Initial access beam management method for 5g-integrated low earth orbit satellite communication system

Abstract

The application belongs to the technical field of satellite communication, and discloses an initial access beam management method of a low-orbit satellite communication system combined with 5G, which comprises the following steps: step 1, a to-be-served area of a ground 5G terminal is divided into a plurality of wave positions, and a queue model module is used to divide the wave positions and construct a queue model; step 2, in each access cycle, a beam allocation decision module is used to establish a beam allocation decision model, the beam allocation decision model is transformed and solved, and the number of signaling beams and the pointing strategy of the signaling beams are determined; and step 3, an access flow control module is used to complete an access flow: in each access cycle, a satellite side generates a downlink signaling beam, a ground 5G terminal listens to the downlink signaling, establishes a communication link and starts transmission after receiving the downlink signaling, and sends a completion notification after service completion. The application takes into account the satellite access coverage capability and the service efficiency, and improves the performance of the terminal service waiting time and the overall completed service quantity.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of satellite communication, and particularly relates to an initial access beam management method of a low-orbit satellite communication system integrated with 5G. BACKGROUND

[0002] 5G is the most outstanding technology in ground mobile wireless communication, and has been widely deployed in densely populated areas. However, in remote mountainous areas and border areas with low population density, the number of network accesses is extremely limited, and it is very difficult to provide 5G network coverage, which also increases the difficulty of device maintenance and other work, especially in the ocean, desert or other complex terrain areas. In contrast, the satellite communication system can solve the mobile communication coverage problem in the above scenarios due to its wide coverage and immunity to natural disasters on earth. Among various satellite communication systems, the low-orbit satellite communication system becomes an important supplement to the ground mobile communication system due to its relatively small round-trip delay, low path loss and relatively low transmission cost, and the advantage of seamless coverage of the earth through constellation.

[0003] A key problem in the low-orbit satellite communication system integrated with 5G is how to establish a stable communication link between the LEO satellite and the ground terminal. In ground 5G, the communication link is established through the initial access process, and the beam management method plays a crucial role. The ground 5G system uses a double-end hierarchical scanning method combined with beam measurement and reporting to perform beam alignment in the initial access stage to establish the link. However, the free space path loss of the LEO satellite is large, and if the wide beam is directly used for signaling transmission according to 5G NR, it is difficult to meet the signal-to-noise ratio requirement. Although the terminal can use a narrower beam for scanning to improve the received signal gain, this method will cause the beam measurement and reporting process to be cumbersome, significantly increasing the access delay, and since the low-orbit satellite moves at a high speed, the relative position of the terminal and the satellite changes rapidly, and the beam measurement result has the risk of expiration. However, if the low-orbit satellite side uses a narrow beam with higher signal gain for signaling transmission, it can solve the problem of high access delay caused by insufficient received signal power, but at the same time, it significantly reduces the coverage range of the signaling beam, causing the access coverage capability of the low-orbit satellite to be insufficient. At this time, due to the polling mechanism of the signaling beam, the narrow beam needs to be scanned more times to complete the polling, and there is still a problem of high access delay. To this end, more beams can be allocated for signaling transmission.

[0004] However, due to the wide coverage of the LEO satellite and the limited payload capacity, the terminal access process and the terminal data transmission process need to be considered at the same time under the limited number of beams. SUMMARY

[0005] To solve the above problems, the application provides an initial access beam management method of a low-orbit satellite communication system integrated with 5G, which proposes a low-orbit satellite and ground terminal fast beam alignment process for initial access and a service process based on a notification mechanism by combining a 5G initial access beam alignment process and satellite ephemeris information assistance; the access and service mechanism is established into a queue model, and the optimization objective is to maximize the number of access terminals per access cycle on the condition of ensuring system queue stability, and the Lyapunov problem transformation and golden section method are used for solving to form an online algorithm, and the optimal signaling beam number allocation and pointing strategy are dynamically determined; both the end-to-end fast access of the low-orbit satellite and the ground terminal are realized, and the system has good performance in the average waiting time of terminal service and the total completed service amount within a limited time.

[0006] To achieve the above purpose, the application is implemented by the following technical solutions:

[0007] The application is an initial access beam management method of a low-orbit satellite communication system integrated with 5G, which is realized by a beam management system in a low-orbit satellite communication system composed of a ground 5G terminal and a low-orbit satellite equipped with a controller, the beam management system includes a queue model modeling module, an access process control module and a beam allocation decision module, the queue model modeling module divides the ground area into wave positions and constructs a queue model, the queue model modeling module includes an access waiting queue and a service waiting queue, the controller of the low-orbit satellite makes beam allocation decisions according to the beam allocation decision module, and the low-orbit satellite equipped with the controller accesses according to the process designed by the access process control module, specifically, the beam management method specifically includes the following steps:

[0008] Step 1, the service area of the ground 5G terminal is divided into several wave positions, and the queue model modeling module divides the several wave positions and constructs a queue model;

[0009] Step 2, in each access cycle, the beam allocation decision module obtains the states of the access waiting queue and the service waiting queue, establishes a beam allocation decision model based on the states of the access waiting queue and the service waiting queue, transforms and solves the beam allocation decision model, and determines the signaling beam number allocation and the signaling beam pointing strategy;

