A LoS reference path-based double-base ISAC clock synchronization algorithm design and system

Abstract

The application belongs to the technical field of unmanned aerial vehicle communication and sensing integration, and discloses a double-base ISAC clock synchronization algorithm design and system based on LoS reference path, aiming to solve the measurement error problem caused by clock asynchrony of the transmitting end and the receiving end. The receiving end receives communication signals based on the LoS path and sensing signals based on the non-line-of-sight (NLoS) path through the communication and sensing integrated design. The application proposes a clock synchronization algorithm based on LoS reference path assistance, measures the time delay and Doppler frequency of the signal by using the propagation characteristics of the LoS signal, and accurately estimates the clock deviation and Doppler frequency deviation. The algorithm combines communication and sensing signals, dynamically adjusts and compensates the clock deviation of the receiving end, reduces the accumulation of asynchronous errors, and significantly improves the sensing accuracy and system performance. The simulation results show that the method effectively enhances the communication and sensing functions of the system in low-altitude economic application scenarios.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of unmanned aerial vehicle communication and perception integration, and particularly relates to a double-base ISAC clock synchronization algorithm design and system based on a LoS reference radius. BACKGROUND

[0002] Double-base communication and perception integration technology is an emerging wireless communication technology, and 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. In such a system, communication signals are not only used for data transmission, but also provide real-time environmental information for the perception system, such as the position, speed, direction, etc. of the target. Therefore, the double-base communication and perception 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, unmanned aerial vehicle cooperative combat, etc.

[0003] The communication module in the double-base communication and perception integration system is responsible for the transmission and reception of wireless signals to ensure efficient transmission of information; the perception module receives reflected information, time delay, frequency offset, etc. in the wireless signal to perform target detection, positioning, tracking, etc. perception tasks. Since the communication and perception modules are usually implemented by different hardware platforms or subsystems, their working clocks may have deviations. Such clock deviations may cause phase distortion, frequency drift, etc. in wireless communication; and in the perception process, it may lead to a decrease in target detection and positioning accuracy. Especially in a dynamic environment, clock deviations may accumulate over time, further increasing system errors and affecting overall performance. Clock asynchronization is a key technical challenge faced by double-base communication and perception integration systems, especially in double-base system (i.e. different sources of transmission and reception) applications. How to effectively synchronize the clocks of each base station and reduce the error accumulation caused by clock asynchronization is the key to improving the accuracy and reliability of double-base communication and perception integration systems. Therefore, the application proposes a double-base communication and perception integration clock synchronization algorithm based on LoS reference radius assistance, which is easy to implement and compensates for the shortcomings of existing research.

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

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

[0006] (2) Especially in dynamic environments, clock deviations can accumulate over time, further increasing system errors and impacting overall performance. Clock asynchrony is a key technical challenge facing dual-base synaesthesia systems, especially in dual-base systems (i.e., where the transmitter and receiver have different sources). Effectively synchronizing the clocks of each base station and reducing the error accumulation caused by clock asynchrony is key to improving the accuracy and reliability of dual-base synaesthesia 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 as follows: a bistatic ISAC clock synchronization algorithm design based on a LoS reference path includes:

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

[0010] Step 2: Estimate the arrival angle of multipath signals using the spatially smoothed 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 based on the assistance of 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 offset vector, β R represents the power allocation factor, and They represent the beamforming vectors of the sensing and communication sub-beams respectively. The beamforming vectors can be directly generated using the least squares method according to the task requirements.

[0014] Furthermore, this scenario features a base station and a detection drone, both of which perform dual-base synaesthesia operations. The detection drone acts as the transmitter for the airborne base station, and its transmitted signals are received via both LoS and NLoS components. The LoS component primarily transmits communication signals, while the NLoS signal, reflected by nearby unauthorized drones, enables target detection.

[0015] Furthermore, the transmitting antennas all adopt uniform planar arrays to realize 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 height, the LoS component between the detection drone and the base station must exist, and its channel can be written as in and Represent the LoS component and NLoS component of the channel respectively, K R represents the Rice 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 arrival angle and departure angle respectively. In addition, and They represent the fading coefficients of the LoS path and the NLoS path, 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 and the distance between the reflector and the receiver of the NLoS path, ρ l Represents the reflection coefficient.

