Satellite communication access method

Abstract

The invention discloses a satellite communication access method, which comprises the following steps that: a user sends an access signaling to a satellite in a time frame access stage of the satellite, and completes initial access according to a beam selection strategy; the time frame comprises the access stage, the channel allocation stage and the communication stage; the satellite carries out channel allocation on all beam services according to the number of users newly accessed by each beam service in the access stage of the current time frame; wherein channel allocation is modeled as a coloring problem of a graph theory, and node coloring is determined by utilizing a Welsh-Powell algorithm based on node weights, so that channel allocation is realized; the satellite sends a channel allocation result of the beam service to the accessed user of each beam service, and allocates a corresponding communication time slot for the accessed user; and the user completes data transmission in a communication stage according to the channel corresponding to the accessed beam service and the allocated time slot. According to the invention, interference between beam services can be reduced, and user communication quality is improved.

Description

Technical Field

[0001] The present invention relates to the field of satellite communication, and relates to a satellite communication access method, which can be used in satellite-assisted communication scenarios in areas where it is difficult to deploy base stations, such as mountainous areas and oceans. Background Art

[0002] In recent years, with the rapid development of wireless communication technology, satellite communication network technology has become a powerful supplement and extension of traditional terrestrial cellular networks due to its advantages such as wide coverage, large communication capacity, and good transmission quality. At the same time, in order to solve the problem of limited frequency band resources of single-beam satellites, multi-beam satellites with two characteristics of beam space isolation and frequency reuse have become the main research direction at present.

[0003] In the process of multi-beam satellite-assisted communication, due to the smaller coverage area of the beam, users face more frequent beam switching, resulting in problems such as an increase in the service interruption probability and access delay. In addition, users are unevenly distributed within the satellite coverage area. If multi-beam full frequency reuse is adopted, the beam interference problem is serious, affecting the user communication quality. Therefore, how users perform efficient beam switching and how satellites design channel allocation strategies to avoid interference and achieve efficient resource utilization have become one of the research hotspots. Summary of the Invention

[0004] The purpose of the present invention is to provide a satellite communication access method to reduce the interference between beam services and improve the user communication quality.

[0005] To achieve the above task, the present invention adopts the following technical solutions:

[0006] A satellite communication access method includes:

[0007] A user sends an access signaling to a satellite during the time frame access stage of the satellite, and completes initial access according to a beam selection strategy; the time frame includes the access stage, the channel allocation stage, and the communication stage; in the beam selection strategy, the user first determines whether there is a beam service. When there is no beam service, the user realizes initial access by means of the beam service of a neighbor node. When there is one beam service, there is no need to update the communication time slot. When there are multiple beams, the user determines which beam service to select for initial access by calculating the weight value of the beam service;

[0008] The satellite performs channel allocation for all beam services according to the number of newly accessed users of each beam service in the access stage of the current time frame; among them, the channel allocation is modeled as a coloring problem of graph theory, and the Welsh-Powell algorithm based on node weight is used to determine the coloring of each node to achieve channel allocation;

[0009] The satellite sends the channel allocation result of the beam service to the users accessed by each beam service, and allocates corresponding communication time slots to the accessed users;

[0010] The users complete data transmission in the communication phase according to the channels corresponding to the beam services they access and the allocated time slots.

[0011] Furthermore, the user first determines whether it has a beam service. When there is no beam service, it realizes initial access by means of the beam service of the neighbor nodes, including:

[0012] The user determines whether it has a beam service; if not, the user broadcasts an inquiry message to the neighbor nodes to determine whether they have a beam service. The neighbor nodes that receive the inquiry message send a confirmation reply frame to the user. The user selects and determines the neighbor nodes with beam services through the confirmation reply frame, and selects the neighbor node that first replies the confirmation reply frame from these neighbor nodes, and sends an access short frame to the neighbor node to indicate joining the beam service where the neighbor node is located;

[0013] If it is determined through the confirmation reply frame that all neighbor nodes do not have a beam service, a cluster network is formed by the user and its neighbor nodes. The nodes in the cluster network randomly select a channel and randomly select a time slot to send an access signaling; if a certain node in the cluster successfully accesses a certain beam service, the entire cluster network accesses the beam service.

