A low-orbit satellite network task offloading method based on SFC

Abstract

The present invention seeks protection for a low-orbit satellite network task offloading method based on SFC, which belongs to the field of communication technology. To address the problem that the high time variability of low-orbit satellite networks may lead to low network resource utilization and long task offloading delays, a low-orbit satellite network task offloading method based on SFC is proposed. The method selects an access satellite based on the real-time position relationship between the ground user and the satellite constellation, selects a collaborative satellite and obtains an SFC mapping decision based on the time-varying law of the inter-satellite link and the distribution of satellite resource status, and obtains an SFC resource allocation decision based on the task offloading delay requirements. Through iterative optimization of the SFC mapping decision and resource allocation decision, the satellite network resource utilization is maximized, thereby effectively improving the task offloading completion rate and reducing the system unit task delay.

Description

Technical Field

[0001] The present invention belongs to the field of communication technology, and in particular relates to a low-orbit satellite network task offloading method based on SFC. Background Art

[0002] With the rapid development of satellite communication technology, deploying edge servers within low-orbit satellite networks to directly provide multi-functional task offload services to ground users has become a key development direction for future satellite networks. Network Function Virtualization (NFV) technology decouples network functions from satellite hardware, enabling rapid virtual network function (VNF) mapping and service function chaining (SFC) orchestration and deployment, thereby providing network support for task offload of various compute-intensive and latency-sensitive applications.

[0003] Most of the existing research on satellite network task offloading uses a single satellite to realize the offloading of single-function tasks, and less consideration is given to the inter-satellite collaborative offloading of multi-function tasks. Most of the existing research on the SFC orchestration and deployment of star networks considers the VNF mapping and SFC deployment issues under the condition of stable inter-satellite links of the same type of orbit, and less consideration is given to the impact of the high time-varying characteristics of inter-satellite links of heterogeneous orbits on the stability of SFC in actual star network applications. The problem involved in the present invention mainly considers the impact of the rapid time-varying state of the inter-satellite link on the sustainability and effectiveness of the SFC, which in turn poses a serious challenge to the quality and performance of multi-function task offloading. In response to the above problems, the present invention proposes a low-orbit satellite network task offloading method based on SFC according to the development of future satellite networks and the application of new services. By ensuring the stability of SFC deployment and maximizing resource utilization within the task delay threshold, the completion rate of multi-function task offloading is effectively improved, and the system unit task delay is reduced. Summary of the Invention

[0004] The present invention aims to solve the above problems of the prior art. A low-orbit satellite network task offloading method based on SFC is proposed. The technical solution of the present invention is as follows:

[0005] A low-orbit satellite network task offloading method based on SFC comprises the following steps:

[0006] 101. According to the task offloading request Q proposed by the ground user u, initialize the optimal deployment fitness σ of the service function chain SFC * =0, candidate mapping satellite set Candidate access satellite set Count variable j = 0;

[0007] 102. Add the satellites in the satellite set S that meet the access conditions of user u to the set S a ,if Jump to step 103, otherwise, jump to step 111;

[0008] 103. If j < |V|, where V represents the ordered set of virtual network functions (VNFs) required for task offloading, let j = j + 1, and the temporary set S a ′=S a , jump to step 104, otherwise, jump to step 110;

[0009] 104. If From S a ′, and let user u’s access satellite s be a =s, jump to step 105, otherwise, jump to step 103;

[0010] 105. Set the distance s a Satellite j hop range and meets All satellites are added to the set S m ,in, represents the remaining available computing resources of satellite s, z0 represents the basic computing resources required for VNF instantiation, if |V|≤|S m |, let i = 0, jump to step 106, otherwise jump to step 104;

[0011] 106. If i<I, where I represents the m The maximum number of times to search for SFC, let i = i + 1, jump to step 107, otherwise jump to step 104;

[0012] 107. According to the access satellite s a , construct and update the node and link mapping decision {X, Y} of the SFC required by user u. If successful, jump to step 108, otherwise, jump to step 106;

[0013] 108. Based on the SFC mapping decision {X, Y}, construct and update the resource allocation decision Z of the SFC required by user u. If successful, jump to step 109; otherwise, jump to step 106.

