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Selected Areas in Communications, IEEE Journal on

Issue 1 • Date Jan 1993

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Displaying Results 1 - 15 of 15
  • Designing a multiuser HDTV storage server

    Page(s): 153 - 164
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    The authors present a quantitative study of designing a multiuser HDTV server, and they present efficient techniques for storing multiple HDTV videos on disk and servicing multiple subscriber requests simultaneously, both under the constraint of guaranteeing HDTV playback rates. They develop a model that relates disk and device characteristics to the HDTV playback rate and derive a storage pattern for HDTV video streams that guarantees their real-time retrieval. Given multiple HDTV streams, mechanisms for merging their individual storage patterns are developed. Merging algorithms that yield a large improvement in space utilization over storing each of the streams independently are proposed. Policies such as round robin and quality proportional for servicing multiple subscribers simultaneously are studied. These studies provide a quantitative demonstration of the technological feasibility and economic viability of HDTV-on-demand servers on metropolitan area networks (MANs) View full abstract»

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  • Multiresolution broadcast for digital HDTV using joint source/channel coding

    Page(s): 6 - 23
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    The use of multiresolution (MR) joint source-channel coding in the context of digital terrestrial broadcasting of high-definition television (HDTV) is shown to be an efficient alternative to single-resolution techniques, which suffer from a sharp threshold effect in the fringes of the broadcast area. It is shown how matched multiresolution source and channel coding can provide a stepwise graceful degradation and improve the behavior, in terms of coverage and robustness of the transmission scheme, over systems not specifically designed for broadcast situations. The alternative available for multiresolution transmission through embedded modulation and error correction codes are examined. It is also shown how multiresolution trellis-coded modulation (TCM) can be used to increase coverage range. Coding results and simulations of noisy transmission are presented, and tradeoffs are discussed View full abstract»

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  • Source coding and transmission of HDTV images compressed with the wavelet transform

    Page(s): 46 - 58
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    Digital high-definition TV (HDTV) signals are generally compressed to reduce transmission bandwidth requirements. A compression algorithm for the bit rate reduction of an HDTV image using the wavelet transform is presented. The major problems related to the transmission of a compressed HDTV signal are analyzed. Transmission is examined both on a noisy channel and an asynchronous transfer mode (ATM) network. The effects of channel noise on the reconstructed image are determined, and a solution to mitigate the degradation of the image quality is presented. A model for the output bit rate of the HDTV coder is derived and used to simulate the transmission of an ATM multiplexer so that the network's main performance parameters can be determined View full abstract»

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  • Precoding technique for partial-response channels with applications to HDTV transmission

    Page(s): 127 - 135
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    An equivalent partial-response (PR) channel 1-Z-k arises in the envisioned terrestrial over-the-air broadcasting of digital high-definition television (HDTV) signals when a comb filter is used by an HDTV receiver to reduce the NTSC cochannel interference. The design of signal constellations and their associated precoders for this PR channel is considered. Besides PAM and square QAM, it is shown that generalized square and hexagonal constellations can also be used. Coded modulation and graceful degradation in the received signal quality are discussed. The results extended to a more general PR channel View full abstract»

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  • On the application of approximate APP decoding to digital video transmission

    Page(s): 136 - 145
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    For transmitting compressed digital video, the authors propose using threshold decodable block codes with large block length, and a posteriori probability (APP) soft decision decoding. A new approximation of the weight function associated with APP soft decision decoding of threshold decodable codes is presented. When the number of components in the parity equations is large, the new method gives excellent error performance, whereas there is a substantial degradation in the performance of the least reliable symbol approximation presented by Tanaka et al. (1980) and others. The effect of feedback on the performance of the APP decoder is also analyzed. It is shown that if the performance criterion is word error rate rather than bit error rate, feedback of previously decoded bits is essential to obtain all possible coding gain from the soft decision decoder. Finally, the performance of the proposed coding scheme is compared to the performance of a concatenated coding system with the same rate View full abstract»

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  • Multiscale video representation using multiresolution motion compensation and wavelet decomposition

