Joint Optimization Method for Content Update, Push, and Transmission and Wireless Caching Network

Abstract

The present invention provides a joint optimization method for content update, push, and transmission, and a wireless caching network, which is applied to a central controller of the wireless caching network. The wireless caching network includes: a central controller, at least one macro base station, multiple user devices, and at least one content server. The central controller receives content requests of user devices obtained from the base stations, groups users based on content identifiers and geographical locations, and the content requests of users in the same group are the same. The central controller quantifies the caching value according to the content popularity and file size, combines the utility function with the channel parameters, and generates a file update strategy. The macro base station distributes content to multicast group users and content servers. The content server caches updated files and serves users within its coverage area. This method achieves the dual maximization of the cache hit rate and the user device rate, improves the data transmission efficiency and user experience, and provides an efficient and practical solution for content update, push, and transmission.

Description

Technical Field

[0001] The present invention relates to the field of communication technologies, and particularly to a joint optimization method for content update, push, and transmission, and a wireless caching network. Background Art

[0002] In recent years, with the popularization of mobile devices and the sharp increase in the number of mobile applications, mobile network traffic has shown an explosive growth trend. This phenomenon not only exacerbates network congestion problems, but also leads to a significant increase in network latency and a significant decline in user experience, making it difficult to fully meet the needs of mobile users. To solve this series of problems, wireless caching technology has gradually emerged and demonstrated great potential in the field of the fifth-generation mobile communication (5G).

[0003] In the development process of 5G mobile communication, edge caching technology has become a key technology in mobile edge computing due to its unique advantages. By reusing hot content in the network, this technology significantly reduces the transmission burden on the wireless network, thereby effectively improving the user's network experience. As a core means to improve the performance of wireless networks, wireless caching technology has currently become a research hotspot in both academia and industry. It can significantly reduce network latency, increase the throughput of data transmission, and further enhance the user's network usage experience.

[0004] During off-peak hours, edge caching technology pre-stores commonly used files in cache devices closer to user devices, such as nearby base stations, access points, or even user devices. When a user device needs to access these files, due to the greatly shortened physical distance between the user device and the cached content, the requested files can be retrieved and transmitted at a higher rate, effectively reducing latency and network congestion. At the same time, this caching strategy also relieves the pressure on other network traffic and improves the operating efficiency of the entire network.

[0005] However, although edge caching technology has achieved remarkable results in improving the performance of wireless networks, it is still necessary to optimize cache hit rate, user device rate, etc. Summary of the Invention

[0006] In view of this, embodiments of the present disclosure provide a joint optimization method for content update, push, and transmission, and a wireless caching network, which at least partially solve the problems existing in the prior art.

[0007] In a first aspect, embodiments of the present disclosure provide a joint optimization method for content update, push, and transmission, which is applied to a central controller of a wireless caching network. The wireless caching network includes: the central controller, at least one macro base station, multiple user devices, and at least one content server. The method includes:

[0008] Receive content requests sent by multiple of the user equipments forwarded by any one of the macro base stations, where the content requests are used to request feedback of content files to the user equipments;

[0009] Group the multiple user equipments according to the content identifiers and location information respectively corresponding to each content request, to obtain multiple user equipment groups and corresponding grouping information, where the content identifier is used to indicate the content file requested by the user equipment, and the location information is used to represent the geographical location of the user equipment, and the content identifiers corresponding to each user equipment in any one of the user equipment groups are the same;

[0010] For each content identifier corresponding to each user equipment group, generate a cache utility function according to the popularity and size factor corresponding to the content file indicated by the content identifier;

[0011] Determine the to-be-updated files that need to be cached in the content server according to the cache utility function and a preset file update algorithm, where the to-be-updated files are content files requested by the user equipments but not cached in the content server;

[0012] Generate an update strategy according to the to-be-updated files, and generate a transmission strategy according to the channel parameters of the wireless cache network, where the update strategy is used to instruct the content server to feedback the to-be-updated files to multiple user equipments, and the transmission strategy is used to instruct the macro base station to transmit the to-be-updated files to the user equipments and / or the content server;

[0013] Send the transmission strategy to the macro base station, so that the macro base station, according to the transmission strategy, feedbacks the content files corresponding to the content identifier to each user equipment in the multicast group, and sends the to-be-updated files to at least one content server, and each user equipment in the multicast group is located outside the transmission range of each content server;

[0014] Send the update strategy to at least one content server, so that each content server, according to the update strategy, caches the to-be-updated files through the macro base station, and feedbacks the content files corresponding to the content identifier to at least one user equipment in at least one user equipment group within the transmission range.

[0015] According to a specific implementation manner of an embodiment of the present disclosure, the grouping the multiple user equipments according to the content identifiers and location information respectively corresponding to each content request, to obtain multiple user equipment groups and corresponding grouping information, includes:

[0016] For each of the content requests, obtain the content identifier and the location information carried by the content request;

[0017] According to the multiple content identifiers and the multiple location information, group the multiple user devices to obtain multiple user device groups and the corresponding grouping information.

[0018] According to a specific implementation manner of an embodiment of the present disclosure, the grouping the multiple user devices according to the multiple content identifiers and the multiple location information to obtain multiple user device groups and the corresponding grouping information includes:

[0019] According to the multiple content identifiers, divide at least one user device corresponding to the same content identifier into one user device group;

[0020] According to each location information, determine whether each user device is within the transmission range of any one of the content servers;

[0021] For each user device, if the user device is within the transmission range of any one of the content servers, then retain the user device in the user device group to which it belongs;

[0022] If the user device is outside the transmission range of each content server, then adjust the user device from the user device group to which it belongs to a multicast group;

[0023] Generate the grouping information according to at least one of the user device groups and the multicast group.

[0024] According to a specific implementation manner of an embodiment of the present disclosure, the determining the files to be updated that need to be cached in the content server according to the cache utility function and a pre-set file update algorithm includes:

[0025] For each content server, according to the location information corresponding to each content identifier, determine at least one target user device covered by the transmission range of the content server;

[0026] According to the content identifier corresponding to each target user device, determine at least one file to be cached corresponding to each target user device, where the file to be cached is a file requested by the target user device and not cached by the content server;

[0027] Determine the caching priority of each file to be cached through the cache utility function;

[0028] Select a preset number of the files to be cached as the files to be updated according to the caching priorities of each of the files to be cached.

[0029] According to a specific implementation manner of an embodiment of the present disclosure, the generating a transmission strategy according to the channel parameters of the wireless caching network includes:

[0030] Obtain a transmission rate according to the channel parameters, where the channel parameters include: channel state, the maximum transmit power of the macro base station, user receiving quality of service constraints, energy conversion efficiency, and signal strength ratio;

[0031] Optimize a beamforming vector and a non-orthogonal multiple access (NOMA) power allocation factor according to the transmission rate to obtain a target beamforming vector and a target NOMA power allocation factor. The target beamforming vector is used to instruct the macro base station to send the content file to the user equipment and / or the content server according to the parameters corresponding to the target beamforming vector, and the target NOMA power allocation factor is used to instruct the content server to feedback the content file to the user equipment according to the parameters corresponding to the target NOMA power allocation factor;

[0032] Obtain a target transmission rate according to the target beamforming vector and the target NOMA power allocation factor;

[0033] Generate the transmission strategy according to the target beamforming vector, the target NOMA power allocation factor, and the target transmission rate.

