Time delay minimization method for block caching and cooperative transmission based on clustered D2D communication

Abstract

The invention discloses a time delay minimization method for block caching and cooperative transmission based on clustered D2D communication, which belongs to the technical field of wireless communication, adopts an OMA or NOMA transmission mechanism, and comprises the following steps of: partitioning popular content and caching the popular content into a plurality of different devices in the same cluster; when a user makes a request, different content blocks are sent to the request user at the same time through the multiple different devices, and the average speed and average time delay of block content transmission are deduced; based on the average rate and the average time delay, constructing a maximum transmission time delay minimization problem; and respectively formulating an optimal bandwidth allocation scheme and a transmitting power optimization scheme under the OMA transmission mechanism and the NOMA transmission mechanism based on the maximum transmission delay minimization problem. The invention solves the problems of low network resource utilization rate and poor transmission performance in the prior art.

Description

Technical Field

[0001] The present invention relates to a method for minimizing the delay of block caching and cooperative transmission based on clustered D2D communication, belonging to the field of wireless communication technology. Background Art

[0002] The popularization of smart mobile devices and the wide application of social media have led to an explosive growth in mobile data traffic, posing a huge challenge to wireless cellular networks. Edge caching technology can pre-cache popular content, including pictures, videos, etc., in network edge nodes such as small base stations and edge servers, reducing the repeated transmission of data and alleviating the traffic congestion problem of the backhaul link. Device-to-device (D2D) communication is one of the key technologies of the fifth-generation mobile communication, allowing direct communication between adjacent devices and effectively reducing the traffic burden on the cellular network. Combining caching with D2D communication can not only meet user needs through a shorter communication path and improve the user service experience, but also be an effective solution to cope with the rapid growth of mobile data traffic.

[0003] However, D2D devices usually have a small cache capacity and limited transmission power, and storing and sending large files pose certain challenges to the devices. Due to the limited cache space of the devices, caching the entire large file will cause a large capacity pressure, and when sharing the entire file with other users, it will increase the communication load of the devices. In addition, in the scenario of a single device sending the entire file, there is a lack of reasonable optimization of the cooperative transmission link resources, and resource allocation strategies such as bandwidth allocation and transmission power adjustment are not fully utilized to improve the utilization rate of network resources and transmission performance, resulting in low network resource utilization rate and poor transmission performance. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for minimizing the delay of block caching and cooperative transmission based on clustered D2D communication, by dividing popular content into blocks and caching them into different devices respectively, and using multiple devices to send the file to the requesting user through cooperative transmission, so as to solve the problems of low network resource utilization rate and poor transmission performance in the prior art.

[0005] To solve the above technical problems, the present invention is implemented by adopting the following technical solutions:

[0006] In a first aspect, the present invention provides a method for minimizing the delay of block caching and cooperative transmission based on clustered D2D communication, adopting the OMA transmission mechanism, including:

[0007] Obtain popular content;

[0008] Divide the popular content into blocks and cache them into several different devices within the same cluster;

[0009] When a user makes a request, use the several different devices to simultaneously send different content chunks to the requesting user by adopting the OMA transmission mechanism;

[0010] Based on the OMA transmission mechanism, deduce the average rate and average delay of the transmission of the content chunks;

[0011] Based on the average rate and average delay, with the total bandwidth as a constraint, construct a problem of minimizing the maximum transmission delay under the OMA transmission mechanism;

[0012] Based on the problem of minimizing the maximum transmission delay under the OMA transmission mechanism, prove the necessary and sufficient conditions for the existence of the optimal solution to the bandwidth allocation problem, and obtain the closed-form solution of the optimal bandwidth allocation according to the necessary and sufficient conditions for the existence of the optimal solution to the bandwidth allocation problem.

[0013] Furthermore, based on the OMA transmission mechanism, deduce the average rate and average delay of the transmission of the content chunks, including:

[0014] Based on the OMA transmission mechanism, use the theory of stochastic geometry to deduce the expectation of the transmission rate of the content chunks, and obtain the average rate of the transmission of the content chunks;

[0015] Based on the average rate of the transmission of the content chunks, use Jensen's inequality to obtain the average delay of the transmission of the content chunks.

[0016] Furthermore, the average rate of the transmission of the content chunks is expressed as:

[0017] R ¯ i o =  [ R i o ] =  [ l o g 2 ( 1 + S I R i o ) ] ;

[0018] In the formula, represents the average rate of the th content chunk under the OMA transmission mechanism, E [ R i o ] represents the expectation of the transmission rate of the th content chunk, represents the logarithmic function with base 2, represents the signal-to-interference ratio of the requesting user receiving the th content chunk under the OMA transmission mechanism;

[0019] The average delay of the content chunks is expressed as:

[0020] L ¯ i o =  [ S K 0 W i R i o ] ≥ S K 0 W i  [ R i o ] = S K 0 W i R ¯ i o , ;

[0021] In the formula, represents the average delay of transmitting the th content chunk under the OMA transmission mechanism, Indicates the size of the content, Indicates the number of chunked contents, Indicates the size of the chunked content, Indicates sending the bandwidth used for the chunked content.

