Multistream transmission for hybrid IBOC-AM with embedded/multidescriptive audio coding

Hybrid In Band on Channel (IBOC) digital audio broadcasting simultaneously with analog amplitude modulation (AM) has been proposed as a hybrid solution to digital audio broadcasting in the AM band. Since the AM band is crowded and since the available bandwidth per program is limited, adding digital transmission is a challenging proposition. To achieve FM like audio quality, an audio coder rate of 32-64 kb/sec may be required. One of the currently proposed hybrid IBOC-AM systems is 30 kHz wide. Severe second adjacent interference may occur in certain geographical. areas. This may lead to loss of 40% of the effective transmission audio bit rate. For coping with such harsh transmission conditions, we present a solution based on embedded/multidescriptive audio coding with matched multistream transmission in separate frequency bands. With loss of one frequency band, the embedded system blends to a lower audio coder rate with a much better quality than analog AM. The nonembedded system without multistream transmission fails catastrophically when a little more than one sideband is severely interfered with causing a severe discontinuity in quality while blending directly to analog AM. A number of detailed robust embedded systems are outlined. We also show how multistream transmission schemes can be used with nonembedded audio coders. Both daytime and nighttime scenarios are included. This paper contains a catalog of possible systems for different audio quality levels and interference scenarios, including systems with 20 kHz bandwidth rather than 30 kHz.