[0034] According to a specific implementation manner of an embodiment of the present disclosure, the optimizing a beamforming vector and a non-orthogonal multiple access (NOMA) power allocation factor according to the transmission rate to obtain a target beamforming vector and a target NOMA power allocation factor includes:

[0035] Obtain, in a first phase, a first signal-to-interference-plus-noise ratio (SINR) corresponding to each of the user equipments, and the energy collected by each of the content servers. The first phase is the phase in which the macro base station sends the content file to the user equipment and the content server;

[0036] Determine the power of the content server in a second phase according to the energy. The second phase is the phase in which the content server sends the content file to the user equipment;

[0037] Determine a second SINR corresponding to each of the user equipments in the second phase according to the power of the content server in the second phase;

[0038] Determine the expression of the sum rate of the user equipment according to the first SINR and the second SINR;

[0039] Calculate the expression of the sum rate of the user equipment to obtain the target beamforming vector and the target NOMA power allocation factor.

[0040] In a second aspect, an embodiment of the present disclosure provides a joint optimization method for content update, push, and transmission, which is applied to a content server of a wireless caching network;

[0041] The wireless caching network includes: a central controller, at least one macro base station, multiple user equipment, and at least one content server, and the method includes:

[0042] Receive the update policy sent by the central controller, where the update policy is generated by the central controller according to each content identifier corresponding to the packet information sent by any one of the macro base stations in combination with a pre-set file update algorithm;

[0043] According to the to-be-updated file indicated by the update policy, receive the to-be-updated file sent by at least one of the macro base stations, update the cached content file, and cache the to-be-updated file, where the to-be-updated file is a content file requested by the user equipment but not cached by the content server;

[0044] For at least one of the content identifiers included in the update policy, send the content file corresponding to the content identifier to the user equipment corresponding to the content identifier.

[0045] According to a specific implementation manner of an embodiment of the present disclosure, the step of receiving the to-be-updated file sent by at least one of the macro base stations according to the to-be-updated file indicated by the update policy, updating the cached content file, and caching the to-be-updated file includes:

[0046] Determine the target storage space required for the to-be-updated file;

[0047] Obtain the deletion priority carried by the update policy, where the deletion priority is used to represent the priority among the content files that are not requested and cached in the content server;

[0048] Delete at least one of the content files cached in the content server according to the target storage space and the deletion priority;

[0049] Receive the to-be-updated file sent by at least one of the macro base stations and cache the to-be-updated file.

[0050] In a third aspect, embodiments of the present disclosure provide a wireless caching network, which includes a central controller, at least one of the macro base stations, multiple user devices, and at least one content server;

[0051] The macro base station is configured to receive content requests sent by multiple user devices, and the content requests are used to request content files to be fed back to the user devices;

[0052] The macro base station is further configured to forward the content requests to the central controller;

[0053] The central controller is configured to receive the content requests sent by any one of the macro base stations;

[0054] The central controller is further configured to group the multiple user devices according to the content identifiers and location information respectively corresponding to each content request, to obtain multiple user device groups and corresponding grouping information. The content identifier is used to indicate the content file requested by the user device, and the content identifiers corresponding to each user device group are the same. The location information is used to represent the geographical location of the user device;

[0055] For each content identifier corresponding to each grouping information, the central controller is further configured to generate a caching utility function according to the popularity and size factor of the content file indicated by the content identifier;

[0056] The central controller is further configured to determine the files to be updated that need to be cached in the content server according to the caching utility function and a pre-set file update algorithm. The files to be updated are content files requested by the user devices but not cached in the content server;

[0057] The central controller is further configured to generate an update strategy according to the files to be updated and generate a transmission strategy according to the channel parameters of the wireless caching network. The update strategy is used to instruct the content server to feed back the cached files to be updated to multiple user devices, and the transmission strategy is used to instruct the macro base station to transmit the files to be updated to the user devices and / or the content server;

[0058] The central controller is further configured to send the transmission strategy to the macro base station and send the update strategy to at least one content server;

[0059] The macro base station is further configured to, according to the transmission strategy fed back by the central controller, feed back content files corresponding to the content identifier to each user device in the multicast group and send the files to be updated to the content server. Each user device in the multicast group is located outside the transmission range of each content server;

[0060] The content server is used to receive the update policy sent by the central controller;

[0061] The content server is further used to receive the to-be-updated file sent by at least one of the macro base stations according to the to-be-updated file indicated by the update policy, and update the cached content file;

[0062] According to at least one content identifier included in the update policy, send the content file corresponding to the content identifier to each user equipment corresponding to the content identifier.

[0063] In summary, compared with the prior art, the present embodiment has the following advantages:

[0064] 1. In this embodiment, by comprehensively considering the size and popularity of cached files, a cache utility function and a corresponding cache update algorithm are designed. This method can optimize the cached content according to the access frequency and size of the files, thereby maximizing the cache hit rate.

[0065] 2. Based on user equipment grouping and file update policies, this embodiment establishes a two-stage sum rate optimization problem aiming to maximize the user equipment rate. Through user equipment grouping and transmission strategy design, the system can ensure that within different transmission stages, user equipment can obtain the best data transmission rate according to their own needs and network conditions.

[0066] All in all, by comprehensively considering multiple key factors of caching and content transmission, this embodiment realizes the dual maximization of the cache hit rate and the user equipment rate, provides an efficient and practical solution for the joint optimization of content update, push and transmission, and improves the data transmission efficiency and user experience. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] To make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below in conjunction with specific embodiments and drawings. Herein, the illustrative embodiments of the present invention and their descriptions are used to explain the present invention, but not to limit the present invention.

[0068] The term "including" and its variations used herein mean open inclusion, that is, "including but not limited to". Unless otherwise stated, the term "or" means "and / or". The term "based on" means "at least partially based on". The term "an example embodiment" and "an embodiment" mean "at least one example embodiment". The term "another embodiment" means "at least one additional embodiment". The terms "first", "second", etc. may refer to different or the same objects. There may be other explicit and implicit definitions hereinafter.

[0069] Figure 1 Network schematic diagram of a wireless caching network involved in a joint optimization method for content update, push, and transmission proposed in an embodiment of the present application;

[0070] Figure 2 Schematic flowchart of a joint optimization method for content update, push, and transmission provided in an embodiment of the present application;

[0071] Figure 3 Schematic flowchart of a process for obtaining an update strategy provided in an embodiment of the present application;

[0072] Figure 4 Schematic diagram of the change curve of the cache file hit rate in a content server with respect to the content server size provided in an embodiment of the present application;

[0073] Figure 5 Schematic diagram of the change curve of the sum rate of the transmission part with respect to power provided in an embodiment of the present application;

[0074] Figure 6 Shows an exemplary structural schematic diagram of a device capable of implementing the method according to an embodiment of the present invention. Detailed implementation manners

[0075] The embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings.

