Plasma and leukocyte levels of zinc and copper were determined to assess the status of these elements in protein energy malnutrition. Significantly lower plasma zinc levels with low leukocyte concentrations indicate a...
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Plasma and leukocyte levels of zinc and copper were determined to assess the status of these elements in protein energy malnutrition. Significantly lower plasma zinc levels with low leukocyte concentrations indicate a deficiency of these elements in PEM.
The authors discuss an implementation of an experimental variable-bit-rate codec (VRC) based on adaptive differential pulse code modulation with a multiquantizer (ADPCM-MQ) that processes speech signals at 16 kb/s to ...
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The authors discuss an implementation of an experimental variable-bit-rate codec (VRC) based on adaptive differential pulse code modulation with a multiquantizer (ADPCM-MQ) that processes speech signals at 16 kb/s to 48 kb/s. The authors propose a method for the combined use of constant SNR (signal/noise ratio) and constant noise to determine optimum bit-rate control of the VRC. This algorithm was implemented using six digital signal processor chips. The average bit rate of the prototype codec for the telephone voice channel was about 23 kb/s, including supplementary information, and a quality better than that specified in G.721 (32-kb/s ADPCM) was observed.
The authors present a concatenated coding modulation scheme for error control in data communications. The scheme is achieved by concatenating a Reed-Solomon outer code and a bandwidth-efficient block inner code for M-...
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The authors present a concatenated coding modulation scheme for error control in data communications. The scheme is achieved by concatenating a Reed-Solomon outer code and a bandwidth-efficient block inner code for M-ary PSK (phase shift keying) modulation. The error performance of the scheme is analyzed for an AWGN (additive white Gaussian noise) channel. It is shown that extremely high reliability can be attained by using a simple M-ary PSK modulation inner code and a relatively powerful Reed-Solomon outer code. A simple method for constructing block codes for M-ary PSK modulation is also presented. Some short M-ary PSK codes with good minimum-squared Euclidean distance are constructed. These codes have a trellis structure and hence can be decoded with a soft-decision Viterbi decoding algorithm. The proposed scheme is particularly suitable for high-speed satellite communications for large file transfer where high reliability is required.
The authors propose variable bit rate modulo-PCM with multiquantizer (VBR-MPCM-MQ), which applies the multiquantizer method to VBR-MPCM using an adaptive predictor (VBR-MPCM-AP) select optimum step size. In VBR-MPCM-M...
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The authors propose variable bit rate modulo-PCM with multiquantizer (VBR-MPCM-MQ), which applies the multiquantizer method to VBR-MPCM using an adaptive predictor (VBR-MPCM-AP) select optimum step size. In VBR-MPCM-MQ, modulo amplitude, quantization bits, and step size are adaptively varied every block in order to prevent anomaly error and to increase data compression efficiency. By computer simulation, it is confirmed that the proposed VBR-MPCM-MQ has better performance by about 2 dB in both SQNR and segmental SQNR (SQNRseg) than conventional VBR-MPCM-AP. It is confirmed that the performance of VBR-MPCM-MQ is better by about 12 dB in SQNR and about 3 dB in SQNRseg than that of the conventional ADPCM (adaptive differential PCM) recommended by CCITT.
The authors characterize variable-rate interframe video coding for an ATM (asynchronous transfer mode) -based environment, focusing on bursty characteristics of encoded information. Inter-frame DPCM (differential puls...
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The authors characterize variable-rate interframe video coding for an ATM (asynchronous transfer mode) -based environment, focusing on bursty characteristics of encoded information. Inter-frame DPCM (differential pulse code modulation), motion-compensated DPCM and motion-compensated DCT (discrete cosine transform) are examined. As a useful measure to characterize variable-rate video sources, the coefficient of variation is proposed to supplement conventional distribution and autocovariance. Modeling methods variable-rate coders using the AR (autoregressive) process and coefficients of variation are introduced. The fitness of each model is evaluated by estimating stochastic multiplexing effects for a simple one-buffer one-server situation.
