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IEEE International Conference on Communications (IEEE ICC)

作者： Colavolpe, Giulio Conti, Elisa Piemontese, Amina Vannucci, Armando Univ Parma I-43124 Parma Italy CNIT Res Unit Dept Engn & Architecture I-43124 Parma Italy

ISBN: (纸本)9781538674628

Expectation Propagation (EP) is a promising framework in message-passing algorithms based on factor-graphs. The inherent ability to combine prior (partial) knowledge of system variables with channel observations suggests that an effective estimation of random channel parameters can be achieved even with a very limited number of pilot symbols, thus increasing the payload efficiency. Yet, the way in which the probability distributions of latent variables (both data and parameters) are combined and projected often requires ad-hoc adjustments to reach satisfactory performance. Here, we apply EP to a classical problem of LDPC-coded transmission on a strong Wiener phase noise channel and discuss how and why, even in the simple case of binary modulation, EP can fail or succeed.

关键词： expectation propagation (EP) phase-noise iterative detection/decoding factor graphs (FGs) sum-product algorithm (SPA) low-density parity-check (LDPC)

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SISO detection Over Linear Channels With Linear Complexity in the Number of Interferers

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IEEE JOURNAL OF SELECTED TOPICS IN SIGNAL PROCESSING 2011年第8期5卷 1475-1485页

作者： Colavolpe, Giulio Fertonani, Dario Piemontese, Amina Univ Parma Dipartimento Ingn Informaz I-43124 Parma Italy

We consider detection over linear channels impaired by additive white Gaussian noise. For this general model, which describes a large variety of scenarios, novel detection algorithms are derived by applying the sum-product algorithm to a suitably designed factor graph. Being soft-input soft-output (SISO) in nature, the proposed detectors can be adopted in turbo processing without additional modifications. Among various applications, we focus on channels with known intersymbol interference, on frequency-division-multiplexed systems where adjacent signals are allowed to overlap in frequency to increase the spectral efficiency, and on code division multiple access systems. When compared with the existing interference-cancellation algorithms, the proposed schemes result very appealing in terms of tradeoff between performance and computational complexity. Particularly, the proposed schemes can approach or even outperform the performance provided by much more complex algorithms.

关键词： Code division multiple access (CDMA) frequency-division multiplexing (FDM) iterative detection/decoding intersymbol interference linear channels soft-input soft-output (SISO) detection

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NOVEL decoding OF SQUARE QAM MODULATED MIMO SYSTEMS BASED ON TURBO MULTIUSER detection

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Journal of Electronics(China) 2008年第2期25卷 174-178页

作者： Zheng Jianping Bai Baoming Wang Xinmei State Key Lab of Integrated Services Networks Xidian Univ. Xi＇an 710071 China

By introducing the bit-level multi-stream coded Layered Space-Time （LST） transmitter along with a novel iterative MultiStage decoding （MSD） at the receiver, the paper shows how to achieve the near-capacity performance of the Multiple-Input Multiple-Output （MIMO） systems with square Quadrature Amplitude Modulation （QAM）. In the proposed iterative MSD scheme, the detection at each stage is equivalent to multiuser detection of synchronous Code Division Multiple Access （CDMA） multiuser systems with the aid of the binary representation of the transmitted symbols. Therefore, the optimal Soft-Input Soft-Output （SISO） multiuser detection and low-complexity SISO multiuser detection can be utilized herein. And the proposed scheme with low-complexity SISO multiuser detection has polynomial complexity in the number of transmit antennas M, the number of receive antennas N, and the number of bits per constellation point Me. Simulation results demonstrate that the proposed scheme has similar Bit Error Rate （BER） performance to that of the known iterative Tree Search （ITS） detection.