[0014] 109. Calculate the SFC deployment fitness σ based on the SFC deployment decision {X, Y, Z}. If σ * ≤σ, let σ * =σ, SFC optimal deployment decision {X * ,Y * ,Z *}={X,Y,Z}, jump to step 106, otherwise, jump to step 106;

[0015] 110. Output SFC optimal deployment decision {X * ,Y * ,Z *};

[0016] 111. End.

[0017] Furthermore, in step 102, the satellites in the satellite set S that meet the access conditions of user u are added to the set S. a The methods specifically include:

[0018] will satisfy β u,s ≥β min and T u,s Satellites s with a value greater than or equal to T are added to the set S a , where β u,s represents the elevation angle between the ground user u and the satellite s, and the calculation method is shown in formula (1), β min Indicates the minimum elevation angle for satellite-to-ground communication, T u,s represents the remaining service time of satellite s to ground user u, and T represents the mission tolerance delay;

[0019]

[0020] In formula (1), Δφ1=φ u -φ s ,φ u and denote the longitude and latitude of ground user u, φ s and They represent the longitude and latitude of the satellite s, R represents the radius of the earth, and h represents the orbital height of the satellite relative to the ground.

[0021] Furthermore, the step 107 constructs and updates the node and link mapping decision {X, Y} of the SFC required by user u, specifically including the following steps:

[0022] 1) Initialize temporary set S′=S m , temporary node s′=s a , counting variables k=0, l=0;

[0023] 2) If k < |V|, set k = k + 1 and jump to step 3); otherwise, jump to step 6);

[0024] 3) For each satellite s in the set S′, calculate the minimum cost path between satellite node s′ and s And delete the satellite nodes that do not have the minimum cost path from the set S′;

[0025] 4) If Calculate the mapping probability η of each satellite in the set S′ s , according to the probability distribution {η s | s∈S′ Randomly pick out a satellite s from S′ and jump to step 5), otherwise, jump to step 7);

[0026] 5) Add satellite s as the kth VNF mapping satellite to the temporary node mapping decision X′, path Add the temporary link mapping decision Y′ as the lth virtual link, remove satellite s from the set S′, set s′=s, l=l+1, and jump to step 2);

[0027] 6) Calculate the satellite node s′ to s a The shortest path between And the passage Add Y′, set {X, Y} = {X′, Y′}, and output the SFC mapping decision {X, Y};

[0028] 7) The algorithm ends.

[0029] Furthermore, the minimum cost path between satellite nodes s′ and s in step 3) The specific solution methods include:

[0030]

[0031] Update the cost ω of each intersatellite physical link e in the satellite network according to formula (2) e , where b e , denote the total bandwidth resources and remaining available bandwidth resources of link e, t e represents the duration of link e, b represents the task transmission bandwidth, and the minimum cost path algorithm is used to calculate the minimum cost path between satellite nodes s′ and s

[0032] Furthermore, the mapping probability η of each satellite in the set S′ in step 4) is s The calculation of is shown in formula (3):

[0033]

[0034] In formula (3), Represents the remaining available computing resources of satellite s The total computing resources z of satellite s s The ratio, χ s represents the sharing weight factor of satellite s.

[0035] Furthermore, the method for constructing and updating the resource allocation decision Z of the SFC required by user u in step 108 specifically includes the following steps:

[0036] 11) According to the node mapping decision X, the mapped satellites are sequentially added to the temporary set S′. According to the link mapping decision Y, the bandwidth b required by the virtual link is added to the SFC resource allocation decision Z. The counting variable k = 0, and the number of VNFs without allocated computing resources v = |V|;

[0037] 12) If k < |V|, set k = k + 1 and jump to step 13); otherwise, jump to step 15);

[0038] 13) If the kth satellite s in S′ has been deployed to meet the required instance of the kth VNF in SFC, jump to step 14), otherwise, allocate the basic computing resources z0 required for the VNF instantiation in satellite s, let Skip to step 14);

[0039] 14) According to the task offloading request Q proposed by user u, calculate the task computing resources allocated by satellite s to user u make Calculate the remaining computation delay t res , if t res ≥0, set v=v-1 and jump to step 12); otherwise, jump to step 18);

[0040] 15) Calculate the offloading completion delay t of task Q. If t>T, jump to step 16), otherwise, jump to step 17);

[0041] 16) The satellites of are removed from the set S′ if according to The value of , sort the elements in the set S ' in descending order, and for the first satellite s in S ', add unit computing resources z1 to the VNF instance of user u, let Jump to step 15), otherwise, jump to step 18);

[0042] 17) According to the node mapping decision X, the task computing resources allocated to user u on each mapping satellite s are Add Z and output SFC resource allocation decision Z;

[0043] 18) End the algorithm.

