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Tunstall adaptive coding and miscoding

IEEE TRANSACTIONS ON INFORMATION THEORY 1996年第6期42卷 2167-2180页

作者： Fabris, F Sgarro, A Pauletti, R UNIV TRIESTE DIPARTIMENTO SCI MATEMAT TRIESTE ITALY PAULETTI PROFESS PONTE NELLE ALPI BELLUNO ITALY

In the first part of this paper, we tackle the case where a variable length-to-block Tunstall code is used to encode the wrong source (miscoding). It turns out that, exactly as it happens in the case with Huffman coding, the asymptotic excess rate is given by the informational divergence between the probability distribution ruling the source and the probability distribution for which the Tunstall code had been devised. We also prove asymptotic equality between the individual rate of a codeword and the corresponding self-information. This allows us to bound the maximal and the minimal length in a Tunstall tree. In the second part of the paper we study the case where the probability distribution of the source changes in time. If this happens, it is necessary to frequently update the current code, to ensure that the optimality conditions concerning its rate are met. This coding procedure is known as adaptive coding, We propose some schemes for adaptive Tunstall coding, based on the structure of the coding tree, on the ''ordering property,'' analogous to Gallager's sibling property of the Huffman code, and on the ''Tunstall regions,'' analogous to the attraction regions due to Longo and Galasso.

关键词： source coding variable length-to-block coding Tunstall codes adaptive coding informational divergence self-information

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Impact of network routing on the end-to-end transmission quality of cellular and PCS connections

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IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY 1998年第4期47卷 1227-1233页

作者： Dimolitsas, S Corcoran, FL Ravishankar, C Comsat Labs Clarksburg MD 20871 USA

Long-distance and especially international calls involve an increasing number of multilink circuits of cellular, personal communications, mobile satellite, and public switched telephone network (PSTN)-type connections incorporating a variety of speech coding devices, In particular, the rapid growth of cellular communications and the impeding emergence of personal communication systems (PCS's) has highlighted the need to characterize the quality of end-to-end connections when cellular and PCS terminals are connected over the PSTN. At the same time, the nonlinear nature of low-rate parametric speech coding has rendered unsuitable known analytical methods for estimating end-to-end quality of interconnected networks. Instead, quantification of transmission performance requires direct subjective evaluation of the pertinent connections of interest. In this paper, the quality of North American, Japanese, and European digital cellular and PCS terminals is quantified when these are interconnected using 16-kb/s low-delay code-excited linear prediction (LD-CELP) and 32-kb/s adaptive differential pulse code modulation (ADPCM) facilities. From these assessments, it can be concluded that digital cellular networks may meet end-to-end transmission planning criteria when interconnected with the switched network as long as calls are terminated to a wired terminal.

关键词： adaptive codes adaptive modulation cellular radio delays differential pulse code modulation digital radio internetworking linear predictive coding mobile satellite communication personal communication networks speech coding telecommunication network plan cellular radio Personal communication networks end-to-end transfer differential pulse code modulation Information Network Transmission Characteristics Digital radio mobile satellite communication Linear Prediction coding Network routing adaptive coding speech coding Personal communication systems adaptive modulation internetworking

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Smart codec: an adaptive packet data link

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IEE PROCEEDINGS-COMMUNICATIONS 1998年第3期145卷 180-185页

作者： Fairhurst, G Pang, SL Wan, PS Univ Aberdeen Dept Engn Aberdeen AB24 3UE Scotland

An adaptive convolutional code-rate system for packet data is presented which adapts the level of coding to overcome the effect of varying levels of noise. The system utilises the frame structure of packet data to synchronise adaption and uses a parallel decoding technique to ensure a hitless changeover between a number of different coding rates. The issues concerning the design are discussed in detail, including the resynchronisation of the Viterbi decoders, and the estimation of the level of noise. The system has been implemented using off-the-shelf components and tested over a range of error conditions and introduces only a low per-packet overhead. One important application is to counter the effect of a rain fade on a satellite communication link. A considerable improvement in the link throughput has been observed for a satellite link which suffers from typical rain fades.

关键词： adaptive coding fading channel packet traffic smart codec

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Deterministic Channel Modeling and Long Range Prediction of Fast Fading Mobile Radio Channels

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IEEE COMMUNICATIONS LETTERS 1998年第9期2卷 254-256页

作者： Eyceoz, Tugay Duel-Hallen, Alexandra Hallen, Hans N Carolina State Univ Dept Elect & Comp Engn Raleigh NC 27695 USA N Carolina State Univ Dept Phys Raleigh NC 27695 USA

In wireless communication systems, the direct signal and the reflected signals form an interference pattern resulting in a received signal given by the sum of these components. They are distinguished by their Doppler shifts at the mobile. Since the parameters associated with these components are slowly varying, the fading coefficients can be accurately predicted far ahead. This novel approach to fading channel prediction is combined with transmitter signal optimization to mitigate the effects of "deep fades," which severely limit the performance of mobile radio systems. This capability will potentially help to reduce power requirements for wireless channels and improve the system performance.

关键词： adaptive coding fading channels mobile communications modeling prediction methds

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adaptive coding using finite state hierarchical table lookup vector quantization with variable block sizes

Adaptive coding using finite state hierarchical table lookup...

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Asilomar Conference on Signals, Systems & Computers

作者： S. Mehrotra N. Chaddha R.M. Gray Information Systems Laboratory University of Stanford Stanford CA USA

We present an algorithm for performing adaptive vector quantization with memory. By using the memory between adjacent blocks which are encoded, we can take advantage of the correlation between adjacent blocks of pixels to reduce the redundancy. We use finite state vector quantization to provide the memory. To further improve the performance by exploiting nonstationarities in the image, we use variable block sizes in the encoding. This is done by using a quadtree data structure to represent an encoding based on variable block sizes. To reduce the encoding complexity, hierarchical table lookup schemes are used to replace all the full search encoders.

