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Reduced-Complexity turbo equalization for turbo Coded MIMO/OFDM Systems

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The Journal of China Universities of Posts and Telecommunications 2006年第1期13卷 93-98页

作者： JIN Yi-dan ZHANG Feng WU Wei-ling Information Engineering School Beijing University of Posts and Teleeommunications Beijing 100876 P. R China

This paper derives a low-complexity turbo equalization algorithm for turbo coded multiple input multiple output/ orthogonal frequency division multiplexing systems. This algorithm consists of soft-output decision-feedback equalization with a probabilistic data association algorithm and a soft-input soft-output turbo channel decoder using iterative operations. In each iteration, extrinsic information extracted from the probabilistic data association algorithm detector and from the channel decoder is used as the prior information for the next iteration to realize iterative channel equalization and channel decoding, Our simulation results show that the algorithm improves the signal noise ratio around 1 dB with bit error rate reaching 10 -6 when the Eb/ N0 - 4 dB compared to minimum mean square error and match filter, and can greatly reduce the intersymbol interference at a low overall complexity of O（ N^3） after 2 iterations.

关键词： MIMO OFDM turbo equalization probabilistic data association turbo channel decoding 16QAM ISI

Adaptive turbo equalization for Probabilistic Constellation Shaped Underwater Acoustic Communications

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Journal of Beijing Institute of Technology 2021年第3期30卷 280-289页

作者： Xisheng Wu Yanbo Wu Min Zhu Dong Li Institute of Acoustics Chinese Academy of SciencesBeijing 100190China University of Chinese Academy of Sciences Beijing 100049China Beijing Engineering Technology Research Center of Ocean Acoustic Equipment Beijing 100190China State Key Laboratory of Acoustics Chinese Academy of SciencesBeijing 100190China

To increase the spectral efficiency of the underwater acoustic(UWA)communication system,the high order quadrature amplitude modulations(QAM)are ***,the prob-abilistic constellation shaping(PCS)has been a novel technology to improve the spectral *** PCS with high-order QAM is introduced into the UWA communication system.A turbo equal-ization scheme with PCS was proposed to cancel the severe inter-symbol interference(ISI).The non-zero a priori information is available for the equalizer and decoder before turbo iteration.A pri-ori hard decision approach is proposed to improve the detection performance and the equalizer con-vergence *** the initial turbo iteration,the relation between the a priori information and the probability of the amplitude of 16QAM symbols in one dimension is *** simulation results verified the efficiency of the proposed method,and compared to the uniform distribution(UD),the PCS-16QAM had a significant improvement of the bit error rate(BER)performance with PCS-ad-aptive turbo equalization(PCS-ATEQ).The UWA communication experiments further verified the performance superiority of the proposed method.

关键词： high order quadrature amplitude modulation probabilistic constellation shaping UWA multipath channel turbo equalization

Performance Analysis of Hard Iterative Channel Estimation in turbo equalization

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Tsinghua Science and Technology 2006年第5期11卷 574-581页

作者：邓拥军杨知行潘长勇王军 States Key Laboratory on Microwave and Digital Communications Department of Electronic Engineering Tsinghua University

Reasonable bit error rate performance requires perfect channel state information （CSI） in traditional turbo equalization （TE）, which is hard to obtain in practice. Soft and hard iterative algorithms have been developed to address the channel estimation problem with the performance of the soft iteratwe channel estimate based on the recursive least square algorithm. This paper presents an analysis of the performance of hard iterative channel estimation （HICE） based on the least mean square algorithm. The analysis uses a cost function with the hard decision on the TE output. An iterative channel correction （ICC） algorithm based on the gradient descent algorithm is used to iteratively minimize the cost function. The simulation results agree with the theoretical lower bound for the mean square error （MSE） of the estimated channels. Simulations show that, given an imperfect CSI with an MSE below the upper bound, the linear minimum mean squared error TE （LMMSE-TE） using the ICC has only small performance degradation compared to that with a perfect CSI, while the traditional LMMSE-TE suffers from severe error floor effect even with more iterations.

关键词： iterative channel estimation turbo equalization gradient descent algorithm

turbo equalization WITH JOINTLY GAUSSIAN EQUALIZER

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Journal of Electronics(China) 2005年第2期22卷 118-124页

作者： JiangSen SunHong LiPing CollegeofElectronicInformation WuhanUniversityWuhan430072China DeptofElectronicEngineering CityUniversityofHongKongHongKong

A Jointly Gaussian (JG) equalizer is derived for turbo equalization based on an augmented real matrix representation of channel model and a Gaussian approximation of the received symbol sequence. Using matrix inversion lemma and Cholesky decomposition, a lowcomplexity implementation of JG equalizer is also presented. The simulation results and complexity comparison confirm that turbo equalization with JG equalizer has a better performance and a lower complexity than the existing turbo equalization with linear minimum mean squared error equalizer.

