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Performance analysis of centralised and distributed scheduling schemes for mobile multihop relay systems

IET COMMUNICATIONS 2017年第1期11卷 69-75页

作者： Kim, Taejoon An, Kwanghoon Yu, Heejung Chungbuk Natl Univ Sch Informat & Commun Engn Chungju Si 28644 South Korea Yeungnam Univ Dept Informat & Commun Engn 280 Deahak Ro Gyoungsan 38541 South Korea

For a mobile multihop relay (MMR) system, a centralised packet scheduling method is compared with a distributed packet scheduling method. The performance of the MMR system considering the joint effect of a finite-length queue and an adaptive modulation and coding scheme for base station and relay station is analysed. A finite state Markov chain (FSMC) describing the queue and channel state pairs' transitions for the MMR system is built. Moreover, a method of reducing the state space of the FSMC, which enables a hop-by-hop performance analysis of the MMR system without explosive growth in the number of states, is presented. Numerical and simulation results show that the proposed FSMC modelling is accurate and the performance of centralised scheduling becomes degraded because of increased mismatches between a scheduled modulation and coding scheme (MCS) level and the actual MCS level.

关键词： mobile radio relay networks (telecommunication) telecommunication scheduling adaptive modulation adaptive codes Markov processes queueing theory mobile multihop relay systems centralised packet scheduling method distributed packet scheduling method finite length queue adaptive modulation adaptive coding finite state Markov chain channel state hop-by-hop performance analysis

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Feature-selective Attention in Frontoparietal Cortex: Multivoxel Codes Adjust to Prioritize Task-relevant Information

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JOURNAL OF COGNITIVE NEUROSCIENCE 2017年第2期29卷 310-321页

作者： Jackson, Jade Rich, Anina N. Williams, Mark A. Woolgar, Alexandra Macquarie Univ Level 316 Univ Ave N Ryde NSW 2109 Australia

Human cognition is characterized by astounding flexibility, enabling us to select appropriate information according to the objectives of our current task. A circuit of frontal and parietal brain regions, often referred to as the frontoparietal attention network or multiple-demand (MD) regions, are believed to play a fundamental role in this flexibility. There is evidence that these regions dynamically adjust their responses to selectively process information that is currently relevant for behavior, as proposed by the adaptive coding hypothesis [Duncan, J. An adaptive coding model of neural function in prefrontal cortex. Nature Reviews Neuroscience, 2, 820-829, 2001]. Could this provide a neural mechanism for feature-selective attention, the process by which we preferentially process one feature of a stimulus over another? We used multivariate pattern analysis of fMRI data during a perceptually challenging categorization task to investigate whether the representation of visual object features in the MD regions flexibly adjusts according to task relevance. Participants were trained to categorize visually similar novel objects along two orthogonal stimulus dimensions (length/orientation) and performed short alternating blocks in which only one of these dimensions was relevant. We found that multivoxel patterns of activation in the MD regions encoded the task-relevant distinctions more strongly than the task-irrelevant distinctions: The MD regions discriminated between stimuli of different lengths when length was relevant and between the same objects according to orientation when orientation was relevant. The data suggest a flexible neural system that adjusts its representation of visual objects to preferentially encode stimulus features that are currently relevant for behavior, providing a neural mechanism for feature-selective attention.

关键词： dimensions Stimuli brain region current task adaptive coding Nervous System Physiological Phenomena Pattern analysis

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Dynamic Rain Attenuation Model for Millimeter Wave Network Analysis

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IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS 2017年第1期16卷 441-450页

作者： Peric, Miroslav V. Peric, Dragana B. Todorovic, Branislav M. Popovic, Miroslav V. VLATACOM Inst High Technol Belgrade 11070 Serbia RT RK Inst Comp Based Syst Novi Sad 21000 Serbia Univ Novi Sad Fac Tech Sci Novi Sad 21000 Serbia

In millimeter wave networks, a received signal level and interference dynamically vary due to rain attenuation. These physical layer variations have influence on upper communication layers, which yield to variable network capabilities to serve traffic demands. Standards and agreements between service providers and users usually specify performance objectives at annual level. In order to make realistic annual level performance analysis of such networks, a new computationally efficient dynamic rain attenuation model is proposed and analyzed. The model reproduces assumed rain statistics at annual level: cumulative distribution function (cdf) of rain intensity, number of rain events in which specified rain intensity threshold is exceeded, rain advection vector intensity, and rain advection vector azimuth. Derivation of model parameter tolerances is based on the experimental results from dense rain gauge network. As an example of model application, annual level cdfs of node-to-node connection capacity in a test network are calculated.