[0022] Furthermore, the problem of minimizing the maximum transmission delay under the OMA transmission mechanism is expressed as:

[0023] , , ;

[0024] In the formula, Indicates the number of chunked contents, is the set of bandwidths allocated for the transmission of Indicates using the OMA transmission mechanism to send the maximum transmission delay of chunked contents, where Indicates the average delay of sending the first chunked content under the OMA transmission mechanism, Indicates the average delay of sending the chunked content under the OMA transmission mechanism, Indicates the bandwidth allocation problem aiming at minimizing the maximum delay, is used to represent the constraint condition, where Indicates the bandwidth used for the transmission of the chunked content, Indicates the total available bandwidth.

[0025] Furthermore, the necessary and sufficient condition for the existence of the optimal solution to the bandwidth allocation problem is that the average delays of all chunked content transmissions are equal, where the closed-form solution of the optimal bandwidth allocation is expressed as:

[0026] , ;

[0027] In the formula, represents the closed-form solution of the optimal bandwidth allocation for the chunked content, that is, the bandwidth used for the transmission of the chunked content, Indicates the average rate of transmitting the chunked content under the OMA transmission mechanism, Indicates the average rate of transmitting the chunked content under the OMA transmission mechanism.

[0028] In a second aspect, the present invention further provides a method for minimizing the delay of chunk caching and cooperative transmission based on clustered D2D communication, adopting the NOMA transmission mechanism, including:

[0029] Obtain popular content;

[0030] Chunk the popular content and cache it in several different devices within the same cluster;

[0031] When a user makes a request, use the several different devices to simultaneously send different content chunks to the requesting user by adopting the NOMA transmission mechanism;

[0032] Based on the NOMA transmission mechanism, deduce the average rate and average delay of the transmission of the chunked content;

[0033] Based on the average rate and average delay, and with the maximum transmission power of the device as a constraint, construct a problem of minimizing the maximum transmission delay under the NOMA transmission mechanism;

[0034] Based on the problem of minimizing the maximum transmission delay under the NOMA transmission mechanism, use the particle swarm optimization algorithm to optimize the transmission power of the devices for cooperative transmission, and formulate a transmission power optimization scheme according to the optimization results.

[0035] Furthermore, based on the NOMA transmission mechanism, deducing the average rate and average delay of the transmission of the chunked content includes:

[0036] Based on the NOMA transmission mechanism, use the stochastic geometry theory to deduce the expectation of the transmission rate of the chunked content, and obtain the average rate of the transmission of the chunked content;

[0037] Use Jensen's inequality to obtain the average delay of the transmission of the chunked content according to the average rate of the transmission of the chunked content.

[0038] Furthermore, the average rate of the transmission of the chunked content is expressed as:

[0039] R ¯ i s =  [ R i s ] =  [ l o g 2 ( 1 + S I R i s ) ] ;

[0040] In the formula, represents the average rate of the th chunked content under the NOMA transmission mechanism, E [ R i s ] represents the expectation of the transmission rate of the th chunked content, is the logarithm function with base 2, represents the signal-to-interference-plus-noise ratio of the requesting user receiving the th chunked content under the NOMA transmission mechanism;

[0041] ​The average delay of the chunk content transmission is expressed as:

[0042] , ;

[0043] In the formula, represents the average delay of the -th chunk content transmission under the NOMA transmission mechanism, represents the size of the content, represents the number of chunk contents, represents the size of the chunk content, represents the total available bandwidth, represents the average rate of the -th chunk content transmission under the NOMA transmission mechanism.

[0044] Furthermore, the problem of minimizing the maximum transmission delay under the NOMA transmission mechanism is expressed as:

[0045] , , , ;

[0046] In the formula, represents the number of chunk contents, is the set of transmit powers used to send the chunk contents, represents the maximum transmission delay of sending the chunk contents using the NOMA transmission mechanism, where represents the average delay of the first chunk content transmission under the NOMA transmission mechanism, represents the average delay of the -th chunk content transmission under the NOMA transmission mechanism, is the transmit power optimization problem aiming at minimizing the maximum delay, is used to represent the constraint conditions. The transmit power of each device when sending the content chunk is a positive number and cannot exceed the maximum transmit power of the device, where represents the power of sending the -th chunk content under the NOMA transmission mechanism, represents the maximum transmit power of the device.