Transmission of 8-bit μ-law PCM (pulse-code-modulated) signals using M-level weighted quadrature amplitude modulation (WQAM), M = 16, 64 and 256, over Gaussian and Rayleigh fading channels is examined. The weighting ...
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Transmission of 8-bit μ-law PCM (pulse-code-modulated) signals using M-level weighted quadrature amplitude modulation (WQAM), M = 16, 64 and 256, over Gaussian and Rayleigh fading channels is examined. The weighting process modifies the positions of the QAM constellation points so that the overall average distortion in the recovered information-bearing source signal is reduced. The PCM bits are mapped onto the WQAM points so that the most signficant bits have a lower probability of being in error than the least significant bits. The WQAM systems have been optimized both for the same average and peak signal energy per transmitted symbol as for unweighted QAM. Theoretical and simulation results using speech indicate that 16-level and 256-level WQAM have gains of up to 3 and 5 dB, respectively, over unweighted QAM for the Gaussian channel. The gains due to weighting for 16-level QAM operating over an ideal slow Rayleigh fading channel are up to 5 dB.
A single-chip implementation of an intrafield DPM codec with adaptive quantizer characteristics and line buffer is discussed. The chip can be used both as transmitter and receiver. Processing of luminance and chromina...
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A single-chip implementation of an intrafield DPM codec with adaptive quantizer characteristics and line buffer is discussed. The chip can be used both as transmitter and receiver. Processing of luminance and chrominance components is possible. Moreover, the number of pixels per line is variable and additional I/O circuitry for utilization of the intrafield system as part of an interframe codec is provided. This experimental chip is realized in 1.5-μm CMOS technology and demonstrates the feasibility of a compact low-cost system component. The chip contains 60K transistors on an area of 80 mm2 including a built-in self-test. Correct operation has been verified up to 26 MHz. Power consumption is about 1 W.
The authors introduce a DPCM (differential pulse code modulation) system with modulo limiting (DPCM-ML). The ML in the DPCM system compresses the dynamic range of the prediction error by 6 dB. Therefore, fewer quantiz...
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The authors introduce a DPCM (differential pulse code modulation) system with modulo limiting (DPCM-ML). The ML in the DPCM system compresses the dynamic range of the prediction error by 6 dB. Therefore, fewer quantization levels are required to maintain the same level of quantization noise as in DPCM without ML. The reduced number of quantization levels translates to more efficient encoding and therefore lower data rate. The DPCM-ML system has a built-in self-correcting mechanism in which the ML at the receiver automatically tracks and corrects the DC offset applied to the prediction error by the ML at the transmitter. Experimental and simulation results on an interframe DPCM-ML for image sequence coding are presented.
A bit-for-bit compatible realization of an adaptive differential pulse code modulation (ADPCM) algorithm and a functional real-time test bed for algorithm modifications are presented. The hardware of the unit, USF32-2...
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A bit-for-bit compatible realization of an adaptive differential pulse code modulation (ADPCM) algorithm and a functional real-time test bed for algorithm modifications are presented. The hardware of the unit, USF32-2, is built around a single TMS320C25 microprocessor and has added circuitry to decrease computation time and facilitate testing. The basic algorithm and an enhanced version can be selectively compared. The encoder/decoder requires a total of 1301 clock cycles, but can be compressed to 1250, thereby enabling the authors to run both the encoder and the decoder on a single TMS320C25 processor.
The authors present a bit-for-bit compatible full-duplex realization of the CCITT ADPCM (adaptive differential pulse code modulation) transcoder algorithm (G.721) and a functional real-time testbed for algorithm modif...
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The authors present a bit-for-bit compatible full-duplex realization of the CCITT ADPCM (adaptive differential pulse code modulation) transcoder algorithm (G.721) and a functional real-time testbed for algorithm modifications. The coder is designed around a single TMS320C25 microprocessor. The authors have built peripheral processing circuitry to decrease computation time and facilitate testing. The base and modified algorithms (for voice and data coding) can be selectively compared. In particular, the authors evaluate a key modification for prevention of transition errors which occur in certain FSK (frequency shift-keying) modems.
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