[0044] Furthermore, in step 14), the satellite s allocates the task computing resources to the user u. And the remaining computation delay t res The calculation of is shown in formula (4) and formula (5):

[0045]

[0046]

[0047] In formula (4), o and They represent the task data volume and task complexity of task Q, t res represents the remaining available computing delay of task Q, v represents the number of VNFs that are not currently allocated computing resources, and in formula (5), according to the link mapping decision Y, the total task transmission delay t is obtained tra Total task propagation delay t pro , where t tra With t pro are the cumulative transmission delay and propagation delay of task data through each physical link on the offloading path, respectively.

[0048] Furthermore, the unloading completion delay t of task Q in step 15) is calculated as shown in formula (6):

[0049] t=t com +t tra +t pro (6)

[0050]

[0051] In formula (6), t com represents the total computational delay of task Q, which is calculated as shown in formula (7).

[0052] Furthermore, the SFC deployment fitness σ in step 109 is calculated as shown in formula (8):

[0053]

[0054] In formula (8), They represent the normalized computing resources and normalized bandwidth resources required for task offloading, represents the normalized task offloading completion delay, 0≤τ1≤1, 0≤τ2≤1, 0≤τ3≤1, where The calculation is shown in formula (9)(10)(11):

[0055]

[0056]

[0057]

[0058] In formula (10), E represents the set of all inter-satellite physical links in the satellite network, It represents the bandwidth resources allocated by the intersatellite link e to user u.

[0059] An electronic device comprises a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the program, the method for offloading low-orbit satellite network tasks based on SFC as described in any one of the items is implemented.

[0060] The advantages and beneficial effects of the present invention are as follows:

[0061] The present invention discloses a low-orbit satellite network task offloading method based on SFC. Existing research on satellite network task offloading mostly uses a single satellite to implement the offloading of single-function tasks, and rarely considers the inter-satellite collaborative offloading of multi-function tasks. Existing research on star network SFC orchestration and deployment mostly considers the VNF mapping and SFC deployment issues under the condition of stable inter-satellite links of the same type of orbit, and rarely considers the impact of the high time-varying characteristics of inter-satellite links of heterogeneous orbits on SFC stability in actual star network applications. In order to address the problem that the high time-varying nature of low-orbit satellite networks may lead to low network resource utilization and long task offloading delay, the present invention selects access satellites based on the real-time position relationship between the user and the satellite constellation, selects collaborative satellites and constructs SFC mapping decisions based on the star network operation rules, satellite computing resources, inter-satellite link resources and the shareability of VNF instances, and constructs resource allocation decisions based on the task delay tolerance requirements and satellite computing resource status. Through iterative optimization of SFC mapping decisions and resource allocation decisions, the resource utilization of the star network is continuously improved, thereby effectively improving the task offloading completion rate and reducing the user's unit task offloading delay. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] Figure 1 The present invention provides a flowchart of a low-orbit satellite network task offloading method based on SFC in a preferred embodiment. DETAILED DESCRIPTION

[0063] The following will describe the technical solutions in the embodiments of the present invention in detail with reference to the accompanying drawings. The described embodiments are only a part of the embodiments of the present invention.

[0064] The technical solution of the present invention to solve the above technical problems is:

[0065] The concepts and models involved in the content of this invention are as follows.

[0066] 1. Network Model

[0067] The present invention assumes that the low-orbit satellite network consists of several satellites in the same orbital plane and different orbital planes, and the satellites communicate directly through line-of-sight links or forward communications through cooperative satellites. Each satellite carries a server with a certain computing capability and can deploy any type of VNF instance. Ground users access the satellite network through the satellite-to-ground link and send an offload task request. The star network completes the task offload requested by the user by instantiating the required VNF on multiple satellites and arranging and building the corresponding SFC. Each VNF in the SFC is mapped to a different satellite, and the same type of VNF instance can be shared between different SFCs.

[0068] 2. Other symbols involved in the present invention are explained as follows.

