OFDM系统改进的训练序列结构及时频同步算法
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摘要
提出了一种改进的基于Zadoff-Chu(ZC)序列的正交频分复用(Orthogonal Frequency Division Multiplexing,OFDM)系统时频同步算法。该算法构造了一个具有共轭重复关系结构的训练序列,首先利用时域训练序列前后的共轭特性完成定时同步,同时得到整数倍频偏估计,使定时结果不受频率同步性能影响,然后在获取精确的定时同步之后利用训练序列的重复性完成小数频偏估计。理论分析和仿真结果表明,在高斯信道和多径信道下,改进算法的定时估计和频偏估计均方误差较低,同时扩大了整数和小数频偏估计范围,降低了系统计算复杂度。
An improved timing and frequency synchronization algorithm based on Zadoff-Chu(ZC) sequence for OFDM system is proposed. The algorithm constructs a training sequence with conjugate repetition relationship. Firstly, the timing synchronization is completed by utilizing the conjugate characteristics of the training sequence in time domain, and the integer frequency offset( IFO)estimation is obtained directly, not affected by the frequency synchronization performance. Then the fractional frequency offset( FFO)estimation is done using the repeatability of the training sequence after timing synchronization. Theoretical analysis and simulation results show that the improved algorithm ′ s timing and frequency offset estimation mean square error is lower, the integer and frac-tional frequency offset estimation range is expanded, and computational complexity is reduced.
An improved timing and frequency synchronization algorithm based on Zadoff-Chu(ZC) sequence for OFDM system is proposed. The algorithm constructs a training sequence with conjugate repetition relationship. Firstly, the timing synchronization is completed by utilizing the conjugate characteristics of the training sequence in time domain, and the integer frequency offset( IFO)estimation is obtained directly, not affected by the frequency synchronization performance. Then the fractional frequency offset( FFO)estimation is done using the repeatability of the training sequence after timing synchronization. Theoretical analysis and simulation results show that the improved algorithm ′ s timing and frequency offset estimation mean square error is lower, the integer and frac-tional frequency offset estimation range is expanded, and computational complexity is reduced.
引文
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[10]刘彬,罗志年,彭疆.改进CAZAC序列的OFDM时域时频同步算法[J].计算机工程与应用,2017,53(14):76-79.
[11]GUL M M U,Ma Xiaoli,LEE S.Timing and frequency synchronization for OFDM downlink transmissions using zadoff-chu sequences[J].IEEE Transactions on Wireless Communication,2015,14(3):1716-1729.
[12]王思拨,马社祥,孟鑫,等.基于训练序列的OFDM频率同步改进算法[J].电子技术应用,2017,43(3):104-107.
[13]WANG W J,TIAN Y,AHN C J.Blind symbol timing synchronization scheme for real-time industrial wireless control network using high-speed preambleless OFDMsystems over multipath fading channels[J].Digital Signal Processing,2017,62:30-37.
[2]HASSINE I B,BOUALLEGUE R.Performances analysis of algebraic space time code under correlated and uncorrelated channels[C].International Conference on Advanced Communication Technology,2014:262-268.
[3]VAN DE BEEK J J,SANDELL M,BORJESSON P O.ML estimation of time and frequency offset in OFDM systems[J].IEEE Transactions on Signal Processing,1997,45(7):1800-1805.
[4]SCHMIDL T M,COX D C.Robust frequency and timing synchronization for OFDM[J].IEEETransactions on Communications,1997,45(12):1613-1621.
[5]MINN H,ZENG M,BHARGAVA V K.On timing offset estimation for OFDM systems[J].IEEE Communications Let ters,2000,4(7):242-244.
[6]PARK B,CHEON H,KANG C,et al.A novel timing estimation method for OFDM systems[J].IEEE Communica tions Letters,2003,7(5):239-241.
[7]ZHOU E,HOU X,ZHANG Z,et al.A preamble structure and synchronization method based on central-symmetric sequence for OFDM systems[C].IEEE Vehicular Technology Conference,2008:1478-1482.
[8]Ren Guangliang,Chang Yilin,Zhang Hui,et al.Synchronization method based on a new constant envelop preamble for OFDM systems[J].IEEE Transactions on Broadcasting,2005,51(1):139-143.
[9]SHAO H,LI Y,TAN J,et al.Robust timing and frequency synchronization based on constant amplitude zero autocorrelation sequence for OFDM systems[C].2014 IEEE International Conference On Communication Problem-Solving(ICCP),2014:14-17.
[10]刘彬,罗志年,彭疆.改进CAZAC序列的OFDM时域时频同步算法[J].计算机工程与应用,2017,53(14):76-79.
[11]GUL M M U,Ma Xiaoli,LEE S.Timing and frequency synchronization for OFDM downlink transmissions using zadoff-chu sequences[J].IEEE Transactions on Wireless Communication,2015,14(3):1716-1729.
[12]王思拨,马社祥,孟鑫,等.基于训练序列的OFDM频率同步改进算法[J].电子技术应用,2017,43(3):104-107.
[13]WANG W J,TIAN Y,AHN C J.Blind symbol timing synchronization scheme for real-time industrial wireless control network using high-speed preambleless OFDMsystems over multipath fading channels[J].Digital Signal Processing,2017,62:30-37.