WO2018103036A1

WO2018103036A1 - Doppler frequency offset estimation method and device and doppler frequency offset elimination method and device in ofdm system

Info

Publication number: WO2018103036A1
Application number: PCT/CN2016/109003
Authority: WO
Inventors: 张奇勋; 高超; 冯志勇; 郑婷婷; 张鹏毅
Original assignee: Beijing University of Posts and Telecommunications
Current assignee: Beijing University of Posts and Telecommunications
Priority date: 2016-12-05
Filing date: 2016-12-08
Publication date: 2018-06-14
Anticipated expiration: 2019-06-05
Also published as: CN106559375A; CN106559375B

Abstract

Embodiments of the present application provide a Doppler frequency offset estimation method and device and a Doppler frequency offset elimination method and device in an OFDM system. The Doppler frequency offset estimation method in the OFDM system comprises: receiving an OFDM transmission signal, wherein a first OFDM symbol in a first OFDM frame in the OFDM transmission signal comprises Q preset cyclic prefixes, and Q is greater than or equal to 3; performing paired autocorrelation on all the preset cyclic prefixes to obtain a plurality of autocorrelation functions; summing all the autocorrelation functions to obtain a probability density function; performing maximum likelihood estimation on the probability density function to obtain an initial Doppler frequency offset and a Doppler change rate; and estimating, according to the initial Doppler frequency offset and the Doppler change rate, a target Doppler frequency offset that varies with a change of a signal sequence position in the first OFDM frame. The embodiments of the present application improve the accuracy of an estimation result and increase the effect of elimination of a Doppler effect.

Description

Doppler frequency offset estimation method and device and elimination method and device in OFDM system

本申请要求于2016年12月5日提交中国专利局、申请号为201611103120.X发明名称为“OFDM系统中多普勒频偏估计方法及装置和消除方法及装置”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。This application claims priority to Chinese Patent Application No. 201611103120.X entitled "Doppler Frequency Offset Estimation Method and Apparatus and Apparatus and Elimination Method and Apparatus in OFDM System" on December 5, 2016 The entire content of which is incorporated herein by reference.

Technical field

本申请涉及无线通信技术领域，特别是涉及一种OFDM系统中多普勒频偏估计方法及装置和消除方法及装置。The present application relates to the field of wireless communication technologies, and in particular, to a Doppler frequency offset estimation method and apparatus, and a cancellation method and apparatus in an OFDM system.

Background technique

当发射端与接收端之间存在相对运动时，发射端发射的源信号在传播过程中，其相位和频率会发生变化，接收端接收到的信号的频率与源信号的频率不同，这种现象称为多普勒效应，接收端接收到的信号的频率与源信号的频率之差称为多普勒频偏。由于多普勒频偏的影响，接收端接收到的信号通常会出现干扰、失真或数据丢失等问题。When there is relative motion between the transmitting end and the receiving end, the phase and frequency of the source signal transmitted by the transmitting end will change during the propagation process, and the frequency of the signal received by the receiving end is different from the frequency of the source signal. Known as the Doppler effect, the difference between the frequency of the signal received at the receiving end and the frequency of the source signal is called the Doppler shift. Due to the influence of Doppler frequency offset, the signal received by the receiving end usually has problems such as interference, distortion or data loss.

在OFDM(Orthogonal Frequency Division Multiplexing，正交频分复用)系统中，发射端发射的每个OFDM源信号中包括多个OFDM帧，每一个OFDM帧包括多个OFDM符号，各个OFDM符号的频率互不相同，因此各OFDM符号间是相互正交的，可避免OFDM符号间的干扰。如果存在多普勒频偏的影响，OFDM源信号中各个OFDM符号的频率会发生偏移，出现频率重叠的情况，这将破坏各OFDM符号间的正交性，导致OFDM符号间产生干扰。In an OFDM (Orthogonal Frequency Division Multiplexing) system, each OFDM source signal transmitted by a transmitting end includes a plurality of OFDM frames, and each OFDM frame includes a plurality of OFDM symbols, and frequencies of the respective OFDM symbols are mutually Different, so each OFDM symbol is orthogonal to each other, and interference between OFDM symbols can be avoided. If there is a Doppler frequency offset, the frequency of each OFDM symbol in the OFDM source signal will be offset, and the frequency overlap will occur, which will destroy the orthogonality between the OFDM symbols, resulting in interference between the OFDM symbols.

为了减小OFDM符号间的干扰，研究者通常会对OFDM传播信号(定义OFDM传播信号为OFDM源信号在传播过程中受到多普勒效应影响后产生的信号)进行多普勒频偏的估算，将估算的多普勒频偏发送给发射端，使发射端按如下方式进行对多普勒效应进行消除：根据接收到的多普勒频偏，对待发射的OFDM源信号进行多普勒频偏反向处理，获得目标OFDM源信号；发送目标OFDM源信号，该信号在传播过程中由于再次受到多普勒效应的影响，两次多普勒频偏相互抵消，从而减小了多普勒效应对OFDM源信号的影响。In order to reduce the interference between OFDM symbols, the researchers usually estimate the Doppler frequency offset of the OFDM propagation signal (defining the OFDM propagation signal is the signal generated by the Doppler effect during the propagation of the OFDM source signal). The estimated Doppler frequency offset is sent to the transmitting end, so that the transmitting end cancels the Doppler effect as follows: according to the received Doppler frequency offset, the Doppler frequency offset of the OFDM source signal to be transmitted is performed. Reverse processing, obtaining the target OFDM source signal; transmitting the target OFDM source signal, the signal is again affected by the Doppler effect during the propagation process, and the two Doppler frequency offsets cancel each other, thereby reducing the Doppler effect The effect on the OFDM source signal.

在实际情况下，OFDM传播信号中的多普勒频偏在OFDM传播信号中是随着信号序列的位置而变化的(即在同一个OFDM传播信号中信号前端的序列和信号后端的序列的多普勒频偏是不同的)，定义多普勒变化率为表示多普勒频偏在OFDM传播信号中随信号序列位置变化的快慢，随着发射端与接收端之间相对速度的增加，多普勒变化率也会逐渐变大。In practical situations, the Doppler frequency offset in the OFDM propagation signal varies with the position of the signal sequence in the OFDM propagation signal (ie, the sequence of the signal front end and the sequence of the signal back end in the same OFDM propagation signal Le-Frequency is different), defining the Doppler rate of change to represent Doppler The frequency of the OFDM propagation signal varies with the position of the signal sequence. As the relative speed between the transmitting end and the receiving end increases, the Doppler rate of change will gradually increase.

现有技术中，OFDM传播信号中随信号序列位置变化的多普勒频偏的估算方法为：In the prior art, the estimation method of the Doppler frequency offset in the OFDM propagation signal as the position of the signal sequence changes is:

从OFDM传播信号中找到第一个OFDM符号和第二个OFDM符号，获取这两个OFDM符号中的预设循环前缀(预设循环前缀为在OFDM传播信号中位置信息预先设定的循环前缀)，对这两个预设循环前缀进行自相关，得到一个自相关函数，对该自相关函数进行最大似然估计，得到起始多普勒频偏(第一个预设循环前缀的多普勒频偏)和多普勒变化率，并根据该预设循环前缀的多普勒频偏和多普勒变化率估算OFDM传播信号中随信号序列位置变化的多普勒频偏。Finding a first OFDM symbol and a second OFDM symbol from the OFDM propagation signal, and acquiring a preset cyclic prefix in the two OFDM symbols (the preset cyclic prefix is a cyclic prefix preset by the location information in the OFDM propagation signal) Autocorrelation is performed on the two preset cyclic prefixes to obtain an autocorrelation function, and the maximum likelihood estimation of the autocorrelation function is performed to obtain a starting Doppler frequency offset (Doppler of the first preset cyclic prefix) The frequency offset) and the Doppler rate of change, and the Doppler frequency offset in the OFDM propagation signal as a function of the position of the signal sequence is estimated based on the Doppler frequency offset and the Doppler rate of change of the preset cyclic prefix.

但由于发射端、接收端以及周围环境各种因素的影响，发射端每次发射的OFDM源信号在传播的过程中，都会发生不同的变化，且变化是随机的无任何规律可循，因此，如果按照现有技术的方法，仅仅选取两个预设循环前缀进行自相关，得到的OFDM传播信号中随信号序列位置变化的多普勒频偏估算结果误差较大，不能很好的描述OFDM传播信号中多普勒频偏的实际大小，准确性不高；并且，发射端按这种方式获得多普勒频偏后，对OFDM源信号进行多普勒频偏反向处理时，消除多普勒效应的效果也有待提高。However, due to various factors such as the transmitting end, the receiving end and the surrounding environment, each time the OFDM source signal transmitted by the transmitting end is in the process of propagation, different changes will occur, and the change is random without any regularity. Therefore, According to the prior art method, only two preset cyclic prefixes are selected for autocorrelation, and the Doppler frequency offset estimation result of the signal sequence position change in the obtained OFDM propagation signal is large, which cannot describe the OFDM propagation well. The actual size of the Doppler frequency offset in the signal is not high; and, after the Doppler frequency offset is obtained in this way, the Doppler frequency offset is applied to the OFDM source signal, and Doppler is eliminated. The effect of the Le effect also needs to be improved.

发明内容Summary of the invention

本申请实施例的目的在于提供一种OFDM系统中多普勒频偏估计方法及装置和消除方法及装置，以减小OFDM传播信号中随信号序列位置变化的多普勒频偏估算结果的误差，提高准确性，并提高消除多普勒效应的效果。The purpose of the embodiments of the present application is to provide a Doppler frequency offset estimation method and apparatus, and a cancellation method and apparatus for the OFDM system, so as to reduce the error of the Doppler frequency offset estimation result of the signal sequence position change in the OFDM propagation signal. , improve accuracy, and improve the effect of eliminating the Doppler effect.

为达到上述目的，本申请实施例提供了一种OFDM系统中多普勒频偏估计方法，应用于接收端，所述方法包括：To achieve the above objective, the embodiment of the present application provides a Doppler frequency offset estimation method in an OFDM system, which is applied to a receiving end, and the method includes:

接收OFDM传播信号；所述OFDM传播信号中第一个OFDM帧中的第一个OFDM符号中包含Q个预设循环前缀；Q大于或等于3；Receiving an OFDM propagation signal; the first OFDM symbol in the first OFDM frame of the OFDM propagation signal includes Q preset cyclic prefixes; Q is greater than or equal to 3;

对所有预设循环前缀进行两两自相关，得到多个自相关函数；Performing two-two autocorrelation on all preset cyclic prefixes to obtain multiple autocorrelation functions;

对所有自相关函数进行求和，得到概率密度函数；Summing all autocorrelation functions to obtain a probability density function;

对所述概率密度函数进行最大似然估计，得到起始多普勒频偏和第一多普勒变化率；Performing maximum likelihood estimation on the probability density function to obtain an initial Doppler frequency offset and a first Doppler rate of change;

根据所述起始多普勒频偏和所述第一多普勒变化率估算所述OFDM传播信号中第一个OFDM帧内随信号序列位置变化的目标多普勒频偏。Estimating the OFDM propagation based on the initial Doppler shift and the first Doppler rate of change The target Doppler shift in the first OFDM frame of the signal as a function of the position of the signal sequence.

