CN106712816A - Design method for safe beam forming based on energy harvesting cognitive network - Google Patents

Abstract

The invention discloses a design method for safe beam forming based on an energy harvesting cognitive network. The design method comprises the steps of firstly establishing a problem of target optimization for the maximum transmission rate of a secondary user system in a cognitive wireless network by taking the energy harvesting time ratio as a variable; secondly, transforming the problem of target optimization into a problem of semi-definite relaxation by using a matrix conjugate transposition principle, and transforming the problem of semi-definite relaxation into a problem of convex optimization in an equivalent manner by adopting a Charnes-Cooper; and finally, acquiring a globally optimal solution comprising a forwarding beam forming vector and a cognitive beam forming vector through one-dimensional search for the energy harvesting time ratio, and thus solving safe rates of a primary user and a secondary user, and completing design for safe beam forming of the cognitive wireless network. The design method disclosed by the invention greatly simplifies the design process. In addition, the solving scheme not only can prevent interception of an eavesdropping user for confidential information, but also can realize increase in transmission rate at the same time, and effectively improves the performance of the system.

Description

A kind of method for designing of the safe beam forming based on energy harvesting cognition network

Technical field

The invention belongs to field of communication security, more particularly to a kind of safe beam forming that cognition network is gathered in based on energy Method for designing.

Background technology

In face of the growing demand that is wirelessly transferred, frequency spectrum resource turns into a kind of rare resource, cognition wireless network There is the effective spectrum efficiency for improving wireless network.Carrying out cooperation transmission using secondary user's (SU) not only can be with less Resource consumption lift the transmission of primary user (PU) data, while SU can also be transmitted using the frequency spectrum resource of part primary user The information of oneself, so as to reach the effect of doulbe-sides' victory.But the collaboration communication meeting in some practical application scenes between PU and SU It is restricted, such as when sensor is used as cooperating relay, due to the finite capacity of battery, if charging or timely can not be provided When changing battery, cooperation transmission can then be interrupted.Therefore, if relaying can obtain energy from transmission environment, then coorporative network " life cycle " of network will greatly extend.In order to solve this problem, energy harvesting quilt is carried out using radio frequency (RF) signal It is recognized as a kind of effective solution.At present, the combination that wireless energy gathers in technology and cordless communication network has been obtained Extensive concern, just progressively turns into a new hot research problem in radio communication.In the radio communication gathered in based on energy In network, energy of the wireless energy harvesting node completely as entrained by radiofrequency signal is powered, and then the node is using harvesting Energy carry out associative operation and data transfer again.

Due to broadcast characteristic of the radio communication in transmission information, the information of user is easy to be stolen in transmitting procedure Listen.In the collaboration communication of energy harvesting, the transmitting terminal (ST) of secondary user's carries out the energy using harvesting as cooperating relay The signal of PU is forwarded, is possible to eavesdrop the signal of PU because of this user's receiving terminal (SR), so as to generate a series of information peace Full problem.In traditional cognition wireless network, for the safety of guarantee information, the beam forming of safety of physical layer has been carried out Extensive research.In recent years, the safety for carrying out energy harvesting and lifting physical layer using relaying is also greatly paid close attention to. ZHANG N have studied and how to design in half-duplex relay network and optimize safe wave beam from the angle of achievable safe rate Shaping and transimission power, (bibliography ZHANG N, LU N, SHEN X X.Cooperative spectrum access towards secure information transfer for CRNs[J].IEEE Journal on Selected Areas in Communications,2013,31(11):2453-2464.) in the cooperative cognitive network of energy harvesting, examine Considering SU may eavesdrop the information of PU this problem, for the safe rate design of collaborative network, there is scholar's research at present Under single-input single-output (SISO) pattern, the situation for single SR and multiple SR has carried out the fast up to safety of collaboration mode Rate is analyzed.The analysis of the cooperative cognitive network to being gathered in based on energy is only limited under the pattern of SISO above, and is not accounted for How the distribution of energy harvesting time and message processing time is optimized.

