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Context-dependent coding and gain control in the auditory system of crickets

EUROPEAN JOURNAL OF NEUROSCIENCE 2015年第7期42卷 2390-2406页

作者： Clemens, Jan Rau, Florian Hennig, R. Matthias Hildebrandt, K. Jannis Humboldt Univ Dept Biol Behav Physiol Grp Berlin Germany Bernstein Ctr Computat Neurosci Berlin Berlin Germany Princeton Univ Princeton Neurosci Inst Princeton NJ 08540 USA Carl von Ossietzky Univ Oldenburg Cluster Excellence Hearing4all Dept Neurosci D-26111 Oldenburg Germany Carl von Ossietzky Univ Oldenburg Res Ctr Neurosensory Sci D-26111 Oldenburg Germany

Sensory systems process stimuli that greatly vary in intensity and complexity. To maintain efficient information transmission, neural systems need to adjust their properties to these different sensory contexts, yielding adaptive or stimulus-dependent codes. Here, we demonstrated adaptive spectrotemporal tuning in a small neural network, i.e. the peripheral auditory system of the cricket. We found that tuning of cricket auditory neurons was sharper for complex multi-band than for simple single-band stimuli. Information theoretical considerations revealed that this sharpening improved information transmission by separating the neural representations of individual stimulus components. A network model inspired by the structure of the cricket auditory system suggested two putative mechanisms underlying this adaptive tuning: a saturating peripheral nonlinearity could change the spectral tuning, whereas broad feed-forward inhibition was able to reproduce the observed adaptive sharpening of temporal tuning. Our study revealed a surprisingly dynamic code usually found in more complex nervous systems and suggested that stimulus-dependent codes could be implemented using common neural computations.

关键词： adaptive coding auditory coding cricket gain control inhibition

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Reduced adaptability, but no fundamental disruption, of norm-based face-coding mechanisms in cognitively able children and adolescents with autism

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NEUROPSYCHOLOGIA 2014年第1期62卷 262-268页

作者： Rhodes, Gillian Ewing, Louise Jeffery, Linda Avard, Eleni Taylor, Libby Univ Western Australia Sch Psychol ARC Ctr Excellence Cognit & Its Disorders Crawley WA 6009 Australia

Faces are adaptively coded relative to visual norms that are updated by experience. This coding is compromised in autism and the broader autism phenotype, suggesting that atypical adaptive coding of faces may be an endophenotype for autism. Here we investigate the nature of this atypicality, asking whether adaptive face-coding mechanisms are fundamentally altered, or simply less responsive to experience, in autism. We measured adaptive coding, using face identity aftereffects, in cognitively able children and adolescents with autism and neurotypical age- and ability-matched participants. We asked whether these aftereffects increase with adaptor identity strength as in neurotypical populations, or whether they show a different pattern indicating a more fundamental alteration in face-coding mechanisms. As expected, face identity aftereffects were reduced in the autism group, but they nevertheless increased with adaptor strength, like those of our neurotypical participants, consistent with norm-based coding of face identity. Moreover, their aftereffects correlated positively with face recognition ability, consistent with an intact functional role for adaptive coding in face recognition ability. We conclude that adaptive norm-based face-coding mechanisms are basically intact in autism, but are less readily calibrated by experience. (C) 2014 Elsevier Ltd. All rights reserved.

关键词： Autism Face recognition Face identity aftereffects adaptive coding Norm-based coding

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IMPROVEMENTS OF TRANSFORM coding ALGORITHM FOR MOTION-COMPENSATED INTERFRAME PREDICTION ERRORS - DCT SQ coding

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IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS 1987年第7期5卷 1068-1078页

作者： KANEKO, M HATORI, Y KOIKE, A KDD Research and Development Laboratories Inc. Tokyo Japan

A new hybrid coding method for transmitting videoconferencing images at a bit rate 384 kbits/s is proposed. Considering the characteristics of motion-compensated interframe prediction errors for typical videoconferencing scenes, a filter is introduced to separate pulsive components on which conventional discrete cosine transform (DCT) coding method does not work well. These separated pulsive components are coded by using scalar quantization (SQ). The remainder are DCT coded. For DCT coefficients, an adaptive coding method based on the classification of DCT coefficients is applied in order to improve the coding performance. Since the proposed method employs both DCT coding and SQ of prediction errors, it is named "DCT/SQ coding method." Experimental results show that the DCT/SQ coding method is effective to reduce so-called mosquito effects, and thus it can improve the quality of decoded images.

