CN113365309A - Content caching and distributing method based on regional collaboration in satellite Internet - Google Patents

Content caching and distributing method based on regional collaboration in satellite Internet Download PDF

Info

Publication number
CN113365309A
CN113365309A CN202110476523.3A CN202110476523A CN113365309A CN 113365309 A CN113365309 A CN 113365309A CN 202110476523 A CN202110476523 A CN 202110476523A CN 113365309 A CN113365309 A CN 113365309A
Authority
CN
China
Prior art keywords
satellite
content
cache
caching
snapshot
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
CN202110476523.3A
Other languages
Chinese (zh)
Other versions
CN113365309B (en
Inventor
任品毅
郝林春
杜清河
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Xian Jiaotong University
Original Assignee
Xian Jiaotong University
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Xian Jiaotong University filed Critical Xian Jiaotong University
Priority to CN202110476523.3A priority Critical patent/CN113365309B/en
Publication of CN113365309A publication Critical patent/CN113365309A/en
Application granted granted Critical
Publication of CN113365309B publication Critical patent/CN113365309B/en
Active legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Images

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W28/00—Network traffic management; Network resource management
    • H04W28/02—Traffic management, e.g. flow control or congestion control
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L67/00—Network arrangements or protocols for supporting network services or applications
    • H04L67/50—Network services
    • H04L67/56—Provisioning of proxy services
    • H04L67/568—Storing data temporarily at an intermediate stage, e.g. caching
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W84/00—Network topologies
    • H04W84/02—Hierarchically pre-organised networks, e.g. paging networks, cellular networks, WLAN [Wireless Local Area Network] or WLL [Wireless Local Loop]
    • H04W84/04—Large scale networks; Deep hierarchical networks
    • H04W84/06—Airborne or Satellite Networks
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02D—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE
    • Y02D30/00—Reducing energy consumption in communication networks
    • Y02D30/70—Reducing energy consumption in communication networks in wireless communication networks

Landscapes

  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Physics & Mathematics (AREA)
  • Astronomy & Astrophysics (AREA)
  • General Physics & Mathematics (AREA)
  • Radio Relay Systems (AREA)

Abstract

The invention discloses a content caching and distributing method based on regional collaboration in a satellite internet, which divides a low-orbit satellite network topology into a plurality of sub-regions according to the minimum distribution path time delay and calculates a similar region set by using the regional caching similarity through a clustering algorithm. And aiming at the similar area, redundant contents are removed, and the diversity of network cache contents is increased under the condition of limited storage space. Meanwhile, when the request is not hit, the content is preferentially requested among the similar areas, so that the cache hit rate and the network throughput are improved. Aiming at the condition that the cache satellite of continuous snapshots in the same area in the regular constellation network is transformed between adjacent orbits, when topology is switched, hot content is determined to be transmitted to the next snapshot cache satellite or the future same-orbit cache satellite according to the hop count between the current cache satellite and the next snapshot cache satellite, so that repeated requests for content from a ground server are avoided, and the waste of inter-satellite link resources caused by repeated back-and-forth transmission of the cache content between the orbits is reduced.

