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Total system energy minimization for wireless image transmission

JOURNAL OF VLSI SIGNAL PROCESSING SYSTEMS FOR SIGNAL IMAGE AND VIDEO TECHNOLOGY 2001年第1-2期27卷 99-117页

作者： Appadwedula, S Goel, M Shanbhag, NR Jones, DL Ramchandran, K Univ Illinois Dept Elect & Comp Engn Coordinated Sci Lab Urbana IL 61801 USA Univ Calif Berkeley Dept Elect Engn & Comp Sci Berkeley CA 94720 USA

In this paper, we focus on the total-system-energy minimization of a wireless image transmission system including both digital and analog components. Traditionally, digital power consumption has been ignored in system design, since transmit power has been the most significant component. However, as we move to an era of pico-cell environments and as more complex signal processing algorithms are being used at higher data rates, the digital power consumption of these systems becomes an issue. We present an energy-optimized image transmission system for indoor wireless applications which exploits the variabilities in the image data and the wireless multipath channel by employing dynamic algorithm transformations and joint source-channel coding. The variability in the image data is characterized by the rate-distortion curve, and the variability in the channel characteristics is characterized by the path-loss and impulse response of the channel. The system hardware configuration space is characterized by the error-correction capability of the channel encoder/decoder, number of powered-up fingers in the RAKE receiver, and transmit power of the power amplifier. An optimization algorithm is utilized to obtain energy-optimal configurations subject to end-to-end performance constraints. The proposed design is tested over QCIF images, IMT-2000 channels and 0.18 mum, 2.5 V CMOS technology parameters. Simulation results over various images, various distances, two different channels, and two different rates show that the average energy savings in utilizing a total-system-energy minimization over a fixed system (designed for the worst image, the worst channel and the maximum distance) are 53.6% and 67.3%, respectively, for short-range (under 20 m) and long-range (over 20 m) systems.

关键词： joint source-channel coding low power indoor wireless transmission energy minimization

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Scalable, error-resilient, and high-performance video communications in mobile wireless environments

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IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS FOR VIDEO TECHNOLOGY 2001年第7期11卷 833-847页

作者： Vass, J Zhuang, S Zhuang, XH Eyeball Networks Inc Vancouver BC V7T 1A2 Canada Univ Calif Berkeley Dept Elect Engn & Comp Sci Berkeley CA 94720 USA Univ Missouri Dept Comp Engn & Comp Sci Columbia MO 65211 USA

A novel mobile communications system is proposed in the paper, which provides not only effective but also efficient video access for mobile users when communicating over low-bandwidth error-prone wireless links, The middleware implemented by a mobile proxy server at the mobile support station is designed for the seamless integration of mobile users with video servers, so the specific details of the underlying protocols and source/channel coding techniques are hidden to both the video server and mobile client. Based on the concept of application-level framing, the application (video codec in our case) plays a significant role in network communications that most of functionalities of the system are implemented as part of the application, As such, at the application layer, adaptive source- and channel-coding techniques are developed to jointly provide the user with the highest possible video quality, For efficient source coding, our high-performance low-complexity video-coding algorithm called a 3-D significance-linked connected component analysis (3D-SLCCA) is chosen, Due to its high robustness against channel-error propagation, 3D-SLCCA is well suited for wireless environments. For error-resilient channel coding, a multilayer transmission error-control mechanism is developed, Since there is no additional requirement imposed on either the mobile client or the video server, mobile users interact with the server in exactly the same way as stationary users, Extensive computer experiments demonstrate the effectiveness of the proposed system.

关键词： error-resilient coding joint source-channel coding mobile communications proxy server scalable coding SLCCA video coding

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Reed-Solomon decoding algorithms for digital audio broadcasting in the AM band

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IEEE TRANSACTIONS ON BROADCASTING 2001年第2期47卷 115-122页

作者： Laneman, JN Sundberg, CEW Lucent Technol Bell Labs Multimedia Commun Res Lab Murray Hill NJ 07974 USA