    Page(s): 24 - 35
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    A multiscale video representation using wavelet decomposition and variable-block-size multiresolution motion estimation (MRME) is presented. The multiresolution/multifrequency nature of the discrete wavelet transform makes it an ideal tool for representing video sources with different resolutions and scan formats. The proposed variable-block-size MRME scheme utilizes motion correlation among different scaled subbands and adapts to their importance at different layers. The algorithm is well suited for interframe HDTV coding applications and facilitates conversions and interactions between different video coding standards. Four scenarios for the proposed motion-compensated coding schemes are compared. A pel-recursive motion estimation scheme is implemented in a multiresolution form. The proposed approach appears suitable for the broadcast environment where various standards may coexist simultaneously View full abstract»

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  • Advanced digital HDTV transmission system for terrestrial video simulcasting

    Page(s): 119 - 126
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    Transmission aspects of the advanced digital high definition television (AD-HDTV) system, for terrestrial simulcast delivery of HDTV are described. In AD-HDTV, two quadrature-amplitude-modulated (QAM) carriers, with different power spectral densities, are employed in a frequency division multiplex (FDM) mode within the standard 6-MHz channel. The resulting spectral shaping allows a larger power to be transmitted, compared to that for a single QAM carrier, for the same level of perceptual interference into cochannel NTSC. The coded video data are split into high-priority (HP) data and standard-priority (SP) data, and the vital information is sent on the appropriate QAM carrier, resulting in a robust audio and video transmission system. The availability is higher in scenarios where the carrier-to-noise ratio (CNR) is above the threshold for HP reception but below the threshold for SP reception; this is important in fringe areas. The NTSC planning factors, suitably modified for HDTV delivery, are used to estimate the coverage area for AD-HDTV. The calculated AD-HDTV coverage area of 54.5 miles is comparable to that for NTSC transmission View full abstract»

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  • Subband coding using human visual characteristics for image signals

    Page(s): 59 - 64
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (488 KB)  

    A subband coder which can be applied to various kinds of images such as HDTV (high-definition television), digital TV, and videophone is proposed using human visual characteristics. Data compression is achieved by the procedure based on human visual characteristics, where motion vectors in lower band are utilized to process components in higher band according to the degree of movement. Since the compression of the signal in higher band is accomplished by motion information, the proposed method shows good performance regardless of the degree of movement. Compared with the existing methods, which uniformly process all subblocks in the same subband, the quality of the image reconstructed by the proposed method is shown to be superior View full abstract»

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  • Flexible and robust packet transport for digital HDTV

    Page(s): 88 - 98
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    The packet-oriented transport approach used in the advanced digital television (ADTV) system for terrestrial HDTV broadcast is described. ADTV achieves robust HDTV delivery on terrestrial simulcast channels via MPEG video compression, prioritization of MPEG data, and `cell-relay' type packet transport in conjunction with a two-tier physical transmission scheme. General design issues relevant to the development of the proposed transport protocol are discussed. ADTV's prioritization algorithm for partitioning MPEG-encoded video into high-priority (HP) and standard-priority (SP) bit streams is outlined. The data transport format supporting these prioritized compressed video bit streams is described. The three principal sublayers of the ADTV transport protocol are discussed in terms of specific functions, impact of system performance, and hardware implementation factors. A proof-of-concept simulation model that incorporates transport encoding and decoding functionality is outlined, and performance evaluation results are given for illustrative transmission scenarios View full abstract»

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  • Subband HDTV coding using high-order conditional statistics

    Page(s): 65 - 76
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    An HDTV coding scheme that is capable of achieving high quality below 20 Mb/s is presented. The system employs motion estimation/compensation followed by four-band subband splitting. The band signals are then subject to quantization and coded by an innovative high-order entropy coder. It is shown that this high-order entropy coder generates a bit rate nearly 30% lower than that of run-length/Huffman coding for motion-compensated frame differences. About 15% improvement is observed for the intrafield coded data. To reduce the complexity of the high-order entropy coder for high-speed implementation, two techniques, codebook reduction and nonuniform quantization of conditioning samples, are developed. A method for selecting conditioning samples and their order, based on mutual information between samples, is proposed and shown to outperform several other systematic and intuitive approaches. Simulations show that the new system, at about 20 Mb/s, achieves picture quality comparable to that of a 120-Mb/s six-band intrafield coding system previously investigated View full abstract»

