CN112367644B - D2D-based system throughput optimization method in wireless cache network - Google Patents

D2D-based system throughput optimization method in wireless cache network Download PDF

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CN112367644B
CN112367644B CN202011176152.9A CN202011176152A CN112367644B CN 112367644 B CN112367644 B CN 112367644B CN 202011176152 A CN202011176152 A CN 202011176152A CN 112367644 B CN112367644 B CN 112367644B
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CN112367644A (en
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黄刚
谢洪岩
毕茂华
陈乃阔
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Chaoyue Technology Co Ltd
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W4/00—Services specially adapted for wireless communication networks; Facilities therefor
    • H04W4/70—Services for machine-to-machine communication [M2M] or machine type communication [MTC]
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W16/00—Network planning, e.g. coverage or traffic planning tools; Network deployment, e.g. resource partitioning or cells structures
    • H04W16/02—Resource partitioning among network components, e.g. reuse partitioning
    • H04W16/10—Dynamic resource partitioning
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W16/00—Network planning, e.g. coverage or traffic planning tools; Network deployment, e.g. resource partitioning or cells structures
    • H04W16/18—Network planning tools
    • 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
    • H04W28/08—Load balancing or load distribution
    • 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
    • H04W28/10—Flow control between communication endpoints
    • H04W28/14—Flow control between communication endpoints using intermediate storage
    • 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

Abstract

A D2D-based wireless cache network system throughput optimization method comprises the following steps: establishing a system throughput optimization model of the wireless cache network under a constraint condition; decomposing a wireless cache network system throughput optimization model into an access selection and distribution model and a power control model; providing access service and channel allocation for the D2D request user according to the access selection and allocation model; judging and maintaining feasibility of power control of channels distributed by D2D users; and responding to the feasibility of power control, converting the power control model into a DC plan, solving a solution of the DC plan, and carrying out throughput optimization based on the solution of the DC plan. The method provided by the invention effectively improves the system throughput of the D2D wireless cache network, provides the lowest transmission power selection for the D2D user, greatly improves the frequency spectrum multiplexing rate of the cellular user, and provides a better solution for the application of the D2D-based wireless cache network system.

Description

D2D-based system throughput optimization method in wireless cache network
Technical Field
The invention belongs to the field of content sharing and resource allocation in a wireless cache network; in particular to a method for optimizing system throughput in a wireless cache network based on D2D.
Background
The D2D-based wireless cache network is a very promising technology, and the backhaul link load of a base station and the time delay for a user to acquire service can be effectively reduced by deploying the content in the network in the cache close to a D2D user; by multiplexing the frequency spectrum resources of the cellular users, the D2D communication can effectively improve the frequency spectrum utilization rate and the throughput of the system. However, if the mutual interference between the cellular users and the D2D users caused by the spectrum reuse cannot be effectively handled, the advantages of the D2D-based wireless cache network cannot be fully exploited. Although a lot of important technical achievements have been developed in a resource allocation algorithm in the current wireless cache network, most researches only consider that a single D2D user multiplexes a single cellular user spectrum resource, and do not consider the influence of multiple D2D user accesses on resource allocation. Therefore, the research on the resource allocation method combining D2D user access and channel allocation can effectively improve the spectrum efficiency of a cellular system and improve the system throughput.
Disclosure of Invention
Aiming at the current situation, the invention designs a D2D-based wireless cache network system throughput optimization method, which comprises the following steps:
establishing a system throughput optimization model of the wireless cache network under a constraint condition;
decomposing a wireless cache network system throughput optimization model into an access selection and distribution model and a power control model;
providing access service and channel allocation for the D2D request user according to the access selection and allocation model;
judging and maintaining feasibility of power control of channels distributed by D2D users;
and responding to the feasibility of power control, converting a power control model into a DC plan, solving a solution of the DC plan, and carrying out throughput optimization based on the solution of the DC plan.
