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US4549304A
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ADPCM Encoder/decoder with signalling bit insertion
Assignee: Nortel Networks Ltd
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Filing: 1983-11-28
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Granted: 1985-10-22
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Expires: 2003-11-28
Abstract
Abstract In an ADPCM transmission system, signalling frames of an incoming multiplexed PCM signal are identified and signalling bits extracted therefrom. During each signalling frame, an ADPCM encoder/decoder is controlled by the signalling frame signal to operate entirely for 3-bit ADPCM, instead of the regular 4-bit ADPCM, to which 3-bit ADPCM the extracted signalling bits are added for transmission. The deliberate alteration from 4-bit to 3-bit ADPCM at the encoder and decoder of the system in each signalling frame ensures proper adaptation and consequently no loss of tracking between the encoder and the decoder.
Inventors
- 👤 Andreas H. Weirich
- 👤 Leo Strawczynski
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 06:06
CPC Classifications
H; H04; H04B; H04B14/00; H04B14/02; H04B14/06; H04B14/066; H04B14/068
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
122 words
An ADPCM transmission system in which ADPCM signal channels are multiplexed in t.d.m. frames each providing n bits for transmission of each channel, the frames comprising, in addition to regular frames, signalling frames in which m of the n bits of each channel are provided for the transmission f additional information, where n and m are integers and n>m>0, the system comprising: means for providing an indication of each signalling frame; ADPCM signal encoding means responsive to said indication for producing n-bit ADPCM signals in the regular frames and (n-m)-bit ADPCM signals in the signalling frames; and ADPCM signal decoding means responsive to said indication for decoding n-bit ADPCM signals in the regular frames and (n-m)-bit ADPCM signals in the signalling frames.
Claim 2
Dependent Claim
122 words
An ADPCM transmission system in which ADPCM signal channels are multiplexed in t.d.m. frames each providing n bits for transmission of each channel, the frames comprising, in addition to regular frames, signalling frames in which m of the n bits of each channel are provided for the transmission f additional information, where n and m are integers and n>m>0, the system comprising: means for providing an indication of each signalling frame; ADPCM signal encoding means responsive to said indication for producing n-bit ADPCM signals in the regular frames and (n-m)-bit ADPCM signals in the signalling frames; and ADPCM signal decoding means responsive to said indication for decoding n-bit ADPCM signals in the regular frames and (n-m)-bit ADPCM signals in the signalling frames.
Claim 3
Dependent Claim
98 words
A system as claimed in claim 1 wherein the ADPCM signal decoding means comprises: means for producing, in dependence upon said indication, an adaptive quantizing-step-size signal from the ADPCM signal; an inverse adaptive quantizer for producing, in dependence upon said indication, a reconstructed error signal from the ADPCM signal and the adaptive quantizing-step-size signal; means for producing a reconstructed signal from the reconstructed error signal and a predicted signal; and an adaptive predictor for producing the predicted signal from the reconstructed signal and the reconstructed error signal; said signals being produced for each of the ADPCM signal channels.
Claim 4
Dependent Claim
75 words
A system as claimed in claim 2 wherein the ADPCM signal encoding means comprises: a decoder constituted by the ADPCM signal decoding means; means for producing, for each channel, an error signal from a signal to be encoded and the predicted signal of the channel; and an adaptive quantizer for producing, for each channel and in dependence upon said indication, the ADPCM signal from the error signal and the adaptive quantizing-step-size signal of the channel.
Claim 5
Dependent Claim
30 words
A system as claimed in claim 3 wherein the means for producing the reconstructed error signal and the means for producing the error signal comprise a single multiplexed adding means.
Claim 6
Dependent Claim
11 words
A system as claimed in claim 1 wherein n=4 and m=1.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1988-10-21 | 1989-04-22 | 1989-10-22 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1992-10-21 | 1993-04-22 | 1993-10-22 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1996-10-21 | 1997-04-22 | 1997-10-22 | $7700.00 | Window Closed / Lapsed |