[0014] Furthermore, when there is one beam service, there is no need to update the communication time slot, including:

[0015] The user determines whether it has multiple beam services; if there is only one beam service, it means that this beam service is the same as the beam service where the user was located in the previous time frame. The user selects this beam service to complete the initial access; for this beam service, the user is called an old user; the user reports the old user identifier to the satellite. After the satellite obtains the old user identifier, when performing communication time slot allocation in the channel allocation phase of the current time frame, the communication time slot allocated to the user in the channel allocation phase of the previous time frame is kept unchanged and is continued to be allocated to the user.

[0016] Furthermore, when there are multiple beams, the weight of the beam service is calculated to determine which beam service to select for initial access, including:

[0017] The user calculates the weight α based on the data in the access status frame sent by the satellite, including the remaining service time T i of the beam service, the number of users M currently accessing the beam service i and calculates the weight α, and selects the beam service with the largest weight to complete the initial access; the weight calculation is as follows:

[0018]

[0019] Further, modeling the channel allocation as a graph theory coloring problem specifically includes:

[0020] Construct an undirected graph G = (V, E); where V is the set of nodes, and the periodic beam services in the current time frame are used as nodes; E is the set of edges; if there is an edge between two nodes, it indicates that there is an overlap between the two beam services.

[0021] Further, using the Welsh-Powell algorithm based on node weights to determine the coloring of each node so as to achieve channel allocation includes:

[0022] (1) Determine the number of colors allocated in each round, that is, the number of channels in different frequency bands allocated within the beam service;

[0023] (2) Start coloring the nodes in descending order of the node weights in the undirected graph. Use the node with the highest node weight as the first node, and sequentially traverse all nodes with non-zero node weights in the undirected graph; if the currently traversed node is not adjacent to all nodes with the same color as the first node, then color the currently traversed node with the same color as the first node; if adjacent, select another color to color the currently traversed node.

[0024] (3) Different colors in the undirected graph represent different allocated channels. After all nodes in a round are traversed, the node weight of each node is reduced by 1, and all nodes with a node weight of 0 are removed;

[0025] (4) For all the remaining nodes, determine the number of colors allocated in the next round according to the method in step (1), and perform the next round of color allocation until all nodes are colored or all node weights are 0.

[0026] Further, the calculation method of the node weight is:

[0027]

[0028] Among them, β is the node weight, K is the number of beam services in the satellite, and M is the number of available channels for full-frequency reuse in the beam service.

[0029] Further, the process of determining the number of colors allocated in the current round is:

[0030] First, arrange the nodes of the current undirected graph in descending order of degrees; when the degrees of two nodes are the same, arbitrarily specify the front and back order of these two nodes; denote the sorted node numbers as i;

[0031] Second, determine a calculated value for each node according to the formula min{dig(v i ) + 1, i}; where dig(vi ) represents the degree of the i-th node;

[0032] Finally, select the largest calculated value from all the calculated values as the number of colors allocated in the current round.

[0033] Furthermore, when there are multiple channels allocated for a beam service, the satellite allocates channels and communication time slots to users in the order of user access to the beam service.

[0034] A terminal device includes a processor, a memory, and a computer program stored in the memory; when the processor executes the computer program, the satellite communication access method is implemented.

[0035] A computer-readable storage medium stores a computer program; when the computer program is executed by a processor, the satellite communication access method is implemented.

