Speech predictive encoding communication system

Claim 2

In a digital communications system wherein information from a maximum number (M) of voice circuits at a transmitting station may be transmitted to a receiving station via a transmission path of given power level, bit rate and bandwidth, apparatus for enable the transmission of information from a number (N) greater than said maximum number (M) of voice circuits over said transmission path comprising: a. means at said transmitting station for periodically sampling the amplitude of voice signals on each circuit of said N voice circuits; b. means for comparing for each of said N circuits, a present amplitude sample with a prior amplitude sample which had been transmitted to said receiving station, said comparing means generating N signals in response to said comparisons and storing said N signals as a control word; c. means for generating a transmission frame comprising a digital representation of those present amplitude samples which differ from the corresponding prior amplitude samples by a predetermined amount and said control word from said comparing means.

Claim 3

The apparatus of claim 1 further including voice detector means, connecteD to said sampling means, for detecting speech in the presence of noise.

Claim 4

The apparatus of claim 2 wherein the servicing sequence of said sampling means is changed such that, periodically, a different voice circuit is the first circuit sampled.

Claim 5

In a digital communications system wherein information from a plurality of voice circuits (N) at a transmitting station may be transmitted at a minimum bit rate to a receiving station via a transmission path, apparatus to enable the transmission of information from said N voice circuits over a transmission path at less than said minimum bit rate comprising: a. means for sampling and digitally encoding, at least once each of successive sampling frames, the amplitude of the analog signal in each of said N voice circuits; b. means for digitally comparing the encoded amplitude samples on said N circuits during a present sampling frame with corresponding encoded amplitude samples on said N circuits during a prior sampling frame and for generating for each frame a signal identifying each comparison and storing said signals as a single control word; c. means for generating a frame of information for transmission to said receiving station comprising a first group of digital signals representing the amplitude of those present samples which differ from the corresponding prior samples by a predetermined amount and a second group of digital signals comprising said control word.

Claim 6

In a digital communications system wherein information from a plurality of voice circuits (N) at a transmitting station may be transmitted at a minimum bit rate to a receiving station via a transmission path, apparatus to enable the transmission of information from said N voice circuits over a transmission path at less than said minimum bit rate comprising: a. means for sampling and digitally encoding, at least once each of successive sampling frames, the amplitude of the analog signal in each of said N voice circuits; b. means for digitally comparing the encoded amplitude samples on said N circuits during a present sampling frame with corresponding encoded amplitude samples on said N circuits during a prior sampling frame and for generating for each frame a signal identifying each comparison and storing said signals as a single control word; c. means for generating a frame of information for transmission to said receiving station comprising a first group of digital signals representing the amplitude of those present samples which differ from the corresponding prior samples by a predetermined amount and a second group of digital signals comprising said control word.

Claim 7

The apparatus of claim 4 including means for substituting, when required for parity, a parity signal as one of said second group of digital signals.

Claim 8

The apparatus of claim 5 further including means for periodically changing the order by which all circuits are serviced during successive transmission frames.

Claim 9

The apparatus of claim 6 further comprising means for generating, as part of a transmission frame, a digital code word representing the particular voice circuit servicing sequence.

Claim 10

In a digital communications system wherein information from a plurality of N voice circuits at a transmitting station may be transmitted to a receiving station via a transmission path, wherein each of the N voice circuits is sampled at the Nyquist sampling rate at least once during each of successive sampling frame periods, wherein each of the resultant samples are encoded into digital signals and wherein the transmission path requires a minimum bit rate to transmit all of said digital signals for a given voice transmission quality, apparatus to enable the digital transmission at said given voice quality of either said information from said N voice circuits over a transmission path at less than said minimum bit rate, or information from more than said N voice circuits over said transmission path at said minimum bit rate comprising: a. a first storage means at the transmitting station for storing, for each voice circuit, said digitally encoded samples from a prior sampling frame; b. means, connected to said first storage means, for digitally comparing the sample from each respective voice circuit for a present sampling frame with the sample stored in the first storage means for such respective voice circuit and for providing an identifying signal for each comparison representing the particular voice circuit whose sample is being compared; c. means for assembling and transmitting a digitally encoded transmission frame of information comprising said identifying signals and signals representing those present samples which differ from corresponding prior samples by a predetermined amount; d. means at the receiver for receiving said digitally encoded transmission frame; e. a second storage means for storing for each voice circuit previously transmitted, digitally encoded samples from a prior sampling frame; and f. means connected to said receiving means for substituting for the samples stored in the second storage means, respective transmitted present samples in accordance with said identifying signalS.