[0069] Q: Task offloading request made by user u

[0070] V: the ordered set of VNFs required by task Q

[0071] T: Task tolerance delay of task Q

[0072] t: Delay in completing the offloading of task Q

[0073] b: The transmission bandwidth of task Q

[0074] E: The collection of all intersatellite physical links in the satellite network

[0075] S: the set of all satellites in the satellite network

[0076] t e : Duration of intersatellite link e

[0077] The remaining available bandwidth resources of the intersatellite link e

[0078] b e : Total bandwidth resources of intersatellite link e

[0079] The remaining computing resources of satellite s

[0080] z s : Total computing resources of satellite s

[0081] ε u,s : The elevation angle between the ground user u and the satellite s

[0082] T u,s : The remaining service time of satellite s to ground user u Computing resources allocated by satellite s to user u

[0083] The bandwidth resources allocated by the intersatellite link e to user u

[0084] The technical solutions of the present invention are described as follows.

[0085] 1. Elevation angle β between ground user u and satellite s u,s , calculated as shown in formula (1):

[0086]

[0087] In formula (1), Δφ1=φ u -φ s ,φ u and denote the longitude and latitude of ground user u, φ s and They represent the longitude and latitude of the satellite s, R represents the radius of the earth, and h represents the orbital height of the satellite relative to the ground;

[0088] 2. The cost of each intersatellite physical link e in the satellite network ω e , calculated as shown in formula (2):

[0089]

[0090] In formula (2), b e , denote the total bandwidth resources and remaining available bandwidth resources of link e, t e represents the duration of link e, b represents the task transmission bandwidth, and T represents the task tolerance delay;

[0091] 3. The mapping probability η of each satellite in the set S′ s , calculated as shown in formula (3):

[0092]

[0093] In formula (3), Represents the remaining available computing resources of satellite s The total computing resources z of satellite s s The ratio, χ s represents the shared weight factor of satellite s;

[0094] 4. Satellite s allocates computing resources to user u The calculation is shown in formula (4):

[0095]

[0096] In formula (4), o and They represent the task data volume and task complexity of task Q, t res represents the remaining computational delay of task Q, and v represents the number of VNFs that are not currently allocated computing resources;

[0097] 5. Remaining computational delay t of task Q res , the calculation method is shown in formula (5):

[0098]

[0099] In formula (5), according to the link mapping decision Y, the total task transmission delay t is obtained tra Total task propagation delay t pro , where t tra With t pro are the cumulative transmission delay and propagation delay of task data through each physical link on the offloading path respectively;

[0100] 6. Total computational delay t for task Q com , the calculation method is shown in formula (6):

[0101] t=t com +t tra +t pro (6)

[0102] 7. The offloading completion delay t of task Q is calculated as shown in formula (7):

[0103]

[0104] 8. Normalized computing resources required for task offloading The calculation is shown in formula (8):

[0105]

[0106] In formula (8), z s represents the total computing resources of satellite s, S represents the set of satellites;

[0107] 9. Normalized bandwidth resources required for task offloading The calculation is shown in formula (9):

[0108]

[0109] In formula (9), E represents the set of all inter-satellite physical links in the satellite network, represents the bandwidth resources allocated by the intersatellite link e to user u;

[0110] 10. Normalized task offloading completion delay The calculation is shown in formula (10):

[0111]

[0112] 11. SFC deployment fitness σ is calculated as shown in formula (11):

[0113]

[0114] In formula (11), 0≤τ1≤1, 0≤τ2≤1, 0≤τ3≤1;

[0115] 12. Sub-algorithm 1: Constructing SFC mapping decision

[0116] 1) Initialize temporary set S′=S m , temporary node s′=s a , counting variables k=0, l=0;

[0117] 2) If k < |V|, set k = k + 1 and jump to step 3); otherwise, jump to step 6);

[0118] 3) For each satellite s in the set S′, calculate the minimum cost path between satellite node s′ and s And delete the satellite nodes that do not have the minimum cost path from the set S′;

[0119] 4) If Calculate the mapping probability η of each satellite in the set S′ s , according to the probability distribution {η s | s∈S′ Randomly pick out a satellite s from S′ and jump to step 5), otherwise, jump to step 7);

[0120] 5) Add satellite s as the kth VNF mapping satellite to the temporary node mapping decision X′, path Add the temporary link mapping decision Y′ as the lth virtual link, remove satellite s from the set S′, set s′=s, l=l+1, and jump to step 2);

[0121] 6) Calculate the satellite node s′ to s a The shortest path between And the passage Add Y′, set {X, Y} = {X′, Y′}, and output the SFC mapping decision {X, Y};

[0122] 7) The algorithm ends.