[0010] Step 3, in each access cycle, the satellite side generates a downlink signaling beam according to the number of signaling beams determined in step 2 and the signaling beam pointing strategy, and receives the ground 5G terminal preamble at the random access occasion, completes the access detection and conflict resolution, the ground 5G terminal listens to the downlink signaling, obtains and demodulates the ephemeris information to form a directional beam, initiates access at the random access occasion (RO) and completes the access process, after successful access, the low-orbit satellite sends a service start notification to the ground 5G terminal and allocates a beam, starts the service, and recovers the downlink signaling beam until the group of ground 5G terminals completes the service, the ground 5G terminal listens to the downlink signaling, receives it, establishes a communication link and starts transmission, and sends a completion notification after the service is completed.

[0011] Further improvement of the application is that the queue model modeling module includes an access waiting queue and a service waiting queue, in each access cycle, the ground 5G terminal which has not accessed and has service demand enters the access waiting queue, and after completing the access process, the satellite side groups the ground 5G terminals which have successfully accessed according to the wave position and adds them to the service waiting queue, and at the same time, the satellite side removes a group of ground 5G terminals from the service waiting queue according to the number of available service beams and adds them to the service waiting queue, and the ground 5G terminal becomes an unaccessed state after completing the service.

[0012] Further improvement of the application is that the access waiting queue is specifically:

[0013] The ground 5G terminal which has service demand in a single access cycle is added to the access waiting queue g corresponding to the wave position of the ground 5G terminal i (t), i = 1, 2,..., G, g i The recursive relationship of g

[0014] g i (t+1) = max[g i (t)-l i (t), 0] + r i (t)

[0015] Wherein, the value of g i (t) represents the number of ground 5G terminals which have service request in the access cycle t of the wave position i, the initial value g i (0) is 0, r i (t) represents the number of ground 5G terminals which newly initiate service request in the access cycle t of the wave position i, l i (t) represents the maximum number of ground 5G terminals which can access in the access cycle t of the wave position i, and G is the total number of ground wave positions.

[0016] Further improvement of the application is that the service waiting queue modeling is specifically:

[0017] The ground 5G terminals accessing through the same service beam in the same access cycle are regarded as a group, and are added to the service waiting queue s(t) in units of groups. The recursive relationship of the service waiting queue s(t) is expressed as:

[0018] s(t+1) = max[s(t) - z(t), 0] + x(t)

[0019] where x(t) is the number of groups of ground 5G terminals that complete access in the access cycle t, z(t) is the number of groups of ground 5G terminals that complete service in the access cycle t, and is expressed as:

[0020] z(t) = min[s(t), n p (t) - h(t)]

[0021] where n p (t) represents the total number of service beams of the low-orbit satellite communication system in the access cycle t, h(t) represents the number of groups of users that are in communication service transmission at the beginning of the access cycle t, and the initial value h(0) is 0. h(t) is expressed as:

[0022] h(t+1) = max[h(t) - f(t), 0] + z(t)

[0023] where f(t) represents the number of groups of users that complete communication service transmission in the access cycle t, and h(t) satisfies h(t) ≤ n p (t).

[0024] The number of groups of users x(t) that complete access in the access cycle t is expressed as:

[0025]

[0026] The initial value s(0) of the service waiting queue is 0. When the following formula is satisfied, the service waiting queue s(t) is average rate stable:

[0027]

[0028] where s(T) is the value of s(t) when the access cycle t takes the value T, and T represents the Tth access cycle.

[0029] A further improvement of this application is that the beam allocation decision module is used to output the allocation and pointing strategy of the number of satellite-side signaling beams and service beams: the service area of ​​the terrestrial 5G terminal is divided into several beam positions, and in each access cycle, the total number of available beams of the cooperative satellite set is determined, the status of the access waiting queue and the service waiting queue is obtained, a beam allocation decision model is established based on the status of the access waiting queue and the service waiting queue, the beam allocation decision model is transformed and solved, and the allocation and pointing strategy of the number of signaling beams and service beams is determined.

[0030] A further improvement in this application lies in: establishing a beam allocation decision model, transforming and solving the beam allocation decision model, specifically including the following steps:

[0031] Step 2.1: Uniformly select several coordinate points within the rectangular ground region of the service area. Obtain the coordinates of all satellites through constellation configuration. Determine the visible satellites for each selected coordinate point and form a set accordingly. This yields the total number of visible satellites in the region. Determine the actual number of satellites S used to form the cooperative satellite set, where the actual number of satellites S does not exceed the total number of visible satellites in the region. Then, determine the total number of available beams n based on the satellite antenna specifications. total , where n total =S·N 2 N is the number of array elements in each row of the satellite antenna. Proceed to step 2.2.

[0032] Step 2.2: Using a single access period t as the time unit, obtain the access waiting queue g on the satellite side. i The values ​​of s(t), the service waiting queue s(t), and the number of user groups h(t) that are transmitting communication services at the beginning of the access period t are used to proceed to step 2.3.

