CN109039706B - Fog wireless access network collaboration content deployment method based on graph theory - Google Patents
Fog wireless access network collaboration content deployment method based on graph theory Download PDFInfo
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Abstract
The invention discloses a method for deploying cooperation contents of a fog wireless access network based on graph theory, which comprises the following steps: (1) cooperative caching according to access stratumThe cluster set is used for constructing a popular content set of each cooperative cache cluster and a popular content set of each non-cluster node; (2) constructing a connection edge set of the fog wireless nodes of the access layer according to the distance and the load difference between the fog wireless nodes and the affiliated cooperative cache cluster(3) According to connected edge setsConstructing access layer adjacency list set(4) According to collectionsObtainingRedundant content set corresponding to each edge in the content(5) From redundant content setsComputingThe cache decision correction indicating quantity of the redundant content corresponding to each edge; (6) calculating a cache decision correction indicating quantity of each cooperative cache cluster; (7) calculating a cache decision correction indicating quantity of each non-cluster fog wireless access node; (8) a final caching decision is calculated. The method and the device determine the caching decision of the F-AP in the fog wireless access network in a cooperative mode, and have low calculation complexity and higher total front-loading capacity.
Description
Technical Field
The invention relates to a content deployment method, in particular to a fog wireless access network collaborative content deployment method based on graph theory.
Background
As a novel system architecture of a 5G communication system, a Fog-Radio Access Network (F-RAN) has attracted wide attention in the field of communication with its great advantages in relieving forward congestion and reducing communication delay. A Fog-radio Access node F-AP (Fog-Access Point) in the F-RAN can cache popular content in advance at off-peak times, which is the key to achieving fronthaul offload. But the storage space of the F-AP is limited, and the content popularity distribution over the coverage area of the F-AP is more dispersed, and the edge cache performance gain of the F-RAN is thus greatly limited. The adjacent cooperative nodes are considered, the content is deployed in a cooperative mode, the content diversity is improved, the cache redundancy is eliminated, the locally acquired requested content is increased, and the cooperative cache can bring great help for further improving the performance gain of the 5G system.
The problem of cooperative content deployment is an NP-hard problem, a global optimal solution can be obtained by using a dynamic programming method, but the time complexity of the method is exponential time complexity. The approximate solution proposed in the past mainly converts the content deployment optimization problem into a monotone sub-model function optimization problem limited by pseudo-array constraint, and then proposes a greedy algorithm to solve the converted problem. When the method is applied, a complex calculation process is needed to evaluate the marginal value of the objective function, and the time complexity of the method is high-order polynomial time complexity related to the number of cache nodes and the size of the content library. Since the content library size is usually very large, in the fog wireless access network, the F-APs are distributed more densely, and therefore, it is necessary to provide a more efficient collaborative content deployment method.
Disclosure of Invention
The purpose of the invention is as follows: aiming at the problems in the prior art, the invention provides a method for deploying the cooperative content of the fog wireless access network based on the graph theory.
The technical scheme is as follows: the invention discloses a method for deploying cooperation contents of a fog wireless access network based on graph theory, which comprises the following steps:
(1) according to the cooperative cache cluster set of the access layer, constructing the popular content set of each cooperative cache cluster nAnd a popular content set for each non-clustered fog wireless access node iN is 1, …, N, I is 1, …, I, N, I respectively represent the number of the cooperative cache cluster and the non-cluster fog wireless access nodes;
(2) constructing a connection edge set epsilon of the fog wireless nodes of the access layer according to the distance and the load difference between the fog wireless nodes and the cooperative cache cluster to which the fog wireless nodes belongr;
(4) According to access layer adjacency list setObtaining epsilonrRedundant content set corresponding to each edge in the content
(5) From redundant content setsCalculating epsilonrThe cache decision correction indicating quantity of the redundant content corresponding to each edge;
(6) calculating a cache decision correction indicating quantity corresponding to each cooperative cache cluster n according to the updated popular content set of the cooperative cache clusters in the step (5);
(7) calculating a cache decision correction indicating quantity corresponding to each non-cluster fog wireless access node according to the cache decision correction indicating quantity obtained in the step (5);
(8) and (5) calculating a final cache decision according to the cache decision correction indicating quantity obtained in the steps (5) to (7).
Further, the step (1) specifically comprises:
(1.1) Aggregating access stratum fog wireless access pointsThe nodes in the cluster are divided into N cooperative cache clusters, and non-clustered fog wireless nodes form a non-cluster fog wireless node set
(1.2) selecting the nth cooperative cache cluster, and calculating the content libraryPer content to a cooperative cache cluster nnfAnd according to the intra-cluster request probability pnfSorting in descending order by SnKmThe individual content serves as a popular content collection of a cooperative cache cluster nWherein the probability of requests p in a clusternfThe calculation formula of (A) is as follows:
in the formula (I), the compound is shown in the specification,representing a set of fog wireless access nodes, p, comprised in a cooperative cache cluster nmfF-AP (radio access node) for representing fogmThe probability of a request for content f over the coverage area,λmF-AP (radio access node) for representing fogmRequest arrival rate of SnRepresenting the number of misty wireless access nodes, K, in a cooperative cache cluster nmF-AP (radio access node) for representing fogmThe number of contents that can be cached;
(1.3) repeatedly executing other cooperative cache clusters according to the step (1.2) until a popular content set of each cooperative cache cluster is obtained;
(1.4) selecting the ith non-cluster fog wireless access nodeComputing content libraryFor each non-cluster-fog wireless access node F-APiRequest probability p ofifAnd according to the request probability pifSorting in descending order, the first KiA set of most popular contentWherein, KiF-AP (radio access node) for representing fogiThe number of contents that can be cached;
and (1.5) repeatedly executing other non-cluster-fog wireless access nodes according to the step (1.4) until the popular content set of each non-cluster-fog wireless access node is obtained.
