Doppler frequency shift compensation method and device

Abstract

The invention discloses a Doppler frequency shift compensation method and device. Relates to the technical field of communication. The method specifically comprises the steps that a receiving end obtains a receiving signal, the receiving signal is a signal which reaches the receiving end after a sending signal is transmitted through a channel, and Doppler frequency shift exists between the receiving signal and the sending signal. And the receiving end performs linear compensation on the Doppler frequency shift of the received signal to obtain a first received signal. And the receiving end iterates the residual volume of the Doppler frequency shift of the first receiving signal to gradually compensate the Doppler frequency shift of the first receiving signal to obtain a second receiving signal, and the Doppler frequency shift between the second receiving signal and the sending signal is within a preset range. And the receiving end demodulates the second receiving signal to obtain information in the second receiving signal. Through the method, the Doppler frequency shift in a communication system can be accurately compensated and corrected.

Description

Technical Field

[0001] The present application relates to the field of communication technology, and in particular to a Doppler frequency shift compensation method and device. Background Art

[0002] In low-orbit satellite communication systems, satellites orbit the earth at a speed of about 7.9 km / s to communicate with ground equipment. This causes relative motion between the signal transmitter and the receiver, resulting in Doppler shift between the received signal and the transmitted signal. In satellite communication systems, Doppler shift can seriously degrade communication performance. Therefore, it is necessary to solve the problem of Doppler shift compensation and correction. Summary of the invention

[0003] The present application provides a Doppler frequency shift compensation method and device for compensating and correcting the Doppler frequency shift in a communication system.

[0004] In the first aspect, the present application provides a Doppler shift compensation method. The method can be applied to a receiving end, and the method specifically includes: the receiving end obtains a received signal, the received signal is a signal that reaches the receiving end after the transmitted signal is transmitted through a channel, and there is a Doppler shift between the received signal and the transmitted signal. The receiving end linearly compensates the Doppler shift of the received signal to obtain a first received signal. The receiving end iterates the residual amount of the Doppler shift of the first received signal to gradually compensate for the Doppler shift of the first received signal to obtain a second received signal, and the Doppler shift between the second received signal and the transmitted signal is within a preset range. The receiving end demodulates the second received signal to obtain information in the second received signal.

[0005] In an embodiment of the present application, after acquiring a received signal, the receiving end first linearly compensates for the Doppler shift of the received signal to obtain a first received signal. Then, the residual amount of the Doppler shift of the first received signal is iterated to gradually compensate for the Doppler shift of the first received signal to obtain a second received signal. The advantage of using linear compensation is that it is simple to calculate and consumes less resources, but it is not accurate enough. The advantage of using algorithm iteration to compensate for Doppler shift is that the calculation is accurate, but it consumes more resources. Therefore, first linearly compensate for the Doppler shift of the received signal, and then iterate the residual amount of the Doppler shift through an algorithm, which can save computing resources and accurately compensate for the Doppler shift.

[0006] Optionally, linear compensation is performed on the Doppler shift of the received signal to obtain a first received signal, including: the receiving end calculates the Doppler shift values ​​of at least two CPs based on the frequency deviation of at least two cyclic prefixes CP in the received signal relative to the transmitted signal. The receiving end determines the linear relationship between the Doppler shift values ​​of at least two CPs based on the Doppler shift values ​​of the at least two CPs and the number of symbols included in the data block between the at least two CPs, and performs linear interpolation calculation on the Doppler shift values ​​of the at least two CPs according to the linear relationship to obtain the Doppler shift value corresponding to each symbol of the data block between the at least two CPs. The receiving end performs Doppler shift compensation on the received signal according to the Doppler shift value corresponding to each symbol to obtain the first received signal.

[0007] In an embodiment of the present application, since at least two CPs are known, the receiving end can calculate the Doppler frequency shift values ​​of at least two CPs based on the frequency deviation of at least two CPs in the received signal relative to the transmitted signal, and then obtain the Doppler frequency shift value corresponding to each symbol of the data block between the at least two CPs through linear interpolation calculation, perform linear compensation on the received signal, and obtain a first received signal.

[0008] Optionally, the Doppler frequency shift values ​​of at least two CPs are calculated using the following formula:

[0009]

[0010] in, represents the Doppler frequency shift value of the i-th CP, Ncp represents the number of CP symbols, L represents the statistics starting from the L-th symbol of the CP, u i,k represents the kth symbol of the received signal, represents the kth symbol of the transmitted signal, for The conjugate of Stands for signal-to-noise ratio.

[0011] Optionally, the first received signal and the transmitted signal respectively include a plurality of symbols, and the Doppler frequency shift of the first received signal is gradually compensated by iterating the residual amount of the Doppler frequency shift of the first received signal to obtain the second received signal, including: the receiving end determines the corresponding reconstructed signal according to each symbol of the first received signal, and the reconstructed signal is a signal obtained by adding the estimated residual amount of the Doppler frequency shift to each symbol of the first received signal. Determine the error between the first received signal and the reconstructed signal. Compensate the first received signal according to the error to obtain an updated first received signal and a reconstructed signal, and gradually reduce the error to within a preset range by iterating the residual amount of the Doppler frequency shift of the first received signal, and determine that the updated first received signal is the second received signal after the error is reduced to within the preset range.