[0033] Step 2.3: Establish the beam assignment decision model as follows:

[0034]

[0035] Among the independent variables of the beam allocation decision model, n b W(t) represents the signaling beam allocation, and W(t) represents the signaling beam pointing strategy. During access period t, the low-Earth orbit satellite communication system has a total of n service beams. p (t) through n total -n b (t) is obtained, proceed to step 2.4;

[0036] Step 2.4: Optimal value W of signaling beam pointing strategy W(t) * (t) by passing through n b (t) is determined when n is before b (t) the largest gi w corresponding to (t) i Based on the determination of (t) = 1, the beam allocation decision model is optimized, and n is solved. b The optimal number of signaling beams n for (t) b * (t) can be transformed into finding the Lyapunov value function at a fixed access period t. The smallest integer n b The value of (t), Represented as:

[0037]

[0038] in, Indicates that g i (t) Sort in descending order, n b (t)·n ssb =z n +d n , z n d represents the integer part. n To represent the decimal part, such that Take the minimum value n b * (t).

[0039] A further improvement in this application lies in: solving for the optimal number of signaling beams n b * The specific steps for (t) are as follows:

[0040] Step 2.4.1, Input Preparation: Access period t, queue function g i (t), s(t), h(t), maximum number of iterations

[0041] Step 2.4.2, Initialization: Set the golden ratio Define the search region [a, b] as And two initial sampling points x1 = b - (ba)g r x2=a+(ba)g r Calculate the objective function value corresponding to the initial point. Set the search longitude ε = 1;

[0042] Step 2.4.3, Boundary Check: Calculation if but if but

[0043] Step 3.4.4, golden section search: when the interval length |b-a|≥ε, if y1 r , Otherwise, update the left boundary a=x1, update the point x1=x2, y1=y2, and calculate the new point

[0044] Step 2.4.5, determine the optimal solution: calculate the midpoint x m =(x1+x2) / 2, if x m is an integer, then Otherwise, compare the function values of adjacent integer points, that is, if then Otherwise

[0045] Step 2.4.6, output the optimal solution: output the optimal signaling beam number

[0046] Further improvement of the application is that the access flow of the access flow control module is: in each access period, the satellite side generates a downlink signaling beam according to the signaling beam number n b (t) and the signaling beam pointing strategy W(t) according to the signaling beam number n (t) and the signaling beam pointing strategy W(t), receives the ground 5G terminal preamble at the random access occasion, completes the access detection and conflict resolution, and the ground 5G terminal listens to the downlink signaling in an omnidirectional manner, obtains and demodulates the ephemeris information to form a directional beam, initiates access at the random access occasion (RO) and completes the access process, after successful access, the satellite side sends a service start notification to the terminal side and allocates a beam, starts the service, and recovers the downlink signaling beam until the group of ground 5G terminals completes the service, the ground 5G terminal listens to the notification, establishes a communication link after receiving it and starts transmission, and sends a completion notification after the service is completed.

[0047] Further improvement of the application is that the access flow of the access flow control module specifically includes the following steps:

[0048] Step 3.1, signaling transmission: in each access period t, the satellite side generates a plurality of downlink signaling beams pointing to the wave position according to the optimal signaling beam number n output by the controller and the optimal signaling beam pointing strategy W * (t), sends downlink signaling information to the wave position through the downlink signaling beam, and the terminal with service demand listens to the synchronization signal block (SSB), synchronizes through the synchronization signal block (SSB) and demodulates the ephemeris information in the physical downlink shared channel (PDSCH), and enters step 3.2;

[0049] Step 3.2, random access: after the terminal listens to and demodulates the downlink signaling message, a beam pointing to the satellite, i.e., a directional beam, is generated with the assistance of the ephemeris information demodulated in step 3.1, and a preamble is sent through the directional beam at a random access occasion (RO) corresponding to the selected SSB signal to initiate random access, and the satellite processes the random access request from the terminal side, thus completing the fast beam alignment, and after completing the remaining random access process, entering step 3.3;

[0050] Step 3.3, start service: in each access period t, the satellite side acquires the number of service beams available in the current access period, and takes out a terminal group of the number of available service beams from the service waiting queue, and sends a service start notification to the terminals in the terminal group, and enters step 3.4;

[0051] Step 3.4: continuous service: the ground 5G terminal forms a beam tracking the satellite according to the ephemeris information of the accessed satellite, and listens to the service start notification on the time-frequency resource specified during access, and once it is listened to, a communication link with the satellite is established, and the service is continuously performed, and enters step 3.5;

[0052] Step 3.5: end of service: after the ground 5G terminal completes the required service, it sends a service end notification to the satellite side on the corresponding time-frequency resource, and after receiving it, the satellite side disconnects the communication link with the ground 5G terminal, and when all ground 5G terminals in a ground 5G terminal group served by a service beam have ended the service, the satellite side recovers the service beam.

[0053] The beneficial effects of the present application are: the present application proposes a fast beam alignment method assisted by ephemeris information using narrow beams and a beam number and pointing strategy decision method to solve the problems of low initial access efficiency and untimely beam alignment in a low-orbit satellite communication system integrated with 5G, and improves the access efficiency and service carrying capacity between the satellite and the ground terminal.

