A differentiated interest and access mode under the star-satellite collaborative network content caching method

Abstract

This invention provides a content caching method for satellite-ground cooperative networks under differentiated interest and access modes. The method includes collecting user proportion information, content popularity distribution information, cache capacity information, and link latency information in the satellite-ground cooperative network; determining a latency-optimized base station and satellite cooperative content caching problem based on differentiated user interests and access modes; solving the content caching problem to obtain a base station and satellite cooperative content caching strategy; and caching content on both the base station and satellite based on the obtained strategy, providing content services to base station access users and satellite access users in the network. This method can simultaneously reduce the content service latency for both base station access users and satellite access users under differentiated user interest distributions, alleviate the problem of long communication latency caused by long transmission distances in satellite-ground links, improve user experience, and support various latency-sensitive services.

Description

Technical Field

[0001] This invention relates to the technical field of resource allocation in wireless communication, and in particular to a content caching method for satellite-ground cooperative networks under differentiated interest and access modes. Background Technology

[0002] With the development of smart devices and multimedia technologies, mobile data traffic is increasing daily in modern society. Due to economic costs and geographical limitations, the construction of traditional terrestrial communication networks in remote areas remains at a low level, and it is also difficult to cover environments such as sea and airspace. Space-terrestrial collaborative networks can compensate for the shortcomings of traditional terrestrial communication networks, providing globally covered communication services at a lower cost, and represent an important development direction for next-generation communication networks. However, due to the long transmission distance of space-terrestrial links, users will experience significant communication latency when requesting content services from the cloud via satellite, resulting in a degraded user experience and difficulty in supporting various latency-sensitive services.

[0003] Edge storage technology has garnered significant attention for reducing content service latency in communication networks. Since multimedia content is often highly repetitive, caching frequently requested content at network edge nodes avoids repeated retrieval from the cloud, thus reducing content service latency. Applying edge storage technology to satellite-ground collaborative networks can provide users across a wide area with lower latency mobile high-definition video, virtual reality, and augmented reality applications. It can also provide edge data storage and intelligent analysis for various IoT devices, such as health monitoring and surveillance sensors. Considering cache size limitations, edge node caching strategies typically need to be designed based on user interest distribution to improve cache hit rate and minimize service latency when users request content.

[0004] In a space-ground cooperative communication system, potential caching locations include base stations, satellites, and ground stations. Since both base stations and satellites can provide access services to users, different content service paths will be constructed for users with different access modes. Furthermore, due to the wide coverage of satellites, the distribution of users' interests in the same content will differ across different areas. Current content caching methods for space-ground cooperative networks typically only consider a single base station access user or a single satellite access user, and usually only consider a global interest model. Effective methods are still lacking for content caching problems under differentiated interests and access modes. To fully exploit the performance of space-ground cooperative network systems, it is necessary to design content caching strategies tailored to the characteristics of differentiated interests and access modes, and optimize user content service latency. Summary of the Invention

[0005] The purpose of this invention is to provide a content caching method for satellite-ground cooperative networks under differentiated interest and access modes. This method can simultaneously reduce the content service latency for both base station access users and satellite access users under differentiated user interest distributions, alleviate the problem of long communication latency caused by long transmission distances of satellite-ground links, improve user experience, and support various latency-sensitive services.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for caching content in a satellite-ground cooperative network under differentiated interest and access modes includes the following steps:

[0008] (1) Collect user ratio information, content popularity distribution information, cache capacity information, and link latency information in the satellite-ground collaborative network; the satellite-ground collaborative network consists of base stations, satellites, base station access users, satellite access users, ground stations, and cloud servers; the coverage area of ​​the satellite-ground collaborative network is divided into multiple regions, and different regions have different local content popularity distributions;

[0009] (2) Based on differentiated user interests and differentiated access modes, determine the base station and satellite collaborative content caching problem for latency optimization; the latency optimization refers to minimizing the average content retrieval latency for all users in the satellite-ground collaborative network;

[0010] (3) Solve the content caching problem to obtain a base station and satellite collaborative content caching strategy;

[0011] (3.1) The average content retrieval delay of satellite access users in different regions is equivalently transformed into the average content retrieval delay of all satellite access users under the global content popularity distribution, thereby reducing the computational complexity of the average content retrieval delay of satellite access users.

[0012] (3.2) Based on solution space analysis, reduce the size of the solution space and reduce the search complexity of the content caching strategy;

[0013] (3.3) The content caching problem is transformed into a latency reduction gain maximization problem; the latency reduction gain refers to the reduction in average user content retrieval latency under the current content caching strategy compared to when the base station and satellite do not cache any content;

[0014] (3.4) Solve the problem of maximizing the gain of delay reduction after conversion to obtain the base station and satellite collaborative content caching strategy;

[0015] (4) Based on the obtained content caching strategy, the content is cached at base stations and satellites to provide content services for base station access users and satellite access users in the network.

