A millimeter wave communication base station synchronization signal directional transmission method

Abstract

The application discloses a millimeter wave communication base station synchronization signal directional transmission method, which comprises the following steps: a preparation codebook at the millimeter wave communication base station comprises different levels of wide / narrow beams; the millimeter wave communication base station can record and store the historical channel information of the millimeter wave communication user; the millimeter wave communication base station can estimate / calculate and store the historical channel samples established with each user; the millimeter wave communication base station can determine the alternative beam subset of the synchronization signal directional transmission according to the stored historical information; and the millimeter wave communication base station can adjust the time of beam allocation in the alternative beam subset when the millimeter wave base station synchronization signal is directionally transmitted according to the spatial distribution of the user in the current recent period and / or the similar period in the history. The millimeter wave communication base station synchronization signal directional transmission method disclosed by the application does not need to obtain the exact channel information, can be adapted to various scenes, and can greatly shorten the average time required for initial access of the user.

Description

Technical Field

[0001] This invention relates to the field of millimeter-wave communication technology, specifically to a method for directional transmission of synchronization signals in a millimeter-wave communication base station. Background Technology

[0002] Millimeter-wave communication plays a crucial role in fifth-generation mobile communication technology (5G) and future communication networks. In millimeter-wave communication systems, base stations and / or user equipment typically rely on beamforming techniques implemented with antenna arrays to compensate for the high path loss of millimeter-wave signals and ensure the stability of the communication link. When a user establishes an initial millimeter-wave communication link with a base station, the user needs to quickly discover nearby base stations and synchronize with them. This process is also known as initial access. A common method for initial access is for the base station to periodically broadcast a reference signal. The user detects the presence of the received signal and then evaluates its quality to connect to the network. Therefore, the beamforming strategy used by the millimeter-wave communication base station to broadcast the reference signal directly affects the time required for initial access.

[0003] Currently, common millimeter-wave base station synchronization signal broadcasting schemes include omnidirectional broadcasting and narrow-beam sequential scanning. The former uses a single antenna to broadcast the synchronization signal indiscriminately in all coverage directions, resulting in low directional gain and inability to guarantee coverage. The latter, on the other hand, sequentially sends synchronization signals using beams pointing in different directions, requiring a longer time to scan the entire angular space, impacting the initial access speed for users. Some newer schemes consider optimizing the base station's beam scanning strategy based on user location information, enabling the targeted transmission of synchronization signals to users based on accurate location information, thus improving access speed and success rate. However, this type of scheme also suffers from the problem of difficulty in obtaining location information from users to the base station.

[0004] Another type of base station broadcast reference signal scheme optimizes the beam of the broadcast reference signal using the channel statistical characteristics of historical users. A representative technique is the paper "Fast Millimeter-Wave Base Station Discovery via Data-driven Beam Training Optimization," published at the 2022 International Symposium on Wireless Communication Systems. This paper proposes to select the beam used for broadcasting the synchronization reference signal based on the channel characteristics of historical users to better match the user distribution around the base station. However, this method is only effective in static scenarios where the user range does not change, and cannot adapt to dynamic scenarios where the user range frequently changes. Furthermore, the method proposed in this paper requires accurate channel information of historical users, which is very costly to obtain in practical systems.

[0005] In summary, it can be seen that the existing beam search strategies for directional transmission of synchronization signals in millimeter-wave communication base stations can only achieve good performance under relatively ideal conditions, and cannot adapt to the dynamic and ever-changing millimeter-wave communication scenarios in real-world situations. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings of existing technologies by proposing a method for directional transmission of synchronization signals for millimeter-wave communication base stations. This method addresses the fact that the location of a user changes over time by enabling the use of a beam to better match the user's location, thereby significantly reducing the time required for initial user access and lowering the average latency of initial user access in various scenarios.

[0007] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows:

[0008] A method for directional transmission of synchronization signals in millimeter-wave communication base stations.

