A terahertz and low-frequency cooperative communication integrated beam management method

Abstract

The application provides a terahertz and low-frequency cooperative communication sensing integrated beam management method, uses the communication sensing integrated technology ISAC to realize positioning and user tracking, and further assists terahertz beam alignment, and realizes efficient seamless beam switching in a terahertz cell, between terahertz cells and between terahertz-low-frequency frequency bands. First, the coarse sensing user position detection of the low frequency is used, under the premise that the user position is determined by the coarse sensing, only the high frequency is used for fine scanning in a specific area, user speed estimation and switching type decision determination can significantly reduce the overhead, while ensuring the accuracy and effectiveness of the beam switching. To balance the high overhead caused by frequent transmission signaling and the not timely sensing information update caused by insufficient signaling transmission, the problem of ineffective switching is solved. The application further designs a synchronization signal block SSB period, which can simultaneously meet the measurable speed demand, the beam alignment capability demand and the coverage range demand.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of wireless communication, in particular to a beam management technology suitable for a wireless mobile network coexisting with a Terahertz and a Sub-6GHz frequency band. BACKGROUND

[0002] Future 6G networks aim to support new applications such as intelligent transportation and low-altitude economy, which require high data transmission rates and accurate perception. Existing frequency bands are difficult to support huge data throughput and accurate perception positioning, so wireless communication is developing towards higher unexplored frequency bands. The Terahertz frequency band with ultra-wide bandwidth is considered as a key technology to achieve Tera-bps data transmission rate and millimeter-level perception resolution. However, Terahertz communication faces serious path loss and Line-of-Sight (LoS) blockage challenges, limiting network coverage. Current communication standards allow multiple frequency bands to coexist, i.e., Dual-Connectivity (DC) technology. DC allows users to connect to two different frequency bands at the same time, such as Terahertz and Sub-6GHz frequency bands. The Sub-6GHz frequency band is a low frequency relative to the Terahertz. Compared with independent Terahertz communication, DC provides a stable Sub-6GHz link to improve network coverage, but the Terahertz and low frequency coexistence network has the following technical problems:

[0003] 1) In order to compensate for the path loss of Terahertz, the transceiver usually uses the power gain provided by the high directivity beam. However, the extremely narrow beam brings challenges to mobile user beam management, including frequent beam switching and serious beam misalignment effects, which result in extremely high switching overhead, limiting the effective data throughput of the Terahertz network.

[0004] 2) The need for Terahertz narrow beam alignment requires frequent control signaling transmission, which is very costly. In high-density and high-mobility networks, extremely narrow beam alignment requires high accuracy, which is extremely prone to beam misalignment, thereby reducing link stability. Solutions are needed to assist Terahertz beam alignment and ensure seamless switching of users in the network.

[0005] 3) Based on the current communication standards and frame structure, a dual-band switching scheme suitable for Terahertz and low frequency is needed to cooperate with the Integrated Sensing and Communication (ISAC) of the Terahertz frequency band, and to minimize the switching time of mobile users. SUMMARY

[0006] The technical problem to be solved by the present application is to provide a mobile user beam management method for Terahertz and low frequency coexistence networks, which uses dual-band cooperative communication and sensing integration technology to achieve stronger beam alignment and lower overhead beam switching.

[0007] The application is a kind of terahertz and low frequency cooperative communication sensing integrated beam management method, including the following steps:

[0008] S1. Set the performance requirements of communication and sensing services on the terahertz ISAC network;

[0009] S2. Extract the current network parameters, signal parameters and frame structure parameters;

[0010] S3. According to the performance requirements of the terahertz ISAC network, the current network parameters, signal parameters and frame structure parameters, the average beam misalignment probability and the average beam switching overhead are calculated as functions of user speed and synchronization signal block (SSB) period;

[0011] S4. Based on the average beam misalignment probability function and the average beam switching overhead function, the feasible SSB period that meets the performance requirements of the terahertz ISAC network is obtained;