[0054] The present application introduces a queue model, constructs an optimization objective function of maximizing the number of access terminals per access period under the condition of queue stability, and forms an efficient online algorithm by transforming the Lyapunov function and using the golden section method. The algorithm can dynamically determine the number allocation and pointing strategy of the signaling beam, realize fast beam allocation and resource utilization.

[0055] The present application constructs a complete access beam management process through three modules of access process optimization design, queue mathematical model establishment, and beam allocation strategy decision.

[0056] The present application not only realizes the end-to-end fast access of low-orbit satellites and ground terminals, but also ensures good performance in terms of average waiting time of terminal service and total completed service volume in a limited time.​ Attached Figure Description

[0057] Figure 1 This is a flowchart of the specific process of this application.

[0058] Figure 2 This is the flowchart for this application.

[0059] Figure 3 This is a comparison chart of the average service waiting time of the terminal under different total number of beams for this application and the comparative method.

[0060] Figure 4 This is a comparison chart of the total number of services completed by this application and the comparative method under different total number of beams. Detailed Implementation

[0061] The embodiments of the present invention will be disclosed below with reference to the drawings. For clarity, many practical details will be described in the following description. However, it should be understood that these practical details are not intended to limit the invention. That is, in some embodiments of the invention, these practical details are not essential.

[0062] like Figures 1-2 As shown, this application discloses an initial access beam management method for a low-Earth orbit (LEO) satellite communication system integrating 5G. In an LEO satellite communication system composed of a terrestrial 5G terminal and a LEO satellite equipped with a controller, the initial access beam management method is implemented through a beam management system. The beam management system includes a queue model modeling module, an access process control module, and a beam allocation decision module. The queue model modeling module divides the ground area into beam positions and constructs a queue model. The queue model modeling module includes an access waiting queue and a service waiting queue. The LEO satellite controller makes beam allocation decisions according to the beam allocation decision module. The LEO satellite equipped with the controller and the terrestrial 5G terminal access each other according to the process designed by the access process control module.

[0063] like Figure 1 As shown, the queue modeling module includes an access waiting queue and a service waiting queue. In each access cycle, terrestrial 5G terminals that have not yet accessed the network but have service needs enter the access waiting queue. After the access process is completed, the satellite side groups the successfully accessed terrestrial 5G terminals by waveband and adds them to the service waiting queue. At the same time, the satellite side removes several terrestrial 5G terminal groups from the service waiting queue and adds them to the service waiting queue according to the number of available service beams. After the terrestrial 5G terminal completes the service, it returns to the unaccessed state.

[0064] like Figure 1As shown, the beam allocation decision module is used to output the satellite side signaling beam and the number of service beam allocation and pointing strategy: the to-be-served area of the ground 5G terminal is divided into a plurality of wave positions, in each access cycle, the total number of available beams of the cooperative satellite set is determined, the states of the access waiting queue and the service waiting queue are obtained, the beam allocation decision model is established based on the states of the access waiting queue and the service waiting queue, the beam allocation decision model is transformed and solved, and the number allocation and pointing strategy of the signaling beam and the service beam are determined.

[0065] As shown in Figure 1 , the access flow control module has an access flow: in each access cycle, the satellite side generates a downlink signaling beam according to the number of signaling beams n b (t) and the signaling beam pointing strategy W(t), receives the preamble of the ground 5G terminal at the random access occasion, completes the access detection and conflict resolution, the ground 5G terminal listens to the downlink signaling in an omnidirectional manner, obtains and demodulates ephemeris information to form a directional beam, initiates access at the random access occasion (RO) and completes the access process, after successful access, the satellite side sends a service start notification to the terminal side and allocates a beam, starts service, and recovers the downlink signaling beam until all the ground 5G terminals in the group complete the service, the ground 5G terminal listens to the notification, establishes a communication link after receiving it and starts transmission, and sends a completion notification after the service is completed.

[0066] As shown in Figures 1-2 , the beam management method of the present application specifically includes the following steps:

[0067] Step 1, the to-be-served area of the ground 5G terminal is divided into a plurality of wave positions, and the queue model modeling module divides the plurality of wave positions and constructs a queue model;

[0068] The wave position is divided into: the coverage radius of the low-orbit satellite beam can be expressed as:

[0069]

[0070] Wherein, L tar represents the distance between the satellite and the target position, d represents the distance between the elements, and generally satisfies λ c represents the carrier wavelength. Referring to the coverage radius R of the low-orbit satellite beam, one beam can cover one rectangular wave position, the ground area is divided into G ground wave positions, and the service arrival statistical parameter λ i of each wave position is determined according to the ground wave position division.

[0071] In this step, the access waiting queue is specifically:

[0072] Add the 5G terminal with service demand in a single access cycle to the access waiting queue g corresponding to the wavelength of the 5G terminal. i (t), i = 1, 2, ... G, g i The recurrence relation of (t) is expressed as:

[0073] g i (t+1)=max[g i (t)-l i (t),0]+r i (t)

[0074] Among them, g i The value of (t) represents the number of terrestrial 5G terminals with service requests at wavelength i during access period t, with an initial value of g. i (0) is 0, r i (t) represents the number of terrestrial 5G terminals that initiate new service requests at position i during access period t, l i (t) represents the maximum number of terrestrial 5G terminals that can be accessed at wave position i during access period t, where G is the total number of terrestrial wave positions.