[0047] Furthermore, based on the problem of minimizing the maximum transmission delay under the NOMA transmission mechanism, the transmit powers of the devices for cooperative transmission are optimized using the particle swarm algorithm, including:

[0048] Randomly initialize the positions and velocities of the particles in the particle swarm algorithm;

[0049] Based on the maximum value of the average delay of the segmented content transmission under the NOMA transmission mechanism, an objective function is established with the goal of minimizing the maximum transmission delay. Among them, the maximum value of the average delay of the segmented content transmission under the NOMA transmission mechanism is expressed as ;

[0050] Based on the position of the particle, the fitness value is calculated according to the objective function;

[0051] Update the historical optimal fitness value and position of the particle individual, as well as the historical optimal fitness value and position of the population according to the fitness value;

[0052] Repeat the following steps until the preset condition or the maximum number of iterations is reached, and output the optimal fitness value and the optimal position:

[0053] According to Update the velocity of the particle, where represents the particle position, represents the inertia weight, and represent the cognitive learning rate constant and the social learning rate constant respectively, and respectively represent [ 0 , 1 ] random numbers within and represent the historical optimal position of the particle individual and the historical optimal position of the population respectively;

[0054] According to Update the position of the particle, where represents the velocity of the particle;

[0055] Calculate the fitness value based on the updated particle position;

[0056] Update the historical optimal fitness value and position of the particle individual, as well as the historical optimal fitness value and position of the population based on the calculated fitness value.

[0057] Compared with the prior art, the beneficial effects achieved by the present invention:

[0058] 1. The present invention divides popular content into chunks and caches them in different devices within the same cluster. When a user requests, these devices can simultaneously use the OMA transmission mechanism to send different content chunks, effectively utilizing the locality of D2D communication and the collaborative ability between devices, significantly improving the parallelism of content transmission, thereby reducing the total delay for the user to obtain the required content. The present invention also accurately derives the average rate and average delay of the chunked content, constructs the maximum transmission delay minimization problem based on this, combines the optimal solution of bandwidth allocation, realizes the efficient allocation of resources, ensures the fast transmission of content, further optimizes the usage efficiency of network bandwidth, reduces the delay, alleviates the limitation of the limited cache capacity of devices, reduces the communication load, improves the transmission efficiency, and solves the problems of low network resource utilization and poor transmission performance in the prior art.

[0059] 2. The present invention also, based on the characteristics of the NOMA transmission mechanism, allows the simultaneous transmission of data of multiple users within the same frequency band, thereby significantly enhancing the capacity and flexibility of the network. Through chunk caching and collaborative transmission, while alleviating the cache and transmission pressure of devices, it can effectively manage resources and reduce the delay. At the same time, by deriving the average rate and average delay based on NOMA and constructing the maximum transmission delay minimization problem, the present invention can make full use of the non-orthogonal characteristics of NOMA, improve the spectrum efficiency, and further reduce the delay of content transmission. The present invention also optimizes the transmit power of collaborative transmission devices by using the particle swarm algorithm, which helps to minimize the transmission delay under the condition of meeting the maximum transmit power constraint of devices, improve the utilization rate of network resources, and enhance the transmission performance.

[0060] 3. The present invention considers two transmission mechanisms, OMA and NOMA. The OMA transmission mechanism avoids intra-cluster interference through bandwidth allocation, and the NOMA transmission mechanism improves the spectrum efficiency by sharing bandwidth. The present invention also optimizes the bandwidth allocation under the OMA transmission mechanism and the transmit power under the NOMA transmission mechanism with the goal of minimizing the maximum transmission delay, while rationally using resource allocation and enhancing the transmission performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Figure 1 It is a schematic flowchart of the method for minimizing the delay of chunk caching and collaborative transmission based on clustered D2D communication provided by an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0062] The technical solution of the present invention will be described in detail below through the drawings and specific embodiments. It should be understood that the specific features in the embodiments of the present invention and the embodiments are detailed descriptions of the technical solution of the present invention, rather than limitations on the technical solution of the present invention. Without conflict, the technical features in the embodiments of the present invention and the embodiments can be combined with each other.

[0063] The term "and / or" is merely a description of the association relationship between associated objects, indicating that there can be three relationships. For example, A and / or B can represent three situations: A exists alone, A and B exist simultaneously, and B exists alone. Additionally, the character " / " generally indicates that the associated objects before and after are in an "or" relationship.

[0064] Embodiment 1

[0065] As Figure 1 shown, this embodiment introduces a method for minimizing the delay of chunk caching and cooperative transmission based on clustered D2D communication.

[0066] In some embodiments, the OMA transmission mechanism is adopted, including:

[0067] Step 1: Obtain popular content, divide the popular content into chunks, and cache them in several different devices within the same cluster.

[0068] The popular content mentioned in the present invention includes content that is frequently requested by users. By dividing the popular content into chunks and caching them in different devices respectively, the caching pressure on the devices is alleviated.

[0069] Step 2: When a user issues a request, use the several different devices to simultaneously send different content chunks to the requesting user by adopting the OMA transmission mechanism.

[0070] In the present invention, by using the OMA transmission mechanism to simultaneously send different content chunks to the requesting user, orthogonal frequency resources are used for different transmission links, reducing interference.