[0076] The following uses specific specific examples to illustrate the implementation manners of the present disclosure. Those skilled in the art can easily understand other advantages and effects of the present disclosure from the content disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of the present disclosure, rather than all of the embodiments. The present disclosure can also be implemented or applied through other different specific implementation manners. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present disclosure. It should be noted that, without conflict, the following embodiments and the features in the embodiments can be combined with each other. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present disclosure without creative efforts fall within the scope of protection of the present disclosure.

[0077] Note that the following description relates to various aspects of embodiments within the scope of the appended claims. It should be apparent that the aspects described herein can be embodied in a wide variety of forms, and any specific structure and / or function described herein is merely illustrative. Based on this disclosure, those skilled in the art should understand that one aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number of the aspects described herein can be used to implement a device and / or practice a method. Additionally, this device and / or method can be implemented using other structures and / or functionality in addition to one or more of the aspects described herein.

[0078] It should also be noted that the diagrams provided in the following embodiments only schematically illustrate the basic concept of the present disclosure. The diagrams only show the components related to the present disclosure and are not drawn according to the number, shape, and size of the components in actual implementation. The type, quantity, and proportion of each component in actual implementation can be arbitrarily changed, and the component layout type may also be more complex.

[0079] In addition, in the following description, specific details are provided to facilitate a thorough understanding of the examples. However, those skilled in the art will understand that the aspects described herein can be practiced without these specific details.

[0080] See Figure 1 , Figure 1 is a network schematic diagram of a wireless caching network involved in a joint optimization method for content update, push, and transmission proposed in an embodiment of the present application. The wireless caching network may include: a central controller 110, at least one macro base station 120, multiple user devices 130, and at least one content server 140.

[0081] Among them, each macro base station 120 can be linked to the central controller 110, user devices 130, and content server 140, and the content server 140 can also be linked to the central controller 110 and user devices 130.

[0082] Specifically, for each user device 130, the user device 130 can generate a content request according to an operation triggered by the user and send the content request to a nearby macro base station 120. Correspondingly, the macro base station 120 can receive the content requests sent by multiple user devices 130 and forward multiple content requests to the central controller 110.

[0083] Correspondingly, the central controller 110 can group multiple user devices 130 according to the content identifiers and location information included in multiple content requests to obtain multiple user device groups and corresponding grouping information.

[0084] Among them, the content identifier is used to indicate the content file requested by the user equipment 130, and the content identifiers corresponding to each user equipment group are the same. The location information is used to represent the geographical location of the user equipment 130.

[0085] Moreover, the central controller 110 can determine the content identifiers included in the grouping information according to the grouping information, and determine the popularity and size factor corresponding to the content file indicated by each content identifier according to the content identifiers included in each grouping information.

[0086] After that, the central controller 110 can generate a cache utility function according to the popularity and size factor corresponding to each content file respectively, so that it can determine the files to be updated that need to be cached in the content server 140 according to the cache utility function, in combination with the pre-set file update algorithm, and generate an update policy according to the files to be updated and a transmission policy according to the channel parameters of the wireless cache network, so that it can send the transmission policy to the macro base station 120 and send the update policy to the content server 140, so that the content server 140 can feedback the cached files to be updated to the user equipment 130.

[0087] Correspondingly, the macro base station 120 can feedback to each user equipment 130 in the multicast group according to the received transmission policy, and send the content file corresponding to the content identifier to each user equipment 130 according to the content identifier in the content request sent by each user equipment 130.

[0088] Moreover, the macro base station 120 can also send the files to be updated to the content server 140 according to the transmission policy.

[0089] Similarly, the content server 140 can receive the update policy sent by the central controller 110, and receive the files to be updated sent by the macro base station 120 according to the update policy, so that it can cache the received files to be updated and send the cached content files to the user equipment 130.

[0090] It should be noted that in practical applications, the wireless cache network may include multiple macro base stations 120, multiple user equipment 130, and multiple content servers 140. For the sake of simplicity in the embodiments of the present application, only one macro base station 120, one user equipment 130, and one content server 140 are taken as examples for illustration, and the embodiments of the present application do not make specific limitations on the numbers of the macro base station 120, the user equipment 130, and the content server.

[0091] The following details the process of data transmission among various devices in the wireless cache network.

[0092] Figure 2Schematic flowchart of a joint optimization method for content update, push, and transmission provided by an embodiment of this application. As an example but not a limitation, it is applied to a central controller, at least one macro base station, and at least one content server in a wireless caching network. Refer to Figure 2 The method includes:

[0093] Step 201: The macro base station receives content requests sent by multiple user devices.

[0094] Among them, the content request is used to request a content file to be fed back to the user device. For example, in the process of generating a content request, the user device can determine the content identifier corresponding to the required content file according to the user-triggered action, and then combine the geographical location where the user device is currently located to generate and send a content request to the macro base station, where the content identifier is used to uniquely identify the requested content file.

[0095] In addition, the above content file can be a video file, an image file, or a text file, and the embodiment of this application does not make specific limitations on the type of the content file.

[0096] In the process of data transmission in the wireless caching network, the user device can send a content request to the macro base station to request the required content file from the macro base station or the content server through the content request. Correspondingly, the macro base station can receive the content request sent by the user device through the channel between the macro base station and the user device.

[0097] For example, in the process of sending a content request to the macro base station, the user device can randomly access any channel between the user device and the macro base station to send a content request to the macro base station. Correspondingly, in the process of data transmission through multiple channels, the macro base station can receive the content request.

[0098] It should be noted that in actual applications, the macro base station can receive content requests sent by multiple user devices. For the sake of simplicity in the embodiment of this application, only the case where the macro base station receives a content request sent by one user device is used as an example for illustration, and the embodiment of this application does not make specific limitations on the number of user devices sending content requests to the macro base station and the number of content requests received by the macro base station.

[0099] Step 202: The macro base station forwards the content requests of multiple user devices to the central controller.

[0100] After obtaining the content requests sent by multiple user devices, the macro base station can send each content request to the central controller so that the central controller can group multiple user devices according to multiple content requests, and thus can adopt different methods to feed back content files to each user device for different groups of user devices.

[0101] It should be noted that in practical applications, the macro base station can periodically send content requests sent by multiple user devices to the central controller, or can immediately send a content request to the central controller after receiving content requests sent by multiple user devices. The embodiments of the present application do not make specific limitations on the timing of the macro base station sending content requests.

[0102] Step 203: The central controller receives content requests sent by multiple user devices forwarded by any one macro base station.

[0103] Corresponding to step 202, the central controller can receive multiple content requests sent by the macro base station, so that in subsequent steps, it can group multiple user devices according to the multiple content requests, and thus feedback content files to user devices in different groups in different ways.

[0104] It should be noted that the embodiments of the present application are described by taking the central controller receiving a content request sent by one macro base station once as an example. In practical applications, the central controller can receive multiple content requests sent by multiple macro base stations. The embodiments of the present application do not make specific limitations on the number of macro base stations and the number of times of sending content requests.

[0105] Step 204: The central controller groups multiple user devices according to the content identifier and location information respectively corresponding to each content request, and obtains multiple user device groups and corresponding grouping information.

[0106] Among them, the content identifier is used to indicate the content file requested by the user device, the content identifiers corresponding to each user device in any one user device group are the same, and the location information is used to represent the geographical location of the user device.