Claim 11

In a digital communications system wherein information from a plurality of N voice circuits at a transmitting station may be transmitted to a receiving station via a transmission path, wherein each of the N voice circuits is sampled at the Nyquist sampling rate at least once during each of successive sampling frame periods, wherein each of the resultant samples are encoded into digital signals and wherein the transmission path requires a minimum bit rate to transmit all of said digital signals for a given voice transmission quality, apparatus to enable the digital transmission at said given voice quality of either said information from said N voice circuits over a transmission path at less than said minimum bit rate, or information from more than said N voice circuits over said transmission path at said minimum bit rate comprising: a. a first storage means at the transmitting station for storing, for each voice circuit, said digitally encoded samples from a prior sampling frame; b. means, connected to said first storage means, for digitally comparing the sample from each respective voice circuit for a present sampling frame with the sample stored in the first storage means for such respective voice circuit and for providing an identifying signal for each comparison representing the particular voice circuit whose sample is being compared; c. means for assembling and transmitting a digitally encoded transmission frame of information comprising said identifying signals and signals representing those present samples which differ from corresponding prior samples by a predetermined amount; d. means at the receiver for receiving said digitally encoded transmission frame; e. a second storage means for storing for each voice circuit previously transmitted, digitally encoded samples from a prior sampling frame; and f. means connected to said receiving means for substituting for the samples stored in the second storage means, respective transmitted present samples in accordance with said identifying signalS.

Claim 12

The apparatus of claim 8 further including apparatus, at a receiver, for reconstructing the samples in the present frame, comprising means for converting into analog form, for each transmission frame, the samples stored in said second storage means including the samples that were substituted into the storage means for said frame.

Claim 13

The apparatus of claim 9 further including a voice detector, at the transmitter, which detects speech in the presence of noise.

Claim 14

The apparatus of claim 9 further including: a. means, at the transmitter, for substituting a parity check signals for one of said identifying signals; b. means, at the receiver, for making a parity check on the received identifying signal; and c. means for reconstructing the previously transmitted samples stored in the second storage means as the present sampling frame of information when the parity check indicates an incorrectly received identifying signal.

Claim 15

The apparatus of claim 11 further comprising: a. sequence generating means, at the transmitter and the receiver, for respectively generating a digital code word identifying the sequence in which each of the voice circuits are to be serviced; b. means for transmitting the sequence identifying code word generated at the transmitter as part of the transmission frame; c. means, at the receiver, for checking to determine if the received sequence identifying code word is being received correctly; and d. means for utilizing the received sequence identifying code word in place of the sequence identifying code word generated at the receiver when reception of the proper sequence identifying code word is indicated.

Claim 16

The apparatus of claim 9 including means for varying the order in which the plurality voice circuits are sampled for each of successive transmission frames comprising: a. third storage means for digitally storing the identifying signal for each comparison in a present frame; b. fourth storage means for digitally storing all of the samples of a present frame; c. fifth storage means for digitally storing those present samples which are to be transmitted; d. sequence generating means for generating a digital code word identifying the order in which each of the voice circuits is to be serviced; e. means, responsive to the digital code word identifying the servicing order, for enabling the third and fourth storage means, respectively, to read-out the contents of the third storage means commencing with the signal corresponding to the voice circuit which is to be serviced first and to read-out the contents of the fourth storage means commencing with the sample corresponding to that voice circuit which is to be serviced first; and f. means for transferring, from the fourth storage means to the fifth storage means, in accordance with the signals read out from the third storage means, those present samples which are to be transmitted.

Claim 17

The apparatus of claim 13 wherein said means for substituting comprises: a. sixth storage means for digitally storing the transmitted samples; b. means for determining where in the received identifying signals the identifying signal relating to the first sampled voice circuit is located; c. means for identifying the location in the sixth storage means of the sample from the lowest active channel relative to the first sampled voice circuit; and d. means for transferring the samples stored in the sixth storage means to the second storage means commencing with the sample from the lowest active channel.

Claim 18

The apparatus of claim 14 wherein said means for determining the location, in the sample assignment word, of the first signal comprises: a. sequence generating means for generating a digital code word representing the servicing sequence for the present sampling frame; and b. means, synchronized with the signal in the sample assignment word representing the first voice circuit serviced in the present sampLing frame, for counting to a number representing the total number of plurality of voice circuits commencing with the number represented by the servicing sequence digital code word.

Claim 19

The apparatus of claim 14 wherein said means for substituting further includes: a. means for determining the location in the sixth storage means containing the last transmitted sample; and b. means for continuing the substitution of samples from the sixth storage means to the second storage means after substituting the last transmitted sample, commencing with the first transmitted sample, without investigating other locations in the sixth storage means for samples that could have been stored in such other locations if transmitted.