In some embodiments, the system throughput optimization model of the wireless cache network under the constraint condition is:
Figure BDA0002748719980000021
wherein, P i c And
Figure BDA0002748719980000022
respectively representing the transmission power of cellular users iRate and D2D request service user transmit power of user j;
ζ j the local storage of the D2D requesting user j is represented whether the network content requested by the user j is cached or not;
ρ m,j indicating whether the D2D requesting user j can be served by the D2D service user m;
v i,j indicating whether the D2D request user j multiplexes the spectrum resource of the cellular user i;
Figure BDA0002748719980000023
and represents a cellular user set;
Figure BDA0002748719980000024
respectively representing a cellular user set and a D2D request user set; />
N c And N r Respectively the number of cellular users and the number of D2D request users in a cellular cell;
Figure BDA00027487199800000211
a candidate service user set representing a D2D request user j;
Figure BDA0002748719980000026
and &>
Figure BDA0002748719980000027
Respectively representing the transmission rates of a cellular user and a D2D request user;
the constraint conditions are as follows:
Figure BDA0002748719980000028
wherein the constraint (a) represents a transmit power constraint for cellular users and D2D links,
Figure BDA0002748719980000029
and &>
Figure BDA00027487199800000210
Maximum transmit power for cellular users and D2D service users, respectively;
constraint (b) represents a transmission rate constraint for cellular users and D2D links, R c And R d Minimum rate constraints for cellular users and D2D links, respectively;
constraint (c) indicates that a single D2D requesting user can only be served by a single D2D transmitting user;
constraint (D) indicates that a single D2D link can only multiplex the spectrum resources of a single cellular user.
In some embodiments, in a wireless cache network system throughput optimization model
Figure BDA0002748719980000031
And &>
Figure BDA0002748719980000032
Respectively expressed as:
Figure BDA0002748719980000033
Figure BDA0002748719980000034
wherein
Figure BDA0002748719980000035
And &>
Figure BDA0002748719980000036
Representing the noise power of the cellular link and the D2D link, respectively;
G i,B respectively representing the channel gains of cellular users i to the base station;
G i,j shown as the interfering link gain, G, of cellular user i to D2D requesting user j j Channel gain, G, for user j, denoted D2D request j,i The interference link gain of the serving user, denoted as D2D requesting user j, to cellular user i; g k,j The interference link gain of the serving user of the D2D requesting user k to the D2D requesting user j.
In some embodiments, the access selection and channel allocation model is represented as:
Figure BDA0002748719980000037
/>
Figure BDA0002748719980000038
in some embodiments, the power control model is:
Figure BDA0002748719980000041
Figure BDA0002748719980000042
wherein, DS i A set of D2D requests representing the reuse of the ith cellular user spectrum resource.
In some embodiments, providing access services and channel allocation for D2D requesting users according to the access selection and allocation model comprises:
converting the three-dimensional matching of the access selection and the channel allocation model into two-dimensional bilateral graph matching;
and calculating to obtain the service user of the D2D request user according to the bilateral graph matching algorithm.
In some embodiments, providing access services and channel allocation for the D2D requesting user according to the access selection and allocation model further comprises:
and calculating to obtain the cellular user spectrum resource with the minimum sum of the channel allocation co-channel interference of the D2D request user by adopting a heuristic iterative algorithm.
In some embodiments, determining and maintaining feasibility of power control for channels allocated by D2D users includes:
judging the feasibility of power control through a Perron-Frobenius theory;
if not, executing link removing algorithm to remove the request user with maximum interference of co-channel in channel allocation until power control is feasible.
In some embodiments, converting the power control model to a DC plan includes:
converting the power control model into a target function in a DC programming form;
and solving the DC plan by using a continuous convex optimization method through a first-order Taylor expansion to obtain an optimal solution.
In some embodiments, a wireless caching network includes a plurality of D2D requesting users, a plurality of D2D serving users, and a plurality of cellular users; the cellular user transmits data on a given authorized channel, the D2D service user caches network content, and the D2D request user requests network content.
The D2D wireless cache network system throughput optimization method provided by the invention provides good access selection and channel matching for D2D users, improves the spectrum utilization rate, provides optimal transmitting power for the D2D users, minimizes co-channel interference, maximizes the throughput of system data transmission, and provides a solution for a high-efficiency D2D wireless cache network system.
