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On reduced-complexity equalization based on Ungerboeck and Forney observation models

IEEE TRANSACTIONS ON SIGNAL PROCESSING 2008年第8期56卷 3784-3789页

作者： Loncar, maja Rusek, Fredrik Lund Univ Elect & Informat Technol Dept SE-22100 Lund Sweden

This correspondence investigates the asymptotic behavior of reduced-state intersymbol interference (ISI) equalizers, based on the Ungerboeck and Forney observation models. It is shown that Ungerboeck-based equalizers can suffer from correct-path-loss (CPL) even in the noiseless regime. ISI conditions that lead to CPL are analytically derived and illustrated by examples.

关键词： equalization Forney model intersymbol interference (ISI) ISI models m-algorithm Ungerboeck model

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Adaptive multiple-symbol differential detection of mAPSK over frequency selective fading channels

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IEICE TRANSACTIONS ON FUNDAmENTALS OF ELECTRONICS COmmUNICATIONS AND COmPUTER SCIENCES 2000年第6期E83A卷 1175-1183页

作者： Liu, mY Handa, S machida, m Oshita, S Shinshu Univ Fac Engn Nagano 3808553 Japan

We propose a novel adaptive multiple-symbol differential detection (mSDD) scheme that has excellent performance over frequency selective fading (FSF) channels. The adaptive mSDD scheme consists of an adaptive noncoherent least mean square channel estimator that can accomplish channel estimation without any decision delay and the mSDD. The m-algorithm is introduced into this detection scheme to reduce the complication of computation due to increasing observed sequence length in the mSDD. Because of the application of the adaptive channel estimator and the m-algorithm, this adaptive mSDD make it possible that channel estimation is accomplished for every symbol along m surviving paths without any decision delay. And the SER performance of this adaptive mSDD is not affected by phase fluctuation introduced by a channel because the mSDD and the noncoherent channel estimator are applied. The adaptive mSDD scheme is applied to typical constellation of 16APSK, the (4,12) QAm and the star QAm. The excellent tracking per performance of this adaptive mSDD scheme over FSF channels is confirmed by computer simulations.

关键词： multiple-symbol differential detection frequency selective fading channel estimator m-algorithm m-ary modulation

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Efficient Soft-Input Soft-Output Tree Detection via an Improved Path metric

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IEEE TRANSACTIONS ON INFORmATION THEORY 2012年第3期58卷 1518-1533页

作者： Choi, Jun Won Shim, Byonghyo Singer, Andrew C. Qualcomm Inc San Diego CA 92121 USA Univ Illinois Dept Elect & Comp Engn Urbana IL 61801 USA Korea Univ Sch Informat & Commun Seoul South Korea

Tree detection techniques are often used to reduce the complexity of a posteriori probability (APP) detection in multiantenna wireless communication systems. In this paper, we introduce an efficient soft-input soft-output tree detection algorithm that employs a new type of look-ahead path metric in the process of branch pruning (or sorting). While conventional path metrics depend only on symbols on a visited path, the new path metric accounts for unvisited parts of the tree in advance through an unconstrained linear estimator and adds a bias term that reflects the contribution of as-yet undecided symbols. By applying the linear estimate-based look-ahead path metric to an m-algorithm that selects the best m paths for each level of the tree, we develop a new soft-input soft-output tree detector, called an improved soft-input soft-output m-algorithm (ISS-mA). Based on an analysis of the probability of correct path loss, we show that the improved path metric offers substantial performance gain over the conventional path metric. We also demonstrate through simulations that the proposed ISS-mA can be a promising candidate for soft-input soft-output detection in high-dimensional systems.

关键词： Iterative detection and decoding (IDD) k-best search list sphere decoding look-ahead path metric m-algorithm soft-input soft-output detection tree detection turbo principle

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PESA: a predictive energy-saving approach based on an OSHmm

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IET COmmUNICATIONS 2018年第14期12卷 1751-1758页

作者： Lin, Qin-Liang Yu, Shun-Zheng Sun Yat Sen Univ Sch Informat Sci & Technol Guangzhou 510006 Guangdong Peoples R China

Reducing energy consumption of the internet becomes more and more important. The authors propose a novel approach, called predictive energy-saving approach (PESA), to put near-idle nodes of a network into sleep mode to save energy. In PESA, they propose an online spatial hidden markov model (OSHmm) to describe the distribution of the network traffic and predict the lowest-loaded nodes. Those nodes will be put into sleep mode under the constraints that the network's full connectivity is kept and no new congested nodes are generated. To reduce the computation, they leverage on an online training technique and m-algorithm in OSHmm. They evaluate the approach over a randomly generated topology and a real ISP backbone topology with a real traffic dataset. The results show that the proposed approach is energy efficient with low computation complexity.

