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China Communications 2023年第1期20卷 199-208页

作者： Lianghui Xie Zhi Quan Osama Elnaha Qinglin Zhao Faculty of Information Technology Macao University of Science and TechnologyMacao 999078China College of Electronic Information Engineering Shenzhen UniversityShenzhen 518060China Department of Electrical Engineering Faculty of EngineeringAssiut UniversityEgypt

The operating frequency accuracy of the local oscillators is critical for the overall system performance in the communication systems.However,the high-precision oscillators could be too expensive for civil applications.In this paper,we propose a model-free adaptive frequency calibration framework for a voltage-controlled crystal oscillator(VCO)equipped with a time to digital converter(TDC),which can significantly improve the frequency accuracy of the VCO thus calibrated.The idea is to utilize a high-precision TDC to directly measure the VCO period which is then passed to a model-free method for working frequency calibration.One advantage of this method is that the working frequency calibration employs the system history of input/output(I/O)data,instead of establishing an accurate VCO voltagecontrolled oscillator model.Another advantage is the lightweight calibration method with low complexity such that it can be implemented on an MCU with limited computation capabilities.Experimental results show that the proposed calibration method can improve the frequency accuracy of a VCO from±20 ppm to±10 ppb,which indicates the promise of the modelfree adaptive frequency calibrator for VCOs.

关键词： frequency calibration carrier frequency offset model-free adaptive control wireless communication systems

New Preamble Sequence for WiMAX System with Improved Synchronization Accuracy

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Intelligent Automation & Soft Computing 2023年第3期35卷 3187-3197页

作者： Suma Sekhar Sakuntala S.Pillai S.Santhosh Kumar Department of Electronics and Communication Engineering LBS Institute of Technology for WomenThiruvananthapuramKeralaIndia Mar Baselios College of Engineering and Technology ThiruvananthapuramKeralaIndia Department of Electronics and Communication Govt.Engineering CollegeIdukkiKeralaIndia

Worldwide Interoperability for Microwave Access(WiMAX)trusts Multiple Input Multiple Output-Orthogonal frequency Division Multiplexing(MIMO-OFDM)combination for the deployment of physical layer functions and for connecting the medium access control to the wireless media.Even though Orthogonal frequency Division Multiplexing(OFDM)facilitates reliable digital broadband transmission in the fading wireless channels,the presence of synchro-nization errors in the form of carrier frequency offset(CFO)and Time offset(TO)adversely affect the performance of OFDM based physical layers.The objective of this work is to improve the accuracy of the frequency and the time offset estimation in the WiMAX physical layer.A method to enhance the synchro-nization accuracy byﬁne-tuning the merit factor of the preamble sequence is sug-gested in this paper.Also,a new preamble with improved synchronization accuracy is proposed for the WiMAX system.The performance of the proposed preamble is evaluated in a Rayleigh fading channel and the results of simulations show that the Mean Square Error(MSE)in offset estimation is signiﬁcantly reduced and it outperforms the standard WiMAX preamble.

关键词： WiMAX MIMO OFDM time offset carrier frequency offset preamble sequence integrated sidelobe level merit factor

frequency Synchronization Based on a Cascading Cross-Correlation Function for CO-FBMC-OQAM

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Chinese Journal of Electronics 2020年第4期29卷 724-730页

作者： WANG Daobin CHEN Bo LYU Ningning WANG Wei LIU Junjie YUAN Lihua School of Science Lanzhou University of Technology School of Electrical and Information Engineering Lanzhou University of Technology

We present a robust frequency synchronization algorithm for the Coherent optical offset quadrature-amplitude modulation based Filter-bank multicarrier(CO-FBMC-OQAM) systems.It is a two-stage method operating in the frequency domain, which expands the estimated range of the normalized fractional frequency offset to(-1, +1).We designed and introduced a cascading cross-correlation function of real-valued pilots to roughly estimate the frequency offset in the first stage.The residual frequency offset was accurately tracked by a non-cascading cross-correlation function afterwards.This approach enlarges the maximum estimated range, and also resists interference and noise.A CO-FBMC-OQAM system with the sampling rate of 50 Gsample/s was numerically investigated to evaluate the frequency-offset estimation and compensation capability.All obtained results prove that the proposed frequency synchronization method can correct the laser-frequency offset and improve the transmission performance significantly.

关键词： CO-FBMC-OQAM carrier frequency offset frequency synchronization Cascading cross-correlation function

Complexity Effective frequency and Sidelink Synchronization Algorithm for LTE Device-to-Device Communication Systems

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Computers, Materials & Continua 2020年第1期62卷 443-458页

作者： Yong-An Jung Min-Goo Kang Young-Hwan You Department of Computer Engineering Sejong UniversitySeoulKorea Department of IT Contents Hanshin UniversityGyeonggi-doKorea

Device-to-device(D2D)communication is considered as a major challenge in the long term evolution(LTE)network wherein devices directly communicate with each other.One of the key challenges in D2D sidelink is reliable and reduced-complexity synchronization.To address this issue,a computationally efficient sequential detection scheme for integer carrier frequency offset and sidelink identity is proposed in the LTE-D2D system.To perform the frequency offset detection without retrieving the sidelink identity,the conjugate relation between two primary sidelink synchronization sequences is exploited,which facilitates the detection tasks of frequency offset and sidelink identity to be decoupled.It is demonstrated from simulation results that the inherent property of the sidelink synchronization sequences is effectively used for joint detection of frequency offset and sidelink identity with significantly reduced complexity,compared to existing estimation schemes.