[0012] In the embodiment of the present application, since the first received signal is obtained through linear compensation, in actual situations, the phase deflection value caused by the Doppler frequency shift of each symbol of the first received signal is not in a strictly linear relationship, and therefore, the first received signal has a residual amount of Doppler frequency shift relative to the transmitted signal. The residual amount of the Doppler frequency shift of the first received signal can be iterated by defining a reconstructed signal so that the error is gradually reduced to a preset range, and the second received signal can be obtained, so that the residual amount of the Doppler frequency shift of the first received signal can be compensated more accurately.

[0013] Optionally, the error is calculated using the following formula:

[0014]

[0015]

[0016]

[0017] Among them, e i,k is the error of the kth symbol of the ith data block of the first received signal at each iteration, for e i,k The conjugate of i,k is the received signal of the kth symbol of the ith data block, is the reconstructed signal of the kth symbol of the ith data block at the nth iteration, w i,k-1 is a compensation coefficient, and the compensation coefficient is used to calculate the second received signal according to the first received signal. for w i,k-1 Conjugation, ω i is the compensation coefficient matrix composed of compensation coefficients, k i，k is the adaptive weight vector.

[0018] Among them, after the error is reduced to a preset range, the compensation coefficient matrix ω is updated i The first received signal is compensated to obtain a second received signal.

[0019] In the second aspect, the present application provides a Doppler shift compensation device. The device includes: an acquisition module, a compensation module and a demodulation module. Among them, the acquisition module is used to acquire a received signal, and the received signal is a signal that reaches the receiving end after the transmitted signal is transmitted through a channel, and there is a Doppler shift between the received signal and the transmitted signal. The compensation module is used to linearly compensate for the Doppler shift of the received signal to obtain a first received signal. The compensation module is also used to gradually compensate for the Doppler shift of the first received signal by iterating the residual amount of the Doppler shift of the first received signal to obtain a second received signal, and the Doppler shift between the second received signal and the transmitted signal is within a preset range. The demodulation module is used to demodulate the second received signal to obtain information in the second received signal.

[0020] Optionally, the compensation module is specifically used to: calculate the Doppler shift values ​​of at least two CPs based on the frequency deviation of at least two cyclic prefixes CP in the received signal relative to the transmitted signal. Determine the linear relationship between the at least two CPs regarding the Doppler shift values ​​based on the Doppler shift values ​​of the at least two CPs and the number of symbols included in the data block between the at least two CPs, and perform linear interpolation calculation on the Doppler shift values ​​of the at least two CPs according to the linear relationship to obtain the Doppler shift values ​​corresponding to each symbol of the data block between the at least two CPs. Perform Doppler shift compensation on the received signal according to the Doppler shift values ​​corresponding to each symbol to obtain a first received signal.

[0021] Optionally, the Doppler frequency shift values ​​of at least two CPs are calculated using the following formula:

[0022]

[0023] in, represents the Doppler frequency shift value of the i-th CP, Ncp represents the number of CP symbols, L represents the statistics starting from the L-th symbol of the CP, u i,k represents the kth symbol of the received signal, represents the kth symbol of the transmitted signal, for The conjugate of Stands for signal-to-noise ratio.

[0024] Optionally, the first received signal and the transmitted signal respectively include a plurality of symbols, and the compensation module is specifically used to: determine a corresponding reconstructed signal according to each symbol of the first received signal, and the reconstructed signal is a signal obtained by adding an estimated residual amount of Doppler frequency shift to each symbol of the first received signal. Determine the error between the first received signal and the reconstructed signal. Compensate the first received signal according to the error to obtain an updated first received signal and a reconstructed signal. Iterate the residual amount of Doppler frequency shift of the first received signal so that the error is gradually reduced to within a preset range, and determine that the updated first received signal is the second received signal after the error is reduced to within the preset range.

[0025] Optionally, the error is calculated using the following formula:

[0026]

[0027]

[0028]

[0029] Among them, e i,k The error of the kth symbol of the i-th data block of the first received signal at each iteration, for e i,k The conjugate of i,k is the received signal of the kth symbol of the ith data block, is the reconstructed signal of the kth symbol of the ith data block at the nth iteration, w i,k-1 is a compensation coefficient, and the compensation coefficient is used to calculate the second received signal according to the first received signal. for w i,k-1 Conjugation, ω i is the compensation coefficient matrix composed of compensation coefficients, k i，k is the adaptive weight vector.

[0030] Among them, after the error is reduced to a preset range, the compensation coefficient matrix ω is updated i The first received signal is compensated to obtain a second received signal.

[0031] In a third aspect, an embodiment of the present application provides an electronic device, the electronic device comprising a processor and a memory in communication with the processor, wherein the memory stores computer-executable instructions, the instructions being executed by the processor so that the processor can execute any of the methods described in the first aspect.

