OFDM radar communication time-frequency synchronization method, device, equipment and medium

Abstract

This application discloses a method, apparatus, device, and medium for time-frequency synchronization of OFDM radar communications, relating to the field of wireless communication technology. The method includes receiving, via a base station-side receiving terminal, an OFDM signal transmitted by a user terminal within a current transmission time interval, obtaining a received signal corresponding to the current transmission time interval, preprocessing the received signal corresponding to the current transmission time interval to obtain a delay-Doppler domain signal matrix corresponding to the current transmission time interval, determining an original fingerprint spectrum based on the initial delay-Doppler domain signal matrix, and determining a carrier frequency offset increment and a time offset increment based on the original fingerprint spectrum and the delay-Doppler domain signal matrix corresponding to the current transmission time interval. This application can address the problems of high computational complexity, numerous restrictions, and limited applicable scenarios in the prior art of time-frequency synchronization.

Description

Technical Field

[0001] The present application relates to the field of wireless communication technology, and in particular to a method, device, equipment and medium for time-frequency synchronization of OFDM (Orthogonal Frequency Division Multiplexing) radar communications. Background Art

[0002] Communication and perception integration refers to the integration of communication and perception functions (such as radar, imaging, and positioning) into the same system or platform through joint air interface and protocol design, time-frequency and space resource reuse, and hardware device sharing. This improves resource utilization efficiency and enhances the overall performance and service capabilities of the system network. In communication networks, the normal operation of most telecommunications services requires that frequency and time differences between devices across the network remain within a reasonable error range, which is known as frequency and clock synchronization. The accuracy of time-frequency synchronization technology significantly affects the accuracy and stability of communication and perception systems. In communication systems, time-frequency synchronization is a key factor in achieving reliable transmission. Low time-frequency synchronization accuracy can lead to signal distortion and increased bit error rates. Perception systems, such as positioning and navigation, rely on parameters such as signal transmission time, so pre-implementation of time-frequency synchronization is necessary to improve accuracy and stability.

[0003] The prior art CN202010843380.0 provides a sensing parameter estimation method, which requires a line-of-sight (LOS) wireless connection between the transmitter and the receiver, and the power of the LOS path is greater than the non-line-of-sight (NLOS) path. The receiver obtains uplink communication signals from multiple transmitter antennas; the receiver performs cross-antenna cross correlation (CACC) processing on the received signal to solve the carrier frequency offset (CFO) and time offset (TO) problems between the receiver and the transmitter. The receiver obtains the sensing parameters corresponding to the received signal through the sensing parameter estimation method.

[0004] However, the above existing time-frequency synchronization methods have the disadvantage of high computational complexity. Summary of the Invention

[0005] The purpose of this application is to provide an OFDM radar communication time-frequency synchronization method, device, equipment and medium, which can reduce the computational complexity and solve the problems of high computational complexity, many restrictions and few applicable scenarios of the existing time-frequency synchronization technology.

[0006] To achieve the above objectives, this application provides the following solutions:

[0007] In a first aspect, the present application provides a method for time-frequency synchronization of OFDM radar communications, comprising:

[0008] Receive, through a base station side receiving end, an OFDM signal sent by a user terminal in a current transmission time interval, and obtain a received signal corresponding to the current transmission time interval;

[0009] Preprocessing the received signal corresponding to the current transmission time interval to obtain a delay-Doppler domain signal matrix corresponding to the current transmission time interval; the delay-Doppler domain signal matrix corresponding to the initial transmission time interval is defined as the initial delay-Doppler domain signal matrix;

[0010] Determine the original fingerprint spectrum according to the initial delay-Doppler domain signal matrix;

[0011] The carrier frequency offset increment and the time offset increment are determined according to the delay-Doppler domain signal matrix corresponding to the original fingerprint spectrum and the current transmission time interval; the carrier frequency offset increment is an increment relative to the initial value of the carrier frequency offset; the time offset increment is an increment relative to the initial value of the time offset; the carrier frequency offset increment and the time offset increment are used for time-frequency synchronization of the OFDM signal.

[0012] In a second aspect, the present application provides an OFDM radar communication time-frequency synchronization device, comprising:

[0013] The signal receiving module is configured to: receive an OFDM signal sent by a user terminal in a current transmission time interval through a base station side receiving terminal, and obtain a received signal corresponding to the current transmission time interval;

[0014] a preprocessing module configured to preprocess a received signal corresponding to a current transmission time interval to obtain a delay-Doppler domain signal matrix corresponding to the current transmission time interval; and define the delay-Doppler domain signal matrix corresponding to an initial transmission time interval as an initial delay-Doppler domain signal matrix.

[0015] The original fingerprint spectrum determination module is used to determine the original fingerprint spectrum according to the initial delay-Doppler domain signal matrix;

[0016] The offset increment determination module is used to: determine the carrier frequency offset increment and the time offset increment based on the delay-Doppler domain signal matrix corresponding to the original fingerprint spectrum and the current transmission time interval; the carrier frequency offset increment is the increment relative to the initial value of the carrier frequency offset; the time offset increment is the increment relative to the initial value of the time offset; the carrier frequency offset increment and the time offset increment are used for time-frequency synchronization of the OFDM signal.

