In this paper, we introduce a novel criterion to rank puncturing patterns for rate-compatible LDPC codes. Specifically, based on Gaussian approximation density evolution, a cost function is devised to characterize the...
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ISBN:
(纸本)9781424441471
In this paper, we introduce a novel criterion to rank puncturing patterns for rate-compatible LDPC codes. Specifically, based on Gaussian approximation density evolution, a cost function is devised to characterize the degree distribution of the punctured code matrices, which are derived from a mother code matrix by matrix transformation. This cost function allows us to effectively compare the expected performance of candidate puncturing patterns and to sort out good ones. Combined with well-designed search algorithms, the proposed criterion can be applied on both standardized Block-LDPC codes and generic binary LDPC codes to get good puncturing patterns with manageable complexity. Numerical simulation results verify the effectiveness of the proposed ranking criterion, and demonstrate that a series of good rate-compatible LDPC codes can be obtained by the proposed ranking criterion.
Bit-interleaved coded-modulation (BICM) with iterative demodulation and decoding (IDD) is a popular architecture for the development of practical communication schemes that operate at rates close to capacity. In multi...
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ISBN:
(纸本)1424407281
Bit-interleaved coded-modulation (BICM) with iterative demodulation and decoding (IDD) is a popular architecture for the development of practical communication schemes that operate at rates close to capacity. In multiple-input multiple-output (MIMO) BICM-IDD schemes, a key computational bottleneck is the demodulation step;that is, the extraction of "soft" information about the transmitted bits from the channel output. The concept of list-based demodulation provides a convenient framework for managing the trade-off between accuracy and computational cost in the extraction of this soft information, especially when tree-search techniques are used to construct the list. In this paper, we will propose several list-based demodulators based on modifications of the stack algorithm for searching a tree. The modifications partition the stack in ways that enable efficient and effective searching of the tree from the perspective of list-based demodulation. Simulation results show that the proposed demodulators achieve desirable trade-offs between complexity and performance.
In this paper, a computationally efficient stack-based iterative detection algorithm is proposed for V-BLAST systems. To minimize the receiver's efforts as much as possible, the proposed scheme employs iterative t...
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In this paper, a computationally efficient stack-based iterative detection algorithm is proposed for V-BLAST systems. To minimize the receiver's efforts as much as possible, the proposed scheme employs iterative tree search for complexity reduction and storage saving. After an M-ary tree structure by QR decomposition of channel matrix is constructed, the full tree depth is divided into the first depth and the remaining ones. At tree depth of one, the proposed algorithm finds M candidate symbols. Based on these symbols, it iteratively searches the remaining symbols at second-to-last depth, until finding an optimal symbol sequence. Simulation results demonstrate that the proposed algorithm yields the performance close to that of sphere detection (SD) with significant saving in complexity and storage.
The Vertical Bell Labs Layered Space-Time (V-BLAST) architecture is considered as an efficient technology for achieving high spectral efficiency in a rich-scattering environment. In this paper, we propose a computatio...
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ISBN:
(纸本)9781424406173
The Vertical Bell Labs Layered Space-Time (V-BLAST) architecture is considered as an efficient technology for achieving high spectral efficiency in a rich-scattering environment. In this paper, we propose a computationally efficient nearoptimal detection algorithm for V-BLAST systems. The proposed scheme employs QR decomposition (QRD) of the channel matrix and stack-based limited tree searching method. To reduce computational complexity, especially in low SNRs, the number of branches required for the extension of the tree structure is conditionally chosen according to the channel condition and SNR. The new algorithm requires a fraction of an effort to achieve a near-optimal performance in comparison with other near-optimal detection schemes.
Beginning with an observed document image and a model of how the image has been degraded, Document Image Decoding recognizes printed text by attempting to find a most probable path through a hypothesized Markov source...