Further, the step (2) specifically comprises:
(2.1) initializing the connected edge set εrIs an empty set;
(2.2) selecting a set of Access stratum fog wireless Access pointsMiddle mth node F-APmPerforming the following operations:
obtaining the m' th node F-APm'M', M ═ M + 1., M denotes the number of the fog wireless access points, and it is determined whether the following conditions are satisfied:
a、Dmm'≤γd,Lmm'≥γl(ii) a Wherein D ismm′=||dm-dm′||2,dmAnd dm′Respectively represent fog wireless access nodes F-APmAnd F-APm'Coordinates in Euclidean space, Lmm′=||λm-λm′||2,λmAnd λm′Respectively representing fog wireless accessNode F-APmAnd F-APm'Request arrival rate, gamma, over coverage areadThreshold, gamma, representing the distance between the fog radio access nodeslA threshold representing a load difference, | · | | non-conducting phosphor2Represents the L2 norm operator;
b. node F-APmAnd node F-APm'Not in the same cooperative cache cluster;
if conditions a and b are satisfied simultaneously, the edges (F-AP) will be connectedm,F-APm') Adding to the set εrPerforming the following steps;
(2.3) for fog Wireless Access Point setAnd (5) repeatedly executing other nodes according to the step (2.2) until the fog wireless access point set is traversedAll the nodes are in the state of being in order to obtain the final connection edge set epsilonr。
Further, the step (3) specifically comprises:
(3.1) set of Wireless Access points to Access stratum fogM-th node in (F-AP)mBuilding its neighbor list set
(3.2) eliminating the adjacent table sets with the element number of 1 from the adjacent table sets of all F-AP nodes, and sequencing the rest adjacent table sets in a descending order according to the element number in the sets to obtain setsWherein H isThe number of the elements in the Chinese character 'Zhongqin'.
Further, the step (4) specifically comprises:
A. obtainingJ element of F-APk,jWith the first element F-APk,1The repeated popular content set corresponding to the connection edge e is obtained according to the following criteria
In the formula (I), the compound is shown in the specification,representing a set of fog wireless access nodes included in the cooperative cache cluster n,representing a non-clustered fog set of wireless nodes Denotes F-APk,jJ2, …, Jk,JkTo representThe number of middle elements;
B. for adjacency list setIs repeatedly executed (4.1), thereby obtaining a repeated popular content set corresponding to each connecting edge
for theJ element of F-APk,jInitialization of Kk,j=KmK, where J is 1, …, Jk,JkTo representThe number of medium elements, m represents a fog wireless access node F-APk,jIn the collectionThe sequence number in (1), M belongs to { 1.,. M }, M denotes the number of the fog wireless access nodes, K denotes the number of the fog wireless access nodes, andk,jand KmAll represent fog wireless access node F-APk,jK represents the maximum available storage space size of the fog wireless access node;
A. cumulative calculationJ element of F-APk,jWith the first element F-APk,1The intersection of the sets of repeated popular content corresponding to the connecting edges of
B. If it isThen for the collectionJ element of F-APk,jWith the first element F-APk,1E, from the setIn random selection of Kk,1The content forms a redundant content set corresponding to the edge eAnd based on redundant content setsUpdating Kk,jUpdate the corresponding KmAnd other fog wireless access nodes with the sequence number m are F-APk',j'(k'>k,j'∈{1,...,Jk'}) available memory space Kk',j'Is updated to KmAnd updating the connection F-APk,jE' ≠ e corresponding repeated popular content setWherein J is 2, …, Jk;
C. If it isThen for the collectionJ element of F-APk,jWith the first element F-APk,1E, from the setIn the random selectionContent, together with collectionsAll contents in (1) constitute a redundant content set corresponding to the edge eAnd based on redundant content setsUpdating Kk,jUpdate the corresponding KmAnd other fog wireless access nodes with the sequence number m are F-APk',j'(k'>k,j'∈{1,...,Jk'}) available memory space Kk',j'Is updated to KmAnd updating the connection F-APk,jE' ≠ e corresponding repeated popular content setWherein J is 2, …, Jk;
D. For adjacency list setRepeat (4.3) to obtain a redundant content set corresponding to each connecting edge
Further, the step (5) specifically comprises:
for theJ element of F-APk,jReset Kk,j=KmK, where J is 1, …, Jk,JkTo representThe number of medium elements, m represents a fog wireless access node F-APk,jIn the collectionThe sequence number in (1), M belongs to { 1.,. M }, M denotes the number of the fog wireless access nodes, K denotes the number of the fog wireless access nodes, andk,jand KmAll represent fog wireless access node F-APk,jK represents the maximum available storage space size of the fog wireless access node;
to the collectionMiddle j element F-APk,jWith the first element F-APk,1Redundant content set corresponding to the connecting edge e ofThe following four-step operation is performed, J is 2, …, and Jk,JkTo representThe number of the medium elements is as follows:
is in the collectionWherein the cache location is found in the F-APk,1The content of (1), the content of the part is not allowed to be cached in the F-APk,jTo avoid cache redundancy, the F-AP is switched onk,jCorresponding cache decision correction indicator Δ xk,j,fSet to-1, i.e.: Δ xk,j,f=-1,And to aggregate such content from collectionsWherein the cache decision correction indicator Δ xk,j,f1 indicates that the buffer location of the content F is in the F-APk,j;