[0071] Step 3: Based on the OMA transmission mechanism, deduce the average rate and average delay of the chunked content.

[0072] In the present invention, the average rate and average delay of the chunked content transmission under the OMA transmission mechanism are deduced through stochastic geometry theory.

[0073] Step 4: Based on the average rate and average delay, with the total bandwidth as a constraint, construct a problem of minimizing the maximum transmission delay under the OMA transmission mechanism.

[0074] In the present invention, by constructing a problem of minimizing the maximum transmission delay under the OMA transmission mechanism with a finite total bandwidth as a constraint, the transmission performance is improved by formulating a suitable bandwidth allocation scheme.

[0075] Step 5: Based on the problem of minimizing the maximum transmission delay under the OMA transmission mechanism, prove the necessary and sufficient conditions for the existence of the optimal solution to the bandwidth allocation problem, and obtain the closed-form solution of the optimal bandwidth allocation according to the necessary and sufficient conditions for the existence of the optimal solution to the bandwidth allocation problem.

[0076] The present invention proves the necessary and sufficient conditions for the existence of the optimal solution to the bandwidth allocation problem and obtains the closed-form solution of the optimal bandwidth allocation. This optimal bandwidth allocation scheme can improve the transmission performance while making full use of resources.

[0077] In some embodiments, the NOMA transmission mechanism is adopted, including:

[0078] Step 1: Obtain popular content, divide the popular content into chunks and cache them in several different devices within the same cluster.

[0079] The popular content mentioned in the present invention includes the content that users request frequently. By dividing the popular content into chunks and caching them in different devices respectively, the caching pressure of the devices is alleviated.

[0080] Step 2: When a user issues a request, use the several different devices to simultaneously send different content chunks to the requesting user by adopting the NOMA transmission mechanism.

[0081] The present invention simultaneously sends different content chunks to the requesting user by using the NOMA transmission mechanism, allowing different transmission links to use the same frequency resources and achieving higher resource utilization.

[0082] Step 3: Based on the NOMA transmission mechanism, deduce the average rate and average delay of the chunked content.

[0083] The present invention deduces the average rate and average delay of the chunked content transmission under the NOMA transmission mechanism through stochastic geometry theory.

[0084] Step 4: Based on the average rate and average delay, with the maximum transmit power of the device as a constraint, construct the problem of minimizing the maximum transmission delay under the NOMA transmission mechanism.

[0085] The present invention constructs the problem of minimizing the maximum transmission delay under the NOMA transmission mechanism with the maximum transmit power of the device as a constraint, and improves the transmission performance by formulating a suitable transmit power scheme.

[0086] Step 5: Based on the problem of minimizing the maximum transmission delay under the NOMA transmission mechanism, use the particle swarm optimization algorithm to optimize the transmit power of the devices for cooperative transmission, and formulate a transmit power optimization scheme according to the optimization results.

[0087] The present invention optimizes the transmit power of the devices for cooperative transmission under the NOMA transmission mechanism through the particle swarm optimization algorithm, and formulates a transmit power optimization scheme according to the optimization results. This optimization scheme not only improves the resource utilization but also enhances the transmission performance.

[0088] Embodiment 2

[0089] Based on the same inventive concept as in Embodiment 1, this embodiment introduces the specific implementation steps of a method for minimizing the delay of block caching and cooperative transmission based on clustered D2D communication, including:

[0090] In some embodiments, an OMA transmission mechanism is adopted, including:

[0091] Step 1: Obtain popular content, divide the popular content into blocks and cache them in several different devices within the same cluster.

[0092] The popular content mentioned in the present invention includes content that is frequently requested by users.

[0093] Step 2: When a user makes a request, use the several different devices to simultaneously send different content blocks to the requesting user by adopting the OMA transmission mechanism.

[0094] Step 3: Based on the OMA transmission mechanism, deduce the average rate and average delay of the transmission of the block content.

[0095] In some embodiments, based on the OMA transmission mechanism, deduce the average rate and average delay of the transmission of the block content, including:

[0096] Based on the OMA transmission mechanism, use the theory of stochastic geometry to deduce the expectation of the transmission rate of the block content, and obtain the average rate of the block content.

[0097] In this embodiment, the average rate of the transmission of the block content is expressed as:

[0098] R ¯ i o =  [ R i o ] =  [ l o g 2 ( 1 + S I R i o ) ] ;

[0099] In the formula, represents the average rate of the th block content under the OMA transmission mechanism, E [ R i o ] represents the expectation of the transmission rate of the th block content, represents the logarithmic function with base 2, represents the signal-to-interference ratio at which the requesting user receives the th block content under the OMA transmission mechanism.

[0100] Among them, the th block content is sent by the device that is the th closest to the requesting user. Therefore, affected by the spatial distribution and fading distribution of the devices, it is a random variable, is the transmission rate of the content block and is also a random variable.