[0036] Compared with the prior art, the present invention has the following technical features:

[0037] The present invention improves the efficiency of users accessing the satellite to realize data forwarding and processing, optimally selects beams through parameters such as remaining service time and the number of served users, and reduces the probability of service interruption; in addition, considering the interference effect of full-band reuse between beams, a Welsh-Powell algorithm based on point weights is designed to allocate channels in different frequency bands for each beam service, reduce the interference between beams, and achieve load balancing and low-latency and high-efficiency access for users. Description of the Drawings

[0038] Figure 1 is the system scenario diagram of the present invention;

[0039] Figure 2 is the time frame process and frame structure design;

[0040] Figure 3 is the user beam selection flowchart in the access stage;

[0041] Figure 4 is the establishment of an undirected graph in the channel allocation stage in an embodiment of the present invention;

[0042] Figure 5 is the channel allocation process in an embodiment of the present invention, where (a) is the allocation result of the first round and (b) is the allocation result of the second round. Detailed Embodiment

[0043] The present invention provides a satellite communication access method. This strategy is based on a hybrid protocol framework of TDMA + FDMA and mainly includes two parts: user beam selection and satellite channel allocation. First, a user beam selection algorithm based on the remaining service time and the number of users within a beam is introduced, which is beneficial to load balancing. After the satellite determines the number of users served by each beam in this period, it performs channel allocation for beam services to reduce interference between beams and improve the communication quality of users.

[0044] Step 1: Assume that a single satellite has K beam services, and each beam has M available channels under full-band reuse. Users are randomly distributed in the coverage area of the satellite.

[0045] Step 2: A cycle of the satellite time frame is divided into an access stage, a channel allocation stage, and a communication stage. During the channel allocation stage, the satellite allocates communication time slots for currently accessing users. Users send access signaling to the satellite during the access stage of the time frame and complete initial access according to the user beam selection strategy.

[0046] To improve the access efficiency of handover users and new users, this solution provides a user beam selection strategy, and the specific steps are as follows:

[0047] (2-1) The user determines whether it has beam service. If so, execute step (2-2); otherwise, the user broadcasts an inquiry message to neighbor nodes (other users) to determine whether they have beam service. The neighbor nodes that receive the inquiry message send a confirmation reply frame to the user. The user selects and determines the neighbor nodes with beam service through the confirmation reply frame, and selects the neighbor node that first replies with the confirmation reply frame from these neighbor nodes, and sends an access short frame to this neighbor node to indicate joining the beam service where the neighbor node is located.

[0048] If it is determined through the confirmation reply frame that all neighbor nodes do not have beam service, the user and its neighbor nodes form a cluster network. The nodes in the cluster network randomly select a channel and a time slot to send access signaling. If a certain node in the cluster successfully accesses a certain beam service, then the entire cluster network accesses this beam service.

[0049] Among them, user access is divided into two types: inter-satellite handover and intra-satellite handover. Inter-satellite handover involves handover between different satellite beam services and includes inter-satellite links. Intra-satellite handover only involves handover between different beam services in the satellite. These two situations should also be included when the user makes a beam service judgment in this step.

[0050] (2-2) The user determines whether they have multiple beam services; if there are multiple beams, then execute (2-3); if there is only one beam service, it indicates that this beam service is the same as the beam service the user was in during the previous time frame. The user selects this beam service to complete the initial access; for this beam service, this user is called an old user; the user reports the old user identifier to the satellite, including the user ID and the identification information flag; after the satellite obtains the old user identifier, when performing communication time slot allocation during the channel allocation phase of the current time frame, keep the communication time slot allocated to the user during the channel allocation phase of the previous time frame unchanged and continue to allocate it to this user without updating the communication time slot.

[0051] (2-3) The user calculates the weight α based on the data in the access status frame sent by the satellite, including the remaining service time T i of the beam service, and the number of users M i currently accessing the beam service, and selects the beam service with the maximum weight to complete the initial access; the weight calculation is as follows:

[0052]

[0053] Step 3, after the user completes the initial access to the beam service, the satellite performs channel allocation for all beam services according to the number of newly accessed users in each beam service during the access phase of the current time frame, specifically as follows:

[0054] (3-1) Model the channel allocation as a graph coloring problem in graph theory, and establish an undirected graph G=(V, E); where V is the set of nodes, that is, the set of beam services during the period of the current time frame; E is the set of edges; if there is an edge between two nodes, it indicates that there is an overlap between the two beam services.

[0055] (3-2) Assign weights to the nodes according to the number of users in the beam service, and use the Welsh-Powell algorithm based on node weights to determine the coloring of each node to achieve channel allocation; the formula for calculating the node weight β is as follows:

[0056]

[0057] where K is the number of beam services in the satellite, and M is the number of available channels for full-band reuse in the beam service.