[0032] In a fourth aspect, an embodiment of the present application provides a computer-readable storage medium, which stores computer-executable instructions. When the computer-executable instructions are executed by a processor, the processor executes any one of the methods described in the first aspect above. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 is an architecture diagram of a satellite communication system in an embodiment of the present application;

[0034] Figure 2 A schematic diagram of a flow chart of a Doppler frequency shift compensation method provided in an embodiment of the present application;

[0035] Figure 3 A schematic diagram of the architecture of the SC-FDE communication system provided in an embodiment of the present application;

[0036] Figure 4 A schematic diagram of a frame structure of a signal provided in an embodiment of the present application;

[0037] Figure 5 Another schematic diagram of a flow chart of a Doppler frequency shift compensation method provided in an embodiment of the present application;

[0038] Figure 6 A simulation schematic diagram of a Doppler frequency shift compensation method provided in an embodiment of the present application;

[0039] Figure 7 A schematic diagram of the structure of a Doppler frequency shift compensation device provided in an embodiment of the present application;

[0040] Figure 8 A schematic diagram of the structure of an electronic device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0041] The embodiments of the present application relate to Doppler shift compensation in a communication system. In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the embodiments of the present application will be further described in detail below with reference to the accompanying drawings.

[0042] like Figure 1 As shown, the satellite communication system includes network equipment (base station or gateway), satellite and terminal equipment. The network equipment sends signals to the terminal equipment through the satellite's intermediate switch. There is relative motion between the satellite and the network equipment and the terminal equipment, so that there is a Doppler frequency shift between the received signal and the transmitted signal in the communication link between the network equipment and the satellite, and between the satellite and the terminal equipment. For example, the satellite sends a signal to the terminal equipment as a signal transmitter, and after the transmitted signal is transmitted through the channel, the terminal equipment obtains the received signal as a receiving end. The terminal equipment can expand the frequency domain matrix relationship of the obtained received signal point by point to obtain the following formula:

[0043]

[0044] Among them, P i (k) is the effect of Doppler frequency shift on the phase of the received signal, Pi (0) is the zero-frequency component. i Indicates sending signal, Y i represents the received signal, and H(n) represents the channel matrix. i (k) is the Gaussian white noise in the channel, and Nb represents the number of symbols of the received signal. Therefore, it can be seen that Doppler frequency deviation will produce irregular phase deviation, and it is very important to compensate for it, otherwise it may affect the information obtained in the received signal.

[0045] An existing Doppler frequency shift compensation method is briefly introduced below.

[0046] This method mainly uses network equipment to uniformly configure corresponding reference information for beam cells within the satellite coverage area, and the reference information includes the Doppler frequency shift compensation reference angle. The network equipment sends the reference information to the terminal equipment via the satellite. After receiving the reference information, the terminal equipment can calculate the Doppler frequency shift compensation value on the network equipment side based on the following formula (2). The Doppler frequency shift compensation value on the network equipment-satellite communication link is:

[0047]

[0048] Where θ1 is the Doppler frequency shift compensation reference angle, f c is the carrier frequency, v is the satellite moving speed, and c is the propagation speed of light.

[0049] Then, the terminal device calculates the total Doppler frequency shift compensation value based on the preset ephemeris data and the geographical location of the terminal device. Based on the total Doppler frequency shift compensation value minus the Doppler frequency shift compensation value on the network device-satellite communication link, the Doppler frequency shift compensation value on the satellite-terminal device communication link can be calculated, and the terminal device compensates the received signal on the terminal device side by the compensation value. For details, please refer to the following formula (3):

[0050]

[0051] Among them, θ2 is the angle between the satellite's moving direction and the connecting line between the satellite and the terminal, θ1 is the Doppler shift compensation reference angle, and f c is the carrier frequency, v is the satellite moving speed, and c is the propagation speed of light.

[0052] It can be seen that in any link of this scheme, when calculating the Doppler frequency shift compensation value of the receiving end for the received signal, only the moving direction of the satellite and the angle between the connecting line between the satellite and the terminal device are considered. Since the moving direction of the satellite and the angle between the connecting line between the satellite and the terminal device are constantly changing, the Doppler frequency shift compensation value of the receiving signal of the terminal device should also be constantly changing. In addition, since the network device sends signals to the terminal device via the satellite frame by frame, for the first frame signal and the second frame signal in the transmitted signal, the moving direction of the satellite and the angle between the connecting line between the satellite and the terminal device may be different during the transmission process. In other words, during a signal transmission process, the Doppler frequency shift compensation values ​​of different parts of the signal are also different. Therefore, the existing scheme does not take these situations into consideration and cannot accurately compensate for the Doppler frequency shift according to the actual situation of the signal transmission process in this scenario.

[0053] In view of this, an embodiment of the present application provides a Doppler shift compensation method. After acquiring a received signal, the receiving end first linearly compensates for the Doppler shift of the received signal to obtain a first received signal. Then, the receiving end gradually compensates for the Doppler shift of the first received signal by iterating the residual amount of the Doppler shift of the first received signal to obtain a second received signal. The advantage of using linear compensation is that it is simple to calculate and consumes less resources, but it is not accurate enough. The advantage of using algorithm iteration to compensate for Doppler shift is that the calculation is accurate, but it consumes more resources. Therefore, the Doppler shift of the received signal is first linearly compensated, and then the residual amount of the Doppler shift is iterated by the algorithm, which can save computing resources and accurately compensate for the Doppler shift.

[0054] See also Figure 2 , which shows a flow chart of a Doppler frequency shift compensation method provided by an embodiment of the present application. The method can be applied to Figure 1 In the scenario shown, it is executed by the receiving end. Among them, the receiving end can be a network device, a satellite or a terminal device, which is not specifically limited in the embodiments of the present application. For the convenience of description, in the subsequent introduction, the receiving end executing the Doppler frequency shift compensation method is uniformly used as an example for explanation. It should be noted that in the introduction of the embodiments of the present application, "at least one" refers to one or more, "at least two" refers to two or more, and "multiple" refers to two or more. "And / or" describes the association relationship of associated objects, indicating that three relationships can exist.