[0017] In a third aspect, the present application provides a computer device comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the above-mentioned OFDM radar communication time-frequency synchronization method.

[0018] In a fourth aspect, the present application provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the above-mentioned OFDM radar communication time-frequency synchronization method.

[0019] According to the specific embodiments provided in this application, this application discloses the following technical effects:

[0020] The present application provides a method, apparatus, device and medium for time-frequency synchronization of OFDM radar communications. The method comprises the following steps: receiving an OFDM signal sent by a user terminal in a current transmission time interval through a base station-side receiving end, obtaining a received signal corresponding to the current transmission time interval, preprocessing the received signal corresponding to the current transmission time interval, obtaining a delay-Doppler domain signal matrix corresponding to the current transmission time interval, determining an original fingerprint spectrum based on the initial delay-Doppler domain signal matrix, and determining a carrier frequency offset increment and a time offset increment based on the original fingerprint spectrum and the delay-Doppler domain signal matrix corresponding to the current transmission time interval. The present application determines the carrier frequency offset increment and the time offset increment by using the fingerprint spectrum as a reference signal, eliminating the need for cross-antenna cross-correlation operations, reducing computational complexity and solving the problem of high computational complexity of existing time-frequency synchronization methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0022] Figure 1 This is an application environment diagram of an OFDM radar communication time-frequency synchronization method in one embodiment of the present application;

[0023] Figure 2 A flowchart of a time-frequency synchronization method for OFDM radar communication provided in one embodiment of the present application;

[0024] Figure 3 A schematic diagram of a detailed flow chart of the pre-processing steps of a received signal provided in one embodiment of the present application;

[0025] Figure 4 A schematic flow chart of a method for obtaining an original fingerprint spectrum in a line-of-sight transmission scenario provided in one embodiment of the present application;

[0026] Figure 5 A schematic flow chart of a method for obtaining an original fingerprint spectrum in a non-line-of-sight transmission scenario provided in one embodiment of the present application;

[0027] Figure 6 A schematic diagram of a detailed flow chart of the steps of determining a carrier frequency offset increment and a time offset increment provided in an embodiment of the present application;

[0028] Figure 7 A schematic diagram of the functional modules of an OFDM radar communication time-frequency synchronization device provided in another embodiment of the present application.

[0029] Figure 8 A schematic diagram of the structure of a computer device provided in one embodiment of the present application. DETAILED DESCRIPTION

[0030] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0031] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the present application is further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0032] Integrated communication and perception technology: Perception and communication can be divided into three levels, from loose coupling to full integration. At the lowest level, communication and perception share hardware and spectrum. Hardware sharing effectively reduces costs, simplifies deployment, and alleviates maintenance issues, allowing perception to benefit from the economies of scale of mobile communication networks. Spectrum sharing makes spectrum utilization more efficient compared to using independent spectrum. The second level integrates waveform and signal processing, combining time-domain, frequency-domain, and spatial-domain waveform and signal processing technologies to serve both perception and communication functions. At the third level, information can be shared across layers, modules, and nodes, achieving full integration of communication and perception. System performance is significantly improved, the overall cost and energy consumption of the network system are greatly reduced, and the system scale is reduced. Other technological innovations, such as greater collaboration between base stations and user devices, joint communication and perception waveform design, advanced interference cancellation techniques, and native AI, can further enhance the processing capabilities of perception data.

[0033] Existing technical solutions can directly use uplink communication signals for radio sensing without changing the current communication / sensing network. The existing time-frequency synchronization scheme (CACC algorithm) is as follows: 1) The receiver obtains uplink communication signals from multiple transmitters. There is a LOS wireless connection between the transmitter and the receiver, and the power of the LOS path is greater than the NLOS path; 2) The received signal of a certain antenna of the receiver is selected as the reference signal; 3) The received signals of the other antennas are cross-correlated with the reference signal to eliminate the frequency offset of the clock offset in the received signal. The CACC algorithm is selected during the time-frequency synchronization process. It is necessary to select the received signal of a certain antenna as the reference signal, and the other antennas perform cross-antenna cross-correlation operations with it. The above steps will introduce unknown parameters of the mirror image, resulting in the number of parameters to be estimated doubling, resulting in a high computational complexity.

[0034] The OFDM radar communication time-frequency synchronization method provided in the embodiment of the present application can be applied to Figure 1 In the application environment shown. Among them, the terminal 102 communicates with the server 104 through the network. The data storage system can store the data that the server 104 needs to process. The data storage system can be set up separately, integrated on the server 104, or placed on the cloud or other servers. The terminal 102 can send the received signal to the server 104. After the server 104 receives the received signal, the server 104 pre-processes the received signal corresponding to the current transmission time interval, obtains the delay-Doppler domain signal matrix corresponding to the current transmission time interval, determines the original fingerprint spectrum according to the initial delay-Doppler domain signal matrix, and determines the carrier frequency offset increment and time offset increment according to the original fingerprint spectrum and the delay-Doppler domain signal matrix corresponding to the current transmission time interval. The server 104 can feed back the obtained carrier frequency offset increment and time offset increment of the received signal to the terminal 102. In addition, in some embodiments, the OFDM radar communication time-frequency synchronization method can also be implemented independently by the server 104 or the terminal 102. For example, the terminal 102 can directly perform OFDM radar communication time-frequency synchronization processing on the received signal, or the server 104 can obtain the received signal from the data storage system and perform OFDM radar communication time-frequency synchronization processing on the received signal.