Digital audio broadcasting (DAB) systems for the AM band are being developed to provide higher-quality radio broadcasts, broader coverage, and data services. Transmission is typically done by means of multistreaming with QAM/OFDM in the high bits/sec/Hz regime, in which Reed-Solomon codes, either alone or in concatenation with inner trellis coded modulation (TCM), are natural choices for error control. For the AM DAB application, Reed-Solomon codes with suboptimal decoders of the bounded-distance type offer error correction important for bringing down the error probability, but also offers error detection important for generating block detected-error flags for use in the error concealment, or error mitigation, algorithm in the audio decoder. For multistream systems, the block detected-error flags can also be used to select the component streams retained by the audio decoder. In this paper, we evaluate the performance of Reed-Solomon codes in terms of both detected (flag) and undetected error rates for DAB applications. We provide simulation results for a variety of decoding algorithms, including hard-decision decoding (HDD), successive-erasure decoding (SED), and fixed-erasure decoding (FED), and discuss the channel environments in which each of these algorithms may be appropriate. Among other results, for example, we address the issue of matching the blocklength of the Reed-Solomon code to the audio decoder with its variable frame structure. From our simulation results for HDD, we conclude that the increased error correction capability of longer Reed-Solomon codes more than compensates for the mismatch in terms of error mitigation in the audio decoder. We also observe that SED provides only small improvements for uniform interference channels, while FED offers considerable improvements for some partial-band interference channels. We describe an appealing two-mode adaptive configuration using HDD and FED for mitigating partial-band interference caused by some second

关键词： bounded-distance decoding digital audio broadcasting (DAB) error mitigation generalized minimum-distance decoding joint source-channel coding Reed-Solomon codes

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On the iterative approximation of optimal joint source-channel decoding

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IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS 2001年第9期19卷 1662-1670页

作者： Görtz, N Univ Kiel Fac Engn Inst Circuits & Syst Theory Kiel Germany

joint source-channel decoding is formulated as an estimation problem. The optimal solution is stated and it is shown that it is not feasible in many practical systems due to its complexity. Therefore, a novel iterative procedure for the approximation of the optimal solution is introduced, which is based on the principle of iterative decoding of turbo codes. New analytical expressions for different types of information in the optimal algorithm are used to derive the iterative approximation. A direct comparison of the performances of the optimal algorithm and its iterative approximation is given for a simple transmission system with "short" channel codewords. Furthermore, the performance of iterative joint source-channel decoding is investigated for a more realistic system.

关键词： concatenated codes iterative decoding joint source-channel coding MAP algorithm soft-in/soft-out decoding turbo (de)coding

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Soft-decision COVQ for turbo-coded AWGN and Rayleigh fading channels

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IEEE COMMUNICATIONS LETTERS 2001年第6期5卷 257-259页

作者： Zhu, GC Alajaji, FI Queens Univ Dept Math & Stat Kingston ON K7L 3N6 Canada Queens Univ Dept Elect & Comp Engn Kingston ON K7L 3N6 Canada

A robust soft-decision channel-optimized vector quantization (COVQ) scheme for Turbo-coded additive white Gaussian noise (AWGN) and Rayleigh fading channels is proposed. The log likelihood ratio (LLR) generated by the Turbo decoder is exploited via the use of a q-bit scaler soft-decision demodulator, The concatenation of the Turbo encoder, modulator, AWGN channel or Rayleigh fading channel, Turbo decoder, and q-bit soft-decision demodulator is modeled as an expanded discrete memoryless channel (DMC), A COVQ scheme for this expanded discrete channel is designed. Numerical results indicate substantial performance improvements over traditional tandem coding systems, COVQ schemes designed for hard-decision demodulated Turbo-coded channels(q = 1), as well as performance gains over a recent soft decoding COVQ scheme by Ho.

关键词： AWGN channels channel-optimized vector quantization joint source-channel coding Rayleigh fading channels soft-decision demodulator turbo codes

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joint turbo decoding and estimation of hidden Markov sources

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IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS 2001年第9期19卷 1671-1679页

作者： Garcia-Frias, J Villasenor, JD Univ Delaware Dept Elect & Comp Engn Newark DE 19716 USA Univ Calif Los Angeles Dept Elect Engn Los Angeles CA 90024 USA

We describe a joint source-channel scheme for modifying a turbo decoder in order to exploit the statistical characteristics of hidden Markov sources. The basic idea is to treat the trellis describing the hidden Markov source as another constituent decoder which exchanges information with the other constituent decoder blocks. The source block uses as extrinsic information the probability of the input bits that is provided by the constituent decoder blocks. On the other hand, it produces a new estimation of such a probability which will be used as extrinsic information by the constituent turbo decoders. The proposed joint source-channel decoding technique leads to significantly improved performance relative to systems in which source statistics are not exploited and avoids the need to perform any explicit source coding prior to transmission. Lack of a priori knowledge of the source parameters does not degrade the performance of the system, since these parameters can be jointly estimated with turbo decoding.