[0107] After receiving the content requests sent by each user device forwarded by the macro base station, the central controller can identify multiple content requests, and group each user device according to the content identifier and location information corresponding to each content request, so that in subsequent steps, it can feedback corresponding content files to user devices in different user device groups.

[0108] Optionally, for each content request, the central controller can obtain the content identifier and location information carried by the content request, and group multiple user devices according to the multiple content identifiers and multiple location information, and obtain multiple user device groups and corresponding grouping information.

[0109] Specifically, the central controller can identify each content request, determine the content identifier and location information included in each content request, and then traverse each content identifier, and divide the user devices belonging to the same content identifier into the same user device group, so that multiple user device groups can be obtained.

[0110] Furthermore, in actual applications, some user devices may not be within the transmission range of any content server, and content files can be fed back to these user devices through the macro base station. Accordingly, the central controller can identify each user device in each user device group based on the location information of each user device and the location information of each content server, and determine whether each user device receives content files through the macro base station or the content server, which can achieve efficient use of resources in the wireless cache network and meet the diverse content needs of user devices.

[0111] Specifically, the central controller may classify at least one user device corresponding to the same content identifier into a user device group according to multiple content identifiers, and determine whether each user device is located within the transmission range of any content server according to each location information.

[0112] For each user device, if the user device is within the transmission range of any content server, the user device can be retained in the user device group to which it belongs; however, if the user device is outside the transmission range of each content server, the user device can be adjusted from the user device group to which it belongs to the multicast group, thereby completing the grouping of user devices based on at least one user device group and multicast group, and generating grouping information.

[0113] Among them, each grouping information may include: the content identifier corresponding to the user device group, the device identifier corresponding to the user device to which each content identifier belongs, the device identifier is used to uniquely indicate the user device, and the device identifier can be sent from the user device to the macro base station through a content request.

[0114] Step 205: For each content identifier corresponding to each grouping information, the central controller generates a cache utility function according to the popularity and size factor of the content file indicated by the content identifier.

[0115] Among them, file popularity is used to indicate the frequency of content files being requested by user devices within a certain period of time, which can indicate the user device's interest in and demand for the content file and can be used as an important parameter of the cache utility function. The size factor is used to indicate the size of the content file.

[0116] After obtaining multiple grouping information, the central controller can identify the content identifier corresponding to each grouping information, determine the content file requested by the user device group indicated by each grouping information, and generate a cache utility function based on the file popularity and size factor corresponding to the multiple requested content files.

[0117] For example, if N content files are included, A set of content files requested by a user device, and a set of sizes corresponding to each content file is , then for the file The corresponding cache utility function value As shown in formula (1):

[0118] (1)

[0119] Where is the file popularity of the th content file, is the size factor of the th content file, is the weighting parameter between file popularity and size factor.

[0120] Where, the file popularity follows the Zipf distribution, then for the requested file The popularity As shown in formula (2):

[0121] (2)

[0122] Where , is the power exponent, representing the file popularity parameter, represents the ranking; is the power of the ranking, representing the weight or contribution of the n th element; is the general term in the summation, representing calculating its weight for each index i . The role of the denominator is to normalize the sum of the weights of all elements to 1. . is the index variable during summation, traversing all integers from 1 to N for calculating the sum of the weights of all elements.

[0123] Assume that the sizes of the content files requested by each user device are different, and for the requested content file The corresponding size factor As shown in formula (3):

[0124] (3)

[0125] is the file size corresponding to the content file , is D N The file size corresponding to the largest content file in, that is, S N The largest parameter in.

[0126] Step 206: The central controller determines the files to be updated that need to be cached in the content server according to the cache utility function and the preset file update algorithm.

[0127] Among them, the files to be updated are content files requested by user devices but not cached in the content server. Moreover, the file size of the files to be updated corresponding to each content server is less than or equal to the storage space of the content server.

[0128] After the central controller generates the corresponding cache utility function for each content file, it can, based on the function values corresponding to each cache utility function, in combination with the preset file update algorithm, determine which content files need to be cached in the content server, so as to determine the files to be updated that need to be cached in the content server.

[0129] Optionally, for each content server, the central controller can determine at least one target user device covered by the transmission range of the content server according to the location information corresponding to each content identifier, determine at least one file to be cached corresponding to each target user device according to the content identifier corresponding to each target user device, and then determine the caching priority of each file to be cached through the cache utility function, so as to select a preset number of files to be cached as the files to be updated according to the caching priority of each file to be cached.

[0130] Among them, the files to be cached can be files requested by target user devices and not cached in the content server.

[0131] Moreover, in practical applications, the central controller can combine the content files cached in each content server and the files to be cached that need to be cached to determine the caching priorities corresponding to the multiple files to be cached that need to be cached in the content server, so as to obtain the files to be updated corresponding to the content server, and thus obtain the files to be updated corresponding to multiple content servers respectively.

[0132] Specifically, for each content server, the central controller can determine each content file currently cached in the content server and determine the content identifiers corresponding to each target user device located within the coverage range of the content server, so as to determine the content files requested by each target user device within the coverage range.

[0133] After that, the central controller can determine which content files need to be cached in the content server according to the content files currently cached in the content server and the content files requested by each target user device within the coverage range, so as to determine the files to be cached.

[0134] Further, the central controller can analyze multiple files to be cached, determine the caching priority corresponding to each file to be cached, and determine the files to be updated from the multiple files to be cached according to the caching priority.

[0135] Step 207: The central controller generates an update policy according to the files to be updated, and generates a transmission policy according to the channel parameters of the wireless caching network.

[0136] Among them, the update policy is used to instruct the content server to feedback the files to be updated to multiple user devices, and the transmission policy is used to instruct the macro base station to transmit the files to be updated to the user devices and / or the content server.

[0137] After the central controller determines the files to be updated corresponding to each content server, it can generate an update policy according to the multiple files to be updated. At the same time, it can also generate a transmission policy according to the channel parameters of the wireless caching network, so that in the subsequent steps, the macro base station can update the content cached by at least one content server according to the transmission policy and in combination with the update policy received by the content server, and complete the data transmission between the content server and the user devices.

[0138] Optionally, in the process of generating the transmission policy by the central controller according to the channel parameters of the wireless caching network, it can first obtain the transmission rate according to the channel parameters, optimize the beamforming vector and the non-orthogonal multiple access (NOMA) power allocation factor according to the transmission rate to obtain the target beamforming vector and the target NOMA power allocation factor, then obtain the target transmission rate according to the target beamforming vector and the target NOMA power allocation factor, and finally generate the transmission policy according to the target beamforming vector, the target NOMA power allocation factor and the target transmission rate.

[0139] Among them, the channel parameters include: channel state, maximum transmission power of the macro base station, user receiving quality of service constraint, energy conversion efficiency and signal strength ratio.

[0140] Moreover, the target beamforming vector is used to instruct the macro base station to send the content file to the user device and / or the content server according to the parameters corresponding to the target beamforming vector, and the target NOMA power allocation factor is used to instruct the content server to feedback the content file to the user device according to the parameters corresponding to the target NOMA power allocation factor.