[0101] Using Jensen's inequality, the average delay of the segmented content transmission is obtained based on the average rate of the segmented content transmission.

[0102] In this embodiment, the average delay of the segmented content transmission is expressed as:

[0103] L ¯ i o =  [ S K 0 W i R i o ] ≥ S K 0 W i  [ R i o ] = S K 0 W i R ¯ i o , ;

[0104] In the formula, represents the average delay of transmitting the th segmented content under the OMA transmission mechanism, represents the size of the content, represents the number of segmented contents, represents the size of the segmented content, represents the bandwidth used to send the th segmented content.

[0105] In this embodiment, the average delay for the user to obtain the requested content is expressed as:

[0106]  [ m a x { S K 0 W 1 R 1 o , … , S K 0 W K 0 R K 0 o } ]

[0107] ≥ m a x {  [ S K 0 W 1 R 1 o ] , … ,  [ S K 0 W K 0 R K 0 o ] }

[0108] ≥ m a x { S K 0 W 1  [ R 1 o ] , … , S K 0 W K 0  [ R K 0 o ] }

[0109] ;

[0110] In the formula, represents the bandwidth used to send the first segmented content, represents the bandwidth used to send the th segmented content.

[0111] Step 4: Based on the average rate and the average delay, with the total bandwidth as a constraint, construct a problem of minimizing the maximum transmission delay under the OMA transmission mechanism.

[0112] In this embodiment, the problem of minimizing the maximum transmission delay under the OMA transmission mechanism is expressed as:

[0113] , , ;

[0114] In the formula, represents the number of segmented contents, is The set of bandwidths allocated for the transmission of each chunk of content Indicates the use of the OMA transmission mechanism to send The maximum transmission delay of each chunk of content. Among them, Indicates the average delay of sending the first chunk of content under the OMA transmission mechanism, Indicates the average delay of sending the chunk of content. Indicates the bandwidth allocation problem with the goal of minimizing the maximum delay. Used to represent the constraint conditions. The bandwidth used for the transmission of each chunk of content must be a positive number, and the total bandwidth used for the transmission of all chunks of content cannot exceed the total available bandwidth. Among them Indicates the bandwidth used for the transmission of the chunk of content,

[0115] Step 5: Based on the problem of minimizing the maximum transmission delay under the OMA transmission mechanism, prove the necessary and sufficient conditions for the existence of the optimal solution of the bandwidth allocation problem, and obtain the closed-form solution of the optimal bandwidth allocation according to the necessary and sufficient conditions for the existence of the optimal solution of the bandwidth allocation problem.

[0116] In some embodiments, the necessary and sufficient condition for the existence of the optimal solution of the bandwidth allocation problem is that the average delays of all chunks of content are equal.

[0117] In this embodiment, the closed-form solution of the optimal bandwidth allocation is expressed as:

[0118] , ;

[0119] In the formula, represents the closed-form solution of the optimal bandwidth allocation of the chunk of content, that is, the bandwidth used for the transmission of the chunk of content, represents the average rate of transmitting the chunk of content under the OMA transmission mechanism, represents the average rate of transmitting the chunk of content under the OMA transmission mechanism.

[0120] In some embodiments, the NOMA transmission mechanism is adopted, including:

[0121] Step 1: Obtain popular content, divide the popular content into chunks and cache them in several different devices within the same cluster.

[0122] Step 2: When the user makes a request, use the several different devices to simultaneously send different content chunks to the requesting user by adopting the NOMA transmission mechanism.

[0123] Step 3: Based on the NOMA transmission mechanism, deduce the average rate and average delay of the chunked content transmission.

[0124] In some embodiments, based on the NOMA transmission mechanism, deducing the average rate and average delay of the chunked content transmission includes:

[0125] Based on the NOMA transmission mechanism, use the stochastic geometry theory to deduce the expectation of the transmission rate of the chunked content, and obtain the average rate of the chunked content transmission.

[0126] In this embodiment, the average rate of the chunked content transmission is expressed as:

[0127] R ¯ i s =  [ R i s ] =  [ l o g 2 ( 1 + S I R i s ) ] ;

[0128] In the formula, represents the average rate of the th chunked content under the NOMA transmission mechanism, E [ R i s ] represents the th chunked content transmission rate expectation of, represents the logarithmic function with base 2, represents the signal-to-interference-plus-noise ratio of the requesting user receiving the

[0129] Among them, the th chunked content is sent by the device that is the th closest to the requesting user. Therefore affected by the device spatial distribution and fading distribution, is a random variable, is the transmission rate of the content chunk and is also a random variable,  [ ⋅ ] represents taking the expectation of the random variable.

[0130] Use Jensen's inequality to obtain the average delay of the chunked content transmission according to the average rate of the chunked content transmission.

