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IEEE Military Communications Conference (MILCOM 2006)

作者： Lee, Namjeong Lee, Keonkook Cha, Jongsub Kang, Joonhyuk Gil, Gyetae School of Engineering Information and Communications University South Korea Professional Research Group Advanced Technology Laboratory KT South Korea

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.

关键词： Multiple-Input Multiple-Output (MIMO) V-BLAST QR decomposition stack algorithm

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Reduced-complexity demodulation for MIMO-BICM-IDD using modified stack algorithms

Reduced-complexity demodulation for MIMO-BICM-IDD using modi...

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32nd IEEE International Conference on Acoustics, Speech and Signal Processing

作者： Nekuii, Mehran Davidson, Timothy N. McMaster Univ Dept Elect & Comp Engn Hamilton ON Canada

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.

关键词： MIMO demodulation iterative demodulation and decoding stack algorithm

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A Transformation Method between PLC Ladder Diagrams and Instruction Lists Using Recursive and stack algorithms

A Transformation Method between PLC Ladder Diagrams and Inst...

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2nd International Conference on Mechatronics and Intelligent Materials (MIM 2012)

作者： Zhang, Zhisheng Li, Cheng Zhou, Yifan Liu, Wendong Southeast Univ Sch Mech Engn Nanjing 211189 Jiangsu Peoples R China Jiangsu Changjiang Elect Technol Co Ltd Wuxi 214431 Peoples R China

ISBN: (纸本)9783037853849

The method of transforming a ladder diagram (LD) and an instruction list (IL) of PLC (Programmable Logic Controller) to each other is investigated in this paper. Firstly, ladder-step is adopted on transforming LD into IL. Ladder-step is divided series or parallel by using recursive algorithm, and then complicated ladder-step can be divided into several simple ladder-steps which can be converted to IL easily. When obtaining simple ladder-steps' IL, combining them together to get final IL program of complicated LD program. Secondly, on transforming IL into LD, stack algorithm contributes a lot. Scanning IL to generate LD of each instruction block, and then pushing them into stack. Combine LDs in the stack by operating instruction, and then IL is transformed into LD successfully. Finally, in the last part of this paper, we show our PLC software and lower position machine. In addition, this transforming algorithm has already applied in PLC software successfully.

关键词： PLC Ladder Diagram Instruction List Recursive algorithm stack algorithm

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Adding linguistic constraints to document image decoding: Comparing the iterated complete path and stack algorithms

Adding linguistic constraints to document image decoding: Co...

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8th Annual Document Recognition and Retrieval Conference

作者： Popat, K Greene, DH Romberg, JK Bloomberg, DS Xerox Corp Palo Alto Res Ctr Palo Alto CA 94304 USA Rice Univ ECE Dept Houston TX 77251 USA

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.

关键词： Document Image Decoding optical character recognition lexical language modeling hidden Markov models dynamic programming Viterbi algorithm stack algorithm list decoding convolutional decoding

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A Multistack algorithm for Soft MIMO Demodulation

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IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY 2009年第5期58卷 2592-2597页

作者： Nekuii, Mehran Davidson, Timothy N. McMaster Univ Dept Elect & Comp Engn Hamilton ON L8S 4K1 Canada

We propose a family of list-based soft demodulators for multiple-input-multiple-output (MIMO) communication systems based on a multistack algorithm for traversing the tree structure that is inherent in the MIMO demodulation problem. The existing stack algorithm for MIMO soft demodulation stores a single stack of visited nodes in the tree and expands the stack using the "best-first" principle. In the proposed multistack algorithm, the single stack is partitioned into a stack for each level of the tree, and the algorithm proceeds by performing one best-first search step in each of these stacks in the natural ordering of the tree. By assigning appropriate priorities to the level at which this "best-first search per level" processing restarts once a leaf node has been obtained, the proposed demodulators can achieve tradeoffs between performance and complexity that dominate those of several existing methods, including the stack algorithm, in the low-complexity region.