The content of the invention

The invention provides a kind of method for designing of the safe beam forming based on energy harvesting cognition network, its purpose exists In the Communication Security Problem of the safe beam forming for overcoming cooperative cognitive wireless network.

A kind of method for designing of the safe beam forming based on energy harvesting cognition wireless network, comprises the following steps：

Step one：Time ratio is gathered in as optimized variable with energy, optimization is turned to the transmission rate maximum of secondary custom system Target, builds the safe beamforming design optimization problem that cognition wireless network is gathered in based on energy so that primary user's system expires The transmit power of sufficient secure communication quality requirement and secondary custom system transmitting terminal meets secure communication limitation；

Step 2：The objective optimisation problems described in step one are converted into semidefinite decoding using Matrix Conjugate transposition principle Problem, it is convex optimization problem by semidefinite decoding problem equivalency transform to use Charnes-Cooper；

Step 3：Time is gathered in than obtaining globally optimal solution by linear search energy, the globally optimal solution is including turning Hair beamforming vectors and cognitive beamforming vectors, and then the safe rate of primary user and time user is solved, complete cognitive nothing The design of the safe beam forming of gauze network.

Further, objective optimisation problems are as follows in the step one：

s.t.

C4:0≤α<1

Wherein, T is expressed as the overall process time of cooperative cognitive wireless network, and α is that energy gathers in time ratio, w_PIt is secondary user Forwarding main system beamforming vectors, w_SFor subsystem sends beamforming vectors；

P_PIt is the average transmitting power of primary user's transmitting terminal, h_PSTRepresent primary user to the channel of time user, N₀It is noise work( Rate,It is main custom system demand rate,It is eavesdropping end user system limiting speed, η is energy conversion efficiency, η ∈ [0, 1], ψ₀Time initial energy of user is represented,It is represented sequentially as time user to eavesdropping end, secondary user to k-th Eavesdropping end, secondary user to the channel vector h for receiving user_SS、h_SPConjugate transposition, h_PP、h_PSWithRepresent respectively primary Family to receive user, subsystem to receive user, main system to k-th eavesdropping put between channel vector；n_PR、WithPoint Not Biao Shi primary user's receiving terminal, first eavesdropping point and k-th eavesdropping point place additive white Gaussian noise, K for eavesdrop end number；

In cognition wireless network primary user's transmitting terminal be PT, secondary user's transmitting terminal be ST, primary user's receiving terminal be PR, secondary use Family receiving terminal is SR, and, used as primary user's system, the transmission channel of ST to PR is used as secondary custom system, PT for the transmission channel of PT to PR Main system is formed to the transmission channel between ST, PR and SR, the transmission channel between ST to PR, SR forms subsystem, and main There is the signal that K-1 legal SR eavesdrops PT and ST in the coverage of system and subsystem.

Further, the objective optimisation problems described in step one are converted to half by the utilization Matrix Conjugate transposition principle It refers to utilize Matrix Conjugate transposition principle by w to determine relaxation problem_S、w_P、h_SS、h_SPChanged, appoint and take the energy harvesting time Than α, objective optimisation problems are converted into semidefinite decoding problem：

s.t.

Wherein,β_p、It is intermediate variable, Wherein Tr (i) is expressed as the mark of matrix；

Equal intermediate variable, With Respectively secondary user forwards the conjugate transposition of main system beamforming vectors, subsystem send wave The conjugate transposition of beam shaping vector.

Further, it is convex optimization problem by described semidefinite decoding problem equivalency transform to use Charnes-Cooper：

s.t.

C1:Tr(H_SSW_P)+λN₀=1

C5:W_P≥0,W_S≥0,λ≥0

Wherein, H_SS、H_SP、W_SAnd W_PIt is intermediate variable, Withλ is lax conversion contraction-expansion factor.

