A coverage extension and transmission scheduling method based on low-altitude assisted VDE-TER system
By introducing low-altitude relay and time-division multiple access technologies into the VDE-TER system, combined with the network flow method, the resource scheduling problem of the traditional VDE-TER system in near-shore communication networks has been solved, achieving efficient transmission scheduling and coverage expansion, and improving the quality of maritime communication.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- DALIAN MARITIME UNIVERSITY
- Filing Date
- 2026-05-06
- Publication Date
- 2026-06-19
AI Technical Summary
Traditional VDE-TER systems struggle to meet the maritime communication needs of densely packed vessels in nearshore waters, particularly due to low computational efficiency in resource scheduling and coverage expansion.
A near-shore downlink transmission network based on the low-altitude assisted VDE-TER system is constructed. The association relationship of ship users and the time-frequency resource allocation are selected by combining the time-division multiple access method and the network flow method. The problem is modeled as the minimum cost maximum flow problem and solved.
It improves maritime communication coverage, optimizes resource scheduling, achieves efficient transmission scheduling under multiple constraints, reduces computational complexity, and provides a feasible solution for large-scale maritime communication networks.
Smart Images
Figure CN122248537A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of wireless communication technology, and more particularly to a coverage extension and transmission scheduling method based on a low-altitude assisted VDE-TER system. Background Technology
[0002] With the increasing density of vessels and the more frequent maritime activities in nearshore waters, traditional VDE-TER systems are struggling to meet the rapidly growing demand for maritime communication. The complex and variable maritime environment, the scarcity of VHF resources, and many other issues pose unprecedented challenges to achieving safe and stable maritime communication. Deploying low-altitude relays at sea within the nearshore low-altitude range for relay-assisted communication can effectively improve the coverage of VDE-TER systems, ensure communication quality for nearshore vessels, and provide a feasible means to further achieve seamless, secure, and reliable maritime communication coverage.
[0003] Traditional optimization algorithms often suffer from low computational efficiency, making their application in densely distributed near-shore communication networks extremely difficult. Therefore, combining graph theory—especially network flow methods—with wireless communication to solve practical resource scheduling problems has become a crucial research direction for the future. In recent years, network flow methods have demonstrated excellent performance in handling large-scale network optimization problems and have been widely applied to resource scheduling and allocation in the field of wireless communication. As a core tool in operations research and graph theory, network flow methods can guarantee solutions in polynomial time and possess outstanding modeling capabilities, effectively handling complex multi-constraint problems. Therefore, applying network flow methods to near-shore communication networks to solve transmission scheduling problems is not only theoretically feasible but also has broad practical application prospects. Summary of the Invention
[0004] To address the aforementioned technical problems, this invention employs the following technical means: a coverage extension and transmission scheduling method based on a low-altitude assisted VDE-TER system, comprising the following steps:
[0005] Based on the VDE-TER system, a near-shore downlink transmission network with low-altitude relay assistance is constructed to realize two information transmission modes for near-shore ship information transmission systems: shore-based direct transmission and low-altitude relay transmission at sea. Based on the time division multiple access method, determine the time and frequency resource allocation mechanism between the VDE-TER system and ship users; Select the association relationships of ship users and determine the information transmission mode of the ship; Based on the ship's determined information transmission mode and the time-frequency resource allocation mechanism between the VDE-TER system and all ship users, the problem of solving the subchannel occupancy duration is modeled as the minimum cost maximum flow problem of time-frequency resource allocation in the near-shore ship information transmission system. Solve the minimum cost maximum flow problem for time-frequency resource allocation to maximize the total amount of data transmitted by all ships.
[0006] Furthermore, the time-frequency resource allocation mechanism for the VDE-TER system and ship users based on the time-division multiple access method is specifically determined as follows: Resource scheduling occurs at the beginning of each VDE-TER TDMA frame; Define ship users In sub-channel The time occupied is The duration of the service is determined by the service demand. All communication links do not reuse the same VHF channels and time slots; Each ship user can occupy multiple sub-channels for data transmission; For the same subchannel, the total time spent by all ship users on that subchannel cannot exceed one scheduling cycle. .