[0075] Let w i (t)∈{0,1} indicates whether position i is illuminated by a signaling beam during access period t, and the number of SSBs transmitted in time division during one access period is n. ssb The system has n signaling beams during access period t. b (t), then the following equation holds:

[0076]

[0077] Specifically, the business waiting queue modeling is as follows:

[0078] Terrestrial 5G terminals accessing the same service beam within the same access cycle are considered a group and added to the service waiting queue s(t) as a group. The recursive relationship of the service waiting queue s(t) is expressed as follows:

[0079] s(t+1)=max[s(t)-z(t),0]+x(t)

[0080] Where x(t) is the number of terrestrial 5G terminal groups that complete access during access period t, and z(t) is the number of terrestrial 5G terminal groups that end service during access period t, expressed as:

[0081] z(t) = min[s(t), n p (t)-h(t)]

[0082] Where, n p(t) represents the total number of traffic beams possessed by the low-orbit satellite communication system in the access period t, h(t) represents the number of user groups in communication traffic transmission at the beginning of the access period t, and the initial value h(0) is 0, and h(t) is represented as follows:

[0083] h(t+1) = max [h(t) - f(t), 0] + z(t)

[0084] wherein f(t) represents the number of user groups completing the communication traffic transmission in the access period t, and h(t) satisfies h(t)≤n p (t) ;

[0085] The number of user groups x(t) completing the access in the access period t is represented as follows:

[0086]

[0087] The initial value s(0) of the traffic waiting queue is 0, and the traffic waiting queue s(t) is average rate stable when the following formula is satisfied:

[0088]

[0089] wherein s(T) is the value of s(t) when the access period t takes the value of T, and T represents the Tth access period.

[0090] Step 2, in each access period, the beam allocation decision module obtains the states of the access waiting queue and the traffic waiting queue, establishes a beam allocation decision model based on the states of the access waiting queue and the traffic waiting queue, transforms and solves the beam allocation decision model, and determines the signaling beam quantity allocation and the signaling beam pointing strategy.

[0091] The beam allocation decision specifically includes the following steps:

[0092] Step 2.1, for a ground terminal with a latitude and longitude position of and an altitude of 0 and a low-orbit satellite with a latitude and longitude position of and an orbit height of H, the geocentric angle θ between the satellite and the terminal can be calculated through the spherical triangle formula:

[0093]

[0094] The geocentric angle condition for communication is satisfied as follows:

[0095]

[0096] wherein θ max is the maximum communication elevation angle of the ground terminal and the satellite, R e represents the earth radius, and R srepresents the satellite geocentric distance and satisfies R s = R e + H.

[0097] In the ground rectangular area of the area to be served, a plurality of coordinate points are uniformly selected, the coordinate points of all satellites are obtained through constellation configuration, the visible satellites of each coordinate point selected are respectively judged to form a set in turn, that is, the total visible satellite number of the area is obtained, the satellite number S actually used is determined to form a cooperative satellite set, wherein the satellite number S actually used is not more than the total visible satellite number of the area, and the total available beam number n is determined according to the satellite antenna size total , wherein n total = S·N 2 , N is the number of array elements in each row of the satellite antenna, and step 2.2 is entered;

[0098] Step 2.2: in a single access period t as a time unit, the value of the access waiting queue g i (t), the value of the service waiting queue s(t), and the value of the number of user groups h(t) that are in communication service transmission at the beginning of the access period t are obtained at the satellite side, and step 2.3 is entered;

[0099] Step 2.3: a beam allocation decision model is established as follows:

[0100]

[0101] Among them, n b (t) in the independent variable of the beam allocation decision model represents the number allocation of the signaling beam, W(t) represents the signaling beam pointing strategy, and the total number of service beams n p (t) of the low-orbit satellite communication system at the access period t is obtained through n total -n b (t), and step 2.4 is entered;

[0102] Step 2.4, the optimal value W * (t) of the signaling beam pointing strategy W(t) is determined by setting w b (t) = 1 corresponding to the largest g b (t) in the n i (t) determined, and the beam allocation decision model is optimized on this basis to solve the optimal signaling beam number n i (t) of n b (t), b * (t) is converted into the value of n b (t) that minimizes the Lyapunov value function and is an integer that can be obtained at the fixed access period t, is represented as:

[0103]

[0104] wherein, g i (t) is sorted in descending order, n b (t)·n ssb = z n +d n , z n denotes the integer part, d n denotes the decimal part, such that n b * (t) takes the minimum value.

