Double-base ISAC clock synchronization algorithm design and system based on LoS reference path

Abstract

The invention belongs to the technical field of unmanned aerial vehicle communication perception integration, discloses a double-base ISAC clock synchronization algorithm design and system based on an LoS reference diameter, and aims to solve the problem of measurement errors caused by clock asynchronization of a transmitting end and a receiving end. And a receiving end receives a communication signal based on an LoS path and a sensing signal based on a non-line-of-sight (NLoS) path through a communication and sensing integrated design. The invention provides a clock synchronization algorithm based on LoS reference path assistance, and the time delay and Doppler frequency of the signal are measured by using the propagation characteristics of the LoS signal, so that the clock skew and Doppler frequency skew are accurately estimated. According to the algorithm, communication and sensing signals are combined, the clock skew of the receiving end is dynamically adjusted and compensated, asynchronous error accumulation is reduced, and sensing precision and system performance are remarkably improved. Simulation results show that the method effectively enhances communication and sensing functions of the system in application scenarios such as low-altitude economy.

Description

Technical Field

[0001] The present invention belongs to the technical field of unmanned aerial vehicle communication and perception integration, and in particular relates to a dual-base ISAC clock synchronization algorithm design and system based on a LoS reference path. Background Art

[0002] Dual-base synaesthesia integration technology is an emerging wireless communication technology. Its core idea is to combine wireless communication and perception functions on the same platform, and use the same hardware resources for data communication and environmental perception at the same time. In this system, the communication signal is not only used for data transmission, but also provides the perception system with real-time environmental information, such as the location, speed, direction, etc. of the target. Therefore, the dual-base synaesthesia integration system has the advantages of high efficiency, energy saving, and low cost, and can play an important role in many fields, especially in low-altitude economy, intelligent transportation, UAV cooperative combat and other applications.

[0003] The communication module in the dual-base synaesthesia integrated system is responsible for the transmission and reception of wireless signals to ensure the efficient transmission of information; the perception module performs perception tasks such as target detection, positioning, and tracking by receiving parameters such as reflection information, delay, and frequency offset in the wireless signal. Since the communication and perception modules are usually implemented by different hardware platforms or subsystems, their working clocks may have deviations. This clock deviation may cause problems such as phase distortion and frequency drift of the signal in wireless communication; and in the perception process, it may lead to a reduction in the accuracy of target detection and positioning. Especially in a dynamic environment, the clock deviation may accumulate over time, further increase the system error, and affect the overall performance. The clock asynchronous problem is a key technical challenge faced by the dual-base synaesthesia integrated system, especially in the application of the dual-base system (i.e., different sources for sending and receiving). How to effectively synchronize the clocks of each base station and reduce the error accumulation caused by clock asynchronous is the key to improving the accuracy and reliability of the dual-base synaesthesia integrated system. Therefore, the present invention proposes a dual-base synaesthesia integrated clock synchronization algorithm based on the assistance of LoS reference path, which has strong performance and is easy to implement, making up for the shortcomings of existing research.

[0004] Through the above analysis, the problems and defects of the prior art are as follows:

[0005] (1) Since the communication and perception modules are usually implemented by different hardware platforms or subsystems, their working clocks may deviate. This clock deviation may cause signal phase distortion, frequency drift and other problems in wireless communication; in the perception process, it may lead to a decrease in target detection and positioning accuracy.

[0006] (2) Especially in dynamic environments, clock deviations may accumulate over time, further increasing system errors and affecting overall performance. Clock asynchrony is a key technical challenge faced by dual-base synaesthesia integrated systems, especially in dual-base systems (i.e., different sources for transmission and reception). How to effectively synchronize the clocks of each base station and reduce the error accumulation caused by clock asynchrony is the key to improving the accuracy and reliability of dual-base synaesthesia integrated systems. Summary of the invention

[0007] In view of the problems existing in the prior art, the present invention provides a dual-base ISAC clock synchronization algorithm design and system based on LoS reference path.

[0008] The present invention is implemented in such a way that a dual-base ISAC clock synchronization algorithm design based on a LoS reference path includes:

[0009] Step 1: Build a dual-base synaesthesia integrated system, where the transmitter and receiver are located at different locations and jointly perform detection tasks; in the collaborative detection scenario, establish the communication and perception signal transmission signal and channel model;

[0010] Step 2: Estimate the arrival angle of multipath signals based on the spatial smoothing MUSIC algorithm;

[0011] Step 3: Separate the multipath signals to obtain the target perception information contained in each path;

[0012] Step 4: By proposing a clock synchronization algorithm assisted by the LoS reference path, the problem of poor perception estimation accuracy caused by different transmitting and receiving sources in dual-base synaesthesia integration is solved.