② in the collectionDoes not allow for finding a cache location in the F-APk,1The part of the content has to be cached in the F-APk,jThen F-AP is setk,jCorresponding cache decision correction indicator Δ xk,j,fSet to 1, namely: Δ xk,j.f=1,And is arranged atWhen it is time to assemble these contents from the collectionRemoving and updating Kk,jUpdate the corresponding KmAnd other fog wireless access nodes with the sequence number m are F-APk',j'(k'>k,j'∈{1,...,Jk'}) available memory space Kk',j'Is updated to KmFrom the collection of these contentsRemoving; wherein, the cache decision correction indication quantity Deltaxk,1,fCache location of presentation content F at-1 is not allowed at F-APk,1;
Respectively calculating the setsIn (3) caching in the F-APk,1Available fronthaul unload capacityAnd will aggregateIn (3) caching in the F-APk,jAvailable fronthaul unload capacityWherein:
in the formula (II)Represents all satiations (F-AP)m,F-APk,1)∈εrOr (F-AP)k,1,F-APm)∈εrFog wireless access node F-APmSet of constructs, setRepresents all satiations (F-AP)m,F-APk,j)∈εrOr (F-AP)k,j,F-APm)∈εrFog wireless access node F-APmSet of formations, λm'F-AP (radio access node) for representing fogm'Request arrival rate of (p)m'fF-AP (radio access node) for representing fogm'Probability of request for content f over the coverage area, L representing the size of each content;
fourthly ifThen set upThe remaining content is cached in the F-APk,1Higher forward unload capacity can be obtained, F-APk,1Setting the corresponding cache decision correction indication quantity to be 1, F-APk,jThe corresponding cache decision correction indication quantity is set to-1, namely: Δ xk,1.f=1,Δxk,j.f=-1,And is arranged atWhen it is time to assemble these contents from the collectionRemoving and updating Kk,1Update the corresponding KmAnd other fog wireless access nodes with the sequence number m are F-APk',j'(k'>k,j'∈{1,...,Jk'}) available memory space Kk',j'Is updated to Km(ii) a If it isThen set upThe remaining content is cached in the F-APk,jHigher forward unload capacity can be obtained, F-APk,1Setting the corresponding cache decision correction indication quantity to-1, F-APk,jThe corresponding cache decision correction indication amount is set to 1, that is: Δ xk,j.1=-1,Δxk,j.f=1,And is arranged atWhen it is time to assemble these contents from the collectionRemoving and updating Kk,jUpdate the corresponding KmAnd other fog wireless access nodes with the sequence number m are F-APk',j'(k'>k,j'∈{1,...,Jk'}) available memory space Kk',j'Is updated to Km;
(5.3) for adjacency list setRepeating the step (5.2) to obtain epsilonrAnd correcting the indication quantity of the cache decision of the redundant content corresponding to each edge.
Further, the step (6) specifically comprises:
(6-1) for the nth cooperative cache cluster, performing the following steps:
A. F-AP for the ith fog wireless access node in the nth cooperation cache clustern,lIf, ifThen will beAll the cache positions are selected in the F-APn,lCorresponding cache decision correction indicator Δ xn,l,fSet to 1, namely:if it isThen fromMedium random selectionLet Kn,lAnd then F-APn,lCorresponding cache decision correction indicator Δ xn,l,fSetting as 1; updating Kn,lAnd selecting the selected content from the collectionRemoving; wherein, Δ xn,l,f0 indicates that it is impossible to determine whether or not the cache position of the content F is in the foggy wireless access node F-APn,l,Kn,lDenotes F-APn,lL is 1, …, Ln represents the number of nodes in the cooperative cache cluster n;
B. for F-APn,lIf K isn,l> 0, then from the setIn random selection of Kn,lAnd correcting the corresponding cache decision by the indicated quantity delta xn,l,fSet to 1, update Kn,lAnd selecting the selected content from the collectionRemoving; otherwise, not processing; wherein, l is 1, …, Ln;
and (6.2) repeatedly executing other cooperative cache clusters according to the step (6.1) until the cache decision correction indicating quantity corresponding to each cooperative cache cluster is obtained.
Further, the step (7) specifically comprises:
(7.1) for non-cluster fog wireless node setThe ith element F-AP of (1)iThe following steps are carried out:
if KiIf > 0, then assembleAccording to the request probability pifSorting in descending order, selecting top KiAccording to the content, the corresponding cache decision is corrected by the indication quantity delta xifSetting as 1; otherwise, the operation is not executed; wherein the content of the first and second substances,Kidenotes F-APiThe available storage space of (a) is,representing the entire content set, Δ xm′fThe cache position of the content F is shown in the F-APm',Indicates all the satisfaction (AP)m,APi)∈εrOr (AP)i,APm)∈εrFog wireless access node APmA set of constructs;
(7.2) for non-clustered fog Wireless node setsAnd (7.1) repeatedly executing other elements to obtain the corresponding cache decision correction indication quantity of each non-cluster fog wireless access node.
Further, the step (8) specifically comprises:
(8.1) selecting a set of access stratum fog wireless access pointsM-th node in (F-AP)mThe following steps are executed:
finding cache location is at F-APmIn the F-AP, the contents are stored in the F-APmThe final caching decision of (1) is set to 1, that is: x is the number ofmf=1,f∈{f|Δxmf1} and the rest is in the F-APmIs set to 0, i.e.:wherein the content of the first and second substances,representing the entire content set, xmfRepresentative content F at F-APmFinal caching decision;
(8.2) Wireless Access Point set for Access stratum fogAnd (8.1) repeating the steps so as to obtain the final caching decision of each fog wireless access node.