Further, the solution procedure for described convex optimization problem is as follows：

Step 1)：Set linear search precision Δ α, concurrently set energy harvesting the time than initial value；

Energy gather in the time than initial value according to practical application request set, span is 0-1, and value is smaller, searches The scope of rope is bigger.

Step 2)：Equation group to convex optimization problem is solved, and obtains local optimum solution vector

Step 3)：IfWithThen the local optimum solution vector of convex optimization problem is

Otherwise, the optimal solution vector of convex optimization problem isWhereinWithWherein, rank is expressed as rank of matrix；

Step 4)：Search value α=α+Δ α is updated, if α >=1, into step 5), otherwise, return to step 2)；

Step 5)：All of local optimum solution vector is substituted into convex optimization problem so that convex optimization problem is used for corresponding time Local optimum solution vector and corresponding energy harvesting time ratio when the transmission rate of family system is maximum is global optimum's solution vectorIt is rightWithCarry out Eigenvalues Decomposition EVD：Obtain primary user and time use The optimal safe rate at family

Beneficial effect

The invention provides a kind of method for designing of the safe beam forming based on energy harvesting cognition network, first with energy The amount harvesting time is used for variable, and the objective optimization for building the peak transfer rate of time custom system in cognition wireless network is asked Topic, and cause that objective optimisation problems meet the secure communication quality of primary user's system and the transmit power satisfaction of subsystem transmitting terminal Subsystem secure communication quality；Secondly, the objective optimisation problems described in step one are changed using Matrix Conjugate transposition principle It is semidefinite decoding problem, it is convex optimization problem by semidefinite decoding problem equivalency transform to use Charnes-Cooper；Finally by The linear search energy harvesting time is to forward beamforming vectors and cognitive beamforming vectors than obtaining globally optimal solution, and then The safe rate of primary user and time user is solved, the design of the safe beam forming of cognition wireless network is completed.By that will solve After changing twice, it is convex optimization to dissolve to the non-convex optimization problem of time custom system peak transfer rate in cognition wireless network Problem solving, greatly simplify design process, meanwhile, the solution scheme for being proposed can not only prevent eavesdropping user to secrecy The intercepting and capturing of information, while can realize the increase of transmission rate again, effectively raise the performance of system.

Brief description of the drawings

Fig. 1 is safe beamforming design method flow in a kind of harvesting cognition network based on energy of the present invention Figure；

Fig. 2 is system model；

Fig. 3 is the safe rate influence for eavesdropping nodes to secondary custom system；

Fig. 4 is safe rate influence of the initialization energy in ST on secondary custom system, (K=2)；

Fig. 5 is safe rate influence of the initialization energy in ST on primary user's system, (K=2).

Specific embodiment

Below in conjunction with example and accompanying drawing, the present invention is described further.

Embodiment 1：

By the indoor environment for designing a radio sensing network or WiFi and the shared 2.4GHz band resources of ZigBee In, wherein WiFi and ZigBee is respectively primary user and time user carries out data transmission, and emulation tool uses matlab.

As shown in figure 1, it is a kind of based on energy harvesting cognition network in safe beam forming method for designing, specifically include with Lower step：

Step 1：Time ratio is gathered in as optimized variable with energy, optimization mesh is turned to the transmission rate maximum of secondary custom system Mark, builds the safe beamforming design optimization problem that cognition wireless network is gathered in based on energy so that primary user's system meets The transmit power of secure communication quality requirement and secondary custom system transmitting terminal meets secure communication limitation.