[0055] Furthermore, unless otherwise specified, the ordinal numbers such as "first" and "second" mentioned in the embodiments of the present application are used to distinguish multiple objects, and are not used to limit the order, timing, priority or importance of multiple objects. For example, the first received signal and the second received signal are only used to distinguish different received signals, and do not indicate the difference in priority or importance of the two received signals.

[0056] S201: The receiving end obtains a received signal.

[0057] In the embodiment of the present application, the communication system may adopt a single-carrier frequency-domain equalization (SC-FDE) communication system. The architecture of the SC-FDE communication system is as follows: Figure 3 As shown. When the transmitting end sends data, the bit stream is first subjected to digital modulation / mapping, and then S / P serial-to-parallel conversion and CP are added, and then the data after adding CP is divided into blocks to generate a transmission signal. Then, the transmission signal is subjected to P / S parallel-to-serial conversion to send the parallel data serially. When adding CP, a known special sequence can be selected as CP. First, the influence of inter-symbol interference (ICI) caused by multipath during transmission can be eliminated, and second, the channel parameters can be estimated at the receiving end by using CP as known information. It should be understood that when the communication system adopts the SC-FDE communication system, the frame structure of the received signal and the transmitted signal adopts the frame structure in the SC-FDE communication system, and the symbol refers to the symbol in the SC-FDE communication system. Of course, the embodiment of the present application can also adopt an orthogonal frequency division multiplexing (OFDM) system, which is not specifically limited in the embodiment of the present application. When the communication system adopts the OFDM system, the frame structure of the received signal and the transmitted signal adopts the frame structure in the OFDM communication system, and the symbol refers to the OFDM symbol.

[0058] The receiving end obtains the received signal, which is composed of multiple data frames. Each data frame includes Nb symbols. It can be seen from formula (1) that the Doppler frequency shift generated by each symbol during the transmission process is different. Therefore, it is necessary to compensate for the Doppler frequency shift of each symbol according to its situation to minimize the Doppler frequency shift of the received signal relative to the transmitted signal.

[0059] S202: The receiving end performs linear compensation on the Doppler frequency shift of the received signal to obtain a first received signal.

[0060] See also Figure 4, shows the frame structure of the data frame in the embodiment of the present application. A data frame includes a preamble and a data part. Among them, the preamble is composed of a pair of Gray complementary sequences, which is mainly used for channel estimation. The data part is composed of n packets, each packet includes a data block, and a cyclic prefix CP is inserted at the front end of each data block. Among them, a Gray complementary sequence includes 256+16 symbols, the cyclic prefix CP of a packet includes 16 symbols, and a data block includes 240 symbols. For the convenience of explanation, in the subsequent introduction, when calculating the Doppler frequency shift, it is taken as an example that the transmitted signal and the received signal are both composed of a data frame, and the case of multiple data frames is similar and will not be repeated.

[0061] In an embodiment of the present application, based on the above-mentioned frame structure, the receiving end can insert a known CP sequence at the front end of the data block of the transmitted signal, and the known CP sequence is a sequence including the same symbols. In this way, at least two CPs are inserted in the data frame of the transmitted signal, and the data block of each group is adjacent to the CP of the group and the CP of the next group, that is, there is at least one data block between at least two CPs of the data frame. Therefore, since the data of the CP sequence is known, and the data of at least one data block is random, after the receiving end receives the data frame, the phase deviation values ​​of at least two CPs in the received signal relative to the transmitted signal can be obtained, and the Doppler frequency shift values ​​of at least two CPs are calculated based on the phase deviation values ​​of at least two CPs relative to the transmitted signal. It can be understood that the Doppler frequency shift value referred to in the embodiment of the present application represents the relative phase deviation value caused by the Doppler frequency shift.

[0062] As an example, the Doppler frequency shift values ​​of at least two CPs are calculated using the following formula (4):

[0063]

[0064] in, represents the Doppler frequency shift value of the i-th CP, Ncp represents the number of CP symbols, L represents the statistics starting from the L-th symbol of the CP, u i,k represents the kth symbol of the received signal, represents the kth symbol of the transmitted signal, for The conjugate of Stands for signal-to-noise ratio.

[0065] That is to say, the multiple symbols included in the CP sequence are known, and the receiving end can determine the Doppler frequency shift value of each symbol based on the phase deviation of each symbol in the received signal relative to the symbol in the transmitted signal. Finally, the Doppler frequency shift value of the CP can be obtained by summing up all the symbols of the CP.

[0066] Further, using Figure 4 In the frame structure shown in FIG. 1 , the data frames of the transmitted signal are transmitted in the order of group 1, group 2, group 3 and group n. During the transmission process, the receiving end and the transmitting end are always in a state of relative motion. When the receiving end receives the previous group and the next group, the relative position relationship between the receiving end and the transmitting end has changed. In other words, the Doppler shift value of the previous group in the received signal is different from the Doppler shift value of the next group. Considering that the cyclic prefix CP is located at the front end of the data block of each group, if the Doppler shift values ​​of at least two CPs of the data frame are known, the Doppler shift values ​​of the data blocks between the CPs can be estimated based on the obtained Doppler shift values ​​of at least two CPs.