[0141] Further, in the process of optimizing the beamforming vector and the NOMA power allocation factor, the central controller can define the stage of the macro base station sending the content file to the user device and the content server as the first stage, and define the stage of the content server sending the content file to the user device as the second stage.

[0142] Correspondingly, the central controller can obtain the first signal-to-interference plus noise ratio (SINR) corresponding to each user device in the first phase, as well as the energy collected by each content server, and the central controller can determine the power of the content server in the second phase according to the energy, and then determine the second SINR corresponding to each user device in the second phase according to the power of the content server in the second phase.

[0143] After that, the central controller can determine the expression of the sum rate of the user devices according to the first SINR and the second SINR, and calculate the expression of the sum rate of the user devices to obtain the target beamforming vector and the target NOMA power allocation factor.

[0144] Among them, the central controller can transform the non-convex problem into a convex problem in the form of second-order cone programming for solution for the expression of the sum rate of the user devices during the processes corresponding to the first phase and the second phase, so as to obtain the target beamforming vector and the target NOMA power allocation factor.

[0145] For example, referring to Figure 3 , Figure 3 is a schematic flowchart of a process for obtaining an update strategy provided by an embodiment of the present application, including the following steps:

[0146] Step 301: Construct a channel model and determine the transmission phase in which the user device is located according to the user device grouping protocol.

[0147] Step 302: Establish a multicast model and calculate the energy collected by the content server.

[0148] Specifically, collect and analyze the channel state information between the user device and the macro base station (or transmission node), including channel gain, path loss, multipath effect, etc. Based on the channel conditions, establish a model for signal transmission.

[0149] According to formula (1), use the received signal and noise power to calculate the SINR of each user device. Suppose there are k 1 user devices transmitting in the first phase and are divided into M multicast groups. When determining the content file obtained from the macro base station in the first phase, the SINR requested by the th user device in the th group is as shown in formula (4):

[0150] (4)

[0151] Among them, is the beamforming vector of the th group; is the channel vector from the macro base station to the user equipment ; is the additive white Gaussian noise.

[0152] Assume that the content server is the 0th user equipment. Then the energy collected in the second-stage transmission is as shown in Equation (5):

[0153] (5)

[0154] where represents the proportion of the signal strength for energy harvesting, is the power conversion efficiency of the content server. If , the content server does not perform content update; otherwise . Assume that the index of the content server is 0.

[0155] Determine the power obtained from the content server for the second-stage transmission according to Equation (5) as shown in Equation (6):

[0156] (6)

[0157] where is the size of the total cached files, is the cache consumption coefficient, is the time slot for energy harvesting. Assume that the time slots for energy harvesting and caching are the same, i.e., ;

[0158] Step 303: Establish the second-stage NOMA transmission model.

[0159] Specifically, determine the transmission power obtained from the content server according to Equation (6). The SINR requested by the th user equipment is as shown in Equation (7):

[0160] (7)

[0161] where is the power allocation factor of the th user equipment, is the power allocation factor of the th user equipment, is the second-stage transmission power, and the channel gains are sorted as , represents the channel gain between the content server and the th user equipment; is the set of requested user equipment; is the variance of the additive white Gaussian noise of the

[0162] Convert the SINR to the transmission rate of each user equipment according to the Shannon formula or other applicable rate formulas. Add up the transmission rates of all user equipments to obtain the expression of the sum rate of user equipments as shown in formula (8):

[0163] (8)

[0164] where is the transmission bandwidth in the first stage, is the transmission bandwidth in the second stage, is the number of user equipments served in the first stage, is the number of user equipments served in the second stage, is the number of multicast groups in the first stage, is the lowest Quality of Service (QoS) constraint required for the group of user equipments to receive information, and is the minimum QoS requirement for the NOMA transmission stage. is the minimum energy harvesting threshold of the content server, is the maximum transmit power of the macro base station.

[0165] Determine the variables to be optimized, such as the beamforming vector and the NOMA power allocation factor. Take the expression of the sum rate of user equipments as the objective function of the optimization problem, and the goal is to maximize this function. Add necessary constraints according to the requirements of the transmission technology and the limitations of system resources, such as the total transmit power limit, the value range of the power allocation factor, etc.

[0166] Step 304, convert the non-convex problem into a convex problem in the form of second-order cone programming for solution in the expression of the sum rate of user equipments under the two-stage content push and distribution model, and obtain the target beamforming vector and the target NOMA power allocation factor.

[0167] Specifically, select a suitable optimization method according to the characteristics and complexity of the optimization problem, such as convex optimization, non-convex optimization, heuristic algorithms, etc. In this embodiment, use the transformation methods of semidefinite relaxation, successive convex approximation, and geometric mean inequality to convert the non-convex problem into a convex problem in the form of second-order cone programming:

[0168] Let and to get and . Introduce slack variables and , and relax the rank-1 condition. Then for the th group, the The SINR requested by a user equipment, as shown in formula (9):

[0169] (9)

[0170] Formula (10) can be obtained from the AGM inequality:

[0171] (10)

[0172] Among them, , and are the values at the th iteration; , value;

[0173] Similarly, for assuming there is a slack variable that satisfies formula (11):

[0174] (11)

[0175] Among them, , and are the values at the th iteration; then maximizing the sum rate of the user equipment is transformed into as shown in formula (12): , value; then

[0176] (12)

[0177] Among them, is the beamforming vector of the mth group, is the QoS constraint introduced in the first stage, is the QoS constraint introduced in the second stage, is the power allocation factor of the th user equipment, is the transmission bandwidth in the first stage, is the transmission bandwidth in the second stage, is the number of user equipments served in the first stage, is the number of user equipments served in the second stage.

[0178] Moreover, , is the value at the th iteration, value, is the value at the th iteration, value, is the beamforming vector of the jth group, is from the macro base station to the user equipment The channel vector, is the additive white Gaussian noise, is the number of multicast groups in the first stage.

[0179] In addition, , is the value of the ith iteration, is the power allocation factor of the ith user equipment, is the value of the ith iteration; is the transmission power in the second stage, represents the channel gain between the content server and the th user equipment, is the additive white Gaussian noise.

[0180] Furthermore, is the minimum QoS constraint required for the th group of user equipment to receive information, is the minimum QoS requirement in the NOMA transmission stage, is the maximum transmit power of the macro base station, is the minimum energy harvesting threshold of the content server, is the energy collected by the content server during the second stage transmission when the content server is the 0th user equipment.

[0181] Use mathematical tools (such as the Lagrange multiplier method, gradient descent method, interior point method, etc.) to solve the optimization problem. Through the solution process, the target beamforming vector and the target NOMA power allocation factor are obtained. It should be noted that the variable to be optimized initially is the beamforming vector . First, the optimization problem is transformed and defined as an auxiliary variable, and the rank constraint condition of is relaxed. The non-convex problem is transformed into a solvable convex optimization problem by using the AGM inequality. After obtaining through convex optimization, the original beamforming vector needs to be restored. In this embodiment, if the rank of the beamforming matrix is equal to 1, then the optimal beamforming vector can be obtained through eigenvalue decomposition; conversely, if the rank of the beamforming matrix is not equal to 1, the Gaussian randomization method is used to obtain the optimal beamforming vector.

