In Band On Channel (IBOC), competing with Digital Audio Broadcast
(DAB), is the US base technology for HD radio. The difference to Digital Audio Broadcast is the channel conditioning.analogue, frequency-modulated FM broadcast signal. Both signals, the analogue and the digital, are transmitted on the same carrier frequency. The advantage is that the broadcasting equipment only needs to be slightly modified. IBOC uses Perceptual Audio Coding (PAC) for audio compression
. Because IBOC did not comply with the specified bandwidths in the U.S. and interfered with other broadcast stations, it was shut down several times regionally.