[0009] The present invention is characterized in that the millimeter-wave communication base station uses a multi-level beamcodebook with different widths to search for and communicate with all users within the receiving range.

[0010] Preferably, the codebook at the millimeter-wave communication base station contains different levels of wide / narrow beams. The wide / narrow beams that are more suitable are used according to the distance between the user and the base station. This allows the user to detect the signal and establish synchronization with the base station more quickly when the millimeter-wave communication base station transmits the synchronization signal in a directional manner, thereby reducing the average latency of the user's initial access.

[0011] Preferably, the number of antennas at the base station is N. T The codebook contains K levels, such as Figure 1 As shown, the k-th level of the codebook is represented as B.k Each level of the codebook has a different beamwidth; the k-th level codebook contains 2... k-1 Multiple beams are used to cover the entire angular space. In B k The beam index in the codebook is f k , and f k =1,...,2 k-1 Therefore, beams in different codebooks can be represented as Specifically, the omnidirectional beam is denoted as w1. During the broadcast of the synchronization signal, the base station can use any beam from any level codebook; during data communication after synchronization is established, beam alignment is completed and the optimal beam of level K is used for communication. The optimal beam index of level K is denoted as f. K * .

[0012] The present invention is characterized in that the millimeter-wave communication base station records and stores the historical channel information of each millimeter-wave communication user, including:

[0013] Record the beam index f used by the base station when the user communicates with the base station. K * Equivalent signal-to-noise ratio after beamforming And the number of antennas N at the user end R ;

[0014] The beam index used by the storage base station is f K * The total number of users connected to the beam during the time period

[0015] The invention is characterized in that the millimeter-wave communication base station estimates / calculates the historical channel samples H established with each user by using the recorded historical channel information of millimeter-wave communication users. n And store all historical channel samples into set D.

[0016] As a preferred option, under the single-path approximation, the formula for reconstructing the historical sample channel is as follows:

[0017]

[0018] in, φ n The index is f K * The center angle of the beam coverage space in degrees u(φ n ) and v(ψ n ) are the array direction vectors of the base station and the user terminal, respectively. Historical channel sample collection

[0019] Preferably, beam filtering is performed on the codebook at each level, starting with the first level (k=1) codebook, i.e., omnidirectional beaming. The effective SNR of all historical channel samples in D can be calculated as:

[0020]

[0021] Among them, P T Where σ is the base station transmit power, and σ is the noise variance. Set the SNR threshold to SNR. th When ξ(H) n > SNR th If the probability of a missed detection is sufficiently low, then it is assumed that the historical user can establish synchronization with the base station through that beam. This sample set is represented as D1 = {H}. n |ξ(H n > SNR th H n ∈D}. Obviously, D1 contains users who can be quickly detected even if the base station broadcasts a signal omnidirectionally. If the sample set D1 is not empty, then the beam is added to the candidate beam subset, and beam filtering is performed on the codebook of the next level. At this time, k = k + 1, and the remaining sample set D′2 = D - D1.

[0022] For the next k-th level codebook (1 < k ≤ K), it will be processed through the remaining sample set D′. k Beam selection. The remaining sample set is represented as... D k These are samples that have been assigned to clusters identified at level k. Specifically, through D′ k The alternative beaming methods in the selection hierarchy are as follows:

[0023] When it's D''s turn to be detected k At that time, the array of the maximum SNR and corresponding beam index of all samples in the set at that level is represented as: Set the SNR threshold for this level to SNR. th .in, That is, to generate the maximum SNRξ k (H n Beam guidance for D′. k In the middle, satisfy ξ k (H n > SNR th Clustering is performed on the array, and the clustering result is the beam index and the corresponding number of samples. The set of beam indices identified by the k-level codebook is represented as S. k The corresponding set of sample sizes is denoted as M. kIf k≠K at this point, then beam filtering continues for the next level codebook (k=k+1).

