119,276 research outputs found
Multi-Mode Wireless Videophony
No full textA comparative study of arbitrarily programmable, but fixed-rate videophone codecs using quarter common intermediate format (QCIF) video sequences scanned at 10 frames/s is offered. These codecs were designed to allow direct replacement of mobile radio voice codecs in second generation wireless systems, such as the Pan-European GSM, the American IS-54 and IS-95 as well as the Japanese systems, operating at 13, 8, 9.6 and 6.7 kbps, respectively, although better video quality is maintained over higher-rate, 32kbps cordless systems, such as the Japanese PHS and the European DECT and CT2 systems. Best overall performance was achieved by our vector-quantised codecs, followed by the discrete cosine transformed and the quadtree-based schemes, which were characterised by the bit allocation schemes of Table 1. The associated video Peak Signal-to-Noise Ratio (PSNR) was around 30 dB, while the subjective quality can be viewed under http://www-mobile.ecs.soton.ac.uk. A range of multimode wireless transceivers were also proposed, which are characterised by Table 2
Dual-Mode Vector-Quantised Low-Rate Cordless Videophone Systems for Indoors and Outdoors Applications
No full textDual-mode reconfigurable wireless videophone transceivers are proposed for noise-, rather than interference-limited indoors and outdoors applications and their video quality, bit rate, robustness, and complexity issues are analyzed. A suite of fixed, but arbitrarily programmable low-rate, perceptually weighted vector quantized (VQ) codecs with and without run-length compression (RLC) are contrived for quarter common intermediate format (QCIF) videophone sequences. The 11.36-kb/s Codec 1 is Bose–Chaudhuri–Hochquenghem (BCH) (127,71,9) coded to a rate of 20.32 kb/s and this arrangement is comparatively studied along with the 8-kb/s Codec 2 and BCH(127,50,13) scheme, which has the same 20.32-kb/s overall rate. The source-sensitivity matched Systems 1–6 characterized in Table IV were contrived to comparatively study the range of system design options. For example, using Codec 1 in System 1 and coherent pilot symbol assisted 16-level quadrature amplitude modulation (16-PSAQAM), an overall signaling rate of 9 kBd was yielded, if the noise-limited channel had a signal-to-noise ratio (SNR) in excess of about 22 dB in the vicinity of the basestation or in indoors scenarios. In contrast, over lower quality outdoors channels near the fringes of the cell, the more robust 4-QAM mode of operation had to be invoked, which required twice as many time slots to accommodate the resulting 18-kBd stream and hence, reduced the total number of users supported. The robustness of Systems 2–4, and 6 was increased using automatic repeat requests (ARQ), again, inevitably reducing the number of users supported, which was between 6 and 16. In a bandwidth of 200 kHz, similarly to the Pan-European GSM mobile radio system’s speech channel, using systems 1, 3, 4, or 5, for example, 16 and eight videophone users can be supported in the 16- and 4-QAM modes, respectively, while in dual-mode cells the number of users is between eight and 16. The basic system characteristics are highlighted in Table IV. Index Terms—Fixed-rate video coding, QAM video communications, vector-quantized video coding, wireless video telephony
Mary Elizabeth Streit Preston Papers, MSS.4156
No full textAbstract: Typed account of one of the first Americans allowed to enter the U.S.S.R. in 1930, during the first "Five Year Plan."Scope and Content Note: The collection contains a twelve-page typed account of Mary Elizabeth Streit Preston of her trip to Russia in August 1931, when she was part of the first group of Americans allowed to enter the U.S.S.R. after the October Revolution during the first "FIve Year Plan." There are also two undated newspaper clippings about television programs filmed in the U.S.S.R.; the envelope they were in is dated July 16, 1963.Biographical/Historical Note: Mary Elizabeth Streit Preston, daughter of Charles William and Sally Ives Streit, was born in Birmingham, Alabama, in 1895. On February 22, 1917, she