[0123] 13. Sub-algorithm 2: Constructing SFC resource allocation decision

[0124] 11) According to the node mapping decision X, the mapped satellites are sequentially added to the temporary set S′. According to the link mapping decision Y, the bandwidth b required by the virtual link is added to the SFC resource allocation decision Z. The counting variable k = 0, and the number of VNFs without allocated computing resources v = |V|;

[0125] 12) If k < |V|, set k = k + 1 and jump to step 13); otherwise, jump to step 15);

[0126] 13) If the kth satellite s in S′ has been deployed to meet the required instance of the kth VNF in SFC, jump to step 14), otherwise, allocate the basic computing resources z0 required for the VNF instantiation in satellite s, let Skip to step 14);

[0127] 14) According to the task offloading request Q proposed by user u, calculate the task computing resources allocated by satellite s to user u make Calculate the remaining computation delay t res , if t res ≥0, set v=v-1 and jump to step 12); otherwise, jump to step 18);

[0128] 15) Calculate the offloading completion delay t of task Q. If t>T, jump to step 16), otherwise, jump to step 17);

[0129] 16) The satellites of are removed from the set S′ if according to The value of , sort the elements in the set S ' in descending order, and for the first satellite s in S ', add unit computing resources z1 to the VNF instance of user u, let Jump to step 15), otherwise, jump to step 18);

[0130] 17) According to the node mapping decision X, the task computing resources allocated to user u on each mapping satellite s are Add Z and output SFC resource allocation decision Z;

[0131] 18) End the algorithm.

[0132] A low-orbit satellite network task offloading method based on SFC, the specific implementation method includes the following steps:

[0133] Step 1: Initialize the optimal deployment fitness σ of the service function chain SFC according to the task offloading request Q proposed by the ground user u * =0, candidate mapping satellite set Candidate access satellite set Count variable j = 0;

[0134] Step 2: Add the satellites in the satellite set S that meet the access conditions of user u to the set S a ,if Jump to step 3, otherwise, jump to step 11;

[0135] Step 3: If j < |V|, where V represents the ordered set of virtual network functions (VNFs) required for task offloading, let j = j + 1, and the temporary set S a ′=S a , jump to step 4, otherwise, jump to step 10;

[0136] Step 4: If From S a ′, and let user u’s access satellite s be a =s, jump to step 5, otherwise, jump to step 3;

[0137] Step 5: Set the distance s a Satellite j hop range and meets All satellites are added to the set S m ,in, represents the remaining available computing resources of satellite s, z0 represents the basic computing resources required for VNF instantiation, if |V|≤|S m |, let i = 0, jump to step 6, otherwise, jump to step 4;

[0138] Step 6: If i<I, where I represents the m The maximum number of times to search for SFC, let i = i + 1, jump to step 7, otherwise, jump to step 4;

[0139] Step 7: According to the access satellite s a , call sub-algorithm 1 to build and update the node and link mapping decision {X, Y} of the SFC required by user u. If successful, jump to step 8, otherwise, jump to step 6;

[0140] Step 8: Based on the SFC mapping decision {X, Y}, call sub-algorithm 2 to construct and update the resource allocation decision Z of the SFC required by user u. If successful, jump to step 9; otherwise, jump to step 6.

[0141] Step 9: Calculate the SFC deployment fitness σ based on the SFC deployment decision {X, Y, Z}. If σ * ≤σ, let σ * =σ, SFC optimal deployment decision {X * ,Y * ,Z *}={X,Y,Z}, jump to step 6, otherwise, jump to step 6;

[0142] Step 10: Output the optimal SFC deployment decision {X * ,Y * ,Z *};

[0143] Step 11: The algorithm ends.

[0144] The systems, devices, modules, or units described in the above embodiments may be implemented by computer chips or entities, or by products having certain functions. A typical implementation device is a computer. Specifically, the computer may be, for example, a personal computer, a laptop computer, a cellular phone, a camera phone, a smartphone, a personal digital assistant, a media player, a navigation device, an email device, a game console, a tablet computer, a wearable device, or a combination of any of these devices.

