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frequency synchronization for TD-LTE-A downlink receiver

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The Journal of China Universities of Posts and Telecommunications 2012年第1期19卷 31-37页

作者： JIA Guo-qing XIONG Yong YANG Xiu-mei FANG Wei-dong Shanghai Research Center for Wireless Communications Shanghai 200335 China Shanghai Institute of Micro-System and Information Technology Chinese Academy of Sciences Shanghai 200050 China Key Laboratory of Wireless Sensor Network ＆ Communication Shanghai Institute of Micro-System and Information Technology Chinese Academy of Sciences Shanghai 200335 China

A high accuracy frequency synchronization method is proposed for the 3rd generation partnership project （3GPP） long term evolution advanced （LTE-A） downlink receiver in time division duplexing （TDD） mode. In general, cyclic prefix （CP） correlation based fractional frequency offset （FFO） estimation method and primary synchronization signal （PSS） differential correlation based integer frequency offset （IFO） estimation method are applied for LTE-A frequency synchronization. However, the polarity of CP based FFO estimation result may get reversed when system FFO is closer to the edge of frequency estimation range on account of noise interference; PSS based IFO estimation has performance degradation in low signal noise ratio （SNR）. We propose polarity detection aided CP based FFO estimation and frequency domain enhanced differential correlation based IFO estimation to obtain higher accuracy of frequency synchronization. Computer simulation shows that the proposed method greatly outperforms the conventional methods, especially in low SNR scenario.

关键词： Time-division long term evolution advanced (TD-LTE-A) frequency synchronization high accuracy polarity reversion resistance

Performance analysis of frequency synchronization in MIMO-OFDM systems with ST/MRC scheme

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The Journal of China Universities of Posts and Telecommunications 2016年第5期23卷 10-14,39页

作者： Han Daoqi Zhang Jianhua Yu Hao Liu Mengmeng Key Laboratory of Universal Wireless Communications Ministry of EducationBeijing University of Posts and Telecommunications

In this paper, the performance of frequency synchronization in a multiple-input multiple-output orthogonal frequency division multiplexing （MIMO-OFDM） system is analyzed for the purpose of carrier frequency offset （CFO） estimation and compensation. Specifically, a joint transmit antenna selection （ST） and receive maximum ratio combining （MRC）（ST/MRC） method is adopted, that is, only one transmit antenna with the highest channel power is selected while MRC is used at the receiver to maximize the sum of frequency synchronization metric of CFO estimation are derived for several antenna configurations validate the theoretical analysis. The mean square error （MSE） closed-form expressions Simulations in both flat and multipath fading channels

关键词： MIMO OFDM frequency synchronization

Joint optimization of time and frequency synchronization based on polynomial sequences for OFDM systems

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The Journal of China Universities of Posts and Telecommunications 2009年第3期16卷 19-23页

作者： ZHANG Yan-yan ZHANG Jian-hua HUANG Jiang-chun ZHANG Ping Key Laboratory of Universal Wireless Communication Beijing University of Posts and Telecommunications Ministry of Education Beijing 100876 China Wireless Technology Innovation Institute Beijing University of Posts and Telecommunications Beijing 100876 China

In orthogonal frequency division multiplexing （OFDM） systems, time and frequency synchronization are two critical elements for guaranteeing the orthogonality of OFDM subcarriers. Conventionally, with the employment of pseudo-noise （PN） sequences in preamble design, the preamble information is not fully utilized in both symbol timing offset acquisition and carrier frequency offset estimation. In this article, a new synchronization algorithm is proposed for jointly optimizing the time and frequency synchronization. This algorithm uses polynomial sequences as synchronization preamble instead of PN sequences. Theoretical analysis and simulation results indicate that the proposed algorithm is much more accurate and reliable than other existing methods.

关键词： frequency synchronization joint optimization OFDM polynomial sequences timing synchronization

A novel frequency synchronization scheme for OFDM systems

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Journal of Harbin Institute of Technology(New Series) 2008年第5期15卷 653-656页

作者：王雯芳李兵兵 State Key Lab of Integrated Service Networks Xidian University

A novel frequency synchronization scheme for orthogonal frequency division multiplexing (OFDM) systems is proposed, including a novel frequency offset estimation algorithm and a novel frequency offset compensation algorithm. The frequency offset estimation includes both the fractional frequency offset (FFO) estimation and the integral frequency offset (IFO) estimation. Firstly, the FFO was obtained by the conventional ML algorithm in time domain. After the FFO was compensated in time domain, the IFO was obtained by the proposed algorithm based on the energy of virtual carriers. This algorithm needs only simple calculations and has a large frequency offset estimation range. Furthermore, it is insensitive to symbol synchronization errors and channel changing. Finally, the IFO was compensated based on the carrier-positions offset, which can be completed through carrier-positions cyclic shifts in frequency domain. This proposed frequency synchronization scheme can decrease the system redundancy without any need of assistant data, and can be applied to the fast synchronization with the only need of one OFDM symbol. The analyses and simulations show the improved performance of the proposed frequency synchronization scheme.

