Finite-state vector quantization over noisy channels and its application to LSP parameters

The authors describe a noisy channel finite-state vector quantizer (FSVQ) for quantizing speech line spectrum pair (LSP) parameters. First they show that under noiseless channel conditions, the ordinary FSVQ of J. Foster et al (1985), when used to encode the LSP parameters, achieves a 1-dB average spectral distortion at 24 b/frame; each LSP vector is split into three subvectors and an eight-state FSVQ is used for each subvector. However, when channel noise is present, the ordinary FSVQ performance degrades drastically. Therefore, the authors describe a modified FSVQ system that is designed taking into account the channel noise. It is shown by means of simulations that the new system is robust to channel noise and outperforms the channel-optimized VQ and the channel-matched multistage VQ of N. Phamdo et al, (1990) by saving 1.5-4 b/vector, depending on the level of noise in the channel