As shown in Fig. 2 carrying out collaboration communication between a main system and a subsystem for energy constraint.Main system includes Transmission channel between PT to ST, PR and SR, subsystem includes the transmission channel between ST to PR, SR, while subsystem Coverage in also there is K-1 SR user and may eavesdrop the signal of PT, it is assumed that ST outfit N root antennas, other terminals are matched somebody with somebody Standby 1 antenna.Within the system, PT sends the data of secrecy to PR, and the frequency spectrum using primary user after ST receives information is provided Source carries out relay forwarding, while also sending unclassified data gives its corresponding receiving terminal SR.If the transmission energy of ST is too low, The efficiency of collaboration communication will also become very low.Therefore, time conversion relaying (TSR) agreement is employed at ST ends so that ST can be The alternate operation of energy harvesting and information processing is carried out in transmission time T.

Therefore, it is necessary to carry out obtaining energy from the transmission of primary user in advance before collaboration communication is carried out；Simultaneously in number According to the transmission stage, other the ZigBee users in effective range are likely to carry out monitoring decoding to main user data.In TSR associations In view, all times T is divided into three phases, as shown in table 1：

TSR agreements in table 1ST

(1) energy harvesting stage α T：

In this stage, PT sends special energy signal x_e, the energy signal that ST will be received using power conversion circuits Be converted to energy, PR, SR and SR_kDo not carry out any operation.Now according to TSR agreements, the energy ψ of ST harvestings_hIt is expressed as ψ_h=α T ηP_p|h_PST|²。

Wherein, η ∈ [0,1] are energy conversion efficiency；P_pIt is the average transmitting power at PT ends；h_PSTRepresent the letter of PT to ST Road vector, because the noise that antenna and rectifier are produced is too small, therefore the energy of harvesting is ignored.

(2) information reconnaissance phase (1- α) T/2

In this stage, PT sends security information x_PTo ST.Now ST receive signal be

Wherein, n_STFor average is 0, white complex gaussian noise, i.e. n are expressed as_ST, PR, SR1 and eavesdropping end SR_k(k∈{2,..., K }) signal of PT is also received in this stage.Now PR, SR1 and SR_kThe signal of reception is respectively

Wherein, h_PP, h_PSWithPT to PR, SR1 and k-th eavesdropping point SR are represented respectively_kChannel vector, n_PR,PR, SR1 and k-th eavesdropping point SR are represented respectively_kThe additive white Gaussian noise at place.Primary user's signal profit that ST will be received Forwarding (amplify-and-forward, AF) is amplified with maximum-ratio combing (maximal ratio combining, MRC) Process, therefore signal to be sent is expressed as

(3) information re-transmission stage (1- α) T/2：

In this stage, ST uses the remaining energy ψ 0 and energy ψ of harvesting_h, and using forwarding beamforming vectors w_PWith Cognitive beamforming vectors w_S, the security information of simultaneous transmission primary user and the information of their own.Now, PR, SR1 and SR_kReceive Signal be respectively：

Wherein, h_SP, h_SSWithST to PR, SR and k-th eavesdropping point SR are represented respectively_kChannel vector,

Then object function is established, the object function for combining safe beam forming optimization design is that maximized realization is secondary The transmission rate of user, while ensureing that PU meets the transmit power limitation of security restriction and ST in qualified function.Therefore, combine Optimization

s.t.

Problem (P1) formula is expressed as：

C4:0≤α<1

Step 2：The objective optimisation problems described in step one are converted into semidefinite decoding using Matrix Conjugate transposition principle Problem, it is convex optimization problem by semidefinite decoding problem equivalency transform to use Charnes-Cooper；

Realization and primary user's system of the peak transfer rate of time custom system are can be seen that from above combined optimization problem Demand rateEavesdropping end user system limiting speedAnd initialization energy is related to harvesting energy.Knowable to analysis (P1), Combined optimization problem (P1) is the optimization problem of non-convex, it is impossible to while it is time user's forwarding main system beamforming vectors to obtain w_P, it is that subsystem sends beamforming vectors w_SOptimization solution of the time than α is gathered in energy, in order to solve the combined optimization of non-convex Problem (P1) first appoint take energy gather in the time than α, optimization problem is converted into semidefinite decoding (SDR) problem.It is assumed that energy is gathered in Time ratioIt is the constant between 0-1, by variable w_PIt is expressed as

DefinitionWithProblem (P1) relaxation problem (P2) can be expressed as：

s.t.