[0024] After beam filtering has been performed on all levels of the codebook, i.e., k = K, the resulting set of beamguides is represented as follows: This constitutes a subset of candidate beams, and the set containing the number of samples corresponding to all beamguides is represented as follows: Specifically, not all codebook levels need to be considered during beamforming. When the beamforming process skips k codebook levels,

[0025] The present invention is characterized in that, at the millimeter-wave communication base station, the beam allocation time of the candidate beam subset is adjusted according to the spatial distribution of users in the current recent time period / or similar historical time periods.

[0026] Preferably, assuming the current time slot is t, the beam allocation time within the period [t, t+J1-1] is updated based on the user spatial distribution of the more recent period [t-J1, t-1], where J1 is the duration of that period. Preferably, the historical user beam allocation S can be calculated using the Generalized Likelihood Ratio Test (GLRT). n (S n The approximate probability p of the detection of ∈S) n The formula is shown below:

[0027]

[0028] Where, N s This represents the number of samples in the RS sequence. It is the cumulative distribution function of the F-distribution F(n1,n2,λ1), and γ is the GLRT test threshold, which can be set to satisfy the false alarm target P. FA :

[0029] Consequently, all users are beamed S n The mean probability of successful detection is expressed as:

[0030]

[0031] Where, N D This represents the total number of historical channel samples. Therefore, it corresponds to the set of beam indices. The set of probability means can be represented as beam S n The number of users successfully detected in the most recent time period is denoted as N. nThen beam S n The detected user density is The time allocation to each beam is based on the proportion ρ of the number of users that each beam can detect. n The probability P of a user being detected by each beam n Confirmed, as shown in the following formula:

[0032]

[0033] Therefore, the beam S allocated to the next time period n The time can be calculated as α n J1 time slots. Since the statistical average results over a long period are taken into account, no special provisions are made for the beam scanning order. When the user distribution of the time period [t',t'+J1-1] is similar to that of a previous time period [t,t+J1-1], the time allocation ratio used in the time period [t,t+J1-1] can be used directly.

[0034] The present invention is characterized in that the required configuration at the millimeter-wave base station includes:

[0035] The information acquisition module is used to collect historical channel information;

[0036] The data processing module is used to calculate historical channel samples, determine whether each beam at each level is selected into the candidate beam subset, and determine the time allocation of the candidate beam subset in the next time period.

[0037] The storage module is used to store historical channel information and historical channel samples;

[0038] The control module is used to control the operation of the information acquisition module, data processing module, and storage module.

[0039] The present invention is characterized in that a computer device required for a millimeter-wave base station includes a processor, a memory, and a program or instructions stored in the memory and executable on the processor, wherein the program or instructions, when executed by the processor, implement any step of the method for directional transmission of synchronization signals of a millimeter-wave communication base station.

[0040] The present invention is further characterized by a computer-readable storage medium storing a computer program thereon, wherein the program or instructions, when executed by a processor, implement any step of the method for directional transmission of synchronization signals of a millimeter-wave communication base station.

[0041] This invention has the following characteristics and beneficial effects:

[0042] This invention obtains a subset of candidate beams that fit the current scenario by recording and storing available historical channel information of communication users at millimeter-wave communication base stations and using clustering methods. It also significantly reduces the average latency of initial user access by dynamically adjusting the scanning time of each training beam when transmitting the synchronization signal of the millimeter-wave base station according to the spatial distribution of users in the time period. Attached Figure Description

[0043] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0044] Figure 1 This is a schematic diagram of the multi-level codebook of the present invention;

[0045] Figure 2 Flowchart for determining candidate beam subsets for this invention;

[0046] Figure 3 This is a schematic diagram of a simulation scenario according to an embodiment of the present invention.

[0047] Figure 4 This is a schematic diagram of the candidate beam subset obtained in an embodiment of the present invention when there are sufficient historical channel samples.

[0048] Figure 5 This is a structural diagram of the directional transmission of synchronization signals according to an embodiment of the present invention.

[0049] Figure 6 , Figure 7 This is a comparison chart of the average initial access latency of users under the condition of sufficient historical user information, according to an embodiment of the present invention.