[0007] Furthermore, the specific process of selecting the association relationship of ship users and determining the information transmission mode of the ship is as follows: Define related variables Indicates ship user Whether to establish an association with a shore-based base station; if an association is established, then... ,otherwise Related variables Indicates ship user Is it related to low-altitude relay at sea? Establish a connection; if a connection is established, then... ,otherwise ; The binary constraints for ship user-related variables are then defined as follows:
[0008] The above binary constraints and Together, they form the overall constraint on ship user-related issues; If a ship user is directly connected to a shore-based base station, the transmission rate expression for that ship user in the shore-based direct connection transmission mode is defined as follows:
[0009] in, This indicates the received power of ship users in shore-based direct transmission mode; This represents the power of additive white Gaussian noise; If a ship user is associated with a maritime low-altitude relay, and the maritime low-altitude relay forwards signals using a decode-forward method, the maritime low-altitude relay transmission rate expression is defined as follows:
[0010] in, Indicates relay at low altitudes over the sea The received power; This indicates that the shore-based base station is a relay. When allocating power, in the case of ship users The received power at that location; , These represent the received power of the direct path and the reflected path of the air-sea channel, respectively; This represents the power of additive white Gaussian noise; The first term in the expression for low-altitude relay transmission rate at sea This is because the two stages of relay transmission occupy space separately. Half the duration; Due to the existence of the aforementioned binary constraints, the association relationship of ship users is unique. Under this condition, ship users will give priority to choosing access points with better signal quality for association. Related variables and Rewritten as ,in, ; This represents the transmission rate calculated given a fixed power allocation, which is used to solve the minimum cost maximum flow problem. This indicates that, given a fixed power allocation, the relationship between ship users and each access point is related to the transmission rate; The global constraint rewrite expression for the ship user association problem is defined as follows:
[0011] Under the constraint of association, the association between each ship user and each access point is determined by calculating and comparing the transmission rates between each ship user and each access point. Based on the transmission rate expressions for the two transmission modes mentioned above, the following definition is given for ship users under the shore-based direct connection transmission mode: The total amount of data transmitted across all sub-channels is expressed as follows:
[0012] in, Indicates ship user In sub-channel Duration of time occupied; Indicates the direct-connection transmission rate from shore; Define the low-altitude relay transmission mode at sea for ship users The total amount of data transmitted across all sub-channels is expressed as follows:
[0013] in, Indicates ship user In sub-channel Duration of time occupied; Indicates the low-altitude relay transmission rate at sea; Therefore, the total data transmission volume of the ship information transmission system is defined as follows: .
[0014] in, This indicates the total amount of data transmitted via direct shore-based connection. This indicates the total amount of data transmitted via maritime relay. Furthermore, based on the ship's determined information transmission mode and the time-frequency resource allocation mechanism between the VDE-TER system and all ship users, the process of modeling the subchannel occupancy duration problem as a minimum-cost maximum-flow problem of time-frequency resource allocation for near-shore ship information transmission systems is as follows: The problem of determining the duration of subchannel occupancy is defined as follows:
[0015] The objective function of the problem is to maximize the total amount of data transmitted by the ship information transmission system, where the C1 constraint means that the total time occupied by all ship users on each sub-channel cannot exceed one scheduling cycle. ; The problem of solving the aforementioned sub-channel occupancy duration is modeled as a minimum-cost maximum flow problem for time-frequency resource allocation; The graph structure of the minimum cost maximum flow problem for time-frequency resource allocation is a directed graph. It means that, among them, Represents a set of nodes. The set of nodes representing ship users, This represents the set of nodes in a sub-channel. Indicates the source node, Represents the destination node; the total number of nodes is [number missing]. The capacity range of the communication link is ; Define the source node and destination node The divergence of all nodes except those in the above order is 0, i.e. For the source node and destination node Then there is ; Define the communication link traffic in the minimum-cost maximum-flow problem of time-frequency resource allocation as:
[0016] in, This represents the edge flow between the source node and the ship user node; This represents the side traffic between the ship user node and the sub-channel node; This represents the side traffic between the sub-channel node and the destination node.