[0012] S5. Mobile user random access and data transmission stage:

[0013] User position detection step: The sub-6GHz macro base station sends synchronization signal block (SSB) according to the feasible SSB period to continuously monitor and locate the base station position information and user position information in the network, and the base station position information and user position information are transmitted to the nearest terahertz base station through the backhaul link;

[0014] User random access step: The nearest terahertz base station sends a preset number of synchronization signal blocks (SSB) to the mobile user according to the feasible SSB period, the mobile user receives and measures the SSB, selects the SSB with the maximum power and reports the SSB information to the nearest terahertz base station, and the nearest terahertz base station configures the beam for the user according to the SSB information reported by the mobile user, and establishes a communication link;

[0015] Data transmission step: The nearest terahertz base station uses the reference signal to continuously estimate the user speed, predicts the user trajectory, and predicts the need for beam switching when entering step S6; through sensing obstacle position, predicting beam switching, improving terahertz beam alignment capability, through predicting user moving trajectory, predicting required beam switching, thereby reducing control signaling overhead;

[0016] S6. ISAC sensing assisted beam switching: the nearest THz base station obtains candidate beam information according to the received SSB, one SSB represents a corresponding candidate beam, and judges whether the candidate beam is blocked, if not, the nearest THz base station estimates the speed of the mobile user and the coverage distance of the current beam, triggers the THz inter-site beam switching, determines the switched THz beam to access the nearest THz base station; if yes, it is judged whether the second nearest THz base station is available, when the second nearest THz base station is available, the THz inter-frequency cell switching is triggered, and the switched THz beam accesses the second nearest THz base station; when the second nearest THz base station is not available, the low frequency band switching is triggered, and the low frequency beam accesses the Sub-6GHz macro base station.

[0017] The present application utilizes the communication sensing integrated technology ISAC (Integrated Sensing and Communication) to realize positioning and user tracking, and then assists THz beam alignment, realizes efficient seamless beam switching in THz cells, between THz cells and between THz and low frequency bands. The usual ISAC assistance only uses a single frequency band. For low frequency, there is a lack of accuracy, and for high frequency, there is a problem of high signal processing complexity and large signaling overhead. The present application innovatively proposes to use low frequency to detect the user's position, and the user's size is m level, and rough accuracy detection can be used, and sub-6GHz signal is used.

[0018] Under the premise that the user's position is determined by rough sensing, only THz is used for fine scanning and accurate speed estimation in a specific area, and THz signal is used for user speed estimation and switching type decision determination, which can significantly reduce the overhead, while ensuring the accuracy and effectiveness of beam switching.

[0019] Specifically, the specific steps of the THz inter-site beam switching are as follows: the nearest THz base station divides the coverage distance estimation value of the current beam by the time length of the feasible SSB period to obtain a speed threshold, judges whether the speed estimation value of the mobile user is less than or equal to the speed threshold, if yes, the nearest THz base station transmits a preset number of SSBs according to the SSB period, if not, the nearest THz base station immediately transmits a preset number of SSBs; the mobile user receives and measures the SSB, selects the SSB with the maximum power and reports the SSB information to the nearest THz base station; the nearest THz base station configures a beam for the user according to the SSB information reported by the mobile user, and completes the beam switching.

[0020] The specific steps of the terahertz same-frequency cell switching are that the nearest terahertz base station informs the next nearest terahertz base station to immediately transmit an SSB burst set through a backhaul link, the SSB burst set represents all beams of the next nearest terahertz base station; the mobile user receives and measures the SSB burst set, selects the SSB with the maximum power and reports the SSB information to the next nearest terahertz base station; the next nearest terahertz base station configures the beam for the user according to the SSB information reported by the mobile user, performs cell switching, completes the initial access of the next nearest terahertz base station and completes the beam switching.