[0182] Through the above embodiments, the preset file update algorithm can effectively manage the cache content of the content server based on the cache utility function, optimize the utilization of storage resources, and at the same time meet the high-priority file requests of user equipment.

[0183] Step 208: The central controller sends a transmission policy to the macro base station and sends an update policy to at least one content server.

[0184] After generating the update policy and the transmission policy, the transmission policy can be sent to the macro base station, and the update policy can be sent to the content server, so that the macro base station can feedback the content file to the user equipment in the multicast group according to the transmission policy, and send the file to be updated to the content server. The content server can cache the received file to be updated according to the update policy and feedback the cached content file to the user equipment in at least one user equipment group.

[0185] It should be noted that in practical applications, the central controller can send the same or different transmission policies and update policies to multiple macro base stations and multiple content servers. The embodiments of the present application do not specifically limit the number of macro base stations and content servers, nor do they specifically limit whether the transmission policies and update policies are the same or different.

[0186] Step 209: The macro base station feedbacks the content file corresponding to the content identifier to each user equipment in the multicast group according to the transmission policy feedback by the central controller, and sends the file to be updated to the content server.

[0187] Corresponding to step 208, the macro base station can receive the transmission policy sent by the central controller, and based on the content identifier and device identifier carried in the transmission policy, combined with the device identifier and content identifier corresponding to each user equipment in the multicast group, feedback the content file corresponding to the content identifier to the user equipment.

[0188] Moreover, the macro base station can also send the corresponding file to be updated to each content server in a multicast manner according to the transmission policy, combined with the file to be updated corresponding to each content server, so that the content server can cache the received file to be updated, and thus can feedback it to the user equipment as a content file.

[0189] It should be noted that due to the limited transmission bandwidth, the content server can only process the update requirement of one file each time it is updated. Therefore, when the macro base station sends the content to be updated to the content server, it can also feedback the content file to each user equipment in the multicast group at the same time to ensure the continuity and efficiency of the service.

[0190] In addition, the macro base station can use orthogonal frequency division multiple access technology to feedback the content file to the user equipment on the allocated time-frequency resource block to avoid collisions and improve the stability and reliability of data transmission.

[0191] Step 210: The content server receives the update policy sent by the central controller.

[0192] Corresponding to step 208, the content server can also receive the update policy sent by the central controller, so that in subsequent steps, the content server can cache the files to be updated according to the update policy, and then can feedback the cached content files to the user device.

[0193] Step 211: The content server receives the files to be updated sent by at least one macro base station according to the files to be updated indicated by the update policy, and updates the cached content files and caches the files to be updated.

[0194] For each content server, after receiving the update policy, the content server can receive the content files that need to be cached by the content server according to the files to be updated indicated by the update policy, and delete some of the cached content files, so as to cache the received files to be updated.

[0195] Optionally, the content server can first determine the target storage space required for the files to be updated, obtain the deletion priority carried by the update policy, and then delete at least one cached content file in the content server according to the target storage space and the deletion priority, so as to receive the files to be updated sent by at least one macro base station and cache the files to be updated.

[0196] Among them, the deletion priority is used to represent the priority among the cached content files that have not been requested in the content server.

[0197] Specifically, the content server first determines the target storage space required for the files to be updated and obtains the deletion priority carried by the update policy, so as to delete at least one cached content file in the content server according to the target storage space and the deletion priority, and then can cache at least one file to be updated sent by the macro base station.

[0198] Among them, the content server can selectively delete one or more unrequested content files, and this deletion operation needs to ensure that the remaining space size after the content server deletes the content files is greater than or equal to the file size corresponding to the content file with the highest caching priority among the cached files.

[0199] Step 212: The content server sends the content files corresponding to each content identifier to the user device corresponding to each content identifier according to at least one content identifier included in the update policy.

[0200] Corresponding to step 211, after caching the files to be updated, the content server can, according to the update policy, send the content files matching the content identifiers corresponding to each user device within the coverage range of the content server to complete the interaction of the content files.

[0201] Among them, the process in which the content server feeds back the content file to the user equipment in this step 212 is similar to the process in which the macro base station feeds back the content file to the user equipment in step 209, and will not be elaborated here.

[0202] The embodiment of the present application also provides a variation curve of the cache file hit rate in the content server with respect to the size of the content server. Refer to Figure 4 , Figure 4 It is a schematic diagram of the variation curve of the cache file hit rate in the content server provided by the embodiment of the present application with respect to the size of the content server. As Figure 4 shown, as the capacity of the content server expands, its hit rate shows a corresponding upward trend. Specifically, a larger capacity means that the content server can accommodate and cache a wider range of file sets, thereby significantly enhancing the ability to satisfy the requests of user equipment, that is, improving the hit rate of user equipment requests. Compared with traditional schemes that only make cache decisions based on file popularity and ignore file size, this embodiment realizes more accurate cache content selection by comprehensively considering file popularity and size. This improved strategy enables this scheme to show a higher hit rate under the same capacity condition, thereby more effectively utilizing cache resources and enhancing the user experience.

[0203] This embodiment also provides a variation curve of the sum rate of the transmission part with respect to power. Refer to Figure 5 , Figure 5 It is a schematic diagram of the variation curve of the sum rate of the transmission part provided by the embodiment of the present application with respect to power. As Figure 5 shown, as the transmit power increases, the transmission quality is correspondingly enhanced, thereby promoting the growth of the sum rate of the user equipment. Compared with the scheme without the assistance of the content server, the scheme proposed in this embodiment shows obvious superiority. Specifically, by introducing the assistance of the content server, a significant improvement in data transmission efficiency is achieved, and the sum rate of the user equipment also increases significantly. This comparison result shows that the proposed scheme has significant advantages in improving transmission quality and user equipment performance, further verifying its feasibility and effectiveness in practical applications.

[0204] In summary, compared with the prior art, this embodiment has the following advantages:

[0205] 1. In this embodiment, by comprehensively considering the size and popularity of cached files, a cache utility function and a corresponding cache update algorithm are designed. This method can optimize the cache content according to the access frequency and size of files, thereby maximizing the cache hit rate.

[0206] 2. Based on user equipment grouping and file update policies, this embodiment establishes a two-stage sum-rate optimization problem aiming to maximize the rate of user equipment. Through user equipment grouping and transmission strategy design, the system can ensure that within different transmission stages, user equipment can obtain the best data transmission rate according to their own needs and network conditions.

[0207] In summary, by comprehensively considering multiple key factors of caching and content transmission, this embodiment achieves the dual maximization of cache hit rate and user equipment rate, provides an efficient and practical solution for the joint optimization of content update, push, and transmission, and improves data transmission efficiency and user experience.

[0208] The third embodiment of the present invention also provides a controller, which includes:

[0209] At least one processor; and a memory communicatively connected to the at least one processor; wherein, the memory stores instructions executable by the at least one processor, and when the instructions are executed by the at least one processor, the at least one processor can execute the joint optimization method for content update, push, and transmission in any of the foregoing embodiments.