关键词： energy consumption energy conservation telecommunication power management Internet hidden markov models telecommunication network topology telecommunication traffic PESA predictive energy-saving approach OSHmm online spatial hidden markov model energy consumption reduction Internet sleep mode energy saving network traffic distribution lowest-loaded node prediction online training technique m-algorithm randomly generated topology real ISP backbone topology real traffic dataset low computation complexity

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Achieving single-user performance in an FEC-Coded DS-CDmA system for frequency selective and flat fading channels

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IEEE JOURNAL ON SELECTED AREAS IN COmmUNICATIONS 2008年第3期26卷 446-458页

作者： Wong, Kitty K. Y. mcLane, Peter J. Queens Univ Dept Elect & Comp Engn Kingston ON K7L 3N6 Canada

This paper presents a reduced-complexity soft-input soft-output trellis/tree multiuser equalizer for an iterative DS-CDmA system undergoing Rayleigh frequency selective fading. The algorithm first expands the equalizer-trellis to an equivalent trellis/tree structure. Then it applies the m-algorithm to the equivalent structure twice, once to reduce the number of states in the trellis and the other to reduce the number of branches emanating from each state. To compute soft-information, the algorithm utilizes not only those fully-extended paths reaching the end of the trellis but also paths that are traversed and discarded in the pruned trellis. Through a simple update-and-discard procedure, reliable soft-information is extracted from discarded paths which enables an extremely large trellis to be successfully decoded with modest complexity. BER performance is presented for a convolutional-coded DS-CDmA system employing random spreading sequences. Our results demonstrate that the proposed algorithm is capable of achieving single-user performance with a much reduced complexity. The proposed algorithm can also be applied to reduce the complexity of multiuser detection where the transmission channel is frequency flat. Single-user performance can also be achieved with the proposed technique.

关键词： equalization iterative decoding m-algorithm multiuser detection sequential decoding

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Reduced-complexity equalization techniques for ISI and mImO wireless channels in iterative decoding

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IEEE JOURNAL ON SELECTED AREAS IN COmmUNICATIONS 2008年第2期26卷 256-268页

作者： Wong, Kitty K. Y. mcLane, Peter J. Queens Univ Dept Elect & Comp Engn Kingston ON K7L 3N6 Canada

Two reduced-complexity soft-input soft-output trellis decoding techniques are presented in this paper for equalizing single-input single-output InterSymbol Interference (ISI) channels and multiple-Input multiple-Output (mImO) frequency selective fading channels. Given a trellis representing an ISI channel, the Soft-Output m-algorithm (SOmA) reduces the complexity of equalization by retaining only the best m survivors at each trellis interval. The remaining survivors are discarded. The novelty of the SOmA is the use of discarded paths to obtain soft-information. Through a simple update-and-discard procedure, the SOmA extracts reliable soft-information from discarded paths which enables a large trellis to be successfully decoded with a relatively small value of m. To decode a trellis representing a mImO frequency selective fading channel, two challenges are faced. Not only that the trellis has a large number of states, the number of branches per trellis interval is also enormous. The Soft-Output Trellis/Tree m-algorithm (SOTTmA) expands each trellis interval into a tree-like structure and performs the m-algorithm twice: once at each trellis interval to reduce the number of states and the other at each tree sub-level to remove unwanted branches. With the proposed technique, high-order trellises with million of branches per interval can be decoded with modest complexity.

关键词： equalization Intersymbol Interference m-algorithm multiple-Input multiple-Output sequential decoding soft-information turbo-detection

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Recursive QR packet combining for uplink single-carrier multi-user mImO HARQ using near mL detection

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WIRELESS COmmUNICATIONS & mOBILE COmPUTING 2012年第18期12卷 1652-1663页

作者： Yamamoto, Tetsuya Adachi, Koichi Sun, Sumei Adachi, Fumiyuki Tohoku Univ Grad Sch Engn Dept Commun Engn Aoba Ku 6-6-05 Aza Aoba Sendai Miyagi 9808579 Japan ASTAR Inst Infocomm Res Singapore 138632 Singapore

QR decomposition-based near maximum likelihood block detection significantly improves the transmission performance of uplink single-carrier (SC) multi-user multiple-input multiple-output (mU-mImO). Hybrid automatic repeat request (HARQ) is an indispensable error control technique for high-quality packet data transmission. The achievable diversity gain of HARQ depends on the packet combining strategy. In uplink mU-mImO HARQ, the received signal may consist of new packets and retransmitted packets as retransmission for each user acts independently. In this paper, a recursive QR packet combining scheme suitable for uplink SC mU-mImO HARQ is proposed, which takes into account the number of retransmissions for each user in the detection order. The computational complexity and required storage size can be significantly reduced by the proposed scheme. moreover, it improves the packet error rate performance and throughput performance significantly over the conventional bit-level log likelihood ratio packet combining, as shown by our computer simulation results. Copyright (C) 2012 John Wiley & Sons, Ltd.

