【摘要】 在OFDM水声通信中,收发双方非匀速运动时,传统的多普勒估计方法误差较大。提出了一种基于导频chirp Z变换的基带OFDM水声通信多普勒估计方法。该方法针对OFDM水声通信中的基带传输特性,取低频端的子载波为导频信号,对每个OFDM符号进行Chirp Z变换估计其多普勒因子。该方法估计精度高,仿真结果表明相对运动速度小于20 m/s时,估计多普勒因子的误差小于3.6×10-6,较传统的时域相关法误差小2个数量级;初速度小于20 m/s、加速度小于1.4 m/s2时估计的多普勒因子与符号平均多普勒因子的误差均小于3.6×10-6;用线性插值方法对多普勒补偿,不同运动速度、加速度以及多径条件下的仿真性能,验证了变速运动时该方法对OFDM接收信号多普勒估计及补偿的有效性。更多还原

【Abstract】 Aim.In OFDM(Orthogonal Frequency Division Multiplexing) underwater acoustic communication,when the transmitter and the receiver have a relative acceleration,the traditional Doppler shift estimation method has big error.Our efficient estimation method can,we believe,suppress greatly this error.Section 1 of the full paper deals with OFDM base-band transmission for underwater acoustic communication.Sections 2 and 3 select pilot frequency signals in accordance with the interpolation method explained in Fig.2.Using eqs.(11),(12) and(13) in section 3 can estimate the Doppler shift with high precision by the process of Chirp Z transformation for each OFDM symbol.The simulation results,shown in Figs.4 through 9,indicate preliminarily that:(1) when the speed of the transmitter relative to that of the receiver is less than 20m/s,the estimation error of our Doppler shift method is less than 3.6×10-6,which is two orders of magnitude smaller than that of the traditional method;(2) the estimation error of our Doppler shift method is also less than 3.6×10-6 when the initial speed of the transmitter relative to that of the receiver is less than 20m/s and the relative acceleration is less than 1.4m/s2;(3) the OFDM system’s performance curve of error bit rate validates that our method is useful for reception signal’s estimation and compensation when there is a relative acceleration.更多还原