Speech bandwidth extension based on in-band transmission of higher frequencies

A new method for wideband speech transmission is proposed which is fully backwards compatible with narrowband telephone systems. For this purpose, a pitch-scaled version of the higher speech frequencies (4 - 6.4 kHz) is inserted into the previously “unused” 3.4 - 4 kHz frequency range of standard telephone speech. This operation is reverted at the decoder side. A consistently good wideband speech quality can be achieved, even after transmission over common codecs and codec tandems. The quality impact on the narrowband part of the signal is insignificant.