[0017] Furthermore, the communication link set The structure is as follows: Type 1 communication link: an edge connecting the source node and each ship user node. This represents a virtual link, and its unit traffic cost is... ; Type II communication link: The edge connecting each ship user node with each sub-channel node. This refers to shore-based direct transmission links or low-altitude relay transmission links at sea. Low-altitude relay transmission links at sea include air-to-shore backhaul links and air-to-sea access links. Assuming the ship user association and power allocation are determined, the unit traffic cost for this type of communication link is expressed as:
[0018] in, Indicates the transmission power The transmission rate calculated in time. With the Correspondingly; Type III communication link: an edge connecting each sub-channel node to the destination node. This represents a virtual link, and its unit traffic cost is... .
[0019] Furthermore: the expression for the minimum-cost maximum-flow problem of time-frequency resource allocation is:
[0020] Among them, the C1 constraint means that the edge flow should always be within the edge capacity range; Constraints C2 and C3 represent the flow conservation conditions for the ship user node and sub-channel node, respectively; constraints C4 and C5 represent the flow conservation conditions for the source node and destination node, respectively. The C6 constraint requires that the total flow out of the source node should be strictly equal to the total flow into the destination node, with the negative sign indicating the direction of flow.
[0021] This invention proposes a coverage extension and transmission scheduling method based on a low-altitude assisted VDE-TER system. It constructs a near-shore downlink transmission network with low-altitude relay assistance, introduces a relay transmission mode to extend the coverage of shore-based base stations, and proposes a time-frequency resource allocation mechanism based on time-division multiple access (TDMA) technology. Finally, the association relationships between ship users are determined, and the time-frequency resource allocation results are obtained using the proposed minimum-cost maximum flow algorithm. Compared to traditional optimization algorithms, the proposed method has lower computational complexity, providing a valuable reference for the coverage extension and transmission scheduling of subsequent large-scale maritime communication networks.
[0022] To address this, this invention proposes a coverage extension and transmission scheduling method based on a low-altitude assisted VDE-TER system. The aim is to leverage the dynamic adaptability of network flow methods to maximize the amount of data transmitted by optimizing the allocation of time-frequency resources to ship users. Attached Figure Description
[0023] 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 some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0024] Figure 1 This is a flowchart of the method of the present invention.
[0025] Figure 2 This is a scenario diagram used in an embodiment of the present invention.
[0026] Figure 3 This is a schematic diagram of the time-frequency resource allocation mechanism of the VDE-TER system provided in an embodiment of the present invention.
[0027] Figure 4 A network flow model diagram for time-frequency resource allocation provided in an embodiment of the present invention.
[0028] Figure 5 This is a schematic diagram of the ship user relationship provided in an embodiment of the present invention.
[0029] Figure 6 A bar chart showing the amount of data transmitted by ship users served by shore-based base stations, provided in an embodiment of the present invention.
[0030] Figure 7 A bar chart showing the amount of data transmitted by ship users via relay services, provided for an embodiment of the present invention.
[0031] Figure 8 This is a graph showing the relationship between the amount of data transmitted by the system and the number of ship users at different relay altitudes, as provided in this embodiment of the invention. Detailed Implementation
[0032] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.
[0033] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.
[0034] Figure 1 This is a flowchart of the method of the present invention.
[0035] like Figure 1 As shown, this embodiment of the invention provides a coverage extension and transmission scheduling method based on a low-altitude assisted VDE-TER system, including the following steps: S1. Based on the VDE-TER system, construct a near-shore downlink transmission network with low-altitude relay assistance at sea, so as to realize two information transmission modes for near-shore ship information transmission system: shore-based direct transmission and low-altitude relay transmission at sea. S2. Based on the time division multiple access method, determine the time and frequency resource allocation mechanism between the VDE-TER system and ship users; S3. Select the association relationships of ship users and determine the information transmission mode of the ship; S4. Based on the information transmission mode determined by the ship and the time-frequency resource allocation mechanism between the VDE-TER system and all ship users, the problem of solving the sub-channel occupancy duration is modeled as the minimum cost maximum flow problem of time-frequency resource allocation in the near-shore ship information transmission system. S5. Solve the minimum cost maximum flow problem for time and frequency resource allocation to maximize the total amount of data transmitted by all ships.
