Transmission of wideband speech signals
First Claim
1. A method of transmitting components of a signal in a high band of frequencies, above a predetermined frequency, on a digital transmission channel which carries components of the signal in a low band of frequencies, below the predetermined frequency, in the form of signal samples sampled at a rate of twice the predetermined frequency, comprising the steps of:
- deriving from the signal bits of information relating to the high band signal components; and
transmitting said bits of information in place of the least significant bit of the samples.
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Accused Products
Abstract
Speech signal components in a high band of frequencies between 4 and 8 kHz are transmitted via a digital transmission channel, which carries speech signal samples at frequencies below 4 kHz and sampled at a rate of 8 kHz, by replacing the least significant bit of the samples with bits of information derived from the high band by linear predictive coding. These information bits are transmitted in frames, each frame comprising a synchronizing bit and bits representing the power of and a set of filter coefficients for the high band signal components occurring in a period corresponding to the frame duration. Each such bit is transmitted redundantly three or six times in view of bit stealing techniques already used for signalling on digital transmission links. The resulting wideband speech signal transmission is compatible with existing limited bandwidth voice channel transmission arrangements.
73 Citations
17 Claims
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1. A method of transmitting components of a signal in a high band of frequencies, above a predetermined frequency, on a digital transmission channel which carries components of the signal in a low band of frequencies, below the predetermined frequency, in the form of signal samples sampled at a rate of twice the predetermined frequency, comprising the steps of:
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deriving from the signal bits of information relating to the high band signal components; and transmitting said bits of information in place of the least significant bit of the samples. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A method of transmitting components, at frequencies above 4 kHz, of a speech signal on a digital transmission channel via which eight-bit samples of the speech signal at a sampling rate of 8 kHz are transmitted, comprising the step of replacing an eighth least significant bit of each sample with a bit of information derived from the speech signal components at frequencies above 4 kHz.
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15. Apparatus for transmitting signal components of a speech signal in high and low bands of frequencies respectively above and below a predetermined frequency, comprising:
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means for producing digital samples of speech signal components in the low band at a sampling rate of twice the predetermined frequency for transmission, each sample comprising eight bits including a least significant bit; means for producing, from the speech signal, bits of information relating to speech signal components in the high band; and means for replacing the least significant bit of each sample with a bit of information relating to speech signal components in the high band. - View Dependent Claims (16, 17)
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Specification