低信噪比下时频联合的载波同步算法
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摘要
针对短突发通信在低信噪比下编码辅助同步算法存在估计精度低和同步范围小的问题,提出了一种时频联合的载波同步(JTDFDCY)算法。首先采用频域估计算法、时域估计算法和最大似然(ML)算法对导频信号进行处理,得到频率粗估计值和相位粗估计值;然后用频率粗估计值和相位粗估计值对接收信号进行补偿,并对补偿后的信号进行解调解码、重新编码、基带调制,得到软判决符号;最后采用时域相关和算法和ML算法对软判决符号进行处理,得到频率细估计值和相位细估计值,进而实现有效的载波同步。仿真结果表明:JTDFDCY算法在低信噪比下的粗估计能够兼顾频率估计范围和估计均方根误差的要求;当归一化频偏在(-0.5,0.5)范围时,仅利用6.1%的导频开销即可将系统的性能损失控制在0.1dB以内。
A joint time-domain and frequency-domain carrier synchronization(JTDFDCY)algorithm is proposed to improve the low estimation accuracy and small synchronization range of code-aided carrier recovery algorithms in the case of low signal to noise ratio(SNR)for short burst communication systems.The coarse frequency estimations and coarse phase estimations are obtained through processing the pilot symbols by the use of the frequency estimation algorithm,the time estimation algorithm,and the ML algorithm.Then the coarse estimations are used to compensate for the received signal,and the compensated signal are demodulated,decoded,reencoded and baseband modulated to get the soft decision symbol.The fine frequency estimation and fine phase estimation are obtained through processing the soft decision symbol by using summation of time-domain correlation and ML algorithm,and eventually, more efficient synchronization carrier is realized.Simulation results show that the proposed JTDFDCY algorithm can satisfy the requirements of frequency estimation range and root mean square error.When the normalized frequency offset is in the range of(-0.5,0.5),the performance degradation of the JTDFDCY algorithm is within 0.1dB at the cost of 6.1% pilot combining with decoder information.
A joint time-domain and frequency-domain carrier synchronization(JTDFDCY)algorithm is proposed to improve the low estimation accuracy and small synchronization range of code-aided carrier recovery algorithms in the case of low signal to noise ratio(SNR)for short burst communication systems.The coarse frequency estimations and coarse phase estimations are obtained through processing the pilot symbols by the use of the frequency estimation algorithm,the time estimation algorithm,and the ML algorithm.Then the coarse estimations are used to compensate for the received signal,and the compensated signal are demodulated,decoded,reencoded and baseband modulated to get the soft decision symbol.The fine frequency estimation and fine phase estimation are obtained through processing the soft decision symbol by using summation of time-domain correlation and ML algorithm,and eventually, more efficient synchronization carrier is realized.Simulation results show that the proposed JTDFDCY algorithm can satisfy the requirements of frequency estimation range and root mean square error.When the normalized frequency offset is in the range of(-0.5,0.5),the performance degradation of the JTDFDCY algorithm is within 0.1dB at the cost of 6.1% pilot combining with decoder information.
引文
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[15]孙锦华,刘鹏,吴小钧.联合旋转平均周期图和解调软信息的载波同步方法[J].电子与信息学报,2013,35(9):2200-2205.SUN Jinhua,LIU Peng,WU Xiaojun.A joint rotational periodogram averaging and demodulation soft information carrier synchronization algorithm[J].Journal of Electronics&Information Technology,2013,35(9):2200-2205.
[16]MENGLI U,D’ANDREA A N.Synchronization techniques for digital receivers[M].New York:Plenum Press,1997:1-4.
[2]BERROU C,GLAVIEUX A,THITIMAJSHIMA P.Near Shannon limit error-correcting coding and decoding:turbo-codes[J].IEEE Transactions on Communications,1996,44(10):1261-1271.
[3]孙锦华,李梦良,吴小钧.连续相位调制和Turbo乘积码的串行级联系统设计[J].西安交通大学学报,2012,46(4):88-93.SUN Jinhua,LI Mengliang,WU Xiaojun.The design of serial concatenated system of Turbo product code with continuous phase modulation[J].Journal of Xi’an Jiaotong University,2012,46(4):88-93.
