While Canada and most countries in Europe have chosen the Eureka 147 standard for creating digital radio service, the United States has been holding out for advancements in IBOC technology, now under the direction of Ibiquity. Part of the reason is the use of the L band (1452–1492 MHz) for test-flight telemetry, by the U.S. military and its contractors. This band is used in Canada for digital radio, but remains unavailable for reassignment by the NTIA in the U.S. for broadcasting. It is also partly because of concern that stations' branding, using their current frequency, would be lost to new channel numbers — and that several stations must share a transmitter which multiplexes them all into one ensemble with the same coverage area. A further concern to FM stations was that AM stations could suddenly be in competition with the same high audio quality.
IBOC in the U.S. still faces some serious technological challenges of its own, including interference with other stations, and poor audio quality likened by some to being underwater. Ibiquity was previously using PAC (also used at a higher bitrate in Sirius satellite radio [see DARS]), but as of 2003August 12 a switch to HDC was made to rectify these problems. Prior to this, a change back to AAC or another MPEGcompression algorithm had been considered; however HDC has been customized for IBOC, and it is also likely that the patent rights for every transmitter and receiver can be retained longer by creating a more proprietary system. Digital Radio Mondiale is also developing a patent-free IBOC system, likely to be used worldwide with AM shortwaveradio, and possibly with broadcast AM and FM.
In-band on-channel radios are being marketed under the brand HD Radio, to highlight the quality of reception. Limited receivers are now available, bearing the HD Radio brand.
IBOC does allow for multiple channels, though this means taking some existing subcarriers off the air to make additional bandwidth available.
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.
It should be noted that the term 'iboc' is not exclusive to any one digital radio system (DigitalAudio Broadcasting, DigitalRadio Mondiale, HD Radio or others), although each may use a proprietary and incompatible implementation.
Part of the reason is the use of the L band (1452–1492 MHz) for test-flight telemetry, by the U.S. military and its contractors.
IBOC in the U.S. still faces some serious technological challenges of its own, including interference to other stations, and poor audio quality likened by some to that of being underwater.
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