[0036] Steps S1 / S2 / S3 / S4 / S5 are executed sequentially; Figure 2 This is a scene diagram used in an embodiment of the present invention; Furthermore, a near-shore downlink transmission network with low-altitude relay assistance will be constructed, the specific contents of which are as follows: Consider a A low-altitude relay at sea, A near-shore downlink transmission network consisting of one ship user and one shore-based base station is established. Each maritime low-altitude relay is deployed in the near-shore low-altitude area, employing a decode-forward relay transmission protocol to extend the coverage of the shore-based base station. The set of maritime low-altitude relays is defined as follows: The ship user group is Ship users can transmit data via shore-based direct transmission or low-altitude relay transmission at sea. Shore-based direct transmission includes shore-sea access links; low-altitude relay transmission at sea includes air-shore return links and air-sea access links.
[0037] Figure 3 A time-frequency resource allocation mechanism diagram of the VDE-TER system provided in this embodiment of the invention; like Figure 3 As shown, the time-frequency resource allocation mechanism of the VDE-TER system is as follows: (1) Resource scheduling is performed at the beginning of each VDE-TER TDMA frame; (2) Define the sub-channel occupancy time for ship users The specific size is determined by service requirements; (3) All communication links do not reuse the same VHF channels and time slots; (4) Each ship user can occupy multiple sub-channels for data transmission.
[0038] (5) For the same subchannel, the total time occupied by all ship users on that subchannel shall not exceed one scheduling cycle. .
[0039] Furthermore, ship users need to select the best signal quality, determine the ship user association relationships, and the specific process for determining the ship's information transmission mode is as follows: Define related variables This indicates whether the ship user has established an association with the shore-based base station. If an association has been established, then... ,otherwise Related variables This indicates whether the ship user has established a connection with a low-altitude maritime relay. If a connection has been established, then... ,otherwise ; The binary constraints for ship user-related variables are then defined as follows:
[0040] The binary constraint and Together, they form the overall constraint on issues related to ship users.
[0041] If a ship user is directly connected to a shore-based base station, the transmission rate expression for that ship user in the shore-based direct connection transmission mode is defined as follows:
[0042] in, This indicates the received power of ship users in shore-based direct transmission mode; This represents the power of additive white Gaussian noise.
[0043] If a ship user is associated with a maritime low-altitude relay, and the maritime low-altitude relay forwards signals using a decode-forward method, the maritime low-altitude relay transmission rate expression is defined as follows:
[0044] in, Indicates the low-altitude relay receiving power at sea; This indicates the received power at the ship user's location when the shore-based base station allocates power; , These represent the received power of the direct path and the reflected path of the air-sea channel, respectively; This represents the power of additive white Gaussian noise.
[0045] The first term in the expression for the low-altitude relay transmission rate at sea This is because the two stages of relay transmission occupy space separately. Half the duration.
[0046] Due to the aforementioned binary constraints, the association relationships between ship users are unique, and ship users will preferentially choose access points with better signal quality for association. For simplification and ease of solution, the association variables are... and Rewritten as ,in, ; This represents the transmission rate calculated given a fixed power allocation, which is used to solve the minimum cost maximum flow problem. This indicates that, given a fixed power allocation, the relationship between ship users and each access point is related to the transmission rate.
[0047] The global constraint rewrite expression for the ship user association problem is defined as follows:
[0048] Under the constraint of association, the one-to-one association between ship users and access points can be determined by calculating and comparing the transmission rates between each ship user and each access point.
[0049] Figure 4 A network flow model diagram for time-frequency resource allocation provided in an embodiment of the present invention; Furthermore, Based on the transmission rate expressions for the two transmission modes mentioned above, the following definition is given for ship users under the shore-based direct connection transmission mode: The total amount of data transmitted across all sub-channels is expressed as follows:
[0050] in, Indicates ship user In sub-channel Duration of time occupied; Indicates the direct-connection transmission rate from shore; Define the low-altitude relay transmission mode at sea for ship users The total amount of data transmitted across all sub-channels is expressed as follows:
[0051] in, Indicates ship user In sub-channel Duration of time occupied; Indicates the low-altitude relay transmission rate at sea; Therefore, the total data transmission volume of the ship information transmission system is defined as follows: .
[0052] in, This indicates the total amount of data transmitted via direct shore-based connection. This indicates the total amount of data transmitted via maritime relay.
