Disclosure of Invention
In view of this, the present invention aims to provide a B5G-oriented wireless energy-carrying D2D network efficient resource allocation method, which considers user minimum rate constraints, minimum collected energy constraints, power splitting and channel allocation factor constraints and establishes a robust energy-efficient resource allocation model for jointly optimizing transmission power, sub-channels and power splitting factors. Based on a Dinkelbach method and a Worst-case method, an original NP-hard problem is converted into a deterministic convex optimization problem, and an analytic solution is obtained by utilizing a matching theory and a Lagrangian dual theory.
In order to achieve the purpose, the invention provides the following technical scheme:
a B5G-oriented wireless energy-carrying D2D network efficient resource allocation method comprises the following steps:
s1: initializing system parameters and setting total iteration times LmaxPerforming iterative initialization;
s2: obtaining a resource block distribution factor;
s3: calculating a power splitting factor;
s4: calculating the power of the cellular user and the D2D user;
s5: calculating the total energy efficiency eta (l +1) of the network;
s6: updating a Lagrange multiplier corresponding to the constraint condition;
s7: calculating the data rate of each D2D user, and judging whether the value is less than or equal to the minimum rate threshold value of the corresponding D2D user; if yes, go to S8; otherwise, go to S12;
s8: calculating the data rate of each cellular user, and judging whether the value is less than or equal to the minimum data rate threshold value of the corresponding cellular user; if yes, go to S9; otherwise, go to S12;
s9: judging whether the energy received by each pair of D2D users is more than or equal to the minimum energy threshold of the D2D user link; if yes, go to S10; otherwise, go to S12;
s10: judging whether the transmitting power of each pair of D2D user transmitters is less than or equal to the maximum transmitting power of the D2D user; if yes, go to S11; otherwise, go to S12;
s11: judging whether the transmitting power of each cellular user is less than or equal to the maximum transmitting power of the cellular user; if yes, go to S12; otherwise, entering the next iteration and returning to S2;
s12: judging whether the current iteration times are larger than the maximum iteration times or not; if yes, ending, and outputting optimal transmitting power and resource block allocation factors of the D2D user and the cellular user; otherwise, the next iteration is entered, returning to S2.
Further, in step S1, the system parameters include the number of users M, D2D, the number of users N, and the background noise σ at the base station
2Mth cellular user to base station channel gain g
m,0N-th pair of D2D user transmitter to base station channel gain h
n,0N-th pair of D2D user transmitter-to-receiver channel gains h
n,nChannel gain g for m to n pairs of D2D user receivers
m,nBackground noise at the nth pair D2D user receiverAcoustic power
Noise power introduced by the n-th pair D2D user receiver information decoding process
Energy collection efficiency factor
Circuit consumption P of all cellular users and any pair of D2D links in the system
cirAnd p
cirMinimum rate threshold for nth pair of D2D users
Minimum rate threshold for mth cellular user
Maximum transmit power of nth pair D2D user transmitter
Maximum transmit power of mth cellular user
Minimum energy threshold for activating nth pair D2D user receiver energy harvesting circuits
Upper bound on channel uncertainty epsilon for the nth pair of D2D user transmitters to receivers
nUpper bound on channel uncertainty v for cellular users m through nth pair D2D user receivers
nAnd the nth pair D2D user transmitter to base station channel uncertainty upper bound ξ
0。
Further, the obtaining of the resource block allocation factor in step S2 specifically includes the following steps:
s21: all D2D users send access requests to the first cellular user sub-channel in the preference list;
s22: all cellular users receive the D2D user pairs according to the preference list, and reject other requests;
s23: the received D2D was removed from the unmatched list, and the rejected D2D user pair removed the cellular user from the favorites list;
s24: searching for the exchange matching pair, if the exchange matching pair exists in the system, executing the exchange matching until the exchange matching pair does not exist in the system, and obtaining the resource block distribution factor xn,m。
Further, in step S3, the power splitting factor is:
wherein, l represents the number of iterations,
[x]+=max(0,x),cnrepresenting the auxiliary variable SCA, eta is the non-negative auxiliary variable, mu, in the Dinkelbach methodn,ωn,νnAnd τnIs to constrain the corresponding lagrange multiplier.
Further, the cellular user has a power of step S4
Wherein the content of the first and second substances,
the power of the D2D user is:
wherein the content of the first and second substances,
λnand phimIs a correspondingly constrained lagrange multiplier.
Further, in step S5, the total energy efficiency of the network is:
wherein the content of the first and second substances,
further, in the step S6, the D2D user data rate auxiliary variable c
nAnd d
nCellular user data rate auxiliary variable a
mAnd b
mSplitting factor constraint multiplier v in power splitter problem
nD2D user data rate constraint multiplier tau
nEnergy harvesting constraint multiplier mu
nAuxiliary variable q
nConstraint multiplier omega
n. D2D power constraint multiplier beta in power sub-problem
nHoneycomb structureUser power constraint multiplier alpha
mAuxiliary variable z
mConstraint multiplier phi
mCellular user rate constraint multiplier χ
mEnergy harvesting constraint multiplier theta
nAuxiliary variable q
nConstraint multiplier
And D2D user rate constraint multiplier lambda
nThe update expression is as follows:
where l denotes the number of iterations, d1-d11Is the update step size for the corresponding lagrange multiplier.