[0105] wherein the specific steps for solving the optimal signaling beam number n b * (t) are as follows:

[0106] Step 2.4.1, input preparation: access period t, queue function g i (t), s(t), h(t), maximum iteration step

[0107] Step 2.4.2, initialization: set the golden ratio define the search region [a, b] as and two initial sampling points x1 = b - (b - a)g r , x2 = a + (b - a)g r , calculate the target function value corresponding to the initial points set the search longitude ε = 1;

[0108] Step 2.4.3, boundary check: calculate if then if then

[0109] Step 3.4.4, golden section search: when the interval length |b - a| ≥ ε, if y1 < y2, update the boundary b = x2, update the point x2 = x1, y2 = y1, calculate the new point x1 = b - (b - a)g r , otherwise, update the left boundary a = x1, update the point x1 = x2, y1 = y2, calculate the new point x2 = a + (b - a)g τ ,

[0110] Step 2.4.5, determine the optimal solution: calculate the midpoint x m = (x1 + x2) / 2, if x m is an integer, then Otherwise compare the function values of the adjacent integer points, that is, if Otherwise

[0111] Step 2.4.6, output the optimal solution: output the optimal signaling beam number

[0112] Step 3, in each access period, the satellite side generates a downlink signaling beam according to the signaling beam number determined in step 2 and the signaling beam pointing strategy, the ground 5G terminal listens to the downlink signaling, obtains and demodulates the ephemeris information to form a directional beam, initiates access at the random access occasion (RO) and completes the access process, after successful access, the low-orbit satellite sends a service start notification to the ground 5G terminal and allocates a beam, starts the service, and recycles the downlink signaling beam until the ground 5G terminal completes the service, the ground 5G terminal listens to the downlink signaling, receives it, establishes a communication link and starts transmission, and sends a completion notification after the service is completed.

[0113] The access process of the access process control module specifically includes the following steps:

[0114] Step 3.1, signaling transmission: in each access period t, the satellite side generates a plurality of downlink signaling beams pointing to the wave position according to the optimal signaling beam number output by the controller and the optimal signaling beam pointing strategy W * (t), sends downlink signaling information to the wave position through the downlink signaling beam, and the signaling information includes SSB signal, PDCCH and PDSCH, wherein the ephemeris information is also carried in the PDSCH. The terminal with service demand listens to the synchronization signal block (SSB), synchronizes through the synchronization signal block (SSB) and demodulates the ephemeris information in the physical downlink shared channel (PDSCH), and enters step 3.2;

[0115] Step 3.2, random access: after the terminal listens to and demodulates the downlink signaling message, a beam pointing to the satellite, that is, a directional beam, is generated under the assistance of the ephemeris information demodulated in step 3.1, and a preamble is sent through the directional beam at the random access occasion (RO) corresponding to the selected SSB signal to initiate random access, the satellite processes the random access request from the terminal side, and thus the fast beam alignment is completed, and after completing the remaining random access process, it enters step 3.3; the remaining access process is as follows: the satellite sends a Msg2 message to the corresponding wave position, the ground 5G terminal receives the Msg2 message and processes it, and then sends a Msg3 message to the satellite to apply for time-frequency resources, the satellite receives the Msg3 message, and performs time-frequency resource allocation notification and conflict resolution by sending a Msg message. The terminal that successfully completes the above steps with the satellite successfully accesses.

[0116] ​Step 3.3, start service: at each access period t, the satellite side acquires the number of service beams available in the current access period, and takes out a terminal group of the number of available service beams from the service waiting queue, and sends a service start notification to the terminals in the terminal group, and enters step 3.4; acquire the number of service beams available in the current access period, and take out a terminal group of the number of available service beams from the service waiting queue, and send a service start notification to the terminals in the terminal group, and enter step 3.4;

[0117] Step 3.4: continue service: the ground 5G terminal forms a beam tracking the satellite according to the ephemeris information of the accessed satellite, and listens to the service start notification on the time-frequency resource specified when accessing, and once it is listened to, it establishes a communication link with the satellite, and continues to perform service, and enters step 3.5;

[0118] Step 3.5: end service: after the ground 5G terminal completes the required service, it sends a service end notification to the satellite side on the corresponding time-frequency resource, and the satellite side receives it and disconnects the communication link with the ground 5G terminal. When all ground 5G terminals in a terminal group served by a service beam end the service, the satellite side recovers the service beam.

[0119] The beam management algorithm of the present application is Figure 3 It is shown that when the total number of available beams n total takes different values, the performance of different algorithms in the average service waiting time of the terminal, the shorter the average service waiting time of the terminal, the better the performance. In the figure, the LYP-IABM algorithm corresponds to the beam management algorithm of the present application, and the other four algorithms are comparative algorithms, and their meanings are as follows: TN5G-IABM is a beam management algorithm of a traditional ground 5G system, S-IABM is a beam management algorithm with fixed allocation of beam number, FD-IABM is an online beam management algorithm based on feedback control, and DPV-IABM is an online beam management algorithm based on value function dynamic programming. As can be seen from Figure 3 , the beam management algorithm proposed in the present application has the best performance.

[0120] Figure 4 It is shown that when the total number of available beams n total takes different values, the performance of different algorithms in the total number of terminal users completing service, the more the total number of terminal users completing service, the better the performance. In the figure, the LYP-IABM algorithm corresponds to the beam management algorithm of the present application, and the other four algorithms are comparative algorithms, and their meanings are as follows: TN5G-IABM is a beam management algorithm of a traditional ground 5G system, S-IABM is a beam management algorithm with fixed allocation of beam number, FD-IABM is an online beam management algorithm based on feedback control, and DPV-IABM is an online beam management algorithm based on value function dynamic programming. As can be seen from Figure 4 , the beam management algorithm proposed in the present application has the best performance.