可选的，所述对所有预设循环前缀进行两两自相关，得到多个自相关函数的步骤，包括：Optionally, the step of performing a pairwise autocorrelation on all preset cyclic prefixes to obtain multiple autocorrelation functions includes:

对所有预设循环前缀进行采样，得到Q×L个分段信号；其中，各预设循环前缀的采样数量为L；Sampling all the preset cyclic prefixes to obtain Q×L segmentation signals; wherein, the sampling number of each preset cyclic prefix is L;

根据所述Q×L个分段信号对所有预设循环前缀进行两两自相关，得到多个自相关函数；其中，对任意两个预设循环前缀第一预设循环前缀和第二预设循环前缀进行自相关得到L个自相关函数；所述对第一预设循环前缀和第二预设循环前缀进行自相关的方式包括：分别对所述第一预设循环前缀的第k个分段信号和所述第二预设循环前缀内的第k个分段信号进行自相关；k＝0,1,...L-1。Performing two-two autocorrelation on all preset cyclic prefixes according to the Q×L segmentation signals to obtain multiple autocorrelation functions; wherein, for any two preset cyclic prefixes, the first preset cyclic prefix and the second preset The cyclic prefix performs autocorrelation to obtain L autocorrelation functions; the manner of autocorrelation between the first preset cyclic prefix and the second preset cyclic prefix includes: respectively, the kth sub-division of the first preset cyclic prefix The segment signal and the kth segment signal in the second preset cyclic prefix are autocorrelated; k=0, 1, . . . L-1.

可选的，所述自相关函数的计算公式为：Optionally, the calculation formula of the autocorrelation function is:

其中，m＝hL，h＝1,2,3,…Q-1，n＝kT_s，T_s为采样间隔，r[n]为所述OFDM传播信号中第一个OFDM帧中第一个OFDM符号中第一个预设循环前缀中第n时刻的波形函数，

为所述OFDM传播信号第n时刻的平均信号能量，ε₀为所述起始多普勒频偏，

为所述第一多普勒变化率，Δf_Doppler为以H_z/s为单位的第二多普勒变化率，

表示的是分段信号空间，N为一个OFDM符号中分段信号的个数，n∈I₀，I_i为第i个预设循环前缀的分段信号，I_i＝{iL,iL+1,…,iL+l-1}，i＝0,1,…Q-1。Where m = hL, h = 1, 2, 3, ... Q-1, n = kT _s , T _s is the sampling interval, r [n] is the first of the first OFDM frames in the OFDM propagation signal The waveform function at the nth time in the first preset cyclic prefix in the OFDM symbol,

For the average signal energy at the nth moment of the OFDM propagation signal, ε ₀ is the initial Doppler frequency offset,

For the first Doppler rate of change, Δf _Doppler is the second Doppler rate of change in H _z /s,

Indicates the segmented signal space, where N is the number of segmented signals in one OFDM symbol, n∈I ₀ , I _i is the segmented signal of the ith preset cyclic prefix, I _i ={iL,iL+1 ,...,iL+l-1},i=0,1,...Q-1.

可选的，所述概率密度函数的计算公式为：Optionally, the formula for calculating the probability density function is:

其中，

为所述概率密度函数。 among them,

Is the probability density function.

可选的，所述对所述概率密度函数进行最大似然估计，得到起始多普勒频偏和第一多普勒变化率的步骤，包括：Optionally, the step of performing maximum likelihood estimation on the probability density function to obtain a starting Doppler frequency offset and a first Doppler rate of change, including:

根据公式According to the formula

计算所述起始多普勒频偏和所述第一多普勒变化率，得到所述起始多普勒频偏和所述第一多普勒变化率。Calculating the initial Doppler shift and the first Doppler rate of change to obtain the initial Doppler shift and the first Doppler rate of change.

可选的，所述根据所述起始多普勒频偏和所述第一多普勒变化率估算所述OFDM传播信号中随信号序列位置变化的目标多普勒频偏的步骤，包括：Optionally, the step of estimating a target Doppler frequency offset of the OFDM propagation signal according to the position of the signal sequence according to the initial Doppler frequency offset and the first Doppler rate of change, including:

根据公式ε_k＝ε₀+αk，估算所述目标多普勒频偏；Estimating the target Doppler frequency offset according to the formula ε _k = ε ₀ + αk;

其中，ε_k为所述目标多普勒频偏。Where ε _k is the target Doppler shift.

本申请实施例还提供了一种OFDM系统中多普勒频偏消除方法，应用于发射端，所述方法包括：The embodiment of the present application further provides a Doppler frequency offset elimination method in an OFDM system, which is applied to a transmitting end, and the method includes:

接收接收端发送的目标多普勒频偏；所述目标多普勒频偏为接收端根据上述OFDM系统中多普勒频偏估计方法估算得到的；Receiving a target Doppler frequency offset sent by the receiving end; the target Doppler frequency offset is estimated by the receiving end according to the Doppler frequency offset estimation method in the OFDM system;

根据所述目标多普勒频偏，对待发射的OFDM源信号进行多普勒频偏反向处理，获得目标OFDM源信号；Performing Doppler frequency offset processing on the OFDM source signal to be transmitted according to the target Doppler frequency offset to obtain a target OFDM source signal;

发送所述目标OFDM源信号。Transmitting the target OFDM source signal.

本申请实施例还提供了一种OFDM系统中多普勒频偏估计装置，应用于接收端，所述装置包括：The embodiment of the present application further provides a Doppler frequency offset estimation apparatus in an OFDM system, which is applied to a receiving end, and the apparatus includes:

接收模块，用于接收OFDM传播信号；所述OFDM传播信号中第一个OFDM帧中的第一个OFDM符号中包含Q个预设循环前缀；Q大于或等于3；a receiving module, configured to receive an OFDM propagation signal; the first OFDM symbol in the first OFDM frame of the OFDM propagation signal includes Q preset cyclic prefixes; Q is greater than or equal to 3;

自相关模块，用于对所有预设循环前缀进行两两自相关，得到多个自相关函数；An auto-correlation module for performing two-two autocorrelation on all preset cyclic prefixes to obtain a plurality of autocorrelation functions;

求和模块，用于对所有自相关函数进行求和，得到概率密度函数；a summation module for summing all autocorrelation functions to obtain a probability density function;

最大似然估计模块，用于对所述概率密度函数进行最大似然估计，得到起始多普勒频偏和第一多普勒变化率；a maximum likelihood estimation module, configured to perform maximum likelihood estimation on the probability density function to obtain an initial Doppler frequency offset and a first Doppler rate of change;

估算模块，用于根据所述起始多普勒频偏和所述第一多普勒变化率估算所述OFDM传播信号中第一个OFDM帧内随信号序列位置变化的目标多普勒频偏。An estimating module, configured to estimate a target Doppler frequency offset of a signal sequence change in the first OFDM frame of the OFDM propagation signal according to the initial Doppler frequency offset and the first Doppler rate of change .

可选的，所述自相关模块，包括： Optionally, the autocorrelation module includes:

采样单元，用于对所有预设循环前缀进行采样，得到Q×L个分段信号；其中，各预设循环前缀的采样数量为L；a sampling unit, configured to sample all the preset cyclic prefixes to obtain Q×L segmentation signals; wherein, the sampling number of each preset cyclic prefix is L;

自相关单元，用于根据所述Q×L个分段信号对所有预设循环前缀进行两两自相关，得到多个自相关函数；其中，对任意两个预设循环前缀第一预设循环前缀和第二预设循环前缀进行自相关得到L个自相关函数；所述对第一预设循环前缀和第二预设循环前缀进行自相关的方式包括：分别对所述第一预设循环前缀的第k个分段信号和所述第二预设循环前缀内的第k个分段信号进行自相关；k＝0,1,...L-1。An auto-correlation unit, configured to perform a pairwise autocorrelation on all preset cyclic prefixes according to the Q×L segmentation signals to obtain multiple autocorrelation functions; wherein, the first preset cycle of any two preset cyclic prefixes The auto-correlation function is obtained by performing auto-correlation on the prefix and the second preset cyclic prefix; the manner of performing auto-correlation on the first preset cyclic prefix and the second preset cyclic prefix comprises: separately performing the first preset loop The k-th segment signal of the prefix and the k-th segment signal in the second preset cyclic prefix are autocorrelated; k=0, 1, . . . L-1.

本申请实施例还提供了一种OFDM系统中多普勒频偏消除装置，应用于发射端，所述装置包括：The embodiment of the present application further provides a Doppler frequency offset canceling apparatus in an OFDM system, which is applied to a transmitting end, and the apparatus includes:

接收模块，用于接收接收端发送的目标多普勒频偏；所述目标多普勒频偏为接收端根据上述OFDM系统中多普勒频偏估计装置估算得到的；a receiving module, configured to receive a target Doppler frequency offset sent by the receiving end; the target Doppler frequency offset is estimated by the receiving end according to the Doppler frequency offset estimating apparatus in the OFDM system;

反向处理模块，用于根据所述目标多普勒频偏，对待发射的OFDM源信号进行多普勒频偏反向处理，获得目标OFDM源信号；a reverse processing module, configured to perform Doppler frequency offset processing on the OFDM source signal to be transmitted according to the target Doppler frequency offset, to obtain a target OFDM source signal;

发送模块，用于发送所述目标OFDM源信号。And a sending module, configured to send the target OFDM source signal.

为达到上述目的，本申请实施例提供了一种接收端，所述接收端包括：壳体、处理器、存储器、电路板和电源电路，其中，电路板安置在壳体围成的空间内部，处理器和存储器设置在电路板上；电源电路，用于为接收端的各个电路或器件供电；存储器用于存储可执行程序代码；处理器通过读取存储器中存储的可执行程序代码来运行与可执行程序代码对应的应用程序，以用于执行本申请实施例所提供的任意一种OFDM系统中多普勒频偏估计方法。To achieve the above objective, the embodiment of the present application provides a receiving end, the receiving end includes: a housing, a processor, a memory, a circuit board, and a power supply circuit, wherein the circuit board is disposed inside the space enclosed by the housing, The processor and the memory are disposed on the circuit board; the power circuit is configured to supply power to each circuit or device at the receiving end; the memory is used to store the executable program code; and the processor is operable to read the executable program code stored in the memory. The application program corresponding to the program code is executed to perform the Doppler frequency offset estimation method in any one of the OFDM systems provided by the embodiments of the present application.

为达到上述目的，本申请实施例提供了一种存储介质，所述存储介质用于存储应用程序，所述应用程序用于执行本申请实施例所提供的任意一种OFDM系统中多普勒频偏估计方法。To achieve the above objective, the embodiment of the present application provides a storage medium, where the storage medium is used to execute an application, and the application is used to perform Doppler frequency in any OFDM system provided by the embodiments of the present application. Partial estimation method.

为达到上述目的，本申请实施例提供了一种应用程序，所述应用程序用于执行本申请实施例所提供的任意一种OFDM系统中多普勒频偏估计方法。To achieve the above objective, the embodiment of the present application provides an application program, which is used to perform a Doppler frequency offset estimation method in any OFDM system provided by the embodiments of the present application.