[0053] The process of modeling the subchannel occupancy duration problem as a minimum-cost maximum-flow problem for time-frequency resource allocation in a near-shore ship information transmission system, based on the ship-determined information transmission mode and the time-frequency resource allocation mechanism between the VDE-TER system and all ship users, is as follows: The problem of determining the duration of subchannel occupancy is defined as follows:
[0054] The objective function of the problem is to maximize the total amount of data transmitted by the ship information transmission system, where the C1 constraint means that the total time occupied by all ship users on each sub-channel cannot exceed one scheduling cycle. ; The objective function of the problem is to maximize the total amount of data transmitted by the system, where, The constraint states that the total duration of all ship users' usage on each subchannel cannot exceed one scheduling cycle. .
[0055] The problem of determining the duration of sub-channel occupancy is modeled as a minimum-cost maximum flow problem in time-frequency resource allocation. The graph structure of the minimum-cost maximum flow problem in time-frequency resource allocation is a directed graph. It means that, among them, Represents a set of nodes. The set of nodes representing ship users, This represents the set of nodes in a sub-channel. Indicates the source node, This represents the destination node. The total number of nodes in the graph is... Each edge in the diagram represents a communication link, with a capacity range of [missing information]. Communication link set The detailed structure is shown below: (1) Type I communication link: the edge connecting the source node and each ship user node This represents a virtual link, and its unit traffic cost is... ; (2) Second type of communication link: the edge connecting each ship user node and each sub-channel node This refers to shore-based direct transmission links or low-altitude relay transmission links at sea. Low-altitude relay transmission links at sea include air-to-shore backhaul links and air-to-sea access links. Given that ship user association and power allocation are determined, the unit traffic cost of this type of communication link can be expressed as:
[0056] in, Indicates the transmission power The transmission rate calculated in time. As mentioned above Correspondingly; (3) Third type of communication link: the edge connecting each sub-channel node and the destination node This represents a virtual link, and its unit traffic cost is... .
[0057] Define the source node and destination node The divergence of all nodes except those in the above order is 0, i.e. For the source node and destination node Then there is ; Define the edge flow in the network flow model graph as:
[0058] in, This represents the edge flow between the source node and the ship user node; This represents the side traffic between the ship user node and the sub-channel node; This represents the side traffic between the sub-channel node and the destination node; The minimum-cost maximum-flow problem for time-frequency resource allocation is defined as follows:
[0059] Among them, constraint C1 means that the edge flow should always be within the edge capacity range; constraints C2 and C3 represent the flow conservation conditions for ship user nodes and sub-channel nodes, respectively; constraints C4 and C5 represent the flow conservation conditions for source nodes and destination nodes, respectively; constraint C6 requires that the total flow out of the source node should be strictly equal to the total flow into the destination node, and the negative sign indicates the flow direction.
[0060] Simulation conditions In simulation scenario 1, ship users are randomly distributed within a rectangular area with a horizontal distance of 0-200km and a vertical width of 0-10km. Relays are also randomly distributed within the same rectangular area, with a fixed relay height of 300m. The shore-based base station's location coordinates are fixed at (0, 5000), and its sea surface height is 2m. The transmit power of both the shore-based base station and the relays is fixed at 10W. There are 3 relays, 40 ship users, and 40 sub-channels. The total duration of all sub-channels is 40s, the channel bandwidth is 25kHz, and the noise power is... W. The gain of the shore-based antenna, the shipboard antenna, and the relay antenna are all 10 dBi.
[0061] In simulation scenario 2, the parameter settings are the same as in simulation scenario 1.
[0062] In simulation scenario 3, ship users are randomly distributed within a rectangular area with a horizontal distance of 100-200 km and a vertical width of 10 km, while relays are randomly distributed within a rectangular area with a horizontal distance of 50-150 km and a vertical width of 10 km. The relay heights are 100m, 300m, and 500m, and the number of ship users is 50, 150, 250, 350, and 450, respectively. Unless otherwise specified, other parameter settings are consistent with simulation scenario 1.
[0063] Simulation content and result analysis Simulation 1: Ship users select the best signal quality and prioritize the access point with the highest transmission rate for association.
[0064] like Figure 5As shown, the 17 ship users closest to the shore-based base station preferentially choose to associate with the shore-based base station for direct transmission, at which point the signal quality is the best, which is consistent with the actual VDE-TER near-shore transmission situation; the remaining 23 ship users choose to associate with relays for relay transmission, extending the coverage of the shore-based base station. Relay 1, which is closest to the shore-based base station, is in an idle state and does not associate with ship users. This satisfies the association constraint condition, that is, each ship user is associated with only one access point.
