CN104507091A - Energy cooperation method based on mutual benefit in cognitive radio network - Google Patents

Abstract

The invention discloses an energy cooperation method based on mutual benefit in a cognitive radio network. The method adopts a time-division scheme, is implemented through two stages, and obtains optimal time slot assignment through maximizing outage capacity of a delay-sensitive cognitive user or ergodic capacity of a delay-non-sensitive cognitive user. According to the energy cooperation method based on mutual benefit in the cognitive radio network, the energy of spectrum sensing can be saved for the cognitive user, while an authorized user can harvest energy from a signal of the cognitive user, and the energy utilization rate is improved. The simulation result shows that compared with direct transmission, the performance of the authorized user can be improved, and more spectrum chances can be acquired by the cognitive user.

Description

Based on reciprocal benefited energy collaboration method in cognitive radio networks

Technical field

The present invention relates to cognitive user frequency spectrum access method and authorized user energy harvesting conceptual design in wireless communication technology field, particularly relate to the realization of frequency spectrum access under energy collaboration mode and energy harvesting method.

Background technology

Along with the develop rapidly of wireless technology and wireless device, the demand of frequency spectrum resource sharply rises, but traditional fixed frequency spectrum access mechanism does not consider the feature of frequency spectrum resource change over time and space, thus cause frequency spectrum resource waste, and then cause the availability of frequency spectrum low.The spectrum opportunities that cognitive radio technology can make full use of those uncommitted users' uses carrys out transmission information, thus improves spectrum efficiency, alleviates the nervous situation of frequency spectrum resource.In cognitive radio networks, cognitive user can be determined the untapped spectrum opportunities of those authorized users by frequency spectrum detection and use these spectrum opportunities to carry out transmission information.Or, cognitive user can with self information of authorized user shared channel transmission, but cognitive user to the interference of authorized user under an interference threshold.But due to the existence of perception mistake and interference threshold be difficult to determine, frequency spectrum sensing method and common transport scheme are difficult to ensure that the transmission of authorized user is by the impact of cognitive user.

Energy harvesting technology can extend the long journey life-span of wireless communication system and improve capacity usage ratio.And cognitive radio technology allows cognitive user dynamic access frequency spectrum resource to improve the availability of frequency spectrum.Therefore two kinds of technology can be utilized to improve the availability of frequency spectrum and the capacity usage ratio of network.For the authorized user of finite energy, the fixed energies supply of himself is difficult to ensure that it transmits reliably.To cooperate the energy of the signal gathering in cognitive user by carrying out energy with cognitive user, authorized user can improve its capacity usage ratio, and cognitive user can when without obtaining frequency spectrum access chance when perception simultaneously.But the report had not yet to see based on reciprocal benefited energy cooperation scheme.

Summary of the invention

The object of the present invention is to provide in a kind of cognitive radio networks based on reciprocal benefited energy collaboration method.The method can provide the frequency spectrum access determined chance, simultaneously for authorized user provides energy to carry out gathering in improve its capacity usage ratio for cognitive user.

For achieving the above object, present invention employs following technical scheme:

Adopt time division mechanism, each transmission time slot of cognitive radio networks is divided into two stages: the time span of first stage is α T, the time span of second stage is (1-α) T, and wherein α is the time slot allocation factor, and T is the length of each transmission time slot; At first stage, cognitive user insertion authority frequency spectrum also carries out cognition transmission, and authorized user carries out energy harvesting to the transmitting radio frequency signal of described cognitive user simultaneously; At second stage, described cognitive user stops transmission, and the energy that described authorized user utilization harvesting simultaneously obtains and the energy that homeostasis energy feed end provides transmit.

By maximizing the outage capacity of delay sensitive cognitive user, ensure the performance of delay sensitive authorized user simultaneously, or, by maximizing the ergodic capacity of the insensitive cognitive user of time delay, ensure the performance of the insensitive authorized user of time delay simultaneously, thus obtain the optimum time slot allocation factor.

At first stage, described authorized user selects the cognitive user s of a pair optimum _icarry out energy cooperation, cognitive user s _iselection criterion be:

Wherein, for the set that cognitive user is right, g _sipfor cognitive user s _itransmitting terminal to the channel power gain of the transmitting terminal of authorized user, for the transmitting terminal of other cognitive user is to the channel power gain of the transmitting terminal of authorized user.