[0067] Since the process of receiving signals at the receiving end is a continuous process, it can be assumed that the Doppler frequency shift values ​​generated by different packets during the transmission process change linearly. In this way, the linear relationship between the Doppler frequency shift values ​​of at least two CPs can be determined based on the Doppler frequency shift values ​​of at least two CPs and the number of symbols included in the data block between at least two CPs, and the Doppler frequency shift values ​​of at least two CPs can be linearly interpolated according to the linear relationship to obtain the Doppler frequency shift value corresponding to each symbol of the data block between at least two CPs. For example, if the Doppler frequency shift value of the CP in packet 1 is known And the Doppler frequency shift value of CP in group 2 It can be assumed that the Doppler frequency shift values ​​generated during the transmission of packets 1 and 2 change linearly. In other words, the CP in packet 1 The Doppler frequency shift value of data block 1 and the CP of packet 2 Linear change, through and Linear interpolation is performed to calculate the Doppler frequency shift value corresponding to each symbol in data block 1.

[0068] As an example, the receiving end may calculate the frequency shift value corresponding to each symbol of the data block between at least two CPs by the following formula (5):

[0069]

[0070] in, represents the kth symbol of the ith data block, and Nb represents that the ith data block includes Nb symbols.

[0071] In the embodiment of the present application, the receiving end can calculate the Doppler frequency shift value corresponding to the symbol of each grouped data block according to formula (5), and perform Doppler frequency shift compensation on each symbol of the received signal through the value to obtain the first received signal. The received signal can be linearly coarsely compensated by linear interpolation, which consumes less resources and is faster to calculate.

[0072] As an example, the receiving end can determine the Doppler frequency shift compensation matrix by the Doppler frequency shift value corresponding to the symbol of each grouped data block obtained by formula (4), as shown in the following formula (6):

[0073]

[0074] In the above formula, 1 Nb×1 Representing a column vector of length Nb with all 1s, the first received signal is obtained by the following equation (7):

[0075]

[0076] S203: The receiving end gradually compensates for the Doppler frequency shift of the first received signal by iterating the residual amount of the Doppler frequency shift of the first received signal to obtain a second received signal, wherein the Doppler frequency shift between the second received signal and the transmitted signal is within a preset range.

[0077] In the above process, the receiving end assumes that the Doppler frequency shift values ​​generated by different groups of signals during the transmission process change linearly, and then obtains the Doppler frequency shift values ​​corresponding to the symbols of the data blocks of each group according to linear interpolation calculation. However, the actual situation is that the phase deflection values ​​caused by the Doppler frequency shift during the transmission of different groups are not strictly linear. Therefore, the first received signal obtained by the receiving end does not completely compensate for the Doppler frequency shift generated by the signal from the transmitting end to the receiving end through the channel transmission, and the first received signal still has a Doppler frequency shift residual relative to the transmitted signal.

[0078] In an embodiment of the present application, the receiving end can gradually compensate for the Doppler shift of the first received signal by iterating the residual amount of the Doppler shift of the first received signal. Since the residual amount of the Doppler shift of each symbol of the first received signal is not the same, the receiving end can determine the corresponding reconstructed signal according to each symbol of the first received signal. The reconstructed signal can be a signal obtained by reconstructing the channel information obtained by channel estimation of the symbol, and then adding the estimated residual amount of the Doppler shift. It can be simply understood that the receiving end obtains a reconstructed received signal after transmitting the symbol in the first received signal through the channel again. Since the symbol is transmitted through the channel again, it will produce a Doppler shift. If the receiving end corrects the Doppler shift of the reconstructed signal relative to the first received signal by a residual amount of an estimated Doppler shift, so that the smaller the error between the reconstructed signal to which the estimated residual amount of the Doppler shift is added and the first received signal, it can be considered that the estimation is more accurate.

[0079] An error between the first received signal and the reconstructed signal may be determined, and a residual amount of the Doppler frequency shift of the first received signal may be iterated to obtain a second received signal.

[0080] The iterative process is briefly as follows. In the first iteration, the first received signal is reconstructed under the same channel conditions to obtain a reconstructed signal, and the estimated residual amount of the Doppler frequency shift of the first received signal is added to the reconstructed signal. The error between the first received signal and the reconstructed signal is determined. The Doppler frequency shift of the first received signal is compensated according to the error to obtain an updated first received signal. In the second iteration, the corresponding reconstructed signal is obtained again through the updated first received signal... Iterate until the error between the updated first received signal and the reconstructed signal is gradually reduced to a preset range. In this way, the smaller the error between the first received signal and the reconstructed signal, the more accurate the estimated residual amount of the Doppler frequency shift of the first received signal. Finally, when the error is reduced to a preset range, the updated first received signal is determined to be the second received signal.

[0081] As an example, the receiving end may use a recursive least square (RLS) algorithm to construct the above iterative process. The following briefly introduces the principle of RLS algorithm iteration.