The invention has the beneficial effects that: compared with the algorithm of random matching under perfect channel state information, the scheme of the invention has better energy efficiency and robustness, and improves the robustness and throughput of the D2D network.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the means of the instrumentalities and combinations particularly pointed out hereinafter.
Detailed Description
The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention. It should be noted that the drawings provided in the following embodiments are only for illustrating the basic idea of the present invention in a schematic way, and the features in the following embodiments and examples may be combined with each other without conflict.
Wherein the showings are for the purpose of illustrating the invention only and not for the purpose of limiting the same, and in which there is shown by way of illustration only and not in the drawings in which there is no intention to limit the invention thereto; to better illustrate the embodiments of the present invention, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of an actual product; it will be understood by those skilled in the art that certain well-known structures in the drawings and descriptions thereof may be omitted.
The same or similar reference numerals in the drawings of the embodiments of the present invention correspond to the same or similar components; in the description of the present invention, it should be understood that if there is an orientation or positional relationship indicated by terms such as "upper", "lower", "left", "right", "front", "rear", etc., based on the orientation or positional relationship shown in the drawings, it is only for convenience of description and simplification of description, but it is not an indication or suggestion that the referred device or element must have a specific orientation, be constructed in a specific orientation, and be operated, and therefore, the terms describing the positional relationship in the drawings are only used for illustrative purposes, and are not to be construed as limiting the present invention, and the specific meaning of the terms may be understood by those skilled in the art according to specific situations.
As shown in fig. 1, the present invention considers a D2D network uplink transmission scenario based on simultaneous data transmission, and m cellular users implement uplink transmission by using an ofdma method. The N D2D user pairs have the function of digital simultaneous transmission and multiplex the channel resources of cellular users by adopting a underlying spectrum sharing mode. Only one pair of D2D users may be allowed access at a time on each subchannel. Define cellular users and D2D user sets as
And
each subchannel is assumed to be subject to block fading. Our goal is to maximize the overall energy efficiency of the system under Qos constraints of cellular users, Qos constraints of D2D users, splitting factor constraints, maximum transmit power of cellular users and D2D users, and energy harvesting constraints, so this optimization problem can be represented by jointly optimizing cellular users, D2D user power, channel allocation factor, and power splitting factor under perfect channel state information:
wherein
Which represents the total rate of the system,
represents the mth beeRate of the cell user, P
mRepresenting the transmission power, σ, of the mth cellular user
2Representing the background noise power, x, at the base station
n,mIndicating that the nth D2D user occupies the channel of the mth cellular user, g
m,0Representing the channel gain, p, from the m-th cellular user to the base station
nRepresents the transmit power, h, of the nth D2D user
n,0Indicating the channel gain of the nth pair of D2D user transmitters to the base station,
representing the rate, p, of the nth pair of D2D user links
nRepresenting the power splitting factor, h, of the nth pair of D2D user receivers
n,nRepresenting the channel gain of the nth pair D2D user transmitter to receiver,
representing the noise power introduced by the n-th pair D2D user receiver information decoding process,
representing the background noise power, g, at the nth pair of D2D user receivers
m,nRepresenting the channel gains of cellular users m through nth pair D2D users,
representing the energy collected by the nth D2D user,
the efficiency of the collection of energy is expressed,
representing the total energy consumption of the system. P
cirAnd p
cirRepresenting the circuit consumption of all cellular users and any pair of D2D links within the system,
representing the minimum rate threshold for the nth pair of D2D users,
representing the minimum rate threshold for the mth cellular user,
represents the maximum transmit power of the nth pair of D2D user transmitters,
representing the maximum transmit power of the mth cellular user,
a minimum energy threshold that indicates activation of the nth pair D2D of user receiver energy harvesting circuits. C
1Is a power splitting factor constraint; c
2Is the minimum rate constraint for each pair of D2D user receivers; c
3Is a minimum rate constraint for each cellular user; c
4Is the maximum transmit power constraint for each pair of D2D users; c
5Is a maximum transmit power constraint for each cellular user; c
6Is the minimum energy harvesting constraint for each pair of D2D user receivers, the harvested energy being greater than the minimum activation energy of the energy harvesting circuit; c
7Is a subchannel assignment constraint.