[0050] Figure 8 This is a schematic diagram of the configuration structure at a millimeter-wave base station provided in an embodiment of the present invention. Detailed Implementation

[0051] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0052] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0053] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0054] Example

[0055] Taking one scenario as an example, the commercial ray tracing software Wireless Insite is used to model a complex urban outdoor millimeter-wave communication scenario to generate the test data required for this implementation.

[0056] In this embodiment of the invention, the millimeter-wave communication scenario is a 500*500 meter square area in Roslin, Virginia, USA, such as... Figure 3 As shown. A millimeter-wave base station has been deployed in this area. Figure 3 (At the green dot), the millimeter-wave communication base station is equipped with 16 (N) T =16) A uniform linear array of antennas spaced at half-wavelength intervals is used to search for and communicate with all users within the receiving range; the codebook at the millimeter-wave base station contains four levels, k=1,2,4,5; the transmit power P T =30dBm. The user's possible locations are as follows: Figure 3 As shown in the red dot matrix. The millimeter-wave user terminal is configured with 1(N) R =1) With one antenna, the user end will detect the presence of the synchronization signal for directional transmission and estimate the average delay time for accessing the network.

[0057] In embodiments of the present invention, in order to obtain relevant information about user locations over the largest possible coverage area, the base station uses a level 5 narrow-beam sequential broadcast reference signal for a period of time to establish synchronization with users in the scene whose signals can be detected. The millimeter-wave base station records and stores historical channel information of millimeter-wave communication users, including:

[0058] (1) Record the beam index f5 used by the base station when the user communicates with the base station for data. * Equivalent signal-to-noise ratio after beamforming And the number of antennas N at the user end R ;

[0059] (2) The beam index used by the storage base station is f5. * The total number of users connected to the beam during the time period

[0060]

[0061] Furthermore, in an embodiment of the present invention, under the single-path approximation, the formula for reconstructing the historical sample channel is as follows:

[0062]

[0063] in, φ n Beam index f5 * Central degree u(φ n ) can be represented as Here Historical channel sample collection

[0064] With sufficient historical channel samples stored, this embodiment stores a total of approximately 4,000 historical channel samples.

[0065] In embodiments of the present invention, the millimeter-wave communication base station determines a subset of candidate beams for directional transmission of synchronization signals through DBSCAN clustering based on stored historical user channel information. For example... Figure 4 As shown, embodiments of the present invention, by storing a sufficient number of historical channel samples, co-clustering yields 16 candidate beams of different widths. The subset of candidate beams is represented as...

[0066] Specifically, beam filtering starts from the first-level (k=1) codebook, i.e., the omnidirectional beam w1=[1,0,…,0], and sets the SNR threshold SNR. th = -3.95dB. Calculate the effective SNR of all historical channel samples in D: like Figure 3As shown in the scenario, there are many users in close proximity around the base station. When the signal-to-noise ratio of the channel is higher than a certain threshold, it is assumed that the millimeter-wave communication base station can quickly establish a connection with these users by using an omnidirectional beam for directional transmission of the synchronization signal. Therefore, the omnidirectional beam is selected as the alternative beam. This sample set is represented as D1 = {H} n |ξ(H n > SNR th H n ∈D}.

[0067] For a codebook with k=2 levels, set the SNR threshold SNR. th = -3.95dB, for samples in the set (D2′=D-D1) that satisfy ξ2(H n > SNR th Array of maximum SNR and corresponding beam indices Perform DBSCAN clustering screening, where, That is, to generate the maximum SNRξ2(H) n The beam guidance of the clustering results in a beam in the codebook at that level, such as... Figure 4 The thick solid line in the middle indicates k=2, f=1.

[0068] For a codebook with k=4 levels, set the SNR threshold SNR. th = -6.85dB, similarly for samples in the union set In the middle, satisfy ξ4(H) n > SNR th Array of maximum SNR and corresponding beam indices DBSCAN clustering was used to filter and obtain the three beams in the codebook at this level, such as... Figure 4 The thin solid line in the middle indicates k=4, f=1 / 2 / 8.