Has the advantages that: compared with the prior art, the invention has the following remarkable advantages:
1. by constructing the adjacency list set of the vertexes, the situation that the same edge is repeatedly constructed in different vertex pair sequences is avoided, and the subsequent large amount of calculation related to the edge can be avoided from being repeated, so that the calculation is simplified from the source;
2. on the basis of determining the repeated popular content set corresponding to each edge, the redundant content set corresponding to each edge is further determined by combining the storage space size of the fog wireless access node, so that the content which does not cause cache redundancy in the repeated popular content is indirectly eliminated, and the calculation is further simplified;
3. when the redundant content set of one edge is determined, the contents are removed from the repeated popular content sets corresponding to the other edges connected with the top points of the edge, so that twice caching decision correction on the same content on the same fog wireless access node is guaranteed, and the calculation is further simplified;
4. in a staged mode, firstly, an intra-cluster content set and a non-cluster node popular content set which can enable the uploading unloading increment of the intra-cluster cooperation to be maximum are found, then the caching decision of the repeated popular content which affects the uploading unloading amount of the inter-cluster cooperation and the non-cluster node cooperation is corrected, at the moment, the cache decision correction indicating amount can be simultaneously determined by a plurality of repeated popular contents meeting the characteristics of the cache position, the cache position of each content does not need to be calculated iteratively, and the whole process greatly simplifies the calculation of the collaborative content deployment with the maximum total uploading unloading amount.
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FIG. 1 is a diagram of an application scenario of the present invention;
FIG. 2 is a schematic flow chart of the present invention.
Detailed Description
The embodiment provides a graph theory-based fog wireless access network cooperationThe application scenario of the content deployment method is shown in fig. 1, H F-APs exist in an access layer of a fog wireless access network, and all the F-APs form a setAs shown in fig. 2, the method comprises the steps of:
(1) according to the cooperative cache cluster set of the access layer, constructing the popular content set of each cooperative cache cluster nAnd a popular content set for each non-clustered fog wireless access node iN is 1, …, N, I is 1, …, I, N, I respectively indicate the number of cooperative cache clusters and non-cluster-misty wireless access nodes. The method specifically comprises the following steps:
(1.1) aggregating access stratum fog wireless access pointsThe nodes in the cluster are divided into N cooperative cache clusters, and non-clustered fog wireless nodes form a non-cluster fog wireless node set
(1.2) selecting the nth cooperative cache cluster, and calculating the content libraryPer content to a cooperative cache cluster nnfAnd according to the intra-cluster request probability pnfSorting in descending order by SnKmThe individual content serves as a popular content collection of a cooperative cache cluster nWherein the probability of requests p in a clusternfThe calculation formula of (A) is as follows:
in the formula (I), the compound is shown in the specification,representing a set of fog wireless access nodes, p, comprised in a cooperative cache cluster nmfF-AP (radio access node) for representing fogmThe probability of a request for content f over the coverage area,λmF-AP (radio access node) for representing fogmRequest arrival rate of SnRepresenting the number of misty wireless access nodes, K, in a cooperative cache cluster nmF-AP (radio access node) for representing fogmThe number of contents that can be cached;
(1.3) repeatedly executing other cooperative cache clusters according to the step (1.2) until a popular content set of each cooperative cache cluster is obtained;
(1.4) selecting the ith non-cluster fog wireless access nodeComputing content libraryFor each non-cluster-fog wireless access node F-APiRequest probability p ofifAnd according to the request probability pifSorting in descending order, the first KiA set of most popular contentWherein, KiF-AP (radio access node) for representing fogiThe number of contents that can be cached;
and (1.5) repeatedly executing other non-cluster-fog wireless access nodes according to the step (1.4) until the popular content set of each non-cluster-fog wireless access node is obtained.
(2) Constructing an access layer according to the distance and the load difference between the fog wireless nodes and the cooperative cache cluster to which the fog wireless nodes belongConnection edge set epsilon of fog wireless noder。
The method specifically comprises the following steps:
(2.1) initializing the connected edge set εrIs an empty set;
(2.2) selecting a set of Access stratum fog wireless Access pointsMiddle mth node F-APmPerforming the following operations:
obtaining the m' th node F-APm'M', M ═ M + 1., M denotes the number of the fog wireless access points, and it is determined whether the following conditions are satisfied:
a、Dmm'≤γd,Lmm'≥γl(ii) a Wherein D ismm′=||dm-dm′||2,dmAnd dm′Respectively represent fog wireless access nodes F-APmAnd F-APm'Coordinates in Euclidean space, Lmm′=||λm-λm′||2,λmAnd λm′Respectively represent fog wireless access nodes F-APmAnd F-APm'Request arrival rate, gamma, over coverage areadThreshold, gamma, representing the distance between the fog radio access nodeslA threshold representing a load difference, | · | | non-conducting phosphor2Represents the L2 norm operator;
b. node F-APmAnd node F-APm'Not in the same cooperative cache cluster;
if conditions a and b are satisfied simultaneously, the edges (F-AP) will be connectedm,F-APm') Adding to the set εrPerforming the following steps;
(2.3) for fog Wireless Access Point setAnd (5) repeatedly executing other nodes according to the step (2.2) until the fog wireless access point set is traversedAll the nodes are in the state of being in order to obtain the final connection edge set epsilonr。
(3) According to the connection edge set epsilonrBuilding access layer adjacency list setThe method specifically comprises the following steps:
(3.1) set of Wireless Access points to Access stratum fogM-th node in (F-AP)mBuilding its neighbor list set
(3.2) eliminating the adjacent table sets with the element number of 1 from the adjacent table sets of all F-AP nodes, and sequencing the rest adjacent table sets in a descending order according to the element number in the sets to obtainWherein H isThe number of the elements in the Chinese character 'Zhongqin'.