married Jerome L. Horton of the Horton Ice Cream Company of New York CIty. They were divorced and she married Lawrence Preston in 1933. They later divorced.Mary lived in New York during the summer and in Miami Beach, Florida, in the winter. She enjoyed a very active social life in New York, Palm Beach, Miami Beach, and Cuba. She traveled extensively, often with her mother. Together they toured around the world on the Graf Zeppelin in 1930.Mary was an accomplished athlete, winning awards in tennis and golf. Even late in life, she moved closer to the beach in Miami Beach in order to be able to walk to the beach and swim in the ocean every day.Mary Elizabeth Streit Preston died in Miami in 1983
S-matrix unitarity and current operator in quantum field theory
No full textStreit L. S-matrix unitarity and current operator in quantum field theory. Il Nuovo Cimento. 1964;34(1):198-204
Test function spaces for direct product representations of the canonical commutation relations
No full textStreit L. Test function spaces for direct product representations of the canonical commutation relations. Communications in Mathematical Physics. 1967;4(1):22-31
A 9/18 kBd Wireless Videophone Scheme
No full textA highly bandwidth efficient, fixed but arbitrarily programmable rate, perceptually weighted Discrete Cosine Transform (DCT) based video communicator for quarter common intermediate format (QCIF) videophone-sequences is presented. Perceptually weighted cost/gain controlled motion compensation and quad-class DCT-based compression is applied without variable rate compression techniques and without adaptive buffering in order to maintain a fixed transmission rate, which can be adjusted to any required value. In this treatise we opted for a source coded rate of 11.36 kbps and the sensitivity matched forward error correction (FEC) coded rate became 20.32 kbps. A partial forced update technique was invoked in order to keep transmitter and receiver aligned amongst hostile channel conditions. When using coherent pilot symbol assisted 16-level quadrature amplitude modulation (16-PSAQAM), an overall signalling rate of 9 kBd was yielded. Over lower quality channels 4QAM had to be invoked, which required twice as many time slots to accommodate the resulting 18 kBd stream. Over the best Gaussian and worst Rayleigh channels signal-to-noise ratio (SNR) values in the range of 7 to 20 dB were needed for these modems in order to maintain near-unimpaired image quality. In a bandwidth of 200 kHz, similarly to the GSM speech channel, 16 and 8 videophone users can be supported, when using the 16QAM and 4QAM systems, respectively
A Fractal Video Communicator
No full textThe image quality and compression ratio trade-offs of five different 176 × 144 pels quarter common intermediate format (QCIF) fractal image codes are investigated by simulation. The average peak signal-to-noise ratio (PSNR) ranges from 29 dB to 37 dB, while the coding rate from 0.24 bit/pel (bpp) to 1.22 bit/pel, as seen in Table 1. Two of the candidate codecs, a 0.28 bit/pel and a 1.1 bit/pel codec, were subjected to bit-sensitivity analysis and projected by the source-sensitivity matched shortened binary BCH(122,80,6) and BCH (122,52,11) codes and transmitted using coherent pilot symbol assisted (PSAM) square-constellation 16-level quadrature amplitude modulation (16-QAM). The proposed fractal video communications required a channel signal-to-noise ratio (SNR) and signal-to-interference ratio (SIR) of about 15 dB in order to maintain a video peak SNR (PSNR) of 31 dB and 35 dB at signaling rate of 39 kBaud and 156 kBaud, respectively, over Rayleigh-fading channels having a propagation frequency of 1800 MHz and a pedestrian speed of 2 mph
Quadtree-Based Reconfigurable Cordless Videophone Systems