关键词： Multiple-Input Multiple-Output （MIMO） MultiStage decoding （MSD） iterative detection/decoding Multiuser detection Polynomial complexity

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iterative detection for channels with memory

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PROCEEDINGS OF THE IEEE 2007年第6期95卷 1272-1294页

作者： Anastasopoulos, Achilleas Chugg, M. Colavolpe, Giulio Ferrari, Gianluigi Raheli, Riccardo Univ Michigan Dept Elect Engn & Comp Sci Ann Arbor MI 48109 USA Univ So Calif Inst Commun Sci Elect Engn Dept Syst Div Los Angeles CA 90089 USA

In this paper, we present an overview on the design of algorithms for iterative detection over channels with memory. The starting point for all the algorithms is the implementation of soft-input soft-ouput maximum a posteriori (MAP) symbol detection strategies for transmissions over channels encompassing unknown parameters, either stochastic or deterministic. The proposed solutions represent effective ways to reach this goal. The described algorithms are grouped into three categories: i) we first introduce algorithms for adaptive iterative detection, where the unknown channel parameters are explicitly estimated;ii) then, we consider finite-memory iterative detection algorithms, based on ad hoc truncation of the channel memory and often interpretable as based on an implicit estimation of the channel parameters;and iii) finally, we present a general detection-theoretic approach to derive optimal detection algorithms with polynomial complexity. A few illustrative numerical results are also presented.

关键词： adaptive iterative detection channels with memory finite-memory detection iterative detection/decoding message passing detection algorithms polynomial complexity detection trellis-based detection

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Reduced-complexity time-domain equalization for Turbo-MIMO systems

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IEEE TRANSACTIONS ON COMMUNICATIONS 2007年第10期55卷 1878-1883页

作者： de Jong, Yvo L. C. Willink, Tricia J. Commun Res Ctr Ottawa ON K2H 8S2 Canada

A reduced-complexity time-domain equalization scheme for wideband turbo-multiple-input multiple-output (turbo-MIMO) systems is presented. This scheme, called iterative trellis search equalization, is based on a modified version of the M-Bahl-Cocke-jelinek-Raviv (M-BCJR) algorithm, applied to a suitably chosen trellis representation of the wideband MIMO channel process. Exploiting the properties of quadrature amplitude modulation (QAM) signal constellations with block-partitionable labels, this modified M-BCJR algorithm has complexity per bit that is independent of the constellation size, and polynomial in the number of transmit antennas and channel memory. Results from computer simulations show that the new scheme successfully mitigates intersymbol interference even if only a very small fraction of trellis state transitions is considered. It is also demonstrated that asynchronous transmission of the spatially multiplexed symbol streams can result in considerable performance improvement compared to synchronous MIMO systems.

关键词： complexity reduction iterative detection/decoding multiple-input multiple-output (MIMO) systems trellis searching

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On LDPC codes over channels with memory

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IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS 2006年第7期5卷 1757-1766页

作者： Colavolpe, Giulio Univ Parma Dipartimento Ingn Informaz I-43100 Parma Italy

The problem of detection and decoding of low-density parity-check (LDPC) codes transmitted over channels with memory is addressed. A new general method to build a factor graph which takes into account both the code constraints and the channel behavior is proposed and the a posteriori probabilities of the information symbols, necessary to implement maximum a posteriori (MAP) symbol detection, are derived by using the sum-product algorithm. With respect to the case of a LDPC code transmitted on a memoryless channel, the derived factor graphs have additional factor nodes taking into account the channel behavior and not the code constraints. It is shown that the function associated to the generic factor node modeling the channel is related to the basic branch metric used in the Viterbi algorithm when MAP sequence detection is applied or in the BCJR algorithm implementing MAP symbol detection. This fact suggests that all the previously proposed solutions for those algorithms can be systematically extended to LDPC codes and graph-based detection. When the sum-product algorithm works on the derived factor graphs, the most demanding computation is in general that performed at factor nodes modeling the channel. In fact, the complexity of the computation at these factor nodes is in general exponential in a suitably defined channel memory parameter. In these cases, a technique for complexity reduction is illustrated. In some particular cases of practical relevance, the above mentioned complexity becomes linear in the channel memory. This;does not happen in the same cases when detection is performed by using the Viterbi algorithm or the BCJR algorithm, suggesting that the use of factor graphs and the sum-product algorithm might be computationally more appealing. As an example of application of the described framework, the cases of noncoherent and flat fading channels are considered.