For delay sensitive cognitive user and delay sensitive authorized user, solve following optimization problem by the method for linear search, obtain the optimum time slot allocation factor:

$\underset{\mathrm{\α}}{\max }{R}_{s_i}^{\lim }$

$s.t.R_p^{\lim }\≥R_{p,\mathrm{tar}}^{\lim }$

Wherein, for the target outage capacity that delay sensitive authorized user is preset, for the actual interrupt capacity of delay sensitive authorized user, for the actual interrupt capacity of delay sensitive cognitive user, s _irepresent that this delay sensitive cognitive user is a pair cognitive user of the optimum that described delay sensitive authorized user is selected according to described selection criterion.

The actual interrupt capacity of described delay sensitive authorized user and delay sensitive cognitive user is expressed as:

$R_p^{\lim }=(1-p_{\mathrm{out}}^p)R_p,R_{s_i}^{\lim }=(1-p_{\mathrm{out}}^{s_i})R_{s_i}$

Wherein, for the outage probability of described delay sensitive authorized user, R _pfor the transmission rate of described delay sensitive authorized user, the outage probability of described delay sensitive cognitive user, for the transmission rate of described delay sensitive cognitive user.

The outage probability of described delay sensitive authorized user and delay sensitive cognitive user is expressed as:

$\begin{array}{c}{P}_{\mathrm{out}}^p=\frac{1}{M}\underset{k=1}{\overset{M}{\mathrm{\Σ}}}\frac{{(-1)}^{k-1}}{{\mathrm{\σ}}_{\mathrm{sp}}^2}\left(\begin{array}{c}M\\ k\end{array}\right)-\frac{1}{M}\underset{k=1}{\overset{M}{\mathrm{\Σ}}}\frac{{(-1)}^{k-1}}{{\mathrm{\σ}}_{\mathrm{sp}}^2}\left(\begin{array}{c}M\\ k\end{array}\right)(\sqrt{\frac{{4\mathrm{k\γ}}_p(1-\mathrm{\α}){\mathrm{\σ}}_{\mathrm{sp}}^2{E}_s\mathrm{\ηT}}{{\mathrm{\σ}}_{\mathrm{pp}}^{2}k}}{K}_1\left(\sqrt{\frac{{4\mathrm{k\γ}}_p(1-\mathrm{\α})T}{E_s\mathrm{\η}{\mathrm{\σ}}_{\mathrm{sp}}^2{\mathrm{\σ}}_{\mathrm{pp}}^2}}\right)\\ -{\∫}_0^{E_p}\exp (-\frac{\mathrm{kx}}{{\mathrm{\σ}}_{\mathrm{sp}}^2}-\frac{{\mathrm{\γ}}_p(1-\mathrm{\α})T}{{\mathrm{\σ}}_{\mathrm{pp}}^2(E_p+E_s\mathrm{\ηx})})\mathrm{dx})\exp \left(\frac{{\mathrm{kE}}_p}{{\mathrm{\σ}}_{\mathrm{sp}}^2{E}_s\mathrm{\η}}\right)\\ P_{\mathrm{out}}^{s_i}=(1-\exp (-\frac{{\mathrm{\γ}}_s\mathrm{\αT}}{{\mathrm{\σ}}_{\mathrm{ss}}^2{E}_s}))\frac{1}{M}\end{array}$

Wherein, E _pfor the energy that each transmission time slot of stable energy feed end of authorized user provides, E _sfor the energy that each transmission time slot of stable energy feed end of cognitive user provides, η is energy harvesting efficiency, for the parameter of the exponential distribution that the transmitting terminal of cognitive user is obeyed to the channel power gain of the transmitting terminal of authorized user, for the parameter of the exponential distribution that the transmitting terminal of cognitive user is obeyed to the channel power gain of receiving terminal, for the parameter of the exponential distribution that the transmitting terminal of authorized user is obeyed to the channel power gain of receiving terminal, for the target interrupt rate of described delay sensitive authorized user, the target interrupt rate of described delay sensitive cognitive user, K ₁() is single order Bessel function.