[0121] LYP-IABM algorithm, FD-IABM algorithm, DPV-IABM algorithm all belong to online algorithm, the other two algorithms are offline algorithm, as can be seen from Figure 3 and Figure 4 , the online algorithm has much higher performance than the offline algorithm.

[0122] Table 1

[0123] Online algorithm Run time (seconds) LYP-IABM algorithm (present application) 0.2867 FD-IABM algorithm 10.6475 DPV-IABM algorithm 102.3714

[0124] The running time of simulating 1000 access cycles of three online algorithms on the same hardware platform is shown in Table 1, and it can be seen from Table 1 that the LYP-IABM algorithm proposed in the application has the optimal time complexity performance.

[0125] The above merely describes the embodiments of the present application and is not intended to limit the present application. The present application can have various modifications and changes for those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the scope of claims of the present application.

Claims

1. A method for initial access beam management of a 5G integrated low earth orbit satellite communication system, in a low earth orbit satellite communication system composed of a low earth orbit satellite equipped with a controller and a ground 5G terminal, the method for initial access beam management is implemented by a beam management system, characterized in that: The beam management system comprises a queue model modeling module, an access flow control module and a beam allocation decision module, the queue model modeling module divides wave positions of a ground area and constructs a queue model, the queue model modeling module comprises an access waiting queue and a service waiting queue, a controller of a low-orbit satellite makes a beam allocation decision according to the beam allocation decision module, the low-orbit satellite equipped with the controller accesses with a ground 5G terminal according to a flow designed by the access flow control module, and specifically, the beam management method specifically comprises the following steps: ​ Step 1, a to-be-served area of the ground 5G terminal is divided into a plurality of wave positions, the queue model modeling module divides the plurality of wave positions and constructs a queue model; Step 2, in each access cycle, the beam allocation decision module obtains the states of the access waiting queue and the service waiting queue, a beam allocation decision model is established based on the states of the access waiting queue and the service waiting queue, the beam allocation decision model is transformed and solved, and the number allocation and pointing strategy of the signaling beam are determined; Step 3, the access flow control module completes the access flow: in each access cycle, the satellite side generates a downlink signaling beam according to the number allocation and pointing strategy of the signaling beam determined in step 2, and receives a preamble of the ground 5G terminal at a random access opportunity, completes access detection and conflict resolution, the ground 5G terminal listens to the downlink signaling, obtains and demodulates ephemeris information to form a directional beam, initiates access at a random access opportunity (RO) and completes the access process, after successful access, the low-orbit satellite sends a service start notification to the ground 5G terminal and allocates a beam, starts service, and recovers the downlink signaling beam until all the ground 5G terminals in the group complete the service, the ground 5G terminal listens to the downlink signaling, receives it to establish a communication link and start transmission, and sends a completion notification after the service is completed; wherein: The beam allocation decision specifically comprises the following steps: Step 2.1, for a ground terminal with latitude and longitude position and an elevation of 0 and a low earth orbit satellite with latitude and longitude position and an orbital height of the geocentric angle between the satellite and the terminal can be calculated by the spherical triangle formula: It satisfies the geocentric angle condition of communication: wherein, is the maximum communication elevation angle of the ground terminal with the satellite, denotes the earth radius, denotes the satellite geocentric distance and satisfies ; Uniformly select several coordinate points in the ground rectangular area of the area to be served, obtain the coordinate points of all satellites through constellation configuration, respectively judge the visible satellites of each coordinate point selected, sequentially form a set, that is, obtain the total visible satellite number of the area, determine the actual number of satellites used Form a cooperative satellite set, wherein the actual number of satellites used does not exceed the total visible satellite number of the area, and then determine the total available beam number according to the satellite antenna size , wherein , is the number of array elements in each row of the satellite antenna, and step 2.2 is entered. Step 2.2: In a single access period in time units, the value of the access waiting queue at the satellite side , the value of the traffic waiting queue , and the value of the number of user groups that are in the middle of a traffic transmission at the beginning of the access period Step 2.3 Step 2.3: In a single access period Step 2.3: the beam allocation decision model is established as follows: wherein the independent variables of the beam allocation decision model comprise representing the number allocation of signaling beams, representing the signaling beam pointing strategy, at the access period the total number of traffic beams of the low earth orbit satellite communication system by goes to step 2.

4. Step 2.4, Signaling beam pointing strategy optimal value by determining the determined at the time largest corresponding to determine, on this basis, the beam allocation decision model, to solve optimal signaling beam number transformed into a fixed access cycle obtained to make the Lyapunov value function minimum and integer value, represented as: wherein, denotes the descending order, , denotes the integer part, denotes the decimal part, such that the minimum value ; Solving optimal signaling beam number The specific steps are as follows: Step 2.4.1, Input preparation: access period , queue function , , , maximum number of iteration steps ; Step 2.4.2, Initialization: Set the golden ratio , define the search region for and two initial sample points , , compute the objective function values for the initial points , , set the search longitude ; Step 2.4.3, Boundary Check: Compute , , , if then if then ; Step 3.4.

