Waveform coding of voiceband data signals at 16 kb/s

The performances of three representative waveform coders (APC, ATC and SBC) are measured for the compression of voiceband data signals to 16 kb/s. Performance is evaluated with respect to four criteria: bit-error rate (BER), signal-to-quantization-noise ratio (SQR), critical data rate (Rc) and detection statistic dispersion figure (γ). The waveform coders pass low rate (0-1200 b/s) modem signals with adequate fidelity through a single encoding, but have difficulty with some medium rate (1200-4800 b/s) signals. An adaptive vector quantizer (ABCVQ) is proposed for voiceband data compression. The ABCVQ coder adapts to the energy and center frequency of a modem signal and employs four baseband codebooks to accommodate an ensemble of low and medium rate voiceband data signals. The ABCVQ coder outperforms the three waveform coders with respect to each of the four performance criteria for all modem signals tested.