[0016] The technical solution adopted by the present invention is as follows: a model of a bistatic synaesthesia integrated system is given; a synaesthesia integrated multi-beam model is established under this model; a spatially smoothed MUSIC algorithm is designed to estimate the target angle; a multipath separation algorithm is proposed to solve the problem of jointly estimating time delay and Doppler frequency; a clock synchronization algorithm based on the assistance of the LoS reference path is designed to solve the problem of clock asynchrony between the transmitter and receiver; and data simulation is performed to compare and analyze the results. Specifically, the following steps are included:

[0017] S1. First, a model of a dual-base synaesthesia integrated system is given, where the detection UAV uses multiple 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 do 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. (1 x ,l y The covariance matrix of the subarrays is where 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 using 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 is used to estimate the arrival angle of multipath signals by searching for spectral peaks.

[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 in K s The array 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 the 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 lth multipath actual channel, and the lth 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 using the MUSIC algorithm in represents the real-valued diagonal matrix of eigenvalues ​​in descending order, Represents the corresponding eigenvector. Its spectral function is in The matrix representing the noise subspace. The time delay of the multipath signal is estimated by searching the spectrum peak. and 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, thereby accurately estimating the clock deviation between the transmitter and the receiver. Doppler frequency deviation Then the real time delay and Doppler frequency of the target can be obtained According to the triangulation positioning method, the transmitter and receiver are the foci of the ellipse, and the propagation distance is the sum of the distances between any point on the ellipse and the foci. Combined with the multipath signal arrival angle estimation, the target position can be determined.

[0030] S6. Perform data simulation based on the proposed algorithm to verify the effectiveness of the proposed algorithm under different signal-to-interference-and-noise ratios and different frequency offsets and time offsets. At the same time, compare it with other basic algorithms to demonstrate 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 these problems, this paper closely combines the technical solutions to be protected by the present invention and the results and data during the research and development process, and analyzes in detail and in depth how the technical solutions of the present invention solve the technical problems and some creative technical effects brought about by solving the problems. The specific description is as follows:

[0033] The present invention proposes a bistatic 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 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 present invention's LoS reference-assisted, bistatic-synaesthesia-integrated clock synchronization algorithm effectively addresses the error problem caused by clock asynchrony in bistatic-synaesthesia-integrated systems. Compared to traditional synchronization methods, this method significantly reduces error accumulation, ensuring the long-term stability and reliability of the system.

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

[0036] 1. This invention leverages the synergy of communication and perception signals while simultaneously performing clock synchronization, improving the perception accuracy of dual-base systems. This has significant advantages, particularly in target positioning, detection, and tracking. Furthermore, by optimizing clock synchronization compensation, signal distortion and aberration are reduced, improving the quality and stability of communication signals.

[0037] 2. This invention uses a spatially smoothed MUSIC algorithm to process received signals, providing high-precision estimates of the angle of arrival of multipath propagation in communication and perception signals. By decomposing the signal covariance matrix of the receiving array, it overcomes multipath effects and interference in the channel and extracts the directional information of each path.