关键词： factor graphs surn-product algorithm channels with memory phase-noise flat fading low-density parity-check codes iterative detection/decoding

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iterative tree search detection for MIMO wireless systems

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IEEE TRANSACTIONS ON COMMUNICATIONS 2005年第6期53卷 930-935页

作者： de Jong, YLC Willink, TJ Commun Res Ctr Ottawa ON K2H 8S2 Canada

This paper presents a reduced-complexity soft-input soft-output detection scheme, called iterative tree search detection, for multiple-input multiple-output wireless communication systems employing turbo processing at the receiver. In this scheme, a reduced search space is selected with the aid of the M-algorithm, and QAM signal constellations with block partitionable labels are used in order to make the detection complexity per bit almost independent of the modulation order, as well as asymptotically linear in the number of transmit antennas. Results from computer simulations are presented which demonstrate the capability of the scheme to approach optimal performance at considerably reduced complexity.

关键词： complexity reduction iterative detection/decoding multiple-input multiple-output (MIMO) systems tree searching

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Algorithms for iterative decoding in the presence of strong phase noise

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IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS 2005年第9期23卷 1748-1757页

作者： Colavolpe, G Barbieri, A Caire, G Univ Parma Dipartimento Ingn Informat I-43100 Parma Italy Inst Eurecom Mobile Commun Grp F-6560 Valbonne France

We present two new iterative decoding algorithms for channels affected by strong phase noise and compare them with the best existing algorithms proposed in the literature. The proposed algorithms are obtained as an application of the sum-product algorithm to the factor graph representing the joint a posteriori probability mass function of the information bits given the channel output. In order to overcome the problems due to the presence in the factor graph of continuous random variables, we apply the method of canonical distributions. Several choices of canonical distributions have been considered in the literature. Well-known approaches consist of discretizing continuous variables or treating them as jointly Gaussian, thus obtaining a Kalman estimator. Our first new approach, based on the Fourier series expansion of the phase probability density function, yields better complexity/performance tradeoff with respect to the usual discretized-phase method. Our second new approach, based on the Tikhonov canonical distribution, yields near-optimal performance at very low complexity and is shown to be much more robust than the Kalman method to the placement of pilot symbols in the coded frame. We present numerical results for binary LDPC codes and LDPC-coded modulation, with particular reference to some phase-noise models and coded-modulation formats standardized in the next-generation satellite Digital Video Broadcasting (DVB-S2). These results show that our algorithms achieve near-coherent performance at very low complexity without requiring any change to the existing DVB-S2 standard.

关键词： channels with memory factor graphs (FGs) iterative detection/decoding low-density parity-check (LDPC) codes phase-noise sum-product algorithm (SPA) Tikhonov parameterization

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Noise-predictive turbo equalization for partial-response channels

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IEEE TRANSACTIONS ON MAGNETICS 2005年第10期41卷 2959-2961页

作者： Aviran, S Siegel, PH Wolf, JK Univ Calif San Diego Ctr Magnet Recording Res La Jolla CA 92093 USA

We present a modified turbo equalization scheme that accounts for the colored noise present in high-density partial-response equalization systems. The scheme uses soft information from previous turbo iterations to selectively predict the noise before the next iteration. Simulation results on a PR4 target with low-density parity check (LDPC) coding show that the proposed scheme with up to 2-tap prediction substantially outperforms standard turbo equalization schemes for LDPC-coded EPR4 and PR4 channels.

关键词： iterative detection/decoding noise-predictive turbo equalization partial-response channels

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Noise-predictive turbo equalization for partial-response channels

Noise-predictive turbo equalization for partial-response cha...

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International Magnetics Conference 2005

作者： Aviran, S Siegel, PH Wolf, JK Univ Calif San Diego Ctr Magnet Recording Res La Jolla CA 92093 USA

ISBN: (纸本)0780390091

关键词： iterative detection/decoding noise-predictive turbo equalization partial-response channels

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