(4) According to access layer adjacency list setObtaining epsilonrRedundant content set corresponding to each edge in the contentThe method specifically comprises the following steps:
A. obtainingJ element of F-APk,jWith the first element F-APk,1The repeated popular content set corresponding to the connection edge e is obtained according to the following criteria
In the formula (I), the compound is shown in the specification,representing a set of fog wireless access nodes included in the cooperative cache cluster n,representing a non-clustered fog set of wireless nodes Denotes F-APk,jJ2, …, Jk,JkTo representThe number of middle elements;
B. for adjacency list setIs repeatedly executed (4.1), thereby obtaining a repeated popular content set corresponding to each connecting edge
for theJ element of F-APk,jInitialization of Kk,j=KmK, where J is 1, …, Jk,JkTo representThe number of medium elements, m represents a fog wireless access node F-APk,jIn the collectionThe sequence number in (1), M belongs to { 1.,. M }, M denotes the number of the fog wireless access nodes, K denotes the number of the fog wireless access nodes, andk,jand KmAll represent fog wireless access node F-APk,jK represents the maximum available storage space size of the fog wireless access node;
A. cumulative calculationJ element of F-APk,jWith the first element F-APk,1The intersection of the sets of repeated popular content corresponding to the connecting edges of
B. If it isThen for the collectionJ element of F-APk,jWith the first element F-APk,1E, from the setIn random selection of Kk,1The content forms a redundant content set corresponding to the edge eAnd based on redundant content setsUpdating Kk,jUpdate the corresponding KmAnd other fog wireless access nodes with the sequence number m are F-APk',j'(k'>k,j'∈{1,...,Jk'}) available memory space Kk',j'Is updated to KmAnd updating the connection F-APk,jE' ≠ e corresponding repeated popular content setWherein J is 2, …, Jk;
C. If it isThen for the collectionJ element of F-APk,jWith the first element F-APk,1E, from the setIn the random selectionContent, together with collectionsAll contents in (1) constitute a redundant content set corresponding to the edge eAnd based on redundant content setsUpdating Kk,jUpdate the corresponding KmAnd other fog wireless access nodes with the sequence number m are F-APk',j'(k'>k,j'∈{1,...,Jk'}) available memory space Kk',j'Is updated to KmAnd updating the connection F-APk,jE' ≠ e corresponding repeated popular content setWherein J is 2, …, Jk;
D. For adjacency list setRepeat (4.3) to obtain a redundant content set corresponding to each connecting edge
(5) From redundant content setsCalculating epsilonrAnd correcting the indication quantity of the cache decision of the redundant content corresponding to each edge. The method specifically comprises the following steps:
for theJ element of F-APk,jReset Kk,j=KmK, where J is 1, …, Jk,JkTo representThe number of medium elements, m represents a fog wireless access node F-APk,jIn the collectionThe sequence number in (1), M belongs to { 1.,. M }, M denotes the number of the fog wireless access nodes, K denotes the number of the fog wireless access nodes, andk,jand KmAll represent fog wireless access node F-APk,jK represents the maximum available storage space size of the fog wireless access node;
to the collectionMiddle j element F-APk,jWith the first element F-APk,1Redundant content set corresponding to the connecting edge e ofThe following four-step operation is performed, J is 2, …, and Jk,JkTo representThe number of the medium elements is as follows:
is in the collectionWherein the cache location is found in the F-APk,1The content of (1), the content of the part is not allowed to be cached in the F-APk,jTo avoid cache redundancy, the F-AP is switched onk,jCorresponding cache decision correction indicator Δ xk,j,fSet to-1, i.e.: Δ xk,j,f=-1,And to aggregate such content from collectionsWherein the cache decision correction indicator Δ xk,j,f1 indicates that the buffer location of the content F is in the F-APk,j;
② in the collectionDoes not allow for finding a cache location in the F-APk,1The part of the content has to be cached in the F-APk,jThen F-AP is setk,jCorresponding cache decision correction indicator Δ xk,j,fSet to 1, namely: Δ xk,j.f=1,And is arranged atWhen it is time to assemble these contents from the collectionRemoving and updating Kk,jUpdate the corresponding KmAnd other fog wireless access nodes with the sequence number m are F-APk',j'(k'>k,j'∈{1,...,Jk'}) available memory space Kk',j'Is updated to KmFrom the collection of these contentsRemoving; wherein, the cache decision correction indication quantity Deltaxk,1,fCache location of presentation content F at-1 is not allowed at F-APk,1;
Respectively calculating the setsIn (3) caching in the F-APk,1Available fronthaul unload capacityAnd will aggregateIn (3) caching in the F-APk,jAvailable fronthaul unload capacityWherein:
in the formula (II)Represents all satiations (F-AP)m,F-APk,1)∈εrOr (F-AP)k,1,F-APm)∈εrFog wireless access node F-APmSet of constructs, setRepresents all satiations (F-AP)m,F-APk,j)∈εrOr (F-AP)k,j,F-APm)∈εrFog wireless access node F-APmSet of formations, λm'F-AP (radio access node) for representing fogm'Request arrival rate of (p)m'fF-AP (radio access node) for representing fogm'Probability of request for content f over the coverage area, L representing the size of each content;
fourthly ifThen set upThe remaining content is cached in the F-APk,1Higher forward unload capacity can be obtained, F-APk,1Setting the corresponding cache decision correction indication quantity to be 1, F-APk,jThe corresponding cache decision correction indication quantity is set to-1, namely: Δ xk,j.1=1,Δxk,j.f=-1,And is arranged atWhen it is time to assemble these contents from the collectionIn the process of removing and updating the corresponding KmAnd other fog wireless access nodes with the sequence number m are F-APk',j'(k'>k,j'∈{1,...,Jk'}) available memory space Kk',j'Is updated to Km(ii) a If it isThen set upThe remaining content is cached in the F-APk,jHigher forward unload capacity can be obtained, F-APk,1Setting the corresponding cache decision correction indication quantity to-1, F-APk,jThe corresponding cache decision correction indication amount is set to 1, that is: Δ xk,j.1=-1,Δxk,j.f=1,And is arranged atWhen it is time to assemble these contents from the collectionRemoving and updating Kk,jUpdate the corresponding KmAnd other fog wireless access nodes with the sequence number m are F-APk',j'(k'>k,j'∈{1,...,Jk'}) available memory space Kk',j'Is updated to Km;
(5-3) for adjacency list setRepeating the step (5-2) to obtain epsilonrAnd correcting the indication quantity of the cache decision of the redundant content corresponding to each edge.