为达到上述目的，本申请实施例提供了一种发射端，所述发射端包括：壳体、处理器、存储器、电路板和电源电路，其中，电路板安置在壳体围成的空间内部，处理器和存储器设置在电路板上；电源电路，用于为发射端的各个电路或器件供电；存储器用于存储可执行程序代码；处理器通过读取存储器中存储的可执行程序代码来运行与可执行程序代码对应的应用程序，以用于执行本申请实施例所提供的OFDM系统中多普勒频偏消除方法。To achieve the above objective, the embodiment of the present application provides a transmitting end, the transmitting end includes: a housing, a processor, a memory, a circuit board, and a power supply circuit, wherein the circuit board is disposed inside the space enclosed by the housing, The processor and the memory are disposed on the circuit board; the power circuit is configured to supply power to each circuit or device of the transmitting end; the memory is used to store executable program code; and the processor is operable to read the executable program code stored in the memory. Execute the application code corresponding to the program to A Doppler frequency offset cancellation method for performing the OFDM system provided by the embodiments of the present application.

为达到上述目的，本申请实施例提供了一种存储介质，所述存储介质用于存储应用程序，所述应用程序用于执行本申请实施例所提供的OFDM系统中多普勒频偏消除方法。To achieve the above objective, an embodiment of the present application provides a storage medium, where the storage medium is used to execute an application, and the application is used to perform a Doppler frequency offset elimination method in an OFDM system provided by an embodiment of the present application. .

为达到上述目的，本申请实施例提供了一种应用程序，所述应用程序用于执行本申请实施例所提供的OFDM系统中多普勒频偏消除方法。To achieve the above objective, the embodiment of the present application provides an application program for performing a Doppler frequency offset elimination method in an OFDM system provided by an embodiment of the present application.

本申请实施例提供的OFDM系统中多普勒频偏估计方法及装置和消除方法及装置，选取至少三个预设循环前缀进行两两自相关得到自相关函数，并对所有的自相关函数求和后进行最大似然估计，得到起始多普勒频偏以及多普勒变化率，进而估算OFDM传播信号中随信号序列位置变化的目标多普勒频偏。The Doppler frequency offset estimation method and apparatus and the elimination method and apparatus in the OFDM system provided by the embodiments of the present application select at least three preset cyclic prefixes to perform autocorrelation functions for the two-two autocorrelation, and all the autocorrelation functions are obtained. After the maximum likelihood estimation, the initial Doppler frequency offset and the Doppler rate of change are obtained, and then the target Doppler frequency offset of the OFDM propagation signal with the positional change of the signal sequence is estimated.

与现有技术中，仅选取两个预设循环前缀进行自相关，进而获得多普勒频偏的方式相比，本申请实施例的方法采用了更多的预设循环前缀进行估算处理，减小了估算结果的误差，能很好的反应OFDM传播信号中多普勒频偏的实际大小，提高了估算结果的准确性。同时，发射端获得目标多普勒频偏后，对OFDM源信号进行多普勒频偏的反向处理时，可提高消除多普勒效应的效果。Compared with the prior art, only two preset cyclic prefixes are selected for autocorrelation, and then the Doppler frequency offset is obtained. Compared with the method for obtaining the Doppler frequency offset, the method in the embodiment of the present application uses more preset cyclic prefixes for estimation processing, and subtracts The error of the estimation result is small, which can well reflect the actual size of the Doppler frequency offset in the OFDM propagation signal, and improve the accuracy of the estimation result. At the same time, when the target end Doppler frequency offset is obtained at the transmitting end, the Doppler frequency effect can be improved by performing inverse processing of the Doppler frequency offset on the OFDM source signal.

DRAWINGS

为了更清楚地说明本申请实施例和现有技术的技术方案，下面对实施例和现有技术中所需要使用的附图作简单地介绍，显而易见地，下面描述中的附图仅仅是本申请的一些实施例，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据这些附图获得其他的附图。In order to more clearly illustrate the embodiments of the present application and the technical solutions of the prior art, the following description of the embodiments and the drawings used in the prior art will be briefly introduced. Obviously, the drawings in the following description are only Some embodiments of the application may also be used to obtain other figures from those of ordinary skill in the art without departing from the scope of the invention.

图1为本申请实施例提供的OFDM系统中多普勒频偏估计方法的第一种流程图；1 is a first flowchart of a Doppler frequency offset estimation method in an OFDM system according to an embodiment of the present application;

图2为本申请实施例提供的OFDM传播信号中第一个OFDM帧的示意图；2 is a schematic diagram of a first OFDM frame in an OFDM propagation signal according to an embodiment of the present disclosure;

图3为本申请实施例提供的OFDM系统中多普勒频偏估计方法的第二种流程图；FIG. 3 is a second flowchart of a Doppler frequency offset estimation method in an OFDM system according to an embodiment of the present disclosure;

图4为本申请实施例提供的OFDM系统中多普勒频偏消除方法的流程图；4 is a flowchart of a Doppler frequency offset cancellation method in an OFDM system according to an embodiment of the present disclosure;

图5为本申请实施例提供的OFDM系统中多普勒频偏估计装置第一种结构示意图； FIG. 5 is a schematic diagram of a first structure of a Doppler frequency offset estimation apparatus in an OFDM system according to an embodiment of the present disclosure;

图6为本申请实施例提供的OFDM系统中多普勒频偏估计装置第二种结构示意图；FIG. 6 is a schematic diagram of a second structure of a Doppler frequency offset estimation apparatus in an OFDM system according to an embodiment of the present disclosure;

图7为本申请实施例提供的OFDM系统中多普勒频偏消除装置的结构示意图。FIG. 7 is a schematic structural diagram of a Doppler frequency offset canceling apparatus in an OFDM system according to an embodiment of the present disclosure.

detailed description

下面将结合本申请实施例中的附图，对本申请实施例中的技术方案进行清楚、完整地描述，显然，所描述的实施例仅仅是本申请一部分实施例，而不是全部的实施例。基于本申请中的实施例，本领域普通技术人员在没有作出创造性劳动前提下所获得的所有其他实施例，都属于本申请保护的范围。The technical solutions in the embodiments of the present application are clearly and completely described in the following with reference to the drawings in the embodiments of the present application. It is obvious that the described embodiments are only a part of the embodiments of the present application, and not all of the embodiments. All other embodiments obtained by a person of ordinary skill in the art based on the embodiments of the present application without departing from the inventive scope are the scope of the present application.

为达到上述目的，本申请实施例提供了一种OFDM系统中多普勒频偏估计方法，图1为本申请实施例提供的OFDM系统中多普勒频偏估计方法的第一种流程图，该方法应用于接收端，其包括：To achieve the above objective, the embodiment of the present application provides a Doppler frequency offset estimation method in an OFDM system, and FIG. 1 is a first flowchart of a Doppler frequency offset estimation method in an OFDM system according to an embodiment of the present application. The method is applied to a receiving end, which includes:

S110，接收OFDM传播信号；所述OFDM传播信号中第一个OFDM帧中的第一个OFDM符号中包含Q个预设循环前缀；Q大于或等于3。S110. Receive an OFDM propagation signal. The first OFDM symbol in the first OFDM frame of the OFDM propagation signal includes Q preset cyclic prefixes; Q is greater than or equal to 3.

图2为本申请实施例提供的OFDM传播信号中第一个OFDM帧的示意图，为了估算OFDM传播信号中随信号序列位置变化的多普勒频偏，可预先设置发射端发送OFDM源信号的具体发射方式，该方式为：在发射OFDM源信号之前，重复发射Q(Q大于或等于3)次OFDM源信号中第一个OFDM帧中第一个OFDM符号中的循环前缀(即预设循环前缀)，之后，按照普通的方法发射OFDM源信号。2 is a schematic diagram of a first OFDM frame in an OFDM propagation signal according to an embodiment of the present disclosure. To estimate a Doppler frequency offset of a signal sequence change in an OFDM propagation signal, a specific manner of transmitting an OFDM source signal by a transmitting end may be preset. The transmission mode is: repeating the cyclic prefix (ie, the preset cyclic prefix) in the first OFDM symbol in the first OFDM frame of the Q (Q is greater than or equal to 3) OFDM source signals before transmitting the OFDM source signal. After that, the OFDM source signal is transmitted in accordance with an ordinary method.

如图2所示，按照上述发送方式发送OFDM源信号后，OFDM帧中总共有M个OFDM符号，其中第一个OFDM符号中多出了Q个预设循环前缀。该OFDM源信号在传播的过程中会受到多普勒效应的影响，产生OFDM传播信号。接收端接收到的OFDM传播信号与现有的OFDM传播信号的不同之处在于，该OFDM传播信号中第一个OFDM帧中的第一个OFDM符号中包含Q个预设循环前缀。As shown in FIG. 2, after transmitting the OFDM source signal according to the foregoing transmission manner, there are a total of M OFDM symbols in the OFDM frame, and Q preset cyclic prefixes are added in the first OFDM symbol. The OFDM source signal is affected by the Doppler effect during propagation, resulting in an OFDM propagation signal. The OFDM propagation signal received by the receiving end is different from the existing OFDM propagation signal in that the first OFDM symbol in the first OFDM frame of the OFDM propagation signal includes Q preset cyclic prefixes.

S120，对所有预设循环前缀进行两两自相关，得到多个自相关函数。S120: Perform two-two autocorrelation on all preset cyclic prefixes to obtain multiple autocorrelation functions.

S130，对所有自相关函数进行求和，得到概率密度函数。S130: sum all the autocorrelation functions to obtain a probability density function.

具体地，接收端在接收到Q个预设循环前缀后，会对各预设循环前缀的波形函数进行模数转换，得到Q个预设循环前缀对应的离散信号；之后，对所有的离散信号进行两两自相关，得到多个自相关函数。具体的，利用循环前缀得到自相关函数为现有技术，本申请实施例在此不对其进行赘述。举例而言，若Q＝3，则得到3个自相关函数。Specifically, after receiving the Q preset cyclic prefixes, the receiving end performs analog-to-digital conversion on the waveform functions of each preset cyclic prefix to obtain discrete signals corresponding to Q preset cyclic prefixes; and then, for all discrete signals Perform a two-two autocorrelation to get multiple autocorrelation functions. Specifically, using a cyclic prefix The autocorrelation function is obtained in the prior art, and the embodiments of the present application are not described herein. For example, if Q=3, then 3 autocorrelation functions are obtained.

具体地，接收端对获取的所有自相关函数进行求和，并将得到的结果确定为概率密度函数。Specifically, the receiving end sums all acquired autocorrelation functions and determines the obtained result as a probability density function.

S140，对所述概率密度函数进行最大似然估计，得到起始多普勒频偏和多普勒变化率。S140: Perform maximum likelihood estimation on the probability density function to obtain an initial Doppler frequency offset and a Doppler change rate.

其中，对所述概率密度函数进行最大似然估计得到的多普勒变化率为第一多普勒变化率。The Doppler change rate obtained by performing maximum likelihood estimation on the probability density function is a first Doppler change rate.

S150，根据所述起始多普勒频偏和所述多普勒变化率估算所述OFDM传播信号中第一个OFDM帧内随信号序列位置变化的目标多普勒频偏。S150. Estimate a target Doppler frequency offset of a signal sequence change in the first OFDM frame in the OFDM propagation signal according to the initial Doppler frequency offset and the Doppler change rate.

