Abstract: A method of coding a sampled speech signal vector in an analysis-by-synthesis coding procedure includes the step of forming an optimum excitation vector comprising a linear combination of a code vector from a fixed code book and a long term predictor vector. A first estimate of the long term predictor vector is formed in an open loop analysis. A second estimate of the-long term predictor vector is formed in a closed loop analysis. Finally, each of the first and second estimates are combined in an exhaustive search with each code vector of the fixed code book to form that excitation vector that gives the best coding of the speech signal vector.

Abstract: In a TDMA cellular telephone system, an error concealment method provides parameter interpolation based on soft quality measures that will enhance the speech quality under bad channel conditions compared to prior methods of repeating previous voice data frames. Specifically, the soft technique of the present invention uses a weighted combination of previous and present frame parameters, where the weighting reflects the probability of error. The present invention will improve the masking of errors compared to hard actions based on a binary detection, especially when the binary detection fails or when the received frame is declared as being "good". The method can also utilize parameter based soft information without increasing the bitrate.

Abstract: A method and an arrangement for quality estimation when detecting an information frame, for instance a speech frame transmitted in a radio communication system in accordance with time division multiple access (TDMA), although the method can also be applied with frequency divided radio systems. There is used the soft information available in the radio receiver which is intended to detect the speech frame and process this signal information in accordance with those principles applicable to known neural nets. Prior to use, the neural net is aligned to the radio communication system concerned. The invention enables better information relating to possible error in the speech frame to be delivered to error correcting units in the radio receiver.

Abstract: The invention relates to a method of coding a sampled speech signal vector by selecting an optimal excitation vector in an adaptive code book. This optimal excitation vector is obtained by maximizing the energy normalized square of the cross correlation between the convolution of the excitation vectors with the impulse response of a linear filter and the speech signal vector. Before the convolution the vectors of the code book are block normalized with respect to the vector component largest in magnitude. In a similar way the speech signal vector is block normalized with respect to its component largest in magnitude. Calculated values for the squared cross correlation C.sub.I and the energy E.sub.I and stored corresponding values C.sub.M, E.sub.M for the best excitation vector so far are divided into a mantissa and a scaling factor with a limited number of scaling levels. The number of levels can be different for squared cross correlation and energy. During the calculation of the products C.sub.I .multidot.E.

Abstract: A method for positioning excitation pulses for a linear predictive coder (LPC) operating according to the multi-pulse principle, i.e. a number of such pulses are positioned at specific time points and with specific amplitudes. The time points and the amplitudes are determined from the predictive parameters (a.sub.k) and the predictive residue signal (d.sub.k), by correlation between a speech representative signal (y) and a composed synthesized signal (y). All possible time positions for the excitation pulses within a given frame interval are provided. The possible time positions are divided into a number (n.sub.f) of phase positions and each phase position is divided into a number of phases (f). All phases are vacant for the first excitation pulse. When this pulse has been positioned, the phase determined for this pulse is denied to the following excitation pulses until all pulses in a frame have been positioned.