Wherein,

Object function in problem (P2) is fractional form, therefore can be changed using Charnes-Cooper, is made WithRelaxation problem (P2) is equivalent It is (P3)

s.t.

C1:Tr(H_SSW_P)+λN₀=1

C5:W_P≥0,W_S≥0,λ≥0

Step 3：Time is gathered in than obtaining globally optimal solution by linear search energy, the globally optimal solution is including forwarding Beamforming vectors and cognitive beamforming vectors, and then the safe rate of primary user and time user is solved, complete cognition wireless The design of the safe beam forming of network；

Step 1)：Linear search precision Δ α=0.01 is set, concurrently set the energy harvesting time than initial value α= 0.1；

Step 2)：Equation group to convex optimization problem is solved, and obtains local optimum solution vector

Step 3)：IfWithThen the local optimum solution vector of convex optimization problem is

Otherwise, the optimal solution vector of convex optimization problem isWhereinWith

Step 4)：Search value α=α+Δ α is updated, if α >=1, into step 5), otherwise, return to step 2)；

Step 5)：All of local optimum solution vector is substituted into convex optimization problem so that convex optimization problem is used for corresponding time Local optimum solution vector and corresponding energy harvesting time ratio when the transmission rate of family system is maximum is global optimum's solution vectorIt is rightWithCarry out Eigenvalues Decomposition EVD：Obtain primary user and time The optimal safe rate of user

In the environment of simulation, it is assumed that the signal transmitting power P of PT_PRemaining energy ψ in=20dB, ST₀=10dB, hair Channel model between sending end and receiving terminal isD represents distance, and μ=3.5 represent path loss index, and ω is obeyed [0,2 π) be uniformly distributed.Noise normalized covariance N₀=1.It is assumed that the antenna number N=4 in ST, from ST to other-end Distance is 2m, and the distance of PT to PR is 4m；PR minimum essential requirement speedSR_kMonitor minimum needed for primary user's signal Speed

Step 4：Find safe rate influence of the eavesdropping nodes on secondary custom system.

Fig. 3 represented under different-energy conversion efficiency, eavesdropping node SR_kThe increase of quantity is to secondary custom system security performance Influence.From the figure, it can be seen that the safe rate of secondary custom system is reduced with the increase of eavesdropping nodes.Meanwhile, it is secondary The safe transmission speed of user is reduced with the reduction of energy conversion efficiency η, but prioritization scheme security performance still better than Security performance when noenergy is gathered in.Work as ψ₀When=0dB, η=0.8,0.5,0.3, when safe rate is gathered in than noenergy Safe rate is higher by about 0.85bit/s/Hz, 0.67bit/s/Hz and 0.5bit/s/Hz respectively.

Step 5：Find safe rate influence of the initialization energy in ST on secondary custom system, K=2.

Fig. 4 is illustrated under eavesdropping nodes K=2 and different energy conversion efficiencies, and the initialization energy of ST is to secondary use The influence of the safe rate of family system.It can be seen that the safe rate of secondary custom system is with ST initialization energy Increase and increase.In relatively low initialization energy range, secondary custom system security performance is substantially better than secondary when noenergy is gathered in The security performance of custom system.Even if during energy conversion efficiency η=0.3, the safe rate of secondary user is received still better than noenergy The safe rate for cutting.When energy is initialized in scope higher, the secondary user security speed of noenergy harvesting is close to energy Measure the secondary user security speed of harvesting.

Step 6：Find safe rate influence of the initialization energy in ST on primary user's system, K=2.

