无人机下行通信数据传输信号同步设计研究

摘要

在无人机下行通信中,由于多径效应、多普勒效应等信道因素的影响,传输信号如何快速准确地同步是一个重要问题,也是整个传输系统的技术难点.针对上述技术难点问题,提出了一种用于无人机下行正交频分复用(OFDM)无线传输系统的时频同步算法.首先,设计一个特殊的前导训练序列,通过功率分配因子线性叠加到OFDM符号的循环前缀上,很好地保持了训练序列的相关性和循环前缀的数据结构.其次,利用本地训练序列前后两部分和接收信号进行相关运算来实现精准的时间同步和较大范围的频偏估计.最后,利用循环前缀的信息做高精度的频偏估计,实现系统同步范围和同步精度的统一.仿真结果表明,在无人机信道下,选用方法具有良好的时频同步性能.%In this paper,a tim-frequency synchronization algorithm is proposed for Orthogonal Frequency Division Multiplexing (OFDM) wireless transformation system in UAV downlinks.First of all,we used the algorithm to design a special preamble training sequence,which was linearly superposed on the cyclic prefix of OFDM symbols by power distribution factor,maintaining the correlation of training sequence and data structure of cyclic prefix.The second,the received signals were correlated to the former and latter parts of training sequence respectively to achieve precise timing synchronization and frequency offset estimation in wider range.The last,using the information of cyclic prefix to realize high precision frequency offset estimation,the synchronization range and precision of the system can be unified.The simulation results indicate that the proposed method has better timing and frequency synchronization performance in UAV communication channel.