[0035] The terminal 102 may be, but is not limited to, various desktop computers, laptop computers, smart phones, and tablet computers. The server 104 may be implemented as an independent server or a server cluster consisting of multiple servers, or a cloud server.

[0036] In an exemplary embodiment, Figure 2As shown, a method for time-frequency synchronization of OFDM radar communication is provided. The method is executed by a computer device, specifically a computer device such as a terminal or a server, or a terminal and a server. In the embodiment of the present application, the method is applied to Figure 1 The server 104 in the example is used as an example to illustrate the process, including the following steps 201 to 204.

[0037] Step 201: An OFDM signal sent by a user terminal in a current transmission time interval is received by a base station-side receiving end to obtain a received signal corresponding to the current transmission time interval.

[0038] Step 202: Preprocess the received signal corresponding to the current transmission time interval to obtain a delay-Doppler domain signal matrix corresponding to the current transmission time interval; the delay-Doppler domain signal matrix corresponding to the initial transmission time interval is defined as the initial delay-Doppler domain signal matrix.

[0039] Step 203: Determine the original fingerprint spectrum according to the initial delay-Doppler domain signal matrix.

[0040] Step 204: Determine a carrier frequency offset increment and a time offset increment based on the delay-Doppler domain signal matrix corresponding to the original fingerprint spectrum and the current transmission time interval; the carrier frequency offset increment is an increment relative to the initial value of the carrier frequency offset; the time offset increment is an increment relative to the initial value of the time offset; the carrier frequency offset increment and the time offset increment are used for time-frequency synchronization of the OFDM signal.

[0041] Implement the above steps 201 to 204, and use the original fingerprint spectrum as a reference signal to determine the carrier frequency offset increment and the time offset increment. There is no need for cross-antenna cross-correlation operations, which reduces the computational complexity and solves the problem of high computational complexity of existing time-frequency synchronization methods. In addition, the prior art CN202010843380.0 has the disadvantage of having few applicable scenarios: this technical solution has many restrictions when performing time-frequency synchronization, such as requiring a LOS communication link between the transmitter and the receiver, and requiring the power of the LOS path to be greater than the NLOS path; in addition, the transmitter and the receiver are required to have multiple antennas, which cannot be applied to single-antenna devices. The prior art selects the signal component received by a specific antenna as the synchronization reference signal, and the received signals of other antennas are cross-correlated or simply divided with it to calculate CFO and TO. Therefore, it is not suitable for NLOS and single-antenna receiver scenarios. The present application can also use the signal emitted or reflected by static objects in the environment as a synchronization reference signal. This type of signal carries the location information of the static object and is called the original fingerprint spectrum. Changes in CFO and TO are reflected in the fingerprint spectrum. By analyzing these changes, the CFO and TO values ​​can be obtained. This technology is applicable to both single-antenna and multi-antenna devices, covering a wider range of application scenarios. This technology ensures high-precision time-frequency synchronization under both LOS and NLOS conditions, and is applicable in LOS / NLOS and single / multi-antenna scenarios.

[0042] First, set up the system environment: This application applies to OFDM communication systems. User terminals (UTs) send signals, which are received by base stations after transmission through channels. The number of antennas in the base station is not required, and it can be used in single-antenna or multi-antenna scenarios. It does not require Loss of Surface (LOS) transmission, and can be applied to NLOS transmission scenarios.

[0043] In another exemplary embodiment of the present application, Figure 3 As shown, the above step 201 is replaced by the following steps 301 to 304:

[0044] Step 301: Demodulate the received signal corresponding to the current transmission time interval to obtain demodulated data.

[0045] Step 302: Perform data compensation based on the demodulated data to obtain a compensated signal at the receiving end of the base station side.

[0046] Step 303: Determine a final compensated signal according to the number of antennas at the base station side receiving end and the compensated signal at the base station side receiving end.

[0047] Step 304: Perform two-dimensional spectrum analysis on the final compensated signal to obtain a delay-Doppler domain signal matrix corresponding to the current transmission time interval.

[0048] The user terminal transmits G OFDM symbols to the base station within the transmission time interval, and the base station completes the received signal Y g Demodulation, get demodulated data Specifically, the communication information carried by the received signal corresponding to the current transmission time interval is demodulated to obtain demodulated data.

[0049] According to the demodulated data, the received signal Y g Specifically, the demodulated data is used to compensate the For the original received signal Y g Data compensation is performed to eliminate communication information and obtain the final compensated signal, which is calculated as follows:

[0050]

[0051] in, represents the final compensated signal; F represents the inverse discrete Fourier transform matrix; diag represents a diagonal matrix.