[0016] Furthermore, in step (1), there is a communication link between the base station and the base station access users within the coverage area, a communication link between the satellite and the base station and satellite access users within the coverage area, a communication link between the ground station and the satellite, and a communication link between the cloud server and the ground station; the base station, satellite, and ground station cache some content that users may request, and the cloud server stores all content that users may request; the base station can transmit the cached content to the base station access users within the coverage area, the satellite can transmit the cached content to the base station and satellite access users within the coverage area, the ground station can transmit the cached content to the satellite, and the cloud server can transmit the cloud-stored content to the ground station.

[0017] Furthermore, the user ratio information in step (1) refers to the ratio of base station access users and satellite access users in the satellite-ground cooperative network, as well as the ratio of users in different areas covered by the satellite-ground cooperative network.

[0018] The content popularity distribution information refers to the local content popularity distribution information in different regions covered by the satellite-ground collaborative network;

[0019] The cache capacity information includes base station cache capacity information and satellite cache capacity information;

[0020] The link delay information includes link delay information from base station to base station access user, link delay information from satellite to base station, link delay information from satellite to satellite access user, link delay information from ground station to satellite, and link delay information from cloud server to ground station.

[0021] Further, step (2) includes the following sub-steps:

[0022] (2.1) For each area covered by the satellite-ground cooperative network, based on the local content popularity distribution in that area, calculate the content storage probability of the content in the base station, satellite, ground station, and cloud server when a user requests any content through the base station in that area.

[0023] For each area covered by the satellite-ground collaborative network, based on the local content popularity distribution in that area, the probability of content being stored on the satellite, ground station, and cloud server when a satellite access user in that area requests any content is calculated.

[0024] (2.2) For each area covered by the satellite-ground cooperative network, based on the content storage probability and link delay information, calculate the average content retrieval delay for base station access users and the average content retrieval delay for satellite access users respectively;

[0025] (2.3) The average content retrieval delay of all users in all areas within the coverage of the satellite-ground collaborative network is weighted and summed to obtain the average content retrieval delay of the network.

[0026] (2.4) The content caching problem is obtained by taking the base station and satellite collaborative content caching strategy as the optimization variable, minimizing the average network content retrieval latency as the optimization objective, and the base station and satellite cache capacity as the optimization constraint.

[0027] Furthermore, the sub-step (3.2) includes the following process:

[0028] (3.2.1) For each region, the fixed cache content and the selected cache content of the base station in that region are calculated based on the local content popularity distribution information, cache capacity information and link delay information of that region; the fixed cache content refers to the content that must be cached in the content caching strategy obtained by solving the content caching problem, and the selected cache content refers to the content that may be cached in the content caching strategy obtained by solving the content caching problem.

[0029] In addition, satellite fixed cache content and selected cache content are calculated based on user ratio information, global content popularity distribution information, and cache capacity information.

[0030] (3.2.2) For each region, the solution space of the base station content caching strategy in that region is reduced to the union of the fixed cached content and the selected cached content of the base station in that region, and the search space of the base station content caching strategy in that region is reduced to the set of the selected cached content of the base station in that region.

[0031] In addition, the solution space of the satellite content caching strategy is reduced to the union of the fixed cached content and the selected cached content of the satellite, and the search space of the satellite content caching strategy is reduced to the set of the selected cached content of the satellite.

[0032] Furthermore, step (3.4) specifically includes the following iterative process:

[0033] (3.4.1) Initialize the satellite iterative solution as a fixed set of satellite cache contents;

[0034] (3.4.2) Initialize all content in the satellite selection cache content set to an unselected state;

[0035] (3.4.3) Select an unselected content from the satellite selection cache content set, and update the satellite candidate solution corresponding to the content to the union of the satellite iterative solution and the selected content;

[0036] (3.4.4) For each region, calculate the content caching strategy when the base station in that region achieves the maximum latency reduction gain under the satellite candidate solution corresponding to the selected content;

[0037] (3.4.5) Based on the satellite candidate solutions corresponding to the selected content and the calculated base station content caching strategy, calculate the corresponding latency reduction gain;

[0038] (3.4.6) Determine whether there is any unselected content in the satellite selection cache content set; if so, return to (3.4.3); if not, compare the satellite candidate solutions corresponding to all content in the satellite selection content set, and update the satellite iterative solution to the satellite candidate solution with the largest delay reduction gain;

[0039] (3.4.7) If there is no unselected content in the satellite's selected cache content set, continue to determine whether the satellite's iterative solution has reached the upper limit of the satellite cache capacity; if it has not reached the upper limit, return to (3.4.2); if it has reached the upper limit, the iteration ends.

[0040] (3.4.8) The satellite content caching strategy obtained by solving is the satellite iterative solution; for each region, the base station content caching strategy obtained by solving is the base station content caching strategy calculated in (3.4.4) corresponding to the satellite iterative solution.

