Method of reconstructing lost data in a digital voice transmission system and transmission system using said method

A method of reconstructing lost data in a digital voice transmission system wherein a residual baseband signal is derived at the transmitting end from the voice signal to be encoded and is then distributed among a plurality of sub-bands whose sampled contents are individually quantized, said method being characterized in that it includes the steps of:

• analyzing the signal received to identify the lost data;
• analyzing within each sub-band previously received valid data to determine a term T.sub.(k) relating to the period of the signal therein (with k denoting the rank of the sub-band considered);
• and,
• reconstructing the lost signal in such a way as to maintain the periodicity T.sub.(k) of the signal in said sub-band.

A method of reconstructing lost data in a BCPCM-type digital voice transmission system wherein a low-frequency signal is derived at the transmitting end from the voice signal to be encoded and is then distributed among a plurality of sub-bands which are individually processed to quantize the samples contained therein and assemble same in blocks (or packets) representing each a voice signal segment of predetermined duration, said method being characterized in that it includes the steps of:

• analyzing the received blocks of samples to detect valid blocks;
• sequentially storing in a buffer a predetermined number of valid blocks;
• identifying the lost block(s);
• analyzing within each sub-band the stored valid block(s) immediately preceding the lost block, to determine a term T.sub.(k) called period of the signal in the sub-band of rank k;
• and,
• reconstructing the signal in each sub-band by constructing a signal of period T.sub.(k) with k denoting the rank of the sub-band considered.

A method of reconstructing lost data in a BCPM-type digital voice transmission system wherein a low-frequency signal is derived at the transmitting end from the voice signal to be encoded and is then distributed among a plurality of sub-bands which are individually processed to quantize the samples contained therein and assemble same in blocks representing each a voice signal segment of predetermined duration, said method being characterized in that it includes the steps of:

• analyzing the received blocks of samples to detect valid blocks;
• sequentially storing in a buffer a predetermined number of valid blocks;
• identifying the lost block(s);
• analyzing within each sub-band the stored valid block(s) immediately preceding and immediately following the lost block, to determine a term T.sub.(k) with k denoting the rank of the sub-band considered;
• and,
• reconstructing the signal in each sub-band by constructing a signal of period T.sub.(k) with k denoting the rank of the sub-band considered.

A digital voice transmission system for transmitting voice signals from a transmitter that processes the voice signal to provide segments having a predetermined duration, each segment providing a block of bits containing a term (ENERG) relating to the energy of the signal within a high-frequency band, characteristic coefficients (COEF) of the voice signal to be transmitted, and a term (SIGNAL) relating to the contents of a low-frequency band of said voice signal to be transmitted, said SIGNAL term being processed within sub-bands of the low-frequency band, and means of transmitting said block to a receiver, said receiver reconstructing the voice signal from the ENERG, COEF and SIGNAL terms contained in each received block of bits, said receiver being characterized in that it includes:

• input means that process the received signal for reconstructing each block of bits;
• buffer connected to said input means and storing at least one block of bits;
• validity checking means connected to said buffer means for checking the validity of blocks received and identifying lost blocks;
• means connected to said validity checking means and said buffer means for determining, for each sub-band, a term T.sub.(k) relative to the period of the signal contained in the sub-band considered;
• means for reconstructing lost blocks from the blocks in the vicinity thereof, said reconstructing means connected to said means of determining T.sub.(k) for reconstructing a sub-band signal of period T.sub.(k) said reconstructing means processing the ENERG, COEF and SIGNAL terms separately;
• and,
• synthesizing means connected to said means for reconstructing lost blocks and to said buffer means for providing the received voice signal.

A DSI-type of digital voice transmission system wherein voice signals are transmitted as packets containing each at least one block of bits from each active source of voice signal, each block containing a term relating to the energy (ENERG) of the voice signal, coefficients (COEF), and a term representing a low-frequency signal called residual baseband signal, said term being processed within sub-bands of said residual baseband signal, said transmissions system being characterized in that it includes at the receiving end:

• input means that process the received signal for reconstructing each block of bits;
• buffer means connected to said input means and storing at least one block of bits;
• validity checking means connected to said buffer means for checking the validity of blocks received and identifying lost blocks;
• demultiplexing means connected to said buffer means for separating the ENERG, COEF, and SIGNAL terms from one another;
• means connected to said validity checking means and said buffer means for determining, for each sub-band, a term T.sub.(k) relative to the period of the signal contained in the sub-band considered;
• reconstruction means connected to said demultiplexing means and to said validity checking means for reconstructing lost packets, said reconstruction means further connected to said means of determining T.sub.(k) reconstructing a sub-band signal of period T.sub.(k), said packet reconstructing means processing the ENERG, COEF and SIGNAL terms separately;
• and,
• synthesizing means connected to said reconstructing means and to said demultiplexing means.