[0052] Construct a matrix based on the received signal after data compensation That is the final compensated signal, where for The mth row represents the gth data-compensated OFDM signal received by the mth antenna at the base station side.

[0053] Step 303 specifically includes the following process:

[0054] 1) When the number of antennas at the base station side receiving end is 1, the compensated signal at the base station side receiving end is determined as the final compensated signal;

[0055] 2) When the number of antennas at the base station receiving end is greater than one, the compensated signal at the base station receiving end includes the compensated signals corresponding to all antennas. The final compensated signal can be obtained in the following two ways:

[0056] The first method is to determine the signal-to-noise ratio of the compensated signal corresponding to each antenna at the base station receiving end, and determine the compensated signal corresponding to the antenna with the largest signal-to-noise ratio as the final compensated signal.

[0057] The second method: When the number of antennas at the base station side receiving end is greater than 1, the compensated signal at the base station side receiving end includes the compensated signals corresponding to all antennas; the compensated signals corresponding to all antennas are fused to obtain the final compensated signal.

[0058] Regarding the selection of the mth antenna, if it is a single-antenna system, the data corresponding to the antenna can be selected for analysis; if it is a multi-antenna system, this application does not require which antenna to select the data corresponding to, and all M antennas can be selected in the specific implementation process. R The antenna with the best signal-to-noise ratio (SNR) is selected for analysis, and the compensated signal corresponding to the antenna with the highest SNR is determined as the final compensated signal. Furthermore, for multi-antenna systems, the received signals from multiple antennas can be selected and combined using any signal data fusion method (such as maximum ratio combining and equal gain combining) to obtain the final compensated signal.

[0059] The final compensated signal Γ m Specifically, two-dimensional fast Fourier transform (2D-FFT), two-dimensional discrete Fourier transform (2D-DFT) or any two-dimensional spectrum analysis method is used to analyze Γ m Processing, we get Γ m The delay-Doppler domain result is defined as the signal matrix This application takes 2D-FFT as an example and uses the following formula to obtain Γ m The delay-Doppler domain result, that is, the delay-Doppler domain signal matrix corresponding to the current transmission time interval

[0060]

[0061] Among them, F G represents the G-dimensional inverse discrete Fourier transform matrix, Indicates N sub dimensional inverse discrete Fourier transform matrix, (·) H represents conjugate transpose, G represents the number of OFDM symbols, N sub Indicates the number of subcarriers in the OFDM signal.

[0062] like Figure 6 As shown, the delay-Doppler domain signal matrix corresponding to the current transmission time interval is Transfer to step 203, the initial Defined as The signal matrix provided at the sampling moment is Defined as Signal Matrix and It can reflect the static environment information and the information of other objects (cars, people, buildings) in the environment. In this application, the above information is defined as the fingerprint spectrum, where The information provided is defined as the raw fingerprint spectrum.

[0063] Step 203 specifically includes the following steps:

[0064] When the transmission type of the signal transmission scenario is a line-of-sight transmission scenario, it is determined whether the initial value of the carrier frequency offset is known, and a first judgment result is obtained. If the first judgment result is yes, an original fingerprint spectrum is determined based on the initial delay-Doppler domain signal matrix and OFDM signal parameters, that is, method one is used to determine the original fingerprint spectrum. The OFDM signal parameters include the number of sampling points, the number of subcarriers, the sampling interval, and the initial value of the carrier frequency offset of the OFDM signal. If the first judgment result is no, it is determined whether the signal transmission scenario has a priori anchor point, and a second judgment result is obtained. The priori anchor point is an object in the signal transmission scenario whose position and / or velocity information is known. If the second judgment result is yes, the fingerprint spectrum of the priori anchor point is determined as the original fingerprint spectrum, that is, method two is used to determine the original fingerprint spectrum. If the second judgment result is no, the original fingerprint spectrum is determined based on the initial delay-Doppler domain signal matrix and an intermediate delay-Doppler domain signal matrix group, that is, method four is used to determine the original fingerprint spectrum. The intermediate delay-Doppler domain signal matrix group includes delay-Doppler domain signal matrices corresponding to several transmission time intervals after the initial transmission time interval. The specific process of determining the original fingerprint spectrum in the line-of-sight transmission scenario is as follows: Figure 4 shown.

[0065] When the transmission type of the signal transmission scenario is a non-line-of-sight transmission scenario, it is determined whether the initial value of the carrier frequency offset is known, and a third judgment result is obtained. If the third judgment result is yes, the original fingerprint spectrum is determined based on the initial delay-Doppler domain signal matrix and the OFDM signal parameters, that is, the original fingerprint spectrum is determined using method one. If the third judgment result is no, it is determined whether the signal transmission scenario has a priori anchor point, and a fourth judgment result is obtained. If the fourth judgment result is yes, the fingerprint spectrum of the priori anchor point is determined as the original fingerprint spectrum, that is, the original fingerprint spectrum is determined using method two. If the fourth judgment result is no, it is determined whether the signal transmission scenario is converted from a line-of-sight transmission scenario and the line-of-sight transmission scenario has a priori anchor point, and a fifth judgment result is obtained. If the fifth judgment result is yes, the fingerprint spectrum of the priori anchor point is determined as the original fingerprint spectrum, that is, the original fingerprint spectrum is determined using method three. If the fifth judgment result is no, the original fingerprint spectrum is determined based on the initial delay-Doppler domain signal matrix and the intermediate delay-Doppler domain signal matrix group, that is, the original fingerprint spectrum is determined using method four. The specific process of determining the original fingerprint spectrum in non-line-of-sight transmission scenarios is as follows: Figure 5 shown.