具体地，接收端在获取了概率密度函数之后，对其进行最大似然估计，得到起始多普勒频偏和多普勒变化率，其中，对概率密度函数进行最大似然估计为现有技术，本申请实施例在此不对其进行赘述。值得注意的是，本实施例中得到的起始多普勒频偏为OFDM传播信号中第一个OFDM帧中的第一个OFDM符号中第一个预设循环前缀的多普勒频偏，第一多普勒变化率为相邻两个预设循环前缀的多普勒频偏的差值。Specifically, after obtaining the probability density function, the receiving end performs maximum likelihood estimation to obtain a starting Doppler frequency offset and a Doppler rate of change, wherein the maximum likelihood estimation of the probability density function is existing. The embodiments of the present application are not described herein. It should be noted that the initial Doppler frequency offset obtained in this embodiment is the Doppler frequency offset of the first preset cyclic prefix in the first OFDM symbol in the first OFDM frame in the OFDM propagation signal. The first Doppler rate of change is the difference in Doppler shifts of two adjacent preset cyclic prefixes.

具体地，目标多普勒频偏为OFDM传播信号中第一个OFDM帧内随信号序列位置变化的多普勒频偏。在对目标多普勒频偏进行估算时，可将目标多普勒频偏看做是随信号序列位置线性变换的。举例而言，假设起始多普勒频偏为A，多普勒变化率为B,则第二个预设循环前缀的多普勒频偏为A+B，第三个预设循环前缀的多普勒频偏为A+2B，第Q个预设循环前缀的多普勒频偏为A+(Q-1)*B。Specifically, the target Doppler frequency offset is a Doppler frequency offset that varies with the position of the signal sequence in the first OFDM frame of the OFDM propagation signal. When estimating the target Doppler shift, the target Doppler shift can be regarded as linearly transformed with the position of the signal sequence. For example, if the initial Doppler frequency offset is A and the Doppler rate of change is B, then the Doppler frequency offset of the second preset cyclic prefix is A+B, and the third preset cyclic prefix is The Doppler frequency offset is A+2B, and the Doppler frequency offset of the Qth preset cyclic prefix is A+(Q-1)*B.

如图2所示，对于OFDM帧内第一个OFDM符号之后的其他OFDM符号，可按照预设循环前缀的时域宽度进行分段，得到每一分段的多普勒频偏。举例而言，图2中第一个OFDM符号中第Q个预设循环前缀后的信号是内容正文，假设该内容正文的时域宽度为预设循环前缀的时域宽度的10倍，则可将该内容正文平均分成10段，第一段内容正文对应的多普勒频偏为A+QB，第10段内容正文对应的多普勒频偏为A+(Q+9)B，以此类推。As shown in FIG. 2, for other OFDM symbols after the first OFDM symbol in the OFDM frame, segmentation may be performed according to the time domain width of the preset cyclic prefix to obtain a Doppler frequency offset of each segment. For example, the signal after the Qth preset cyclic prefix in the first OFDM symbol in FIG. 2 is the content body, and if the time domain width of the content body is 10 times the time domain width of the preset cyclic prefix, The content body is divided into 10 segments on average, the Doppler frequency offset corresponding to the content of the first paragraph is A+QB, the Doppler frequency offset corresponding to the content of the 10th paragraph is A+(Q+9)B, and so on. .

另外，在本申请的另一实施例中，每个OFDM帧都可以设置Q个预设循环前缀；具体的，由于不同的OFDM帧内的多普勒频偏的变化情况可能不同，接收端每接收到一个OFDM帧就会利用该帧内的Q个预设循环前缀计算一次起始多普勒频偏和第一多普勒变化率，这样可更加准确的描述每个OFDM帧内的目标多普勒频偏。In addition, in another embodiment of the present application, Q preset cyclic prefixes may be set for each OFDM frame; specifically, since the Doppler frequency offset in different OFDM frames may be different, the receiving end may each Receiving an OFDM frame will be calculated once using the Q preset cyclic prefixes in the frame. The initial Doppler shift and the first Doppler rate of change, which more accurately describe the target Doppler shift in each OFDM frame.

本申请实施例提供的OFDM系统中多普勒频偏估计方法，选取至少三个预设循环前缀进行两两自相关得到自相关函数，并对所有的自相关函数求和后进行最大似然估计，得到起始多普勒频偏以及第一多普勒变化率，进而估算OFDM传播信号中随信号序列位置变化的目标多普勒频偏。The Doppler frequency offset estimation method in the OFDM system provided by the embodiment of the present application selects at least three preset cyclic prefixes to perform autocorrelation functions by pairwise autocorrelation, and performs maximum likelihood estimation after summing all autocorrelation functions. The initial Doppler shift and the first Doppler rate of change are obtained, and then the target Doppler shift in the OFDM propagation signal as a function of the position of the signal sequence is estimated.

与现有技术中，仅选取两个预设循环前缀进行自相关，进而获得多普勒频偏的方式相比，本申请实施例的方法采用了更多的预设循环前缀进行估算处理，减小了估算结果的误差，能很好的反应OFDM传播信号中多普勒频偏的实际大小，提高了估算结果的准确性。Compared with the prior art, only two preset cyclic prefixes are selected for autocorrelation, and then the Doppler frequency offset is obtained. Compared with the method for obtaining the Doppler frequency offset, the method in the embodiment of the present application uses more preset cyclic prefixes for estimation processing, and subtracts The error of the estimation result is small, which can well reflect the actual size of the Doppler frequency offset in the OFDM propagation signal, and improve the accuracy of the estimation result.

图3为本申请实施例提供的OFDM系统中多普勒频偏估计方法的第二种流程图，该方法包括：FIG. 3 is a second flowchart of a Doppler frequency offset estimation method in an OFDM system according to an embodiment of the present disclosure, where the method includes:

S310，接收OFDM传播信号；所述OFDM传播信号中第一个OFDM帧中的第一个OFDM符号中包含Q个预设循环前缀；Q大于或等于3。S310. Receive an OFDM propagation signal. The first OFDM symbol in the first OFDM frame of the OFDM propagation signal includes Q preset cyclic prefixes; Q is greater than or equal to 3.

具体地，假设接收到的OFDM传播信号r[t]表示为Specifically, it is assumed that the received OFDM propagation signal r[t] is expressed as

其中，x[t]为OFDM源信号信号，z[t]为t时刻的背景噪声干扰，该背景噪声干扰可以看成均值为0的加性白高斯噪声。f_Doppler(τ)表示多普勒频偏，θ₀表示初始相位。Where x[t] is the OFDM source signal signal, and z[t] is the background noise interference at time t, which can be regarded as additive white Gaussian noise with a mean of zero. f _Doppler (τ) represents the Doppler shift, and θ ₀ represents the initial phase.

S320，对所有预设循环前缀进行采样，得到Q×L个分段信号；其中，各预设循环前缀的采样数量为L。S320. Sample all the preset cyclic prefixes to obtain Q×L segmentation signals. The number of samples of each preset cyclic prefix is L.

具体地，接收端接收到OFDM传播信号r[t]后，对每个预设循环前缀进行采样处理得到L个分段信号，共得到Q×L个分段信号，并对r[t]进行模数转换，得到第一个预设循环前缀中第n时刻的离散信号为：Specifically, after receiving the OFDM propagation signal r[t], the receiving end performs sampling processing on each preset cyclic prefix to obtain L segmentation signals, and obtains Q×L segmentation signals, and performs r[t] Analog-to-digital conversion, the discrete signal at the nth moment in the first preset cyclic prefix is:

其中，n＝kT_s，T_s为采样间隔，k＝0,1,…L-1，θ₀为初始相位，m为一个离散信号中的各个OFDM符号的标号。Where n = kT _s , T _s is the sampling interval, k = 0, 1, ... L-1, θ ₀ is the initial phase, and m is the label of each OFDM symbol in a discrete signal.

定义随信号序列位置变化的多普勒频偏为： Define the Doppler frequency offset as a function of the position of the signal sequence:

其中，

为分段信号空间，N为一个OFDM符号中分段信号的个数，因此公式(2)可以被重写为：among them,

For the segmented signal space, N is the number of segmented signals in one OFDM symbol, so equation (2) can be rewritten as:

尽管多普勒频偏在很长一段时域上非线性改变，但是在一个OFDM符号内，假设多普勒频偏线性改变是合乎情理的，因此有Although the Doppler shift is nonlinearly changed over a long period of time, it is reasonable to assume that the Doppler shift is linear in an OFDM symbol.

ε_k＝ε₀+αk (4)ε _k =ε ₀ +αk (4)

其中，

为第一多普勒变化率，ε₀为第一个预设循环前缀中第一个分段信号的多普勒频偏(即起始多普勒频偏)，同时Δf_Doppler为以H_z/s为单位的第二多普勒变化率，ε_k为OFDM传播信号中第一个OFDM帧内随信号序列位置变化的多普勒频偏；因此，公式(3)可变为：among them,

For the first Doppler rate of change, ε ₀ is the Doppler frequency offset of the first segmented signal in the first preset cyclic prefix (ie, the initial Doppler shift), and Δf _Doppler is H _z /s is the second Doppler rate of change, ε _k is the Doppler shift of the position of the signal sequence in the first OFDM frame of the OFDM propagation signal; therefore, equation (3) can be changed to:

S330，根据所述Q×L个分段信号对所有预设循环前缀进行两两自相关，得到多个自相关函数；其中，对任意两个预设循环前缀中第一预设循环前缀和第二预设循环前缀进行自相关得到L个自相关函数；所述对第一预设循环前缀和第二预设循环前缀进行自相关的方式包括：分别对所述第一预设循环前缀的第k个分段信号和所述第二预设循环前缀内的第k个分段信号进行自相关；k＝0,1,...L-1。S330, performing a pairwise autocorrelation on all preset cyclic prefixes according to the Q×L segmentation signals to obtain multiple autocorrelation functions; wherein, the first preset cyclic prefix and the first preset cyclic prefix in any two preset cyclic prefixes The two preset cyclic prefixes perform autocorrelation to obtain L autocorrelation functions; the manner of autocorrelation between the first preset cyclic prefix and the second preset cyclic prefix includes: respectively, the first preset cyclic prefix The k segment signals and the kth segment signal in the second preset cyclic prefix are autocorrelated; k=0, 1, . . . L-1.

具体地，根据接收到的一个完整的OFDM帧的分段信号来看，

为了不失一般性，定义n＝0作为OFDM帧的第一个分段信号，起始多普勒频偏ε₀以及多普勒变化率α会在接下来的部分通过最大似然估计算法进行描述并求解。Specifically, according to the segmentation signal of a complete OFDM frame received,

In order not to lose the generality, n=0 is defined as the first segmentation signal of the OFDM frame, and the initial Doppler frequency offset ε ₀ and the Doppler rate of change α are performed in the next part by the maximum likelihood estimation algorithm. Describe and solve.