关键词： Long term evolution device-to-device communication carrier frequency offset sidelink identity sidelink synchronization

A Novel OFDM Receiver with Optimum Second Order Polynomial Nyquist Windowing

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The Journal of China Universities of Posts and Telecommunications 2006年第2期13卷 84-89,102页

作者： SONG Rong-fang AI Si LEUNG Shu-hung College of Telecommunications and Information Engineering Nanjing University of P~ts and Telecommunications Nanjing 210003 P.R. China National Mobile Communications Research Laboratory Southeast University Nanjing 210096 P.R. China Department of Electronic Engineering City University of Hong Kong Kowloon Hong Kong P.R. China

This paper proposes a new receive scheme and a class of time domain second order polynomial Nyquist window functions, and applies them to Orthogonal frequency-Division Multiplexing （ OFDM ） systems in order to reduce Inter-carrier Interference （ICI） induced by frequency offset. This paper also analyzes the Signal to ICI plus Noise Ratio （SINR） and Bit Error Rate （BER） performances of the receiver. Additionally, this paper proposes a method to select optimum window parameters to maximize the SINR of the receiver thus providing an adaptive receiving capability. Our results show that the proposed method enables the use of unity roll-off factor, provides better SINR and BER than conventional receive methods whose roll-off factors are generally less than one. The new second order polynomial window is shown to provide better performance than raised cosine and ＂better than ＂ Nyquist window.

关键词： OFDM Nyquist window inter-carrier interference carrier frequency offset

Hard Decision Directed frequency Tracking for OFDM on frequency Selective Channel

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Tsinghua Science and Technology 2012年第2期17卷 202-208页

作者： Guanping Lu Jun Wang Chao Zhang Zhaocheng Wang Tsinghua National Laboratory for Information Science and Technology(TNList) Department of Electronic EngineeringTsinghua UniversityBeijing 100084China

This paper presents a decision directed frequency tracking scheme to improve the spectrum efficiency of Orthogonal frequency Division Modulation （OFDM） transmission for frequency selective channels. OFDM divides a broadband channel into parallel narrowband subchannels with different channel characteristics. The subcarriers with lower attenuation are selected to do the decision directed based frequency tracking. A phase error detection method is needed to keep the hard decision working stable during tracking. The algorithm ensures that the carrier frequency offset could be solved from the detected phase error. The Mean Square Error （MSE） estimate and the loop bandwidth are also presented. Simulations illustrate that this scheme has better MSE and bit error rate performance than the traditional scheme. Furthermore, the pilots are saved in this scheme, which lead to improved spectrum efficiency.

关键词： decision directed synchronization tracking carrier frequency offset

An Improved Algorithm for Blind carrier frequency Estimation with Burst MPSK Transmissions

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Wuhan University Journal of Natural Sciences 2013年第1期18卷 55-58页

作者： YUAN Xiaohua ZHENG Hui ZHAO Zhengyu ZHOU Chen National Key Laboratory of Blind Signals Processing School of Electronic Information Wuhan University

This paper presents an improved non-data-aided algo- rithm for carrier frequency estimation for burst M-ary PSK signals when modulation order M and training symbols are unknown. Unlike data-aided estimation, a phase clustering algorithm is used first to estimate M and modulated information is removed by a vari- able interval linear phase unwrapping. Then, a high-order correlation algorithm with proper correction is present, which reduces the probability of phase ambiguity and promotes anti-noise capability of the estimation. Simulations are given to analyze the unbiased esti- mation range, and the asymptotic performance and symbol number are needed to compare with the former algorithms. The new algo- rithm has a large estimation range close to the theoretical maximum value for non-data-aided estimation and has a better performance than earlier non-data-aided techniques for large frequency offset, low signal-to-noise ratio, and limited symbol numbers.

关键词： burst MPSK signal automatic modulation recognition non-data-aided carrier frequency offset linear phase unwrapping high-order correlation

An Improved Frame Synchronization Method Based on Correlation Window Division 11th

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An Improved Frame Synchronization Method Based on Correlatio...

A Method to Improve the Bandwidth Efficiency of Self ICI Cancellation in OFDM Systems

2012 IEEE 11th International Conference on Solid-State and Integrated Circuit Technology(ICSICT-2012)

作者： Xiaoxin Cui Bin Sun Institute of Microelectronics Peking University

ISBN: (纸本)9781467324748

Frame synchronization is susceptible to carrier frequency offset.To solve the problem,the correlation window division method for frame synchronization is presented in this paper.This algorithm divides the correlation window into several sub-sections and calculates the correlation value of each sub-section separately,and then combines these values to detect frame synchronization signal.The simulation results show that this method can detect the starting position of frame sequence precisely in presence of large carrier frequency offset.Besides,low complexity of realization and high utilization of hardware resource are achieved.

关键词： resource complexity utilization windows windows frame synchronization window Complexity carrier frequency offset Simulation results hardware resource

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A Method to Improve the Bandwidth Efficiency of Self ICI Can...