关键词： Decoding equalization turbo equalization Iterative method

JOINT MF COMBINING AND turbo equalization FOR WIRELESS COMMUNICATIONS OVER ISI CHANNELS WITH DIVERSITY RECEPTION

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Journal of Electronics(China) 2010年第4期27卷 548-552页

作者： Li Baoguo Lei Jing School of Electronic Science and Engineering National University of Defense Technology Changsha 410073 China

A new method called joint Matched Filter (MF) combining and turbo equalization is proposed for wireless communications over Inter-Symbol Interference (ISI) channels with diversity reception. This method takes diversity combining and equalization as integrity and need just one turbo equalizer for all diversity branches. Computer simulations prove that our method can take advantage of turbo equalization and diversity reception to combat fading of wireless channels.

关键词： Matched Filter (MF) combining turbo equalization Inter-Symbol Interference (ISI) Diversity reception

LOW COMPLEXITY LMMSE turbo equalization FOR COMBINED ERROR CONTROL CODED AND LINEARLY PRECODED OFDM

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Journal of Electronics(China) 2006年第1期23卷 1-6页

作者： Qu Daiming Zhu Guangxi Dept of Electro. ＆ lnfo. Eng. Huazhong University of Sci. ＆ Tech. Wuhan 430074 China

The turbo equalization approach is studied for Orthogonal Frequency Division Multiplexing （OFDM） system with combined error control coding and linear precoding. While previous literatures employed linear precodcr of small size for complexity reasons, this paper proposes to use a linear precoder of size larger than or equal to the maximum length of the equivalent discrete-time channel in order to achieve full frequency diversity and reduce complexities of the error control coder/decoder. Also a low complexity Linear Minimum Mean Square Error （LMMSE） turbo equalizer is derived for the receiver. Through simulation and performance analysis, it is shown that the performance of the proposed scheme over frequency selective fading channel reaches the matched filter bound; compared with the same coded OFDM without linear precoding, the proposed scheme shows an Signal-to-Noise Ratio （SNR） improvement of at least 6dB at a bit error rate of 10 6 over a multipath channel with exponential power delay profile. Convergence behavior of the proposed scheme with turbo equalization using various type of linear precoder/transformer, various interleaver size and error control coder of various constraint length is also investigated.

关键词： Orthogonal Frequency Division Multiplexing (OFDM) Linear precoding turbo equalization Linear Minimum Mean Square Error (LMMSE)

CRC-AIDED turbo equalization FOR MIMO FREQUENCY SELECTIVE FADING CHANNELS

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Journal of Electronics(China) 2007年第1期24卷 69-74页

作者： Liu Zhanli Liang Xiao Zhao Chunming Wang Jing National Mobile Commun. Research Lab. Southeast Univ. Nanjing i10096 China SEUCOMM Corporation Ltd Nanjing 2100P6 China

This paper presents a CRC (Cyclic Redundancy Check)-aided turbo equalization approach to reduce the computational complexity. In this approach,CRC code bits are padded to the end of each transmit block,and a cyclic redundancy check is performed after decoding each block at the receiver end. If the check sum is zero,which means the receive block is correct,the corresponding LLRs (Log Likelihood Ratios) of this block are set high reliable values,and all the computations corresponding to this block can be cancelled for the subsequent outer iterations. With a lower computational complexity the proposed approach can achieve the same as or even better performance than the conventional non-CRC method.

关键词： Cyclic Redundancy Check (CRC) turbo equalization Multi-Input Multi-Output (MIMO)

An Improved MMSE turbo equalization with Matched Filter Based on Hybrid Soft Feedback Interference Concelation

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An Improved MMSE Turbo Equalization with Matched Filter Base...

turbo AIDED CYCLIC PREFIX RECONSTRUCTION FOR CODED SINGLE-CARRIER SYSTEMS WITH FREQUENCY-DOMAIN equalization (SC-FDE)

2010 3rd International Conference on Computer and Electrical Engineering(ICCEE 2010)

作者： Yuxin Cheng Lei Zhang Haige Xiang School of Electronics Engineering and Computer Science Peking University

This paper presents an improved soft feedback interference cancelation scheme which is used in matched filtered minimum mean squared error (MF-MMSE) turbo equalization. In the iterative receiver, a kind of combined prior information and a dynamic updating method are adopted to improve the performance. Simulation results show that the proposed scheme can achieve 0.25 to 0.5 dB performance gain over the original MF-MMSE turbo equalizer.

关键词： turbo equalization iterative receiver combined prior information dynamic updating

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Journal of Electronics(China) 2007年第6期24卷 726-731页

作者： Wei Shengqun Wu Qihui Wang Jinlong Institute of Communication Engineering PLA University of Science and Technology Nanjing 210007 China

In this paper, a turbo aided Cyclic Prefix (CP) reconstruction scheme, termed turbo- CPR, is proposed for Single-Carrier systems with Frequency-Domain equalization (SC-FDE) that employ insufficient CP in the transmitter. In turbo-CPR, the decoder output is incorporated in the process of equalization, i.e. turbo equalizer is employed. It is shown in the simulation results that turbo-CPR not only recovers the performance loss due to insufficiency of CP, but also provides extra gains over the lower bound of performance for conventional CP reconstruction schemes.

关键词： Single-Carrier systems with Frequency-Domain equalization (SC-FDE) Cyclic Prefix (CP) reconstruction InterBlock Interference (IBI) InterSymbol Interference (ISI) turbo equalization