[0021] The specific steps of the low-frequency band switching are that the nearest terahertz base station informs a Sub-6GHz macro base station to immediately transmit an SSB burst set through a backhaul link; the SSB burst set represents all beams of the Sub-6GHz macro base station, the mobile user receives and measures the SSB burst set, selects the SSB with the maximum power and reports the SSB information to the Sub-6GHz macro base station; the Sub-6GHz macro base station configures the beam for the user according to the SSB information reported by the mobile user, performs band switching, completes the initial access of the Sub-6GHz macro base station and completes the beam switching.

[0022] On this basis, for the frame structure design of ISAC, the high overhead caused by frequent transmission of signaling and the problem that the sensing information is not timely caused by insufficient signaling transmission cannot effectively switch. The application designs a terahertz and low-frequency cooperative ISAC scheme and a beam management signaling period, i.e., a synchronization signal block (SSB) period, finds the most suitable SSB period, which can meet the measurable speed requirement, the beam alignment capability requirement and the coverage requirement at the same time.

[0023] The application has the following beneficial effects:

[0024] (1) In order to improve the terahertz narrow beam alignment performance and reduce the alignment overhead, the application provides a beam switching solution based on the ISAC terahertz and low-frequency cooperation. The application can effectively reduce the beam misalignment probability and beam switching signaling overhead in the network, and is compatible with the existing 5G protocol.

[0025] (2) The application is an ISAC-based communication network, and an SSB period that can meet the beam misalignment threshold, user speed and data load efficiency requirement at the same time is designed. The improved ISAC frame structure is compatible with the current air interface standard frame structure.

[0026] (3) The beam switching scheme provided by the application is compatible with the current wireless communication network air interface, the SSB period design is highly compatible with the current 5G frame structure, only a small adjustment is made on the current parameter set, and has high practicability. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1Flow chart for the sensing resource allocation scheme of the present invention.

[0028] Figure 2 Flow chart for the feasible SSB period design of the present invention.

[0029] Figure 3 Flow chart for the ISAC based mobile user random access and data transmission of the present invention.

[0030] Figure 4 Flow chart for the terahertz and low frequency collaborative ISAC sensing assisted beam switching of the present invention.

[0031] Figure 5 Network beam misalignment probability variation curve under different beam numbers.

[0032] Figure 6 Network beam switching overhead variation curve under different beam numbers.

[0033] Figure 7 Feasible SSB period under different maximum user speeds. DETAILED DESCRIPTION

[0034] The present invention is applicable to a wireless mobile network coexisting with terahertz and Sub-6GHz frequency bands, which can utilize sensing function to provide assistance for beam alignment. The present invention provides a beam switching scheme based on ISAC collaborative terahertz and low frequency for this type of network. At the same time, the present invention provides a beam switching signaling period that meets the requirements of beam misalignment threshold, user speed and data load efficiency.

[0035] The present invention is implemented in a network composed of multiple randomly distributed terahertz base stations and Sub-6GHz base stations, where the terahertz base stations and Sub-6GHz base stations are independently distributed and connected through backhaul links. There are multiple users moving in random directions in the network, which access the nearest available base station under the criterion of maximizing received power. In addition to communication nodes, the present invention also considers the blocking problem of communication signals by obstacles, and considers all base stations and users in the network as potential blockers for this typical communication node.

[0036] The present invention will be described in detail below in conjunction with the accompanying drawings and simulation examples, which prove the practicability of the present invention.

[0037] The application is suitable for a wireless mobile network coexisting with a terahertz and a Sub-6GHz frequency band, which can utilize a sensing function to provide assistance for beam alignment, thereby improving the beam alignment probability and reducing the beam alignment overhead. The application provides a beam switching scheme based on ISAC terahertz and low-frequency cooperation for such a network, and provides a signaling transmission cycle design that simultaneously meets the beam misalignment threshold, user speed and data load efficiency requirements. Specifically, the application considers a network composed of multiple randomly distributed terahertz base stations and Sub-6GHz base stations, wherein the terahertz base stations and the Sub-6GHz base stations are independently distributed and linked through a backhaul. There are multiple users moving in random directions in the network, which access the nearest available base station in the criterion of maximizing the received power. In addition to the communication nodes, the application also considers the blocking problem of communication signals by obstacles, and considers all base stations and users in the network as potential blockers for the typical communication node. The time-frequency signal structure proposed by the application is based on the current 5G communication system orthogonal frequency division multiplexing (OFDM) frame structure and parameter set design, and has high practicability and can be integrated into the existing system. As shown in Figure 1 , the specific implementation of the beam switching scheme proposed by the application is as follows:

[0038] Step S1, set the performance requirements of communication and sensing services on the terahertz ISAC network, and obtain the following three performance parameters: 1) beam misalignment probability threshold 2) maximum user speed v Q ; 3) data load efficiency β Q .

[0039] Step S2 extracts network parameters, signal parameters and frame structure parameters. Including the density of nodes in the network, the densities of terahertz base stations, Sub-6GHz macro base stations and mobile users are respectively T , λ M , λ U ; 2) the number of beams, the number of beams used by the terahertz base station and the Sub-6GHz base station respectively ; 3) the beam width is respectively T , θ M ; 3) the radius of the base station r B . The signal parameters include 1) the terahertz frequency band: the center frequency , the total bandwidth , the RS bandwidth , the RS duration 2) the Sub-6GHz signal parameters: the center frequency , the total bandwidth The frame structure parameters include 1) the frame length T F; 2) SSB duration: sub-6GHz band Sub-6GHz band 3) SSB burst set size: sub-6GHz band Sub-6GHz band

[0040] Step S3, calculate the average beam misalignment probability, beam switching overhead. First, according to the maximum user speed v Q , the average beam misalignment probability is calculated as a function of the user speed v and the SSB period τ T , as follows

[0041]

[0042] where λ = λ T + λ M + λ U , The function Next, the average beam switching overhead T SW is calculated as a function of the user speed and the SSB period τ T , as follows

[0043]

[0044] where denotes the ceiling function,

[0045] Step S4 specifically includes the sub-steps as shown in Figure 2 , specifically as follows:

[0046] Step S410: the beam misalignment threshold is brought into the function of the average beam misalignment probability obtained in S3 about the SSB period , and the maximum user speed about the SSB period is solved as follows

[0047]

[0048] Step S420: using one-dimensional linear search to obtain the SSB period supporting the demand speed, denoted as set A

[0049] A = {τ T | v max (τ T ) ≥ v Q}

[0050] Step S430: the maximum user speed v QBring in the average beam switching overhead function, solve the data payload efficiency β Q And the function of SSB period β D (τ T ), as follows

[0051]

[0052] Step S440: using one-dimensional linear search to get the SSB period that satisfies the data payload efficiency, denoted as set B

[0053] B={τ T |β D (τ T )≥β Q}

[0054] Step S450: take the maximum value in the intersection of set A and B as the SSB period, and configure the frame structure. As follows

[0055]

[0056] Step S5 contains the sub-steps as shown in Figure 3 , specifically as follows:

[0057] Step S510: user position detection. Sub-6GHz macro base station MBS transmits SSB burst set with period τ T , which includes all macro base station beam directions. Based on the sensing information, the macro base station performs coarse positioning of the base station and user position in the network, and transmits it to the nearest TBS, denoted as TBS1, through the backhaul connection.

[0058] Step S520: user random access. TBS1 transmits SSB burst set to mobile users periodically, which includes all TBS base station beam directions. The user receives the SSB and measures the power, and reports the beam information corresponding to the SSB with the maximum power to TBS1. TBS1 configures the beam to serve the user and establishes a communication link.

[0059] Step S530: data transmission. TBS1 performs fine sensing using the reference signal in the data frame, continuously estimates the user speed, predicts the trajectory, and predicts the required beam switching type.

