Artificial bandwidth extension of telephony speech by data hiding

The current public switched telephone network (PSTN) is only able to deliver analog signals in a relatively narrow frequency band, about 300-3400 Hz. Such a bandwidth is so small that the intelligibility of speech frequently suffers from poor subjective quality. In order to improve the voice quality and intelligibility, it is proposed to use a data hiding technique to extend the PSTN channel bandwidth artificially. That is, the higher frequency components beyond the PSTN bandwidth are encoded and imperceptibly embedded into the narrowband signal. When the hidden signal is extracted at the receiver, wideband speech can be reconstructed with better perceptual quality. The advantage of the proposed scheme lies in that it is fully compatible with conventional end-user equipment, e.g., a plain ordinary telephone set (POTS). Experimental results show that the proposed scheme has a better performance than conventional bandwidth extension methods with speaker-independent training.