[0041] Furthermore, step (3.4.4) specifically includes the following process:

[0042] (3.4.4.1) For each region, initialize the base station content caching strategy for that region to a fixed set of base station cache content for that region;

[0043] (3.4.4.2) For each region, select each content in the cache content set for the base station in that region, and calculate the reduction in latency for users accessing the base station in that region to retrieve the content when the satellite content caching strategy is a given satellite candidate solution, compared to not caching the content.

[0044] (3.4.4.3) For each region, select all content in the cache content set of the base station in that region, sort the calculated delay reduction, and add the content with the largest delay reduction to the cache of the base station in that region until the number of cached content in the base station in that region reaches the upper limit of the base station cache capacity.

[0045] An electronic device, comprising:

[0046] One or more processors;

[0047] A storage device for storing one or more programs, which, when executed by the electronic device, enable the electronic device to implement the satellite-ground cooperative network content caching method under the differentiated interest and access mode.

[0048] A computer-readable storage medium having a program stored thereon, which, when executed by a processor, implements the aforementioned method for caching content in a satellite-ground cooperative network under differentiated interest and access modes.

[0049] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0050] The present invention provides a content caching method for satellite-ground cooperative networks under differentiated interest and access modes. First, it collects user proportion information, content popularity distribution information, cache capacity information, and link latency information in the satellite-ground cooperative network. Then, based on differentiated user interests and differentiated access modes, it determines a latency-optimized base station and satellite cooperative content caching problem, solves the content caching problem, and obtains a base station and satellite cooperative content caching strategy. Finally, based on the obtained content caching strategy, it caches content on both the base station and satellite, providing content services to base station access users and satellite access users in the network, thereby optimizing the content service capabilities of the satellite-ground cooperative network. This method can simultaneously reduce the content service latency for both base station access users and satellite access users under differentiated user interest distributions, alleviate the problem of long communication latency caused by long transmission distances in satellite-ground links, improve user experience, and support various latency-sensitive services. Attached Figure Description

[0051] Figure 1 This is a flowchart illustrating a method for caching content in a satellite-ground collaborative network under a differentiated interest and access mode, as provided in an embodiment of the present invention.

[0052] Figure 2 This is a schematic diagram of a satellite-ground collaborative network provided in an embodiment of the present invention.

[0053] Figure 3 This is a flowchart for collecting user ratio information, content popularity distribution information, cache capacity information, and link latency information in a satellite-ground cooperative network, as provided in an embodiment of the present invention.

[0054] Figure 4 This is a flowchart illustrating how to determine the base station and satellite collaborative content caching problem for latency optimization based on differentiated user interests and differentiated access modes, as provided in this invention example.

[0055] Figure 5 The flowchart of the content caching strategy for base station and satellite collaboration is provided for solving the content caching problem in the embodiments of the present invention.

[0056] Figure 6 This is a flowchart illustrating how solution space analysis reduces the size of the solution space and lowers the search complexity of content caching strategies, as provided in embodiments of the present invention.

[0057] Figure 7The flowchart of the base station and satellite collaborative content caching strategy is obtained by solving the problem of maximizing the gain of latency reduction after conversion, as provided in the embodiments of the present invention.

[0058] Figure 8 This is a flowchart illustrating the content caching strategy for each region, calculated under the satellite candidate solution corresponding to the selected content, to achieve the maximum latency reduction gain for the base station in that region, as provided in this embodiment of the invention.

[0059] Figure 9 This diagram illustrates the performance comparison of the satellite-ground collaborative network content caching method under differentiated interest and access modes provided in this embodiment of the invention. Detailed Implementation

[0060] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. However, it should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and technologies are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0061] Existing content caching methods for satellite-ground cooperative networks typically only consider a single base station access user or a single satellite access user, and usually only consider a global interest model. Their performance is poor for content caching problems in scenarios with differentiated interests and access modes. Compared with existing content caching methods, the satellite-ground cooperative network content caching method under differentiated interest and access modes in this embodiment of the invention first collects user proportion information, content popularity distribution information, cache capacity information, and link latency information in the satellite-ground cooperative network. Then, based on differentiated user interests and differentiated access modes, it determines a latency-optimized base station and satellite cooperative content caching problem, solves the content caching problem, and obtains a base station and satellite cooperative content caching strategy. Finally, based on the obtained content caching strategy, the content is cached on the base station and satellite, providing content services to base station access users and satellite access users in the network, thereby optimizing the content service capabilities of the satellite-ground cooperative network. The specific process is as follows: Figure 1 As shown, this method can simultaneously reduce content service latency for both base station access users and satellite access users under differentiated user interest distributions, alleviate the problem of long communication latency caused by long transmission distances of satellite-to-ground links, improve user experience, and support various latency-sensitive services.

[0062] The above provides a brief overview of the content caching method for satellite-ground collaborative networks under differentiated interest and access modes. The following section provides a detailed description of the specific content involved.

[0063] S100 collects user ratio information, content popularity distribution information, cache capacity information, and link latency information in the satellite-ground collaborative network.