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In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art that other embodiments can be obtained by using the drawings without creative efforts.
Figure 1 is a graph comparing the results of system throughput as a function of cell user signal-to-interference ratio constraints for two algorithms of the present invention and the prior art.
Fig. 2 is a graph comparing the number of system access D2D links with the change of the cell user signal-to-interference ratio constraint in two algorithms according to the present invention and the prior art.
FIG. 3 is a flow chart of the method of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the following embodiments of the present invention are described in further detail with reference to the accompanying drawings.
In the present invention. The wireless cache network model based on Underarying-D2D comprises N r D2D requesting user, N s D2D service subscriber and N c A cellular subscriber. A cellular user transmits data on a given authorization channel, a D2D service user caches network content according to certain caching probability distribution, and a D2D request user requests the network content; when a D2D request user requests network content, firstly checking whether local storage caches the network content, and if the local storage caches the network content, completing service; otherwise, requesting service from the adjacent D2D service user: if the data requested by the adjacent D2D service user is cached and the signal-to-interference-and-noise ratio condition is met, multiplexing the frequency spectrum resources of the cellular user and providing service by the D2D service user; otherwise, the base station allocates specific spectrum resources for the D2D request user to provide service.
As shown in fig. 3, the present invention provides a D2D-based method for optimizing throughput of a wireless cache network system, including the following steps:
s1, establishing a system throughput optimization model of a wireless cache network under a constraint condition;
s2, decomposing a throughput optimization model of the wireless cache network system into an access selection and distribution model and a power control model;
s3, providing access service and channel allocation for the D2D request user according to the access selection and allocation model;
s4, judging and maintaining feasibility of power control of channels distributed by the D2D users;
and S5, responding to feasibility of power control, converting the power control model into a DC plan, solving a solution of the DC plan, and carrying out throughput optimization based on the solution of the DC plan.
In step S1, an undermining-D2D-based wireless cache network model is established, and a system throughput optimization model of the undermining-D2D-based wireless cache network model under constraint conditions is expressed as:
Figure BDA0002748719980000061
wherein, P i c And
Figure BDA0002748719980000062
respectively representing the transmitting power of a cellular user i and the transmitting power of a service user of a D2D request user j;
ζ j indicating whether the local storage of the D2D requesting user j caches the requested network content, if the local storage of the D2D requesting user j caches the requested network content, zeta j =1, otherwise ζ j ＝0；
ρ m,j Represents whether the D2D requesting user j can be served by the D2D service user m, if the D2D requesting user j can be served by the D2D service user m, then rho m,j =1, otherwise ρ m,j ＝0；
v i,j Indicating whether the D2D request user j multiplexes the frequency spectrum resource of the cellular user i, if the D2D request user j multiplexes the frequency spectrum resource of the cellular user i, v i,j =1, vice versa v i,j ＝0；
Figure BDA0002748719980000071
And represents a set of cellular users;
Figure BDA0002748719980000072
representing a set of D2D requesting users;
N c and N r Respectively the number of cellular users and the number of D2D request users in a cellular cell;
Figure BDA00027487199800000712
a candidate service user set representing a D2D request user j;
Figure BDA0002748719980000074
and &>
Figure BDA0002748719980000075
Respectively representing the transmission rates of the cellular user and the D2D request user;
the constraint conditions are as follows:
Figure BDA0002748719980000076
wherein the constraint (a) represents a transmit power constraint for the cellular user and the D2D link,
Figure BDA0002748719980000077
and &>
Figure BDA0002748719980000078
Maximum transmit power for cellular users and D2D service users, respectively;
constraint (b) represents a transmission rate constraint for cellular users and D2D links, R c And R d Minimum rate constraints for cellular users and D2D links, respectively;
constraint (c) indicates that a single D2D requesting user can only be served by a single D2D transmitting user;
constraint (D) indicates that a single D2D link can only multiplex the spectrum resources of a single cellular user.