关键词： Millimeter wave propagation rain attenuation routing protocols adaptive modulation adaptive coding

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Applications of Capacity Limits to Performance Analyses of adaptive Transmission Protocols for Packet Radios

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IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY 2017年第1期66卷 71-78页

作者： Borkotoky, Siddhartha S. Pursley, Michael B. Clemson Univ 303 EIB Clemson SC 29634 USA

Analytical methods are provided for use in performance evaluations, tradeoff studies, and preliminary designs of adaptive modulation and coding protocols that obtain their control information from practical sources. Our approach employs capacity limits and Markov chain models of fading to give analytical results on the throughput achieved by adaptive transmission in packet radio systems. The analytical methods replace simulations of the modem, iterative decoder, and time-varying fading channel. The amount of processor time required for protocol performance evaluations is decreased by several orders of magnitude.

关键词： adaptive coding adaptive modulation fading channels information theory packet radio

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A Multiplexed, Heterogeneous, and adaptive Code for Navigation in Medial Entorhinal Cortex

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NEURON 2017年第2期94卷 375-+页

作者： Hardcastle, Kiah Maheswaranathan, Niru Ganguli, Surya Giocomo, Lisa M. Stanford Univ Dept Neurobiol Sch Med Stanford CA 94305 USA Stanford Univ Dept Appl Phys Stanford CA 94305 USA

Medial entorhinal grid cells display strikingly symmetric spatial firing patterns. The clarity of these patterns motivated the use of specific activity pattern shapes to classify entorhinal cell types. While this approach successfully revealed cells that encode boundaries, head direction, and running speed, it left a majority of cells unclassified, and its pre-defined nature may have missed unconventional, yet important coding properties. Here, we apply an unbiased statistical approach to search for cells that encode navigationally relevant variables. This approach successfully classifies the majority of entorhinal cells and reveals unsuspected entorhinal coding principles. First, we find a high degree of mixed selectivity and heterogeneity in superficial entorhinal neurons. Second, we discover a dynamic and remarkably adaptive code for space that enables entorhinal cells to rapidly encode navigational information accurately at high running speeds. Combined, these observations advance our current understanding of the mechanistic origins and functional implications of the entorhinal code for navigation.

关键词： Multiplexed-coding spatial navigation adaptive coding tuning heterogeneity entorhinal cortex encoding mode computational models of spatial coding

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Analytical evaluation of adaptive coding for Markov models of Nakagami fading

Analytical evaluation of adaptive coding for Markov models o...

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Information Theory and Applications Workshop, ITA

作者： Jason D. Ellis Michael A. Juang Michael B. Pursley Clemson University USA

Packet radio systems that communicate over channels with slow fading experience changes in propagation loss from one packet to the next. In order to maintain high throughput, it is necessary for the packet radios to adapt their transmissions in response to changes in the channel. Practical adaptive coding protocols can respond to such changes by adjusting the code rate to maximize the expected throughput for each packet transmission. Performance evaluations for practical protocols typically require simulation of both the time-varying fading process and the adaptive protocol. We employ recently developed finite-state Markov models of Nakagami-m fading to obtain analytical evaluations of the throughput of an adaptive coding protocol. In our approach, neither the fading processes nor their Markov models are simulated.

关键词： Protocols Fading Throughput Adaptation models Markov processes Analytical models adaptive coding

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adaptive Code Refinement: A Compiler Technique and Extensions to Generate Self-Tuning Applications 24

Adaptive Code Refinement: A Compiler Technique and Extension...

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IEEE 24th International Conference on High Performance Computing Workshops (HiPCW)

作者： Schmitt, Maxime Helluy, Philippe Bastoul, Cedric Univ Strasbourg Inria Strasbourg France

ISBN: (纸本)9781538622933

Compiler high-level automatic optimization and parallelization techniques are well suited for some classes of simulation or signal processing applications, however they usually don't take into account domain-specific knowledge nor the possibility to change or to remove some computations to achieve "good enough" results. Differently, production simulation and signal processing codes have adaptive capabilities: they are designed to compute precise results only where it matters if the complete problem is not tractable or if computation time must be short. In this paper, we present a new way to provide adaptive capabilities to compute-intensive codes automatically. It relies on domain-specific knowledge provided through special pragmas by the programmer in the input code and on polyhedral compilation techniques to continuously regenerate at runtime a code that performs heavy computations only where it matters. We present experimental results on several applications where our strategy enables significant computation savings and speedup while maintaining a good precision, with a minimal effort from the programmer.