[0058] The steps of the Welsh-Powell algorithm based on node weights are as follows:

[0059] (1) Determine the number of colors allocated in each round, that is, the number of channels in different frequency bands allocated within the beam service.

[0060] Specifically, the process of determining the number of colors allocated in the current round is as follows:

[0061] First, arrange the nodes of the current undirected graph in descending order of degree (the number of edges a node has); when the degrees of two nodes are the same, arbitrarily specify the order of these two nodes; denote the node numbers after sorting as i;

[0062] Second, determine a calculated value for each node according to the formula min{dig(v i ) + 1, i}; where dig(v i ) represents the degree of the i-th node;

[0063] Finally, select the largest calculated value from all the calculated values as the number of colors allocated in the current round.

[0064] (2) Start coloring the nodes in the order of descending node weights in the undirected graph, taking the node with the highest node weight as the first node, and sequentially traverse all nodes with non-zero node weights in the undirected graph; if the currently traversed node is not adjacent to all nodes with the same color as the first node, then color the currently traversed node with the same color as the first node; if adjacent, then use other colors to color the currently traversed node.

[0065] (3) Different colors in the undirected graph represent different allocated channels. After all nodes are traversed in one round, the node weights of all nodes are decreased by 1, and all nodes with node weight 0 are removed; the purpose of decreasing the node weight by 1 after one round of traversal is that if the node weight becomes 0 after the decrease, it indicates that the number of users accessing this node (beam service) is small and it will no longer participate in the channel allocation in the next round; while beam services with a larger number of accessing users will be allocated multiple channels in multiple rounds of allocation.

[0066] (4) Determine the number of colors allocated in the next round for all the remaining nodes according to the method in step (1), and perform the color allocation in the next round until all nodes are colored or all node weights are 0.

[0067] Step 4, the satellite sends the channel allocation result of each beam service to the users accessing it, and allocates corresponding communication time slots to the accessing users; when there are multiple channels allocated to a beam service, the satellite allocates channels and communication time slots to the users in the order of their access to this beam service.

[0068] Step 5, the users complete data transmission in the communication phase according to the channels corresponding to the beam services they access and the allocated time slots.

[0069] Example:

[0070] Step 1, as Figure 1The figure shows an example scenario diagram of the present invention. The system mainly consists of low-earth orbit satellites and aircraft. Among them, the low-earth orbit satellites are about 500 km above the ground. Each satellite is equipped with a communication payload and a phased array antenna. It is assumed that 10 sub-beams {A, B, C, … J} can be generated at the same time, and 10 sub-channels for services {a, b, c, … j} can be generated under each beam; aircraft as users {U1, U2, U3,...} can all directly transmit data with the help of satellites.

[0071] Step 2, Figure 2 It is the time frame stream and frame structure diagram of the satellite, including an access phase, a channel allocation phase, and a communication phase. In the access phase, users complete access by adopting the user beam selection strategy designed by the present invention. The specific steps are as Figure 3 shown:

[0072] (2-1) Taking {U1, U2, U3, U4} as an example, U1 and U4 have service satellites at this moment and execute step (2-2); while U2 does not have a service satellite at this moment, then U2 sends a confirmation message to the neighbor node U3. When U3 replies to U2 indicating that it has a service satellite, then U2 accesses the beam J where U3 is located;

[0073] (2-2) U4 is served by only one beam G at this moment, so the time slot in its communication phase remains unchanged, and it reports the old user identifier in the access phase and retains the communication time slot; U1 has two beams at this moment and executes step (2-3) according to the flow chart;

[0074] (2-3) U1 calculates the weight α according to the remaining service time of the satellite and the number of served users in the beam, as shown in the following formula:

[0075]

[0076] Assume that the moving direction of U1 is the same as that of the satellite, from D→E, then T D <T E , from Figure 1 it can be known that M D =M E , therefore, α D <α E , that is, U1 will access beam E; the selection strategies of other users are the same as those in the embodiment.