In some embodiments of the present invention, in a wireless cache network system throughput optimization model,
Figure BDA0002748719980000079
and &>
Figure BDA00027487199800000710
Respectively expressed as:
Figure BDA00027487199800000711
/>
Figure BDA0002748719980000081
wherein
Figure BDA0002748719980000082
And &>
Figure BDA0002748719980000083
Representing the noise power of the cellular link and the D2D link, respectively;
G i,B respectively representing the channel gains of cellular users i to the base station;
G i,j denoted as interfering link gain, G, for cellular user i to D2D requesting user j j Channel gain, G, for user j, denoted D2D request j,i The interference link gain of the serving user, denoted as D2D requesting user j, to cellular user i; g k,j The interference link gain of the serving user of the D2D requesting user k to the D2D requesting user j.
In step S2, the throughput optimization model of the wireless cache network system is decomposed into an access selection and allocation model and a power control model, after D2D access selection and channel allocation are determined, the state of each channel is determined, and the throughput optimization is sequentially obtained for each channel, so that the total throughput of the system is optimal.
In some embodiments of the present invention, the D2D access selection and channel allocation model is:
Figure BDA0002748719980000084
Figure BDA0002748719980000085
wherein P is compared to the system throughput model of the wireless cache network described above i c And
Figure BDA0002748719980000086
are all fixed transmit frequencies: and->
Figure BDA0002748719980000087
In some embodiments of the invention, the power control model is:
Figure BDA0002748719980000091
/>
Figure BDA0002748719980000092
wherein, DS i A set of D2D requests representing the reuse of the ith cellular user spectrum resource.
In step S3, providing access service and channel allocation for the D2D requesting user according to the access selection and allocation model includes: converting the three-dimensional matching of the D2D access selection and the channel allocation model into bilateral graph matching, determining the D2D user access selection by using a bilateral graph matching algorithm, and then obtaining the channel allocation state of the D2D request user by using a heuristic iterative algorithm.
In some embodiments of the present invention, a specific process of the bilateral graph matching algorithm is as follows:
first, initialize the D2D link matrix
Figure BDA0002748719980000093
Then determining a candidate service user matrix ^ of the D2D requesting user according to the cache contents of the D2D requesting user and the D2D service user>
Figure BDA0002748719980000094
That is, if D2D requests user jCache the network content it requested, then &>
Figure BDA0002748719980000095
Otherwise
If the D2D service user m caches the network content requested by the D2D request user j and the communication distance between the D2D user m and the D2D user j is smaller than the maximum communication distance R of the D2D d Then DC j,m =1, whereas, DC j,m ＝0。
Second, calculate popularity for each D2D requesting user
Figure BDA0002748719980000096
If->
Figure BDA0002748719980000097
Then the user set is requested from D2D>
Figure BDA0002748719980000098
Removing D2D requesting user j.
Third, requesting a user set from D2D
Figure BDA0002748719980000099
In select>
Figure BDA00027487199800000910
Minimum D2D requesting user j, set &'s from D2D serving user>
Figure BDA00027487199800000911
Selecting to satisfy DC for D2D requesting user j j,m 1 and I m,j The largest candidate D2D service user m; setting DL j,m ＝1。
The fourth step, respectively from
Figure BDA0002748719980000101
And &>
Figure BDA0002748719980000102
Removing the D2D request j and the D2D service user m;
in the fifth step, if
Figure BDA0002748719980000103
If the set is an empty set, ending the algorithm; otherwise, returning to the third step.
Wherein, the first and the second end of the pipe are connected with each other,
Figure BDA0002748719980000104
preference selection defined as D2D requesting user j, I m,j A larger indicates a larger gain obtained by the requesting user j and thus a larger transmission rate.
In some embodiments of the present invention, the specific process of the heuristic iterative algorithm for channel allocation is:
first, inputting cellular user transmitting power P c D2D service user transmitting power P d Channel gain matrix G and D2D link matrix DL;
second, initializing the channel allocation matrix
Figure BDA0002748719980000105
Setting WT i =0 store total channel interference in subchannel i, D2D requesting user set multiplexing spectrum resource of cellular user i is ÷ based on>
Figure BDA0002748719980000106
Initializing j =0 to indicate that a channel is currently allocated to the D2D requesting user j; />
Third, j = j +1; when the D2D request user j multiplexes the frequency spectrum resource of each cellular user i in turn, the co-channel interference of each channel i, namely
Figure BDA0002748719980000107
Fourthly, multiplexing the D2D request user j with the cellular user i * Of spectrum resources of, wherein
Figure BDA0002748719980000108
Updating a device>
Figure BDA0002748719980000109
Adding a D2D requesting user j to a set +>
Figure BDA00027487199800001010
Setting up
Figure BDA00027487199800001011
Step five, if j = N r If yes, ending the algorithm; otherwise, returning to the third step.