Description

Content caching and distributing method based on regional collaboration in satellite Internet
Technical Field
The invention belongs to the technical field of satellite internet content caching and distribution, and particularly relates to a content caching and distribution method based on regional collaboration in a satellite internet.
Background
As communication technologies continue to evolve, the size of networks and the data traffic in the networks are also growing explosively. Particularly, the popularization of the ground mobile terminal enables people to live more conveniently and simultaneously enables ground traffic to increase at a high speed, and the next generation network puts strict requirements on communication with higher bandwidth and lower time delay. The existing communication infrastructure is generally located in areas with dense people flow and deployable areas, and the infrastructure in some remote areas is deficient, so that the ground facilities are easily damaged due to frequent natural disasters, and the quality of network transmission is influenced. In recent years, satellites are widely used in various emergency communication occasions by virtue of advantages such as wide coverage and no influence from geographical environment, and meanwhile, air-ground integration is a development trend of future networks, and the satellites and a ground network cooperate with each other to provide services such as content caching and data transmission for users.
However, due to the fact that the satellite communication distance is long and the topology changes dynamically, the problems of large time delay, intermittent interruption and the like exist in end-to-end transmission in the satellite network. With the development of satellite technology and the improvement of on-satellite processing capacity, it is also possible to deploy content caching in a satellite network. The deployment of the on-satellite cache can enable the ground user to access the content cached on the satellite with smaller time delay, and the content does not need to be transmitted from end to end through a long distance and is not limited by ground facilities. Meanwhile, the cache in the network can reduce the load of the content server to a certain extent, save the bandwidth of the inter-satellite communication link and avoid network congestion. When a large number of users access the same data to the server, a large amount of repeated data exists in the transmission process, and redundancy and transmission delay are increased to a certain extent. With the rapid increase of users, the transmission performance of the network also drops rapidly.
At present, the caching strategy of the ground network is relatively mature, and the research on the caching of the satellite network is relatively less. In the solution using the satellite terminal cache, the satellite terminal decides whether to cache the requested content by comparing the similarity and distance between the user request and the user's interests in the vicinity of the terminal. But this solution does not have the limitation of escaping the terrestrial infrastructure using the satellite terminals for caching. In addition, the existing cache scheme based on partition divides the network into a plurality of disjoint sub-areas by backtracking, and calculates the cache strategy of the content by using the multi-knapsack problem for reference. However, when the constellation is large, the complexity of the backtracking algorithm is high, and meanwhile, the scheme has no cooperation between the regions, and the content searching efficiency between the regions is low.
Disclosure of Invention
The invention aims to provide a content caching and distributing method based on regional collaboration in satellite internet, so as to overcome the defects of the prior art.
In order to achieve the purpose, the invention adopts the following technical scheme:
a content caching and distributing method based on regional collaboration in satellite Internet comprises the following steps:
s1, pre-calculating a cache node set of each snapshot and partitioning an LEO cache layer network topology by using a medium earth orbit satellite through a satellite and ground network topology, and storing the cache node set and a topology partitioning result on an MEO satellite;
s2, collecting ground user request information in a fixed time interval through an LEO satellite, forming a list of requested probability of the content and sending the list to an MEO satellite;
s3, calculating a cache strategy through user request information, a cache node set and a topology partitioning result collected by the MEO satellite and sending a cache plan to the LEO layer cache satellite;
s4, the ground station sends the message of the generated content to the MEO satellite connected with the ground station, and the ground station informs the user through the MEO satellite broadcast;
s5, the user sends out content request and transfers it to the buffer satellite or ground server through LEO layer satellite;
s6, the LEO layer cache satellite caches the content of the response request of the cache satellite or the ground server according to the cache plan;
and S7, when the topology is switched, according to the hop count between the current cache satellite and the next snapshot cache satellite, determining to transmit part of popular content to the next snapshot cache satellite or the future same-orbit cache satellite for caching.
Further, the topology at equal time intervals is static, the topology at each interval is regarded as an undirected graph G ═ V, E, where V denotes a set of satellites and ground stations, i.e., V ═ S ═ GS, E denotes a set of all inter-satellite links and all satellite-ground links, and in each snapshot, a routing and caching strategy is calculated according to the undirected graph G and other network information.
