Jutta,
Thanks for the information:
The patent I've seen investigated in connection with GSM 06.10
and Philips is the older 4,932,061 (1990)....
Interesting. The priority date of that one is 22 March 1985.
The practice of quantizing residual exitation in LPC vocoders was
not novel in 1985. For an example of how people were performing
VQ classification on the exitation residual much earlier, see:
"Epoch extraction from linear prediction residual for
identification of closed glottis interval", by T. Ananthapadmanabha
and B. Yegnanarayana, in IEEE Transactions on Acoustics, Speech,
and Signal Processing, vol. 27, no.4, pp. 309-19 (1979).
Certainly the methods of doing such quantization described in the
claims of patent 4,932,061 are novel, because they all explicitly
refer to "perceptually weighting" the exitation residual. However,
GSM 6.10 uses only four quantization vectors and a linear scaling
factor, without any weighting based on non-linear perceptual
modeling, so that particular set of claims do not apply to GSM 6.10.
It also might be helpful to look at the references in the these
GSM 6.10 descriptions published prior to ETSI's:
"Evolution of Six Medium Bit rate Coders For The Pan-European
Digital Mobile Radio System", by E. Natvig, in Journal On Selected
Areas In Communications, vol. 6, no. 2, pp 324-34 (1988).
"Speech Codec for the European Mobile Radio System", by K. Hellwig,
P. Vary, D. Massaloux, and J.P. Petit, in Proceedings of the
ICASSP-88, pp. 227 (April, 1988).
Cheers,
James