另外，当N非常大时，发射端发射OFDM源信号的过程可以被看成是一个高斯过程，同时，由于OFDM源信号与噪声相互独立，接收端接收OFDM传播信号的过程也可以看成一个高斯过程，该过程可建模成一个如下的自相关函数。In addition, when N is very large, the process of transmitting the OFDM source signal at the transmitting end can be regarded as one. At the same time, since the OFDM source signal and the noise are independent of each other, the process of receiving the OFDM propagation signal at the receiving end can also be regarded as a Gaussian process, which can be modeled as an autocorrelation function as follows.

具体地，从Q个预设循环前缀中任意选择两个预设循环前缀，假设这两个预设循环前缀为第一预设循环前缀和第二预设循环前缀，第一预设循环前缀和第二预设循环前缀中分别包含L个分段信号，对第一预设循环前缀和第二预设循环前缀进行自相关得到L个自相关函数，其中，对第一预设循环前缀的第k个分段信号和第二预设循环前缀内的第k个分段信号进行自相关，得到的自相关函数为：Specifically, two preset cyclic prefixes are arbitrarily selected from the Q preset cyclic prefixes, and the two preset cyclic prefixes are assumed to be a first preset cyclic prefix and a second preset cyclic prefix, and the first preset cyclic prefix and The second preset cyclic prefix respectively includes L segmentation signals, and the first preset cyclic prefix and the second preset cyclic prefix are autocorrelated to obtain L autocorrelation functions, wherein the first preset cyclic prefix is The k segment signals and the kth segment signal in the second preset cyclic prefix are autocorrelated, and the obtained autocorrelation function is:

其中，m＝hL，h＝0,1,2,…Q-1，n∈I₀，I_i为第i个预设循环前缀的分段信号，I_i＝{iL,iL+1,…,iL+l-1}，i＝0,1,…Q-1，x[n+hL]＝x[n]，

为OFDM传播信号第n时刻的平均信号能量。当m＝0的时候，自相关函数的值为

为高斯白噪声的方差。Where m=hL, h=0,1,2,...Q-1,n∈I ₀ ,I _i is the segmentation signal of the ith preset cyclic prefix, I _i ={iL,iL+1,... , iL+l-1}, i=0,1,...Q-1,x[n+hL]=x[n],

The average signal energy at the nth moment of the signal propagation for OFDM. When m=0, the value of the autocorrelation function is

The variance of the white Gaussian noise.

需要说明的是，由于预设循环前缀对OFDM帧的同步性能影响程度较小，因此在自相关函数进行计算的过程中没有将预设循环前缀按一个OFDM符号进行处理，也就是计算时仅对M个OFDM符号进行处理，也使的分析过程更加直观。举例来说，假设一个OFDM帧内有1000个OFDM符号，有10个预设循环前缀，则在上述计算过程中M＝1000，而不是1010。It should be noted that, since the preset cyclic prefix has a small influence on the synchronization performance of the OFDM frame, the preset cyclic prefix is not processed by one OFDM symbol in the process of calculating the autocorrelation function, that is, only when calculating The processing of M OFDM symbols also makes the analysis process more intuitive. For example, if there are 1000 OFDM symbols in an OFDM frame and there are 10 preset cyclic prefixes, then M=1000 instead of 1010 in the above calculation process.

S340，对所有自相关函数进行求和，得到概率密度函数。S340, summing all autocorrelation functions to obtain a probability density function.

本实施例中，所有自相关函数包含所有预设循环前缀两两自相关得到的多组自相关函数，每组自相关函数包括L个自相关函数。举例而言，假设存在3个预设循环前缀，这3个预设循环前缀两两自相关得到的3组自相关函数，每组自相关函数包括L个自相关函数。In this embodiment, all autocorrelation functions include multiple sets of autocorrelation functions obtained by pairwise autocorrelation of all preset cyclic prefixes, and each set of autocorrelation functions includes L autocorrelation functions. For example, suppose there are 3 preset cyclic prefixes, 3 preset auto-correlation functions obtained by pairwise auto-correlation, and each set of autocorrelation functions includes L autocorrelation functions.

具体的，对所有自相关函数进行求和，得到的概率密度函数的计算公式可以表示为：Specifically, all autocorrelation functions are summed, and the obtained probability density function can be expressed as:

其中，

为概率密度函数。 among them,

For the probability density function.

S350，对所述概率密度函数进行最大似然估计，得到起始多普勒频偏和多普勒变化率。S350, performing maximum likelihood estimation on the probability density function to obtain an initial Doppler frequency offset and a Doppler change rate.

具体地，对概率密度函数

进行最大似然估计得到Specifically, the probability density function

Maximum likelihood estimation

其中，

n∈I_i，r[n]为高斯随机变量，

满足Q维高斯分布，

的概率密度函数可以表示为among them,

n∈I _i , r[n] is a Gaussian random variable,

Satisfy the Q-dimensional Gaussian distribution,

The probability density function can be expressed as

公式(9)中，H表示矩阵的共轭变换，K是一个Q×Q的相关矩阵，K的第(i,j)个元素满足E{y[n+iL]y^*[n+jL]},n∈I₀,i,j∈{0,1,2,…,Q-1}。In equation (9), H denotes the conjugate transformation of the matrix, K is a correlation matrix of Q × Q, and the (i, j)th element of K satisfies E{y[n+iL]y ^* [n+jL] },n∈I ₀ ,i,j∈{0,1,2,...,Q-1}.

考虑到式(8)的分母部分中的各项，这些项都满足一维高斯分布，概率密度函数可以进一步表示为Considering the items in the denominator part of equation (8), these terms satisfy the one-dimensional Gaussian distribution, and the probability density function can be further expressed as

把公式(10)带公式(8)中，同时把K的行列式带入公式(9)中，K的行列式为

然后省略掉相同部分∏(f(r[n]|ε₀,α))，最大似然估计的结果(ε₀,α)可以表示为：Put the formula (10) into the formula (8), and bring the determinant of K into the formula (9). The determinant of K is

Then the same part ∏(f(r[n]|ε ₀ , α)) is omitted, and the maximum likelihood estimation result (ε ₀ , α) can be expressed as:

对于公式(11)中出现的参数变量，其各自详细的表达式都可以在公式(12)到公式(14)中得到。For the parameter variables appearing in equation (11), their respective detailed expressions can be obtained in equations (12) through (14).

对于公式(14)中出现的参数变量，其各自详细的表达式都可以在公式(15)到公式(17)中得到。For the parameter variables appearing in equation (14), their respective detailed expressions can be obtained in equations (15) through (17).

在本实施例提供的最大似然估计中，公式(14)中关于{I_i,I_j}的自相关函数需要在求和之前进行β^-k,k＝{-(Q-1),…,-1,0,1,…，Q-1}的相位补偿，以便完成连续的求和。因此，β^-k针对不同的k值对自相关函数带来的是不同的相位旋转，防止像传统估计方法那样对多普勒频偏以及多普勒变化率进行简单独立的估计。In the maximum likelihood estimation provided in this embodiment, the autocorrelation function for {I _i , I _j } in equation (14) needs to perform β ^-k , k = {-(Q-1),... before summation. Phase compensation of -1, 0, 1, ..., Q-1} to complete the continuous summation. Therefore, β ^-k brings different phase rotations to the autocorrelation function for different k values, preventing simple independent estimation of Doppler frequency offset and Doppler rate of change like traditional estimation methods.

总之，一旦多普勒频偏的值是不准确的，那么最大似然估计的最佳效果将会通过大量的数值计算获得，极大增加了计算复杂度。因此，为了消除这种复杂度增大带来的计算负担，本实施例提出了一种近似最大似然估计方法，该近似最大似然估计方法如下：In short, once the value of the Doppler shift is inaccurate, the best effect of the maximum likelihood estimation will be obtained through a large number of numerical calculations, which greatly increases the computational complexity. Therefore, in order to eliminate the computational burden caused by such an increase in complexity, the present embodiment proposes an approximate maximum likelihood estimation method, and the approximate maximum likelihood estimation method is as follows:

针对公式(8)中Λ(ε₀,α)的表达式求多普勒频偏ε的一阶偏导数以及二阶偏导数，一阶偏导数得到的结果如公式(18)所示： For the expression of Λ(ε ₀ , α) in the formula (8), the first-order partial derivative of the Doppler frequency offset ε and the second-order partial derivative are obtained. The result of the first-order partial derivative is as shown in the formula (18):

二阶偏导数得到的结果如公式(19)所示：The result obtained by the second-order partial derivative is as shown in equation (19):

既然正确的多普勒频偏值在没有噪声的情况下对于多普勒变化率的值满足∠Ψ_k(α)＝-2πεk/Q，那么就可以假设一般情况下∠Ψ_k(α)≈-2πεk/Q，除非遇到极低信噪比的情况。因此也就自然而然能够得到cos(∠Ψ_k(α)+2πεk/Q)≈1(>>0)，这种估计对于信噪比的一般情况是很准确的。Since the correct Doppler shift value satisfies ∠Ψ _k (α)=-2πεk/Q in the absence of noise for the Doppler rate of change, then it can be assumed that ∠Ψ _k (α)≈ in general -2πεk/Q unless a very low signal to noise ratio is encountered. Therefore, it is natural to obtain cos(∠Ψ _k (α)+2πεk/Q)≈1(>>0). This estimation is very accurate for the general case of signal-to-noise ratio.

以上也能够说明在ε＝-Q∠Ψ_k(α)/2πk的频偏范围之内，一阶偏导数

满足单调递减，二阶偏导数满足

的情况。因此，Λ(ε₀,α)关于多普勒频偏ε的最大值将会在

得到。再利用sin x≈x,|x|<<1，公式(17)将会得到以下表达式(20)：The above can also explain the first-order partial derivative within the frequency offset range of ε=-Q∠Ψ _k (α)/2πk

Satisfying monotonic decline, second-order partial derivatives satisfy

Case. Therefore, the maximum value of Λ(ε ₀ , α) with respect to the Doppler shift ε will be

get. Reusing sin x≈x, |x|<<1, equation (17) will result in the following expression (20):

对于以第一多普勒变化率为参数，起始多普勒频偏的估计值ε₀(α)可以表示为：For the first Doppler rate of change parameter, the estimated value of the initial Doppler shift ε ₀ (α) can be expressed as:

将ε₀(α)和β^-k代入至公式(14)中，进而能够得到第一多普勒变化率的估计值，其表达式如(22)所示：Substituting ε ₀ (α) and β ^-k into equation (14), an estimate of the first Doppler rate of change can be obtained, the expression of which is shown in (22):

在本实施例中，当第一多普勒变化率的值为给定的已知值的情况下，那么起始多普勒频偏的值就是唯一确定的，其计算复杂度相对于通过逐步搜索进行最大似然估计，起始多普勒频偏的值以及第一多普勒变化率的值降低了 Q-1倍。In this embodiment, when the value of the first Doppler change rate is a given known value, then the value of the initial Doppler shift is uniquely determined, and the computational complexity is relatively Search for maximum likelihood estimation, the value of the initial Doppler shift and the value of the first Doppler rate of change are reduced Q-1 times.

S360，根据所述起始多普勒频偏和所述多普勒变化率估算所述OFDM传播信号中第一个OFDM帧内随信号序列位置变化的目标多普勒频偏。S360. Estimate a target Doppler frequency offset of a signal sequence change in the first OFDM frame in the OFDM propagation signal according to the initial Doppler frequency offset and the Doppler change rate.