To overcome the effects of uncertainty, the uncertainty of the channel is taken into account in P1. According to the robust optimization theory, an ellipsoid bounded channel error is considered, and channel gain is modeled as follows:
wherein the content of the first and second substances,
and
is the channel estimate, Δ h
n,n,Δg
m,nAnd Δ h
n,0Is the corresponding estimation error, R
h,R
gAnd
an uncertainty set is represented. According to a continuous convex approximation, the rate is approximated as
Wherein the content of the first and second substances,
according to the worst criterion and the continuous convex approximation method, the original optimization problem P1 can be converted into the following form:
wherein the content of the first and second substances,
z
mand q is
nIs the auxiliary variable which is the variable of the auxiliary variable,
ξ
0,υ
nand
representing the upper bound of channel uncertainty.
Since P2 is a non-linear fractional programming problem. Therefore, it can be solved by the Buckbach method. Define the dickelbach function as:
wherein eta.gtoreq.0 represents energy efficiency. Thus, P2 can be restated as:
due to the binary variable xn,mP3 is still a non-convex optimization problem due to the coupling relationship with other variables to solve the problem, x is determined by using a matching algorithmn,mAnd then solving the remaining convex optimization problem.
The steps of the matching algorithm are as follows:
1. all D2D users sent access requests to the first cellular user sub-channel in the favorites list;
2. all cellular users receive the D2D user pairs according to the preference list, and reject other requests;
3. the received D2D was removed from the unmatched D2D user list, and the rejected D2D user removed the corresponding cellular user from the preference list;
4. repeat 1-3 until all D2D users in the system match a channel;
5. and searching a matching block pair in the system, and executing exchange matching.
The preferences of cellular users and D2D users are defined as utility functions, expressed as utility functions, respectively
Where k represents the cost of accessing the cellular user subchannel. The definition of a matching occlusion pair is: when two pairs of D2D users exchange their matched cellular user channels, the increased utility of both parties is a matched blocked pair.
Because of ρ
nAnd C
1,
And C
12In connection with this, based on the alternative optimization idea, the problem P3 is decomposed to contain only rho
nSub-questions of other variables. Definition of
P3 can be re-described as
By using the lagrangian function, there are:
wherein, vn≥0,τn≥0,μn≥0,ωnAnd more than or equal to 0 is a Lagrangian multiplier corresponding to the constraint condition of the optimization problem P4.
By using the KKT condition, the optimal split factor is solved as:
wherein, [ x ]]+=max(0,x),
The lagrange multiplier can be updated using a gradient descent method
Wherein l represents the number of iterations, d1-d4Is the iteration step size. By selecting a proper step length, the convergence of the Lagrangian algorithm can be ensured.
Definition of same theory
At a determined
Under the conditions, P3 can translate into the following power distribution subproblem
Wherein the content of the first and second substances,
by KKT condition, the analytic solution of the optimal power can be obtained as
Wherein the content of the first and second substances,
the lagrange multiplier update law is:
wherein l represents the number of iterations, d5-d11Representing the step size. By selecting a proper step length, the convergence of the Lagrangian algorithm can be ensured. The system energy efficiency resource allocation algorithm is shown in fig. 2.
The application effect of the present invention will be described in detail with reference to the simulation.
Simulation conditions are as follows: the simulation parameters are set to M-2, N-2,
σ
2=10
-5W,
W,l
max=10
4,T=10
4,
P
cir=0.04W,p
cir=0.02W,
ε
n∈[0,1],υ
n∈[0,1],ξ
0∈[0,1]the channel fading model includes rayleigh fading, shadow fading, and path loss.
And (3) simulation results: in the present embodiment, fig. 3 shows a convergence diagram of the system energy efficiency and the power splitting factor in the present embodiment. Fig. 4 shows a graph of the actual rate versus uncertainty of D2D users under different resource allocation methods and different algorithms. FIG. 5 is a graph showing a relationship between total energy efficiency and collected energy threshold of the system under different resource allocation methods and different algorithms. Fig. 3 shows that the algorithm of the present invention can achieve convergence quickly, which means that the algorithm of the present invention can ensure the communication quality of cellular users well and has real-time performance. FIG. 4 shows the dependence on the channel uncertainty Δ hn,nThe actual rate of D2D users may decrease. On the other hand, when the channel uncertainty reaches a certain value, the data rate of the non-robust algorithm is lower than the minimum data rate, but the algorithm of the invention can be well controlled above the minimum data rate. Fig. 5 shows that as the minimum collected energy threshold increases, the overall energy efficiency of the system decreases, and the energy efficiency of the algorithm of the present invention is always better than that of the non-robust algorithm and other algorithms. The experimental results of fig. 3, fig. 4 and fig. 5 show that the algorithm of the present invention guarantees the real-time performance, and simultaneously guarantees the service quality of the cellular users, and has good robustness and energy efficiency.
Finally, the above embodiments are only intended to illustrate the technical solutions of the present invention and not to limit the present invention, and although the present invention has been described in detail with reference to the preferred embodiments, it will be understood by those skilled in the art that modifications or equivalent substitutions may be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions, and all of them should be covered by the claims of the present invention.