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International Symposium on Optical Memory and Optical Data Storage

作者： L. Selavo D.M. Chiarulli S.P. Levitan Department of Computer Science University of Pittsburgh Pittsburgh PA USA

Volumetric and page oriented optical storage systems have a great potential for high data density and high speed through page oriented data access (Haichuan Zhang et al, Proc. 18th IEEE Symp. Mass Storage Sys., 2001). However, in order to be practical, they have to maintain data integrity using error correction and modulation codes. The coding comes at a cost of spatial overhead of codeword size over the source data size, and processing time overhead for encoding and decoding. Our proposed adaptive modulation scheme strives to minimize both overheads. It achieves utilization of 74% with constant time complexity, which is competitive with other recently proposed schemes for page-oriented memories.

关键词： Optical modulation adaptive coding Modulation coding adaptive optics Encoding Optical arrays High speed optical techniques Decoding Costs Detectors

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Design and implementation of the 155 Mbps adaptive modem for broadband satellite communications

Design and implementation of the 155 Mbps adaptive modem for...

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International Symposium on Wireless Personal Multimedia Communications (WPMC)

作者： Eun-A Choi Dae-Ig Chang Nae-Soo Kim Broadband Wireless Communication Research Department Radio & Broadcasting Research Laboratory ETRI Daejeon South Korea

ISBN: (纸本)0780374428

We present the design and implementation of a 155 Mbps satellite modem adaptively compensated against rain attenuation. In order to compensate rain attenuation over a high-speed satellite link, adaptive coding schemes with variable coding rates and pragmatic TCM, that can decode both QPSK and TC-8PSK using the same Viterbi decoder, are studied and analyzed. The pragmatic TCM with rate 2/3, selected as the optimal parameters for implementation, is modeled by VHDL. The key design issues are how to achieve a high data rate and how to integrate into a single ASIC chip various functions such as different data rates, scrambler/descrambler, interleaver, encoder/decoder, and BPSK/QPSK/8PSK modulator/demodulator. The implemented 155 Mbps adaptive modem has simplified interface circuits among the many functional blocks, and parallel processing architecture to achieve the high data rate. This 155 Mbps adaptive modem was designed and implemented by a single ASIC chip with the 0.25 /spl mu/m CMOS standard cell technology.

关键词： Modems Broadband communication Satellite communication Decoding Rain Attenuation Quadrature phase shift keying Application specific integrated circuits CMOS technology adaptive coding

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adaptive coding for time-varying channels using outdated fading estimates

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IEEE TRANSACTIONS ON COMMUNICATIONS 1999年第6期47卷 844-855页

作者： Goeckel, DL Univ Massachusetts Dept Elect & Comp Engn Amherst MA 01003 USA

The idea of using knowledge of the current channel fading values to optimize the transmitted signal in wireless communication systems has attracted substantial research attention in recent years. However, the practicality of this adaptive signaling has been questioned due to the variation of the wireless channel over time, which results in a different channel at the time of data transmission than at the time of channel estimation. By characterizing the effects of fading channel variation on the adaptive signaling paradigm, it is demonstrated here that these misgivings are well founded, as the channel variation greatly alters the nature of the problem. The main goal of this paper is to employ this characterization of the effects of the channel variation to design adaptive signaling schemes that are effective for the time-varying channel, The design of uncoded adaptive quadrature amplitude modulation (QAM) systems is considered first, and it demonstrates the need to consider the channel variation in system design. This is followed by the main contribution of this paper;using only a single outdated fading estimate when neither the Doppler frequency nor the exact shape of the autocorrelation function of the channel fading process is known, adaptive trellis-coded modulation schemes are designed that can provide a significant increase in bandwidth efficiency over their nonadaptive counterparts on time-varying channels.