[0210] The fourth embodiment of the present invention also provides a non-transitory computer-readable storage medium, which stores computer instructions for causing the computer to execute the joint optimization method for content update, push, and transmission in any of the foregoing embodiments.

[0211] The fifth embodiment of the present invention also provides a computer program product, which includes a computing program stored on a non-transitory computer-readable storage medium. The computer program includes program instructions, and when the program instructions are executed by a computer, the computer is caused to execute the joint optimization method for content update, push, and transmission in any of the foregoing embodiments.

[0212] The sixth embodiment of the present invention also provides a computer program, which includes program instructions, and when the program instructions are executed by a computer, the computer is caused to execute the joint optimization method for content update, push, and transmission in any of the foregoing embodiments.

[0213] Figure 6 A schematic diagram showing a method that can implement the embodiments of the present invention or a device 1000 that can implement the embodiments of the present invention is shown. In some embodiments, it may include more or fewer devices than shown. In some embodiments, it can be implemented using a single or multiple devices. In some embodiments, it can be implemented using cloud or distributed devices.

[0214] As Figure 6As shown, device 1000 includes a processor 1001, which can perform various appropriate operations and processes according to programs and / or data stored in a read-only memory (ROM) 1002 or programs and / or data loaded from a storage section 1008 into a random access memory (RAM) 1003. The processor 1001 can be a multi-core processor or can include multiple processors. In some embodiments, the processor 1001 can include a general-purpose main processor and one or more special co-processors, such as a central processing unit (CPU), a graphics processing unit (GPU), a neural network processing unit (NPU), a digital signal processing unit (DSP), and so on. In the RAM 1003, various programs and data required for the operation of the device 1000 are also stored. The processor 1001, the ROM 1002, and the RAM 1003 are connected to each other via a bus 1004. An input / output (I / O) interface 1005 is also connected to the bus 1004.

[0215] The above-mentioned processor and memory are jointly used to execute the programs stored in the memory, and when the programs are executed by a computer, they can implement the methods, steps, or functions described in the above embodiments.

[0216] The following components are connected to the I / O interface 1005: an input section 1006 including a keyboard, a mouse, a touch screen, etc.; an output section 1007 including, for example, a cathode ray tube (CRT), a liquid crystal display (LCD), etc. and a speaker, etc.; a storage section 1008 including a hard disk, etc.; and a communication section 1009 including a network interface card such as a LAN card, a modem, etc. The communication section 1009 performs communication processing via a network such as the Internet. A drive 1010 is also connected to the I / O interface 1005 as needed. A removable medium 1011, such as a magnetic disk, an optical disk, a magneto-optical disk, a semiconductor memory, etc., is installed on the drive 1010 as needed so that a computer program read from it can be installed into the storage section 1008 as needed. Figure 6 Only some components are schematically shown in, and it does not mean that the device 1000 only includes Figure 6 the components shown.

[0217] The systems, devices, modules, or units illustrated in the above embodiments can be implemented by a computer or its associated components. The computer can be, for example, a mobile terminal, a smart phone, a personal computer, a laptop computer, an in-vehicle human-machine interaction device, a personal digital assistant, a media player, a navigation device, a game console, a tablet computer, a wearable device, a smart TV, an Internet of Things system, a smart home, an industrial computer, a server, or a combination thereof.

[0218] Although not shown, in an embodiment of the present invention, a computer-readable storage medium is provided, on which a computer program / instructions are stored, and when the computer program / instructions are executed by a processor, the combined optimization method for content update, push, and transmission described in Embodiment 1 is implemented.

[0219] The storage medium in the embodiment of the present invention includes permanent and non-permanent, removable and non-removable articles that can store information by any method or technology. Examples of storage media include, but are not limited to, phase change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technologies, compact disc read-only memory (CD-ROM), digital versatile disc (DVD) or other optical storage, magnetic cassette tapes, magnetic disk storage or other magnetic storage devices, or any other non-transmission medium that can be used to store information accessible by a computing device.

[0220] Although not shown, an embodiment of the present invention further provides a computer program product, including: a computer program / instructions, and when the computer program / instructions are executed by a processor, the combined optimization method for content update, push, and transmission described in Embodiment 1 is implemented.

[0221] The methods, programs, systems, devices, etc. in the embodiments of the present invention can be executed or implemented in a single or multiple networked computers, and can also be practiced in a distributed computing environment. In the embodiments of this specification, in these distributed computing environments, tasks can be executed by remote processing devices connected through a communication network.

[0222] Those skilled in the art should understand that the embodiments of this specification can be provided as methods, systems, or computer program products. Therefore, those skilled in the art can think that the implementation of the functional modules / units or controllers and related method steps described in the above embodiments can be achieved in a software, hardware, or software / hardware combination manner.

[0223] Unless explicitly stated, the actions or steps of the methods and programs described according to the embodiments of the present invention do not necessarily have to be executed in a specific order and can still achieve the desired results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0224] In this document, multiple embodiments of the present invention are described. For the sake of brevity, the descriptions of the embodiments are not exhaustive, and features or parts that are the same or similar among the embodiments may be omitted. In this document, "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" mean applicable to at least one embodiment or example according to the present invention, rather than all embodiments. The above terms do not necessarily refer to the same embodiment or example. Without contradiction, those skilled in the art can combine and combine different embodiments or examples described in this specification and the features of different embodiments or examples.

[0225] The exemplary systems and methods of the present invention have been specifically shown and described with reference to the above embodiments, which are only examples of the best mode for implementing the systems and methods. Those skilled in the art can understand that various changes can be made to the embodiments of the systems and methods described herein when implementing the systems and / or methods without departing from the spirit and scope of the present invention defined in the appended claims.

Claims

1. A joint optimization method for content update, push and transmission, characterized in that A central controller applied to a wireless caching network, the wireless caching network including: the central controller, at least one macro base station, multiple user equipments, and at least one content server, the method including: Receiving content requests sent by multiple user equipments forwarded by any one of the macro base stations, the content requests being used to request feedback of content files to the user equipments; Grouping the multiple user equipments according to the content identifier and location information respectively corresponding to each content request, to obtain multiple user equipment groups and corresponding grouping information, the content identifier being used to indicate the content file requested by the user equipment, the location information being used to represent the geographical location of the user equipment, and the content identifiers corresponding to each user equipment in any one user equipment group being the same; For each content identifier corresponding to each user equipment group, generating a caching utility function according to the popularity and size factor of the content file indicated by the content identifier; Determining, according to the caching utility function and a preset file update algorithm, the to-be-updated files that need to be cached in the content server, the to-be-updated files being content files requested by the user equipments but not cached in the content server; Generating an update strategy according to the to-be-updated files, and generating a transmission strategy according to the channel parameters of the wireless caching network, the update strategy being used to instruct the content server to feedback the to-be-updated files to multiple user equipments, and the transmission strategy being used to instruct the macro base station to transmit the to-be-updated files to the user equipments and / or the content server; Sending the transmission strategy to the macro base station, so that the macro base station, according to the transmission strategy, feeds back content files corresponding to the content identifier to each user equipment in a multicast group, and sends the to-be-updated files to at least one content server, and each user equipment in the multicast group is located outside the transmission range of each content server; Sending the update strategy to at least one content server, so that each content server determines the target storage space required for the to-be-updated files, obtains the to-be-deleted priority carried by the update strategy, deletes at least one content file cached in the content server according to the target storage space and the to-be-deleted priority, receives the to-be-updated files sent by at least one macro base station, and caches the to-be-updated files, and for at least one content identifier included in the update strategy, sends the content file corresponding to the content identifier to the user equipment corresponding to the content identifier, the to-be-deleted priority being used to represent the priority among the content files that are not requested and cached in the content server; The generating a transmission strategy according to the channel parameters of the wireless caching network includes: Constructing a channel model, and determining the transmission stage in which the user equipment is according to the user equipment grouping protocol; Establishing a multicast model, and calculating the energy collected by the content server; Establishing a second-phase non-orthogonal multiple access NOMA transmission model; In the expressions of the user equipment and rate under the two-stage content push and distribution model, the non-convex problem is transformed into a convex problem in the form of second-order cone programming for solution, and the target beamforming vector and the target NOMA power allocation factor are obtained.