关键词： single-carrier mU-mImO HARQ packet combining QR decomposition m-algorithm

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High-performance, low-cost joint equalizer and trellis decoder for 1000BASE-T gigabit Ethernet transceiver

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The Journal of China Universities of Posts and Telecommunications 2007年第2期14卷 106-111页

作者： ZHU Yue RONG meng-tian Department of Electronic Engineering School of Electronic Information and Electrical Engineering Shanghai Jiao Tong University Shanghai 200240 China

This article presents an m-algorithm （mA） decoder with 4 survival paths （mA4） for Institute of Electrical and Electronics Engineers （IEEE） 802.3ab 1000BASE-T gigabit Ethernet （GbE） transceiver. To fulfill the entire requirements, various methods were introduced to accelerate the mA4 decoder while retaining the desired high performance and low complexity. Optimized look-ahead architecture was employed to solve the critical path problem with minimal gate consumption. Symbol compression methods saved registers during pipeline stages. A sorting network accelerated the kernel sorting operation at low hardware cost by utilizing the special characteristics of mA4. Simulations and synthesis results show that the proposed decoder achieves 125 mHz clock frequency and l Gb/s throughput in 1.8 V 0.18μm standard cell complementary metal-oxide-semiconductor （CmOS） process. It achieves additional 0.4 dB coding gain over 14tap parallel decision feedback decoder （PDFD） with 39% area reduction.

关键词： 1000BASE-T GbE m-algorithm PDFD look-ahead technology

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A Large-Scale Hidden Semi-markov model for Anomaly Detection on User Browsing Behaviors

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IEEE-ACm TRANSACTIONS ON NETWORKING 2009年第1期17卷 54-65页

作者： Xie, Yi Yu, Shun-Zheng Sun Yat Sen Univ Dept Elect & Commun Engn Guangzhou 510275 Guangdong Peoples R China

many methods designed to create defenses against distributed denial of service (DDoS) attacks are focused on the IP and TCP layers instead of the high layer. They are not suitable for handling the new type of attack which is based on the application layer. In this paper, we introduce a new scheme to achieve early attack detection and filtering for the application-layer-based DDoS attack. An extended hidden semi-markov model is proposed to describe the browsing behaviors of web surfers. In order to reduce the computational amount introduced by the model's large state space, a novel forward algorithm is derived for the online implementation of the model based on the m-algorithm. Entropy of the user's HTTP request sequence fitting to the model is used as a criterion to measure the user's normality. Finally, experiments are conducted to validate our model and algorithm.

关键词： Anomaly detection browsing behaviors DDoS hidden semi-markov model m-algorithm

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All pairs shortest paths for graphs with small integer length edges

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JOURNAL OF COmPUTER AND SYSTEm SCIENCES 1997年第2期54卷 243-254页

作者： Galil, Z margalit, O COLUMBIA UNIV NEW YORKNY 10027

The authors have solved the all pairs shortest distances (APSD) problem for graphs with integer edge lengths. Our algorithm is subcubic for edge lengths of small (less than or equal to m) absolute value. In this paper we show how to transform these algorithms to solve the all pairs shortest paths (APSP), in the same time complexity, up to a polylogarithmic factor. For n = \V\ the number of vertices, m the bound on edge length, and omega the exponent of matrix multiplication, we get the following results: 1. A directed nonnegative APSP(n, m) algorithm which runs in (O) over tilde(T(n, m)) time, where [GRAPHICS] 2. An undirected APSP(n, m) algorithm which runs in (O) over tilde(m((omega+1)/2)n(omega) log(mn)) time. 3. A general APSP(n, m) algorithm which runs in (O) over tilde((mn)((3+omega)/2)).

关键词： oxygen Precursor Cell Lymphoblastic Leukemia-Lymphoma shortest path complexity classes Byways m-algorithm matrix multiplication Less than or equal to

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