关键词： OFDM systems frequency synchronization virtual carriers ML

STATISTICAL APPROXIMATION BASED FINE frequency synchronization FOR OFDM SYSTEMS

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Journal of Electronics(China) 2007年第6期24卷 760-764页

作者： Lu Cewu Liu Xiaojun Kuang Yujun Fang Guangyou Chen Qianbin The Institute of Electronics Chinese Academy of Sciences. Beijing 100080 China

The paper proposes a novel approach for fine frequency synchronization of OFDM syn- chronization systems in multi-path channels. Maximum Likelihood (ML) function of frequency offsets including integral and decimal parts in frequency domain is developed according to the law of great number to eliminate the noise impact of the signal. When the timing delay close to the actual time, the proposed function produces a deep valley indicating frequency offset when large Valley-Square- Error (VSE) appears. Coarse timing offset can also be detected when function’s Valley-Square-Error (VSE) is maximized. Simulation results shows that the proposed algorithm gives very robust estimation of frequency offset, and a coarse timing offset estimation.

关键词： Orthogonal frequency Division Multiplexing (OFDM) frequency synchronization Statistical approximation Maximum Likelihood (ML)

Research on time-frequency synchronization technology of multistatic joint observation

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Research on time-frequency synchronization technology of mul...

Carrier frequency offset estimation for a generalized OFDMA uplink

第十一届中国卫星导航年会

作者： Ya Liu Duo-sheng Fan Jia-chen Wang Rui-qiong Chen Xiao-hui Li National Time Service Centre Chinese Academy of Sciences University of CAS

The multi-station joint detection of non-cooperative targets,such as high-dynamic space debris and aircraft,requires the synchronization of time,frequency and phase between stations,and the synchroniz

关键词： Joint detection time synchronization frequency synchronization mobile platform

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High Technology Letters 2011年第4期17卷 333-338页

作者： Zhang Wei Wang Jing Chen Xiang State Key Laboratory on Microwave and Digital Communications Tsinghua National Laboratory for Information Science and Technology Department of Electronic Engineering Tsinghua University Beijing 100084 P.R.China College of Informatlon and Commumcation Engineering Harbin Engineering University Harbin 150001P.R.China

A residual carrier frequency offset （CFO） estimation scheme is proposed for the uplink of orthogonal frequency division multiple access （OFDMA） systems. Multiple access interference caused by CFOs in the uplink is investigated, as it severely affects the performance of a classical maximum likelihood （ML） frequency estimator. By the use of the estimated CFOs of the active users, the linear maximum mean square error （LMMSE） equalization is performed before the ML frequency estimator for the interference cancellation, which can help to sufficiently improve the estimation accuracy for the residual CFO of the incoming user. Analysis and simulations show that the modified ML estimator provides a tradeoff between estimation accuracy and computational complexity caused by the LMMSE interference cancellation, and the proposed method allows OFDMA systems flexibly allocating subcarriers to users.

关键词： OFDMA upliak frequency synchronization maximum likelihood (ML) frequency estimator linear minhnum mean square error (LMMSE) equalization generalized carrier-allocation scheme (GCAS)

Efficient Timing and frequency Offset Estimation Scheme for OFDM Systems

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Transactions of Tianjin University 2009年第1期15卷 27-31页

作者：郭漪葛建华刘刚张武军 National Key Laboratory of Integrated Service Networks Xidian University

A new training symbol weighted by pseudo-noise(PN) sequence is designed and an efficient timing and fre-quency offset estimation scheme for orthogonal frequency division multiplexing(OFDM) systems is proposed. The timing synchronization is accomplished by using the piecewise symmetric conjugate of the primitive training symbol and the good autocorrelation of PN weighted factor. The frequency synchronization is finished by utilizing the training symbol whose PN weighted factor is removed after the timing synchronization. Compared with conventional schemes, the pro-posed scheme can achieve a smaller mean square error and provide a wider frequency acquisition range.

关键词： orthogonal frequency division multiplexing (OFDM) technique time synchronization frequency synchronization training symbol

Real-Time Upstream Services Demonstration in Orthogonal frequency Division Multiplexing- Passive Optical Network System

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China Communications 2014年第1期11卷 26-33页

作者： LI Ming Andrey Lukyanenko Sasu Tarkoma Antti Yl-Jski Department of Computer Science and Engineering Aalto University Department of Computer Science University of Helsinki

Abstract： Real-time digital service and mul- timedia service upstream transmission in Dig- ital Signal Processing （DSP）-based Orthogo- nal frequency Division Multiplexing-Passive Optical Network （OFDM-PON） is experimen- tally demonstrated with Centralised Light Sou- rce （CLS） configuration in this paper. After transmitted over 25 km Standard Single Mode Fibre （SSMF） with -16.5 dBm optical power at receiver, the Bit Error Rate （BER） is 9.5 ×10^-11. The implementations of digital domain up-conversion and down-conversion based on Field Programmable Gate Array （FPGA） are int- roduced, which can reduce the cost of In-ph- ase and Quadrature （IQ） radio frequency mix- ers utilised at transmitter and receiver. A car- rier synchronization algorithm is implemented for compensating carrier offset. A channel eq- ualization algorithm is adopted for compen- sating the damage of channel. A new structure of frequency synchronization Unit （FSU） des- igned in FPGA is also proposed to cope with the frequency shifting at receiver.

关键词： orthogonal frequency division multiplexing-passive optical network real-time field programmable gate array wavelength division multiplexing-OFDM-PON frequency synchronization