[0064] In one alternative implementation, reference Figure 2 The space-ground collaborative network includes:

[0065] The satellite-ground collaborative network consists of base stations, satellites, base station access users, satellite access users, ground stations, and cloud servers;

[0066] There is a communication link between the base station and the base station access users within its coverage area; there is a communication link between the satellite and the base station and satellite access users within its coverage area; there is a communication link between the ground station and the satellite; and there is a communication link between the cloud server and the ground station.

[0067] Base stations, satellites, and ground stations cache some content that users may request, while cloud servers store all content that users may request. Base stations can transmit cached content to users within their coverage area, satellites can transmit cached content to both base stations and satellite users within their coverage area, ground stations can transmit cached content to satellites, and cloud servers can transmit content stored in the cloud to ground stations.

[0068] When a base station accesses content requested by a user, it can obtain the content directly from the base station, or obtain the content from a satellite, ground station, or cloud server by forwarding; when a satellite accesses content requested by a user, it can obtain the content directly from the satellite, or obtain the content from a ground station or cloud server by forwarding.

[0069] Optionally, refer to Figure 3 The data collected includes user ratio information, content popularity distribution information, cache capacity information, and link latency information in the satellite-ground collaborative network.

[0070] S110. Collect information on the proportion of users accessing the base station and the proportion of users accessing the satellite in the satellite-ground cooperative network, as well as the proportion of users in different areas covered by the satellite-ground cooperative network.

[0071] In the satellite-ground collaborative network, the proportion of users accessing the base station is α, and the proportion of users accessing the satellite is 1-α.

[0072] The satellite-ground collaborative network covers N regions, with β representing the proportion of users in region n. n And there are

[0073] S120. Collect local content popularity distribution information in different areas covered by the satellite-ground collaborative network;

[0074] The set of content that may be cached at base stations, satellites, and ground stations in a space-ground collaborative network is as follows: The total number is F, and each content item has a normalized size of 1; base stations and satellites only cache the content set. Part of the content, a collection of cached content from ground stations. All content in the middle;

[0075] The set of content not cached at base stations, satellites, and ground stations in a space-ground collaborative network is Content Collection Stored only on cloud servers;

[0076] The content popularity distribution differs across the N regions covered by the satellite-ground collaborative network. For region n, the content popularity distribution is as follows: I n (k) = i represents the content in region n whose popularity ranking is k and whose content is f. i .

[0077] S130, Collect base station cache capacity information and satellite cache capacity information;

[0078] Base station buffer capacity is For the content caching strategy of base stations in region n, Content f i Cached in region n base station;

[0079] Satellite cache capacity is For satellite content caching strategy, Content f i It is cached in the satellite.

[0080] S140. Collect link delay information from base station to base station access user, link delay information from satellite to base station, link delay information from satellite to satellite access user, link delay information from ground station to satellite, and link delay information from cloud server to ground station;

[0081] The link delay from base station to user access is τ1, and the link delay from satellite to base station is... The link latency from satellite to satellite access user is The link delay from the ground station to the satellite is τ3, and the link delay from the cloud server to the ground station is τ4.

[0082] S200, based on differentiated user interests and differentiated access modes, identifies the base station and satellite collaborative content caching problem for latency optimization.

[0083] Differentiated user interests refer to the different distribution of content popularity in different areas of the satellite-ground cooperative network; differentiated access mode refers to the simultaneous existence of base station access users and satellite access users in the satellite-ground cooperative network; and latency optimization refers to minimizing the average content retrieval latency for all users in the satellite-ground cooperative network.

[0084] Optionally, refer to Figure 4Based on differentiated user interests and differentiated access modes, the following are identified as potential issues in base station and satellite collaborative content caching for latency optimization:

[0085] S210. For each area covered by the satellite-ground cooperative network, based on the local content popularity distribution of the area, calculate the probability of content storage in the base station, satellite, ground station, and cloud server when a user accessing the base station in the area requests any content; For each area covered by the satellite-ground cooperative network, based on the local content popularity distribution of the area, calculate the probability of content storage in the satellite, ground station, and cloud server when a user accessing the satellite in the area requests any content.

[0086] For users accessing base stations in region n, when requesting arbitrary content:

[0087] The probability that this content is stored in the base station's content storage when it is retrieved is...

[0088] The probability that this content is stored in the satellite's content storage when it is retrieved is...

[0089] The probability that this content is stored at the ground station when it is retrieved is...

[0090] The probability that this content will be stored on the cloud server when it is retrieved is...

[0091] For users with satellite access in region n, when requesting arbitrary content:

[0092] The probability that this content is stored in the satellite's content storage when it is retrieved is...

[0093] The probability that this content is stored at the ground station when it is retrieved is...

[0094] The probability that this content will be stored on the cloud server when it is retrieved is...

[0095] S220. For each area covered by the satellite-ground cooperative network, based on the content storage probability and link delay information, calculate the average content retrieval delay for base station access users and the average content retrieval delay for satellite access users, respectively.