[0145] It should also be noted that the terms "comprises," "includes," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, commodity, or apparatus that includes a series of elements includes not only those elements but also other elements not explicitly listed, or includes elements inherent to such process, method, commodity, or apparatus. In the absence of further limitations, an element defined by the phrase "comprises a ..." does not exclude the presence of other identical elements in the process, method, commodity, or apparatus that includes the element.

[0146] The above embodiments should be understood as merely illustrating the present invention and not as limiting the scope of protection of the present invention. After reading the contents of the present invention, technicians may make various changes or modifications to the present invention, and these equivalent changes and modifications also fall within the scope defined by the claims of the present invention.

Claims

1. A low-orbit satellite network task offloading method based on SFC, characterized in that: The following steps are involved:

101. According to the task offloading request Q proposed by the ground user u, initialize the optimal deployment fitness σ of the service function chain SFC * =0, candidate mapping satellite set Candidate access satellite set Count variable j = 0; 102. Add the satellites in the satellite set S that meet the access conditions of user u to the set S a ,if Jump to step 103, otherwise, jump to step 111; 103. If j < |V|, where V represents the ordered set of virtual network functions (VNFs) required for task offloading, let j = j + 1, and the temporary set S a ′=S a , jump to step 104, otherwise, jump to step 110; 104. If From S a ′, and let user u’s access satellite s be a =s, jump to step 105, otherwise, jump to step 103; 105. Set the distance s a Satellite j hop range and meets All satellites of join the set S m ,in, represents the remaining available computing resources of satellite s, z0 represents the basic computing resources required for VNF instantiation, if |V|≤|S m |, let i = 0, jump to step 106, otherwise jump to step 104; 106. If i<I, where I represents the m The maximum number of times to search for SFC, let i = i + 1, jump to step 107, otherwise jump to step 104; 107. According to the access satellite s a , construct and update the node and link mapping decision {X, Y} of the SFC required by user u. If successful, jump to step 108, otherwise, jump to step 106; 108. Based on the SFC mapping decision {X, Y}, construct and update the resource allocation decision Z of the SFC required by user u. If successful, jump to step 109; otherwise, jump to step 106.

109. Calculate the SFC deployment fitness σ based on the SFC deployment decision {X, Y, Z}. If σ * ≤σ, let σ * =σ, SFC optimal deployment decision {X * ,Y * ,Z * }={X,Y,Z}, jump to step 106, otherwise, jump to step 106; 110. Output SFC optimal deployment decision {X * ,Y * ,Z * }; 111. End; The step 107 constructs and updates the node and link mapping decision {X, Y} of the SFC required by user u, specifically including the following steps: 1) Initialize temporary set S′=S m , temporary node s′=s a , counting variables k=0, l=0; 2) If k < |V|, set k = k + 1 and jump to step 3); otherwise, jump to step 6); 3) For each satellite s in the set S′, calculate the minimum cost path between satellite node s′ and s And delete the satellite nodes that do not have the minimum cost path from the set S′; 4) If Calculate the mapping probability η of each satellite in the set S′ s , according to the probability distribution {η s | s∈S′ Randomly take out a satellite s from S′ and jump to step 5), otherwise, jump to step 7); 5) Add satellite s as the kth VNF mapping satellite to the temporary node mapping decision X′, path Add the temporary link mapping decision Y′ as the lth virtual link, remove satellite s from the set S′, set s′=s, l=l+1, and jump to step 2); 6) Calculate the satellite node s′ to s a The shortest path between And the passage Add Y′, set {X, Y} = {X′, Y′}, and output the SFC mapping decision {X, Y}; 7) The algorithm ends; The method for constructing and updating the resource allocation decision Z of the SFC required by user u in step 108 specifically includes the following steps: 11) According to the node mapping decision X, the mapped satellites are sequentially added to the temporary set S′. According to the link mapping decision Y, the bandwidth b required by the virtual link is added to the SFC resource allocation decision Z. The counting variable k = 0, and the number of VNFs without allocated computing resources v = |V|; 12) If k < |V|, set k = k + 1 and jump to step 13); otherwise, jump to step 15); 13) If the kth satellite s in S′ has been deployed to meet the required instance of the kth VNF in SFC, jump to step 14), otherwise, allocate the basic computing resources z0 required for the VNF instantiation in satellite s, let Skip to step 14); 14) According to the task offloading request Q proposed by user u, calculate the task computing resources allocated by satellite s to user u make Calculate the remaining computational delay t res , if t res ≥0, set v=v-1 and jump to step 12); otherwise, jump to step 18); 15) Calculate the offloading completion delay t of task Q. If t>T, jump to step 16), otherwise, jump to step 17); 16) The satellites of are removed from the set S′ if according to The value of , sort the elements in the set S ' in descending order, and for the first satellite s in S ', add unit computing resources z1 to the VNF instance of user u, let Jump to step 15), otherwise, jump to step 18); 17) According to the node mapping decision X, the task computing resources allocated to user u on each mapping satellite s are Add Z and output SFC resource allocation decision Z; 18) End the algorithm; The SFC deployment fitness σ in step 109 is calculated as shown in formula (8): In formula (8), They represent the normalized computing resources and normalized bandwidth resources required for task offloading, represents the normalized task offloading completion delay, 0≤τ1≤1, 0≤τ2≤1, 0≤τ3≤1, where The calculation is shown in formula (9)(10)(11): In formula (10), E represents the set of all inter-satellite physical links in the satellite network, It represents the bandwidth resources allocated by the intersatellite link e to user u.