Further, the shortest transmission path from the ground station to each LEO satellite is calculated by using a Dijkstra shortest path algorithm.
Further, selecting a proper cache node in the shortest path tree for caching the content, and dividing the whole network topology into a plurality of disjoint sub-trees T; the root node c of the subtree is used as a cache node of the area T (c) where the subtree is located and is responsible for providing content transmission for users covered by the area.
Further, the node with the smallest sum of path delays to other nodes in the network is sequentially selected as a cache node set C ═ C1,c2,...,cCThe cache node obtained by the method can reduce the time delay from other nodes in the network to the cache node to acquire the content, and the calculation formula of the minimum distribution path time delay is as follows:
Figure BDA0003047263170000031
wherein, Td(i, j) is the propagation delay between node i and node j, Tp(i, j) is the transmission delay.
Further, the MEO satellite preferentially adds the content with the greater regional popularity in each region to the regional cache content set F according to the pre-calculated partitions using the collected request probability informationc＝{f1.....fmaxIn the method, the maximum storable content number of the cached satellite is max, assuming that the storage space of the cached satellite is limited.
Further, all the areas are clustered through a k-medoids clustering algorithm, wherein the distance measure is closeijRegarding similar and similar areas as a virtual area, and regarding each area in the virtual areaCache content set FcAnd optimizing to remove redundant cache contents.
Furthermore, the LEO satellite is used as a user access layer and a content cache layer, each LEO satellite broadcasts access signals periodically, and the ground user directly communicates with the LEO satellite.
Further, when a user requests contents from an accessed LEO layer satellite, information Q (f) is requested1) Transmitting through satellite network, if the cache is hit in the local area, feeding back the content to the user, otherwise, feeding back the content to the cache node s in the similar area1,kRequest content, eventually by responding to R (f)1) And feeding back the content to the user, and requesting the content from the ground server if the content is not found yet.
Further, the transmission of the cache content during snapshot switching is optimized:
(1) caching satellite s if k +1 snapshotj,k+1Caching satellite s by using distance k snapshoti,kOne jump, then snapshot switches to δ1Time, si,kDirect transmission of partially popular content to sj,k+1And updated during the k +1 snapshot according to a caching policy, δ1The calculation is as follows:
δ1＝qi,k·d(sj,k+1,si,k) (8)
wherein q isi,kIs si,kNumber of contents to be transmitted, d(s)j,k+1,si,k) Is the propagation delay between the two cached satellites.
(2) If sj,k+1And si,kMore than one hop apart, delta before k snapshot switches2Time, original buffer satellite si,kSending partially popular content to the same track k + Δ k1Snapshot caching satellite
Figure BDA0003047263170000041
If k +1 snapshot different orbit cache satellite sj,k+1Cached satellite s with k-1 snapshotn,k-1In the same orbit, the satellite s is illustratedj,k+1Has cached satellite sn,k-1Content of transmission, then satellite si,kNo longer to satellite sj,k+1The content is transmitted to the mobile terminal,sj,k+1the update is done directly on the next snapshot. Finally, the original cache satellite s is deleted during snapshot switchingi,kBuffer contents of (1), δ2Is calculated as follows:
Figure BDA0003047263170000051
compared with the prior art, the invention has the following beneficial technical effects:
the invention discloses a content caching and distributing method based on regional collaboration in a satellite internet, which divides a low-orbit satellite network topology into a plurality of sub-regions according to the minimum distribution path time delay and calculates a similar region set by using the regional caching similarity through a clustering algorithm. And aiming at the similar area, redundant contents are removed, and the diversity of network cache contents is increased under the condition of limited storage space. Meanwhile, when the request is not hit, the content is preferentially requested among the similar areas, so that the cache hit rate and the network throughput are improved. Aiming at the condition that the cache satellite of continuous snapshots in the same area in a regular constellation network is transformed between adjacent tracks, when topology is switched, hot content is determined to be transmitted to the next snapshot cache satellite or the future same-track cache satellite according to the hop count between the current cache satellite and the next snapshot cache satellite, repeated content request to a ground server is avoided, waste of inter-satellite link resources caused by repeated back-and-forth transmission of the cache content between the tracks is reduced, and the scheme can further improve the network throughput and the cache hit rate under the condition of lower flow cost.
Furthermore, the network topology is partitioned, the similarity of request contents among the regions and the geographic distance are utilized, the region cache similarity is defined to measure the relation among the regions, and the set of similar regions is calculated through a clustering algorithm. And removing redundant cache contents for the similar areas, and preferentially searching contents among the similar areas if the cache of the area is not hit when the contents are requested. When the on-board storage is limited, the scheme can effectively reduce the cache redundancy and improve the network throughput and the cache hit rate.