关键词： Baum-Welch algorithm hidden Markov sources iterative decoding joint source-channel coding turbo codes

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joint source-channel coding and guessing with application to sequential decoding

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IEEE TRANSACTIONS ON INFORMATION THEORY 1998年第5期44卷 1756-1769页

作者： Arikan, E Merhav, N Bilkent Univ Dept Elect & Elect Engn TR-06533 Ankara Turkey Hewlett Packard Labs Palo Alto CA USA

We extend our earlier work on guessing subject to distortion to the joint source-channel coding contest. We consider a system in which there is a source connected to a destination via a channel and the goal is to reconstruct the source output at the destination within a prescribed distortion level with respect to (w.r.t) some distortion measure. The decoder is a guessing decoder in the sense that it is allowed to generate successive estimates of the source output until the distortion criterion is met, The problem is to design the encoder and the decoder so as to minimize the average number of estimates until successful reconstruction. We derive estimates on nonnegative moments of the number of guesses, which are asymptotically tight as the length of the source block: goes to infinity. Using the close relationship between guessing and sequential decoding, we give a tight lower bound to the complexity of sequential decoding in joint source-channel coding systems, complementing earlier works by Koshelev and Hellman. Another topic explored here is the probability of error for list decoders with exponential list sizes for joint source-channel coding systems, for which we obtain tight bounds as well. It is noteworthy that optimal performance w.r.t. the performance measures considered here can be achieved in a manner that separates source coding and channel coding.

关键词： guessing joint source-channel coding list decoding rate distortion sequential decoding

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channel optimized matrix quantization (COMQ) of LSP parameters over waveform channels

Channel optimized matrix quantization (COMQ) of LSP paramete...

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IEEE International Conference on Acoustics, Speech, and Signal Processing

作者： Pérez-Córdoba, JL Rubio, A López-Soler, JM Sánchez, VE Univ Granada Fac Ciencias Dept Elect & Tecnol Comp Granada Spain

ISBN: (纸本)0780370414

Combined source and channel coding is a technique to mitigate channel errors without increasing the bit error rate. channel optimized vector quantizer (COVQ) [3] performs these objectives in the context of vector quantization. This paper presents a study of channel optimized matrix quantizer (COMQ) applied to quantize the Line Spectral Pair (LSP) parameters [5] as an extension of COVQ technique. Gaussian and slow-fading Rayleigh channels are considered and GMSK (Gaussian Minimum Shift-Keying) is used as modulation technique. Several channel signal to noise ratio (CSNR) are considered to measure the performance of this system. In addition, for comparison purposes, the performance of other schemes for quantizing the LSP parameters are computed.

关键词： matrix quantization joint source-channel coding COVQ COMQ LSP parameters CELP coders SMQ GSM EFR coder

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Unequally protected multistage vector quantization for time-varying CDMA channels

Unequally protected multistage vector quantization for time-...

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IEEE International Conference on Communications

作者： Gadkari, S Rose, K Conexant Syst Inc Newport Beach CA 92658 USA Univ Calif Santa Barbara Dept Elect & Comp Engn Santa Barbara CA 93106 USA

ISBN: (纸本)0780347889

We present a source-channel coding system for operation over code-division multiple-access channels with time-varying conditions. The proposed system consists of a multistage vector quantizer (MSVQ) in conjunction with unequal protection against channel errors. The receiver estimates the channel conditions and decodes as many stages of the quantizer as can be reliably decoded, The approach to system design and optimization is first derived and evaluated for a system that employs hard decoding of stage indices. The approach is then extended to the more general case of weighted decoding. Simulation results are given for transmission of Gauss-Markov sources over broadcast and slow fading channels. Consistent and substantial improvement is achieved over the standard MSVQ with equal error protection, and the gains, in terms of source signal-to-noise ratio, are in the range of 3-5 dB.

关键词： code-division multiple access joint source-channel coding time-varying channels unequal error protection vector quantization

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Error statistical analysis of H.263 syntactical elements

Error statistical analysis of H.263 syntactical elements

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Conference on Visual Communications and Image Processing 2001

作者： Tavares, J Navarro, A Univ Aveiro Elect & Telecommun Dept Inst Telecommun P-3810193 Aveiro Portugal

ISBN: (纸本)0819439886

The purpose of our work is to report a solution for the problem of the joint source-channel coding (JSCC) of the H.263 bit stream to be transmitted through error prone channels. Our investigations led us to classify the H.263 syntactical elements into several classes of different significance. By identifying the most sensitive elements we developed a data partitioning (DP) technique which exhibits improved error resilience. A good reconstructed video quality is obtained for a constant 64 kbit/s transmission rate using Rate Compatible Punctured Convolutional (RCPC) codes of different rates for forward error protection. By exploiting the different syntactical element sensitivities we presented an Unequal Error Protection (UEP) scheme that surpasses the optimal Equal Error Protection (EEP). The forward error correction adopted has resulted in PSNR improvements over 20 dB for bit error rates higher than of 4x10(-3).

关键词： H.263 video coding forward error protection joint source-channel coding data partitioning

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