(6) And (5) calculating the corresponding cache decision correction indication quantity of each cooperative cache cluster n according to the updated popular content set of the cooperative cache clusters. The method specifically comprises the following steps:
(6-1) for the nth cooperative cache cluster, performing the following steps:
A. F-AP for the ith fog wireless access node in the nth cooperation cache clustern,lIf, ifThen will beAll the cache positions are selected in the F-APn,lCorresponding cache decision correction indicator Δ xn,l,fSet to 1, namely:if it isThen fromIn the random selection of Kn,lAnd then F-APn,lCorresponding cache decision correction indicator Δ xn,l,fSetting as 1; updating Kn,lAnd will be selectedContent slave collectionsRemoving; wherein, Δ xn,l,f0 indicates that it is impossible to determine whether or not the cache position of the content F is in the foggy wireless access node F-APn,l,Kn,lDenotes F-APn,lL is 1, …, Ln represents the number of nodes in the cooperative cache cluster n;
B. for F-APn,lIf K isn,l> 0, then from the setIn random selection of Kn,lAnd correcting the corresponding cache decision by the indicated quantity delta xn,l,fSet to 1, update Kn,lAnd selecting the selected content from the collectionRemoving; otherwise, not processing; wherein, l is 1, …, Ln;
and (6.2) repeatedly executing other cooperative cache clusters according to the step (6.1) until the cache decision correction indicating quantity corresponding to each cooperative cache cluster is obtained.
(7) And (5) calculating the corresponding cache decision correction indication quantity of each non-cluster fog wireless access node according to the cache decision correction indication quantity obtained in the step (5). The method specifically comprises the following steps:
(7.1) for non-cluster fog wireless node setThe ith element F-AP of (1)iThe following steps are carried out:
if KiIf > 0, then assembleAccording to the request probability pifSorting in descending order, selecting top KiAccording to the content, the corresponding cache decision is corrected by the indication quantity delta xifSetting as 1; otherwise, the operation is not executed; wherein, KiDenotes F-APiThe available storage space of (a) is,representing the entire content set, Δ xm′fThe cache position of the content F is shown in the F-APm',Indicates all the satisfaction (AP)m,APi)∈εrOr (AP)i,APm)∈εrFog wireless access node APmA set of constructs;
(7.2) for non-clustered fog Wireless node setsAnd (7.1) repeatedly executing other elements to obtain the corresponding cache decision correction indication quantity of each non-cluster fog wireless access node.
(8) And (5) calculating a final cache decision according to the cache decision correction indicating quantity obtained in the steps (5) to (7). The method specifically comprises the following steps:
(8.1) selecting a set of access stratum fog wireless access pointsM-th node in (F-AP)mThe following steps are executed:
finding cache location is at F-APmIn the F-AP, the contents are stored in the F-APmThe final caching decision of (1) is set to 1, that is: x is the number ofmf=1,f∈{fΔxmf1} and the rest is in the F-APmIs set to 0, i.e.:wherein the content of the first and second substances,representing the entire content set, xmfRepresentative content F at F-APmFinal caching decision;
(8.2) Wireless Access Point set for Access stratum fogAnd (8.1) repeating the steps so as to obtain the final caching decision of each fog wireless access node.
While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.
Claims (9)
1. A fog wireless access network collaboration content deployment method based on graph theory is characterized by comprising the following steps:
(1) according to the cooperative cache cluster set of the access layer, constructing the popular content set of each cooperative cache cluster nAnd a popular content set for each non-clustered fog wireless access node iN is 1, …, N, I is 1, …, I, N, I respectively represent the number of the cooperative cache cluster and the non-cluster fog wireless access nodes;
(2) constructing a connection edge set epsilon of the fog wireless nodes of the access layer according to the distance and the load difference between the fog wireless nodes and the cooperative cache cluster to which the fog wireless nodes belongr;
(4) According to access layer adjacency list setObtaining epsilonrRedundant content set corresponding to each edge in the content
(5) From redundant content setsCalculating epsilonrThe cache decision correction indicating quantity of the redundant content corresponding to each edge;
(6) calculating a cache decision correction indicating quantity corresponding to each cooperative cache cluster n according to the updated popular content set of the cooperative cache clusters in the step (5);
(7) calculating a cache decision correction indicating quantity corresponding to each non-cluster fog wireless access node according to the cache decision correction indicating quantity obtained in the step (5);
(8) and (5) calculating a final cache decision according to the cache decision correction indicating quantity obtained in the steps (5) to (7).
2. The graph theory-based deployment method for the fog radio access network collaborative content, according to claim 1, is characterized in that: the step (1) specifically comprises the following steps:
(1.1) aggregating access stratum fog wireless access pointsThe nodes in the cluster are divided into N cooperative cache clusters, and non-clustered fog wireless nodes form a non-cluster fog wireless node set
(1.2) selecting the nth cooperative cache cluster, and calculating the content libraryPer content to a cooperative cache cluster nnfAnd according to the intra-cluster request probability pnfSorting in descending order by SnKmThe individual content serves as a popular content collection of a cooperative cache cluster nWherein the probability of requests p in a clusternfThe calculation formula of (A) is as follows:
in the formula (I), the compound is shown in the specification,representing a set of fog wireless access nodes, p, comprised in a cooperative cache cluster nmfF-AP (radio access node) for representing fogmThe probability of a request for content f over the coverage area,λmF-AP (radio access node) for representing fogmRequest arrival rate of SnRepresenting the number of misty wireless access nodes, K, in a cooperative cache cluster nmF-AP (radio access node) for representing fogmThe number of contents that can be cached;
(1.3) repeatedly executing other cooperative cache clusters according to the step (1.2) until a popular content set of each cooperative cache cluster is obtained;
(1.4) selecting the ith non-cluster fog wireless access nodeComputing content libraryFor each non-cluster-fog wireless access node F-APiRequest probability p ofifAnd according to the request probability pifSorting in descending order, the first KiA set of most popular contentWherein, KiF-AP (radio access node) for representing fogiThe number of contents that can be cached;
and (1.5) repeatedly executing other non-cluster-fog wireless access nodes according to the step (1.4) until the popular content set of each non-cluster-fog wireless access node is obtained.