Further, in the regular constellation network, the distance between the cache nodes of two continuous snapshots in the same area is judged according to the condition that the cache nodes of the two continuous snapshots in the same area are changed between adjacent orbits during topology switching, if the distance is one hop, part of popular contents are directly transmitted to the next snapshot cache node during snapshot switching, and otherwise, the contents are transmitted to a future cache satellite in the same orbit. The scheme avoids repeated content request to the ground server, and reduces inter-satellite link resource waste caused by repeated back-and-forth transmission of the cache content between the tracks.
Drawings
Fig. 1 is a flowchart of a content caching and distributing method based on regional collaboration in a satellite internet according to an embodiment of the present invention.
Fig. 2 is a schematic diagram of a satellite internet content caching and distribution network architecture according to an embodiment of the present invention.
Fig. 3 is a schematic diagram of content caching and distribution based on regional collaboration in the embodiment of the present invention.
Fig. 4 is a schematic diagram of cache content transmission according to an embodiment of the present invention.
Fig. 5 is a graph comparing content throughput in an embodiment of the present invention.
FIG. 6 is a graph comparing cache hit rates in embodiments of the invention.
Figure 7 is a comparison graph of average round trip delay in an embodiment of the present invention.
Fig. 8 is a comparison of traffic overhead in an embodiment of the invention.
FIG. 9 is a comparison graph of cache redundancy in an embodiment of the invention.
Detailed Description
The invention is described in further detail below with reference to the accompanying drawings:
as shown in fig. 1, a method for caching and distributing content based on regional collaboration in satellite internet includes the following steps:
s1, pre-calculating a cache node set of each snapshot and partitioning an LEO cache layer network topology by using a medium orbit satellite (MEO) through a satellite and ground network topology, and storing the cache node set and a topology partitioning result on the MEO satellite;
regarding the topology of equal time intervals as static, regarding the topology of each interval as an undirected graph G (V, E), wherein V represents the set of a satellite and a ground station, namely V (S U GS), E represents the set of all inter-satellite links and all satellite-ground links, and in each snapshot, calculating a routing and caching strategy according to the undirected graph G and other network information; calculating the shortest transmission path from the ground station to each LEO satellite by using a Dijkstra shortest path algorithm; the whole path set is a multi-branch tree structure and is composed of a plurality of subtrees. The ground station is used as the root node of the whole tree structure, and the nodes in the subtree, namely the request nodes, can obtain the requested content from the root node of the subtree to the ground station. In order to reduce the time delay of acquiring the content, a proper cache node is selected from the shortest path tree for caching the content, and the whole network topology is divided into a plurality of disjoint sub-trees T; the root node c of the subtree is used as a cache node of the area T (c) where the subtree is located and is responsible for providing content transmission for users covered by the area.
Selecting a cache node set according to the minimum distribution path delay, namely sequentially selecting a node with the minimum sum of path delays to other nodes in the network as a cache node set C ═ C1,c2,...,cCThe cache node obtained by the method can reduce the time delay from other nodes in the network to the cache node to acquire the content, and the calculation formula of the minimum distribution path time delay is as follows:
Figure BDA0003047263170000071
wherein, Td(i, j) is the propagation delay between node i and node j, Tp(i, j) is the transmission delay.
S2, collecting ground user request information in a fixed time interval through an LEO satellite, forming a list of requested probability of the content and sending the list to an MEO satellite;
a list of all content requested probabilities is maintained on each LEO satellite on the LEO layer satellite. For simplicity, we will divide the content into several categories, and let L kinds of content in the network, denoted as F ═ F1,f2,...,fL}. The request distribution of the content follows Zipf distribution, and the probability that the content with the popularity ranking I is requested is as follows:
Figure BDA0003047263170000072
in the formula, γ is a content distribution coefficient, and the larger γ is, the smaller the popular content set in the content set is, and the value range is [0.6, 1.2 ].
S3, calculating a cache strategy through user request information, a cache node set and a topology partitioning result collected by the MEO satellite and sending a cache plan to the LEO layer cache satellite;
in calculating the cache strategy, the MEO satellite preferentially adds the content with larger regional popularity in each region to the regional cache content set F according to the pre-calculated subareas by using the collected request probability informationc＝{f1.....fmaxIn the method, the maximum storable content number of the cached satellite is max, assuming that the storage space of the cached satellite is limited. The regional popularity of content f is shown in equation (3):
Figure BDA0003047263170000081
wherein
Figure BDA0003047263170000082