[0096] For region n:

[0097] The average content retrieval latency for users accessing the base station is

[0098]

[0099] The average content retrieval latency for satellite access users is

[0100]

[0101] S230. The average content retrieval latency of all users in all areas within the coverage of the satellite-ground collaborative network is weighted and summed to obtain the average content retrieval latency of the network.

[0102] The average network content retrieval latency is

[0103]

[0104] S240. Taking the base station and satellite collaborative content caching strategy as the optimization variable, minimizing the average network content retrieval latency as the optimization objective, and the base station and satellite cache capacity as the optimization constraint, the content caching problem is obtained.

[0105] The content caching issue is as follows:

[0106]

[0107] st

[0108]

[0109]

[0110]

[0111] Where the optimization variable is x b =[x b,1 ,...,x b,N ],

[0112] S300, Solve the content caching problem to obtain the base station and satellite collaborative content caching strategy;

[0113] Optionally, refer to Figure 5 Solving the content caching problem, the base station and satellite collaborative content caching strategy includes:

[0114] S310. The average content retrieval latency of satellite access users in different regions is equivalently transformed into the average content retrieval latency of all satellite access users under the global content popularity distribution, thereby reducing the computational complexity of the average content retrieval latency of satellite access users.

[0115] In a space-ground collaborative network, the global content popularity distribution can be represented as:

[0116]

[0117] f represents the content whose global popularity ranking is k. i;

[0118] The average content retrieval latency for all satellite access users can be simplified into a calculation.

[0119]

[0120] The average network content service latency can be simplified to the following calculation:

[0121]

[0122] S320: Based on solution space analysis, the solution space size is reduced, thus lowering the search complexity of content caching strategies;

[0123] Optimal solution analysis is performed on the solution space of base station and satellite content caching strategies to obtain the set of possible cached content when the optimal solution is reached, thereby reducing the size of the solution space and thus reducing the search complexity of the content caching strategy.

[0124] Optionally, refer to Figure 6 Based on solution space analysis, reducing the solution space size and lowering the search complexity of content caching strategies include:

[0125] S321. For each region, calculate the fixed cache content and selected cache content of the base station in that region based on the local content popularity distribution information, cache capacity information, and link delay information; in addition, calculate the fixed cache content and selected cache content of the satellite based on the user ratio information, global content popularity distribution information, and cache capacity information.

[0126] For region n, the set of fixed cache contents of the base stations in this region is:

[0127]

[0128]

[0129] Fixed cache content refers to the content that must be cached in the base station content caching strategy;

[0130] For region n, the base station in that region selects the following cache content set:

[0131]

[0132]

[0133] Selected cache content refers to the content that may be cached in the base station content caching strategy. Except for fixed cache content and selected cache content, the rest of the content will not be cached.

[0134] The satellite fixed cache content set is

[0135]

[0136]

[0137] Fixed cache content refers to content that is always cached in the satellite content caching strategy;

[0138] The satellite selects a cached content set as follows

[0139]

[0140]

[0141] Selected cached content refers to the content that may be cached in the satellite content caching strategy. Except for fixed cached content and selected cached content, the rest of the content will not be cached.

[0142] S322. For each region, the solution space of the base station content caching strategy for that region is reduced to the union of the fixed cached content and the selected cached content of the base stations in that region, and the search space of the base station content caching strategy for that region is reduced to the set of the selected cached content of the base stations in that region; in addition, the solution space of the satellite content caching strategy is reduced to the union of the fixed cached content and the selected cached content of the satellite, and the search space of the satellite content caching strategy is reduced to the set of the selected cached content of the satellite.

[0143] Optionally, for region n, the solution space of the base station content caching strategy in that region is reduced to

[0144] For region n, the search space for the base station content caching strategy in this region is reduced to Since the fixed set of cached content is always cached, it is only necessary to search for the remaining cached content in the selected set of cached content.

[0145] Optionally, the solution space for the satellite content caching strategy is reduced to

[0146] The search space for satellite content caching strategies has been reduced to Since the fixed set of cached content is always cached, it is only necessary to search for the remaining cached content in the selected set of cached content.

[0147] S330: Transform the content caching problem into a problem of maximizing latency reduction and gain;

[0148] Let t0 represent the average content retrieval latency for users when the base station and satellite do not cache any content. This indicates that the base station and satellite content caching strategy is x. b ,x s If the average content retrieval latency per user is Γ(x), then... b ,x s ) indicates the caching strategy xb ,x s The resulting delay reduction gain is calculated as

[0149] The content caching problem can be transformed into a problem of maximizing gain while minimizing latency, as follows:

[0150]

[0151] st

[0152]

[0153]

[0154]

[0155] S340. Solve the problem of maximizing the gain of delay reduction after conversion to obtain the base station and satellite collaborative content caching strategy.