[0082] The RLS algorithm is an iterative algorithm based on decision feedback. Its core idea is to use the time average criterion of squares for iterative operations, sum the squares of the errors generated in each iteration and minimize them, that is:

[0083]

[0084] In order to better track random signals, a weighted exponential factor is introduced to modify the above formula:

[0085]

[0086] Among them, λ is the forgetting factor, which is a positive number less than 1. Expanding the above formula, we can see that the newer the data, the greater the impact on ε(n). The weighted autocorrelation and cross-correlation matrix is ​​defined as follows:

[0087]

[0088]

[0089] The relationship between the iteration of the RLS algorithm can be obtained as follows:

[0090] w(n)=w(n-1)+k(n) e(n|n-1) (11)

[0091] Where k(n) is the Kalman gain vector, as shown below:

[0092]

[0093] Among them, the values ​​of T(n) and the autocorrelation matrix R(n) are inversely proportional to each other.

[0094] T(n)=R -1 (n) (13)

[0095] Next, the process of iterating the residual amount of Doppler frequency shift based on the RLS algorithm is introduced.

[0096] The first received signal can be expressed as y i,k , then for the first received signal y i,k After channel reconstruction, the estimated residual amount of Doppler frequency shift is added to obtain the reconstructed signal is the reconstructed signal of the kth symbol of the ith data block at the nth iteration. i,k-1 is the compensation coefficient, which can be understood as the estimated residual amount of Doppler frequency shift. Calculated by the following formula:

[0097]

[0098] Further determine the error e between the first received signal and the reconstructed signal i,k :

[0099]

[0100]

[0101] Determine the iteration relationship according to the RLS algorithm:

[0102]

[0103] Among them, e i,k is the error of the kth symbol of the ith data block of the first received signal at each iteration, for e i,k The conjugate of i,k-1 is the compensation coefficient, for w i,k-1 Conjugation, ω i is the compensation coefficient matrix composed of compensation coefficients.

[0104] where k i,k is the adaptive weight vector, corresponding to the nth iteration process as follows:

[0105]

[0106] Among them, p (n) is the value of the inverse correlation matrix during the nth iteration, as shown in the following formula:

[0107]

[0108] According to the above iterative relationship, the error e in each iteration process is obtained i,k and i The compensation coefficient matrix is ​​calculated by the error e i,k and i The compensation coefficient matrix updates the first received signal and the reconstructed signal. Step by step iteration, when the error e i,k After reducing to the preset range, retain the compensation coefficient w of the last iteration i,k-1 , determine the compensation coefficient matrix ω of the last iteration i , through the compensation coefficient matrix ω i The first received signal is compensated to obtain a second received signal.

[0109] S204: The receiving end demodulates the second received signal to obtain information in the second received signal.

[0110] See also Figure 5 , which shows the overall process of the receiving end obtaining information from the received signal. After obtaining the received signal, the receiving end performs coarse Doppler frequency shift compensation on the received signal, that is, linear compensation. The phase deflection of the received signal is linearly calculated, and then the relative phase noise vector is obtained. Further get the relative phase noise compensation matrix pass The received signal is compensated, and then the compensation result is equalized and demodulated to obtain a first received signal, wherein the equalization method is MMSE equalization.

[0111] Then, a reconstructed signal of the first received signal is determined according to the first received signal, and the residual amount of the Doppler frequency shift of the first received signal is estimated by the first received signal and the reconstructed signal to calculate the phase noise vector The first received signal is compensated. Then, equalization and demodulation are judged. When n is less than Nmax, the above process is repeated to iterate the residual amount of the Doppler frequency shift of the first received signal. When the iteration ends, the second received signal is determined according to the updated first received signal, that is, the Doppler frequency shift compensation is completed. Finally, the information in the second received signal can be obtained by demodulating the second received signal.

[0112] like Figure 6 , the simulation results of Doppler frequency shift compensation under QPSK modulation in the Rayli fading channel with Doppler frequency offset are given. This includes the comparison of the system performance without using the compensation algorithm, using only the coarse compensation algorithm and the fine compensation algorithm for one and two iterations respectively, and without Doppler frequency offset. The Doppler frequency offset is calculated by consulting the data and system indicators and according to the formula where f cis the center frequency, c is the speed of light, v is the mobile station speed, θ is the angle between the base station and the mobile station, and f is set d =5000.

[0113] See also Figure 7 Based on the same inventive concept, the embodiment of the present application also provides a Doppler shift compensation device 700. The device 700 includes: an acquisition module 701, a compensation module 702 and a demodulation module 703. Among them, the acquisition module 701 is used to obtain a received signal, and the received signal is a signal that reaches the receiving end after the transmitted signal is transmitted through the channel, and there is a Doppler shift between the received signal and the transmitted signal. The compensation module 702 is used to linearly compensate the Doppler shift of the received signal to obtain a first received signal. The compensation module 702 is also used to gradually compensate the Doppler shift of the first received signal by iterating the residual amount of the Doppler shift of the first received signal to obtain a second received signal, and the Doppler shift between the second received signal and the transmitted signal is within a preset range. The demodulation module 703 is used to demodulate the second received signal to obtain information in the second received signal.

[0114] Optionally, the compensation module 702 is specifically used to: calculate the Doppler shift values ​​of at least two CPs based on the frequency deviation of at least two cyclic prefixes CP in the received signal relative to the transmitted signal. Determine the linear relationship between the at least two CPs regarding the Doppler shift values ​​based on the Doppler shift values ​​of the at least two CPs and the number of symbols included in the data block between the at least two CPs, and perform linear interpolation calculation on the Doppler shift values ​​of the at least two CPs according to the linear relationship to obtain the Doppler shift values ​​corresponding to each symbol of the data block between the at least two CPs. Perform Doppler shift compensation on the received signal according to the Doppler shift value corresponding to each symbol to obtain a first received signal.