[0065] Simulation 2: After ship users select the access point with the best signal quality for association, under the premise of fixed transmit power, the time-frequency resource allocation algorithm based on minimum cost and maximum flow proposed in this invention is used to solve for the occupancy time of each ship user on each sub-channel, thus completing the resource allocation. For example... Figure 6 As shown, this illustrates the amount of data transmitted by ship users operating in shore-based direct transmission mode; for example... Figure 7 As shown, this illustrates the amount of data transmitted by ship users in low-altitude relay transmission mode at sea. In this mode, relay 1 is idle, while relay 2 supports data transmission for most ship users.
[0066] Simulation 3: After ship users select the access point with the best signal quality for association, under the premise of fixed transmit power, the time-frequency resource allocation algorithm based on minimum cost and maximum flow proposed in this invention is used to solve for the occupancy time of each ship user on each sub-channel, thus completing the resource allocation. For example... Figure 8 As shown, the impact of relay altitude on the system's data transmission volume is illustrated. At each relay altitude, the system's data transmission volume exhibits an increasing trend with the increase in the number of ship users. This simulation result further demonstrates the importance of balancing relay altitude for improving the system's data transmission volume, providing a reference for subsequent research on relay deployment optimization.
[0067] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.
Claims
1. A method for coverage extension and transmission scheduling based on a low-altitude assisted VDE-TER system, characterized in that, Includes the following steps: Based on the VDE-TER system, a near-shore downlink transmission network with low-altitude relay assistance is constructed to realize two information transmission modes for near-shore ship information transmission systems: shore-based direct transmission and low-altitude relay transmission at sea. Based on the time division multiple access method, determine the time and frequency resource allocation mechanism between the VDE-TER system and ship users; Select the association relationships of ship users and determine the information transmission mode of the ship; Based on the ship's determined information transmission mode and the time-frequency resource allocation mechanism between the VDE-TER system and all ship users, the problem of solving the subchannel occupancy duration is modeled as the minimum cost maximum flow problem of time-frequency resource allocation in the near-shore ship information transmission system. Solve the minimum cost maximum flow problem for time-frequency resource allocation to maximize the total amount of data transmitted by all ships.
2. The shore-based coverage and transmission scheduling method based on a low-altitude assisted VDE-TER system according to claim 1, characterized in that, The time-frequency resource allocation mechanism for the VDE-TER system and ship users, based on the time-division multiple access method, is determined as follows: Resource scheduling occurs at the beginning of each VDE-TER TDMA frame; Define ship users In sub-channel The time occupied is The duration of the service is determined by the service demand. All communication links do not reuse the same VHF channels and time slots; Each ship user can occupy multiple sub-channels for data transmission; For the same subchannel, the total time spent by all ship users on that subchannel cannot exceed one scheduling cycle. .
3. The coverage extension and transmission scheduling method based on a low-altitude assisted VDE-TER system according to claim 1, characterized in that, The specific process of selecting the association relationship of ship users and determining the information transmission mode of the ship is as follows: Define related variables Indicates ship user Whether to establish an association with a shore-based base station; if an association is established, then... ,otherwise ; Related variables Indicates ship user Is it related to low-altitude relay at sea? Establish a connection; if a connection is established, then... ,otherwise ; The binary constraints for ship user-related variables are then defined as follows: The above binary constraints and Together, they form the overall constraint on ship user-related issues; If a ship user is directly connected to a shore-based base station, the transmission rate expression for that ship user in the shore-based direct connection transmission mode is defined as follows: in, This indicates the received power of ship users in shore-based direct transmission mode; This represents the power of additive white Gaussian noise; If a ship user is associated with a maritime low-altitude relay, and the maritime low-altitude relay forwards signals using a decode-forward method, the maritime low-altitude relay transmission rate expression is defined as follows: in, Indicates relay at low altitudes over the sea The received power; This indicates that the shore-based base station is a relay. When allocating power, in the case of ship users The received power at that location; , These represent the received power of the direct path and the reflected path of the air-sea channel, respectively; This represents the power of additive white Gaussian noise; The first term in the expression for low-altitude relay transmission rate at sea This is because the two stages of relay transmission occupy space separately. Half the duration; Due to the existence of