[0038] 3. Based on the AoA estimation results of the MUSIC algorithm, this invention separates the received multipath signals and extracts the signals of each path from the mixed signal. For each separated path signal, the target perception information contained in it (such as target position, speed, and reflection intensity) is analyzed, with particular attention paid to the characteristics of line-of-sight (LoS) path signals, providing 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 for 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 a clock synchronization algorithm and multipath separation technology based on the assistance of the LoS reference path. Especially in scenarios such as low-altitude economy, drone detection, and intelligent transportation, this 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 serve 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 enhanced with the rapid development of the low-altitude economy, intelligent transportation, and security markets, becoming 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 a dual-base interawareness integrated system, conventional methods struggle to achieve high-precision clock synchronization in dynamic environments and complex channel conditions because the transmitter and receiver operate independently and their clocks are asynchronous. This paper proposes a clock synchronization algorithm assisted by a LoS reference path. This algorithm leverages the propagation characteristics of the LoS path to accurately measure delays and dynamically adjust clock deviation compensation, thereby addressing the perception errors caused by clock asynchrony. Compared to traditional synchronization technologies, this paper achieves improvements in both perception accuracy and communication performance. It also utilizes a spatially smoothed MUSIC algorithm to estimate the angle of arrival of multipath signals, and combined with high-precision multipath signal separation techniques, effectively distinguishes and extracts information from LoS and NLoS paths for the first time, providing a novel solution for high-precision perception and synchronization in complex environments. Combining the collaborative perception capabilities of dual-base interawareness integration with a high-precision clock synchronization algorithm, this paper offers a novel solution for key application scenarios in the low-altitude economy, significantly advancing technological development in this field. These technical achievements effectively fill several gaps in interawareness integration technology both domestically and internationally, providing new theoretical foundations and technical support for further development in this field, and possessing significant 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 a dual-base interawareness integrated system, the system is significantly limited in terms of perception accuracy and communication performance because the transmitter and receiver operate independently and their clocks are not synchronized. 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. Dynamic and independent clock deviation processing solutions for dual-base systems are not yet mature, especially when LoS and NLoS signals are mixed, making it difficult to achieve high-precision synchronization. The present invention is the first to create a clock synchronization algorithm assisted by the LoS reference path, making full use of the propagation characteristics of the LoS signal to measure the delay, and combining it 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 error caused by clock asynchrony in dual-base systems. Through perfect algorithm design and practical verification, the present invention provides a standardized clock synchronization and perception solution for dual-base interawareness integrated systems, 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 have argued that clock synchronization in dual-base synaesthesia systems can only be solved using 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. This invention, through a clock synchronization algorithm assisted by a LoS reference path, fully leverages the propagation characteristics of the system's internal signals (LoS paths) to achieve high-precision clock synchronization without an external reference. This solution overcomes the reliance on centralized clock synchronization and enhances the system's autonomy and flexibility. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0050] Figure 2 It 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 distance and speed perception of the proposed algorithm under different signal-to-interference-noise ratios as frequency offset and clock offset change, as provided by an embodiment of the present invention.

[0052] Figure 4 This is a simulation diagram comparing the accuracy of distance and speed perception of the proposed algorithm under different signal-to-interference-noise ratios as frequency offset and clock offset change, as 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-interference-noise ratios provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0054] In order to make the purpose, technical solutions 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 intended 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 issues in dual-base systems: In dual-base integrated telepathy systems, the transmitter and receiver operate independently, resulting in clock asynchrony. This leads to 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. In particular, the efficiency of distinguishing and processing LoS and NLoS signals is low.

[0059] 3. Optimization of communication and perception synergy performance: In the integrated synaesthesia 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 both.

[0060] Technological advancements:

[0061] 1. Propose a LoS reference path-assisted dual-base synaesthesia integrated clock synchronization algorithm: This invention uses a clock synchronization algorithm based on the LoS reference path to take advantage of the high stability and low latency characteristics of LoS signal propagation, accurately measure the clock deviation between the transmitter and receiver, and dynamically adjust the system's clock synchronization parameters, thereby significantly improving perception accuracy and communication performance.

[0062] 2. Overcoming signal processing challenges in multipath environments: This invention uses a spatially smoothed MUSIC algorithm to perform high-precision estimation of the arrival angle of multipath signals. Combined with multipath separation technology, it effectively extracts 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: By using LoS signals for both clock synchronization and perception functions, the present invention optimizes resource allocation, 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 proposes a LoS reference path-assisted dual-base synaesthesia integrated clock synchronization algorithm, which successfully solves key problems in the existing technology, such as clock asynchrony, complex and difficult multipath signal processing, and collaborative performance optimization, and achieves significant technological progress and application value.

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

[0067] 1. In urban environments, monitoring illegal drones presents challenges due to dense buildings and complex signal processing. This embodiment designs a dual-base, integrated, synaesthesia-based illegal drone monitoring system adapted to complex urban environments. This system is used to perceive the location and flight path of illegal drones in real time and communicate with other monitoring nodes. The monitoring range is assumed to cover an airspace within a 500-meter radius, with varying building heights and complex interference signals.