[0115] Optionally, the Doppler frequency shift values ​​of at least two CPs are calculated using the following formula:

[0116]

[0117] in, represents the Doppler frequency shift value of the i-th CP, Ncp represents the number of CP symbols, L represents the statistics starting from the L-th symbol of the CP, u i,k represents the kth symbol of the received signal, represents the kth symbol of the transmitted signal, for The conjugate of Stands for signal-to-noise ratio.

[0118] Optionally, the first received signal and the transmitted signal respectively include a plurality of symbols, and the compensation module 702 is specifically used to: determine a corresponding reconstructed signal according to each symbol of the first received signal, and the reconstructed signal is a signal obtained by adding an estimated residual amount of Doppler frequency shift to each symbol of the first received signal. Determine the error between the first received signal and the reconstructed signal. Compensate the first received signal according to the error to obtain an updated first received signal and a reconstructed signal. Iterate the residual amount of Doppler frequency shift of the first received signal so that the error is gradually reduced to within a preset range, and determine that the updated first received signal is the second received signal after the error is reduced to within the preset range.

[0119] Optionally, the error is calculated using the following formula:

[0120]

[0121]

[0122]

[0123] Among them, e i,k The error of the kth symbol of the i-th data block of the first received signal at each iteration, for e i,k The conjugate of i,k is the received signal of the kth symbol of the ith data block, is the reconstructed signal of the kth symbol of the ith data block at the nth iteration, w i,k-1 is a compensation coefficient, and the compensation coefficient is used to calculate the second received signal according to the first received signal. for w i,k-1 Conjugation, ω i is the compensation coefficient matrix composed of compensation coefficients, k i，k is the adaptive weight vector.

[0124] Among them, after the error is reduced to a preset range, the compensation coefficient matrix ω is updated i The first received signal is compensated to obtain a second received signal.

[0125] See also Figure 8 Based on the same inventive concept, an embodiment of the present application provides an electronic device 800, which includes: at least one processor 801, at least one memory 802, and computer program instructions stored in the memory. When the computer program instructions are executed by the processor, the Doppler frequency shift compensation method as described above is implemented.

[0126] Optionally, the processor 801 may be a central processing unit, an application specific integrated circuit (ASIC), one or more integrated circuits for controlling program execution, a hardware circuit developed using a field programmable gate array (FPGA), or a baseband processor.

[0127] Optionally, the read-write lock operation device further includes a memory 802 connected to at least one processor 801, and the memory 802 may include a read-only memory (ROM), a random access memory (RAM), and a disk memory. The memory 802 is used to store data required by the processor 801 when it is running. The number of memories 802 is one or more. Figure 8 However, it should be noted that the memory 802 is not a mandatory functional module, so Figure 8 Shown by dotted lines.

[0128] Based on the same inventive concept, an embodiment of the present application further provides a computer-readable storage medium, which stores computer instructions. When the computer instructions are executed on a computer, the computer executes the Doppler frequency shift compensation method as described above.

[0129] In the specific implementation process, the computer-readable storage medium includes: Universal Serial Bus flash drive (USB), mobile hard disk, read-only memory (ROM), random access memory (RAM), magnetic disk or optical disk, and other storage media that can store program codes.

[0130] Those skilled in the art can clearly understand that for the convenience and simplicity of description, only the division of the above-mentioned functional modules is used as an example. In actual applications, the above-mentioned functions can be assigned to different functional modules as needed, that is, the internal structure of the device is divided into different functional modules to complete all or part of the functions described above. The specific working process of the system, device and unit described above can refer to the corresponding process in the aforementioned method embodiment, and will not be repeated here.

[0131] In the several embodiments provided by the present invention, it should be understood that the disclosed devices and methods can be implemented in other ways. For example, the device embodiments described above are only schematic. For example, the division of the modules or units is only a logical function division. There may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0132] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0133] In addition, each functional unit in each embodiment of the present application may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above-mentioned integrated unit may be implemented in the form of hardware or in the form of software functional units.

[0134] If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present application is essentially or the part that contributes to the prior art or all or part of the technical solution can be embodied in the form of a software product, and the computer software product is stored in a storage medium, including a number of instructions to enable a computer device (which can be a personal computer, a server, or a network device, etc.) or a processor (processor) to perform all or part of the steps of the method described in each embodiment of the present application. The aforementioned storage medium includes: a universal serial bus flash disk (Universal Serial Bus flash disk), a mobile hard disk, a read-only memory (Read-Only Memory, ROM), a random access memory (Random Access Memory, RAM), a disk or an optical disk, and other media that can store program codes.

[0135] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A Doppler frequency shift compensation method, characterized in that: Applied to the receiving end, the method includes: Acquire a received signal, where the received signal is a signal that reaches the receiving end after the transmitted signal is transmitted through a channel, and there is a Doppler frequency shift between the received signal and the transmitted signal; Performing linear compensation on the Doppler frequency shift of the received signal to obtain a first received signal; Iterating the residual amount of the Doppler frequency shift of the first received signal, gradually compensating the Doppler frequency shift of the first received signal, to obtain a second received signal, wherein the Doppler frequency shift between the second received signal and the transmitted signal is within a preset range; The second received signal is demodulated to obtain information in the second received signal.