[0131] In this embodiment, the average delay of the chunked content transmission is expressed as:

[0132] , ;

[0133] In the formula, Denote the average delay of transmitting the th chunk of content under the NOMA transmission mechanism. Denote the size of the content. Denote the number of chunks of content. Denote the size of a chunk of content. Denote the total available bandwidth. Denote the average rate of transmitting the th chunk of content under the NOMA transmission mechanism. Step 4: Based on the average rate and average delay, with the maximum transmit power of the device as a constraint, construct a problem of minimizing the maximum transmission delay under the NOMA transmission mechanism.

[0134] In this embodiment, the problem of minimizing the maximum transmission delay under the NOMA transmission mechanism is expressed as:

[0135] , , , ;

[0136] In the formula, Denote the number of chunks of content. is the set of transmit powers used to send chunks of content. Denote the maximum transmission delay of sending chunks of content using the NOMA transmission mechanism, where Denote the average delay of transmitting the first chunk of content under the NOMA transmission mechanism. Denote the average delay of transmitting the th chunk of content under the NOMA transmission mechanism. is an optimization problem of transmit power aiming at minimizing the maximum delay. is used to represent the constraint conditions. The transmit power of each device when sending content chunks is a positive number and cannot exceed the maximum transmit power of the device , where Denote the power of sending the th chunk of content under the NOMA transmission mechanism. Denote the maximum transmit power of the device.

[0137] Step 5: Based on the problem of minimizing the maximum transmission delay under the NOMA transmission mechanism, use the particle swarm optimization algorithm to optimize the transmit power of the devices for cooperative transmission, and formulate a transmit power optimization scheme according to the optimization results.

[0138] In some embodiments, based on the problem of minimizing the maximum transmission delay under the NOMA transmission mechanism, using the particle swarm optimization algorithm to optimize the transmit power of the devices for cooperative transmission includes:

[0139] Randomly initialize the positions and velocities of the particles in the particle swarm algorithm;

[0140] Based on the maximum value of the average delay of the block content transmission under the NOMA transmission mechanism, establish an objective function with the goal of minimizing the maximum transmission delay. Among them, the maximum value of the average delay of the block content transmission under the NOMA transmission mechanism is expressed as ;

[0141] Based on the positions of the particles, calculate the fitness values according to the objective function;

[0142] Update the individual historical best fitness values and positions of the particles, as well as the group historical best fitness values and positions according to the fitness values;

[0143] Repeat the following steps until the preset conditions are met or the maximum number of iterations is reached, and output the optimal fitness value and the optimal position:

[0144] According to Update the velocities of the particles, where represents the particle position, represents the inertia weight, and represent the cognitive learning rate constant and the social learning rate constant respectively, and represent respectively [ 0 , 1 ] random numbers within and represent the individual historical best position of the particle and the group historical best position respectively;

[0145] According to Update the positions of the particles, where represents the velocity of the particle;

[0146] Calculate the fitness values based on the updated particle positions;

[0147] Update the individual historical best fitness values and positions of the particles, as well as the group historical best fitness values and positions based on the calculated fitness values.

[0148] Example 3

[0149] Based on the same inventive concept as other embodiments, this embodiment introduces a computer-readable storage medium, on which computer instructions are stored. It is characterized in that when the computer instructions are executed by a processor, the steps of the method of the above-mentioned Embodiment 1 or 2 are implemented.

[0150] Example 4

[0151] Based on the same inventive concept as other embodiments, the present invention also provides a computer program product, including computer instructions, characterized in that when the computer instructions are executed by a processor, the steps of the method in the above-mentioned Embodiment 1 or 2 are implemented.

[0152] In summary of the above embodiments, the present invention divides popular content into chunks and caches them in different devices within the same cluster. When a user requests, these devices can simultaneously use the OMA transmission mechanism to send different content chunks, effectively utilizing the locality of D2D communication and the collaborative ability between devices, significantly improving the parallelism of content transmission, thereby reducing the total delay for the user to obtain the required content. The present invention also precisely derives the average rate and average delay of the chunked content, constructs the maximum transmission delay minimization problem based on this, combines the optimal solution of bandwidth allocation, realizes the efficient allocation of resources, ensures the fast transmission of content, optimizes the usage efficiency of network bandwidth, further reduces the delay, alleviates the limitation of the limited cache capacity of devices, reduces the communication load, improves the transmission efficiency, and solves the problems of low network resource utilization rate and poor transmission performance in the prior art.

