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IEEE Conference on Wireless Communications and Networking

作者： E. Armanious D.D. Falconer H. Yanikomeroglu Broadband Communications and Wireless Systems Centre Department of Systems and Computer Engineering Carleton University Ottawa Canada

It is well known that link adaptation techniques, when designed to track the channel variations, yield a higher network throughput. In this work, we investigate the throughput returns due to the employment of various combinations of adaptive modulation, adaptive coding, and adaptive power control in a fixed cellular broadband wireless access system incorporating the effects of shadowing, multipath fading, and multiple access interference. The system considered is a multipoint multichannel distribution system (MMDS) with carrier frequency 2.5 GHz. It is observed that among all the possible combinations, the combination of adaptive modulation and adaptive coding (without power control) is the most efficient type since the further employment of adaptive power control only adds a relatively small improvement in the throughput. The frequency of occurrence of different constellation sizes and code rates with the percentages of the successful and failing links, are reported as well in this study.

关键词： Programmable control adaptive control Modulation coding adaptive coding Power control Throughput Employment Frequency Shadow mapping Fading

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Approaches to adaptive Reed-Solomon coding for OFDM systems

Approaches to adaptive Reed-Solomon coding for OFDM systems

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IEEE Conference on Vehicular Technology (VTC)

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Non-binary type-II HARQ and its application to an adaptive system

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INTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS 2005年第2期18卷 97-117页

作者： Zhang, LJ Li, VOK Cao, ZG Tsinghua Univ Dept Elect Engn Beijing 100084 Peoples R China Univ Hong Kong Dept Elect & Elect Engn Hong Kong Hong Kong Peoples R China

Non-binary type-II hybrid ARQ (HARQ), which combines shortened Reed-Solomon (RS) code with ARQ, is proposed. Its throughput is obtained by extending Lin and Yu's analysis of binary type-II HARQ The reliability and average delay are also obtained. The analytical results show that non-binary HARQ outperforms its binary counterpart in throughput, reliability and average delay when proper RS codes are selected. Non-binary HARQs are applied adaptively in a cellular phone system with uniformly distributed mobile terminals (MTs). MTs switch adaptively between two different hybrid schemes according to the average SNR of the received signals. The adaptive parameters include the size of the modulation constellation, the error-correction coding and their joint adaptation. Numerical results show that the adaptive scheme always outperforms its non-adaptive counterparts, and the adaptive modulation scheme is superior to adaptive coding and the joint adaptation scheme when the implementation complexity is a limiting factor. Robustness analysis shows that introducing a mixed modulation scheme in addition to QPSK and 8PSK in the adaptive modulation scheme is unnecessary, and HARQ with adaptive modulation is insensitive to deviations from the optimal threshold, thus facilitating its implementation. Copyright (C) 2004 John Wiley Sons, Ltd.

关键词： automatic-repeat-request (ARQ) non-binary type-II HARQ adaptive modulation adaptive coding robustness analysis

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adaptive scheduling and coding for time-varying links

Adaptive scheduling and coding for time-varying links

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International Conference on Communication Technology (ICCT)

作者： Yaxin Cao V.O.K. Li Department of Electrical and Electronic Engineering University of Hong Kong Hong Kong China

In dealing with wireless link variability, adaptive scheduling and adaptive coding each has its own advantages and disadvantages. These two approaches were mostly used separately. Existing work on wireless scheduling usually uses a coarse two-stage link model and assumes perfect link knowledge, while work on adaptive coding ignores bandwidth sharing among users. In reality, multiple users with time-varying and location dependent links share the transmission bandwidth in a wireless network, and the two approaches need to be integrated to achieve better utilization and finer fairness granularity. In this paper, we design a simple scheme that combines the adaptive scheduling and coding mechanisms. The scheme is applicable to general multiple-state Markov link model and enables tradeoff between bandwidth utilization and fairness granularity. Link state estimation and prediction errors are accounted for in decision-making. We also show that the optimal solution for maximizing bandwidth utilization is a special case of the general schemes.

关键词： adaptive scheduling Bandwidth adaptive coding Error correction codes Throughput Wireless communication Scheduling algorithm Wireless networks State estimation Decision making

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Rate-distortion analysis of backward adaptive transform coding schemes

Rate-distortion analysis of backward adaptive transform codi...

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

作者： D. Mary D.T.M. Slock Institut Eurecom Sophia-Antipolis France

The main advantage of backward over forward adaptive coding schemes is to update the coding parameters with the data available at the decoder, avoiding thereby any excess bit rate. The performances of two practical backward adaptive transform coding schemes are analyzed in terms of rate and distortion for two transforms: the KLT (Karhunen-Loeve transform) and the LDU transform (based on a lower-diagonal-upper factorization of the covariance matrix, R, of the data). For both algorithms, we model the expected distortion w.r.t. the number of vectors available at the decoder. Our analysis shows that, for an algorithm using Sheppard's correction on the second order moment estimates, the distortion should converge to the target distortion. Without this correction, the effects of backward adaptation are shown to move the actual r(D) point of the system from the target point by the same term for both transforms. Simulation results confirming the theoretic analysis are presented.