[0077] Step 3, after the access time slot ends, the satellite performs in-beam channel allocation according to the number of users, and the specific allocation strategy is as follows:

[0078] (3-1) Model the channel allocation of the satellite as a graph coloring problem, as Figure 4As shown in the figure, for the establishment of an undirected graph in the channel allocation phase, 10 beams are the node set V of the undirected graph G = (V, E), and the edge set E represents the overlap between two beams.

[0079] (3-2) Assign weights to the points according to the number of users in the beam, and use the Welsh-Powell algorithm based on point weights to determine the coloring of each node. The calculation of point weights is as follows:

[0080]

[0081] Table 1 Calculation of beam weights in the embodiment

[0082]

[0083] The steps of the Welsh-Powell algorithm based on point weights are as follows:

[0084] The first round of allocation:

[0085] (1) The following table shows the min{dig(v i ) + 1, i} calculated by arranging the nodes in descending order of degree in the embodiment, and then select the maximum value from the settlement results of all nodes as the number of colors allocated in this round; it can be determined that the number of channels allocated in the first round is 4.

[0086] Table 2 Number of channels allocated in the first round

[0087] Order 1 2 3 4 5 6 7 8 9 10 Point number E F A B C G D H I J Degree 4 4 3 3 3 3 2 2 2 2 <![CDATA[min{dig(v i )+1,i}]]> 1 2 3 4 4 4 3 3 3 3

[0088] (2) In this embodiment, {a, b, c,..., j} represents different colors (i.e., different channels). Starting from the point with the highest point weight in the graph, color the nodes in sequence, and traverse all the points with non-zero weights in the graph to ensure that adjacent nodes have different colors. The allocation result is as Figure 5 shown in (a).

[0089] (3) After all the nodes in the graph have completed one round of coloring, subtract 1 from the weight of each node;

[0090] Table 3 Weights of each beam after the first round

[0091]

[0092] (4) Repeat this algorithm for the remaining points with non-zero weights. End the algorithm when all the channels in the beam are allocated or the weights of all the beams in the satellite are zero. The allocation result is shown in Figure 5 shown in (b).

[0093] The second round of channel allocation:

[0094] The remaining nodes in this round are as Figure 5 shown in (b). According to the following table, it can be known that the number of channels allocated in the second round is 3;

[0095] Table 1 The number of channel allocations in the second round

[0096] Order 1 2 3 4 Point number E F I J Degree 2 2 2 0 <![CDATA[min{dig(v i )+1,i}]]> 1 2 3 1

[0097] Table 2 The beam weights after the second round ends

[0098]

[0099] After this round ends, the weights of each beam are all 0, and the channel allocation is completed.

[0100] Step 4: The satellite sends down the results of the channel allocation in Step 3 and allocates corresponding time slots to users.

[0101] Step 5: Users complete data transmission in the communication phase according to the corresponding channels and time slots.

[0102] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application, and should all be included in the protection scope of the present application.

Claims

1. A satellite communication access method, characterized in that: include: The user sends access signaling to the satellite during the satellite's time frame access phase and completes initial access based on the beam selection strategy; The time frame includes the access phase, the channel allocation phase and the communication phase; in the beam selection strategy, the user first determines whether there is a beam service, and when there is no beam service, the user uses the beam service of the neighboring node to achieve initial access, and when there is a beam service, there is no need to update the communication time slot, and when there are multiple beams, the weight of the beam service is calculated to determine which beam service is selected for initial access; The satellite allocates channels to all beam services according to the number of new users accessed by each beam service during the access phase of the current time frame. The channel allocation is modeled as a graph coloring problem, and the Welsh-Powell algorithm based on node weights is used to determine the coloring of each node to achieve channel allocation. The satellite sends the channel allocation result of each beam service to the users connected by the beam service, and allocates corresponding communication time slots to the connected users; The user completes data transmission during the communication phase according to the channel and allocated time slot corresponding to the accessed beam service.