[0156] Optionally, refer to Figure 7 Solving the problem of maximizing the gain of latency reduction after conversion, the base station and satellite collaborative content caching strategy is obtained, including:

[0157] Perform the following iterative process:

[0158] S341. Initialize the satellite iterative solution as a fixed set of satellite cache contents;

[0159] initialization l represents the current used capacity of the satellite cache, used for initializing the satellite iterative solution. for

[0160] S342. Initialize all content in the satellite selection cache content set to an unselected state;

[0161] initialization The corresponding satellite selects all content in the cached content set, among which This indicates that the satellite selects content from the cached content set. Initialize to the unselected state.

[0162] S343. Select an unselected content from the satellite selection cache content set, and update the satellite candidate solution corresponding to the content to the union of the satellite iterative solution and the selected content;

[0163] Select a set of cached content from satellites. Selected content renew Update selected content The corresponding satellite candidate solution is

[0164] S344. For each region, calculate the content caching strategy when the base station in that region achieves the maximum latency reduction gain under the satellite candidate solution corresponding to the selected content.

[0165] For each region, calculate the satellite content caching strategy as follows: When the base station in this area achieves the maximum latency reduction gain, the content caching strategy is as follows:

[0166] Optionally, refer to Figure 8 For each region, the content caching strategy for achieving maximum latency reduction gain for the base station in that region, based on the satellite candidate solutions corresponding to the selected content, includes:

[0167] (1) For each region, initialize the base station content caching strategy of that region to the fixed cache content set of the base station in that region;

[0168] For each region, initialize the base station content caching strategy for that region as follows:

[0169] (2) For each region, select each content in the cache content set for the base station in that region, and calculate the reduction in latency for users to retrieve the content when the satellite content caching strategy is a given satellite candidate solution, compared with not caching the content.

[0170] Optionally, for each region, select each piece of content from the cached content set for the base stations in that region. Calculate the satellite content caching strategy for a given satellite candidate solution. At that time, the base station cache content f in this area i With non-cached content f i In comparison, the content f retrieved by users accessing base stations in this area i The amount of delay reduction The calculation is as follows:

[0171]

[0172] in like like

[0173] (3) For each region, select all content in the cache content set of the base station in that region, sort the calculated delay reduction, and add the content with the largest delay reduction to the cache of the base station in that region until the number of cache content of the base station in that region reaches the upper limit of the base station cache capacity.

[0174] Optionally, for each region, a set of cached content is selected for the base stations in that region. All content in the calculation results in a reduction in delay. Sort the data, let θ n (k) = i represents the content f in the cache content set selected by the base station in region n, sorted by delay reduction amount k. i .

[0175] For each region, the base station content caching strategy for that region is as follows:

[0176]

[0177] S345. Based on the satellite candidate solutions corresponding to the selected content and the calculated base station content caching strategy, calculate the corresponding latency reduction gain.

[0178] For the satellite candidate solutions corresponding to the selected content right Each item in make For those that do not belong Each item in make Get satellite content caching strategy x s ;

[0179] For each calculated regional base station content caching strategy right Each item in make For those that do not belong Each item in make Get base station content caching strategy x b ;

[0180] Based on the obtained x s ,x b Calculate delay to reduce gain

[0181] S346. Determine whether there is any unselected content in the satellite selection cache content set; determine the satellite selection cache content set based on the value of k. If there is any content that has not been selected, return to continue selecting the remaining content; if not, compare the satellite candidate solutions corresponding to all content in the satellite selection content set, and update the satellite iterative solution to the satellite candidate solution with the largest delay reduction gain.

[0182] Optionally,

[0183] like If there is content that has not been selected, update k = k + 1, and return to S343 to continue selecting the remaining content.

[0184] like There is no content that has not been selected. The satellite candidate solutions corresponding to all content in the satellite selection content set are compared, and then... for If the maximum value is found, the satellite iterative solution is updated as follows:

[0185] S347. When there is no unselected content, continue to check whether the satellite iteration solution has reached the upper limit of the satellite cache capacity. Based on the value of l, determine whether the satellite iteration solution has reached the upper limit of the satellite cache capacity. If it has not reached the upper limit, return to continue iteration; if it has reached the upper limit, the iteration ends.

[0186] Alternatively, if l+1 < C s If the upper limit has not been reached, update l = l + 1 and return to S342 to continue iterating; if l + 1 = C s If the limit is reached, the iteration ends.

[0187] S348. The satellite content caching strategy obtained is the satellite iterative solution; for each region, the base station content caching strategy obtained is the base station content caching strategy calculated corresponding to the satellite iterative solution.

[0188] The satellite content caching strategy obtained from the solution is the satellite iterative solution. For each region, the base station content caching strategy obtained is the satellite iterative solution in step S344. The corresponding base station content caching strategy is calculated; the corresponding variable x s ,x b The value can be obtained based on the method in step S345, which will not be repeated here.

[0189] S400: Based on the obtained content caching strategy, the content is cached at the base station and satellite to provide content services for base station access users and satellite access users in the network.