[0013] Furthermore, the UAV adopts synaesthesia integrated multi-beam signaling, using fixed sub-beams to perform communication functions and scanning sub-beams to perform perception functions. represents the transmit beamforming vector, represents the phase shift vector, β R represents the power allocation factor, and They represent the beamforming vectors of the sensing and communication sub-beams respectively. The beamforming vector can be directly generated by the least squares method according to the task requirements.

[0014] Furthermore, this scenario has one base station and one detection drone, which perform dual-base synaesthesia integrated operation. The detection drone acts as the transmitting end of the air base station, and its transmission signal is received through the LoS and NLoS components. The LoS component mainly transmits communication signals, and the NLoS signal can be reflected by the surrounding black-flying drones for target perception.

[0015] Furthermore, the transmitting antennas all use uniform planar arrays to implement multi-beam design, and their transmitting signals can be expressed as x(t)=w t s(t), where represents the Orthogonal Frequency Division Multiplexing (OFDM) baseband signal, M and N represent the number of OFDM symbols and the number of subcarriers respectively, s m,n represents the baseband symbol of the mth OFDM symbol on the nth subcarrier, f c +nΔf represents the nth subcarrier frequency, Δf represents the subcarrier spacing, rect(x) represents the matrix function, T s Represents the symbol duration. Since the detection drone always works at a certain altitude, the LoS component between the detection drone and the base station must exist, and its channel can be written as in and Respectively represent the LoS component and NLoS component of the channel, K R represents the Ricean channel K factor, L represents the number of multipaths, β l , f l , τ l They represent the channel coefficient, Doppler frequency and delay of the l∈{0,1,2…,L}th path respectively. r,l and q t,l denote the angle of arrival and the angle of departure respectively. In addition, and They represent the fading coefficients of the LoS path and the NLoS path respectively, λ represents the wavelength of the signal, and d L Indicates the distance between the transmitter and the receiver of the LoS path, d NL,1 and d NL,2 They represent the distance between the transmitter and the reflector of the NLoS path and the distance between the reflector and the receiver, ρ l Represents the reflection coefficient.

[0016] The technical solution adopted by the present invention is: give a model of a dual-base synaesthesia integrated system; establish a synaesthesia integrated multi-beam model under the model; design a spatial smoothing MUSIC algorithm to estimate the target angle; propose a multipath separation algorithm to solve the problem of joint estimation of delay and Doppler frequency; design a clock synchronization algorithm based on the assistance of LoS reference path to solve the problem of clock asynchrony at the transmitting and receiving ends; perform data simulation and compare and analyze the results. Specifically, it includes the following steps:

[0017] S1. First, a model of a dual-base synaesthesia integrated system is given, and the detection UAV uses multi-beams to perform communication and perception functions.

[0018] S2. In the scenario of collaborative detection between the base station and the detection drone, establish the communication and perception signal transmission and reception and channel models.

[0019] S3. Since frequency offset and delay offset will not affect angle prediction, the spatial smoothing multiple signal classification (MUSIC) algorithm is used to estimate the multipath signal arrival angle. The specific steps are as follows:

[0020] A1. Will have The uniform planar array of antennas is divided into L x ×L y overlapping subarrays, each containing Antennas.

[0021] A2, No. x ,l y ) subarrays has a covariance matrix of Among them l x ∈[1,2,…,L x ],l y ∈[1,2,…,L y ], as well as

[0022] A3. Perform spatial smoothing in multiple subarrays, average multiple covariance matrices, and calculate the overall covariance matrix obtained by weighted average to obtain

[0023] A4. Calculate the eigenvalue decomposition of the covariance matrix based on the MUSIC algorithm where Λ h Represents the real-valued diagonal matrix of eigenvalues ​​in descending order, Q h represents the corresponding eigenvector. Its spectral function is Among them U N The matrix representing the noise subspace. The arrival angle of multipath signal is estimated by spectrum peak search.