2. The method according to claim 1, characterized in that Linearly compensating the Doppler frequency shift of the received signal to obtain a first received signal includes: Calculate the Doppler frequency shift values ​​of the at least two cyclic prefixes CP in the received signal based on the frequency deviation of the at least two cyclic prefixes CP in the received signal relative to the transmitted signal; Determining a linear relationship between the at least two CPs regarding Doppler frequency shift values ​​based on the Doppler frequency shift values ​​of the at least two CPs and the number of symbols included in the data block between the at least two CPs, and performing linear interpolation calculation on the Doppler frequency shift values ​​of the at least two CPs according to the linear relationship to obtain a Doppler frequency shift value corresponding to each of the symbols of the data block between the at least two CPs; Doppler frequency shift compensation is performed on the received signal according to the Doppler frequency shift value corresponding to each of the symbols to obtain the first received signal.

3. The method according to claim 2, characterized in that The Doppler frequency shift values ​​of at least two CPs are calculated using the following formula: in, represents the Doppler frequency shift value of the i-th CP, Ncp represents the number of CP symbols, L represents the statistics starting from the L-th symbol of the CP, u i,k represents the kth symbol of the received signal, represents the kth symbol of the transmitted signal, for The conjugate of Stands for signal-to-noise ratio.

4. The method according to any one of claims 1 to 3, characterized in that: The first received signal and the transmitted signal each include a plurality of symbols, and the Doppler frequency shift of the first received signal is gradually compensated by iterating the residual amount of the Doppler frequency shift of the first received signal to obtain a second received signal, including: Determine a corresponding reconstructed signal according to each symbol of the first received signal, wherein the reconstructed signal is a signal obtained by adding an estimated residual amount of Doppler frequency shift to each symbol of the first received signal; determining an error between the first received signal and the reconstructed signal; The first received signal is compensated according to the error to obtain an updated first received signal and the reconstructed signal, the error is gradually reduced to within a preset range by iterating the residual amount of the Doppler frequency shift of the first received signal, and after the error is reduced to within the preset range, the updated first received signal is determined to be the second received signal.

5. The method according to claim 4, characterized in that The error is calculated by the following formula: Among them, e i,k is the error of the kth symbol of the ith data block of the first received signal at each iteration, for e i,k The conjugate of i，k is the received signal of the kth symbol of the ith data block, is the reconstructed signal of the kth symbol of the ith data block at the nth iteration, w i,k-1 is a compensation coefficient, and the compensation coefficient is used to calculate the second received signal according to the first received signal, for w i,k-1 Conjugation, ω i is the compensation coefficient matrix composed of compensation coefficients, k i,k is the adaptive weight vector; After the error is reduced to a preset range, the compensation coefficient matrix ω is updated. i The first received signal is compensated to obtain the second received signal.

6. A Doppler frequency shift compensation device, characterized in that: include: An acquisition module, used for acquiring a received signal, wherein the received signal is a signal that reaches the receiving end after the transmitted signal is transmitted through a channel, and there is a Doppler frequency shift between the received signal and the transmitted signal; A compensation module, used for performing linear compensation on the Doppler frequency shift of the received signal to obtain a first received signal; The compensation module is further configured to gradually compensate for the Doppler frequency shift of the first received signal by iterating the residual amount of the Doppler frequency shift of the first received signal to obtain a second received signal, wherein the Doppler frequency shift between the second received signal and the transmitted signal is within a preset range; A demodulation module is used to demodulate the second received signal to obtain information in the second received signal.

7. The device according to claim 6, characterized in that The compensation module is specifically used for: Calculate the Doppler frequency shift values ​​of the at least two cyclic prefixes CP in the received signal based on the frequency deviation of the at least two cyclic prefixes CP in the received signal relative to the transmitted signal; Determining a linear relationship between the at least two CPs regarding Doppler frequency shift values ​​based on the Doppler frequency shift values ​​of the at least two CPs and the number of symbols included in the data block between the at least two CPs, and performing linear interpolation calculation on the Doppler frequency shift values ​​of the at least two CPs according to the linear relationship to obtain a Doppler frequency shift value corresponding to each of the symbols of the data block between the at least two CPs; Doppler frequency shift compensation is performed on the received signal according to the Doppler frequency shift value corresponding to each of the symbols to obtain the first received signal.

8. The device according to claim 6, characterized in that The first received signal and the transmitted signal respectively include a plurality of symbols, and the compensation module is specifically used for: Determine a corresponding reconstructed signal according to each symbol of the first received signal, wherein the reconstructed signal is a signal obtained by adding an estimated residual amount of Doppler frequency shift to each symbol of the first received signal; determining an error between the first received signal and the reconstructed signal; The first received signal is compensated according to the error to obtain an updated first received signal and the reconstructed signal, the error is gradually reduced to within a preset range by iterating the residual amount of the Doppler frequency shift of the first received signal, and after the error is reduced to within the preset range, the updated first received signal is determined to be the second received signal.

9. An electronic device, characterized in that: include: A processor, and a memory communicatively connected to the processor; The memory stores computer-executable instructions; The processor executes the computer-executable instructions stored in the memory to implement the method according to any one of claims 1 to 5.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores computer-executable instructions, which are used to implement the method according to any one of claims 1 to 5 when executed by a processor.

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