[0190] This invention proposes a satellite-ground collaborative network content caching method under differentiated interest and access modes. Through collaborative caching between base stations and satellites, it provides edge content services to both base station-accessed and satellite-accessed users simultaneously, under differentiated user interest distributions. Based on global content popularity and solution space analysis, this invention reduces the computational complexity of average content retrieval latency for satellite users and the search complexity of content caching strategies. It transforms the content caching problem into a latency reduction gain maximization problem, ultimately solving for the base station-satellite collaborative content caching strategy that minimizes average content retrieval latency.

[0191] A schematic diagram of the satellite-ground collaborative network in this embodiment is shown below. Figure 2 As shown, the proportion of users accessing the base station is 0.9, the proportion of users accessing the satellite is 0.1, the number of regions is 3, the proportion of users in each region is 1 / 3, the number of content items that users may request is 500-2000, the base station cache capacity is 200, the satellite cache capacity is 200, the link latency from base station to base station access user is 20ms, the link latency from satellite to base station is 100ms, the link latency from satellite to satellite access user is 100ms, the link latency from ground station to satellite is 100ms, and the link latency from cloud server to ground station is 500ms. The local content popularity distribution in each region adopts a Zipf distribution with a factor of 0.5. (Reference) Figure 9 As can be seen, under differentiated user interest distribution and differentiated access modes, the content caching method proposed in this embodiment can reduce the average content retrieval latency by 30% compared to the random caching method, and by 20% compared to the most popular caching method. The content caching method for satellite-ground cooperative networks under differentiated interest and access modes proposed in this invention can effectively reduce the content retrieval latency for base station access users and satellite access users in satellite-ground cooperative networks, alleviate the problem of long communication latency caused by long transmission distances of satellite-ground links, improve user experience, and support various latency-sensitive services.

[0192] The computer program product of the satellite-ground cooperative network content caching method under differentiated interest and access modes provided in this embodiment of the invention includes a computer-readable storage medium storing program code. The instructions included in the program code can be used to execute the methods described in the preceding method embodiments. For specific implementation, please refer to the method embodiments, which will not be repeated here.

[0193] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working process of the system and apparatus described above can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0194] If the aforementioned functions are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this invention, essentially, or the part that contributes to the prior art, or a portion of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0195] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions or improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for caching content in a satellite-ground collaborative network under differentiated interest and access modes, characterized in that, Includes the following steps: (1) Collect user ratio information, content popularity distribution information, cache capacity information, and link delay information in the satellite-ground collaborative network; the satellite-ground collaborative network consists of base stations, satellites, base station access users, satellite access users, ground stations, and cloud servers; the coverage area of ​​the satellite-ground collaborative network is divided into multiple regions, and different regions have different local content popularity distributions; (2) Based on differentiated user interests and differentiated access modes, determine the base station and satellite collaborative content caching problem for latency optimization; the latency optimization refers to minimizing the average content retrieval latency for all users in the satellite-ground collaborative network; step (2) includes the following sub-steps: (2.1) For each area covered by the satellite-ground cooperative network, based on the local content popularity distribution in that area, calculate the content storage probability of the content in the base station, satellite, ground station, and cloud server when a user requests any content through the base station in that area; For each area covered by the satellite-ground collaborative network, based on the local content popularity distribution in that area, the probability of content being stored on the satellite, ground station, and cloud server when a satellite access user in that area requests any content is calculated. (2.2) For each area covered by the satellite-ground cooperative network, based on the content storage probability and link delay information, calculate the average content retrieval delay for base station access users and the average content retrieval delay for satellite access users respectively; (2.3) The average content retrieval delay of all users in all areas within the coverage of the satellite-ground collaborative network is weighted and summed to obtain the average content retrieval delay of the network; (2.4) Taking the base station and satellite collaborative content caching strategy as the optimization variable, minimizing the average network content retrieval latency as the optimization objective, and the base station and satellite cache capacity as the optimization constraint, the content caching problem is obtained; (3) Solve the content caching problem to obtain the base station and satellite collaborative content caching strategy; (3.1) The average content retrieval delay of satellite access users in different regions is equivalently transformed into the average content retrieval delay of all satellite access users under the global content popularity distribution, thereby reducing the computational complexity of the average content retrieval delay of satellite access users. (3.2) Based on solution space analysis, reduce the size of the solution space and reduce the search complexity of the content caching strategy; (3.3) The content caching problem is transformed into a latency reduction gain maximization problem; the latency reduction gain refers to the reduction in average user content retrieval latency under the current content caching strategy compared to when the base station and satellite do not cache any content; (3.4) Solve the problem of maximizing the gain of delay reduction after conversion to obtain the base station and satellite collaborative content caching strategy; (4) Based on the obtained content caching strategy, the content is cached at the base station and satellite to provide content services for base station access users and satellite access users in the network.