2. The satellite communication access method according to claim 1, characterized in that: The user first determines whether it has a beam service, and if there is no beam service, uses the beam service of a neighboring node to achieve initial access, including: The user determines whether it has beam service; if not, the user sends a query message to the neighbor node in a broadcasting manner to determine whether it has beam service. The neighbor node that receives the query message sends a confirmation reply frame to the user; the user selects the neighbor node with beam service through the confirmation reply frame, and selects the neighbor node that replies to the confirmation reply frame first from these neighbor nodes, and sends an access short frame to the neighbor node to indicate joining the beam service of the neighbor node; If it is determined through the confirmation reply frame that all neighbor nodes have no beam service, the user and its neighbor nodes will form a cluster network, and the nodes in the cluster network will randomly select a channel and a time slot to send access signaling; if a node in the cluster successfully accesses a beam service, the entire cluster network will access the beam service.

3. The satellite communication access method according to claim 1, characterized in that: The method of not updating the communication time slot when there is a beam service includes: The user determines whether he has multiple beam services; if there is only one beam service, it means that this beam service is the same beam service as the user's beam service in the previous time frame, and the user selects this beam service to complete the initial access; for this beam service, the user is called an old user; the user reports the old user identifier to the satellite, and after the satellite obtains the old user identifier, when allocating communication time slots in the channel allocation phase of the current time frame, the communication time slot allocated to the user in the channel allocation phase of the previous time frame remains unchanged and continues to be allocated to the user.

4. The satellite communication access method according to claim 1, characterized in that: The step of determining which beam service to select for initial access by calculating the weight of the beam service when there are multiple beams includes: The user receives data in the access status frame sent by the satellite, including the remaining service time T of the beam service. i , the number of users currently accessing the beam service M i The weight α is calculated based on the signal, and the beam service with the largest weight is selected to complete the initial access; the weight is calculated as follows:

5. The satellite communication access method according to claim 1, characterized in that: The channel allocation is modeled as a graph theory coloring problem, specifically: Establish an undirected graph G = (V, E); where V is a set of nodes, using the periodic beam service of the current time frame as the node; E is a set of edges; if there is an edge between two nodes, it indicates that there is an overlap between the two beam services.

6. The satellite communication access method according to claim 1, characterized in that: The method of using the Welsh-Powell algorithm based on node weights to determine the coloring of each node so as to achieve channel allocation includes: (1) Determine the number of colors allocated in each round, that is, the number of channels in different frequency bands allocated within the beam service; (2) Start coloring the nodes in the undirected graph in descending order of node weights, starting with the node with the highest node weight as the first node, and sequentially traverse all nodes with non-zero node weights in the undirected graph; if the currently traversed node and all nodes with the same color as the first node are not adjacent, then color the currently traversed node with the same color as the first node; if they are adjacent, select other colors to color the currently traversed node; (3) Different colors in the undirected graph represent different allocated channels. After a round of traversal of all nodes is completed, the node weight of each node is reduced by 1, and all nodes with a node weight of 0 are removed; (4) All remaining nodes determine the number of colors to be assigned in the next round according to the method in step (1), and perform the next round of color assignment until all nodes have been colored or all node weights are 0.

7. The satellite communication access method according to claim 6, characterized in that: The calculation method of the node weight is: Among them, β is the node weight, K is the number of beam services in the satellite, and M is the number of available channels for full-band multiplexing in the beam service.

8. The satellite communication access method according to claim 6, characterized in that: The process of determining the number of colors assigned to the current round is: First, arrange the nodes of the current undirected graph in descending order of degree; when two nodes have the same degree, arbitrarily specify the order of the two nodes; the sorted node is numbered as i; Secondly, according to the formula min{dig(v i )+1,i} determines a calculated value for each node; where dig(v i ) represents the degree of the i-th node; Finally, the largest calculated value is selected from all the calculated values ​​as the color number assigned to the current round.

9. The satellite communication access method according to claim 1, characterized in that: When a beam service has multiple allocated channels, the satellite allocates channels and communication time slots to users in the order in which they access the beam service.

10. A computer-readable storage medium, wherein a computer program is stored in the medium; characterized in that: When the computer program is executed by a processor, the satellite communication access method according to any one of claims 1 to 9 is implemented.

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