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ISBN:
(纸本)0819439851
Beginning with an observed document image and a model of how the image has been degraded, Document Image Decoding recognizes printed text by attempting to find a most probable path through a hypothesized Markov source. The incorporation of linguistic constraints, which are expressed by a sequential predictive probabilistic language model, can improve recognition accuracy significantly in the case of moderately to severely corrupted documents. Two methods of incorporating linguistic constraints in the best-path search are described analyzed and compared. The first, called the iterated complete path algorithm, involves iteratively rescoring complete paths using conditional language model probability distributions of increasing order, expanding state only as necessary with each iteration. A property of this approach is that it results in a solution that is exactly optimal with respect to the specified source, degradation, and language models;no approximation is necessary. The second approach considered is the stack algorithm, which is often used in speech recognition and in the decoding of convolutional codes. Experimental results are presented in which text line images that have been corrupted in a known way are recognized using both the ICP and stack algorithms. This controlled experimental setting preserves many of the essential features and challenges of real text line decoding, while highlighting the important algorithmic issues.
Bidirectional sequential decoding (BSD) substantially reduces the computational variability of conventional sequential decoding without compromising the error performance. However. BSD does not completely eliminate th...
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Bidirectional sequential decoding (BSD) substantially reduces the computational variability of conventional sequential decoding without compromising the error performance. However. BSD does not completely eliminate the erasure problem, We propose in this paper an erasure-free decoding algorithm which combines the idea of BSD in conjunction with that of the multiple stack algorithm (MSA). It is found that the nerv bidirectional multiple stack algorithm (BMSA) offers substantial advantages over the MSA in terms of computational effort, memory requirements, and error performance. The BMSA appears as an attractive alternative to the Viterbi algorithm (VA) where low error probabilities and high decoding speeds are required.
This letter presents techniques for improving the distribution of the number of stack entries, for stack sequential decoding over hard quantized channel, with emphasis on high rate codes. It is shown that, for a class...
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This letter presents techniques for improving the distribution of the number of stack entries, for stack sequential decoding over hard quantized channel, with emphasis on high rate codes. It is shown that, for a class of high rate b/(b + 1) codes, a table-based true high rate approach can be easily implemented for obtaining decoding advantage over the punctured approach. Modified algorithms, which significantly improve the distribution of the number of stack entries and decoding time, are proposed for rate 1/N codes and high rate b/(b + 1) codes.
An algorithm is proposed for universal decoding of convolutional/trellis codes employed over unknown channels. On discrete memoryless channels and at rates below the channel's computational cutoff rate (for a unif...
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An algorithm is proposed for universal decoding of convolutional/trellis codes employed over unknown channels. On discrete memoryless channels and at rates below the channel's computational cutoff rate (for a uniform input distribution), the algorithm achieves an asymptotic complexity-performance tradeoff similar to the tradeoff achieved by the Viterbi algorithm, but with the benefit that the algorithm's implementation does not require knowledge of the channel law. The algorithm is also applicable to channels with memory, and in particular to intersymbol interference (ISI) channels, to channels with nonlinear ISI, and even to general finite-state channels.
This paper presents a method of employing a priority scheme in a random access environment. A prioritized nonblocked stack collision resolution algorithm with binary feedback is developed and tested using simulations....
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This paper presents a method of employing a priority scheme in a random access environment. A prioritized nonblocked stack collision resolution algorithm with binary feedback is developed and tested using simulations. The algorithm accommodates an n-level priority scheme which makes it attractive in mobile data systems. The effectiveness of the algorithm is described on its ability to first, reject the lowest priority class when the system load is near or on the maximum value and second, minimize the delay spread of the higher class users. The performance of the algorithm is characterized using the through-put/delay and cumulative delay for each class of users.
The decoding of long memory high-rate punctured convolutional codes by sequential decoding algorithms is investigated. Both the stack and the Fano algorithms have been thoroughly tested through computer simulation wit...
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The decoding of long memory high-rate punctured convolutional codes by sequential decoding algorithms is investigated. Both the stack and the Fano algorithms have been thoroughly tested through computer simulation with coding rates ranging from R = 2/3 to R = 7/8. Error and overflow probabilities and variability of decoding effort are similar for both algorithms. With hard quantization, plateaus appear in the cumulatives of decoding effort for both algorithms. Comparing the punctured approach of decoding to the more traditional technique for high-rate codes, it is found that punctured decoders perform a larger number of simpler computations, so that the overall decoding effort is on the average more important for the usual decoder than it is for its punctured counterpart. Finally, computational variability, error and overflow probabilities are no worse for punctured decoders than they are for normal decoders.
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