[0024] S4. In order to obtain the perception information contained in each multipath signal, the corresponding receiving beamforming is designed based on the estimated arrival angle of the multipath signal to perform multipath separation. Indicates that K s The array corresponding matrix corresponding to the target direction can be obtained based on the least squares method. in Represents the array corresponding matrix After multipath separation, each path can be processed separately to obtain perception information. The specific steps are as follows:

[0025] A1. The channel estimation of the lth multipath signal is in Respectively represent the entire multipath channel estimation, the l-th multipath actual channel, and the l-th multipath channel estimation error. s After ×N channel estimation, its channel response matrix is ​​written as

[0026] A2. Rewrite the channel response matrix as in G l =β c,l χ t,l χ r,l ,as well as After vectorization, the channel response of the lth multipath signal is written as

[0027] A3. The covariance matrix of the lth multipath channel is

[0028] A4. Calculate the eigenvalue decomposition of the covariance matrix based on the MUSIC algorithm in represents a diagonal matrix of real values ​​of the eigenvalues ​​in descending order, represents the corresponding eigenvector. Its spectral function is in The matrix represents the noise subspace. The delay of multipath signal is estimated by spectrum peak search. With Doppler frequency

[0029] S5. Due to clock asynchrony, the estimated delay and Doppler frequency have errors. A clock synchronization algorithm based on the LoS reference path is proposed. According to the distance between the transmitter and the receiver, the propagation characteristics of the LoS signal are used to measure the signal delay and Doppler frequency, so as to accurately estimate the clock deviation between the transmitter and the receiver. Deviation from Doppler frequency Then the real time delay and Doppler frequency of the target can be obtained According to the triangulation positioning method, the transmitter and the receiver are the foci of the ellipse, and the propagation distance is the sum of the distances from any point on the ellipse to the foci. Combined with the multipath signal arrival angle estimation, the position of the target can be determined.

[0030] S6. Data simulation is performed based on the proposed algorithm to verify the effectiveness of the proposed algorithm under different signal-to-interference-noise ratios and different frequency offsets and time offsets. At the same time, it is compared with other basic algorithms to reflect the advantages of the algorithm in improving communication and perception performance.

[0031] In combination with the above technical solutions and the technical problems solved, please analyze the advantages and positive effects of the technical solutions to be protected by the present invention from the following aspects:

[0032] First, in view of the technical problems existing in the above-mentioned prior art and the difficulty of solving the problems, the technical solutions to be protected by the present invention and the results and data during the research and development process are closely combined to analyze in detail and deeply how the technical solutions of the present invention solve the technical problems, and some creative technical effects brought about after solving the problems. The specific description is as follows:

[0033] The present invention proposes a dual-base synaesthesia integrated clock synchronization algorithm based on the assistance of LoS reference path. By utilizing the propagation characteristics of LoS signals to measure the signal delay and Doppler frequency, the clock deviation and Doppler frequency deviation between the transmitter and the receiver are accurately estimated, the clock deviation compensation is dynamically adjusted, the error accumulation is reduced, and the perception accuracy and communication quality of the system are significantly improved.

[0034] First, the LoS reference path-assisted dual-base synaesthesia integrated clock synchronization algorithm of the present invention can effectively solve the error problem caused by clock asynchrony in the dual-base synaesthesia integrated system. Compared with the traditional synchronization method, the present invention can significantly reduce error accumulation and ensure the long-term stability and reliability of the system.

[0035] The method of the present invention has the following advantages:

[0036] 1. While performing clock synchronization, the present invention makes full use of the synergy of communication and perception signals to improve the perception accuracy of the dual-base system, especially in target positioning, detection and tracking. At the same time, by optimizing clock synchronization compensation, signal distortion and distortion are reduced, and the quality and stability of communication signals are improved.

[0037] 2. The present invention uses the spatial smoothing MUSIC algorithm to process the received signal and make a high-precision estimate of the arrival angle of multipath propagation in the communication and perception signals. By decomposing the signal covariance matrix of the receiving array, the multipath effect and interference in the channel are overcome and the direction information of each path is extracted.

[0038] 3. According to the AoA estimation result of the MUSIC algorithm, the present invention separates the received multipath signals and extracts the signal of each path from the mixed signal. For each separated path signal, the target perception information (such as target position, speed, and reflection intensity, etc.) contained in it is analyzed, and the characteristics of the line-of-sight (LoS) path signal are particularly concerned to provide key data support for subsequent clock synchronization.

[0039] 4. The proposed algorithm is applicable to the UAV dual-base synaesthesia integrated system under different signal-to-interference-noise ratios and different frequency offsets and time offsets. It has broad application value in many fields such as low-altitude economy, UAV collaborative detection, intelligent transportation, smart cities, etc.