For the insensitive cognitive user of time delay and the insensitive authorized user of time delay, solve following optimization problem by the method for linear search, obtain the optimum time slot allocation factor:

$\underset{\mathrm{\α}}{\max }{R}_{s_i}^{\mathrm{erg}}$

$s.t.R_p^{\mathrm{erg}}\≥R_{p,\mathrm{tar}}^{\mathrm{lunim}}$

Wherein, for the target ergodic capacity of the insensitive authorized user of described time delay, for the actual ergodic capacity of the insensitive authorized user of described time delay, for the actual ergodic capacity of the insensitive cognitive user of described time delay, s _irepresent that the insensitive cognitive user of this time delay is a pair cognitive user of the optimum that the insensitive authorized user of described time delay is selected according to described selection criterion.

The actual ergodic capacity of the insensitive authorized user of described time delay is expressed as:

$R_p^{\mathrm{erg}}={\∫}_0^{+\∞}{\log }_2(1+z)({2K}_1\left(a\right)-b)\exp \left(\frac{1}{E_s\mathrm{\η}{\mathrm{\σ}}_{\mathrm{sp}}^2}\right)\mathrm{dz}$

$\left\{\begin{array}{c}a=2\sqrt{\frac{(1-\mathrm{\α})\mathrm{Tz}}{E_s\mathrm{\η}{\mathrm{\σ}}_{\mathrm{sp}}^2{\mathrm{\σ}}_{\mathrm{pp}}^2}}\\ b={\∫}_0^{E_p}\frac{1}{y}\exp (-\frac{(1-\mathrm{\α})\mathrm{Tz}}{{\mathrm{\σ}}_{\mathrm{pp}}^{2}y}-\frac{y}{E_s\mathrm{\η}{\mathrm{\σ}}_{\mathrm{sp}}^2})\mathrm{dy}\end{array}\right.$

Wherein, K ₁() is single order Bessel function, E _pfor the energy that each transmission time slot of stable energy feed end of authorized user provides, E _sfor the energy that each transmission time slot of stable energy feed end of cognitive user provides, η is energy harvesting efficiency, g _ppfor the transmitting terminal of authorized user is to the channel power gain of receiving terminal, for the parameter of the exponential distribution that the transmitting terminal of cognitive user is obeyed to the channel power gain of the transmitting terminal of authorized user, the parameter of the exponential distribution that the transmitting terminal of authorized user is obeyed to the channel power gain of receiving terminal;

The actual ergodic capacity of the insensitive cognitive user of described time delay is expressed as:

$R_{s_i}^{\mathrm{erg}}=-\mathrm{\αexp}\left(\frac{\mathrm{\αT}}{E_s{\mathrm{\σ}}_{\mathrm{ss}}^2}\right)\mathrm{Ei}(-\frac{\mathrm{\αT}}{E_s{\mathrm{\σ}}_{\mathrm{ss}}^2})$

Wherein, the parameter of the exponential distribution that the transmitting terminal of cognitive user is obeyed to the channel power gain of receiving terminal, $\mathrm{Ei}(-v)=-{\∫}_v^{+\∞}{e}^{-t}{t}^{-1}\mathrm{dt}.$

Beneficial effect of the present invention is embodied in:

Of the present invention based in reciprocal benefited energy collaboration method, first cooperation stage, cognitive user insertion authority frequency spectrum, authorized user adopts the energy of the method harvesting cognitive user signal of energy harvesting simultaneously; Second cooperation stage, authorized user utilizes the energy of harvesting and the energy in the fixed energies source of self to transmit its own signal.The method makes cognitive user can save the energy of frequency spectrum perception, and authorized user can gather in energy from the signal of cognitive user, saves self-energy, improves capacity usage ratio.Meanwhile, simulation results show the present invention suggest plans, compared with directly transmitting, can be improved the performance of authorized user and make cognitive user obtain more spectrum opportunities.

Obtain the optimum time slot allocation factor by the ergodic capacity of the outage capacity or the insensitive cognitive user of time delay that maximize delay sensitive cognitive user in the present invention, thus cognitive user can be transmitted with higher speed.

Accompanying drawing explanation

Fig. 1 is cognitive radio networks energy cooperation schematic diagram; Energy harvest represents that energy gathers in, and First stage represents the first stage, and Second stage represents second stage;

Fig. 2 is the analogous diagram that authorized user and cognitive user throughput change with time slot distribution factor α;

Fig. 3 is that authorized user and cognitive user throughput are with cognitive user transmitting energy E _sthe analogous diagram of change.

Embodiment

Elaborate to the present invention below in conjunction with drawings and Examples, the explanation of the invention is not limited.