2. The joint optimization method for content update, push, and transmission according to claim 1, wherein Grouping the multiple user equipments according to the content identifiers and location information respectively corresponding to each content request to obtain multiple user equipment groups and corresponding grouping information, including: For each content request, obtaining the content identifier and the location information carried by the content request; Grouping the multiple user equipments according to the multiple content identifiers and the multiple location information to obtain multiple user equipment groups and corresponding grouping information.

3. The joint optimization method for content update, push, and transmission according to claim 2, characterized in that The grouping the multiple user equipments according to the multiple content identifiers and the multiple location information to obtain multiple user equipment groups and corresponding grouping information includes: Grouping at least one user equipment corresponding to the same content identifier into one user equipment group according to the multiple content identifiers; Determining whether each user equipment is within the transmission range of any content server according to each location information; For each user equipment, if the user equipment is within the transmission range of any content server, retaining the user equipment in the user equipment group to which it belongs; If the user equipment is outside the transmission range of each content server, adjusting the user equipment from the user equipment group to which it belongs to a multicast group; Generating the grouping information according to at least one user equipment group and the multicast group.

4. The joint optimization method for content update, push, and transmission according to claim 1, characterized in that Determining the files to be updated that need to be cached in the content server according to the cache utility function and a preset file update algorithm, including: For each content server, determining at least one target user equipment covered by the transmission range of the content server according to the location information corresponding to each content identifier; Determining at least one file to be cached corresponding to each target user equipment according to the content identifier corresponding to each target user equipment, where the file to be cached is a file requested by the target user equipment and not cached by the content server; Determining the cache priority of each file to be cached through the cache utility function; Selecting a preset number of the files to be cached as the files to be updated according to the cache priority of each file to be cached.

5. The joint optimization method for content update, push and transmission according to claim 1, characterized in that Generating a transmission strategy according to the channel parameters of the wireless cache network, including: Obtaining a transmission rate according to the channel parameters, where the channel parameters include: channel state, the maximum transmission power of the macro base station, user receiving quality of service constraints, energy conversion efficiency, and signal strength ratio; Optimize the beamforming vector and the NOMA power allocation factor according to the transmission rate to obtain the target beamforming vector and the target NOMA power allocation factor. The target beamforming vector is used to instruct the macro base station to send the content file to the user equipment and / or the content server according to the parameters corresponding to the target beamforming vector. The target NOMA power allocation factor is used to instruct the content server to feedback the content file to the user equipment according to the parameters corresponding to the target NOMA power allocation factor. Obtain the target transmission rate according to the target beamforming vector and the target NOMA power allocation factor. Generate the transmission strategy according to the target beamforming vector, the target NOMA power allocation factor and the target transmission rate.

6. The joint optimization method for content update, push, and transmission according to claim 5, wherein The optimizing the beamforming vector and the NOMA power allocation factor according to the transmission rate to obtain the target beamforming vector and the target NOMA power allocation factor includes: Obtain the first SINR corresponding to each user equipment and the energy collected by each content server in the first phase. The first phase is the phase when the macro base station sends the content file to the user equipment and the content server. Determine the power of the content server in the second phase according to the energy. The second phase is the phase when the content server sends the content file to the user equipment. Determine the second SINR corresponding to each user equipment in the second phase according to the power of the content server in the second phase. Determine the expression of the sum rate of the user equipment according to the first SINR and the second SINR. Calculate the expression of the sum rate of the user equipment to obtain the target beamforming vector and the target NOMA power allocation factor.

7. A wireless caching network, characterized in that, The wireless caching network includes: a central controller, at least one macro base station, multiple user equipments and at least one content server. The macro base station is used to receive content requests sent by multiple user equipments. The content requests are used to request content files to be fed back to the user equipments. The macro base station is also used to forward the content requests to the central controller. The central controller is used to receive the content requests sent by any one of the macro base stations. The central controller is also used to group multiple user equipments according to the content identifier and location information respectively corresponding to each content request to obtain multiple user equipment groups and corresponding grouping information. The content identifier is used to indicate the content file requested by the user equipment. The content identifiers corresponding to each user equipment group are the same. The location information is used to represent the geographical location of the user equipment. For each content identifier corresponding to each grouping information, the central controller is also used to generate a caching utility function according to the popularity and size factor of the content file indicated by the content identifier. The central controller is further configured to determine, according to the cache utility function and a preset file update algorithm, the files to be updated that need to be cached in the content server, where the files to be updated are content files requested by the user equipment but not cached in the content server; The central controller is further configured to generate an update policy according to the files to be updated, and generate a transmission policy according to the channel parameters of the wireless caching network, where the update policy is used to instruct the content server to feed back the cached files to be updated to a plurality of the user equipment, and the transmission policy is used to instruct the macro base station to transmit the files to be updated to the user equipment and / or the content server; The central controller is further configured to send the transmission policy to the macro base station, and send the update policy to at least one of the content servers; The macro base station is further configured to, according to the transmission policy fed back by the central controller, feed back the content files corresponding to the content identifiers to each of the user equipment in the multicast group, and send the files to be updated to the content server, where each of the user equipment in the multicast group is outside the transmission range of each of the content servers; The content server is configured to receive the update policy sent by the central controller and determine the target storage space required for the files to be updated; The content server is further configured to obtain the deletion priority carried by the update policy, where the deletion priority is used to represent the priority among the content files that are not requested and cached in the content server; The content server is further configured to delete at least one of the content files cached in the content server according to the target storage space and the deletion priority; The content server is further configured to receive the files to be updated sent by at least one of the macro base stations and cache the files to be updated; The content server is further configured to send the content files corresponding to each content identifier to the user equipment corresponding to each content identifier according to at least one content identifier included in the update policy; Generating the transmission policy according to the channel parameters of the wireless caching network includes: Constructing a channel model and determining the transmission stage where the user equipment is located according to the user equipment grouping protocol; Establishing a multicast model and calculating the energy collected by the content server; Establishing a second-stage NOMA transmission model; In the expression of the sum rate of the user equipment under the two-stage content push and distribution model, converting the non-convex problem into a convex problem in the form of second-order cone programming for solution to obtain the target beamforming vector and the target NOMA power allocation factor.

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