In June 1982, CCITT Study Group XVIII chartered a small seven-country expert group to recommend a single 32-kb/s coding algorithm as a candidate for international standardization. The group embarked on an eighteen-mon...
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In June 1982, CCITT Study Group XVIII chartered a small seven-country expert group to recommend a single 32-kb/s coding algorithm as a candidate for international standardization. The group embarked on an eighteen-month work program that resulted in an ADPCM algorithm defined as a digital transcoding technique from 64-kb/s PCM. The algorithm uses both adaptive quantization and adaptive prediction. CCITT formally approved the algorithm as an international standard at the October 1984 plenary session. The major elements of the ADPCM algorithm are described.
A set of tests is described for measuring the performance of the ADPCM coder with signals other than speech. The general test procedures are outlined, and major results are presented. Most results pertain to voiceband...
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A set of tests is described for measuring the performance of the ADPCM coder with signals other than speech. The general test procedures are outlined, and major results are presented. Most results pertain to voiceband data modems operating at 2400, 4800, and 9600 b/s. Other results include an objective characterization, dual-tone multifrequency measurements, and analog telecopy measurement.
A new coding scheme has been standardized at 32 kb/s using adaptive predictive ADPCM. One of the most important properties of such coding is the synchronous tandem property, i. e. , the nonaccumulation of distortion i...
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A new coding scheme has been standardized at 32 kb/s using adaptive predictive ADPCM. One of the most important properties of such coding is the synchronous tandem property, i. e. , the nonaccumulation of distortion in successive tandem-connected ADPCM coders with a 64-kb/s PCM interface. The synchronous tandem algorithm described here is used to provide this property in the 32-kb/s ADPCM coder. The synchronous tandem property is important because 32-kb/s ADPCM coding will be introduced for transmission purposes while the TDM switch still operates with 64-kb/s PCM.
A method for the design of economic PCM switching networks composed of uniform time-space elements is proposed. This method makes it possible to design switching networks having in many cases fewer stages and fewer el...
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A method for the design of economic PCM switching networks composed of uniform time-space elements is proposed. This method makes it possible to design switching networks having in many cases fewer stages and fewer elements than known networks.
A piecewise linear approximation is used for the dependence of the anomalous error pulse amplitude, in the case of failures of the PCM signal place symbols, on the coder input signal amplitude. The 'weights' o...
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A piecewise linear approximation is used for the dependence of the anomalous error pulse amplitude, in the case of failures of the PCM signal place symbols, on the coder input signal amplitude. The 'weights' of the different digit symbol failures are estimated for systems with a type A-87. 6 companding characteristic. The possibility of reducing the noise immunity threshold of actual PCM systems is estimated.
An original M-ary multiform transmission system is presented, characterized by the fact that the waveforms carrying the multiplexed information are made up of orthogonal and equal energies polynomial segments. The gen...
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An original M-ary multiform transmission system is presented, characterized by the fact that the waveforms carrying the multiplexed information are made up of orthogonal and equal energies polynomial segments. The general expression of these polynomials on (O,T) interval and their relations with Legendre polynomials are deduced. An upper bound on the probability of error in the presence of intersymbol interference and additive Gaussian noise is evaluated.
The economics of digital transmission in rural areas frequently favor the use of transmission systems with fewer than the standard 30 channels. A new 10-channel system has been successfully developed for such applicat...
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The economics of digital transmission in rural areas frequently favor the use of transmission systems with fewer than the standard 30 channels. A new 10-channel system has been successfully developed for such applications.
A CO 2 laser rangefinder has been built that uses an acousto-optic modulator to obtain an amplitude modulated optical beam from a cw laser. An on-off deflected beam was obtained by driving the modulator with a carrier...
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A CO 2 laser rangefinder has been built that uses an acousto-optic modulator to obtain an amplitude modulated optical beam from a cw laser. An on-off deflected beam was obtained by driving the modulator with a carrier modulated by a periodic binary code. The received infra-red radiation was heterodyne detected. After envelope detection of the heterodyne signal, the signal-to-noise ratio was improved by applying a digital integrator. Ranging was carried out by calculating the delay of the received code by means of a cross-correlation technique. For this purpose a minicomputer was implemented in the system. Using 1 W average beam power and measuring times less than 1 s, ranges of several kilometers have been determined from stationary targets.
To eliminate noise immunity problems in infrared remote control systems the most common solution is to use elaborate preamplifier circuits. A new approach is chosen for remote control chips by using an inherently reli...
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To eliminate noise immunity problems in infrared remote control systems the most common solution is to use elaborate preamplifier circuits. A new approach is chosen for remote control chips by using an inherently reliable pulse code modulation (PCM) coding system that allows the intelligent receiver/decoders to recognise valid signals in the presence of severe interference. Receiver configurations vary considerably but three typical applications are given by way of example.
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