[0069] For a codebook with k=5 levels, set the SNR threshold SNR. th = -7.62dB, similarly for samples in the union set In the middle, satisfy ξ5(H) n > SNR th Array of maximum SNR and corresponding beam indices DBSCAN clustering and filtering yielded eleven beams in this level of codebook, such as... Figure 4 As shown by the dashed line.

[0070] In an embodiment of the present invention, the millimeter-wave base station adjusts the beam allocation time of the candidate beam subset when transmitting the millimeter-wave base station synchronization signal according to the spatial distribution of users in the most recent time period.

[0071] Specifically, in this embodiment, the generalized likelihood ratio test (GLRT) is used to calculate the user's beamwidth S. n Approximate probability of detection p n The formula is shown below:

[0072]

[0073] Where, N s This represents the number of samples in the RS sequence. It is the cumulative distribution function of the F-distribution F(n1,n2,λ1), and γ is the GLRT test threshold, which can be set to satisfy the false alarm target P. FA :

[0074] Figure 5 The frame structure diagram of the embodiment is shown below. J1 = 3000, user range passed The time slot changed once. All users were affected by beam S. n The mean probability of successful detection is expressed as:

[0075]

[0076] Where, N D This represents the total number of historical channel samples. Therefore, it corresponds to the set of beam indices. The set of probability means can be represented as Because a narrow-beam sequential scanning method is used in the user location information collection phase, it is impossible to obtain user density information that the training beams in the candidate beam subset can successfully detect. Figure 5 As shown, firstly, within the time period [T0, T0+J1-1] (the first time period in the yellow section), time allocation is performed on the beams in the candidate beam subset solely based on the probability mean P, with the time allocated to each beam being [percentage missing]. The time allocated to each beam can be represented as α. n J1 time slots. This allows for the collection of sufficient user density information during this period to facilitate subsequent beam time allocation. Beam S... n The number of users successfully detected during this period is denoted as N. n Then beam S n The detected user density is

[0077] For the following time periods [T0+(β-1)J1,T0+βJ1-1],β=2,...,30 (the remaining units in the yellow section and each time period in the green section), the beam time allocation will be updated based on the user density information collected in the preceding time period, i.e., [T0+(β-1)J1,T0+βJ1-1],β=1,...,29. Specifically, the time allocation to each beam is as follows:

[0078]

[0079] Similarly, assigned to beam S n The time can be calculated as α n J1 time slots. Since statistical averages over a long period of time are taken into account, no special rules are specified for the beam scanning order.

[0080] User access latency is also calculated using GLRT. When a millimeter-wave communication base station transmits synchronization signals directionally, the maximum delay time for users who fail to detect the base station is set to 1000 time slots (T). max =1000). The user's initial access delay is equal to the number of time slots it takes for the user to successfully detect the reference signal. For users who successfully detect the base station in the first available time slot, the initial access delay is set to 1.

[0081] The remaining parameters of this invention embodiment are shown in the following table:

[0082]

[0083]

[0084] Figure 6 , 7 The present invention provides a comparison of the method for millimeter-wave communication base stations proposed in this embodiment with the method proposed in the conference paper FastMillimeter-Wave Base Station Discovery via Data-driven Beam Training Optimization, and the use of a narrow beam sequential scanning method in terms of initial user access delay and the proportion of users accessing each time slot.

