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IEEE Globecom 2006

作者： Ashok K. Karmokar Vijay K. Bhargava Department of Electrical and Computer Engineering University of British Columbia Vancouver BC Canada

We study coding and modulation rate adaptation problem for HARQ systems with partially observable state from cross-layer viewpoint. The rate of convolutionally coded M-QAM is adapted jointly with buffer state and channel state. We assume that perfect channel state information is not known at the transmitter, but it can be estimated from previous actions and observations. POMDP-based approach is utilized to formulate the problem, where average throughput is maximized, and average delay, packet error rate and overflows are minimized. To solve the cross-layer adaptation problem approximately, we discuss two heuristic-based methods and compare their applicability with completely observable channel state case by simulation results.

关键词： adaptive coding Modulation coding Automatic repeat request Fading Convolutional codes Channel state information Transmitters State estimation Throughput Delay

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REGION adaptive SPECTRAL TRANSFORMATION FOR WAVELET BASED COLOR IMAGE COMPRESSION

REGION ADAPTIVE SPECTRAL TRANSFORMATION FOR WAVELET BASED CO...

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16th IEEE International Conference on Image Processing

作者： Bayazit, Ulug Istanbul Tech Univ TR-80626 Istanbul Turkey

ISBN: (纸本)9781424456536

In general, each region of a color image exhibits different spectral characteristics. Therefore, the energy compaction characteristic of a single global spectral transformation is rather weak for compression purposes. In this paper, we propose that different groups of wavelet coefficients of a color image be subjected to different spectral transformations prior to the spectral planes being coded by a wavelet-based image coder such as CSPIHT (Color Set Partitioning in Hierarchical Trees, [7]). The decomposition of the color image into such groups is succintly represented with a quadtree structure which is optimized for rate-distortion performance by means of a known analytical rate-distortion model for wavelet-based image codecs. The experiments show that, when integrated with the CSPIHT coder, the proposed region adaptive transformation method yields compression gains of 0.4-0.5 dB, on the average, for rates between 0.5bpp and 2.5bpp over the single global transformation method.

关键词： Color image coding adaptive coding Karhunen Loeve transforms quadtrees

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A fast and efficient nearly-optimal adaptive Fano coding scheme

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INFORMATION SCIENCES 2006年第12期176卷 1656-1683页

作者： Rueda, Luis Oommen, B. John Carleton Univ Sch Comp Sci Ottawa ON K1S 5B6 Canada Univ Windsor Sch Comp Sci Windsor ON N9B 3P4 Canada

adaptive coding techniques have been increasingly used in lossless data compression. They are suitable for a wide range of applications, in which on-line compression is required, including communications, internet, e-mail, and e-commerce. In this paper, we present an adaptive Fano coding method applicable to binary and multi-symbol code alphabets. We introduce the corresponding partitioning procedure that deals with consecutive partitionings, and that possesses, what we have called, the nearly-equal-probability property, i.e. that satisfy the principles of Fano coding. To determine the optimal partitioning, we propose a brute-force algorithm that searches the entire space of all possible partitionings. We show that this algorithm operates in polynomial-time complexity on the size of the input alphabet, where the degree of the polynomial is given by the size of the output alphabet. As opposed to this, we also propose a greedy algorithm that quickly finds a sub-optimal, but accurate, consecutive partitioning. The empirical results on real-life benchmark data files demonstrate that our scheme compresses and decompresses faster than adaptive Huffman coding, while consuming less memory resources. (c) 2005 Elsevier Inc. All rights reserved.

关键词： adaptive coding Fano coding data compression

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Diversity Investigation of Satellite Backbone Network for BFWA Systems

Diversity Investigation of Satellite Backbone Network for BF...

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International Workshop on Satellite and Space Communications

作者： Kantor, Peter Toth, Gabor Drozdy, Arpad Bito, Janos Budapest Univ Technol & Econ Dept Broadband Infocommun & Electromagnet Theory H-1117 Budapest Hungary

ISBN: (纸本)9781424443840

The Broadband Fixed Wireless Access (BFWA) networks are terrestrial systems operating at high carrier frequencies (above 20 GHz), therefore one of the most harmful circumstantial factors in these systems is the attenuation caused by precipitation, especially by rain. Employing site diversity is a well-known method to improve the signal to interference plus noise ratio conditions within the BFWA network. The backbone of a BFWA can be wired or wireless terrestrial, however the connection between base stations and the operator's core network can be also established by high frequency satellite links. Applying a satellite backbone system and route diversity between the Earth-space links can compensate precipitation attenuation. In this paper the efficiency of the diversity scheme in a satellite backbone network for BFWA system will be presented.