关键词： adaptive coding fading channels quadrature amplitude modulation time-varying channels trellis-coded modulation

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On-line adaptive canonical prefix coding with bounded compression loss

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IEEE TRANSACTIONS ON INFORMATION THEORY 2001年第1期47卷 88-98页

作者： Turpin, A Moffat, A Univ Melbourne Dept Comp Sci & Software Engn Melbourne Vic 3010 Australia

Semistatic minimum-redundancy prefix (MRP) coding is fast compared with rival coding methods, but requires two passes during encoding. Its adaptive counterpart, dynamic Huffman coding, requires only one pass over the input message for encoding and decoding, and is asymptotically efficient. Dynamic Huffman coding is, however, notoriously slow in practice. By removing the restriction that the code used for each message symbol must have minimum-redundancy and thereby admitting some compression loss, it is possible to improve the speed of adaptive MRP coding. This paper presents a controlled method for trading compression loss for coding speed by approximating symbol frequencies with a geometric distribution, The result is an adaptive MRP coder that is asymptotically efficient and also fast in practice.

关键词： adaptive coding Huffman coding minimum-redundancy coding (MRP) on-line coding

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Region-based image coding with multiple algorithms

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IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING 2001年第3期39卷 562-570页

作者： Petrou, M Hou, PX Kamata, S Underwood, CI Univ Surrey Sch Elect Comp & Math Guildford GU2 7XH Surrey England Kyushu Univ Grad Sch Informat Sci & Elect Engn Dept Intelligent Syst Fukuoka 81281 Japan

The wide usage of small satellite imagery, especially its commercialization, makes data-based onboard compression not only meaningful but also necessary in order to solve the bottleneck between the huge volume of data generated onboard and the very limited downlink bandwidth. In this paper, we propose a method that encodes different regions with different algorithms. We use three shape-adaptive image compression algorithms as the candidates. The first one is a JPEG-based algorithm, the second one is based on the object-based wavelet transform (OWT) method proposed by [1], and the third adopts Hilbert scanning of the regions of interest followed by one-dimensional (1-D) wavelet transform. The three algorithms are also applied to the full image so that we can compare their performance on a whole rectangular image. We use eight Landsat Th I multispectral images and another 12 small satellite single-band images as our data set. The results show that these compression algorithms have significantly different performance for different regions. For relatively smooth regions, e.g., regions that consist of a single type of vegetation or water areas etc, the 1-D wavelet method is the best. For highly textured regions, e.g., urban areas, mountain areas, and so on, the modified OWT method wins over the others. For the whole image, OWT working at whole image mode, which is just an ordinary 2-D wavelet compression, is the heat. Based on this, we propose a new data-based compression architecture that extracts particular regions according to the application of interest and then involves different algorithms to encode different regions in order to achieve better performance than traditional onboard compression schemes in which a fixed compression method is applied to the whole image no matter what the application is. This approach is most appropriate for use with images captured by microsatellites, which are commissioned for specific applications in which one knows a priori which cla

关键词： adaptive coding image coding region-based coding remote sensing

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adaptive coding of hyperspectral imagery

Adaptive coding of hyperspectral imagery

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International Conference on Acoustics, Speech, and Signal Processing (ICASSP)

作者： G.P. Abousleman Systems Solutions Group Motorola Scottsdale AZ USA

Two systems are presented for compression of hyperspectral imagery. These systems utilize adaptive classification, trellis-coded quantization, and optimal rate allocation. In the first system, DPCM is used for spectral decorrelation, while an adaptive wavelet-based coding scheme is used for spatial decorrelation. The second system uses DPCM in conjunction with an adaptive DCT-based coding scheme. In each system, entropy-constrained trellis-coded quantization (ECTCQ) is used to quantize the transform coefficients. Entropy-constrained codebooks are designed for generalized Gaussian distributions by using a modified version of the generalized Lloyd algorithm. The wavelet-based system compresses an AVIRIS hyperspectral test sequence at 0.118 bits/pixel/band, while retaining an average peak signal-to-noise ratio (PSNR) of 41.24 dB. The DCT-based system achieves the same bit rate with an average PSNR of 40.72 dB.

关键词： adaptive coding Hyperspectral imaging PSNR Quantization Decorrelation Image coding adaptive systems Algorithm design and analysis Gaussian distribution System testing

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adaptive coding in fading channels

Adaptive coding in fading channels

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AFRICON Conference

作者： C. Mitchell F. Swarts F. Aghdasi Department of Electrical Engineering University of the Witwatersrand South Africa Department of Electrical Engineering University of Pretoria South Africa

The use of an adaptive forward error control coding scheme is investigated on Rayleigh fading channels typically encountered in mobile communications systems. A predictive algorithm is used to estimate the fading intensity on the channel and this estimate is used to predict the code parameters. It is found that the use of the proposed scheme leads to an improvement in both the bit error rate performance and the throughput of the system.