[0040] Second, as auxiliary evidence of the inventiveness of the claims of the present invention, it is also reflected in the following important aspects:

[0041] (1) The expected benefits and commercial value of the technical solution of the present invention after transformation are:

[0042] The present invention effectively improves the accuracy of the perception function through the clock synchronization algorithm and multipath separation technology based on the LoS reference path. Especially in the scenes of low-altitude economy, drone detection, intelligent transportation, etc., the technology can significantly improve the detection, positioning and tracking effects of the target. The technology transformation of the present invention can not only bring significant economic benefits to enterprises and research institutions, but also promote the development of wireless communication and perception technology. It can be used as an innovative model in the field of synaesthesia integration, attract more research institutions and enterprises to participate in technology research and development, and promote innovation and collaboration in the upstream and downstream of the industrial chain. Its commercial value will be further improved with the rapid development of low-altitude economy, intelligent transportation and security markets, and become an important driving force for the commercialization of synaesthesia integration technology.

[0043] (2) The technical solution of the present invention fills the technical gap in the industry at home and abroad:

[0044] In the dual-base synaesthesia integrated system, since the transmitter and the receiver work independently and the clocks are not synchronized, it is difficult for conventional methods to achieve high-precision clock synchronization in dynamic environments and complex channel conditions. The present invention proposes a clock synchronization algorithm based on the assistance of the LoS reference path, which makes full use of the propagation characteristics of the LoS path, accurately measures the delay and dynamically adjusts the clock deviation compensation, thereby solving the perception error problem caused by clock asynchrony. Compared with traditional synchronization technology, the present invention achieves a double improvement in perception accuracy and communication performance. The spatial smoothing MUSIC algorithm is also used to estimate the arrival angle of multipath signals, and combined with high-precision multipath signal separation technology, the effective distinction and information extraction of LoS path and NLoS path are realized for the first time, providing a new solution for high-precision perception and synchronization in complex environments. The present invention combines the collaborative perception capability of dual-base synaesthesia integration with a high-precision clock synchronization algorithm, provides a new solution for key application scenarios in the low-altitude economy, and strongly promotes the development of technology in this field. These technical achievements effectively fill many gaps in synaesthesia integration technology at home and abroad, provide new theoretical basis and technical support for the further development of this field, and have important academic value and practical application significance.

[0045] (3) Whether the technical solution of the present invention solves the technical problems that people have been eager to solve but have not been able to solve successfully:

[0046] In the dual-base interaceptive integrated system, since the transmitter and the receiver operate independently and the clocks are not synchronized, the system is significantly limited in terms of perception accuracy and communication performance. Traditional synchronization methods cannot take into account the multipath propagation characteristics in complex environments and the real-time requirements of dynamic scenarios. Current research is mostly focused on centralized or single-base systems, and the dynamic and independent clock deviation processing solutions for dual-base systems are not yet mature, especially when LoS and NLoS signals are mixed, it is difficult to achieve high-precision synchronization. The present invention is the first to create a clock synchronization algorithm based on the assistance of the LoS reference path, making full use of the propagation characteristics of the LoS signal to measure the delay, combined with a dynamic clock deviation compensation strategy, to achieve high-precision synchronization under complex propagation conditions. This solution solves the long-standing problem of perception errors caused by clock asynchrony in dual-base systems. Through perfect algorithm design and actual verification, the present invention provides a standardized clock synchronization and perception solution for the dual-base interaceptive integrated system, which has high scalability and practical application value.

[0047] (4) Whether the technical solution of the present invention overcomes technical prejudice:

[0048] Some traditional studies believe that the clock synchronization problem in the dual-base synaesthesia integrated system can only be solved by high-precision external reference signals (such as the Global Positioning System (GPS)) or centralized control, ignoring the synchronization potential of the system's internal signals. The present invention uses a clock synchronization algorithm assisted by the LoS reference path to make full use of the propagation characteristics of the system's internal signals (LoS path) to achieve high-precision clock synchronization without the need for an external reference. This solution overcomes the reliance on centralized clock synchronization and improves the autonomy and flexibility of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 is a system model diagram provided by an embodiment of the present invention;

[0050] Figure 2 is a flow chart of an algorithm provided by an embodiment of the present invention;

[0051] Figure 3 This is a simulation diagram comparing the accuracy of the proposed algorithm in sensing distance and speed with changes in frequency offset and clock offset under different signal-to-interference-noise ratios provided by an embodiment of the present invention;

[0052] Figure 4 This is a simulation diagram comparing the accuracy of the proposed algorithm in sensing distance and speed with changes in frequency offset and clock offset under different signal-to-interference-noise ratios provided by an embodiment of the present invention;

[0053] Figure 5 This is a simulation diagram comparing the accuracy of the proposed algorithm and other basic algorithms in sensing distance under different signal to noise ratios provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0054] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0055] The technical problems of the prior art solved by the present invention and the significant technical progress achieved are mainly reflected in the following aspects:

[0056] Technical issues:

[0057] 1. Clock synchronization problem in dual-base system: In the dual-base synaesthesia integrated system, the transmitter and receiver work independently, resulting in clock asynchrony, which leads to the problem of reduced perception accuracy and impaired communication quality.