[0153] Based on the characteristics of the NOMA transmission mechanism, the present invention allows the simultaneous transmission of data of multiple users within the same frequency band, thus significantly enhancing the capacity and flexibility of the network. Through chunk caching and collaborative transmission, while alleviating the caching and transmission pressure of devices, resources can be effectively managed, the delay can be reduced. At the same time, by deriving the average rate and average delay based on NOMA and constructing the maximum transmission delay minimization problem, the present invention can make full use of the non-orthogonal characteristics of NOMA to improve the spectral efficiency and further reduce the delay of content transmission. The present invention also optimizes the transmission power of collaborative transmission devices by using the particle swarm algorithm, which helps to minimize the transmission delay under the condition of satisfying the maximum transmission power constraint of the device, improve the utilization rate of network resources, and enhance the transmission performance. The present invention considers two transmission mechanisms, OMA and NOMA. The OMA transmission mechanism avoids intra-cluster interference through bandwidth allocation, and the NOMA transmission mechanism improves the spectral efficiency by sharing bandwidth. The present invention also optimizes the bandwidth allocation under the OMA transmission mechanism and the transmission power under the NOMA transmission mechanism with the goal of minimizing the maximum transmission delay, while rationally using resource allocation, improving the transmission performance.

[0154] Those skilled in the art should understand that the embodiments of the present invention can be provided as a method, a system, or a computer program product. Therefore, the present invention can take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present invention can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0155] The present invention is described with reference to the flowcharts and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the present invention. It should be understood that each flow and / or block in the flowcharts and / or block diagrams, as well as the combination of flows and / or blocks in the flowcharts and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to the processors of general-purpose computers, special-purpose computers, embedded processors, or other programmable data processing devices to generate a machine, such that the instructions executed by the processors of the computer or other programmable data processing devices produce means for implementing the functions specified in one flow Figure 1 one flow or multiple flows and / or blocks Figure 1 or multiple blocks.

[0156] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, such that the instructions stored in the computer-readable memory produce a manufactured article including instruction means that implement the functions specified in one flow Figure 1 one flow or multiple flows and / or blocks Figure 1 or multiple blocks.

[0157] These computer program instructions can also be loaded onto a computer or other programmable data processing device, such that a series of operation steps are executed on the computer or other programmable device to generate a computer-implemented process, so that the instructions executed on the computer or other programmable device provide steps for implementing the functions specified in one flow Figure 1 one flow or multiple flows and / or blocks Figure 1 or multiple blocks.

[0158] The embodiments of the present invention have been described above in conjunction with the accompanying drawings. However, the present invention is not limited to the above specific embodiments. The above specific embodiments are merely illustrative and not restrictive. Under the inspiration of the present invention, those of ordinary skill in the art can also make many forms without departing from the spirit and scope protected by the present invention and the claims. These all fall within the protection scope of the present invention.

Claims

1. A method for minimizing latency based on block caching and cooperative transmission in clustered D2D communication, characterized in that: Adopt OMA transmission mechanism, including: Get popular content; Chunking and caching popular content to several different devices within the same cluster; When a user makes a request, the plurality of different devices are used to adopt an OMA transmission mechanism to simultaneously send different content blocks to the requesting user; Based on the OMA transmission mechanism, the average rate and average delay of block content transmission are derived; Based on the average rate and average delay, and taking the total bandwidth as a constraint, a maximum transmission delay minimization problem under the OMA transmission mechanism is constructed; Based on the maximum transmission delay minimization problem under the OMA transmission mechanism, the necessary and sufficient conditions for the optimal solution of the bandwidth allocation problem are proved, and based on the necessary and sufficient conditions for the optimal solution of the bandwidth allocation problem, the closed-form solution of the optimal bandwidth allocation is obtained.

2. The method for minimizing the delay of block caching and cooperative transmission based on clustered D2D communication according to claim 1, characterized in that: Based on the OMA transmission mechanism, the average rate and average delay of block content transmission are derived, including: Based on the OMA transmission mechanism, the expected transmission rate of block content is derived using random geometry theory, and the average transmission rate of block content is obtained; Based on the average rate of block content transmission, the average delay of block content transmission is obtained using Jason's inequality.

3. The method for minimizing the delay of block caching and cooperative transmission based on clustered D2D communication according to claim 2, characterized in that: The average rate of block content transmission is expressed as: ； In the formula, Indicates the OMA transmission mechanism The average rate of chunked content, Expressing the The expected transfer rate of chunked content, represents the logarithmic function with base 2, Indicates that the user is requested to receive the first The signal-to-interference ratio of the content of each block; The average delay of the block content is expressed as: ， ； In the formula, Indicates the transmission of the first The average latency of chunked content, Indicates the size of the content. Indicates the number of chunk contents. Indicates the size of the chunk content. Indicates sending The bandwidth used by the chunked content.

4. The method for minimizing the delay of block caching and cooperative transmission based on clustered D2D communication according to claim 2, characterized in that: The maximum transmission delay minimization problem under the OMA transmission mechanism is expressed as: ， ， ； In the formula, Indicates the number of chunk contents. for The bandwidth set allocated to the block content transmission, Indicates that the OMA transmission mechanism is used for transmission The maximum transmission delay of the block content, where It indicates the average delay of sending the first block content under OMA transmission mechanism. Indicates that the first The average latency of chunked content, represents the bandwidth allocation problem with the goal of minimizing the maximum delay, Used to express constraints, where Indicates The bandwidth used for chunked content transmission, Indicates the total available bandwidth.

