XM has applied for a U.S. patent on a new method of FM modulation. Currently most cars do not include any kind of an auxiliary jack, so the method of choice for satellite radio is through FM transmission to the existing car stereo. The problem that occurs is that the nice, beautiful digital signal coming from those satellites in the sky are converted to an analog signal when transmitted over FM. This is causing a conflict between sound quality and convenience.
The patent that XM has applied for would utilize HD Radio by transmitting the satellite radio signal in-band over carrier digital audio broadcast. Wait, so XM is applying for a patent that uses HD Radio, a competitor? Whatever works, I guess.