[0058] 2. Signal processing challenges in complex multipath environments: Existing technologies have difficulty separating and utilizing multipath signals in complex environments with significant multipath effects, especially the efficiency of distinguishing and processing LoS and NLoS signals is low.

[0059] 3. Optimization of communication and perception synergistic performance: In the synaesthesia integrated system, resource competition between communication and perception functions exists for a long time, making it difficult to achieve the optimal balance between the performance of the two.

[0060] Technological advancements:

[0061] 1. A dual-base synaesthesia integrated clock synchronization algorithm assisted by a LoS reference path is proposed: The present invention uses a clock synchronization algorithm assisted by a LoS reference path, utilizes the high stability and low latency characteristics of LoS signal propagation, accurately measures the clock deviation between the transmitter and the receiver, and dynamically adjusts the clock synchronization parameters of the system, thereby significantly improving the perception accuracy and communication performance.

[0062] 2. Breakthrough in signal processing difficulties in multipath environments: The present invention adopts a spatially smoothed MUSIC algorithm to perform high-precision estimation of the arrival angle of multipath signals, and combines it with multipath separation technology to effectively extract the target perception information contained in LoS and NLoS signals, thereby achieving high-precision perception and communication in complex environments.

[0063] 3. Realize the coordinated optimization of perception and communication functions: The present invention optimizes resource allocation by using LoS signals for clock synchronization and perception functions at the same time, realizes the coordinated work of communication and perception, and significantly improves the overall performance of the system.

[0064] 4. Data simulation verifies the effectiveness of the algorithm: This paper uses data simulation to verify the effectiveness of the proposed algorithm, proving the feasibility and superiority of the algorithm in practical applications.

[0065] In summary, the present invention successfully solves the key problems of clock asynchrony, complex and difficult multipath signal processing, and collaborative performance optimization in the prior art by proposing a dual-base synaesthesia integrated clock synchronization algorithm assisted by a LoS reference path, and achieves significant technical progress and application value.

[0066] Example: Illegal drone monitoring scenario in an urban environment

[0067] 1. In urban environments, due to dense buildings and complex signals, the monitoring task of illegal drones faces challenges. This embodiment designs a dual-base synaesthesia integrated illegal drone monitoring system that adapts to complex urban environments, which is used to perceive the location and flight path of illegal drones in real time and communicate and cooperate with other monitoring nodes. It is assumed that the monitoring range covers the airspace within a radius of 500 meters, the buildings are of different heights, and the interference signals are complex.

[0068] 2. Data collection: In an urban environment, transmitters and receivers are arranged at different heights and density areas to collect target reflection signals and environmental background signals. The system is operated under various weather conditions such as day and night, sunny and rainy, to collect multipath signal data under different postures, paths and speeds during the flight of illegal drones. The collected multipath signals are paired with the actual position of the drone to generate a labeled signal data set for subsequent algorithm training and verification.

[0069] 3. Use DeblurGANv2 model processing: Input the collected multipath signals into the improved DeblurGANv2 model, and deblur the reflected signals in complex environments to improve the quality of LoS and NLoS signals and reduce the impact of building reflections and multipath interference on monitoring accuracy. The deblurring weight file is obtained through training to improve the system's adaptability to LoS ​​signals and non-ideal signals in complex environments.

[0070] 4. Use the improved YOLOv7-tiny model: Based on the urban traffic environment, the improved YOLOv7-tiny model is used to optimize the multi-target detection of illegal drones, enhancing the system's ability to accurately detect illegal drones in complex urban environments, especially in high-rise building reflection signal interference and multi-target dynamic scenes, improving system robustness and detection accuracy. Within the monitoring range, the reflected signal is processed in real time and the illegal drone is quickly located, generating high-precision three-dimensional location information and flight trajectory.

[0071] 5. System deployment: Deploy the transmitter and receiver in the monitoring area, and set up a monitoring terminal to be responsible for the identification, tracking and information sharing of illegal drones.

[0072] This embodiment combines clock synchronization based on the LoS reference path, multipath signal defuzzification processing and an improved multi-target detection model, which significantly improves the perception accuracy and communication capability of the illegal drone monitoring system and provides a strong technical guarantee for airspace security in urban environments.