Fig. 5 is illustrated under eavesdropping nodes K=2 and different energy conversion efficiencies, and the initialization energy of ST is to primary The influence of the safe rate of family system.The wherein safe rate demand of primary user's systemCan from Fig. 5 Go out, it is low initialization energy range in (0dB-10dB), when scheme η=0.3 proposed by the present invention and noenergy harvesting feelings Under condition, the safe rate of PU can not meet demand.When energy conversion efficiency η=0.5, when 0.8, the safe rate of primary user PU The demand of safe rate is satisfied by whole initialization energy range.With the increase of initialization energy, gathered in using energy When PU safe rates be provided without energy gather in when PU safe rates move closer to.Thus illustrate in relatively low relay transmission Under energy, the transmission rate of PU can be influenceed by serious；With the lifting of energy conversion efficiency, the transmission energy of relaying also can Increase, therefore can also cause that primary user's speed meets transmission demand in relatively low initialization energy range.

Although the present invention has been presented for some embodiments of the present invention, it will be appreciated by those of skill in the art that Without departing from the spirit of the invention, the embodiments herein can be changed, above-described embodiment be it is exemplary, Should not be using the embodiments herein as the restriction of interest field of the present invention.

Claims (5)

1. it is a kind of based on energy harvesting cognition wireless network safe beam forming method for designing, it is characterised in that including with Lower step：

Step one：Time ratio is gathered in as optimized variable with energy, optimization aim is turned to the transmission rate maximum of secondary custom system, Build the safe beamforming design optimization problem that cognition wireless network is gathered in based on energy so that primary user's system meets safety The transmit power of QoS requirement and secondary custom system transmitting terminal meets secure communication limitation；

Step 2：The objective optimisation problems described in step one are converted into semidefinite decoding using Matrix Conjugate transposition principle to ask Topic, it is convex optimization problem by semidefinite decoding problem equivalency transform to use Charnes-Cooper；

Step 3：Time is gathered in than obtaining globally optimal solution by linear search energy, the globally optimal solution is including forwarding ripple Beam shaping vector sum cognition beamforming vectors, and then the safe rate of primary user and time user is solved, complete cognitive wireless The design of the safe beam forming of network.

2. method according to claim 1, it is characterised in that objective optimisation problems are as follows in the step one：

$\underset{w_S,w_P,\mathrm{\&alpha;}}{\max }\frac{\left(1-\mathrm{\&alpha;}\right)T}{2}{\log }_2\left(1+\frac{|h_{SS}^H{w}_S{|}^2}{\left(P_P\left|\right|h_{PST}|{|}^4+|\left|h_{PST}\right|{|}^2{N}_0\right)|h_{SS}^H{w}_P{|}^2+N_0}\right)$

s.t.

$C3:\left(P_P\right|\left|h_{PST}\right|{|}^4+\left|\right|h_{PST}\left|{|}^2{N}_0\right)|w_P{|}^2+|w_S{|}^2\&le;\frac{2({\mathrm{\&psi;}}_0+{\mathrm{\&alpha;T\&eta;P}}_p|h_{PST}{|}^2)}{(1-\mathrm{\&alpha;})T}$

C4:0≤α<1

Wherein, T is expressed as the overall process time of cooperative cognitive wireless network, and α is that energy gathers in time ratio, w_PFor secondary user forwards Main system beamforming vectors, w_SFor subsystem sends beamforming vectors；

P_PIt is the average transmitting power of primary user's transmitting terminal, h_PSTRepresent primary user to the channel of time user, N₀It is noise power, It is main custom system demand rate,It is eavesdropping end user system limiting speed, η is energy conversion efficiency, η ∈ [0,1], ψ₀Table Show time initial energy of user,Be represented sequentially as time user to eavesdropping end, secondary user to k-th eavesdrop end, Channel vector h of the secondary user to reception user_SS、h_SPConjugate transposition, h_PP、h_PSWithRepresent primary user to connecing respectively Receive user, subsystem to reception user, main system to the channel vector between k-th eavesdropping point；n_PR、WithRepresent respectively Additive white Gaussian noise at primary user's receiving terminal, first eavesdropping point and k-th eavesdropping point, K is eavesdropping end number；