However, in order to reduce the redundancy of the cache contents, the relationship between the regions is considered, and for FcAnd further optimizing to form a final cache plan. Since the probability that the users with the closer distance request the same content is greater, the region cache similarity is defined, and not only the similarity of the requested content but also the distance between the regions are considered, as shown in formula (5):
Figure BDA0003047263170000083
Figure BDA0003047263170000084
where d (i, j) represents the distance between i and j. l (i, j) represents the similarity of requested contents between the regions, and the cosine similarity is used for calculation, as shown in formula (6), the calculation process is as follows:
(1) respectively finding out n content sets F most popular in the area i and the area ji＝{f1,f2...fnAnd Fj＝{f1,f2...fn}；
(2) Finding a union F of two sets of contentu＝Fi∪Fj；
(3) Respectively calculating F corresponding to the areas i and j according to the formula (3)uThe regional popularity of the middle content is obtained to obtain a vector PiAnd Pj；
(4) Finally, the content similarity l (i, j) between the region i and the region j can be obtained by the formula (6).
In order to find out a region set which is close in distance and similar in request content, all regions are clustered through a k-medoids clustering algorithm, wherein the distance metric is closeij. Regarding similar and similar areas as a virtual area, and setting F of cache content of each area in the virtual areacAnd optimizing to remove redundant cache contents. Under the limited storage space, the scheme can increase the diversity of the cache contents in each virtual area and reduce the repeated cache of the same contents in the same virtual area, and the optimization process is as follows:
(1) selecting region popularity Θ for popular and repeated contentfThe largest region and cached in the cached satellite for that region.
(2) And the content which is popular and is specific to the region is cached in the cache satellite of the region.
(3) Each regional cache node maintains an index table of a similar region, and if the request is not hit in the region, the request is sent to the similar regional cache node to acquire the content.
As shown in fig. 3, when a user requests content from an accessed LEO layer satellite, information Q (f) is requested1) Transmission over a satellite network. If the cache is hit in the region, the content is fed back to the user, otherwise, the content is fed back to the cache node s in the similar region1,kRequest content, eventually by responding to R (f)1) And feeding back the content to the user, and requesting the content from the ground server if the content is not found yet.
S4, the ground station sends the message of generating the content to the MEO satellite connected with the ground station, and informs the user through the MEO satellite broadcast;
s5, the user sends out content request and transfers it to the buffer satellite or ground server through LEO layer satellite;
the LEO satellites serve as a user access layer and a content cache layer, and each LEO satellite broadcasts access signals periodically, so that ground users can communicate with the LEO satellites directly.
S6, the LEO layer cache satellite caches the content of the response request of the cache satellite or the ground server according to the cache plan;
and S7, when the topology is switched, according to the hop count between the current cache satellite and the next snapshot cache satellite, determining to transmit part of popular content to the next snapshot cache satellite or the future same-orbit cache satellite for caching.
In order to avoid frequent requests for content from the server, part of the content is transmitted to the cache node of the next snapshot according to the access frequency from large to small (namely popular cache content), and then the updating is carried out according to the cache strategy, so that the request failure at the topology switching moment can be reduced. However, if the distance between two cache nodes in the same area of the continuous snapshot is greater than one hop, then transferring the content back and forth between the tracks for multiple times will result in waste of inter-satellite link resources. By using the characteristics of polar orbit constellation, on the basis of regional cooperative caching, the transmission of the caching content during snapshot switching is optimized:
(1) caching satellite s if k +1 snapshotj,k+1Caching satellite s by using distance k snapshoti,kOne jump, then snapshot switches to δ1Time, si,kDirect transmission of partially popular contentTo sj,k+1And updated during the k +1 snapshot according to a caching policy, δ1The calculation is as follows:
δ1＝qi,k·d(sj,k+1,si,k) (8)
wherein q isi,kIs si,kNumber of contents to be transmitted, d(s)j,k+1,si,k) Is the propagation delay between the two cached satellites.
(2) If sj,k+1And si,kMore than one hop apart, delta before k snapshot switches2Time, original buffer satellite si,kSending partially popular content to the same track k + Δ k1Snapshot caching satellite
Figure BDA0003047263170000101
If k +1 snapshot different orbit cache satellite sj,k+1Cached satellite s with k-1 snapshotn,k-1In the same orbit, the satellite s is illustratedj,k+1Has cached satellite sn,k-1Content of transmission, then satellite si,kNo longer to satellite sj,k+1Transmitting content, sj,k+1The update is done directly on the next snapshot. Finally, the original cache satellite s is deleted during snapshot switchingi,kBuffer contents of (1), δ2Is calculated as follows:
Figure BDA0003047263170000102