2. The method for offloading low-orbit satellite network tasks based on SFC according to claim 1, characterized in that: In step 102, the satellites in the satellite set S that meet the access conditions of user u are added to the set S. a The methods specifically include: will satisfy β u,s ≥β min and T u,s Satellites s with a value greater than or equal to T are added to the set S a , where β u,s represents the elevation angle between the ground user u and the satellite s, and the calculation method is shown in formula (1), β min Indicates the minimum elevation angle for satellite-to-ground communication, T u,s represents the remaining service time of satellite s to ground user u, and T represents the mission tolerance delay; In formula (1), Δφ1=φ u -φ s ,φ u and denote the longitude and latitude of ground user u, φ s and They represent the longitude and latitude of the satellite s, R represents the radius of the earth, and h represents the orbital height of the satellite relative to the ground.

3. The method for offloading low-orbit satellite network tasks based on SFC according to claim 1, characterized in that: The minimum cost path between satellite nodes s′ and s in step 3) The specific solution methods include: Update the cost ω of each intersatellite physical link e in the satellite network according to formula (2) e , where b e , denote the total bandwidth resources and remaining available bandwidth resources of link e, t e represents the duration of link e, b represents the task transmission bandwidth, and the minimum cost path algorithm is used to calculate the minimum cost path between satellite nodes s′ and s 4. The method for offloading low-orbit satellite network tasks based on SFC according to claim 1, characterized in that: The mapping probability η of each satellite in the set S′ in step 4) s The calculation of is shown in formula (3): In formula (3), Represents the remaining available computing resources of satellite s The total computing resources z of satellite s s The ratio, χ s represents the sharing weight factor of satellite s.

5. The method for offloading low-orbit satellite network tasks based on SFC according to claim 4, characterized in that: In step 14), satellite s is the task computing resource allocated to user u. And the remaining computation delay t res The calculation of is shown in formula (4) and formula (5): In formula (4), o and They represent the task data volume and task complexity of task Q, t res represents the remaining available computing delay of task Q, v represents the number of VNFs that are not currently allocated computing resources, and in formula (5), according to the link mapping decision Y, the total task transmission delay t is obtained tra Total task propagation delay t pro , where t tra With t pro are the cumulative transmission delay and propagation delay of task data through each physical link on the offloading path, respectively.

6. The method for offloading low-orbit satellite network tasks based on SFC according to claim 5, characterized in that: The unloading completion delay t of task Q in step 15) is calculated as shown in formula (6): t=t com +t tra +t pro (6) In formula (6), t com represents the total computational delay of task Q, which is calculated as shown in formula (7).

7. An electronic device, characterized in that: The invention comprises a memory, a processor and a computer program stored in the memory and executable on the processor, wherein when the processor executes the program, the low-orbit satellite network task offloading method based on SFC as claimed in any one of claims 1 to 6 is implemented.

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