3. The graph theory-based deployment method for the fog radio access network collaborative content, according to claim 1, is characterized in that: the step (2) specifically comprises the following steps:
(2.1) initializing the connected edge set εrIs an empty set;
(2.2) selecting a set of Access stratum fog wireless Access pointsMiddle mth node F-APmPerforming the following operations:
obtaining the m' th node F-APm'M', M ═ M + 1., M denotes the number of the fog wireless access points, and it is determined whether the following conditions are satisfied:
a、Dmm'≤γd,Lmm'≥γl(ii) a Wherein D ismm′=||dm-dm′||2,dmAnd dm′Respectively represent fog wireless access nodes F-APmAnd F-APm'Coordinates in Euclidean space, Lmm′=||λm-λm′||2,λmAnd λm′Respectively represent fog wireless access nodes F-APmAnd F-APm'Request arrival rate, gamma, over coverage areadThreshold, gamma, representing the distance between the fog radio access nodeslA threshold representing a load difference, | · | | non-conducting phosphor2Represents the L2 norm operator;
b. node F-APmAnd node F-APm'Not in the same cooperative cache cluster;
if conditions a and b are satisfied simultaneously, the edges (F-AP) will be connectedm,F-APm') Adding to the set εrPerforming the following steps;
4. The graph theory-based deployment method for the fog radio access network collaborative content, according to claim 1, is characterized in that: the step (3) specifically comprises the following steps:
(3.1) set of Wireless Access points to Access stratum fogM-th node in (F-AP)mBuilding its neighbor list set
(3.2) eliminating the adjacent table sets with the element number of 1 from the adjacent table sets of all F-AP nodes, and sequencing the rest adjacent table sets in a descending order according to the element number in the sets to obtain setsWherein H isThe number of the elements in the Chinese character 'Zhongqin'.
5. The graph theory-based deployment method for the fog radio access network collaborative content, according to claim 1, is characterized in that: the step (4) specifically comprises the following steps:
A. obtainingJ element of F-APk,jWith the first element F-APk,1The repeated popular content set corresponding to the connection edge e is obtained according to the following criteria
In the formula (I), the compound is shown in the specification,representing a set of fog wireless access nodes included in the cooperative cache cluster n,representing a non-clustered fog set of wireless nodes Denotes F-APk,jJ2, …, Jk,JkTo representThe number of middle elements;
B. for adjacency list setIs repeatedly executed (4.1), thereby obtaining a repeated popular content set corresponding to each connecting edge
for theJ element of F-APk,jInitialization of Kk,j=KmK, where J is 1, …, Jk,JkTo representThe number of medium elements, m represents a fog wireless access node F-APk,jIn the collectionThe sequence number in (1), M belongs to { 1.,. M }, M denotes the number of the fog wireless access nodes, K denotes the number of the fog wireless access nodes, andk,jand KmAll represent fog wireless access node F-APk,jK represents the maximum available storage space size of the fog wireless access node;
A. cumulative calculationJ element of F-APk,jAnd firstAn element F-APk,1The intersection of the sets of repeated popular content corresponding to the connecting edges of
B. If it isThen for the collectionJ element of F-APk,jWith the first element F-APk,1E, from the setIn random selection of Kk,1The content forms a redundant content set corresponding to the edge eAnd based on redundant content setsUpdating Kk,jUpdate the corresponding KmAnd other fog wireless access nodes with the sequence number m are F-APk',j'(k'>k,j'∈{1,...,Jk'}) available memory space Kk',j'Is updated to KmAnd updating the connection F-APk,jE' ≠ e corresponding repeated popular content setWherein J is 2, …, Jk;
C. If it isThen for the collectionJ element of F-APk,jWith the first element F-APk,1E, from the setIn the random selectionContent, together with collectionsAll contents in (1) constitute a redundant content set corresponding to the edge eAnd based on redundant content setsUpdating Kk,jUpdate the corresponding KmAnd other fog wireless access nodes with the sequence number m are F-APk',j'(k'>k,j'∈{1,...,Jk'}) available memory space Kk',j'Is updated to KmAnd updating the connection F-APk,jE' ≠ e corresponding repeated popular content setWherein J is 2, …, Jk;
6. The graph theory-based deployment method for the fog radio access network collaborative content, according to claim 1, is characterized in that: the step (5) specifically comprises the following steps:
for theJ element of F-APk,jReset Kk,j=KmK, where J is 1, …, Jk,JkTo representThe number of medium elements, m represents a fog wireless access node F-APk,jIn the collectionThe sequence number in (1), M belongs to { 1.,. M }, M denotes the number of the fog wireless access nodes, K denotes the number of the fog wireless access nodes, andk,jand KmAll represent fog wireless access node F-APk,jK represents the maximum available storage space size of the fog wireless access node;
to the collectionMiddle j element F-APk,jWith the first element F-APk,1Redundant content set corresponding to the connecting edge e ofThe following four-step operation is performed, J is 2, …, and Jk,JkTo representThe number of the medium elements is as follows:
is in the collectionWherein the cache location is found in the F-APk,1The content of (1), the content of the part is not allowed to be cached in the F-APk,jTo avoid cache redundancy, the F-AP is switched onk,jCorresponding cache decision correction indicator Δ xk,j,fSet to-1, i.e.: Δ xk,j,f=-1,And to aggregate such content from collectionsWherein the cache decision correction indicator Δ xk,j,f1 indicates that the buffer location of the content F is in the F-APk,j;