[0073] Figure 1 This is a system model diagram of the multi-beam dual-base synaesthesia integration of the present invention. Figure 1 As shown, the algorithm of the present invention is implemented based on the following system: the system scenario has 1 base station and 1 detection drone, and the two perform dual-base synaesthesia integration operation. The detection drone acts as the transmitting end of the aerial base station, and its transmission signal is received through the LoS and NLoS components. The LoS component mainly transmits communication signals, and the NLoS signal can be reflected by the surrounding unmanned aerial vehicles for target perception. The transmitting antennas all use uniform linear arrays to implement multi-beam design, and their transmission signals can be expressed as x(t)=w t s(t), where s(t) represents the baseband signal, represents the transmit beamforming vector, represents the phase shift vector, β R represents the power allocation factor, and Represent the beamforming vectors of the sensing and communication sub-beams respectively. By flexibly adjusting and β R , which can meet the needs of communication and perception at the same time.

[0074] Figure 2 The algorithm flow chart of the present invention is as follows:

[0075] A1. Construct a dual-base interaceptive integrated system, where the transmitter and receiver are located at different locations and jointly perform detection tasks; in the collaborative detection scenario, establish the communication and perception signal transmission signal and channel model;

[0076] A2. Estimate the arrival angle of multipath signals according to the spatial smoothing MUSIC algorithm. The specific steps are as follows:

[0077] A21. Will have The uniform planar array of antennas is divided into L x ×L y overlapping subarrays, each containing Antennas.

[0078] A22, No.x ,l y ) subarrays has a covariance matrix of Among them l x ∈[1,2,…,L x ],l y ∈[1,2,…,L y ], as well as

[0079] A23, perform spatial smoothing in multiple subarrays, average multiple covariance matrices, and obtain the overall covariance matrix obtained by calculating the weighted average

[0080] A24. Calculate the eigenvalue decomposition of the covariance matrix according to the MUSIC algorithm where Λ h Represents the real-valued diagonal matrix of eigenvalues ​​in descending order, Q h represents the corresponding eigenvector. Its spectral function is Among them U N The matrix representing the noise subspace. The arrival angle of multipath signal is estimated by spectrum peak search.

[0081] A3. Separate the multipath signals to obtain the target perception information contained in each path. The specific steps are as follows:

[0082] A31, the channel estimation of the lth multipath signal is in Respectively represent the entire multipath channel estimation, the l-th multipath actual channel, and the l-th multipath channel estimation error. s After ×N channel estimation, its channel response matrix is ​​written as

[0083] A32. Rewrite the channel response matrix as in G l =β c,l χ t,l χ r,l ,as well as After vectorization, the channel response of the lth multipath signal is written as

[0084] A33, the covariance matrix of the l-th multipath channel is

[0085] A34. Calculate the eigenvalue decomposition of the covariance matrix according to the MUSIC algorithm in represents a diagonal matrix of real values ​​of the eigenvalues ​​in descending order, represents the corresponding eigenvector. Its spectral function is in The matrix represents the noise subspace. The delay of multipath signal is estimated by spectrum peak search. With Doppler frequency

[0086] A4, based on the distance between the transmitter and the receiver, uses the propagation characteristics of the LoS signal to measure the signal delay and Doppler frequency, thereby accurately estimating the clock deviation between the transmitter and the receiver Deviation from Doppler frequency Then the real time delay and Doppler frequency of the target can be obtained According to the triangulation positioning method, the transmitter and the receiver are the foci of the ellipse, and the propagation distance is the sum of the distances from any point on the ellipse to the foci. Combined with the multipath signal arrival angle estimation, the position of the target can be determined.

[0087] In the simulation process of the present invention, it is assumed that the base station and the detection drone jointly perform the dual-base synaesthesia integration task, realize communication cooperation while monitoring illegal drones, and the flight range of the detection drone covers the airspace within a radius of 500 meters, and the flight is controlled by the base station. The specific process is as follows:

[0088] Figure 3 and Figure 4 The simulation diagram shows the comparison of the accuracy of the proposed algorithm in sensing distance and speed under different signal-to-interference-noise ratios as the frequency offset and clock offset change. Figure 3 and Figure 4 It can be seen that the accuracy of the traditional algorithm in sensing distance and speed is seriously affected by frequency offset and clock offset. The algorithm proposed in the present invention can effectively solve the problem of low estimation accuracy caused by asynchrony of the transmitting and receiving ends, and can improve the overall performance of the system.

[0089] Figure 5 The simulation diagram shows the comparison of the proposed algorithm and other basic algorithms in the accuracy of sensing distance under different signal-to-interference-noise ratios; the implementation of other basic algorithms is as follows: Cross-Antenna Cross-Correlation (CACC), Cross-Antenna Signal Ratio (CASR), Cramer-Rao Bound (CRB). Figure 5It can be seen that although CACC / CASR can alleviate the influence of time offset and carrier frequency offset to a certain extent, additional processing is required to solve the range ambiguity problem. The LoS Aided Offset Mitigation (LAOM) algorithm proposed in the present invention can effectively alleviate the influence of time offset and carrier frequency offset.