the content caching and distributing method based on regional collaboration in the satellite internet is based on a medium orbit satellite (MEO) and a low orbit satellite (LEO), wherein the MEO satellite is connected with a ground station and used for broadcasting a message for generating content and inquiring the content of the ground station, and meanwhile, the MEO satellite is also used for assisting the LEO satellite to perform routing calculation and caching strategy updating. Because the round-trip delay of the LEO satellite is low, the LEO satellite is used as a user access layer and a content cache layer. Each LEO satellite will periodically broadcast an access signal so that terrestrial users can communicate directly with the LEO satellite, denoted S ═ S1,s2,...,sS}. The ground station is located on the earth surface and is provided with a groundA server with stored content, denoted GS ═ GS, is deployed in the face station1,gs2,...,gsM}. The source node for all content requests of the satellite terminals, the ground users and the aerial vehicles is denoted as U ═ U1,u2,...,uU}. The process of content caching and distribution is illustrated by fig. 2.
(1) LEO satellite per deltatCollecting the request of the ground user at a time interval, and sending the request to the MEO satellite;
(2) the MEO satellite calculates and updates a cache plan, and sends the cache plan to the LEO layer cache satellite;
(3) the ground station generates content to inform the user through MEO satellite broadcast;
(4) on the way of returning the content, the LEO cache satellite selects the content to cache according to the cache plan;
(5) and when the topology is switched, the original cache satellite transmits part of cache contents to the next snapshot cache satellite or a future co-orbital cache satellite.
To explain the effect of the present invention, a network model is first built by using STK software, and relevant parameters of a satellite network are shown in table 1. In simulation, all contents are set to be the same in size, and the satellite cache space is limited. In order to approximately simulate the characteristics of the content requests on the earth surface distributed in different regions, the earth surface is divided into a plurality of regions with the same size, and each continent is approximately represented by a plurality of regions in the range by analyzing the longitude and latitude of each continent. Let us say that the content requests generated by each continent have regional characteristics and the request probability of each content within the continent is different. The proposed content caching scheme (RCC) based on regional collaboration, the scheme (RCCT) which optimizes inter-snapshot caching content transmission on the basis of the RCC, and the existing three schemes are contrastively analyzed. The compared performance indexes comprise network throughput, average round trip delay, cache hit rate, content transmission flow overhead, cache redundancy and the like.
The comparative protocol included the following three protocols:
on-satellite no-cache scheme (NC): according to the scheme, the content is not cached in the satellite network, and the user transmits a request to the ground server through the satellite network to obtain the content.
And a random caching scheme (RC) which uses the satellite network to cache contents, randomly selects C satellites as caching nodes at different moments, and simultaneously, supposes that the caching space of the caching satellites is limited and caches max contents at most.
Region-based caching scheme (RPC): the scheme divides the network, and the cache nodes in each area cache the max contents which are most popular in the area, but the areas do not cooperate with each other.
TABLE 1 satellite network parameters
Satellite parameters LEO layer MEO layer
Track type Polar orbit Walker
Inclination angle of track 86.4 55
Track height/km 780 26571
Number of satellites 66(6*11) 24(6*4)
As shown in fig. 5 and fig. 6, the RCC of our scheme can effectively improve the network throughput and the cache hit rate compared with three comparison schemes, namely RPC, RC and NC. This is because we realize cooperation between regions by using correlation between regions on the basis of region cache. And if the user does not hit the requested content in the local cache, acquiring the content through the adjacent similar area. And under the limited storage space, the RCC increases the diversity of the cache contents in the network, thereby improving the success rate of the user for acquiring the contents and responding more user requests in the same time. By optimizing content delivery between snapshots, RCCT further improves network throughput and cache hit rate.
In fig. 7, 8, the partition-based scheme has lower latency and traffic overhead than the non-partition schemes RC and NC in terms of average round trip latency and traffic overhead. The time delay of the RCC and the time delay of the RPC are close to each other, and the flow overhead is slightly increased. This is because we have removed the content that is duplicated between regions, and sometimes the user misses in this region, then needs to go to a similar region to get the content. But at the same time, the diversity of the cache contents in the network is increased, and the long time delay caused by the request of the user to the ground server is reduced. By optimizing content transfer between snapshots, RCCT is slightly reduced in time delay compared with RPC, and flow overhead caused by inter-region search is made up.
In fig. 9, it can be seen that, in the scheme RCC of the present application, the number of copies of cache contents in a network can be reduced while throughput and cache hit rate are improved, and cache redundancy is reduced. The RCC has better performance in situations where the cache satellite storage space is limited. However, the RCCT performs content delivery during snapshot switching, and sometimes the same orbiting satellite needs to temporarily store part of popular content in order to avoid multiple back-and-forth transmissions between orbits, so that the performance of the RCCT is improved and the redundancy of the cache is increased.