[0068] 2. Data Collection: Transmitters and receivers are deployed in urban environments at varying heights and densities to collect target reflection signals and ambient background signals. The system operates under various weather conditions, including daytime and nighttime, sunny and rainy, to collect multipath signal data from illegal drones at different flight attitudes, paths, and speeds. The collected multipath signals are paired with the actual drone locations to generate a labeled signal dataset for subsequent algorithm training and validation.

[0069] 3. Processing using the DeblurGANv2 model: The collected multipath signals are fed into the improved DeblurGANv2 model. By deblurring reflected signals in complex environments, the quality of LoS and NLoS signals is improved, and the impact of building reflections and multipath interference on monitoring accuracy is reduced. The deblurring weight file is generated through training, improving the system's adaptability to LoS ​​signals and non-ideal signals in complex environments.

[0070] 4. Using an improved YOLOv7-tiny model: This model optimizes multi-target detection of illegal drones in urban traffic environments. This enhances the system's ability to accurately detect illegal drones in complex urban environments, particularly in situations with interference from reflected signals from high-rise buildings and in dynamic, multi-target scenarios. This improves system robustness and detection accuracy. Within the monitoring range, the system processes reflected signals in real time and rapidly locates illegal drones, generating highly accurate three-dimensional position information and flight paths.

[0071] 5. System deployment: Deploy transmitters and receivers within the monitoring area, and set up monitoring terminals to identify, track, and share information on 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, significantly improving the perception accuracy and communication capabilities of the illegal drone monitoring system, and providing strong technical support 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 one base station and one detection drone, and the two perform dual-base synaesthesia integration operation. The detection drone serves 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 is reflected by the surrounding unmanned aerial vehicles to perform 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 offset 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. Build a dual-base interaceptive integrated system, with the transmitter and receiver located in different locations, to jointly perform detection tasks. In a collaborative detection scenario, establish communication and perception signal transmission and channel models.

[0076] A2. Estimate the arrival angle of multipath signals using the spatially smoothed 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. (1x ,l y The covariance matrix of the subarrays is where 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 calculate the overall covariance matrix obtained by weighted average to obtain

[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 is used to estimate the arrival angle of multipath signals by searching for spectral peaks.

[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 lth multipath actual channel, and the lth 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 the real-valued diagonal matrix of eigenvalues ​​in descending order, Represents the corresponding eigenvector. Its spectral function is in The matrix representing the noise subspace. The time delay of the multipath signal is estimated by searching the spectrum peak. and 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. Doppler frequency deviation Then the real time delay and Doppler frequency of the target can be obtained According to the triangulation positioning method, the transmitter and receiver are the foci of the ellipse, and the propagation distance is the sum of the distances between any point on the ellipse and the foci. Combined with the multipath signal arrival angle estimation, the target position can be determined.

[0087] In the simulation process of this invention, it is assumed that the base station and the detection drone jointly perform the dual-base synergy integration task, realizing communication cooperation while monitoring illegal drones. The detection drone's flight range covers the airspace within a radius of 500 meters and 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 As can be seen in Figure 2, the accuracy of distance and speed perception by traditional algorithms is severely affected by frequency offset and clock offset. The algorithm proposed in this paper can effectively solve the problem of low estimation accuracy caused by asynchrony between the transmitter and receiver, 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 distance perception 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 5As can be seen in Figure 2, while CACC / CASR can mitigate the effects of time offset and carrier frequency offset to a certain extent, additional processing is required to resolve range ambiguity. The LoS Aided Offset Mitigation (LAOM) algorithm proposed in this paper can effectively mitigate the effects 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 portion can be implemented using dedicated logic; the software portion can be stored in a memory and executed by an appropriate instruction execution system, such as a microprocessor or dedicated design hardware. Those skilled in the art will appreciate that the above-mentioned devices and methods can be implemented using computer-executable instructions and / or contained in processor control code, for example, 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. The devices and 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, 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, or can be implemented by a combination of the above-mentioned hardware circuits and software, such as firmware.