Wherein, a service user of each D2D request user is obtained according to DL:
1) If it is used
Figure BDA00027487199800001012
Then W i,j For co-channel interference W between D2D link and cellular user i,j Comprises the following steps:
Figure BDA00027487199800001013
2) If it is not
Figure BDA00027487199800001014
Then W i,j For co-channel interference between different D2D links, W i,j Comprises the following steps:
Figure BDA00027487199800001015
SINR c and SINR d Signal to interference plus noise ratio thresholds for the cellular user link and the D2D link respectively,
Figure BDA00027487199800001016
is a D2D link set.
In step S4, the determining and maintaining the feasibility of power control of the channels allocated by the D2D users includes:
determining feasibility of power control using Perron-Frobenius theory;
and if not, executing a link removal algorithm to remove the D2D request user with the largest co-channel interference in the current channel allocation until the power control is feasible.
In the embodiment of the invention, the constraint conditions of the power control model are converted into a matrix form:
I-ΓZ P≥Γn
wherein P is the transmission power vector of the cellular user link and the D2D link, and I is | DS i And an | + 1-dimensional unit matrix, wherein Γ is a signal-to-interference-and-noise ratio constraint matrix of the cellular user link and the D2D link, Z represents a normalized path gain matrix, and n represents a normalized noise power vector. The specific definition is as follows:
Figure BDA0002748719980000111
/>
Figure BDA0002748719980000121
if the maximum eigenvalue of Γ Z is greater than 1, then the power control has no solution; otherwise, there is one positive power vector such that the cellular user link and the D2D link satisfy the signal to interference plus noise ratio constraint. The minimum emission power Pp is derived from (I- Γ Z) Pq ≧ Γ n * ＝(1-ΓZ) -1 Γ n; i.e. arbitrary feasible transmit power
Figure BDA0002748719980000124
Satisfy +>
Figure BDA0002748719980000122
If P is * If the transmission power constraint of the cellular user and the D2D service user is met, the power control is feasible; otherwise, the power control has no solution.
DS is removed in turn if power control is not feasible i The maximum co-channel interference (Metric) generated between the uplink and the other links j The largest link is obtained until the link is feasible, so that the D2D link can be ensured to be accessed into the frequency spectrum resource of the cellular user as much as possible, and the system throughput is improved.
Wherein
Figure BDA0002748719980000123
In some embodiments of the present invention, the specific process of the link removal algorithm is:
in the first step, Γ, Z, and n are calculated based on the channel allocation status and channel gain.
Second, calculate maximum eigenvalue of Γ Z and minimum transmitting power P of power control * 。
Thirdly, if the maximum eigenvalue of Γ Z is less than 1 and P * If the transmission power constraints of cellular users and D2D users are met, the problem is feasible, and the algorithm is ended; otherwise, calculating Metric for each D2D request user j j Removal of Metric j And the largest D2D requests the user, and the first step is returned.
In step S5, in response to power control being available, converting the power control model to a DC plan and solving for the DC plan includes: and converting the power control subproblem model into a DC planning problem, and solving the DC planning by using a continuous convex optimization method through a first-order Taylor expansion.
In some embodiments of the invention, the objective function in the form of a DC plan for power control is: t is i ＝g i -h i Wherein, g i And h i The mathematical expressions of (a) are respectively:
Figure BDA0002748719980000131
/>
Figure BDA0002748719980000132
then by mixing h i And replacing the first-order Taylor expansion, converting the DC planning problem into a convex optimization problem, and solving power control by using a continuous convex optimization method.