[0066] The specific process of the above methods 1 to 4 is as follows:

[0067] Method 1 is applicable to the scenario where the carrier frequency offset f is caused by the difference in crystal oscillators between the user terminal UT and the base station. oThe specific process is as follows: If it is known that the carrier frequency offset f caused by the different crystal oscillators of the user terminal UT and the base station o , then select As the original fingerprint spectrum, express K c All elements of the row; K c =Round(ξ o N s / N sub ),ξ o =N sub f o T s , that is, K c =Round(ξ o N s f o T s ), N s is the number of sampling points of each OFDM signal, T s is the sampling interval, and Round() represents the rounding function.

[0068] Method 2 is applicable when f cannot be obtained in advance. o , but there are prior anchor points in the scene, the specific process is: if it is not possible to obtain f in advance o , then the synchronization module needs to obtain the original fingerprint spectrum based on the prior anchor points in the environment.

[0069] Select a priori anchor points in signal transmission scenarios. A priori anchor points are objects whose position and / or velocity information is known. For example, in LOS scenarios, the prior anchor point can be a static user terminal; in NLOS scenarios, the prior anchor point can be a static reflective object (such as a building).

[0070] The signal emitted or reflected from the prior anchor point has a constant and significant fingerprint spectrum, which can be manually extracted. For example, in the LOS scenario, the original fingerprint spectrum corresponding to the static UT anchor point will be The corresponding row in the figure shows a high-power Sinc function; in the NLOS scenario, the spatial distribution of the selected static anchor points will also be shown in It is reflected as a specific spectrum feature, so the corresponding original fingerprint spectrum can be intuitively converted from Extracted from.

[0071] Method 3 is applicable when f cannot be obtained in advance. o , and the NLOS scene cannot select a priori anchor points, but the NLOS scene is converted from the LOS environment at some point and a priori anchor points can be selected in the LOS scene. The specific process is: if it is not possible to obtain f in advance oAt the same time, the original fingerprint spectrum cannot be obtained through the prior anchor point in the NLOS scenario. Consider that the NLOS environment is converted from the LOS environment at some point in time, and the original fingerprint spectrum can be obtained through the prior anchor point in the LOS environment. In the LOS scenario, method 2 is used to obtain the original fingerprint spectrum of the LOS scenario. When the LOS scene is converted to the NLOS scene, the original fingerprint spectrum obtained from the LOS scene at the corresponding moment is selected as the original fingerprint spectrum of the NLOS scene. When the LOS scene is converted to the NLOS scene, moving targets such as vehicles or people appear.

[0072] Method 4 is applicable when f cannot be obtained in advance. o , and no matter in the LOS scenario or NLOS scenario, the prior anchor point cannot be selected, the specific process is: if the above method cannot be used to obtain the original fingerprint spectrum in both the LOS scenario and the NLOS scenario, it is necessary to use and multiple groups This situation is generally because the signal will be reflected by moving targets such as vehicles or people at certain moments, making it difficult to distinguish the original fingerprint spectrum. Considering that the signal emitted / reflected by the prior anchor point will be reflected as a constant and obvious spectrum feature in the delay-Doppler domain, while the signal emitted / reflected by the frequently moving target will only be reflected as an obvious spectrum feature in the delay-Doppler domain at certain moments, the identification and multiple groups The original fingerprint spectrum can be extracted from the spectral features with constant and obvious positions in the data.

[0073] According to step 203, the original fingerprint spectrum is updated regularly and recorded as ζ.

[0074] In addition, considering that estimating CFO and TO simultaneously is a 2-D likelihood search scheme, in order to further reduce the complexity, the present application can also use two 1-D likelihood search schemes to estimate CFO and TO separately.

[0075] According to the original fingerprint spectrum ζ obtained in step 203 and the signal matrix provided by the data preprocessing module Using likelihood, correlation or any feasible signal processing method, the increments of the carrier frequency offset CFO and the time offset TO relative to the initial values ​​are obtained. Furthermore, the present application proposes two synchronization schemes for selection in the synchronization module.

[0076] 1) 2-D likelihood estimation scheme, step 204 may include:

[0077] A likelihood estimation method or a cross-correlation method is used to determine a carrier frequency offset increment and a time offset increment according to the original fingerprint spectrum and a delay-Doppler domain signal matrix corresponding to the current transmission time interval.