Consider cognitive radio networks system model as shown in Figure 1.In FIG, have a pair authorized user to comprise transmitting terminal (PT) and receiving terminal (PR), and authorized user adopt mixing energy supply mechanism.In order to ensure that authorized user obtains reliable and lasting energy supply, the transmitting terminal of authorized user can carry out energy harvesting from the signal of cognitive user transmission.Cognitive user system is made up of cognitive user transmitting terminal (ST) and receiving terminal (SR) M.Authorized user selects the cognitive user s of a pair optimum _icarry out energy cooperation to be supplied to the signal that authorized user carries out energy harvesting.

In this network, cognitive user and authorized user is synchronous and cognitive user system and authorized user system all experience steadily and independently Rayleigh block decline.Suppose that the length of each transmission time slot is T, and all channel statuss of each transmission time slot ensure constant, and in all channel independent variation of different transmission time slots.Link ST _i→ SR _i, ST _ithe channel power gain of → PT and PT → PR is respectively and g _pp.Because cognitive user system and authorized user system all experience Rayleigh fading, therefore variable and g _ppobedience parameter is with exponential distribution.In order to simplify calculating, suppose with obeying parameter is respectively with exponential distribution.In cognitive radio networks system model of the present invention, suppose that channel condition information is known.

In addition, suppose in energy harvesting process, noise signal energy can be ignored compared with harvesting energy.The energy harvesting efficiency of PT is η.The energy that the stable energy feed end of authorized user and each time slot of cognitive user provides is E _pand E _s.

Be divided into two stages based on reciprocal benefited energy cooperation in cognitive radio networks proposed by the invention, specific implementation process is:

At first stage, authorized user selects the cognitive user s of a pair optimum _icarry out energy cooperation, its collaboration user selection criterion is:

Namely choose the best cognitive user of authorized user transmitting end channel and carry out energy cooperation.Wherein for the set that cognitive user is right, namely have M in network to cognitive user, the cognitive user s of this optimum _ithe front α T time taking current time slots carries out broadcasting to send the signal of cognitive user, and authorized user carries out energy harvesting in section at this moment, and the transmission rate that now cognitive user obtains is:

$R_{s_i}=\mathrm{\α}{\log }_2(1+\frac{E_s}{\mathrm{\αT}}{g}_{s_i{s}_i})$

Wherein be the transmitted power of cognitive user, the energy that authorized user harvesting obtains is:

$E_h=E_s{g}_{s_{i}p}\mathrm{\η}$

α is the time slot allocation factor, and T is the length of transmission time slot;

At second stage, cognitive user stops transmission, and now authorized user utilizes the energy of harvesting to transmit authorization user signal in residue (1-α) T time of current time slots, and its through-put power is:

$P_p=\frac{E_p+E_s{g}_{s_{i}p}\mathrm{\η}}{(1-\mathrm{\α})T}$

Then now the transmission rate of authorized user is:

R _p＝(1-α)log ₂(1+P _pg _pp)

Cooperated by the energy of cognitive user, cognitive user obtains transmission opportunity, and authorized user can gather in energy thus guarantee transmitting.By maximizing the outage capacity of delay sensitive cognitive user, ensure the performance of delay sensitive authorized user simultaneously, or maximize the ergodic capacity of the insensitive cognitive user of time delay, ensure the performance of the insensitive authorized user of time delay simultaneously, thus obtain optimum time slot allocation factor-alpha.

1. the authorized user of delay sensitive and cognitive user

For latency sensitive user, outage capacity is adopted to weigh its performance.

For the authorized user of delay sensitive, its outage probability is:

$P_{\mathrm{out}}^p=\mathrm{Pr}(R_p<R_{\mathrm{tar}}^p)$

Wherein for the target interrupt rate of authorized user, according to the selection scheme of collaboration user, can the outage probability of authorized user be:

Wherein according to the selection criterion of cognitive user and the probability density function of channel coefficients and distribution function, optimum g can be obtained _sipprobability density function be:

$f\left(g_{s_{\mathrm{ip}}}\right)=\underset{k=1}{\overset{M}{\mathrm{\&Sigma;}}}\left(\begin{array}{c}M\\ k\end{array}\right)\frac{{(-1)}^{k+1}}{{\mathrm{\&sigma;}}_{\mathrm{sp}}^2}\exp (-\frac{{\mathrm{kg}}_{s_{i}p}}{{\mathrm{\&sigma;}}_{\mathrm{sp}}^2})$