关键词： satellite backbone network BFWA diversity methods rain fading adaptive coding

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Decoder Description Syntax for fully configurable video coding

Decoder Description Syntax for fully configurable video codi...

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IEEE International Conference on Image Processing

作者： J. M. Philp C. S. Kannangara M. Bystrom M. de Frutos Lopez I. E. Richardson Robert Gordon University Aberdeen UK Boston University Boston MA USA Universidad Carlos III de Madrid Spain

Fully configurable video coding is a novel approach to video compression in which a video decoder can be dynamically constructed based on a decoder description. This paper presents a new syntax for describing video decoder functionality and structure, namely, the decoder description syntax (DDS). The DDS is a platform-independent syntax that can define all aspects of a video decoder in terms of basic processing instructions. We present examples of video decoding functions implemented in the DDS and show that flexible configuration, reconfiguration, and decoding of video can be achieved using a real-time prototype universal video decoder.

关键词： Decoding Video coding Video compression Automatic voltage control Technological innovation adaptive coding Libraries Codecs Prototypes Communication standards

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An efficient coding method for intra prediction mode information

An efficient coding method for intra prediction mode informa...

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IEEE International Symposium on Circuits and Systems (ISCAS)

作者： Kai Zhang Xiangyang Ji Qian Huang Debin Zhao Wen Gao Chinese Academy and Sciences Beijing China Institute of Computing Technology Chinese Academy and Sciences Beijing China Chinese Academy of Sciences Beijing Beijing CN

ISBN: (纸本)9781424438273

In H.264/AVC, the bits used for the Intra_4times4 prediction mode information usually occupy a high percentage in intra coding. Towards this issue, we present an efficient coding method for the Intra_4times4 prediction mode information. Firstly, a 3-order Markov random field is introduced to model the correlation among neighboring 4times4 blocks at picture level. Secondly, based on the conditional probabilities learned in this model, we build up a context adaptive coding scheme to code the Intra_4times4 prediction mode information. Although the probabilities and the coding scheme are initialized off-line, they can be revised by automatic adjustments. Thus the proposed algorithm is robust to a variety of video sequences. Experimental results demonstrate that the proposed method can obtain a gain up to 0.3 dB in all I-frames coding without involving any serious computational burden.

关键词： Automatic voltage control Predictive models Markov random fields Robustness Video coding Computers Performance gain Context modeling adaptive coding Video sequences

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adaptive modulation and coding (AMC) for bit-interleaved coded OFDM (BIC-OFDM)

Adaptive modulation and coding (AMC) for bit-interleaved cod...

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IEEE International Conference on Communications (ICC 2004)

作者： Song, Kee-Bong Ekbal, Amal Chung, Seong Taek Cioffi, John M. Stanford Univ Dept Elect Engn Stanford CA 94305 USA

ISBN: (纸本)0780385330

This paper proposes adaptive modulation and coding (AMC) as a method for the bit-interleaved coded OFDM (BIC-OFDM) packet transmission. Following a pair-wise error probability (PEP) analysis of AMC-BIC-OFDM in a slowly fading frequency selective channel, AMC scheme maximizes the total rate by optimally selecting the code and efficiently allocating rate and power over the frequency band. The proposed method improves upon the performance of uniform rate and power allocation scheme by 6.5 to 10 dB.

关键词： BICM adaptive coding adaptive modulation AMC rate and power allocation coded OFDM BICM capacity

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TRANSPONDERS: Research and analysis for the development of telecommunication payloads in Q/v bands

TRANSPONDERS: Research and analysis for the development of t...