2. The method for caching content in a satellite-ground cooperative network under differentiated interest and access modes as described in claim 1, characterized in that, In step (1), there is a communication link between the base station and the base station access users within the coverage area, there is a communication link between the satellite and the base station and satellite access users within the coverage area, there is a communication link between the ground station and the satellite, and there is a communication link between the cloud server and the ground station; the base station, satellite, and ground station cache some content that users may request, and the cloud server stores all content that users may request. Base stations can transmit cached content to users within their coverage area; satellites can transmit cached content to both base stations and satellite users within their coverage area; ground stations can transmit cached content to satellites; and cloud servers can transmit cloud-stored content to ground stations.

3. The method for caching content in a satellite-ground cooperative network under differentiated interest and access modes as described in claim 1, characterized in that, The user ratio information mentioned in step (1) refers to the ratio of users accessing the base station and users accessing the satellite in the satellite-ground cooperative network, as well as the ratio of users in different areas covered by the satellite-ground cooperative network. The content popularity distribution information refers to the local content popularity distribution information in different regions covered by the satellite-ground collaborative network; The cache capacity information includes base station cache capacity information and satellite cache capacity information; The link delay information includes link delay information from base station to base station access user, link delay information from satellite to base station, link delay information from satellite to satellite access user, link delay information from ground station to satellite, and link delay information from cloud server to ground station.

4. The method for caching content in a satellite-ground cooperative network under differentiated interest and access modes as described in claim 1, characterized in that, The sub-step (3.2) includes the following process: (3.2.1) For each region, calculate the fixed cache content and selected cache content of the base station in that region based on the local content popularity distribution information, cache capacity information and link delay information of that region; the fixed cache content refers to the content that must be cached in the content caching strategy obtained by solving the content caching problem, and the selected cache content refers to the content that may be cached in the content caching strategy obtained by solving the content caching problem. In addition, satellite fixed cache content and selected cache content are calculated based on user ratio information, global content popularity distribution information, and cache capacity information. (3.2.2) For each region, the solution space of the base station content caching strategy in that region is reduced to the union of the fixed cached content and the selected cached content of the base station in that region, and the search space of the base station content caching strategy in that region is reduced to the set of the selected cached content of the base station in that region. In addition, the solution space of the satellite content caching strategy is reduced to the union of the fixed cached content and the selected cached content of the satellite, and the search space of the satellite content caching strategy is reduced to the set of the selected cached content of the satellite.

5. The satellite-ground collaborative network content caching method under differentiated interest and access modes as described in claim 4, characterized in that, Step (3.4) specifically includes the following iterative process: (3.4.1) Initialize the satellite iterative solution as a fixed set of satellite cache contents; (3.4.2) Initialize all content in the satellite selection cache content set to an unselected state; (3.4.3) Select an unselected content from the satellite selection cache content set, and update the satellite candidate solution corresponding to the content to the union of the satellite iterative solution and the selected content; (3.4.4) For each region, calculate the content caching strategy when the base station in that region achieves the maximum latency reduction gain under the satellite candidate solution corresponding to the selected content; (3.4.5) Based on the satellite candidate solutions corresponding to the selected content and the calculated base station content caching strategy, calculate the corresponding latency reduction gain; (3.4.6) Determine whether there is any unselected content in the satellite's selected cache content set; If it exists, return to (3.4.3); if it does not exist, compare the satellite candidate solutions corresponding to all contents in the satellite selection content set, and update the satellite iterative solution to the satellite candidate solution with the largest delay reduction gain; (3.4.7) If there is no unselected content in the satellite's selected cache content set, continue to determine whether the satellite's iterative solution has reached the upper limit of the satellite cache capacity; If the upper limit is not reached, return to (3.4.2); if the upper limit is reached, the iteration ends. (3.4.8) The satellite content caching strategy obtained by solving is the satellite iterative solution; for each region, the base station content caching strategy obtained by solving is the base station content caching strategy calculated in (3.4.4) corresponding to the satellite iterative solution.

6. The satellite-ground collaborative network content caching method under differentiated interest and access modes as described in claim 5, characterized in that, Step (3.4.4) specifically includes the following process: (3.4.4.1) For each region, initialize the base station content caching strategy for that region to a fixed set of base station cache content for that region; (3.4.4.2) For each region, select each content in the cache content set for the base station in that region, and calculate the reduction in latency for users accessing the base station in that region to retrieve the content when the satellite content caching strategy is a given satellite candidate solution, compared to not caching the content. (3.4.4.3) For each region, select all content in the cache content set of the base station in that region, sort the calculated delay reduction, and add the content with the largest delay reduction to the cache of the base station in that region until the number of cached content in the base station in that region reaches the upper limit of the base station cache capacity.

7. An electronic device, characterized in that, include: One or more processors; A storage device for storing one or more programs, which, when executed by the electronic device, cause the electronic device to implement the satellite-ground cooperative network content caching method under the differentiated interest and access mode as described in any one of claims 1 to 6.

8. A computer-readable storage medium, characterized in that, It stores a program that, when executed by a processor, implements the satellite-ground cooperative network content caching method under the differentiated interest and access mode as described in any one of claims 1 to 6.

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