No full textAbstract - Arbitrarily programmable, but fixed-rate quadtree (QT) decomposed. parametrically enhanced videophone codecs using quarter common intermediate format (QCIF) video sequences are proposed as a direct replacement for mobile radio voice codecs In second generation systems, such as the Pan-European GSM, the American IS-54 and IS-95, as well as the Japanese systems. The corresponding bit rates are 13, 8, 9.6 and 6.7 kb/s, respectively. As an example, the proposed 11.36 kb/s prototype Codec 1 and the 11 kb/s Codee 2 are embedded in the adaptively reconfigurable wireless videophone Systems 1-4 featured in Table IV and their video quality, bit rate, robustness, and complexity Issues are investigated. Coherent reconfigurable 16 or four-level pilot symbol assisted quadrature amplitude modulation (PSAQAM) is used and the system's robustness is Improved by a combination of diversity and automatic repeat request (ARQ) techniques. When using a bandwidth of 200 kHz, as In the Pan-European GSM mobile radio system, the number of videophone users supported varies between three and 16, while the minimum required channel signal to noise ratio over Gausslan and Rayleigh channels is in excess of 6 and 8 dB, respectively, assuming a noise-limited, rather than interference-limited scenario. The salient system features are summarized in Table 1V
Vector-quantised Cordless Videophone Transceivers
No full textA variety of adaptively re-configurable wireless videophone transceivers are proposed and their video quality, bit rate, robustness and complexity issues are analysed. A suite of fixed but arbitrarily programmable low-rate, perceptually weighted vector quantised (VQ) codecs with and without run-length compression (RLC) are contrived for quarter common intermediate format (QCIF) videophone sequences. The 11.36 kbps Codec 1 is BCH(127,71,9) coded to a rate of 20.32 kbps and this arrangement is comparatively studied along with the 8 kbps Codec 2 and BCH(127,50,13) scheme, which has the same 20.32 kbps overall rate. The source-sensitivity matched Systems 1-6 characterised in Table 3 were contrived to comparatively study the range of system design options. For example, using Codec 1 in System 1 and coherent pilot symbol assisted 16-level quadrature amplitude modulation (16-PSQAM), an overall signalling rate of 9kBd was yielded. Over lower quality channels the 4QAM mode of operation had to be invoked, which required twice as many time slots to accommodate the resulting 18kBd stream. The robustness of Systems 2,3,4 and 6 was increased using Automatic Repeat Requests (ARQ), inevitably reducing the number of users supported, which was between 6 and 16. In a band-width of 200kHz, similarly to the Pan European GSM mobile radio systems's speech channel, using Systems 1, 3, 4 or 5 for example, 16 and 8 videophone users can be supported in the 16QAM and 4QAM modes, respectively. The basic system characteristics are highlighted in Table 3
An Adaptive Discrete Cosine Transformed Videophone Communicator for Mobile Applications
No full textA highly bandwidth efficient, fixed but arbitrarily programmable rate, perceptually weighted Discrete Cosine Transfor (DCT) based video communicator for quarter common intermediate format (QCIF) videophone sequences is presented. Perceptually weighted cost/gain controlled motion compensation and quad-class DCT-based compression is applied without variable rate compression techniques and without adaptive buffering in order to maintain a fixed transmission rate, which can be adjusted to any required value. in this treatise we opted for a source coded rate of 11.36 kbps and the sensitivity-matched forward error correction (FEC) coded rate became 20.32 kbps. A partial forced update technique was invoked in order to keep transmitter and receiver aligned amongst hostile channel conditions. When using coherent pilot symbol assisted 16-level quadrature amplitude modulation (16-PSAQAM), an overall signalling rate of 9 kBd was yielded. OVer lower quality channels 4QAM had to be invoked, which required twice as many time slots to accommodate the resulting 18 kBd stream. Over the best Gaussian and worst Rayleigh channels signal-to-noise ratio (SNR) values in the range of 7 to 20 dB were needed for these modems in order to maintain near-unimpaired image quality. In a bandwidth of 200 kHz, similarly to the GSM speech channel, 16 and 8 videophone users can be supported, when using the 16QAM and 4QAM systems, respectively
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