The continuous convex optimization method is to use h i Is replaced by
Figure BDA0002748719980000133
First order Taylor expansion as initial point I i ，I i The definition of (A) is as follows:
Figure BDA0002748719980000134
wherein, P 0 Is any feasible point of the power control sub-problem,
Figure BDA0002748719980000135
are respectively h i In respect of P i c And &>
Figure BDA0002748719980000136
The specific expression of the first partial derivative of (a) is as follows:
Figure BDA0002748719980000137
Figure BDA0002748719980000138
by the approximation, the objective function of power control can be converted into T i ＝g i -I i And solving by a continuous convex optimization method.
The continuous convex optimization method comprises the following specific steps:
in the first step, the number of initialization iterations K =0, and the maximum number of iterations L. Initializing P with any feasible point in feasible domain 0 。
Second step with h i At P 0 First order Taylor expansion formula I of point expansion i Substitute for h i Update K = K +1.
Thirdly, optimizing the problem by using an interior point method to obtain the optimal solution P of the current problem K 。
Fourthly, if K is less than or equal to L, updating P 0 ＝P K Returning to the step 2; otherwise, P K I.e. the optimal solution to the problem. Will P K And optimizing the wireless cache network as the transmitting power in a system throughput optimization model of the wireless cache network under the constraint condition.
The system throughput obtained by the technical scheme of the invention through experiments is compared with a multi-user single cellular user spectrum resource multiplexing scheme (algorithm 1) and a single D2D user single cellular user spectrum resource multiplexing scheme (algorithm 2) which do not consider D2D access selection. As shown in fig. 1, the technical solution of the present invention will achieve higher system throughput.
The number of D2D links accessed by experiments performed with the method provided by the present invention is compared with a scheme (algorithm 1) for multiplexing single cellular user spectrum resources by multiple users without considering D2D access selection and a scheme (algorithm 2) for multiplexing single cellular user spectrum resources by single D2D users. As shown in fig. 2, the number of D2D links accessed by the system in the technical solution of the present invention is more, because we consider the co-channel interference and the influence of the signal to interference plus noise ratio of different links at the same time.
Compared with the prior art, the invention has the beneficial effects that: according to the technical scheme, the system throughput is maximized and decomposed into the D2D access selection submodel and the channel allocation submodel and the power control submodel, the service users, the channel allocation, the optimal transmitting power of cellular users and the optimal transmitting power of the D2D users of the D2D request users are respectively determined, and therefore the system throughput is maximized. The service quality requirements of cellular users and D2D users are ensured in the limiting conditions of the system throughput optimization problem; the frequency spectrum resource of a single cellular user can be reused by a plurality of D2D users, and the frequency spectrum efficiency of the system can be effectively improved; meanwhile, the transmitting power of the cellular user and the D2D user is limited, and the normal work of the equipment is ensured; the problem of optimizing the system throughput is a mixed integer nonlinear programming problem, and the original problem is decomposed into a D2D access selection and channel allocation sub-problem and a power control sub-problem, so that the solving complexity is reduced, and the compromise between the operation complexity and the algorithm performance is realized; the sub-problem of D2D access selection and channel allocation is still an NP-hard problem, three-dimensional matching is converted into bilateral matching, and a service user of a D2D request user is determined by using a bilateral graph matching algorithm; and then, minimizing the co-channel interference of each cellular user channel through a heuristic iterative algorithm to determine the spectrum reuse state.
Furthermore, in the technical scheme, a Perron-Frobenius theory is used for determining the feasibility of the power control subproblem. And if the problem is not feasible, executing a link removal algorithm to remove the D2D request user with the largest co-channel interference in the current channel allocation until the power control sub-problem is feasible, so that more D2D users can be accessed as much as possible.
Furthermore, the power control subproblem model is converted into a DC planning problem, and the solving complexity is reduced by solving a local optimal solution of the DC planning through a first-order Taylor expansion.