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  • Compatible coding of digital interlaced HDTV

    Page(s): 146 - 152
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    A compatible coding scheme for interlaced HDTV (high-definition television) is proposed. This scheme provides a standard definition signal and a second channel containing the additional information required to reach the HD resolution. The global scheme is of the pyramidal type: the standard TV is obtained by downsampling the HDTV signal by means of a field-based operation. The standard TV signal is coded, decoded, and upsampled. It is used as a prediction of the HD signal and the prediction error is coded in a second channel. In both branches, motion-compensated hybrid DCT coding is used. In addition, the DCT is taken within the frame View full abstract»

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  • Low-complexity subband encoding for HDTV images

    Page(s): 77 - 87
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    The transmission of high-definition television (HDTV) signals on available digital networks and satellites requires the adoption of sophisticated compression techniques to limit the bit rate requirements and to provide high-quality and reliable service to customers. For processing and transmission of image signals, a low-complexity codec without visible degradation is desired. A low-complexity intraframe subband image coding algorithm is developed. The low band is DPCM encoded and the high bands are PCM encoded. An efficient entropy coder is designed which reduces the overall bit rate significantly. It is shown that high-quality HDTV images can be obtained at as low a bit rate as 45 Mb/s or less with a very low-complexity encoder. For dividing the image into subbands, a new class of quadrature mirror filters (QMFs) called generalized quadrature mirror filters (GQMFs) is used for filtering. Performance is also evaluated by using short kernel filters (SKFs), which are easy to implement and require very few computations View full abstract»

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  • Multidimensional quantizers for scalable video compression

    Page(s): 36 - 45
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    Scalable video compression requires the creation of an encoded bit stream that may be decoded in part if channel bandwidth drops, decoder resources are limited, or a smaller image than the source is desired. A separable spatiotemporal subband decomposition is combined with vector and lattice quantizers modified so that the individual subbands may be decoded scalably. This results in finer bandwidth control and more flexibility than simply discarding entire subbands View full abstract»

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  • Practical coding for QAM transmission of HDTV

    Page(s): 111 - 118
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    It is demonstrated how modulation schemes based on QPSK can be directly incorporated into QAM-based systems. It is argued that this leads directly to an easily implementable structure that is both efficient in bandwidth and data reliability. It is contended that the correct solution to the concatenated coding problem for HDTV transmission is to simply extend the modulation codes developed for QPSK-to-QAM modulation. In nonconcatenated situations, a trellis code based on a binary code at rate 2/3 is usually best. However, this is not the case for higher error rates at the output of the trellis decoder (e.g., when a symbol error correcting decoder follows as a concatenated code). The reason for this follows from an analysis of the effect of the number of nearest neighbors on the error rate. A four-way partition of QAM is a natural extension of QPSK modulation; it is a simple matter to incorporate any good QPSK code into a trellis coding scheme for QAM modulation. A concatenated coding scheme based on QPSK trellis codes and symbol error correcting coding is proposed. An example is presented to show the advantages of this approach View full abstract»

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  • Analysis of satellite broadcasting systems for digital television

    Page(s): 99 - 110
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    The concept of digital direct satellite broadcasting (D-DBS), which allows unprecedented flexibility by providing a large number of audio-visual services, is introduced. The concept assumes an information rate of about 40 Mb/s, which is compatible with practically all present-day transponders. After discussion of the general system concept, the optimization procedure is introduced, and results of the transmission system optimization are presented. Channel distortion and uplink/downlink interference effects are taken into account by means of a time domain system computer simulation approach. It is shown, by means of link budget analysis, how a medium-power direct-to-home TV satellite can provide multimedia services to users equipped with small (60-cm) dish antennas View full abstract»

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Aims & Scope

IEEE Journal on Selected Areas in Communications focuses on all telecommunications, including telephone, telegraphy, facsimile, and point-to-point television, by electromagnetic propagation.

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Meet Our Editors

Editor-in-Chief
Muriel Médard
MIT