关键词： Monitoring Computational modeling Kernel Optimization Approximation algorithms adaptive coding Signal processing

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Segmentation of Source Symbols for adaptive Arithmetic coding

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IEEE TRANSACTIONS ON BROADCASTING 2012年第2期58卷 228-235页

作者： Zhang, Liang Wang, Demin Zheng, Dong Commun Res Ctr Canada Ottawa ON K2H 8S2 Canada

adaptive arithmetic coding is a general technique for coding source symbols of a stochastic process based on an adaptive model. The adaptive model provides measures of the statistics of source symbols and is updated, along with encoding/decoding processes, when more encoded/decoded symbols are fed as samples to the adaptive model. The coding performance depends on how well the adaptive model fits the statistics of source symbols. If the number of source symbols is large and the number of samples is small, the adaptive model may not be able to provide valid measures of the statistics, which results in an inefficient coding performance of the adaptive arithmetic coder. To this end, this paper presents segmentation of source symbols to improve the performance of the adaptive arithmetic coder. Each source symbol is divided into several segments. Each segment is separately coded with an adaptive arithmetic coder. With this division, possible values of each segment are concentrated within a small range. Given the limited number of samples, this concentration leads to a better fit of the adaptive model to the statistics of source symbols and therefore to an improvement of the coding efficiency. The proposed coding algorithm is applied to lossless motion vector coding for video transmission as an application example to show its performance improvement and coding gains.

关键词： adaptive coding predictive coding signal representations vector quantization video coding video compression

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Real-Time adaptive LDPC Coded APSK for Aeronautical Telemetry 13

Real-Time Adaptive LDPC Coded APSK for Aeronautical Telemetr...

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13th International Conference on Advanced Technologies, Systems and Services in Telecommunications (TELSIKS)

作者： Zou, Ding Djordjevic, Ivan. B. Univ Arizona Dept Elect & Comp Engn 1230 E Speedway Blvd Tucson AZ 85719 USA

ISBN: (纸本)9781538618004

In this paper, we consider the design of capacity-approaching forward error correction (FEC) coded amplitude phase shift keying (APSK) modulation schemes for use in the aeronautical telemetry. By maximizing the mutual information, we first investigate the designs of APSK modulations suitable for communication over nonlinear wireless channels. Then we propose a unified FPGA-based hardware-efficient architecture which combines the capacity-approaching LDPC decoders with four APSK modulation formats, including Gray-mapping-based 8-APSK, 16-APSK, 32-APSK, and 64-APSK. The proposed architecture allows the flexibility of the FEC-encoded signal to be received by legacy test-range systems. The emulation results show that such an LDPC-coded modulation scheme can adapt to wide range of received signal-to-noise ratios, ranging from 9.4 dB to 21.4 dB, by using different LDPC codes and/or modulation formats.

关键词： Aeronautical telemetry LDPC coding APSK FPGA coded modulation adaptive coding

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adaptive coding for Frequency-Hop Transmission over Fading Channels with Partial-Band Interference

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IEEE TRANSACTIONS ON COMMUNICATIONS 2011年第3期59卷 854-862页

作者： Masse, Michael R. Pursley, Michael B. Skinner, Jason S. Clemson Univ Dept Elect & Comp Engn Clemson SC 29634 USA

Protocols that were proposed recently for adapting the error-control code from packet to packet in a frequency-hop packet radio network are evaluated for use on channels for which the fading distribution has fixed or slowly varying parameters. The protocols do not require channel measurements or pilot signals;instead, the receiver derives the necessary adaptation control information from its decoder during of the reception of each packet. The throughput achieved by each adaptive-coding protocol when it is used with a family of turbo product codes is compared with the capacity limit and with the throughput that is obtained from a hypothetical ideal protocol that is given perfect channel state information.

关键词： Frequency-hop spread spectrum adaptive coding fading channels

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