The languishing state of digital audio broadcasting in the United States following its introduction more than two years ago has spurred the nation’s largest broadcast conglomerates to form an “HD Digital Radio Alliance” to facilitate the bona-fide rollout of digital service. Key to this campaign is the coming of what the Alliance calls “HD2 multicast sidechannels.”
The ability to broadcast multiple program streams on a single radio channel is relatively new to the U.S. digital radio environment. As initially developed over the last 15 years (!) the dominant U.S. digital radio protocol, now known as “HD Radio,” did not accommodate a multicasting feature: National Public Radio spearheaded its creation less than three years ago.