[4]张毅,欧阳志新,邓云凯,等.高性能无数据辅助QPSK频偏估计新算法[J].西安电子科技大学学报,2013,40(2):187-193.ZHANG Yi,OUYANG Zhixin,DENG Yunkai,et al.New high performance non-data-aided frequency estimation and implementation of QPSK[J].Journal of Xidian University,2013,40(2):187-193.
[5]张帅,张晓林.数字电视大范围载波频偏快速捕获算法[J].北京航空航天大学学报,2013,39(2):225-229.ZHANG Shuai,ZHANG Xiaolin.Rapid large frequency offset estimation for DTMB system[J].Journal of Beijing University of Aeronautics and Astronautics,2013,39(2):225-229.
[6]刘晓东,陈卫东.一种宽范围高精度的载波频偏估计算法[J].无线电工程,2014,44(3):43-45.LIU Xiaodong,CHEN Weidong.Carrier frequency offset estimation algorithm with extended range and high accuracy[J].Radio Engineering,2014,44(3):43-45.
[7]聂少军,何兵哲,王宏卓.一种新的大载波频偏估计算法[J].电子设计工程,2014,22(1):168-170.NIE Shaojun,HE Bingzhe,WANG Hongzhuo.A new estimate algorithm of large carrier frequency offset[J].Electronic Design Engineering,2014,22(1):168-170.
[8]RAHAMIM Y,FREEDMAN A,REICHMAN A.ML iterative tentative-decision-directed(ML-ITDD):a carrier synchronization system for short packet turbo coded communication[C]∥Proceedings of the 200411th IEEE Conference on Electronics,Circuits and System.Piscataway,NJ,USA:IEEE,2004:346-349.
[9]史治平,唐发建,晏辉.极低信噪比下的导频联合编码辅助载波同步算法[J].电子与信息学报,2011,33(10):2506-2510.SHI Zhiping,TANG Jianfa,YAN Hui.Joint assisted carrier synchronization algorithm by pilot and code at extremely low SNR[J].Journal of Electronics&Information Technology,2011,33(10):2506-2510.
[10]FREEDMAN A,RAHAMIM Y,REICHMAN A.Maximum-mean-square soft-output(M2S2 O):a method for carrier synchronization of short burst turbo coded signals[J].IEE Proceedings:Communications,2006,153(2):245-255.
[11]SUN Jinhua,ZHI Jili,WU Xiaojun.A joint pilot and demodulation soft information carrier synchronization for SOQPSK signals[C]∥Proceedings of 2012 5th Global Symposium on Millimeter-Waves.Piscataway,NJ,USA:IEEE,2012:512-516.
[12]HERZET C,NOELS N,LOTTICI V,et al.Codeaided turbo synchronization[J].Proceedings of the IEEE,2007,95(6):1255-1271.
[13]TANG Fajian,SHI Zhiping.Iterative LDPC-Hadamard code-aided carrier frequency synchronization at extremely low SNR[C]∥Proceedings of 2010Second International Conference on Networks Security Wireless Communications and Trusted Computing.Piscataway,NJ,USA:IEEE,2010:314-317.
[14]孙锦华,王雪梅,吴小钧.短突发传输系统的联合导频和迭代译码载波同步[J].西安电子科技大学学报,2014,41(1):29-36.SUN Jinhua,WANG Xuemei,WU Xiaojun.Joint pilot and iterative decoding carrier synchronization for short burst transmission system[J].Journal of Xidian University,2014,41(1):29-36.
[15]孙锦华,刘鹏,吴小钧.联合旋转平均周期图和解调软信息的载波同步方法[J].电子与信息学报,2013,35(9):2200-2205.SUN Jinhua,LIU Peng,WU Xiaojun.A joint rotational periodogram averaging and demodulation soft information carrier synchronization algorithm[J].Journal of Electronics&Information Technology,2013,35(9):2200-2205.
[16]MENGLI U,D’ANDREA A N.Synchronization techniques for digital receivers[M].New York:Plenum Press,1997:1-4.