其中，该多普勒变化率为第一多普勒变化率。Wherein, the Doppler change rate is the first Doppler change rate.

具体地，根据公式(8)计算得到的起始多普勒频偏和第一多普勒变化率后，可根据公式ε_k＝ε₀+αk，估算OFDM传播信号中第一个OFDM帧内随信号序列位置变化的目标多普勒频偏，其中，ε_k为目标多普勒频偏。Specifically, after the initial Doppler frequency offset and the first Doppler rate of change calculated according to formula (8), the first OFDM frame in the OFDM propagation signal can be estimated according to the formula ε _k = ε ₀ + αk The target Doppler shift with the position of the signal sequence, where ε _k is the target Doppler shift.

值得注意的是，本实施例中的起始多普勒频偏ε₀为OFDM传播信号中第一个OFDM帧中第一个OFDM符号中第一个预设循环前缀中第一个分段信号的多普勒频偏，α为相邻两个分段信号的多普勒频偏的差(即第一多普勒变化率)，利用ε₀和α估算的目标多普勒频偏ε_k，在描述OFDM传播信号中多普勒频偏的实际大小时，比上述第一种实施例中的目标多普勒频偏准确性更高。It should be noted that the initial Doppler frequency offset ε ₀ in this embodiment is the first segment signal in the first preset cyclic prefix in the first OFDM symbol in the first OFDM frame in the OFDM propagation signal. Doppler frequency offset, α is the difference of the Doppler frequency offset of the adjacent two segmented signals (ie, the first Doppler rate of change), and the target Doppler frequency offset ε _k estimated by ε ₀ and α When describing the actual size of the Doppler shift in the OFDM propagation signal, the target Doppler frequency offset accuracy is higher than that in the first embodiment described above.

本申请实施例还提供了一种OFDM系统中多普勒频偏消除方法，图4为本申请实施例提供的OFDM系统中多普勒频偏消除方法的流程图，应用于发射端，该方法包括：The embodiment of the present application further provides a Doppler frequency offset cancellation method in an OFDM system, and FIG. 4 is a flowchart of a Doppler frequency offset cancellation method in an OFDM system according to an embodiment of the present application, which is applied to a transmitting end, and the method is include:

S410，接收接收端发送的目标多普勒频偏。S410. Receive a target Doppler frequency offset sent by the receiving end.

具体地，接收端生成目标多普勒频偏后，将其发送给发射端，发射端接收目标多普勒频偏。本实施例中，目标多普勒频偏可以是接收端按照本申请实施例提供的OFDM系统中多普勒频偏估计方法估算得到的。Specifically, after the target end generates the target Doppler frequency offset, it sends the target Doppler frequency offset to the transmitting end, and the transmitting end receives the target Doppler frequency offset. In this embodiment, the target Doppler frequency offset may be estimated by the receiving end according to the Doppler frequency offset estimation method in the OFDM system provided by the embodiment of the present application.

S420，根据所述目标多普勒频偏，对待发射的OFDM源信号进行多普勒频偏反向处理，获得目标OFDM源信号。S420: Perform Doppler frequency offset processing on the OFDM source signal to be transmitted according to the target Doppler frequency offset, to obtain a target OFDM source signal.

S430，发送所述目标OFDM源信号。S430. Send the target OFDM source signal.

具体地，发射端接收到目标多普勒频偏后，对待发射的OFDM源信号进行多普勒频偏反向处理(即使OFDM源信号受到反向目标多普勒频偏的影响)，得到目标OFDM源信号。然后发射目标OFDM源信号，目标OFDM源信号在传播的过程中再次受到目标多普勒频偏的影响，两次目标多普勒频偏相互抵消，接收端可接收到OFDM源信号，因此该方法减小了多普勒效应对OFDM源信号的影响。Specifically, after receiving the target Doppler frequency offset, the transmitting end performs Doppler frequency offset processing on the OFDM source signal to be transmitted (even if the OFDM source signal is affected by the reverse target Doppler frequency offset), and obtains the target. OFDM source signal. Then, the target OFDM source signal is transmitted, and the target OFDM source signal is again affected by the target Doppler frequency offset in the process of propagation, the two target Doppler frequency offsets cancel each other, and the receiving end can receive the OFDM source signal, so the method The influence of the Doppler effect on the OFDM source signal is reduced.

值得注意的是，如果目标多普勒频偏是按照本申请图1所示实施例提供的OFDM系统中多普勒频偏估计方法估算得到的，由于该目标多普勒频偏是由OFDM传播信号中第一个OFDM帧中的第一个OFDM符号中第一个完整的预设循环前缀的多普勒频偏和相邻两个预设循环前缀的多普勒频偏的差值进行估算得到的，那么发射端在对OFDM源信号进行目标多普勒频率补偿时，需要对一个一个完整的预设循环前缀进行多普勒频偏的反向处理。虽然该处理方式与现有的处理方式相同，但由于计算得到的目标多普勒频偏比现有的较为准确，最后得到OFDM源信号，在消除OFDM源信号的多普勒效应时，比现有的方式效果更好。It should be noted that if the target Doppler frequency offset is estimated according to the Doppler frequency offset estimation method in the OFDM system provided by the embodiment shown in FIG. 1 of the present application, since the target Doppler frequency offset is propagated by OFDM The first complete in the first OFDM symbol in the first OFDM frame in the signal Estimating the difference between the Doppler frequency offset of the preset cyclic prefix and the Doppler frequency offset of two adjacent cyclic prefixes, then the transmitting end performs the target Doppler frequency compensation on the OFDM source signal. It is necessary to perform reverse processing of Doppler shift on a complete preset cyclic prefix. Although the processing method is the same as the existing processing method, since the calculated target Doppler frequency offset is more accurate than the existing one, the OFDM source signal is finally obtained, and when the Doppler effect of the OFDM source signal is eliminated, the ratio is Some ways work better.

如果目标多普勒频偏是按照本申请图3所示实施例提供的OFDM系统中多普勒频偏估计方法估算得到的，由于该目标多普勒频偏是由OFDM传播信号中第一个OFDM帧中第一个OFDM符号中第一个预设循环前缀中第一个分段信号的多普勒频偏和相邻两个分段信号的多普勒频偏的差值进行估算得到的，那么发射端在对OFDM源信号进行多普勒频偏的反向处理时，需要对一个一个分段信号进行多普勒频偏的反向处理，第二种处理方式与第一种处理方式相比，在消除OFDM源信号的多普勒效应时，效果更佳。If the target Doppler frequency offset is estimated according to the Doppler frequency offset estimation method in the OFDM system provided by the embodiment shown in FIG. 3 of the present application, since the target Doppler frequency offset is the first one of the OFDM propagation signals Estimating the difference between the Doppler frequency offset of the first segmented signal and the Doppler shift of the adjacent two segmented signals in the first preset cyclic prefix in the first OFDM symbol in the OFDM frame Then, when the transmitting end performs the inverse processing of the Doppler frequency offset on the OFDM source signal, it is necessary to perform reverse processing of Doppler frequency offset on one segmented signal, and the second processing method and the first processing method In comparison, the effect is better when the Doppler effect of the OFDM source signal is eliminated.

本申请实施例还提供了一种OFDM系统中多普勒频偏估计装置。图5为本申请实施例提供的OFDM系统中多普勒频偏估计装置第一种结构示意图，用于执行图1所示的方法，所示装置应用于接收端，其包括：The embodiment of the present application further provides a Doppler frequency offset estimation apparatus in an OFDM system. FIG. 5 is a schematic diagram of a first structure of a Doppler frequency offset estimation apparatus in an OFDM system according to an embodiment of the present disclosure, where the apparatus shown in FIG. 1 is applied to a receiving end, which includes:

接收模块510，用于接收OFDM传播信号；所述OFDM传播信号中第一个OFDM帧中的第一个OFDM符号中包含Q个预设循环前缀；Q大于或等于3；The receiving module 510 is configured to receive an OFDM propagation signal; the first OFDM symbol in the first OFDM frame of the OFDM propagation signal includes Q preset cyclic prefixes; Q is greater than or equal to 3;

自相关模块520，用于对所有预设循环前缀进行两两自相关，得到多个自相关函数；The auto-correlation module 520 is configured to perform a pairwise autocorrelation on all preset cyclic prefixes to obtain a plurality of autocorrelation functions;

求和模块530，用于对所有自相关函数进行求和，得到概率密度函数；a summation module 530 for summing all autocorrelation functions to obtain a probability density function;

最大似然估计模块540，用于对所述概率密度函数进行最大似然估计，得到起始多普勒频偏和第一多普勒变化率；a maximum likelihood estimation module 540, configured to perform maximum likelihood estimation on the probability density function to obtain an initial Doppler frequency offset and a first Doppler rate of change;

估算模块550，用于根据所述起始多普勒频偏和所述第一多普勒变化率估算所述OFDM传播信号中第一个OFDM帧内随信号序列位置变化的目标多普勒频偏。An estimation module 550, configured to estimate, according to the initial Doppler frequency offset and the first Doppler rate of change, a target Doppler frequency of a signal sequence change in a first OFDM frame in the OFDM propagation signal. Partial.

本申请实施例提供的OFDM系统中多普勒频偏估计装置，现选取至少三个预设循环前缀进行两两自相关得到自相关函数，并对所有的自相关函数求和后进行最大似然估计，得到起始多普勒频偏以及多普勒变化率，进而估算OFDM传播信号中随信号序列位置变化的目标多普勒频偏。The Doppler frequency offset estimation apparatus in the OFDM system provided by the embodiment of the present application selects at least three preset cyclic prefixes to perform autocorrelation function for two-two autocorrelation, and performs maximum likelihood after summing all autocorrelation functions. It is estimated that the initial Doppler shift and the Doppler rate of change are obtained, and then the target Doppler shift in the OFDM propagation signal as a function of the position of the signal sequence is estimated.

与现有技术中，仅选取两个预设循环前缀进行自相关，进而获得多普勒频偏的方式相比，本申请实施例的方法采用了更多的预设循环前缀进行估算处理，减小了估算结果的误差，能很好的反应OFDM传播信号中多普勒频偏的实际大小，提高了估算结果的准确性。In the prior art, only two preset cyclic prefixes are selected for autocorrelation, thereby obtaining Doppler. Compared with the frequency offset mode, the method in the embodiment of the present application adopts more preset cyclic prefixes for estimation processing, reduces the error of the estimation result, and can well reflect the actual Doppler frequency offset in the OFDM propagation signal. Size increases the accuracy of the estimates.

