The use of the variable-length coding in the final stage of image compression using JPEG makes the image more sensitive to channel errors and can have severe effects on the viewed image. This is due to loss of synchro...
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The use of the variable-length coding in the final stage of image compression using JPEG makes the image more sensitive to channel errors and can have severe effects on the viewed image. This is due to loss of synchronization in the decoder. Even one bit error can propagate significantly throughout the image. In the past, some techniques have been proposed for resynchronizing Huffman decoders using special synchronizing codewords. The JPEG standard itself allows the use of a special restart marker to help decoder resynchronization. It does not, however, give any guidelines for error recovery. We first describe the most probable types of errors that occur in a JPEG data stream. We focus on techniques and algorithms for detecting the occurrence of a particular error and then for locating that error. One technique functions at the entropy encoding level by taking advantage of the specific data structure of the JPEG stream and using alternately two different end-of-block characters. Others function at the DCT coefficient level or at the pixel level, detecting unlikely patterns that are produced due to errors. We compare different methods and finally propose the most effective method for errordetection and image correction.< >
Erasure-and-error decoding is a general form of channel decoding and is a basis of important coding schemes, such as the concatenated coding scheme and coded ARQ. However, there do not exist enough discussions on the ...
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Erasure-and-error decoding is a general form of channel decoding and is a basis of important coding schemes, such as the concatenated coding scheme and coded ARQ. However, there do not exist enough discussions on the interrelationship between erasure-and-error decoding schemes. In this paper, threshold decoding schemes are discussed in a systematic manner and compared with Forney's optimal scheme. Some confusions in known results are pointed out and new results on threshold decoding are shown.
The authors discuss combined channel coding and error concealment schemes for digital audio broadcasting (DAB). Comparison of two coding schemes showed that the robustness against hostile reception conditions of a dig...
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The authors discuss combined channel coding and error concealment schemes for digital audio broadcasting (DAB). Comparison of two coding schemes showed that the robustness against hostile reception conditions of a digital broadcast transmission can effectively be increased by applying unequal protection (UEP) and a simple concealment of residual bit errors (muting and repetition of some scalefactors).< >
The discrete Fourier transform (DFT) is used for errordetection and correction. An iterative decoder is proposed for erasure and impulsive noise which also works with moderate amount of additive random noise. The ite...
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The discrete Fourier transform (DFT) is used for errordetection and correction. An iterative decoder is proposed for erasure and impulsive noise which also works with moderate amount of additive random noise. The iterative method is very simple and efficient consisting of modules of fast Fourier transforms (FFT) and inverse FFTs. This iterative decoder can be implemented in a feedback configuration. The authors are working on a DSP implementation of this technique.< >
A 140 Mbit/s optical line system is proposed which will not only satisfy the emerging tie line requirement but which will also be capable of adaptation for long haul systems to allow replacement of the older equipment...
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A 140 Mbit/s optical line system is proposed which will not only satisfy the emerging tie line requirement but which will also be capable of adaptation for long haul systems to allow replacement of the older equipment. Results from prototype testing have shown that all of the design parameters for both the line code and the remainder of the system have been achieved with adequate margins.< >
Codes based on runlength-limited sequences are the state of the art corner stone of current disk recorders, whether their nature is magnetic or optical. The error detecting or correcting capabilities of runlength limi...
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Codes based on runlength-limited sequences are the state of the art corner stone of current disk recorders, whether their nature is magnetic or optical. The error detecting or correcting capabilities of runlength limited sequences are quite poor. In this paper, the author presents an algebraic approach for constructing runlength-limited block codes of fixed codeword length that impart some error detecting capabilities.< >
An approach to fault-tolerant computing in general and digital signal processing in particular is that of arithmetic error-detecting/correcting codes. These codes were designed to commute with the addition operator an...
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An approach to fault-tolerant computing in general and digital signal processing in particular is that of arithmetic error-detecting/correcting codes. These codes were designed to commute with the addition operator and the theory is extensive. In digital signal processing applications the bulk of the arithmetic is addition and multiplication, it is therefore interesting to look for codes that commute with both addition and multiplication. It is shown that such a code does in fact exist; an AN code where the code generator A is an idempotent i.e. A/sup 2/=A. This code, unfortunately, has a serious deficiency in that errors can be masked by a fault-free multiplier. Thus no single (non-separate) code is suitable for both addition and multiplication. Motivated by this problem and the fact that AN codes were designed around the addition operator, the characteristics of a code that commutes with multiplication are discussed. A simple code that satisfies these requirements is presented: an AN+B code. The results of some computer simulations of an AN+B coded multiplier are given.< >
An algorithm for switching communications between a mobile station and two adjacent base stations is investigated. The hand-off algorithm is based on the symbol error rate measured by a Reed-Solomon (RS) coder. Simula...
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An algorithm for switching communications between a mobile station and two adjacent base stations is investigated. The hand-off algorithm is based on the symbol error rate measured by a Reed-Solomon (RS) coder. Simulations based on SBC speech, RS coding, MSK modulation, and the Hata propagation path loss model, show how hand-off can be used as a form of diversity reception with the effective BER varying as a function of the number of hand-offs.< >
Presents the principal requirements from a modern adaptive HF communication system, the basic design concepts of the implemented system which successfully answers these requirements, the accompanying field trial metho...
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Presents the principal requirements from a modern adaptive HF communication system, the basic design concepts of the implemented system which successfully answers these requirements, the accompanying field trial methodology and briefly, some of the field trials results. The basic lesson learned from the implementation and the field trials of the described system is that a modern HF communication system can fulfil the current and future requirements of C3I systems only if it glues together a number of technical features including self-healing architecture, automatic digital operation, real time, adaptive frequency management, HF oriented errordetection and correction codes and communication protocols. ALE, LQA and simple and efficient man-machine interfaces. A mandatory phase is developing such systems is the field trials which should be performed with computer aid, using appropriate methodology and tools.< >
The paper seeks to justify the contention that the efficiency of error-detection-coding techniques is frequently overestimated owing to insufficient appreciation of the interaction between the characteristics of the c...
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The paper seeks to justify the contention that the efficiency of error-detection-coding techniques is frequently overestimated owing to insufficient appreciation of the interaction between the characteristics of the code and those of the signalling channel itself. The redundancy of an error-detection code (e.d.c.) requires an increase in modulation rate, and this causes an increase in element error rate due to reduction in normalised signal/noise ratio. On h.f. radio circuits, ionospheric effects can cause even greater increases, and current interleaving and convolution techniques only recoup a small proportion of the disadvantage. It is shown that, in many cases, these factors can outweigh the correcting capabilities of current codes. Comparison of various binary codes and the Piccolo m.f.s.k. system suggests that, where circumstances are such that extremely low error rates are not essential, a nonredundant unprotected code may be comparable in availability with an e.d.c., and Piccolo would probably be an improvement.
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