Editing In-band on-channel (section)

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

===HD Radio Broadcasting===
The first, and 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 widely used system, with approximately 1,560 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.

===FMeXtra===
The other system is [[FMeXtra]] by Digital Radio Express, which instead uses subcarriers within the existing signal. This system was introduced more recently. The FMeXtra 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 restrict listening with [[conditional access]] and [[encryption]].

===DRM===
[[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>

Like HD Radio, it can be [[backwards compatible]] with existing FM receiver equipment receiving the analog signal, with side-band<ref>{{Cite web|url=http://www.etsi.org/deliver/etsi_ts/102500_102599/102509/01.01.01_60/ts_102509v010101p.pdf|title=See section 5: "DRM/AM single channel simulcast"}}</ref> broadcasts digitally encoded using HE-AAC or [[xHE-AAC]] received on compatible devices, this ability to operate within the internationally agreed FM spectrum of 88-108&nbsp;MHz makes DRM a viable candidate for future adoption if countries begin to eliminate their analog broadcasts.