[0060] S6, ISAC sensing assisted same-site beam switching, same-frequency cell switching and low-frequency band switching.

[0061] 1) Firstly, based on the obtained perception information, TBS1 selects the switching type and corresponding command transmission according to different situations. If the candidate beam of TBS1 is not blocked, terahertz intra-site beam switching is triggered, that is, high frequency transmission is preferred in the case of high frequency availability (i.e. not blocked). Specifically, TBS1 estimates the speed of the mobile user MT and the coverage distance d b of the current beam. If , TBS1 immediately transmits 4 synchronization signal blocks (SSBs) representing the corresponding 4 candidate beams, facilitating beam switching measurement and candidate beam selection at the MT end.

[0062] 2) If the candidate beam of TBS1 is blocked and the next nearest base station TBS2 is available, terahertz intra-frequency cell switching is triggered. Specifically, TBS1 informs the next nearest base station TBS2 through the backhaul link to immediately transmit an SSB burst set. The SSB burst set represents all beams of TBS2, facilitating measurement and new cell access at the MT end.

[0063] 3) If the next nearest base station TBS2 is not available, low frequency band switching is triggered. TBS1 informs MBS through the backhaul link to immediately transmit an SSB burst set. The SSB burst set represents all beams of MBS, which is used for candidate beam measurement and frequency band switching at the user end.

[0064] As shown in Figure 4 , the specific implementation is as follows:

[0065] Step S610: MBS transmits base station location information and user location information to TBS1. TBS1 determines whether the candidate beam is blocked. If not, go to step S620 to trigger terahertz intra-site beam switching; if yes, go to step S640.

[0066] Step S620: TBS1 estimates the speed of the MT and the coverage distance d b of the current beam.

[0067] Step S630: TBS1 determines whether the user receives a preset SSB burst set at the current speed. Specifically, it can be divided into the following sub-steps:

[0068] Sub-step S631: If , that is, yes, TBS1 transmits 4 candidate SSBs according to the preset SSB period, representing the corresponding candidate beams, and goes to sub-step S633.

[0069] Sub-step S632: If , that is, no, TBS1 immediately transmits the candidate SSB, and goes to sub-step S633.

[0070] d bdenotes the current beam coverage distance, τ T denotes the current transmission period. The user needs to select and report the candidate beam before disconnection, that is, to receive the SSB transmitted by the current beam within the current beam coverage distance τ T period. If the speed is greater than d b / τ T , that is, there is a possibility that no SSB is received within the coverage range, the selection and reporting of the candidate beam cannot be completed, and when the user leaves the current beam coverage range, disconnection occurs, that is, beam misalignment occurs.

[0071] Substep S633: The user receives and measures the SSB, selects the SSB with the maximum power and reports the information thereof. TBS1 configures the beam for the user according to the information, and completes the beam switching.

[0072] Step S640: TBS1 judges whether the base station TBS2 is available. Specifically, the following substeps can be divided:

[0073] Substep S641: If the next base station TBS2 is available, a terahertz same-frequency cell switching is triggered. Specifically, TBS1 notifies the next base station TBS2 to immediately transmit an SSB burst set through a backhaul link. The SSB burst set represents all beams of TBS2. The user measures the SSB burst set and initiates random access with the new base station to perform cell switching and complete beam switching.

[0074] Substep S642: If the next base station TBS2 is not available, a low-frequency band switching is triggered. Specifically, TBS1 notifies MBS to immediately transmit an SSB burst set through a backhaul link. The SSB burst set represents all beams of MBS. The user measures the SSB burst set and initiates random access with the low-frequency base station to perform band switching and complete beam switching.

[0075] The present application will further illustrate the effectiveness of the proposed ISAC-based terahertz and low-frequency cooperative beam switching scheme and the trend of the optimal SSB period with the change of system parameters. By comparing the beam misalignment probability and beam switching overhead of the system without using the scheme of the present application, it is proved that the scheme provided by the present application can provide significant performance gain.