图6为本申请实施例提供的OFDM系统中多普勒频偏估计装置第二种结构示意图，用于执行图3所示的方法，与图5不同之处在于，所述自相关模块520，包括：FIG. 6 is a schematic diagram of a second structure of a Doppler frequency offset estimation apparatus in an OFDM system according to an embodiment of the present disclosure, for performing the method shown in FIG. 3, which is different from FIG. 5 in that the autocorrelation module 520, include:

采样单元521，用于对所有预设循环前缀进行采样，得到Q×L个分段信号；其中，各预设循环前缀的采样数量为L；The sampling unit 521 is configured to sample all the preset cyclic prefixes to obtain Q×L segmentation signals; wherein, the sampling number of each preset cyclic prefix is L;

自相关单元522，用于根据所述Q×L个分段信号对所有预设循环前缀进行两两自相关，得到多个自相关函数；其中，对任意两个预设循环前缀中第一预设循环前缀和第二预设循环前缀进行自相关得到L个自相关函数；所述对第一预设循环前缀和第二预设循环前缀进行自相关的方式包括：分别对所述第一预设循环前缀的第k个分段信号和所述第二预设循环前缀内的第k个分段信号进行自相关；k＝0,1,...L-1。The auto-correlation unit 522 is configured to perform a pairwise autocorrelation on all preset cyclic prefixes according to the Q×L segmentation signals to obtain multiple autocorrelation functions; wherein, the first pre-prefix in any two preset cyclic prefixes Setting a cyclic prefix and a second preset cyclic prefix to perform autocorrelation to obtain L autocorrelation functions; the manner of performing autocorrelation on the first preset cyclic prefix and the second preset cyclic prefix includes: separately performing the first pre- The k-th segment signal of the cyclic prefix and the k-th segment signal in the second preset cyclic prefix are autocorrelated; k=0, 1, . . . L-1.

其中，所述自相关函数的计算公式为：Wherein, the calculation formula of the autocorrelation function is:

表示的是分段信号空间，N为一个OFDM符号中分段信号的个数。n∈I₀，I_i为第i个预设循环前缀的分段信号，I_i＝{iL,iL+1,…,iL+l-1}，i＝0,1,…Q-1。Where m = hL, h = 1, 2, 3, ... Q-1, n = kT _s , T _s is the sampling interval, r [n] is the first of the first OFDM frames in the OFDM propagation signal The waveform function at the nth time in the first preset cyclic prefix in the OFDM symbol,

Indicated is the segmented signal space, where N is the number of segmented signals in one OFDM symbol. n ∈ I ₀ , I _i is the segmentation signal of the ith preset cyclic prefix, I _i = {iL, iL+1, ..., iL + l-1}, i = 0, 1, ... Q-1.

其中，所述概率密度函数的计算公式为： Wherein, the calculation formula of the probability density function is:

其中，

为所述概率密度函数。among them,

Is the probability density function.

其中，所述最大似然估计模块540具体用于：The maximum likelihood estimation module 540 is specifically configured to:

根据公式According to the formula

本实施例提供的OFDM系统中多普勒频偏估计装置估算得到的目标多普勒频偏，在描述OFDM传播信号中多普勒频偏的实际大小时，准确性更高。The target Doppler frequency offset estimated by the Doppler frequency offset estimation apparatus in the OFDM system provided by this embodiment provides higher accuracy when describing the actual size of the Doppler frequency offset in the OFDM propagation signal.

本申请实施例还提供了一种OFDM系统中多普勒频偏消除装置，图7为本申请实施例提供的OFDM系统中多普勒频偏消除装置的结构示意图，应用于发射端，用于执行图4所示的方法，该装置包括：The embodiment of the present application further provides a Doppler frequency offset canceling apparatus in an OFDM system, and FIG. 7 is a schematic structural diagram of a Doppler frequency offset canceling apparatus in an OFDM system according to an embodiment of the present application, which is applied to a transmitting end, and is used in Performing the method illustrated in Figure 4, the apparatus includes:

接收模块710，用于接收接收端发送的目标多普勒频偏；所述目标多普勒频偏为接收端根据上述OFDM系统中多普勒频偏估计装置估算得到的；The receiving module 710 is configured to receive a target Doppler frequency offset sent by the receiving end, where the target Doppler frequency offset is estimated by the receiving end according to the Doppler frequency offset estimating apparatus in the OFDM system;

反向处理模块720，用于根据所述目标多普勒频偏，对待发射的OFDM源信号进行多普勒频偏反向处理，获得目标OFDM源信号；The inverse processing module 720 is configured to perform Doppler frequency offset processing on the OFDM source signal to be transmitted according to the target Doppler frequency offset, to obtain a target OFDM source signal;

发送模块730，用于发送所述目标OFDM源信号。The sending module 730 is configured to send the target OFDM source signal.

本申请实施例提供的OFDM系统中多普勒频偏消除装置，对OFDM源信号进行多普勒频偏反向处理时，可提高消除多普勒效应的效果。The Doppler frequency offset canceling apparatus in the OFDM system provided by the embodiment of the present application can improve the effect of eliminating the Doppler effect when Doppler frequency offset processing is performed on the OFDM source signal.

本申请实施例还提供了一种接收端，所述接收端包括：壳体、处理器、存储器、电路板和电源电路，其中，电路板安置在壳体围成的空间内部，处理器和存储器设置在电路板上；电源电路，用于为接收端的各个电路或器件供电；存储器用于存储可执行程序代码；处理器通过读取存储器中存储的可执行程序代码来运行与可执行程序代码对应的应用程序，以用于执行本申请实施例所提供的OFDM系统中多普勒频偏估计方法，其中，本申请实施例所提供的OFDM系统中多普勒频偏估计方法，可以包括：The embodiment of the present application further provides a receiving end, the receiving end includes: a housing, a processor, a memory, a circuit board, and a power supply circuit, wherein the circuit board is disposed inside the space enclosed by the housing, the processor and the memory Provided on a circuit board; a power supply circuit for supplying power to each circuit or device at the receiving end; a memory for storing executable program code; and a processor for operating the executable program code by reading executable program code stored in the memory The method for performing the Doppler frequency offset estimation method in the OFDM system provided by the embodiment of the present application, wherein the Doppler frequency offset estimation method in the OFDM system provided by the embodiment of the present application may include:

对所有预设循环前缀进行两两自相关，得到多个自相关函数； Performing two-two autocorrelation on all preset cyclic prefixes to obtain multiple autocorrelation functions;

根据所述起始多普勒频偏和所述第一多普勒变化率估算所述OFDM传播信号中第一个OFDM帧内随信号序列位置变化的目标多普勒频偏。And estimating a target Doppler frequency offset of the signal sequence position change in the first OFDM frame in the OFDM propagation signal according to the initial Doppler frequency offset and the first Doppler change rate.

其中，所述对所有预设循环前缀进行两两自相关，得到多个自相关函数的步骤，包括：The step of performing a two-two autocorrelation on all preset cyclic prefixes to obtain multiple autocorrelation functions includes:

其中，

为所述概率密度函数。among them,

Is the probability density function.

其中，所述对所述概率密度函数进行最大似然估计，得到起始多普勒频偏和第一多普勒变化率的步骤，包括：The step of performing maximum likelihood estimation on the probability density function to obtain a starting Doppler frequency offset and a first Doppler rate of change, including:

根据公式According to the formula

其中，所述根据所述起始多普勒频偏和所述第一多普勒变化率估算所述OFDM传播信号中随信号序列位置变化的目标多普勒频偏的步骤，包括：The step of estimating a target Doppler frequency offset of the OFDM propagation signal according to the position of the signal sequence according to the initial Doppler frequency offset and the first Doppler rate of change, including:

另外，本申请实施例还提供了一种存储介质，用于存储应用程序，所述应用程序用于执行本申请实施例所提供的OFDM系统中多普勒频偏估计方法，其中，本申请实施例所提供的OFDM系统中多普勒频偏估计方法，可以包括：In addition, the embodiment of the present application further provides a storage medium for storing an application, where the application is used to perform a Doppler frequency offset estimation method in an OFDM system provided by an embodiment of the present application, where The Doppler frequency offset estimation method in the OFDM system provided by the example may include:

根据所述Q×L个分段信号对所有预设循环前缀进行两两自相关，得到多个自相关函数；其中，对任意两个预设循环前缀第一预设循环前缀和第二预设循环前缀进行自相关得到L个自相关函数；所述对第一预设循环前缀和第二预设循环前缀进行自相关的方式包括：分别对所述第一预设循环前缀的第k个分段信号和所述第二预设循环前缀内的第k个分段信号进行自相关；k＝0,1,...L-1。Performing a pairwise autocorrelation on all preset cyclic prefixes according to the Q×L segmentation signals to obtain multiple autocorrelation functions; wherein, the first preset cyclic prefix and the second pre-prefix for any two preset cyclic prefixes The loop prefix is used for autocorrelation to obtain L autocorrelation functions; the manner of autocorrelation between the first preset cyclic prefix and the second preset cyclic prefix includes: respectively, the kth of the first preset cyclic prefix The segmentation signal and the kth segmentation signal in the second preset cyclic prefix are autocorrelated; k=0, 1, . . . L-1.

其中，所述概率密度函数的计算公式为：Wherein, the calculation formula of the probability density function is:

其中，

为所述概率密度函数。among them,

Is the probability density function.

根据公式According to the formula

其中，所述根据所述起始多普勒频偏和所述第一多普勒变化率估算所述 OFDM传播信号中随信号序列位置变化的目标多普勒频偏的步骤，包括：Wherein the estimating the initial Doppler shift and the first Doppler rate of change The steps of the target Doppler shift in the OFDM propagation signal as the position of the signal sequence changes, including:

另外，本申请实施例还提供了一种应用程序，用于执行本申请实施例所提供的OFDM系统中多普勒频偏估计方法，其中，本申请实施例所提供的OFDM系统中多普勒频偏估计方法，可以包括：In addition, the embodiment of the present application further provides an application program for performing the Doppler frequency offset estimation method in the OFDM system provided by the embodiment of the present application, where the Doppler in the OFDM system provided by the embodiment of the present application is provided. The frequency offset estimation method may include:

其中，m＝hL，h＝1,2,3,…Q-1，n＝kT_s，T_s为采样间隔，r[n]为所述OFDM传播信号中第一个OFDM帧中第一个OFDM符号中第一个预设循环前缀中第n 时刻的波形函数，

表示的是分段信号空间，N为一个OFDM符号中分段信号的个数，n∈I₀，I_i为第i个预设循环前缀的分段信号，I_i＝{iL,iL+1,…,iL+l-1}，i＝0,1,…Q-1。Where m = hL, h = 1, 2, 3, ... Q-1, n = kT _s , T _s is the sampling interval, r [n] is the first of the first OFDM frames in the OFDM propagation signal The waveform function at the nth moment in the first preset cyclic prefix in the OFDM symbol,

其中，

为所述概率密度函数。among them,

Is the probability density function.

根据公式According to the formula

本申请实施例还提供了一种发射端，所述发射端包括：壳体、处理器、存储器、电路板和电源电路，其中，电路板安置在壳体围成的空间内部，处理器和存储器设置在电路板上；电源电路，用于为发射端的各个电路或器件供电；存储器用于存储可执行程序代码；处理器通过读取存储器中存储的可执行程序代码来运行与可执行程序代码对应的应用程序，以用于执行本申请实施例所提供的OFDM系统中多普勒频偏消除方法，其中，本申请实施例所提供的OFDM系统中多普勒频偏消除方法，可以包括： The embodiment of the present application further provides a transmitting end, the transmitting end includes: a housing, a processor, a memory, a circuit board, and a power supply circuit, wherein the circuit board is disposed inside the space enclosed by the housing, the processor and the memory Provided on a circuit board; a power supply circuit for supplying power to each circuit or device at the transmitting end; a memory for storing executable program code; and a processor for operating the executable program code by reading executable program code stored in the memory The method for performing the Doppler frequency offset cancellation method in the OFDM system provided by the embodiment of the present application, wherein the Doppler frequency offset cancellation method in the OFDM system provided by the embodiment of the present application may include:

接收接收端发送的目标多普勒频偏；所述目标多普勒频偏为接收端根据本申请实施例提供的OFDM系统中多普勒频偏估计方法估算得到的；Receiving a target Doppler frequency offset sent by the receiving end; the target Doppler frequency offset is estimated by the receiving end according to the Doppler frequency offset estimation method in the OFDM system provided by the embodiment of the present application;

发送所述目标OFDM源信号。Transmitting the target OFDM source signal.