[0078] Use likelihood estimation method, cross-correlation method or any feasible signal processing method to estimate ζ and For analysis, this application takes the cross-correlation method as an example, specifically:

[0079]

[0080] Where k = 1,…,K B ,q=1,…,Q B , G is the number of OFDM symbols, N s is the number of sampling points per OFDM symbol; The carrier frequency offset CFO to be estimated is the increment relative to the initial value, that is, the carrier frequency offset increment; That is, the increment of the time offset TO relative to the initial value, that is, the time offset increment; ζ * (i) represents the conjugate of the i-th element of the original fingerprint spectrum.

[0081] 2) Simplified 1-D maximum likelihood estimation scheme, step 204 may include:

[0082] Determining a target row index value of a delay-Doppler domain signal matrix according to the original fingerprint spectrum and the delay-Doppler domain signal matrix corresponding to the current transmission time interval using a likelihood estimation method or a cross-correlation method;

[0083] determining a carrier frequency offset increment according to a target row index value of a delay-Doppler domain signal matrix;

[0084] A likelihood analysis is performed on a target row matrix and the original fingerprint spectrum using a likelihood estimation method or a cross-correlation method to obtain a time offset increment; the target row matrix is ​​a matrix composed of elements of a target row index value row of the delay-Doppler domain signal matrix corresponding to the current transmission time interval.

[0085] According to the obtained ζ and Use likelihood estimation method, cross-correlation method or any feasible signal processing method to obtain The row index of the data in a row is most similar to the original fingerprint spectrum ζ, and the value of the row index is equal to This application takes the maximum likelihood algorithm in the likelihood algorithm as an example, and the following formula can be used to obtain The row index K that is most similar to the original fingerprint spectrum ζ in a row of data:

[0086]

[0087] because Therefore, the carrier frequency offset increment can be estimated using the following formula:

[0088]

[0089] According to the obtained ζ and Use likelihood estimation method, cross-correlation method or any feasible signal processing method to analyze the original fingerprint spectrum ζ and matrix The target row matrix (the target row matrix is No. This application takes cross-correlation as an example, and the time offset increment can be estimated using the following formula:

[0090]

[0091] After the above process, the output carrier frequency offset increment and the time offset increment

[0092] This application also provides an application scenario that utilizes the aforementioned OFDM radar communication time-frequency synchronization method. Specifically, the OFDM radar communication time-frequency synchronization method provided in this embodiment can be applied in a time-frequency synchronization scenario. The time-frequency synchronization scenario includes a signal transmission link, an OFDM radar communication time-frequency synchronization processing link, and a time-frequency synchronization link. The OFDM signal transmitted by the user terminal enters the OFDM radar communication time-frequency synchronization processing link from the signal transmission link, obtains corresponding carrier frequency offset increments and time offset increments, and then enters the downstream time-frequency synchronization link. The OFDM radar communication time-frequency synchronization method provided in this embodiment belongs to the content processing link. Specifically, during the content processing link, a base station-side receiving end can receive an OFDM signal transmitted by a user terminal during a current transmission time interval, obtain a received signal corresponding to the current transmission time interval, pre-process the received signal corresponding to the current transmission time interval to obtain a delay-Doppler domain signal matrix corresponding to the current transmission time interval, determine an original fingerprint spectrum based on the initial delay-Doppler domain signal matrix, and determine the carrier frequency offset increment and time offset increment based on the original fingerprint spectrum and the delay-Doppler domain signal matrix corresponding to the current transmission time interval.

[0093] Based on the same inventive concept, embodiments of the present application also provide an OFDM radar communication time-frequency synchronization device for implementing the aforementioned OFDM radar communication time-frequency synchronization method. The implementation solution provided by this device is similar to the implementation solution described in the aforementioned method. Therefore, the specific limitations in one or more OFDM radar communication time-frequency synchronization device embodiments provided below can be found in the above-mentioned limitations of the OFDM radar communication time-frequency synchronization method and will not be repeated here.

[0094] In an exemplary embodiment, Figure 7As shown, an OFDM radar communication time-frequency synchronization device is provided, including:

[0095] The signal receiving module T1 is configured to receive an OFDM signal sent by a user terminal in a current transmission time interval through a base station side receiving terminal, and obtain a received signal corresponding to the current transmission time interval.

[0096] The preprocessing module T2 is used to preprocess the received signal corresponding to the current transmission time interval to obtain a delay-Doppler domain signal matrix corresponding to the current transmission time interval; the delay-Doppler domain signal matrix corresponding to the initial transmission time interval is defined as the initial delay-Doppler domain signal matrix.

[0097] The original fingerprint spectrum determination module T3 is used to determine the original fingerprint spectrum according to the initial delay-Doppler domain signal matrix.

[0098] The offset increment determination module T4 is used to: determine the carrier frequency offset increment and the time offset increment based on the delay-Doppler domain signal matrix corresponding to the original fingerprint spectrum and the current transmission time interval; the carrier frequency offset increment is the increment relative to the initial value of the carrier frequency offset; the time offset increment is the increment relative to the initial value of the time offset; the carrier frequency offset increment and the time offset increment are used for time-frequency synchronization of the OFDM signal.