the aforementioned binary constraints, the association relationship of ship users is unique. Under this condition, ship users will give priority to choosing access points with better signal quality for association. Related variables and Rewritten as ,in, ; This represents the transmission rate calculated given a fixed power allocation, which is used to solve the minimum cost maximum flow problem. This indicates that, given a fixed power allocation, the relationship between ship users and each access point is related to the transmission rate; The global constraint rewrite expression for the ship user association problem is defined as follows: Under the constraint of association, the association between each ship user and each access point is determined by calculating and comparing the transmission rates between each ship user and each access point. Based on the transmission rate expressions for the two transmission modes mentioned above, the following definition is given for ship users under the shore-based direct connection transmission mode: The total amount of data transmitted across all sub-channels is expressed as follows: in, Indicates ship user In sub-channel Duration of time occupied; Indicates the direct-connection transmission rate from shore; Define the low-altitude relay transmission mode at sea for ship users The total amount of data transmitted across all sub-channels is expressed as follows: in, Indicates ship user In sub-channel Duration of time occupied; Indicates the low-altitude relay transmission rate at sea; Therefore, the total data transmission volume of the ship information transmission system is defined as follows: in, This indicates the total amount of data transmitted via direct shore-based connection. This indicates the total amount of data transmitted via maritime relay.
4. The coverage extension and transmission scheduling method based on a low-altitude assisted VDE-TER system according to claim 1, characterized in that, The process of modeling the subchannel occupancy duration problem as a minimum-cost maximum-flow problem for time-frequency resource allocation in a near-shore ship information transmission system, based on the ship-determined information transmission mode and the time-frequency resource allocation mechanism between the VDE-TER system and all ship users, is as follows: The problem of determining the duration of subchannel occupancy is defined as follows: The objective function of the problem is to maximize the total amount of data transmitted by the ship information transmission system, where the C1 constraint means that the total time occupied by all ship users on each sub-channel cannot exceed one scheduling cycle. ; The problem of solving the aforementioned sub-channel occupancy duration is modeled as a minimum-cost maximum flow problem for time-frequency resource allocation; The graph structure of the minimum cost maximum flow problem for time-frequency resource allocation is a directed graph. It means that, among them, Represents a set of nodes. The set of nodes representing ship users, This represents the set of nodes in a sub-channel. Indicates the source node, Represents the destination node; the total number of nodes is [number missing]. The capacity range of the communication link is ; Define the source node and destination node The divergence of all nodes except those in the above order is 0, i.e. For the source node and destination node Then there is ; Define the communication link traffic in the minimum-cost maximum-flow problem of time-frequency resource allocation as: in, This represents the edge flow between the source node and the ship user node; This represents the side traffic between the ship user node and the sub-channel node; This represents the side traffic between the sub-channel node and the destination node.
5. A coverage extension and transmission scheduling method based on a low-altitude assisted VDE-TER system according to claim 4, characterized in that, The communication link set The structure is as follows: Type 1 communication link: an edge connecting the source node and each ship user node. This represents a virtual link, and its unit traffic cost is... ; Type II communication link: The edge connecting each ship user node with each sub-channel node. This refers to shore-based direct transmission links or low-altitude relay transmission links at sea. Low-altitude relay transmission links at sea include air-to-shore backhaul links and air-to-sea access links. Assuming the ship user association and power allocation are determined, the unit traffic cost for this type of communication link is expressed as: in, Indicates the transmission power The transmission rate calculated in time. With the Correspondingly; Type III communication link: an edge connecting each sub-channel node to the destination node. This represents a virtual link, and its unit traffic cost is... .
6. The coverage extension and transmission scheduling method based on a low-altitude assisted VDE-TER system according to claim 1, characterized in that: The expression for the minimum-cost maximum-flow problem of time-frequency resource allocation is: Among them, the C1 constraint means that the edge flow should always be within the edge capacity range; Constraints C2 and C3 represent the flow conservation conditions for the ship user node and sub-channel node, respectively; constraints C4 and C5 represent the flow conservation conditions for the source node and destination node, respectively. The C6 constraint requires that the total flow out of the source node should be strictly equal to the total flow into the destination node, with the negative sign indicating the direction of flow.