关键词： Iterative demodulation and decoding (IDD) list demodulation sphere decoder stack algorithm tree-search decoding turbo principle

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Reduced-complexity stack-based iterative detection for V-BLAST systems

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IEICE TRANSACTIONS ON COMMUNICATIONS 2007年第10期E90B卷 2897-2902页

作者： Cha, Jongsub Lee, Keonkook Kang, Joonhyuk Informat & Commuun Univ Sch Engn Taejon 305714 South Korea

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.

关键词： MIMO systems V-BLAST maximum-likelihood detection sphere detection stack algorithm

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On low complexity stack decoding of convolutional codes

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IEEE TRANSACTIONS ON COMMUNICATIONS 1999年第5期47卷 648-652页

作者： D'Souza, J Maskara, SL Indian Inst Technol Dept Elect & Elect Commun Engn Kharagpur 721302 W Bengal India

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.

关键词： convolutional codes sequential decoding stack algorithm

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Memory-Constrained Tree Search Detection and New Ordering Schemes

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IEEE JOURNAL OF SELECTED TOPICS IN SIGNAL PROCESSING 2009年第6期3卷 1026-1037页

作者： Dai, Yongmei Yan, Zhiyuan Lehigh Univ Dept Elect & Comp Engn Bethlehem PA 18015 USA

Hardware implementations of tree search-based multiple-input multiple-output (MIMO) detection often have limited performance due to large memory requirement or high computational complexity of sophisticated MIMO detection algorithms. In this paper, we propose new tree search-based detection algorithms that achieve maximum-likelihood (ML) performance under any given memory constraints and with reduced computational complexity. To this end, we make two main contributions. First, we propose a memory-constrained tree search (MCTS) algorithm that bridges the gap between the sphere decoding (SD) and stack algorithms. Our MCTS algorithm dynamically adapts to any pre-specified memory constraint and offers a graceful tradeoff between computational complexity and memory requirement while maintaining the ML performance. When the memory size is set as the minimum, our MCTS algorithm is similar to the SD algorithm. As the memory size increases, the average computational complexity of our MCTS algorithm decreases. When the memory size becomes large, our MCTS algorithm is similar to the stack algorithm, having similar average computational complexity but requiring significantly less memory. To further reduce the computational complexity of tree search-based ML detection algorithms, we propose novel ordering schemes that can be easily embedded in the QR decomposition and take into account both the channel matrix and the received signal (noise);simulation results show that our ordering schemes lead to reduced average computational complexity for the SD and MCTS algorithms, and the reduction is significant at low to medium signal-to-noise ratio region.

关键词： Multiple-input multiple-output (MIMO) detection maximum-likelihood (ML) QR decomposition (QRD) sphere decoding stack algorithm zero-forcing interference cancellation (ZF-IC)

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Optimally Efficient Max-Log APP Demodulation in MIMO Systems

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IEEE JOURNAL OF SELECTED TOPICS IN SIGNAL PROCESSING 2011年第8期5卷 1400-1414页

作者： Prasad, Narayan Kalbat, Khalid Y. Wang, Xiaodong NEC Labs Amer Princeton NJ 08540 USA Columbia Univ Dept Elect Engn New York NY 10027 USA

In this paper, we consider the design of multi-stream demodulators for multiple-input multiple-output (MIMO) systems. Our proposed MIMO demodulator is based on the stack tree-search strategy and provides soft-outputs in the form of exact max-log log-likelihood ratios (max-log LLRs). We prove that our proposed demodulator is optimally efficient in that it visits the least number of nodes among all optimal demodulators in a class of tree-search-based demodulators. We conduct a comprehensive complexity analysis of such optimally efficient demodulators. We also identify key parameters associated with our proposed demodulator that can be controlled to realize near max-log performance with substantially reduced complexity, as demonstrated via simulations.

关键词： Demodulator log-likelihood ratio (LLR) max-log approximation multiple-input multiple-output (MIMO) stack algorithm

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Random access algorithm for users with multiple priorities

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IEICE TRANSACTIONS ON COMMUNICATIONS 1996年第3期E79B卷 237-243页

作者： Buot, T Watanabe, F UNIV ELECTROCOMMUN GRAD SCH INFORMAT SYST CHOFU TOKYO 182 JAPAN

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.

关键词： aloha reservation random access algorithm stack algorithm

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