Claims (10)

1. A content caching and distributing method based on regional collaboration in satellite Internet is characterized by comprising the following steps:
s1, pre-calculating a cache node set of each snapshot and partitioning an LEO cache layer network topology by using a medium earth orbit satellite through a satellite and ground network topology, and storing the cache node set and a topology partitioning result on an MEO satellite;
s2, collecting ground user request information in a fixed time interval through an LEO satellite, forming a list of requested probability of the content and sending the list to an MEO satellite;
s3, calculating a cache strategy through user request information, a cache node set and a topology partitioning result collected by the MEO satellite and sending a cache plan to the LEO layer cache satellite;
s4, the ground station sends the message of generating the content to the MEO satellite connected with the ground station, and informs the user through the MEO satellite broadcast;
s5, the user sends out content request and transfers it to the buffer satellite or ground server through LEO layer satellite;
s6, the LEO layer cache satellite caches the content of the response request of the cache satellite or the ground server according to the cache plan;
and S7, when the topology is switched, according to the hop count between the current cache satellite and the next snapshot cache satellite, determining to transmit part of popular content to the next snapshot cache satellite or the future same-orbit cache satellite for caching.
2. The method according to claim 1, wherein topologies at equal time intervals are static, and the topology at each interval is regarded as an undirected graph G (V, E), where V denotes a set of satellites and ground stations, that is, V ═ S ═ GS, E denotes a set of all inter-satellite links and all satellite-ground links, and in each snapshot, a routing and caching strategy is calculated according to the undirected graph G and other network information.
3. The method as claimed in claim 2, wherein the Dijkstra shortest path algorithm is used to calculate the shortest transmission path from the ground station to each LEO satellite.
4. The content caching and distributing method based on regional collaboration in the satellite internet as claimed in claim 2, wherein a suitable caching node is selected from a shortest path tree for caching content, and the whole network topology is divided into a plurality of disjoint sub-trees T; the root node c of the subtree is used as a cache node of the area T (c) where the subtree is located and is responsible for providing content transmission for users covered by the area.
5. The method as claimed in claim 2, wherein the node with the smallest sum of path delays to other nodes in the network is selected in turn to join the cache node set C ═ C1,c2,...,cCThe cache node obtained by the method can reduce the time delay from other nodes in the network to the cache node to acquire the content, and the calculation formula of the minimum distribution path time delay is as follows:
Figure FDA0003047263160000021
wherein, Td(i, j) is the propagation delay between node i and node j, Tp(i, j) is the transmission delay.
6. The method as claimed in claim 1, wherein the MEO satellite preferentially adds the content with greater regional popularity in each region to the regional cache content set F according to the pre-computed partitions by using the collected request probability informationc＝{f1.....fmaxIn the method, the maximum storable content number of the cached satellite is max, assuming that the storage space of the cached satellite is limited.
7. The method as claimed in claim 1, wherein the content caching and distribution method based on regional collaboration in satellite internet is implemented by k-medoids clusteringThe method clusters all regions with a distance metric of closeijRegarding similar and similar areas as a virtual area, and setting the cache content F of each area in the virtual areacAnd optimizing to remove redundant cache contents.
8. The method as claimed in claim 1, wherein LEO satellites serve as a user access layer and a content caching layer, each LEO satellite broadcasts access signals periodically, and terrestrial users communicate with LEO satellites directly.
9. The method as claimed in claim 1, wherein when the user requests the content from the accessed LEO layer satellite, the request information Q (f) is requested1) Transmitting through satellite network, if the cache is hit in the local area, feeding back the content to the user, otherwise, feeding back the content to the cache node s in the similar area1,kRequest content, eventually by responding to R (f)1) And feeding back the content to the user, and requesting the content from the ground server if the content is not found yet.
10. The method for caching and distributing the content based on the regional collaboration in the satellite internet as claimed in claim 1, wherein the transmission of the cached content during snapshot switching is optimized as follows:
(1) caching satellite s if k +1 snapshotj,k+1Caching satellite s by using distance k snapshoti,kOne jump, then snapshot switches to δ1Time, si,kDirect transmission of partially popular content to sj,k+1And updated during the k +1 snapshot according to a caching policy, δ1The calculation is as follows:
δ1＝qi,k·d(sj,k+1,si,k) (8)
wherein q isi,kIs si,kNumber of contents to be transmitted, d(s)j,k+1,si,k) Is the propagation delay between two cached satellites;
(2) if sj,k+1And si,kMore than one hop apart, delta before k snapshot switches2Time, original buffer satellite si,kSending partially popular content to the same track k + Δ k1Snapshot caching satellite
Figure FDA0003047263160000031
If k +1 snapshot different orbit cache satellite sj,k+1Cached satellite s with k-1 snapshotn,k-1In the same orbit, the satellite s is illustratedj,k+1Has cached satellite sn,k-1Content of transmission, then satellite si,kNo longer to satellite sj,k+1Transmitting content, sj,k+1Updating is directly carried out on the next snapshot; finally, the original cache satellite s is deleted during snapshot switchingi,kBuffer contents of (1), δ2Is calculated as follows:
Figure FDA0003047263160000032
CN202110476523.3A 2021-04-29 2021-04-29 Content caching and distributing method based on regional collaboration in satellite Internet Active CN113365309B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN202110476523.3A CN113365309B (en) 2021-04-29 2021-04-29 Content caching and distributing method based on regional collaboration in satellite Internet

