Pilot tone aided QPRS systems for digital audio broadcasting

For fast fading channels, a spectrally efficient technique than can achieve more than 2 b/s/Hz with a built-in fade canceler is proposed. Recent studies show that fading in digital mobile communications can be canceled by adding redundant bits to the customer data or with pilot-aided techniques. This concept is extended to a more spectrally efficient class-IV quadrature partial response signaling (QPRS) system. However, in such schemes if the pilot is corrupted by the phase noise caused by the pilot-data interference, the fade cancellation will not effectively remove the error floor. The class-IV system has an inherent advantage in that it has a spectral null at DC and a low energy content at the ends of the band. Such systems also have a higher speed tolerance. It is shown that a small bandwidth around DC can be vacated to insert the pilot. Preliminary results show that residual error floor can be reduced from 10^-2 to 10^-5 in fast fading channels