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

Claims

1. A dual-base ISAC clock synchronization method based on a LoS reference path, characterized in that: The dual-base synaesthesia system consists of a transmitter and a receiver, which are located in different locations. The transmitter transmits signals with specific coding or modulation, which not only performs communication tasks but also provides perception information to the receiver. After the signal is transmitted, the receiver receives and processes the reflected signals from different targets or environments. The receiver then senses the target based on these reflected signals. The signal delay is measured by the propagation characteristics of the LoS signal and used to estimate the clock offset between the transmitter and receiver, thereby improving perception accuracy. Use data simulation to verify the effectiveness of the proposed algorithm; The measurement scenario consists of a base station and a detection drone, which perform dual-base synergy operations. The detection drone acts as the transmitter of the airborne base station, and its transmitted signal is received via LoS and NLoS components. The LoS component mainly transmits communication signals, while the NLoS signal can be reflected by surrounding unmanned aerial vehicles for target perception. In order to estimate the target perception information under the NLoS path, the least square method is first used to perform channel estimation; the estimated channel for the mth OFDM data packet on the nth subcarrier is where h n,m is the real channel state information, χ t,k =α T (q t,l )w 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 directly obtained. 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. Based on 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, thereby accurately estimating the clock deviation between the transmitter and the receiver. Doppler frequency deviation Then obtain the real time delay and Doppler frequency of the target According to the triangulation positioning method, the transmitter and receiver are the foci of the ellipse, and the propagation distance is the sum of the distances between any point on the ellipse and the foci. Combined with the multipath signal arrival angle estimation, the target position can be determined.

2. The bistatic ISAC clock synchronization method based on the LoS reference path according to claim 1, wherein: 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 offset vector, β R represents the power allocation factor, and They represent the beamforming vectors of the perception and communication sub-beams respectively; the beamforming vectors can be directly generated using the least squares method according to task requirements.

3. The bistatic ISAC clock synchronization method based on the LoS reference path according to claim 2, wherein: Since the detection drone always works at a certain height, the LoS component between the detection drone and the base station must exist, and its channel can be written as in and Represent the LoS component and NLoS component of the channel respectively, K R represents the Ricean channel K factor, L represents the number of multipaths, f0 and τ0 represent the Doppler frequency and delay of the LoS path respectively, and f l , τ l They represent the Doppler frequency and delay of the NLoS path respectively; q r,l and q t,l denote the arrival angle and departure angle respectively; in addition, and They represent the fading coefficients of the LoS path and the NLoS path, 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 and the distance between the reflector and the receiver of the NLoS path, 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 angles between the direct signal and the coordinate axes x and y, θ k and represent the elevation and horizontal angles of the incident angle, respectively.

4. The bistatic ISAC clock synchronization method based on the LoS reference path according to claim 1, wherein: Since frequency offset and delay offset do 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: A1. Will have The uniform planar array of antennas is divided into L x ×L y overlapping subarrays, each containing antennas; A2, No. (1 x ,l y The covariance matrix of the subarrays is where 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 using 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 spectral peak search.

5. The bistatic ISAC clock synchronization method based on the LoS reference path according to claim 4, wherein: In order to obtain the perceptual information contained in each multipath signal, the corresponding receiving beamforming is designed based on the estimated multipath signal arrival angle to perform multipath separation. Indicates that in K s The corresponding array matrix in the target direction can be obtained based on the least squares method. in Represents the array corresponding matrix Pseudo-reversal.

6. The bistatic ISAC clock synchronization method based on the LoS reference path according to claim 5, wherein: 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 lth multipath actual channel, and the lth 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 =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 A3. The covariance matrix of the lth multipath channel is A4. Calculate the eigenvalue decomposition of the covariance matrix using the MUSIC algorithm in represents the real-valued diagonal matrix of eigenvalues ​​in descending order, represents the corresponding eigenvector; its spectral function is in Matrix representing the noise subspace; Estimate the time delay of multipath signals by searching for spectral peaks and Doppler frequency f l e .

7. The bistatic ISAC clock synchronization method based on the LoS reference path according to claim 6, wherein: 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 signal and channel model 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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