[0099] In an exemplary embodiment, a computer device is provided. The computer device may be a server or a terminal. The internal structure diagram thereof may be as follows: Figure 8 As shown. The computer device includes a processor, a memory, an input / output interface (Input / Output, abbreviated as I / O) and a communication interface. The processor, memory and input / output interface are connected through a system bus, and the communication interface is connected to the system bus through the input / output interface. The processor of the computer device is used to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system, a computer program and a database. The internal memory provides an environment for the operation of the operating system and computer program in the non-volatile storage medium. The database of the computer device is used to store OFDM radar communication time-frequency synchronization data. The input / output interface of the computer device is used to exchange information between the processor and an external device. The communication interface of the computer device is used to communicate with an external terminal through a network connection. When the computer program is executed by the processor, a method for time-frequency synchronization of OFDM radar communication is implemented.

[0100] Those skilled in the art will understand that Figure 8The structure shown in the figure is only a block diagram of a part of the structure related to the solution of the present application, and does not constitute a limitation on the computer device to which the solution of the present application is applied. The specific computer device may include more or fewer components than shown in the figure, or combine certain components, or have a different component arrangement.

[0101] In an exemplary embodiment, a computer device is further provided, including a memory and a processor. The memory stores a computer program, and the processor implements the steps in the above method embodiments when executing the computer program.

[0102] In an exemplary embodiment, a computer-readable storage medium is provided, storing a computer program. When the computer program is executed by a processor, the steps in the above-mentioned method embodiments are implemented.

[0103] It should be noted that the user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data used for analysis, stored data, displayed data, etc.) involved in this application are all information and data authorized by the user or fully authorized by all parties, and the collection, use and processing of relevant data must comply with relevant regulations.

[0104] Those skilled in the art will understand that all or part of the processes in the above-mentioned embodiment methods can be implemented by instructing the relevant hardware through a computer program, and the computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above-mentioned methods. Among them, any reference to memory, database or other media used in the embodiments provided in this application may include at least one of non-volatile and volatile memory. Non-volatile memory may include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory may include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM may be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM).

[0105] The databases involved in the various embodiments provided herein may include at least one of a relational database and a non-relational database. Non-relational databases may include, but are not limited to, distributed databases based on blockchains. The processors involved in the various embodiments provided herein may include, but are not limited to, general-purpose processors, central processing units, graphics processing units, digital signal processors, programmable logic units, data processing logic units based on quantum computing, and the like.

[0106] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0107] This document uses specific examples to illustrate the principles and implementation methods of this application. The description of the above examples is only intended to help understand the method and core concept of this application. At the same time, for those skilled in the art, based on the concept of this application, there may be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting this application.

Claims

1. A time-frequency synchronization method for OFDM radar communication, characterized in that: The OFDM radar communication time-frequency synchronization method comprises: Receive, through a base station side receiving end, an OFDM signal sent by a user terminal in a current transmission time interval, and obtain a received signal corresponding to the current transmission time interval; Preprocessing the received signal corresponding to the current transmission time interval to obtain a delay-Doppler domain signal matrix corresponding to the current transmission time interval; the delay-Doppler domain signal matrix corresponding to the initial transmission time interval is defined as the initial delay-Doppler domain signal matrix; Determine the original fingerprint spectrum according to the initial delay-Doppler domain signal matrix; The carrier frequency offset increment and the time offset increment are determined according to the delay-Doppler domain signal matrix corresponding to the original fingerprint spectrum and the current transmission time interval; the carrier frequency offset increment is an increment relative to the initial value of the carrier frequency offset; the time offset increment is an increment relative to the initial value of the time offset; the carrier frequency offset increment and the time offset increment are used for time-frequency synchronization of the OFDM signal.

2. The OFDM radar communication time-frequency synchronization method according to claim 1, characterized in that: Preprocessing the received signal corresponding to the current transmission time interval to obtain a delay-Doppler domain signal matrix corresponding to the current transmission time interval, specifically including: Demodulating the received signal corresponding to the current transmission time interval to obtain demodulated data; Performing data compensation based on the demodulated data to obtain a compensated signal at a receiving end on the base station side; Determine a final compensated signal according to the number of antennas at the base station side receiving end and the compensated signal at the base station side receiving end; A two-dimensional spectrum analysis is performed on the final compensated signal to obtain a delay-Doppler domain signal matrix corresponding to the current transmission time interval.

3. The OFDM radar communication time-frequency synchronization method according to claim 2, characterized in that: The final compensated signal is determined according to the number of antennas at the base station side receiving end and the compensated signal at the base station side receiving end, specifically including: When the number of antennas at the base station side receiving end is 1, determining the compensated signal at the base station side receiving end as the final compensated signal; When the number of antennas at the base station side receiving end is greater than 1, the compensated signal at the base station side receiving end includes the compensated signals corresponding to all antennas; the signal-to-noise ratio of the compensated signal corresponding to each antenna at the base station side receiving end is determined, and the compensated signal corresponding to the antenna with the largest signal-to-noise ratio is determined as the final compensated signal.

4. The OFDM radar communication time-frequency synchronization method according to claim 2, characterized in that: Determining the final compensated signal according to the number of antennas at the base station side receiving end and the compensated signal at the base station side receiving end further includes: When the number of antennas at the base station side receiving end is greater than 1, the compensated signal at the base station side receiving end includes the compensated signals corresponding to all antennas; The compensated signals corresponding to all antennas are fused to obtain the final compensated signal.