Thus the outage probability of authorized user is:

$\begin{array}{c}{P}_{\mathrm{out}}^p=\frac{1}{M}\underset{k=1}{\overset{M}{\mathrm{\&Sigma;}}}\frac{{(-1)}^{k-1}}{{\mathrm{\&sigma;}}_{\mathrm{sp}}^2}\left(\begin{array}{c}M\\ k\end{array}\right)-\frac{1}{M}\underset{k=1}{\overset{M}{\mathrm{\&Sigma;}}}\frac{{(-1)}^{k-1}}{{\mathrm{\&sigma;}}_{\mathrm{sp}}^2}\left(\begin{array}{c}M\\ k\end{array}\right)(\frac{\sqrt{{4\mathrm{k\&gamma;}}_p(1-\mathrm{\&alpha;}){\mathrm{\&sigma;}}_{\mathrm{sp}}^2{E}_s\mathrm{\&eta;T}}}{{\mathrm{\&sigma;}}_{\mathrm{pp}}^{2}k}{K}_1\left(\sqrt{\frac{{4\mathrm{k\&gamma;}}_p(1-\mathrm{\&alpha;})T}{E_s\mathrm{\&eta;}{\mathrm{\&sigma;}}_{\mathrm{sp}}^2{\mathrm{\&sigma;}}_{\mathrm{pp}}^2}}\right)\\ -{\&Integral;}_0^{E_p}\exp (-\frac{\mathrm{kx}}{{\mathrm{\&sigma;}}_{\mathrm{sp}}^2}-\frac{{\mathrm{\&gamma;}}_p(1-\mathrm{\&alpha;})T}{{\mathrm{\&sigma;}}_{\mathrm{pp}}^2(E_p+E_s\mathrm{\&eta;x})})\mathrm{dx})\exp \left(\frac{{\mathrm{kE}}_p}{{\mathrm{\&sigma;}}_{\mathrm{sp}}^2{E}_s\mathrm{\&eta;}}\right)\end{array}$

Wherein K ₁() is single order Bessel function.Now the actual interrupt capacity of delay sensitive authorized user and throughput can be expressed as:

$R_p^{\lim }=(1-p_{\mathrm{out}}^p)R_p$

And for the cognitive user of delay sensitive, its outage probability is:

Wherein the target interrupt rate of cognitive user, utilizes the condition of Rayleigh fading and the selection scheme of collaboration user, can obtain the outage probability of cognitive user:

$P_{\mathrm{out}}^{s_i}=(1-\exp (-\frac{{\mathrm{\&gamma;}}_s\mathrm{\&alpha;T}}{{\mathrm{\&sigma;}}_{\mathrm{ss}}^2{E}_a}))\frac{1}{M}$

Wherein thus the actual interrupt capacity of delay sensitive cognitive user and throughput are:

$R_{s_i}^{\lim }=(1-p_{\mathrm{out}}^s)R_{s_i}$

By the design time slot allocation factor-alpha of optimum to maximize the outage capacity of cognitive user, ensure that the minimal disruption of authorized user is handled up demand simultaneously, following optimization problem can be obtained:

$\underset{\mathrm{\&alpha;}}{\max }{R}_{s_i}^{\lim }$

$s.t.R_p^{\lim }\&GreaterEqual;R_{p,\mathrm{tar}}^{\lim }$

Its the target outage capacity of delay sensitive authorized user;

Owing to being difficult to the closed solutions obtaining this problem, therefore the present invention's employing obtains the optimum time slot allocation factor to the method that time slot allocation factor-alpha carries out linear search.

2. the insensitive authorized user of time delay and cognitive user

For the insensitive user of time delay, ergodic capacity is adopted to weigh its performance.