5. The method for minimizing the delay of block caching and cooperative transmission based on clustered D2D communication according to claim 4, characterized in that: The necessary and sufficient condition for the optimal solution of the bandwidth allocation problem is that the average delay of all block content transmissions is equal, wherein the closed-form solution of the optimal bandwidth allocation is expressed as: ， ； In the formula, Indicates The closed-form solution for the optimal bandwidth allocation of the block content is The bandwidth used for chunked content transmission, Indicates the number of chunk contents. Indicates the transmission of the first The average rate of chunked content, Indicates the transmission of the first The average rate of chunked content.

6. A method for minimizing latency based on block caching and cooperative transmission in clustered D2D communication, characterized in that: Adopt NOMA transmission mechanism, including: Get popular content; Chunking and caching popular content to several different devices within the same cluster; When a user makes a request, the NOMA transmission mechanism is used to simultaneously send different content blocks to the requesting user using the plurality of different devices; Based on the NOMA transmission mechanism, the average rate and average delay of block content transmission are derived; Based on the average rate and average delay, and with the maximum transmission power of the device as a constraint, the maximum transmission delay minimization problem under the NOMA transmission mechanism is constructed; Based on the problem of minimizing the maximum transmission delay under the NOMA transmission mechanism, the particle swarm algorithm is used to optimize the transmission power of the collaborative transmission devices, and a transmission power optimization plan is formulated according to the optimization results.

7. The method for minimizing the delay of block caching and cooperative transmission based on clustered D2D communication according to claim 6, characterized in that: Based on the NOMA transmission mechanism, the average rate and average latency of block content transmission are derived, including: Based on the NOMA transmission mechanism, the expected transmission rate of block content is derived using random geometry theory, and the average transmission rate of block content is obtained; Using Jason's inequality, the average delay of block content transmission is obtained according to the average rate of block content transmission.

8. The method for minimizing the delay of block caching and cooperative transmission based on clustered D2D communication according to claim 7, characterized in that: The average rate of block content transmission is expressed as: ； In the formula, Indicates the NOMA transmission mechanism The average rate of chunked content, Expressing the The transfer rate of chunked content expectations, represents the logarithmic function with base 2, Indicates that the user is requested to receive the first The signal-to-interference ratio of the content of each block; The average delay of the block content transmission is expressed as: ， ； In the formula, Indicates the NOMA transmission mechanism The average delay of chunk content transmission, Indicates the size of the content. Indicates the number of chunk contents. Indicates the size of the chunk content. Represents the total available bandwidth, Indicates the NOMA transmission mechanism The average rate at which chunked content is transferred.

9. The method for minimizing the delay of block caching and cooperative transmission based on clustered D2D communication according to claim 6, characterized in that: The maximum transmission delay minimization problem under the NOMA transmission mechanism is expressed as: ， ， ， ； In the formula, Indicates the number of chunk contents. To send The set of transmission powers used by the block content, Indicates that the transmission is sent using the NOMA transmission mechanism The maximum transmission delay of the block content, where It represents the average delay of the first block content transmission under the NOMA transmission mechanism. Indicates the NOMA transmission mechanism The average delay of chunk content transmission, It is a transmission power optimization problem with the goal of minimizing the maximum delay. Used to indicate constraints. The transmission power of each device when sending content blocks is a positive number and cannot exceed the maximum transmission power of the device. ,in Indicates that the first The power of the content of each block, Indicates the maximum transmit power of the device.

10. The method for minimizing delay based on block caching and cooperative transmission in clustered D2D communication according to claim 9, characterized in that: Based on the problem of minimizing the maximum transmission delay under the NOMA transmission mechanism, the particle swarm algorithm is used to optimize the transmission power of the cooperative transmission device, including: Randomly initialize the positions and velocities of particles in the particle swarm algorithm; According to the maximum value of the average delay of block content transmission under the NOMA transmission mechanism, the objective function is established with the maximum transmission delay minimization problem as the goal, where the maximum value of the average delay of block content transmission under the NOMA transmission mechanism is Expressed as ; Based on the position of the particle, the fitness value is calculated according to the objective function; Update the historical optimal fitness value and position of the individual particle and the historical optimal fitness value and position of the group according to the fitness value; Repeat the following steps until the preset conditions or the maximum number of iterations are reached, and output the optimal fitness value and optimal position: according to Update the particle's velocity, where represents the particle position, represents the inertia weight, and denote the cognitive learning rate constant and the social learning rate constant, respectively. and Respectively The random number inside, and They represent the best historical position of individual particles and the best historical position of the group respectively; according to Update the particle's position, where represents the velocity of the particle; Calculate the fitness value based on the updated particle position; Based on the calculated fitness value, the historical optimal fitness value and position of the individual particle and the historical optimal fitness value and position of the group are updated.

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