Claims (3)

1. A D2D-based wireless cache network system throughput optimization method is characterized by comprising the following steps:
establishing a system throughput optimization model of the wireless cache network under a constraint condition;
decomposing a wireless cache network system throughput optimization model into an access selection and distribution model and a power control model;
providing access service and channel allocation for the D2D request user according to the access selection and allocation model;
judging and maintaining feasibility of power control of channels distributed by D2D users;
in response to the feasibility of power control, converting a power control model into a DC plan, solving a solution of the DC plan, and carrying out throughput optimization based on the solution of the DC plan;
the system throughput optimization model of the wireless cache network under the constraint condition is as follows:
Figure FDA0004017028290000011
wherein, P i c And
Figure FDA0004017028290000012
respectively representing the transmitting power of a cellular user i and the transmitting power of a service user of a D2D request user j;
ζ j the local storage of the D2D requesting user j is represented whether the network content requested by the user j is cached or not;
ρ m,j indicating whether the D2D requesting user j can be served by the D2D service user m;
v i,j indicating whether the D2D request user j multiplexes the spectrum resource of the cellular user i;
Figure FDA0004017028290000013
and &>
Figure FDA0004017028290000014
Respectively representing a cellular user set and a D2D request user set;
N c and N r Respectively the number of cellular users and the number of D2D request users in a cellular cell;
Figure FDA0004017028290000015
representing a candidate service user set of the D2D request user j;
Figure FDA0004017028290000016
and &>
Figure FDA0004017028290000017
Respectively representing the transmission rates of the cellular user and the D2D request user;
the constraint conditions are as follows:
Figure FDA0004017028290000021
wherein the constraint (a) represents a transmit power constraint for the cellular user and the D2D link,
Figure FDA0004017028290000022
and &>
Figure FDA0004017028290000023
Maximum transmit power for cellular users and D2D service users, respectively;
constraint (b) represents a transmission rate constraint for cellular users and D2D links, R c And R d Minimum rate constraints for cellular users and D2D links, respectively;
constraint (c) indicates that a single D2D requesting user can only be served by a single D2D transmitting user;
the constraint (D) indicates that a single D2D link can only multiplex spectrum resources of a single cellular user;
in the model
Figure FDA0004017028290000024
And &>
Figure FDA0004017028290000025
Respectively expressed as:
Figure FDA0004017028290000026
/>
Figure FDA0004017028290000027
wherein
Figure FDA0004017028290000028
And &>
Figure FDA0004017028290000029
Representing the noise power of the cellular link and the D2D link, respectively;
G i,B respectively representing the channel gains of cellular users i to the base station;
G i,j denoted as interfering link gain, G, for cellular user i to D2D requesting user j j Channel gain, G, for user j, denoted D2D request j,i The interference link gain to cellular user i denoted as D2D requesting user j's service; g k,j The interference link gain of the service of the D2D request user k to the D2D request user j is expressed;
the access selection and channel allocation model is represented as:
Figure FDA0004017028290000031
Figure FDA0004017028290000032
the power control model is as follows:
Figure FDA0004017028290000033
Figure FDA0004017028290000034
wherein, DS i A set of D2D requests representing a reuse of an ith cellular user spectrum resource;
the providing access service and channel allocation for the D2D requesting user according to the access selection and allocation model includes:
converting the three-dimensional matching of the access selection and the channel allocation model into two-dimensional bilateral graph matching;
calculating according to a bilateral graph matching algorithm to obtain a service user of the D2D request user;
the determining and maintaining feasibility of power control of channels allocated to D2D users includes:
judging the feasibility of power control through a Perron-Frobenius theory;
if not, executing a link removal algorithm to remove the request user with the maximum interference of the common channel in the channel allocation until the power control is feasible;
the converting the power control model into the DC plan comprises:
converting the power control model into a target function in a DC programming form;
and solving the DC plan by using a continuous convex optimization method through a first-order Taylor expansion to obtain an optimal solution.
2. The method of optimizing throughput in a wireless cache network system according to claim 1, further comprising:
and calculating to obtain the cellular user spectrum resource with the minimum sum of the channel allocation co-channel interference of the D2D request user by adopting a heuristic iterative algorithm.
3. The method of claim 1, wherein the method comprises:
the wireless cache network comprises a plurality of D2D requesting users, a plurality of D2D serving users, and a plurality of cellular users; the cellular user transmits data on a given authorized channel, the D2D service user caches network content, and the D2D request user requests network content.
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