低信噪比下时频联合的载波同步算法  

Joint Time-Domain and Frequency-Domain Carrier Synchronization Algorithm in Low Signal to Noise Ratio

作　　者：孙锦华[1] 韩会梅[1] 

机构地区：[1]西安电子科技大学综合业务网理论及关键技术国家重点实验室,西安710071

出　　处：《西安交通大学学报》2015年第2期62-68,共7页Journal of Xi'an Jiaotong University

基　　金：国家自然科学基金资助项目(61271175);中央高校基本科研业务费专项资金资助项目(JB140114;K5051201043)

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, re- encoded 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 0.1 dB at the cost of 6.1% pilot combining with decoder information.

关 键 词：低信噪比 导频 载波同步 编码辅助 

分 类 号：TN911.3[电子电信—通信与信息系统]