② in the collectionDoes not allow for finding a cache location in the F-APk,1The part of the content has to be cached in the F-APk,jThen F-AP is setk,jCorresponding cache decision correction indicator Δ xk,j,fSet to 1, namely: Δ xk,j.f=1,And is arranged atWhen it is time to assemble these contents from the collectionRemoving and updating Kk,jUpdate the corresponding KmAnd other fog wireless access nodes with the sequence number m are F-APk',j'(k'>k,j'∈{1,...,Jk'}) available memory space Kk',j'Is updated to KmFrom the collection of these contentsRemoving; wherein, the cache decision correction indication quantity Deltaxk,1,fCache location of presentation content F at-1 is not allowed at F-APk,1;
Respectively calculating the setsIn (3) caching in the F-APk,1Available fronthaul unload capacityAnd will aggregateIn (3) caching in the F-APk,jAvailable fronthaul unload capacityWherein:
in the formula (II)Represents all satiations (F-AP)m,F-APk,1)∈εrOr (F-AP)k,1,F-APm)∈εrFog wireless access node F-APmSet of constructs, setRepresents all satiations (F-AP)m,F-APk,j)∈εrOr (F-AP)k,j,F-APm)∈εrFog wireless access node F-APmSet of formations, λm'F-AP (radio access node) for representing fogm'Request arrival rate of (p)m'fF-AP (radio access node) for representing fogm'Probability of request for content f over the coverage area, L representing the size of each content;
fourthly ifThen set upThe remaining content is cached in the F-APk,1Higher forward unload capacity can be obtained, F-APk,1Setting the corresponding cache decision correction indication quantity to be 1, F-APk,jThe corresponding cache decision correction indication quantity is set to-1, namely: Δ xk,1.f=1,Δxk,j.f=-1,And is arranged atWhen it is time to assemble these contents from the collectionRemoving and updating Kk,1Update the corresponding KmAnd other fog wireless access nodes with the sequence number m are F-APk',j'(k'>k,j'∈{1,...,Jk'}) available memory space Kk',j'Is updated to Km(ii) a If it isThen set upThe remaining content is cached in the F-APk,jHigher forward unload capacity can be obtained, F-APk,1Setting the corresponding cache decision correction indication quantity to-1, F-APk,jThe corresponding cache decision correction indication amount is set to 1, that is: Δ xk,j.1=-1,Δxk,j.f=1,And is arranged atWhen it is time to assemble these contents from the collectionRemoving and updating Kk,jUpdate the corresponding KmAnd other fog wireless access nodes with the sequence number m are F-APk',j'(k'>k,j'∈{1,...,Jk'}) available memory space Kk',j'Is updated to Km;
7. The graph theory-based deployment method for the fog radio access network collaborative content, according to claim 1, is characterized in that: the step (6) specifically comprises the following steps:
(6-1) for the nth cooperative cache cluster, performing the following steps:
A. F-AP for the ith fog wireless access node in the nth cooperation cache clustern,lIf, ifThen will beAll the cache positions are selected in the F-APn,lCorresponding cache decision correction indicator Δ xn,l,fSet to 1, namely: Δ xn,l,f=1,If it isThen fromIn the random selection of Kn,lAnd then F-APn,lCorresponding cache decision correction indicator Δ xn,l,fSetting as 1; updating Kn,lAnd selecting the selected content from the collectionRemoving; wherein, Δ xn,l,f0 indicates that it is impossible to determine whether or not the cache position of the content F is in the foggy wireless access node F-APn,l,Kn,lDenotes F-APn,lL is 1, …, Ln represents the number of nodes in the cooperative cache cluster n;
B. for F-APn,lIf K isn,l> 0, then from the setIn random selection of Kn,lAnd correcting the corresponding cache decision by the indicated quantity delta xn,l,fSet to 1, update Kn,lAnd will select the innerCollection of contentsRemoving; otherwise, not processing; wherein, l is 1, …, Ln;
and (6.2) repeatedly executing other cooperative cache clusters according to the step (6.1) until the cache decision correction indicating quantity corresponding to each cooperative cache cluster is obtained.
8. The graph theory-based deployment method for the cooperative content in the fog radio access network, according to claim 1, wherein the step (7) specifically comprises:
(7.1) for non-cluster fog wireless node setThe ith element F-AP of (1)iThe following steps are carried out:
if KiIf > 0, then assembleAccording to the request probability pifSorting in descending order, selecting top KiAccording to the content, the corresponding cache decision is corrected by the indication quantity delta xifSetting as 1; otherwise, the operation is not executed; wherein, KiDenotes F-APiThe available storage space of (a) is,representing the entire content set, Δ xm′fThe cache position of the content F is shown in the F-APm',Indicates all the satisfaction (AP)m,APi)∈εrOr (AP)i,APm)∈εrFog wireless access node APmA set of constructs;
9. The graph theory-based deployment method for the cooperative content in the fog radio access network, according to claim 1, wherein the step (8) specifically comprises:
(8.1) selecting a set of access stratum fog wireless access pointsM-th node in (F-AP)mThe following steps are executed:
finding cache location is at F-APmIn the F-AP, the contents are stored in the F-APmThe final caching decision of (1) is set to 1, that is: x is the number ofmf=1,f∈{f|Δxmf1} and the rest is in the F-APmIs set to 0, i.e.: x is the number ofmf=0,Wherein the content of the first and second substances,representing the entire content set, xmfRepresentative content F at F-APmFinal caching decision;
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