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IEEE Conference on Aerospace

作者： C. Stallo M. Lucente T. Rossi E. Cianca M. Ruggieri A. Paraboni C. Cornacchini A. Vernucci M. T. Nocerino A. Ceccarelli L. Bruca G. Codispoti M. De Sanctis Department of Electronic Engineering University of Roma Tor Vergata Rome Italy DEI Politecnico di Milano Italy Space Engineering S.p.A. Rome Italy Thales Alenia Space Rome Italy Telespazio S.P.A Rome Italy Italian Space Agency Rome Italy

Since the 70s Italy has had a pioneering approach to higher frequencies, at first at Ka band (20/30 GHz) with the Sirio experience (launched in 1978), when such a range was still a frontier, and then with Italsat F1 and F2 experiments in the 90s, studying Q and V bands in addition to Ka one as well. After those experiences, Italy through the Italian space agency (ASI) was one of the first European countries that have made an effort toward the exploitation of Q/V band in telecommunications. In 2004 ASI funded a feasibility study (phase A), called TRANSPONDERS, Italian acronym for ldquoresearch, analysis and study of Q/V payloads for telecommunicationsrdquo, aimed at studying and designing a payload to be used to fully characterize the channel at Q/V bands and to test novel adaptive interference/fading mitigation techniques such as ACM (adaptive coding and modulation). Finally, the feasibility and performance of preliminary broadband services in such frequencies can be verified through this study. A new phase has recently started (April 2008), called TRANSPONDERS-2 and leaded by Space Engineering S.p.A., to continue the achievements gained during the first phase. In this scenario, it is mandatory to identify pre-operative experimental missions aiming at fully verifying the feasibility of future Q/V bands satellite telecommunication applications. The experimental goals are mainly to test the effectiveness of propagation impairment mitigation techniques (PIMTs) in such frequency bands and the minimization of implementation risks for operative system characterized by a series of technological challenges.

关键词： Transponders Payloads Frequency Testing Interference Fading adaptive coding Phase modulation Modulation coding Artificial satellites

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adaptive uplink MAC for CDMA-based cognitive radio networks

Adaptive uplink MAC for CDMA-based cognitive radio networks

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MILCOM, Military Communications Conference

作者： Hang Su Xi Zhang Networking and Information Systems Laboratory Department of Electrical and Computer Engineering Texas A and M University College Station TX USA

ISBN: (纸本)9781424452385

This paper proposes an adaptive code division multiple access (CDMA) based cognitive medium access control (MAC) scheme for uplink cognitive radio networks. The proposed scheme addresses the joint channel sensing and data transmission, power and rate assignments, and long-term fairness. Under our proposed scheme, the secondary users (SUs) can adaptively select either the intrusive spectrum sharing or non-intrusive spectrum sharing operations to transmit data to secondary base station (SBS) based on the channel utilization, traffic load, and the interference constraints. Our proposed scheme enables the SUs to efficiently utilize the frequency spectrum which is licensed to the primary users (PUs) while rigorously limiting the interference to the PUs. Also conducted are simulations to validate and verify our proposed scheme.

关键词： Cognitive radio Multiaccess communication Interference constraints Frequency synchronization Programmable control adaptive control Information systems Laboratories adaptive coding Media Access Protocol

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adaptive code partitioning for fast h0andover in IEEE 802.16e systems

Adaptive code partitioning for fast h0andover in IEEE 802.16...

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IEEE Radio and Wireless Symposium (RWS formerly RAWCON)

作者： Dae-Cheol Kwon Bongjhin Shin Daehyoung Hong Suwon Lee Heejin Jang Department of Electronics engineering Sogang University Seoul South Korea Samsung Advanced Institute of Technology Suwon Gyeonggi South Korea

Ranging is one of the major sources of handover latency in IEEE802.16e systems. It is due to the retransmission of ranging signals because of collision in contention based ranging. To reduce the handover latency, we need to make the possibility of retransmission low. We propose an adaptive code partitioning scheme that we utilize for fast handover in this paper. This scheme allocates a portion of codes only for the retransmission of ranging signals. The portion of this region is also adjusted adaptively in this scheme. Performance of the proposed scheme is evaluated by simulation. We analyzed the system capacity or the number of MSs that can be supported with reliable handover. Simulation results show that the proposed scheme leads to about 28.6% capacity improvement.

关键词： adaptive coding Delay Chromium Multiaccess communication Downlink OFDM Resource management Wireless communication Standards development Data communication

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