关键词： adaptive coding Fading Programmable control adaptive control Error correction Mobile communication Prediction algorithms Rayleigh channels Bit error rate Throughput

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Low delay perceptually lossless coding of audio signals

Low delay perceptually lossless coding of audio signals

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Data Compression Conference (DCC 2001)

作者： Dorward, S Huang, DW Savari, SA Schuller, G Yu, B Bell Labs Lucent Technol Murray Hill NJ 07974 USA

ISBN: (纸本)0769510310

A novel predictive lossless coding scheme is proposed. The prediction is based on a new weighted cascaded least mean squared (WCLMS) method. To obtain both a high compression ratio and a very low encoding and decoding delay, the residuals from the prediction are encoded using either a variant of adaptive Huffman coding or a version of adaptive arithmetic coding. WCLMS is especially designed for music/speech signals. It can be used either in combination with psycho-acoustically pre-filtered signals (an idea presented in [1]) to obtain perceptually lossless coding, or as a stand-alone lossless coder. Experiments on a database of moderate size and a variety of pre-filtered mono-signals show that the proposed lossless coder (which needs about 2 bit/sample for pre-filtered signals) outperforms competing lossless coders, such as ppmz, bzip2, Shorten, and LPAC, in terms of compression ratios. The combination of WCLMS with either of the adaptive coding schemes is also shown to achieve better compression ratios and lower delay than an earlier scheme combining WCLMS with Huffman coding over blocks of 4096 samples.

关键词： compression ratio Huffman codes audio signals lossless coding lossless compression LPAC ENCODER adaptive coding Lossless DEcoding labeling scheme

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adaptive-rate coding for frequency-hop communications over Rayleigh fading channels

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IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS 1999年第7期17卷 1224-1232页

作者： Pursley, MB Wilkins, CS Clemson Univ Dept Elect & Comp Engn Clemson SC 29634 USA

Because of the variability of the channels in frequency-hop wireless systems and networks, the performance of error-control coding can be improved by adapting the rate of the code to the channel conditions. In this paper, adaptive-rate error-control coding is investigated for slow frequency-hop communications with Reed-Solomon coding. Two methods are investigated that use decoder side information as a means for selecting the code rate. These methods are based on counts of errors and erasures, which are provided by the demodulator and the decoder. The performance of the adaptive-rate coding system is evaluated for channels with Rayleigh fading, partial-band interference, and thermal noise.

关键词： adaptive coding frequency-hop communications spread-spectrum communications

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Enhanced static Fano coding

Enhanced static Fano coding

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IEEE International Conference on Systems, Man and Cybernetics

作者： L.G. Rueda B.J. Oommen School of Computer Science Carleton University Ottawa ONT Canada

Statistical coding techniques have been used for a long time in lossless data compression, using methods such as Huffman's algorithm, arithmetic coding, Shannon's method, Fano's method, etc. Most of these methods can be implemented either statically or adaptively. Canonical codes, in which the code words are arranged in a lexicographical order, are advantageous because they can be decoded extremely expediently. Although Huffman's algorithm is optimal, the generation of a canonical Huffman code is not straightforward. Conversely, while the Fano coding is sub-optimal, it can lead to canonical codes. In this paper, we resolve the dilemma by focusing on the static implementation of Fano's method. By taking advantage of the properties of the encoding schemes generated by this method, and the concept of "code word arrangement", we present an enhanced version of the static Fano's method, namely Fano/sup +/. We formally analyze Fanol by presenting some properties of Fano trees, and the theory of list rearrangements. Our enhanced algorithm achieves compression ratios arbitrarily close to those of Huffman's algorithm. Empirical results on files of the Canterbury corpus corroborate the almost-optimal efficiency of our enhanced algorithm and its canonical nature. We believe that the compression efficiency of Fano+ can be made to attain the compression ratios of the best known schemes if a structure model of the data is also incorporated.

关键词： Data compression Encoding Decoding Computer science Huffman coding Arithmetic adaptive coding

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