关键词： adaptive coding Table lookup Vector quantization Encoding Image coding Bit rate Decoding Arithmetic Information systems Laboratories

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Channel activation with adaptive coding rate and processing gain control for cellular DS/CDMA systems

Channel activation with adaptive coding rate and processing ...

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IEEE Conference on Vehicular Technology (VTC)

作者： S. Abeta S. Sampei N. Morinaga Faculty of Engineering Osaka University Suita Osaka Japan

This paper proposes a CDMA system using soft power control, adaptive controls for coding rate and processing gain, and channel activation to achieve high capacity cellular systems. The proposed system controls the processing gain and coding rate according to the variation of the channel and employs a channel activation technique in which data is transmitted in a shorter burst when the bit rate is high and it is transmitted in a longer burst when the bit rate is low. The results show that the proposed scheme can achieve more than 2 times larger capacity compared to the conventional scheme.

关键词： adaptive coding Gain control Multiaccess communication Bit rate Power control Interference adaptive control Multimedia communication Radio transmitters Power system modeling

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Modeling and low-complexity adaptive coding for image prediction residuals

Modeling and low-complexity adaptive coding for image predic...

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IEEE International Conference on Image Processing

作者： N. Merhav G. Seroussi M.J. Weinberger Hewlett Packard Laboratories Company Palo Alto CA USA

This paper elaborates on the use of discrete, two-sided geometric distribution models for image prediction residuals. After providing achievable bounds for universal coding of a rich family of models, which includes traditional image models, we present a new family of practical prefix codes for adaptive image compression. This family is optimal for two-sided geometric distributions and is an extension of the Golomb (1966) codes. Our new family of codes allows for encoding of prediction residuals at a complexity similar to that of Golomb codes, without recourse to the rough approximations used when a code designed for non-negative integers is matched to the encoding of any integer. We also provide adaptation criteria for a further simplified, sub-optimal family of codes used in practice.

关键词： Predictive models adaptive coding Image coding Context modeling Decoding Costs Laboratories Pixel Arithmetic Length measurement

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Lossy adaptive coding of motion vectors with global camera motion compensation

Lossy adaptive coding of motion vectors with global camera m...

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Asilomar Conference on Signals, Systems & Computers

作者： X.C. Chen N. Chaddha Computer System Laboratory University of Stanford Stanford CA USA

We propose a motion estimation and coding scheme that combines global camera motion estimation with a scene adaptive coder based on a quadtree structure with entropy-constrained vector quantization (ECVQ). Global camera motion parameters are first estimated before the local motion estimation. A quadtree structure is then constructed that finds the best block size to perform adaptive local motion estimation. Motion vectors of each block size are coded using an entropy-constrained vector quantizer specific for that block size. Our simulation results have shown that this adaptive coding algorithm has superior rate-distortion performance over the traditional fixed-block-size full-search method and the global camera motion compensation gives additional performance improvement when there is camera zoom and rotation.

关键词： adaptive coding Cameras Motion compensation Motion estimation Layout Video coding Laboratories Vector quantization Parameter estimation Rate-distortion

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Astrolink/sup TM/ satellite system overview

Astrolink/sup TM/ satellite system overview

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IEEE Conference on Aerospace

作者： E. Elizondo R. Gobbi A. Modelfino Lockheed Martin Telecommunications Sunnyvale CA USA

Lockheed Martin's Astrolink/sup TM/ system is currently in active development. Astrolink will provide global bandwidth-on-demand digital communications utilizing a constellation of nine Ka-Band geosynchronous satellites deployed in five orbital locations and interconnected by means of inter-satellite links. The Astrolink satellites will employ high gain spot beams, adaptive coding in response to rain, and on-board packet switching based on the Asynchronous Transfer Mode (ATM) network protocol. Astrolink will provide both "dial-up" user access and secure virtual private networks which will allow business, government and individual users to extend their communications-voice, data and video-throughout the world at an affordable cost and with improved reliability, thus bringing one step closer the vision of a Global Information Infrastructure.

关键词： Asynchronous transfer mode Digital communication Artificial satellites adaptive coding Rain Packet switching Access protocols Virtual private networks Business communication Government

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A fast adaptive cosine transform image coding technique

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IETE JOURNAL OF RESEARCH 1997年第4期43卷 295-301页

作者： Kumar, S Vijay, R Jain, RC Jain, PC Univ Calif Riverside Coll Engn Visualizat & Intelligent Syst Lab Riverside CA 92521 USA Birla Inst Technol & Sci Elect & Elect Engn Grp Pilani 333031 Rajasthan India Cent Elect Engn Res Inst Pilani 333031 Rajasthan India

A computationally efficient adaptive cosine transform coding technique is described in which only 10 x 10 DCT coefficients are required to be computed for a 16 x 16 pixel block. The coding process involves fuzzy based ac classification along with normalisation and quantisation which are governed by the activity index of the blocks. adaptive block distortion equalisation is also performed on the blocks to eliminate block edge structures. Zones of various shapes and sizes have been chosen for each activity class to perform zonal sampling. Very good reconstructed image quality is demonstrated for coding of gray level test images at a bit-rate of less than 0.3 bit/pixel which is lower than most of the other adaptive DCT techniques.

关键词： image coding video compression adaptive coding DCT

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