4. Golden section search: When the interval length is , then update the right boundary , update the point , , calculate the new point , , else update the left boundary , update the point , , calculate the new point , ; Step 2.4.

5. Determining the optimal solution: computing the midpoint If is an integer, then , otherwise compare the function values at the adjacent integer points, i.e. if then , otherwise ; Step 2.4.6, output optimal solution: output optimal number of signaling beams . 2.The initial access beam management method for a 5G integrated low earth orbit satellite communication system of claim 1, wherein: In each access cycle, the ground 5G terminal that has not accessed and has a service demand enters the access waiting queue, and after completing the access flow, the satellite side groups the ground 5G terminals that have successfully accessed according to wave positions and adds them to the service waiting queue, and at the same time, the satellite side removes a plurality of groups of ground 5G terminals from the service waiting queue according to the number of available service beams and adds them to the service waiting queue, and the ground 5G terminal becomes an unaccessed state after completing the service. 3.The initial access beam management method for a 5G integrated low earth orbit satellite communication system of claim 2, wherein: The access waiting queue is specifically: A single access cycle has a service demand of ground 5G terminal, join the access waiting queue corresponding to the wave position of the ground 5G terminal , , The recursive relationship of the above formula is expressed as: wherein, the value of the wave position in the access period the number of ground 5G terminals that have a service request, the initial value is 0, the value of the wave position in the access period the number of ground 5G terminals that newly initiate a service request, the value of the wave position in the access period the maximum number of ground 5G terminals that can access, is the total number of ground wave positions. 4.The method of claim 3, wherein: The service waiting queue is modeled as: Ground 5G terminals accessing through the same service beam in the same access cycle are considered as a group, and are added to the service waiting queue in units of groups , the recursive relationship of the service waiting queue is expressed as: wherein, is the number of ground 5G terminals that have completed access in the access period is the number of groups of ground 5G terminals that have completed access, is the number of ground 5G terminals that have completed access in the access period is the number of groups of ground 5G terminals that have completed service, and is represented by: wherein, denotes the access period the total number of traffic beams of the low earth orbit satellite communication system, denotes the access period the number of user groups that are in the middle of communication traffic transmission at the start, which is initially set to 0, denotes the following: wherein, represents the number of user groups that complete communication service transmission within an access period, satisfies ;​ In the access period Number of user groups completing access is expressed as: Initial value of the service queue is 0, and when the following equation is satisfied, then the service queue is average rate stable: wherein, is the access period is the value is the value is the value is the value is the value 5. The initial access beam management method for a 5G integrated low earth orbit satellite communication system according to claim 4, wherein: The beam allocation decision module is used to output the number allocation and pointing strategy of the satellite side signaling beam and service beam: the to-be-served area of the ground 5G terminal is divided into a plurality of wave positions, in each access cycle, the total number of available beams of the cooperative satellite set is determined, the states of the access waiting queue and the service waiting queue are obtained, a beam allocation decision model is established based on the states of the access waiting queue and the service waiting queue, the beam allocation decision model is transformed and solved, and the number allocation and pointing strategy of the signaling beam and the service beam are determined. 6.The initial access beam management method for a 5G integrated low earth orbit satellite communication system of claim 1, wherein: The access procedure of the access procedure control module comprises the following steps in particular: Step 3.1, Signaling transmission: In each access cycle The satellite side determines the optimal number of signaling beams based on the controller output. and optimal signaling beam pointing strategy Several downlink signaling beams pointing to the wave positions are generated. Downlink signaling information is sent to the wave positions through the downlink signaling beams. Terminals with service requirements listen to the synchronization signal block (SSB), synchronize through the synchronization signal block (SSB), and demodulate the ephemeris information in the physical downlink shared channel (PDSCH). Proceed to step 3.

2. Step 3.2, random access: after the terminal listens to and demodulates the downlink signaling message, a beam pointing to the satellite, i.e. a directional beam, is generated under the assistance of the ephemeris information demodulated in step 3.1, and a preamble is sent through the directional beam at a random access occasion (RO) corresponding to the selected SSB signal to initiate random access. The satellite processes the random access request from the terminal side, and thus the fast beam alignment is completed. After completing the remaining random access procedure, step 3.3 is entered. Step 3.3, Start service: at each access period , the satellite side acquires the number of service beams available in the current access period, and takes out a terminal group of the number of available service beams from the service waiting queue, and sends a service start notification to the terminals in the terminal group, and enters Step 3.

4. Step 3.4, Send service start notification: the satellite side sends a service start notification to the terminals in the terminal group, and enters Step 3.

5. Step 3.4: continuous service: the ground 5G terminal forms a beam tracking the satellite according to the ephemeris information of the accessed satellite, listens to the service start notification on the time-frequency resource specified during access, and establishes a communication link with the satellite as soon as it is listened to, to continuously perform service, and enters step 3.5; Step 3.5: end of service: after the ground 5G terminal completes the required service, it sends a service end notification to the satellite side on the corresponding time-frequency resource. After receiving it, the satellite side disconnects the communication link with the ground 5G terminal. When all ground 5G terminals in a group of ground 5G terminals served by a service beam end the service, the satellite side recovers the service beam.

Images