Primary user's transmitting terminal is that PT, secondary user's transmitting terminal are that ST, primary user's receiving terminal are PR in cognition wireless network, and secondary user connects The transmission channel of receiving end SR, PT to PR as primary user's system, the transmission channel of ST to PR as secondary custom system, PT to ST, Transmission channel between PR and SR forms main system, and the transmission channel between ST to PR, SR forms subsystem, and main system with There is the signal that K-1 legal SR eavesdrops PT and ST in the coverage of subsystem.

3. method according to claim 2, it is characterised in that the utilization Matrix Conjugate transposition principle is by institute in step one It refers to utilize Matrix Conjugate transposition principle by w that the objective optimisation problems stated are converted to semidefinite decoding problem_S、w_P、h_SS、h_SPEnter Row conversion, appoints and takes the energy harvesting time than α, and objective optimisation problems are converted into semidefinite decoding problem：

$\underset{w_S,w_P}{max}\frac{Tr\left({\stackrel{\&OverBar;}{H}}_{SS}{\stackrel{\&OverBar;}{W}}_S\right)}{Tr\left({\stackrel{\&OverBar;}{H}}_{SS}{\stackrel{\&OverBar;}{W}}_P\right)+N_0}$

s.t.

$C3:Tr\left({\stackrel{\&OverBar;}{W}}_P\right)+Tr\left({\stackrel{\&OverBar;}{W}}_S\right)\&le;\frac{2({\mathrm{\&psi;}}_0+{\mathrm{\&alpha;T\&eta;P}}_p|\left|h_{PST}\right|{|}^2)}{(1-\mathrm{\&alpha;})T}$

Wherein,β_p、It is intermediate variable, Wherein Tr () is expressed as the mark of matrix；

Equal intermediate variable, With Respectively secondary user forwards the conjugate transposition of main system beamforming vectors, subsystem send wave The conjugate transposition of beam shaping vector.

4. method according to claim 3, it is characterised in that asked described semidefinite decoding using Charnes-Cooper Topic equivalency transform is convex optimization problem：

$\underset{w_S,w_P,\mathrm{\&lambda;}}{max}Tr\left(H_{SS}{W}_S\right)$

s.t.

C1:Tr(H_SSW_P)+λN₀=1

$C4:Tr\left(W_P\right)+Tr\left(W_S\right)\&le;\frac{2\mathrm{\&lambda;}({\mathrm{\&psi;}}_0+{\mathrm{\&alpha;T\&eta;P}}_p|\left|h_{PST}\right|{|}^2)}{(1-\mathrm{\&alpha;})T}$

C5:W_P≥0,W_S≥0,λ≥0

Wherein, H_SS、H_SP、W_SAnd W_PIt is intermediate variable, Withλ is lax conversion contraction-expansion factor.

5. method according to claim 4, it is characterised in that the solution procedure for described convex optimization problem is as follows：

Step 1)：Set linear search precision Δ α, concurrently set energy harvesting the time than initial value；

Step 2)：Equation group to convex optimization problem is solved, and obtains local optimum solution vector

Step 3)：IfWithThen the local optimum solution vector of convex optimization problem is

Otherwise, the optimal solution vector of convex optimization problem isWhereinWithWherein, rank is expressed as rank of matrix；

Step 4)：Search value α=α+Δ α is updated, if α >=1, into step 5), otherwise, return to step 2)；

Step 5)：All of local optimum solution vector is substituted into convex optimization problem so that corresponding user system of convex optimization problem Local optimum solution vector and corresponding energy harvesting time ratio when the transmission rate of system is maximum is global optimum's solution vectorIt is rightWithCarry out Eigenvalues Decomposition EVD：Obtain primary user and time The optimal safe rate of user