关键词： Transform coding Discrete cosine transforms Image coding Teleconferencing Bit rate Layout Filters Quantization adaptive coding Decoding

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Alternative Algorithms Involving Alphabetical coding and Limited Length Encoding in Lossless Data Compression of Text Files

Alternative Algorithms Involving Alphabetical Coding and Lim...

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International Symposium on Fundamentals of Electrical Engineering (ISFEE)

作者： Radescu, Radu Univ Politehn Bucuresti Fac Elect Telecommun & Informat Technol Appl Elect & Informat Engn Dept 1-3 Iuliu Maniu Blvd RO-061071 Bucharest Romania

ISBN: (纸本)9781467395755

coding algorithms are generally aimed at minimizing the output code length encoding speed once the code has been designed. Moreover, most codes use a binary alphabet. This paper examines other issues related to coding, such as additional constraints imposed on the channel. Code generation will be considered where there is a limit on code words. Limits the application of such systems is a practical example of data compression where fast decoding is essential. When all code words correspond to a single word in memory (usually 32 bits, but there are situations that take 64-bit) can be used canonical decoding. If the deadline cannot be guaranteed, however, required the use of slower decoding methods. This paper also deals with the alphabetic code generation, where lexicographic arrangement of words by their code symbols must correspond to the original order in which the symbols were taken coding system. When an alphabetic code is used to compress a database that can be sorted in the same, order they would have had if the database records were first decompressed and then sorted. It also corresponds to alphabetic code trees binary search trees, which have applications in a wide variety of search problems. Assumption that the symbols are sorted by probability is not suitable for this scenario. The problem of finding codes for non-binary alphabets channel will be examined in detail. The subsequent experimental results cover the problem of alphabetic coding and of limited length coding.

关键词： Data compression Source coding Compression algorithms adaptive coding Text processing

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MULTIPURPOSE HARDWARE FOR DIGITAL coding OF AUDIO SIGNALS

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IEEE TRANSACTIONS ON COMMUNICATIONS 1978年第11期26卷 1785-1788页

作者： JOHNSTON, JD GOODMAN, DJ BELL TEL LABS INC CRAWFORD HILL LABHOLMDELNJ 07733

We describe an adaptive coding system capable of representing audio frequency signals in a wide variety of digital code formats. To provide adaptive quantization, the step size is adjusted by voltage controlled amplifiers operating with analog control signals. Sine wave signal-to-noise ratio measurements demonstrate important relationships among the main code classifications: pcm, apcm, dpcm, adpcm. The multipurpose coder has proved a useful laboratory aid in the design of special purpose coders. After adjustment and evaluation of parameters using the multipurpose coder one proceeds to an economical, specialized design.

关键词： Hardware Size control Voltage control adaptive coding Frequency Programmable control adaptive control Quantization Signal to noise ratio Phase change materials

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To Code or Not to Code Across Time: Space-Time coding with Feedback

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IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS 2008年第8期26卷 1588-1598页

作者： Lin, Che Raghavan, Vasanthan Veeravalli, Venugopal V. Univ Illinois Coordinated Sci Lab Urbana IL 61801 USA Univ Illinois Dept Elect & Comp Engn Urbana IL 61801 USA

Space-time codes leverage the availability of multiple antennas to enhance the reliability of communication over wireless channels. While space-time codes have initially been designed with a focus on open-loop systems, recent technological advances have enabled the possibility of low-rate feedback from the receiver to the transmitter. The focus of this paper is on the implications of this feedback in a single-user multi-antenna system with a general model for spatial correlation. We assume a limited feedback model, that is, a coherent receiver and statistical knowledge at both the ends, along with B bits of error-free quantized channel information at the transmitter. We study space-time coding with a family of linear dispersion (LD) codes that meet an additional orthogonality constraint so as to ensure low-complexity decoding. Our results show that, when the number of bits of feedback (B) is small, a space-time coding scheme that is equivalent to beamforming and does not code across time is optimal in a weak sense in that it maximizes the average received SNR. As B increases, this weak optimality transitions to optimality in a strong sense that is characterized by the maximization of average mutual information. Thus, from a system designer's perspective, our work suggests that beamforming may not only be attractive from a low-complexity viewpoint, but also from an information-theoretic viewpoint.

关键词： adaptive coding diversity methods fading channels feedback communications MIMO systems multiplexing quantization

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Efficient Lossless coding of Highpass Bands from Block-based Motion Compensated Wavelet Lifting Using JPEG 2000

Efficient Lossless Coding of Highpass Bands from Block-based...

