Algebraic codebook with signal-selected pulse amplitude/position combinations for fast coding of speech

A device for conducting a search in a codebook in view of encoding a sound signal, said codebook consisting of a set of pulse amplitude/position combinations, each pulse amplitude/position combination defining L different positions and comprising both zero-amplitude pulses and non-zero-amplitude pulses assigned to respective positions p=1, 2, . . . L of the combination, and each non-zero-amplitude pulse assuming at least one of q possible amplitudes, said device comprising:

• means for pre-selecting from said codebook a subset of pulse amplitude/position combinations in relation to the sound signal;
• and
• means for searching only said subset of pulse amplitude/position combinations in view of encoding the sound signal whereby complexity of the search is reduced as only a subset of the pulse amplitude/position combinations of the codebook is searched;
• wherein the pre-selecting means comprises means for pre-establishing, in relation to the sound signal, a function S.sub.p pre-assigning to the positions p=1, 2, . . . L valid amplitudes out of said q possible amplitudes, and wherein the searching means comprises means for limiting the search to the pulse amplitude/position combinations of said codebook having non-zero-amplitude pulses which respect the pre-established function.

A cellular communication system for servicing a large geographical area divided into a plurality of cells, comprising:

• mobile transmitter/receiver units;
• cellular base stations respectively situated in said cells;
• means for controlling communication between the cellular base stations;
• a bidirectional wireless communication sub-system between each mobile unit situated in one cell and the cellular base station of said one cell, said bidirectional wireless communication sub-system comprising in both the mobile unit and the cellular base station (a) a transmitter including means for encoding a speech signal and means for transmitting the encoded speech signal, and (b) a receiver including means for receiving a transmitted encoded speech signal and means for decoding the received encoded speech signal;
• wherein said speech signal encoding means comprises a device for conducting a search in a codebook in view of encoding the speech signal, said codebook consisting of a set of pulse amplitude/position combinations, each pulse amplitude/position combination defining L different positions and comprising both zero-amplitude pulses and non-zero-amplitude pulses assigned to respective positions p=1, 2, . . . L of the combination, and each non-zero-amplitude pulse assuming at least one of q possible amplitudes, said search conducting device comprising:
• means for pre-selecting from said codebook a subset of pulse amplitude/position combinations in relation to the speech signal;
• and
• means for searching only said subset of pulse amplitude/position combinations in view of encoding the speech signal whereby complexity of the search is reduced as only a subset of the pulse amplitude/position combinations of the codebook is searched;
• wherein the pre-selecting means comprises means for pre-establishing, in relation to the sound signal, a function S.sub.p pre-assigning to the positions p=1, 2, . . . L valid amplitudes out of said q possible amplitudes, and wherein the searching means comprises means for limiting the search to the pulse amplitude/position combinations of said codebook having non-zero-amplitude pulses which respect the pre-established function.