[0090] It should be noted that the embodiments of the present invention can be implemented by hardware, software, or a combination of software and hardware. The hardware part can be implemented using dedicated logic; the software part can be stored in a memory and executed by an appropriate instruction execution system, such as a microprocessor or dedicated design hardware. It can be understood by a person of ordinary skill in the art that the above-mentioned devices and methods can be implemented using computer executable instructions and / or contained in a processor control code, such as a carrier medium such as a disk, CD or DVD-ROM, a programmable memory such as a read-only memory (firmware), or a data carrier such as an optical or electronic signal carrier. Such code is provided on the carrier medium. The device and its modules of the present invention can be implemented by hardware circuits such as very large-scale integrated circuits or gate arrays, semiconductors such as logic chips, transistors, etc., or programmable hardware devices such as field programmable gate arrays, programmable logic devices, etc., can also be implemented by software executed by various types of processors, and can also be implemented by a combination of the above-mentioned hardware circuits and software, such as firmware.

[0091] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any modifications, equivalent substitutions and improvements made by any technician familiar with the technical field within the technical scope disclosed by the present invention and within the spirit and principle of the present invention should be covered by the protection scope of the present invention.

Claims

1. A design of a dual-base ISAC clock synchronization algorithm based on LoS reference path, characterized in that: The dual-base synaesthesia integrated system includes a transmitter and a receiver, which are located in different locations. The transmitter not only undertakes the communication task but also provides perception information to the receiver by sending signals with specific coding or modulation. After the signal is transmitted, the receiver receives and processes the reflected signals from different targets or environments. The receiver perceives the target based on these reflected signals. The signal delay is measured through the propagation characteristics of the LoS signal, and the signal delay is used to estimate the clock deviation between the transmitter and the receiver, thereby improving the perception accuracy; data simulation is used to verify the effectiveness of the proposed algorithm.

2. The design of a dual-base ISAC clock synchronization algorithm based on a LoS reference path as claimed in claim 1, characterized in that: This scenario has one base station and one detection drone, which perform dual-base synaesthesia integrated operation. The detection drone acts as the transmitting end of the air base station, and its transmission signal is received through LoS and NLoS components. The LoS component mainly transmits communication signals, and the NLoS signal can be reflected by surrounding illegal drones for target perception.

3. The design of a dual-base ISAC clock synchronization algorithm based on a LoS reference path as claimed in claim 2, characterized in that: The transmitting antennas all use uniform planar arrays to implement multi-beam design, and their transmitted signals can be expressed as x(t)=w t s(t), where represents the Orthogonal Frequency Division Multiplexing (OFDM) baseband signal, M and N represent the number of OFDM symbols and the number of subcarriers respectively, s m,n represents the baseband symbol of the mth OFDM symbol on the nth subcarrier, f c +nΔf represents the nth subcarrier frequency, Δf represents the subcarrier spacing, rect(x) represents the matrix function, T s Indicates the duration of the symbol; represents the transmit beamforming vector, represents the phase shift vector, β R represents the power allocation factor, and They represent the beamforming vectors of the sensing and communication sub-beams respectively; the beamforming vector can be directly generated using the least squares method according to task requirements.

4. The design of a dual-base ISAC clock synchronization algorithm based on a LoS reference path as claimed in claim 3, characterized in that: Since the detection drone always works at a certain altitude, there must be a LoS component between the detection drone and the base station, and its channel can be written as in and Respectively represent the LoS component and NLoS component of the channel, K R represents the Ricean channel K factor, L represents the number of multipaths, β l , f l , τ l They represent the channel coefficient, Doppler frequency and delay of the l∈{0,1,2…,L}th path respectively; q r,l and q t,l denote the angle of arrival and the angle of departure respectively; in addition, and They represent the fading coefficients of the LoS path and the NLoS path respectively, λ represents the wavelength of the signal, and d L Indicates the distance between the transmitter and the receiver of the LoS path, d NL,1 and d NL,2 They represent the distance between the transmitter and the reflector of the NLoS path and the distance between the reflector and the receiver, ρ l Represents the reflection coefficient; for A uniform planar array of antennas with an angle of arrival / departure of The array steering vector is in and Respectively represent the angle between the direct signal and the coordinate axis x, y, θ k and represent the elevation and horizontal angles of the incident angle respectively.