[0076] Figure 5 The network beam misalignment probability curve under different beam numbers is shown. In a typical urban scenario, the terahertz and low-frequency cooperative ISAC scheme can reduce the average beam misalignment probability by 34.1%, and in a typical high-speed scenario, the proposed scheme can reduce the beam misalignment probability by 42.9%.

[0077] Figure 6The network beam switching overhead curve changes under different beam numbers. In a typical urban scenario, the terahertz and low-frequency cooperative ISAC scheme can reduce the average beam switching overhead by 41.9%, and in a typical high-speed scenario, the proposed scheme can reduce the beam switching overhead by 46.1%. And when using large-scale narrow beams, the proposed scheme shows greater advantages.

[0078] Figure 7 The feasible SSB period under different maximum user speeds is The data load efficiency requirement is The gray bar represents. When the maximum user speed v Q = 250 km / h, a shorter SSB period is required, about 15-25 ms. When the user speed v Q = 120 km / h, a longer SSB period is required, about 45-65 ms.

[0079] In summary, the present application provides a beam switching scheme based on ISAC for terahertz and low-frequency cooperative wireless mobile networks coexisting with sub-6GHz frequency bands and an SSB period that meets the beam misalignment threshold, user speed and data load efficiency requirements. The proposed scheme significantly reduces the network's beam misalignment probability and beam switching overhead, and the designed SSB period is compatible with the current 5G standard parameter set, with high compatibility and high practicality.

Claims

1. A beam management method integrating terahertz and low-frequency cooperative communication sensing, characterized in that, Includes the following steps: S1. Define the performance requirements of the terahertz ISAC network for communication and sensing services; S2. Extract current network parameters, signal parameters, and frame structure parameters; S3. Based on the performance requirements of the terahertz ISAC network, current network parameters, signal parameters, and frame structure parameters, calculate the average beam misalignment probability and average beam switching overhead as functions of user speed and synchronization signal block SSB period, respectively. S4. Based on the average beam misalignment probability function and the average beam switching overhead function, a feasible SSB cycle that meets the performance requirements of the terahertz ISAC network is obtained. S5. Mobile user random access and data transmission phase: User location detection steps: The Sub-6GHz macro base station sends synchronization signal blocks according to the feasible SSB cycle. The SSB continuously monitors and locates the base station location information and user location information in the network. The base station location information and user location information are transmitted to the nearest terahertz base station through the backhaul link. User random access steps: The nearest terahertz base station sends a preset number of synchronization signal blocks (SSBs) to the mobile user according to the feasible SSB cycle. The mobile user receives and measures the SSBs, selects the SSB with the highest power and reports the SSB information to the nearest terahertz base station. The nearest terahertz base station configures a beam for the user and establishes a communication link based on the SSB information reported by the mobile user. Data transmission steps: The nearest terahertz base station continuously estimates the user speed and predicts the user trajectory using the reference signal. When it is determined that beam switching is required, it proceeds to step S6. S6. ISAC-based sensing-assisted beam handover: The nearest terahertz base station determines candidate beams based on the SSB measurement information reported by the user. Each SSB corresponds to one candidate beam. The station also determines whether the candidate beam is blocked. If not, the nearest terahertz base station estimates the speed of the mobile user and the coverage distance of the current beam, triggering a terahertz co-station beam handover. The terahertz beam to be handed over is connected to the nearest terahertz base station. If the beam is blocked, the station determines whether the next nearest terahertz base station is available. If the next nearest terahertz base station is available, a terahertz co-frequency cell handover is triggered, and the terahertz beam to be handed over is connected to the next nearest terahertz base station. If the next nearest terahertz base station is unavailable, a low-frequency band handover is triggered, and a low-frequency beam is selected to connect to the Sub-6GHz macro base station.