For the insensitive authorized user of time delay, its actual ergodic capacity is:

Wherein representative is expected.Suppose $z=\frac{E_p+E_s{g}_{s_{i}p}\mathrm{\&eta;}}{(1-\mathrm{\&alpha;})T}{g}_{\mathrm{pp}},$ Can obtain:

Wherein thus the actual ergodic capacity of the insensitive authorized user of time delay is:

$R_p^{\mathrm{erg}}={\&Integral;}_0^{+\&infin;}{\log }_2(1+z)({2K}_1\left(a\right)-b)\exp \left(\frac{1}{E_s\mathrm{\&eta;}{\mathrm{\&sigma;}}_{\mathrm{sp}}^2}\right)\mathrm{dz}$

Wherein

$\left\{\begin{array}{c}a=2\sqrt{\frac{(1-\mathrm{\&alpha;})\mathrm{Tz}}{E_s\mathrm{\&eta;}{\mathrm{\&sigma;}}_{\mathrm{sp}}^2{\mathrm{\&sigma;}}_{\mathrm{pp}}^2}}\\ b={\&Integral;}_0^{E_p}\frac{1}{y}\exp (-\frac{(1-\mathrm{\&alpha;})\mathrm{Tz}}{{\mathrm{\&sigma;}}_{\mathrm{pp}}^{2}y}-\frac{y}{E_s\mathrm{\&eta;}{\mathrm{\&sigma;}}_{\mathrm{sp}}^2})\mathrm{dy}\end{array}\right.$

For the insensitive cognitive user of time delay, its actual ergodic capacity is:

According to probability density function and the distribution function of rayleigh fading channel coefficient, can obtain its actual ergodic capacity is:

$R_{s_i}^{\mathrm{erg}}=-\mathrm{\&alpha;exp}\left(\frac{\mathrm{\&alpha;T}}{E_s{\mathrm{\&sigma;}}_{\mathrm{ss}}^2}\right)\mathrm{Ei}(-\frac{\mathrm{\&alpha;T}}{E_s{\mathrm{\&sigma;}}_{\mathrm{ss}}^2})$

Wherein $\mathrm{Ei}(-v)=-{\&Integral;}_v^{+\&infin;}{e}^{-t}{t}^{-1}\mathrm{dt}.$

By the design time slot allocation factor-alpha of optimum to maximize the ergodic capacity of cognitive user, ensure the ergodic capacity demand that authorized user is minimum simultaneously, following optimization problem can be obtained:

$\underset{\mathrm{\&alpha;}}{\max }{R}_{s_i}^{\mathrm{erg}}$

$s.t.R_p^{\mathrm{erg}}\&GreaterEqual;R_{p,\mathrm{tar}}^{\mathrm{lunim}}$

Wherein the target ergodic capacity of the insensitive authorized user of time delay.

Owing to being difficult to the closed solutions obtaining this problem, therefore the present invention's employing obtains the optimum time slot allocation factor to the method that time slot allocation factor-alpha carries out linear search.

Emulation experiment:

In simulations, the present invention adopts 30 pairs of cognitive user random distribution.The stable energy feed end of cognitive user and authorized user is 0.125J at energy that each time slot provides.The interrupt rate of authorized user and cognitive user is 4bits/s/Hz and 2bits/s/Hz.The target outage capacity of delay sensitive authorized user is 3bit/s/Hz.And the insensitive authorized user of time delay can carry out 2 re-transmissions, its target ergodic capacity is 2bit/s/Hz.

In simulation analysis, consider that following Two Variables is on delay sensitive and the actual interrupt capacity of the insensitive cognitive user of time delay and authorized user and the impact of actual ergodic capacity:

1. time slot allocation factor-alpha;

2. cognitive user stable energy feed end provides ENERGY E _s;

Fig. 2 gives the variability situation of throughput along with time slot allocation factor-alpha of latency sensitive user and the insensitive user of time delay.As can be seen from the figure, along with the increase of α, the performance of authorized user will decline, and the performance of cognitive user rises.Because α increases, the transmission that cognitive user will have more time slot to carry out self, thus makes the transmission time slot of authorized user reduce, thus its hydraulic performance decline.Meanwhile, as can be seen from the figure the performance of the insensitive user of time delay is better than the performance of latency sensitive user.This is because the capacity of the insensitive user of time delay is ergodic capacity, its performance is the average influence of collaboration user, and latency sensitive user is when the collaboration user that selection one is optimum assists transmission, its outage capacity is easily subject to the impact of collaboration user channel state variations.In addition, also compare the performance that the performance of the authorized user of institute of the present invention extracting method and authorized user directly transmit in emulation, can find out that the present invention suggests plans and is better than the scheme of direct transferring when α is greater than a certain value.

