* [ IBOC interference recordings]

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