关键词： Rate-distortion Transform coding Karhunen-Loeve transforms Decoding adaptive coding Bit rate Performance analysis Rate distortion theory Covariance matrix Algorithm design and analysis

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Open loop rate-distortion optimized audio coding

Open loop rate-distortion optimized audio coding

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

作者： F. Norden M.G. Christensen S.H. Jensen Department of Communication Technology University of Aalborg Denmark

The paper addresses complexity reduced rate-distortion optimized audio coding under rate constraint. A technique where distortion minimizing coding templates, chosen from a set of templates, are jointly selected for a set of segments. This optimization requires knowledge of rate-distortion pairs for all segments, and for each coding template, which is often costly to obtain. The proposed framework exchanges true rate-distortion pairs with predicted ones, thereby allowing for complexity reduction. The prediction is based on a property vector extracted for each segment, from which distortion predictions, using Gaussian mixture models, are performed. Here, we evaluate the proposed framework in a sinusoidal coding context. The results show that the proposed framework can increase the distortion performance, compared to a fixed sinusoidal coding scheme.

关键词： Rate-distortion Audio coding Constraint optimization Predictive models Signal synthesis Communications technology adaptive coding Speech Distortion Signal analysis

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Sinusoidal Prediction for Waveform coding

Sinusoidal Prediction for Waveform Coding

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Asilomar Conference on Signals, Systems & Computers

作者： W.C. Chu Media Laboratory DoCoMo Communications Laboratory USA Inc. San Jose CA USA

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DVB-S2 coding modes for broadcasting and unicasting

DVB-S2 coding modes for broadcasting and unicasting

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International Symposium on Electronics in Marine (ELMAR)

作者： G. Gvozden M. Gosta S. Grgic Croatian Radio and Television Zagreb HR Croatia Croatian Telecommunications Agency Zagreb HR Croatia Zagreb Croatia Faculty of Electrical Engineering and Computing Zagreb HR Croatia

To provide cost effective and profitable broadband services, next generations of satellite system will have to apply new technologies in satellite equipment and communications payload designs. This article describes the second generation DVB-S2 transmission standard and its possibility to achieve greater performance and quality of signal in presence of interference and high level noise using constant, variable and adaptive coding and modulation modes

关键词： Digital video broadcasting Satellite broadcasting Artificial satellites Costs Payloads Signal generators Interference Noise generators Noise level adaptive coding

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On asymptotically optimal methods of prediction and adaptive coding for Markov sources

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JOURNAL OF COMPLEXITY 2002年第1期18卷 224-241页

作者： Ryabko, BY Topsoe, F Siberian State Univ Telecommun & Comp Sci Novosibirsk Russia Univ Copenhagen Dept Math Copenhagen Denmark

The problem of predicting a sequence x(1), x(2), ... generated by a discrete source with unknown statistics is considered. Each letter x(t+1) is predicted using information on the word x(1), x(2),...x(t) only. In fact, this problem is a classical problem which has received much attention. Its history can be traced back to Laplace. To estimate the efficiency of a method of prediction, three quantities are considered: the precision as given by the Kullback-Leibler divergence, the memory size of the program needed to implement the method on a computer, and the time required, measured by the number of binary operations needed at each time instant. A method is presented for which the memory size and the average time are close to the minimum. The results can readily be translated to results about adaptive coding. (C) 2001 Elsevier Science (USA).

关键词： prediction adaptive coding universal coding epsilon-capacity epsilon-net imaginary sliding window

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Frame buffer compression using a limited-size code book for low-power display systems

Frame buffer compression using a limited-size code book for ...

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Embedded Systems for Real-Time Multimedia (ESTIMedia)

作者： Hojun Shim Youngjin Cho Naehyuck Chang School of Computer Science & Engineering Seoul National University South Korea

Modern hand-held multimedia terminals consume significant power for their quality display devices. Due to 60Hz or higher LCD refresh operations, frame buffer memory and related buses become dominant power consumers. In this paper, we introduce an efficient frame buffer compression scheme that uses differential Huffman coding and its hardware implementation. The compression and decompression must be simple and not incur distinct power overhead involving no CPU operations. We have achieved both on-the-fly compression and high compression efficiency devising a limited-size code book, color-difference reduction techniques and an adaptive code book update scheme. On the MobileMark 2002 benchmark, our techniques reduce the frame buffer activity by 52% to 90%, saving up to 86mW including the overhead.

关键词： Books Image coding Liquid crystal displays Computer displays Energy consumption Huffman coding Hardware adaptive coding Lamps Graphics

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