5. The OFDM radar communication time-frequency synchronization method according to claim 1, characterized in that: Determine the original fingerprint spectrum based on the initial delay-Doppler domain signal matrix, specifically including: When the transmission type of the signal transmission scenario is a line-of-sight transmission scenario, determine whether the initial value of the carrier frequency offset is known to obtain a first judgment result; if the first judgment result is yes, determine the original fingerprint spectrum according to the initial delay-Doppler domain signal matrix and the OFDM signal parameters; the OFDM signal parameters include the number of sampling points, the number of subcarriers, the sampling interval and the initial value of the carrier frequency offset of the OFDM signal; if the first judgment result is no, determine whether the signal transmission scenario has a priori anchor point to obtain a second judgment result; the priori anchor point is an object in the signal transmission scenario whose position and / or speed information is known; if the second judgment result is yes, determine the fingerprint spectrum of the priori anchor point as the original fingerprint spectrum; if the second judgment result is no, determine the original fingerprint spectrum according to the initial delay-Doppler domain signal matrix and the intermediate delay-Doppler domain signal matrix group; the intermediate delay-Doppler domain signal matrix group includes the delay-Doppler domain signal matrices corresponding to several transmission time intervals after the initial transmission time interval; When the transmission type of the signal transmission scenario is a non-line-of-sight transmission scenario, determine whether the initial value of the carrier frequency offset is known to obtain a third judgment result; if the third judgment result is yes, determine the original fingerprint spectrum based on the initial delay-Doppler domain signal matrix and the OFDM signal parameters; if the third judgment result is no, determine whether the signal transmission scenario has a priori anchor point to obtain a fourth judgment result; if the fourth judgment result is yes, determine the fingerprint spectrum of the priori anchor point as the original fingerprint spectrum; if the fourth judgment result is no, determine whether the signal transmission scenario is converted from a line-of-sight transmission scenario and the line-of-sight transmission scenario has a priori anchor point to obtain a fifth judgment result; if the fifth judgment result is yes, determine the fingerprint spectrum of the priori anchor point as the original fingerprint spectrum; if the fifth judgment result is no, determine the original fingerprint spectrum based on the initial delay-Doppler domain signal matrix and the intermediate delay-Doppler domain signal matrix group.

6. The OFDM radar communication time-frequency synchronization method according to claim 1, characterized in that: Determining a carrier frequency offset increment and a time offset increment according to the delay-Doppler domain signal matrix corresponding to the original fingerprint spectrum and the current transmission time interval specifically includes: A likelihood estimation method or a cross-correlation method is used to determine a carrier frequency offset increment and a time offset increment according to the original fingerprint spectrum and a delay-Doppler domain signal matrix corresponding to the current transmission time interval.

7. The OFDM radar communication time-frequency synchronization method according to claim 1, characterized in that: Determining a carrier frequency offset increment and a time offset increment according to the delay-Doppler domain signal matrix corresponding to the original fingerprint spectrum and the current transmission time interval specifically includes: Determining a target row index value of a delay-Doppler domain signal matrix according to the original fingerprint spectrum and the delay-Doppler domain signal matrix corresponding to the current transmission time interval using a likelihood estimation method or a cross-correlation method; determining a carrier frequency offset increment according to a target row index value of a delay-Doppler domain signal matrix; A likelihood analysis is performed on a target row matrix and the original fingerprint spectrum using a likelihood estimation method or a cross-correlation method to obtain a time offset increment; the target row matrix is ​​a matrix composed of elements of a target row index value row of the delay-Doppler domain signal matrix corresponding to the current transmission time interval.

8. An OFDM radar communication time-frequency synchronization device, characterized in that: The OFDM radar communication time-frequency synchronization device comprises: The signal receiving module is configured to: receive an OFDM signal sent by a user terminal in a current transmission time interval through a base station side receiving terminal, and obtain a received signal corresponding to the current transmission time interval; a preprocessing module configured to preprocess a received signal corresponding to a current transmission time interval to obtain a delay-Doppler domain signal matrix corresponding to the current transmission time interval; and define the delay-Doppler domain signal matrix corresponding to an initial transmission time interval as an initial delay-Doppler domain signal matrix. The original fingerprint spectrum determination module is used to determine the original fingerprint spectrum according to the initial delay-Doppler domain signal matrix; The offset increment determination module is used to: determine the carrier frequency offset increment and the time offset increment based on the delay-Doppler domain signal matrix corresponding to the original fingerprint spectrum and the current transmission time interval; the carrier frequency offset increment is the increment relative to the initial value of the carrier frequency offset; the time offset increment is the increment relative to the initial value of the time offset; the carrier frequency offset increment and the time offset increment are used for time-frequency synchronization of the OFDM signal.

9. A computer device comprising: A memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the OFDM radar communication time-frequency synchronization method according to any one of claims 1 to 7.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the OFDM radar communication time-frequency synchronization method according to any one of claims 1 to 7 is implemented.

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