2. The method as described in claim 1, characterized in that, The specific steps of terahertz co-station beam switching are as follows: The nearest terahertz base station divides the estimated coverage distance of the current beam by the time length of the feasible SSB cycle to obtain the speed threshold. It then determines whether the speed estimate of the mobile user is less than or equal to the speed threshold. If so, the nearest terahertz base station transmits a preset number of SSBs according to the SSB cycle. If not, the nearest terahertz base station immediately transmits the preset number of SSBs. The mobile user receives and measures the SSBs, selects the SSB with the highest power, and reports the SSB information to the nearest terahertz base station. The most recent terahertz base station configures beams for users based on the SSB information reported by mobile users and completes beam switching.

3. The method as described in claim 1, characterized in that, The specific steps for terahertz co-frequency cell handover are as follows: The nearest terahertz base station notifies the next nearest terahertz base station via a backhaul link to immediately transmit an SSB burst set, which represents all beams of the next nearest terahertz base station. The mobile user receives and measures the SSB burst set, selects the SSB with the highest power, and reports the SSB information to the next nearest terahertz base station. The next nearest terahertz base station configures beams for the user based on the SSB information reported by the mobile user, performs cell handover, completes the initial access to the next nearest terahertz base station, and completes beam handover.

4. The method as described in claim 1, characterized in that, The specific steps for low-frequency band switching are as follows: The nearest terahertz base station notifies the Sub-6GHz macro base station to immediately transmit an SSB burst set via the backhaul link; the SSB burst set represents all beams of the Sub-6GHz macro base station; the mobile user receives and measures the SSB burst set, selects the SSB with the highest power and reports the SSB information to the Sub-6GHz macro base station; the Sub-6GHz macro base station configures the beam for the user according to the SSB information reported by the mobile user, performs band switching to complete the initial access of the Sub-6GHz macro base station, and completes the beam switching.

5. The method as described in claim 1, characterized in that, The performance requirements of terahertz ISAC networks include beam misalignment probability thresholds. Maximum user rate v Q and data load efficiency β Q .

6. The method as described in claim 5, characterized in that, Current network parameters include: the density λ of terahertz base stations. T Density of Sub-6GHz macro base stations λ M and the density of mobile users λ U The number of beams used by terahertz base stations and beamwidth θ T Number of beams used by Sub-6GHz base stations and beamwidth θ M Base station radius r B ; Signal parameters include the center frequency of the terahertz signal. Total bandwidth Reference signal bandwidth and duration The center frequency of the Sub-6GHz signal and total bandwidth Frame structure parameters include frame length T F Duration of the synchronization signal block SSB in the terahertz band Duration of the Synchronization Signal Block (SSB) in the Sub-6GHz band SSB burst set size in the terahertz band SSB burst set size in the Sub-6GHz band 7. The method as described in claim 6, characterized in that, Mean beam misalignment probability Regarding user speed v and SSB period τ T The function is: Where c is the speed of light, an intermediate quantity Total density λ=λ T +λ M +λ U intermediate quantity intermediate quantity function x is the independent variable; Average beam switching overhead T SW Regarding user speed v and SSB period τ T The function is: in, The function represents the floor function. r is the independent variable.

8. The method as described in claim 7, characterized in that, The specific method for obtaining a feasible SSB period that meets the performance requirements of terahertz ISAC networks based on the average beam misalignment probability function and the average beam switching overhead function is as follows: Beam misalignment probability threshold Substitute the average beam misalignment probability The function obtains the maximum user speed v. max Regarding the SSB period τ T Functions: Find the maximum user speed v using a one-dimensional linear search. max Demand SSB cycle τ T Let A be the set of sets: A={τ T |v max (t T )≥v Q }; Set the user speed threshold v Q Substituting the average beam switching overhead function T SW The data load efficiency β is obtained. D Regarding the SSB period τ T Functions: The SSB period τ that satisfies the data load efficiency requirements is obtained using a one-dimensional linear search. T Let B be the set: B={τ T |b D (t T )≥β Q }; The maximum value in the intersection of sets A and B is taken as the final determined SSB period τ. T :

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