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IEEE Visual Communications and Image Processing Conference

作者： Schnurrer, Wolfgang Troeger, Tobias Richter, Thomas Seiler, Juergen Kaup, Andre Univ Erlangen Nurnberg Multimedia Commun & Signal Proc Cauerstr 7 D-91058 Erlangen Germany

ISBN: (纸本)9781479961399

Lossless image coding is a crucial task especially in the medical area, e.g., for volumes from Computed Tomography or Magnetic Resonance Tomography. Besides lossless coding, compensated wavelet lifting offers a scalable representation of such huge volumes. While compensation methods increase the details in the lowpass band, they also vary the characteristics of the wavelet coefficients, so an adaption of the coefficient coder should be considered. We propose a simple invertible extension for JPEG 2000 that can reduce the filesize for lossless coding of the highpass band by 0.8% on average with peak rate saving of 1.1%.

关键词： Computed Tomography Wavelet Lifting Signal Analysis adaptive coding Lossless Image coding

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REAL-TIME RATE-ADAPTABLE coding FOR FADING CHANNELS

REAL-TIME RATE-ADAPTABLE CODING FOR FADING CHANNELS

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IEEE Signal Processing and Signal Processing Education Workshop (SP/SPE)

作者： Schmidt, Sam Harrison, Willie K. Univ Colorado Colorado Springs Dept Elect & Comp Engn Colorado Springs CO 80918 USA

ISBN: (纸本)9781467391696

In this paper, a new adaptive-rate convolutional coding system for maximizing the throughput over slowly fading channels is presented. The scheme is capable of adapting on the fly to fading conditions without the delay inherent in ARQ-based adaptive-rate strategies. The system employs a bank of encoders, and the current encoder is selected as a function of the channel state information obtained through a periodically transmitted feedback training sequence. This scheme does not require rate compatibility in the code bank, and can therefore make use of the best-known codes of any rates with arbitrary constraint lengths. At the receiver, an innovative decoding method based on the well-known Viterbi algorithm is employed. Knowledge of the encoder choices is not required at the decoder due to its ability to seamlessly track encoder transitions through an expanded Viterbi trellis. The system provides a hassle-free solution to achieving high-rate communications over fading channels.

关键词： Viterbi algorithm adaptive coding fading forward error correction

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Research on Cascaded Turbo-STBC coding Based on GFDM-ROF System 10

Research on Cascaded Turbo-STBC Coding Based on GFDM-ROF Sys...

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10th International Conference on Information Optics and Photonics

作者： Wang, Bo Tian, Feng Zhang, Qi Wang, Yongjun Zhang, Lijia Tian, Qinghua Rao, Lan Xin, Xiangjun Beijing Univ Posts & Telecommun BUPT Sch Elect Engn Beijing Key Lab Space Ground Interconnect & Conve Xitucheng Rd 10 Beijing 100876 Peoples R China

ISBN: (纸本)9781510625808

ROF is the technology that integrates optical communication and wireless communication. It not only possesses the characteristics of high speed and long distance in optical communication, but also has the characteristics of flexible in wireless communication. GFDM is one of 5G's alternative technologies for high-frequency millimeter waves. This paper proposes and verifies that in the GFDM-ROF system with MIMO, cascaded Turbo-STBC coding can improve the reliability of the entire system. We use Turbo code as the out-of-channel code, and STBC code as the intra-channel code. When using two transmitting antennas and four receiving antennas and the SNR is higher than 5 dB, the BER is below 10(-6). Furthermore, based on this system, under high load communication conditions, we proposed an adaptive coding technology with excellent performance and it can reduce system load

关键词： GFDM-ROF Turbo-STBC adaptive coding

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An Asymptotically Optimal Two-Part coding Scheme for Networked Control under Fixed-Rate Constraints

An Asymptotically Optimal Two-Part Coding Scheme for Network...

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IEEE International Symposium on Information Theory (ISIT)

作者： Keeler, Jonathan Linder, Tamas Yuksel, Serdar

ISBN: (纸本)9781665421607;9781665421591

It is known that fixed rate adaptive quantizers can be used to stabilize an open-loop-unstable linear system driven by unbounded noise. These quantizers can be designed so that they have near-optimal rate, and the resulting system will be stable in the sense of having an invariant probability measure, or ergodicity, as well as the boundedness of the state second moment. However, results on the minimization of the state second moment for such quantizers, an important goal in practice, do not seem to be available. In this paper, we construct a two-part adaptive coding scheme that is asymptotically optimal in terms of the second moments as the data rate grows large. The first part, as in prior work, leads to ergodicity (via positive Harris recurrence) and the second part attains order optimality of the invariant second moment, resulting in near optimal performance at high rates.

关键词： Linear systems adaptive systems Minimization Encoding adaptive coding

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