另外，本申请实施例还提供了一种存储介质，用于存储应用程序，所述应用程序用于执行本申请实施例所提供的OFDM系统中多普勒频偏消除方法，其中，本申请实施例所提供的OFDM系统中多普勒频偏消除方法，可以包括：In addition, the embodiment of the present application further provides a storage medium for storing an application, where the application is used to perform a Doppler frequency offset elimination method in an OFDM system provided by an embodiment of the present application, where The Doppler frequency offset elimination method in the OFDM system provided by the example may include:

发送所述目标OFDM源信号。Transmitting the target OFDM source signal.

另外，本申请实施例还提供了一种应用程序，用于执行本申请实施例所提供的OFDM系统中多普勒频偏消除方法，其中，本申请实施例所提供的OFDM系统中多普勒频偏消除方法，可以包括：In addition, the embodiment of the present application further provides an application for performing the Doppler frequency offset cancellation method in the OFDM system provided by the embodiment of the present application, where the Doppler in the OFDM system provided by the embodiment of the present application is provided. The frequency offset elimination method may include:

发送所述目标OFDM源信号。Transmitting the target OFDM source signal.

需要说明的是，在本文中，诸如第一和第二等之类的关系术语仅仅用来将一个实体或者操作与另一个实体或操作区分开来，而不一定要求或者暗示这些实体或操作之间存在任何这种实际的关系或者顺序。而且，术语“包括”、“包含”或者其任何其他变体意在涵盖非排他性的包含，从而使得包括一系列要素的过程、方法、物品或者设备不仅包括那些要素，而且还包括没有明确列出的其他要素，或者是还包括为这种过程、方法、物品或者设备所固有的要素。在没有更多限制的情况下，由语句“包括一个……”限定的要素，并不排除在包括所述要素的过程、方法、物品或者设备中还存在另外的相同要素。It should be noted that, in this context, relational terms such as first and second are used merely to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply such entities or operations. There is any such actual relationship or order between them. Furthermore, the term "comprises" or "comprises" or "comprises" or any other variations thereof is intended to encompass a non-exclusive inclusion, such that a process, method, article, or device that comprises a plurality of elements includes not only those elements but also Other elements, or elements that are inherent to such a process, method, item, or device. An element that is defined by the phrase "comprising a ..." does not exclude the presence of additional equivalent elements in the process, method, item, or device that comprises the element.

本说明书中的各个实施例均采用相关的方式描述，各个实施例之间相同相似的部分互相参见即可，每个实施例重点说明的都是与其他实施例的不同之处。尤其，对于装置实施例而言，由于其基本相似于方法实施例，所以描述的比较简单，相关之处参见方法实施例的部分说明即可。The various embodiments in the specification are described in a related manner, and the same similar parts between the various embodiments may be referred to each other, and each embodiment focuses on the differences from other embodiments. Where. In particular, for the device embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can be referred to the description of the method embodiment.

本领域普通技术人员可以理解实现上述方法实施方式中的全部或部分步骤是可以通过程序来指令相关的硬件来完成，所述的程序可以存储于计算机可读取存储介质中，这里所称得的存储介质，如：ROM/RAM、磁碟、光盘等。One of ordinary skill in the art can understand that all or part of the steps in implementing the above method embodiments can be completed by a program to instruct related hardware, and the program can be stored in a computer readable storage medium, which is referred to herein. Storage media such as ROM/RAM, disk, CD, etc.

以上所述仅为本申请的较佳实施例而已，并非用于限定本申请的保护范围。凡在本申请的精神和原则之内所作的任何修改、等同替换、改进等，均包含在本申请的保护范围内。 The above description is only the preferred embodiment of the present application, and is not intended to limit the scope of the present application. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application are included in the scope of the present application.

Claims

A Doppler frequency offset estimation method in an OFDM system, which is characterized in that it is applied to a receiving end, and the method includes:

Receiving an OFDM propagation signal; the first OFDM symbol in the first OFDM frame of the OFDM propagation signal includes Q preset cyclic prefixes; Q is greater than or equal to 3;

Performing two-two autocorrelation on all preset cyclic prefixes to obtain multiple autocorrelation functions;

Summing all autocorrelation functions to obtain a probability density function;

Performing maximum likelihood estimation on the probability density function to obtain an initial Doppler frequency offset and a first Doppler rate of change;

And estimating a target Doppler frequency offset of the signal sequence position change in the first OFDM frame in the OFDM propagation signal according to the initial Doppler frequency offset and the first Doppler change rate.

The method according to claim 1, wherein the step of performing a pairwise autocorrelation on all preset cyclic prefixes to obtain a plurality of autocorrelation functions comprises:

Sampling all the preset cyclic prefixes to obtain Q×L segmentation signals; wherein, the sampling number of each preset cyclic prefix is L;

Performing two-two autocorrelation on all preset cyclic prefixes according to the Q×L segmentation signals to obtain multiple autocorrelation functions; wherein, for any two preset cyclic prefixes, the first preset cyclic prefix and the second preset The cyclic prefix performs autocorrelation to obtain L autocorrelation functions; the manner of autocorrelation between the first preset cyclic prefix and the second preset cyclic prefix includes: respectively, the kth sub-division of the first preset cyclic prefix The segment signal and the kth segment signal in the second preset cyclic prefix are autocorrelated; k=0, 1, . . . L-1.

The method according to claim 2, wherein the calculation formula of the autocorrelation function is:

Where m = hL, h = 1, 2, 3, ... Q-1, n = kT _s , T _s is the sampling interval, r [n] is the first of the first OFDM frames in the OFDM propagation signal The waveform function at the nth time in the first preset cyclic prefix in the OFDM symbol,

The method of claim 3 wherein the probability density function is calculated as:

among them,

Is the probability density function.

The method according to claim 4, wherein said step of performing maximum likelihood estimation on said probability density function to obtain a starting Doppler shift and a first Doppler rate of change comprises:

According to the formula

Calculating the initial Doppler shift and the first Doppler rate of change to obtain the initial Doppler shift and the first Doppler rate of change.

The method according to claim 5, wherein said estimating a target of a change in position of said signal sequence in said OFDM propagation signal based on said initial Doppler frequency offset and said first Doppler rate of change The steps of Pule's frequency offset include:

Estimating the target Doppler frequency offset according to the formula ε _k = ε ₀ + αk;

Where ε _k is the target Doppler shift.

A Doppler frequency offset elimination method in an OFDM system, which is characterized in that it is applied to a transmitting end, and the method includes:

Receiving a target Doppler frequency offset sent by the receiving end; the target Doppler frequency offset is estimated by the receiving end according to the Doppler frequency offset estimation method in the OFDM system according to any one of claims 1-6;

Performing Doppler frequency offset processing on the OFDM source signal to be transmitted according to the target Doppler frequency offset to obtain a target OFDM source signal;

Transmitting the target OFDM source signal.

A Doppler frequency offset estimation apparatus for an OFDM system, which is characterized in that it is applied to a receiving end, and the apparatus includes:

a receiving module, configured to receive an OFDM propagation signal; the first OFDM symbol in the first OFDM frame of the OFDM propagation signal includes Q preset cyclic prefixes; Q is greater than or equal to 3;

An auto-correlation module for performing two-two autocorrelation on all preset cyclic prefixes to obtain a plurality of autocorrelation functions;

a summation module for summing all autocorrelation functions to obtain a probability density function;

a maximum likelihood estimation module, configured to perform maximum likelihood estimation on the probability density function to obtain an initial Doppler frequency offset and a first Doppler rate of change;

An estimating module, configured to estimate a target Doppler frequency offset of a signal sequence change in the first OFDM frame of the OFDM propagation signal according to the initial Doppler frequency offset and the first Doppler rate of change .

The device according to claim 8, wherein the autocorrelation module comprises:

a sampling unit, configured to sample all the preset cyclic prefixes to obtain Q×L segmentation signals; wherein, the sampling number of each preset cyclic prefix is L;

An auto-correlation unit, configured to perform a pairwise autocorrelation on all preset cyclic prefixes according to the Q×L segmentation signals to obtain multiple autocorrelation functions; wherein, the first preset cycle of any two preset cyclic prefixes The auto-correlation function is obtained by performing auto-correlation on the prefix and the second preset cyclic prefix; the manner of performing auto-correlation on the first preset cyclic prefix and the second preset cyclic prefix comprises: separately performing the first preset loop The k-th segment signal of the prefix and the k-th segment signal in the second preset cyclic prefix are autocorrelated; k=0, 1, . . . L-1.

A Doppler frequency offset canceling apparatus for an OFDM system, which is characterized in that it is applied to a transmitting end, and the apparatus includes:

a receiving module, configured to receive a target Doppler frequency offset sent by the receiving end; the target Doppler frequency offset is estimated by the receiving end according to the Doppler frequency offset estimating apparatus in the OFDM system according to claim 8 or 9. ;

a reverse processing module, configured to perform Doppler frequency offset processing on the OFDM source signal to be transmitted according to the target Doppler frequency offset, to obtain a target OFDM source signal;

And a sending module, configured to send the target OFDM source signal.

A receiving end, wherein the receiving end comprises: a housing, a processor, and a storage a circuit board, a circuit board, and a power supply circuit, wherein the circuit board is disposed inside the space enclosed by the casing, the processor and the memory are disposed on the circuit board; the power supply circuit is configured to supply power to each circuit or device at the receiving end; and the memory is used for storing Executable program code; the processor runs an application corresponding to the executable program code by reading executable program code stored in the memory for performing Dopp in the OFDM system of any of claims 1-6 Le frequency offset estimation method.

A storage medium for storing an application for performing a Doppler frequency offset estimation method in an OFDM system according to any one of claims 1-6.

An application program for performing a Doppler frequency offset estimation method in an OFDM system according to any one of claims 1-6.

A transmitting end, characterized in that the transmitting end comprises: a housing, a processor, a memory, a circuit board and a power supply circuit, wherein the circuit board is disposed inside the space enclosed by the housing, and the processor and the memory are disposed in the circuit An on-board power supply circuit for powering various circuits or devices at the transmitting end; a memory for storing executable program code; and a processor for executing an application corresponding to the executable program code by reading executable program code stored in the memory And a method for performing Doppler frequency offset cancellation in the OFDM system according to claim 7.

A storage medium, characterized in that the storage medium is for storing an application for performing a Doppler frequency offset elimination method in the OFDM system according to claim 7.

An application program for performing the Doppler frequency offset elimination method in the OFDM system of claim 7.