[0085] from Figure 6 and 7It can be seen that the user equipment initial access method proposed in this invention can identify changes in the user range in a short time and adjust the beam time allocation accordingly, thereby reducing the average user access time. Compared with the method used in this invention, the traditional method using narrow beam sequential scanning has an average user access time that is 270.2% longer, while the method proposed in the conference paper "Fast Millimeter-Wave Base Station Discovery via Data-driven Beam Training Optimization" is 28.7% longer. Furthermore, the method provided in this invention can successfully establish synchronization with 94.6% of users in the fifth time slot, while the algorithm proposed in the conference paper can only establish synchronization with 94.1% of users in the ninth time slot, and the narrow beam sequential scanning method can only establish synchronization with 93.9% of users in the thirteenth time slot. Therefore, it is clear that the millimeter-wave communication base station synchronization signal directional transmission method provided in this invention can successfully establish connections with most users in a short time.

[0086] at last, Figure 8 The configuration device structure at the millimeter-wave base station in this embodiment includes: an information acquisition module 801, a data processing module 802, a storage module 803, and a configuration module 804. The information acquisition module 801 is used to acquire historical channel information; the data processing module 802 is used to calculate historical channel samples, determine whether each beam at each level is selected into the candidate beam subset, and determine the time allocation of the candidate beam subset in the next time period; the storage module 803 is used to store historical channel information and historical channel samples; and the control module 804 is used to control the operation of the information acquisition module 801, the data processing module 802, and the storage module 803.

[0087] To achieve the above objectives, this embodiment proposes a computer device, including a processor, a memory, and a program or instructions stored in the memory and executable on the processor. When the program or instructions are executed by the processor, they implement any step of the millimeter-wave communication base station synchronization signal directional transmission method as described above.

[0088] To achieve the above objectives, this embodiment proposes a computer-readable storage medium storing a computer program that, when executed by a processor, implements any step of the millimeter-wave communication base station synchronization signal directional transmission method as described above.

[0089] In summary, the millimeter-wave communication base station synchronization signal directional transmission method proposed in this invention stores available historical user communication information at the millimeter-wave communication base station. Based on this stored information, it determines beams of different widths as candidate beam subsets for directional transmission of synchronization signals, thus better aligning with the user distribution in the real-time scenario. Furthermore, it adjusts the beam allocation time within the candidate beam subsets based on the user spatial distribution in the recent time period, significantly reducing the average initial access delay for users. Compared to beam scanning methods using only narrow beam search codebooks or the methods mentioned in the conference paper "Fast Millimeter-Wave Base Station Discovery via Data-driven BeamTraining Optimization," the method proposed in this invention is applicable to a wider range of communication scenarios. It can match the distribution of buildings and users within the scenario to select candidate beam subsets and allocate scanning times for each beam for directional transmission of synchronization signals. Moreover, it does not require precise channel information, resulting in a significant reduction in the average initial access time for users.

[0090] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions, and variations can be made to these embodiments, including components, without departing from the principles and spirit of the present invention, and these variations still fall within the protection scope of the present invention.

Claims

1. A method for directional transmission of synchronization signals in a millimeter-wave communication base station, characterized in that, Includes the following steps: S1. Construct a codebook for a millimeter-wave communication base station, wherein the codebook includes beams at different levels; In step S1, the codebook of the millimeter-wave communication base station contains Level, the first level of the codebook Level is represented as , No. The codebook contains One beam to cover the entire angular space, The beam index in the codebook is ,and The beams in different codebooks can be represented as Omnidirectional beam is represented as , No. The optimal beam index of the level is represented as ; S2. Record and store historical channel information of millimeter-wave communication users through millimeter-wave communication base stations; The historical channel information includes: No. Optimal beam index of level Equivalent signal-to-noise ratio after beamforming and the number of antennas at the user end ; The base station uses the first The optimal beam index for the class is The total number of users connected to the beam during the time period ; S3, millimeter-wave communication base stations reconstruct historical channel samples by estimating and storing the recorded historical channel information, thus obtaining a collection of historical channel samples. ; In step S3, the method for estimating and reconstructing historical channel samples is as follows: The formula for reconstructing historical sample channels is as follows: ； in, , Is the index as The center angle of the beam coverage angle space, and These are the array direction vectors for the base station and the user terminal, respectively. Then, historical channel samples are stored to obtain a collection of historical channel samples. ; S4. The millimeter-wave communication base station uses the SNR calculation method to perform beam filtering on the codebook at each level based on the stored historical channel samples to obtain a subset of candidate beams for directional transmission of synchronization signals. S5. The millimeter-wave communication base station will adjust the beam allocation time of the alternative beam subset when transmitting the synchronization signal of the millimeter-wave communication base station in a directional manner according to the spatial distribution of users.