5. The design of a dual-base ISAC clock synchronization algorithm based on a LoS reference path as claimed in claim 4, characterized in that: To estimate the target perception information under the NLoS path, we first use the least squares method to perform channel estimation; the estimated channel for the mth OFDM packet on the nth subcarrier is where h n,m is the real channel state information, χ t,k =α T (q t,l ) t represents the transmit beamforming gain, f l e =f l +f off and denote the Doppler frequency and delay of the lth path, z n,m,h represents Gaussian noise; in addition, f l , f off , τ l and τ off They represent the true Doppler frequency, frequency offset, true delay and delay offset respectively. Due to the influence of frequency offset and delay offset, target perception information cannot be obtained directly.

6. The design of a dual-base ISAC clock synchronization algorithm based on a LoS reference path as claimed in claim 5, characterized in that: Since frequency offset and delay offset do not affect angle prediction, the spatial smoothing multiple signal classification (MUSIC) algorithm is used to estimate the arrival angle of multipath signals. The specific steps are as follows: A1. Will have The uniform planar array of antennas is divided into L x ×L y overlapping subarrays, each containing antennas; A2, No. x ,l y ) subarrays has a covariance matrix of Among them l x ∈[1,2,…,L x ],l y ∈[1,2,…,L y ], as well as A3. Perform spatial smoothing in multiple subarrays, average multiple covariance matrices, and calculate the overall covariance matrix obtained by weighted average to obtain A4. Calculate the eigenvalue decomposition of the covariance matrix based on the MUSIC algorithm where Λ h Represents the real-valued diagonal matrix of eigenvalues ​​in descending order, Q h represents the corresponding eigenvector; its spectral function is Among them U N A matrix representing the noise subspace; the arrival angle of multipath signals is estimated by spectrum peak search.

7. The design of a dual-base ISAC clock synchronization algorithm based on a LoS reference path as claimed in claim 6, characterized in that: In order to obtain the perceptual information contained in each multipath signal, the corresponding receiving beamforming is designed based on the estimated arrival angle of the multipath signal to perform multipath separation. Indicates that K s The array corresponding matrix corresponding to the target direction can be obtained based on the least squares method. in Represents the array corresponding matrix The pseudo-inverse.

8. The design of a dual-base ISAC clock synchronization algorithm based on a LoS reference path as claimed in claim 7, characterized in that: After multipath separation, each path can be processed separately to obtain perception information. The specific steps are as follows: A1. The channel estimation of the lth multipath signal is in Respectively represent the entire multipath channel estimation, the l-th multipath actual channel, and the l-th multipath channel estimation error; after M s After ×N channel estimation, its channel response matrix is ​​written as A2. Rewrite the channel response matrix as in G l =b c,l x t,l x r,l , as well as After vectorization, the channel response of the lth multipath signal is written as A3. The covariance matrix of the lth multipath channel is A4. Calculate the eigenvalue decomposition of the covariance matrix based on the MUSIC algorithm in represents a diagonal matrix of real values ​​of the eigenvalues ​​in descending order, represents the corresponding eigenvector; its spectral function is in Matrix representing the noise subspace; Estimate the delay of multipath signals by spectral peak search With Doppler frequency f l e .

9. The design of a dual-base ISAC clock synchronization algorithm based on a LoS reference path as claimed in claim 8, characterized in that: Due to clock asynchrony, there are errors in the estimated delay and Doppler frequency. A clock synchronization algorithm based on the assistance of LoS reference path is proposed. According to the distance between the transmitter and the receiver, the propagation characteristics of the LoS signal are used to measure the signal delay and Doppler frequency, so as to accurately estimate the clock deviation between the transmitter and the receiver. Deviation from Doppler frequency Then the real time delay and Doppler frequency of the target can be obtained f l =f l e -f off According to the triangulation positioning method, the transmitting end and the receiving end are the foci of the ellipse, and the propagation distance is the sum of the distances from any point on the ellipse to the foci. Combined with the estimation of the arrival angle of the multipath signal, the position of the target can be determined.

10. The design of a dual-base ISAC clock synchronization algorithm based on a LoS reference path as claimed in claim 8, characterized in that: The transmitter and receiver are located at different locations and jointly perform detection tasks; in the collaborative detection scenario, the communication and perception signal transmission signals and channel models are established; Estimate the arrival angle of multipath signals based on the spatially smoothed MUSIC algorithm; Separate multipath signals to obtain target perception information contained in each path; By proposing a clock synchronization algorithm assisted by LoS reference path, the problem of poor perception estimation accuracy caused by different transmitting and receiving sources in dual-base synaesthesia integration is solved.

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