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN202110476523.3A CN113365309B (en) 2021-04-29 2021-04-29 Content caching and distributing method based on regional collaboration in satellite Internet

Publications (2)

Publication Number Publication Date
CN113365309A true CN113365309A (en) 2021-09-07
CN113365309B CN113365309B (en) 2023-03-28

Family

ID=77525715

Family Applications (1)

Application Number Title Priority Date Filing Date
CN202110476523.3A Active CN113365309B (en) 2021-04-29 2021-04-29 Content caching and distributing method based on regional collaboration in satellite Internet

Country Status (1)

Country Link
CN (1) CN113365309B (en)

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104683016A (en) * 2015-03-15 2015-06-03 西安电子科技大学 Method for distributing and routing optimal services of multi-layer satellite network based on minimum time delay
WO2015153587A1 (en) * 2014-03-31 2015-10-08 Intelsat Corporation Multichannel content distribution via satellite to broadcast-capable mobile networks
CA2927217A1 (en) * 2016-04-14 2017-10-14 Telesat Canada Dual leo satellite system and method for global coverage
CN109412950A (en) * 2018-10-12 2019-03-01 哈尔滨工业大学（深圳） Data distributing method of the star ground based on on-path caching in hybrid network

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2015153587A1 (en) * 2014-03-31 2015-10-08 Intelsat Corporation Multichannel content distribution via satellite to broadcast-capable mobile networks
CN106165319A (en) * 2014-03-31 2016-11-23 国际通信卫星公司 Via satellite by multichannel content distribution to the mobile network with broadcast-capable
US20170085328A1 (en) * 2014-03-31 2017-03-23 Intelsat Corporation Multichannel content distribution via satellite to broadcast-capable mobile networks
CN104683016A (en) * 2015-03-15 2015-06-03 西安电子科技大学 Method for distributing and routing optimal services of multi-layer satellite network based on minimum time delay
CA2927217A1 (en) * 2016-04-14 2017-10-14 Telesat Canada Dual leo satellite system and method for global coverage
CN109412950A (en) * 2018-10-12 2019-03-01 哈尔滨工业大学（深圳） Data distributing method of the star ground based on on-path caching in hybrid network

Non-Patent Citations (4)

* Cited by examiner, † Cited by third party
Title
ERBAO WANG等: "Content Placement Based on Utility Function for Satellite Networks", 《IEEE》, 20 November 2019 (2019-11-20) *
戴翠琴等: "星地融合通信中的卫星回传技术", 《移动通信》, no. 09, 15 September 2020 (2020-09-15) *
祝振凱等: "基于链路信息的卫星网络最优路径选择策略", 《计算机工程与科学》 *
祝振凱等: "基于链路信息的卫星网络最优路径选择策略", 《计算机工程与科学》, no. 03, 15 March 2017 (2017-03-15) *

Also Published As

Publication number Publication date
CN113365309B (en) 2023-03-28

Similar Documents

Publication Publication Date Title
CN110493130B (en) Dynamic and static hybrid routing method for heaven-earth integrated network
CN111342885B (en) Gateway station combination-based satellite network routing method
WO2022105621A1 (en) Evolutionary game-based multi-user switching method in software-defined satellite network system
CN110730131A (en) SDN satellite network multi-QoS constraint routing method based on improved ant colony
CN107094047B (en) Double-layer satellite network routing method based on packet data pre-storage and segmented transmission
CN111148069A (en) Air-ground integrated Internet of vehicles information transmission method based on fog calculation and intelligent traffic
CN112953625B (en) Super-large-scale low-orbit satellite network operation and maintenance and resource control method
Lyu et al. Optimal computation offloading in collaborative leo-iot enabled mec: A multi-agent deep reinforcement learning approach
CN109672625A (en) A kind of the low orbit satellite feed load-balancing method and system of optimization time delay
Park et al. Mobility-aware distributed proactive caching in content-centric vehicular networks
CN114666843A (en) Cooperative caching method in layered network architecture
Liu et al. Routing for predictable multi-layered satellite networks
CN113365309B (en) Content caching and distributing method based on regional collaboration in satellite Internet
CN114158106A (en) Distributed routing method, device and storage medium for satellite network
Tang et al. Content-Aware Routing based on Cached Content Prediction in Satellite Networks
Li et al. LEO Mega-Constellations Routing Algorithm Based on Area Segmentation
Hao et al. Cooperative Regional Caching and Distribution in Space-Terrestrial Integrated Networks
US20020126623A1 (en) Method for decentralized transmission and distribution of user data between subscribers in a telecommunications network
Wang et al. Task assignment strategy in LEO-muti-access edge computing based on matching game
Yang et al. A synergic architecture for content distribution in integrated satellite and terrestrial networks
CN109412950B (en) On-path cache-based data distribution method in satellite-ground hybrid network
Iqbal Cache-MCDM: A hybrid caching scheme in Mobile Named Data Networks based on multi-criteria decision making
Lyu et al. Ndn-based multimedia content distribution in space-ground integration network
CN115102608B (en) Cooperative multicast method based on high-low orbit double-layer satellite network
Urquizo Medina et al. QoS routing for LEO satellite networks

Legal Events

Date Code Title Description
PB01 Publication
PB01 Publication
SE01 Entry into force of request for substantive examination
SE01 Entry into force of request for substantive examination
GR01 Patent grant
GR01 Patent grant