2. The method for directional transmission of synchronization signals in a millimeter-wave communication base station according to claim 1, characterized in that, The filtering method in step S4 is as follows: S4-1, Starting from the first-level codebook, that is... It is an omnidirectional beam, for The remaining sample set is obtained by calculating the effective SNR of all historical channel samples. ; S4-2, For the next... The codebook includes, It will be through the remaining sample set. After filtering the beams, the remaining sample set is represented as , It has been allocated to Samples for hierarchical clustering; S4-3, until beam filtering has been performed on codebooks at all levels, i.e. The resulting set of beam indexes is represented as This constitutes a subset of candidate beams, and the set containing the number of samples corresponding to all beam indices is represented as... .

3. The method for directional transmission of synchronization signals in a millimeter-wave communication base station according to claim 2, characterized in that, The screening method in step S4-1 is as follows: The effective SNR of all historical channel samples can be calculated as: ； in, It is the base station's transmission power. It is the noise variance, and the SNR threshold is set to... ,when If the probability of a missed detection is low enough, it is assumed that the historical user was able to establish synchronization with the base station through that beam.

4. The method for directional transmission of synchronization signals in a millimeter-wave communication base station according to claim 3, characterized in that, The screening method in step S4-2 is as follows: When it's time for testing At that time, the array of the maximum SNR and corresponding beam index of all samples in the set at that level is represented as: And set the SNR threshold for this level to ;in, That is, to generate the maximum SNR Beam index; for China satisfies Clustering is performed on the array, and the clustering result is the beam index and the corresponding number of samples. The beam index set identified by the codebook is represented as follows: The corresponding set of sample sizes is represented as If at this time Then, beam filtering continues for the next level of codebook.

5. The method for directional transmission of synchronization signals in a millimeter-wave communication base station according to claim 2, characterized in that, The specific method for step S5 is as follows: When the user's spatial distribution is within the most recent time period, assuming the current time slot is... ,but The beam allocation time during this period is based on the most recent period. The user space distribution is updated, among which This refers to the duration of the time period; Historical user beaming is calculated using GLRT. Approximate probability of detection The formula is shown below: ； in, The number of samples in the RS sequence. , It is an F-distribution The cumulative distribution function, It is the GLRT test threshold; Consequently, all users are beamed The mean probability of successful detection is expressed as: ； in, This represents the total number of historical channel samples; thus, it corresponds to the set of beam indices. The set of probability means can be represented as ; to beam The number of users successfully detected in the most recent time period is represented as: Then the beam The detected user density is The time allocation to each beam is based on the proportion of users that each beam can detect. The probability that a user will be detected by each beam Confirmed, as shown in the following formula: ； Therefore, the beam allocated to the next time period The time can be calculated as Each time slot.

6. The method for directional transmission of synchronization signals in a millimeter-wave communication base station according to claim 5, characterized in that, When the spatial distribution of users corresponds to similar historical time periods, i.e., when a time period is encountered... With a certain period of time When user distributions are similar, time periods can be used directly. The proportion of time allocated.

7. A computer device required for a millimeter-wave base station, characterized in that, It includes a processor, a memory, and a program or instructions stored in the memory and executable on the processor, wherein the program or instructions, when executed by the processor, implement the steps of the millimeter-wave communication base station synchronization signal directional transmission method as described in any one of claims 1-6.

8. A computer-readable storage medium, characterized in that, The readable storage medium stores a computer program that, when executed by a processor, implements the steps of the millimeter-wave communication base station synchronization signal directional transmission method as described in any one of claims 1-6.

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