Fig. 3 gives the throughput of latency sensitive user and the insensitive user of time delay along with cognitive user ENERGY E _schange curve.Cognitive user stable energy feed end provides ENERGY E _sduring lifting, cognitive user can be transmitted with larger power, and thus authorized user can gather in more energy for self transmission, then its increase of handling up.And cognitive user is owing to have employed larger power delivery, thus its throughput increases.

The invention discloses in cognitive radio networks a kind of based on reciprocal benefited energy cooperation scheme.In cognitive radio networks, cognitive user accesses the frequency spectrum resource of uncommitted user utilization by frequency spectrum perception, thus improves the availability of frequency spectrum.But due to the existence of perception mistake, the transmission of authorized user can be subject to the interference of cognitive user.In order to reduce the impact on authorized user, improving the availability of frequency spectrum and capacity usage ratio simultaneously, the present invention proposes based on reciprocal benefited energy cooperation scheme.This scheme is divided into two stages to realize.First cooperation stage, cognitive user insertion authority frequency spectrum, authorized user adopts the energy of the method harvesting cognitive user signal of energy harvesting simultaneously.Second cooperation stage, authorized user utilizes the energy of harvesting and the energy in the fixed energies source of self to transmit its own signal.In energy cooperation scheme of the present invention, cognitive user and authorized user can be benefited.Cognitive user can save the energy of frequency spectrum perception, and authorized user can gather in energy from the signal of cognitive user, saves self-energy, improves capacity usage ratio.The outage capacity of latency sensitive user and the ergodic capacity of the insensitive user of time delay is analyzed respectively in the present invention.The optimum time slot allocation factor is obtained by the outage capacity of cognitive user and the ergodic capacity of the insensitive cognitive user of time delay that maximize delay sensitive.Simulation results show the present invention suggest plans, compared with directly transmitting, can be improved the performance of authorized user and make cognitive user obtain more spectrum opportunities.

Claims (8)

1. in cognitive radio networks based on reciprocal benefited energy collaboration method, it is characterized in that: adopt time division mechanism, each transmission time slot of cognitive radio networks is divided into two stages: the time span of first stage is α T, the time span of second stage is (1-α) T, wherein α is the time slot allocation factor, and T is the length of each transmission time slot; At first stage, cognitive user insertion authority frequency spectrum also carries out cognition transmission, and authorized user carries out energy harvesting to the transmitting radio frequency signal of described cognitive user simultaneously; At second stage, described cognitive user stops transmission, and the energy that described authorized user utilization harvesting simultaneously obtains and the energy that homeostasis energy feed end provides transmit.

2. according to claim 1 in cognitive radio networks based on reciprocal benefited energy collaboration method, it is characterized in that: by maximizing the outage capacity of delay sensitive cognitive user, ensure the performance of delay sensitive authorized user simultaneously, or, by maximizing the ergodic capacity of the insensitive cognitive user of time delay, ensure the performance of the insensitive authorized user of time delay simultaneously, thus obtain the optimum time slot allocation factor.

3. according to claim 1 in cognitive radio networks based on reciprocal benefited energy collaboration method, it is characterized in that: at first stage, described authorized user selects the cognitive user s of a pair optimum _icarry out energy cooperation, cognitive user s _iselection criterion be:

Wherein, for the set that cognitive user is right, g _sipfor cognitive user s _itransmitting terminal to the channel power gain of the transmitting terminal of authorized user.

4. according to claim 3 in cognitive radio networks based on reciprocal benefited energy collaboration method, it is characterized in that: for delay sensitive cognitive user and delay sensitive authorized user, solve following optimization problem by the method for linear search, obtain the optimum time slot allocation factor:

$\underset{\mathrm{\&alpha;}}{\max }{R}_{s_i}^{\lim }$

$s.t.R_p^{\lim }\&GreaterEqual;R_{p,\mathrm{tar}}^{\lim }$

Wherein, for the target outage capacity that delay sensitive authorized user is preset, for the actual interrupt capacity of delay sensitive authorized user, for the actual interrupt capacity of delay sensitive cognitive user, s _irepresent that this delay sensitive cognitive user is a pair cognitive user of the optimum that described delay sensitive authorized user is selected according to described selection criterion.

5. according to claim 4 in cognitive radio networks based on reciprocal benefited energy collaboration method, it is characterized in that: the actual interrupt capacity of described delay sensitive authorized user and delay sensitive cognitive user is expressed as:

$R_p^{\lim }=(1-p_{\mathrm{out}}^p)R_p,R_{s_i}^{\lim }=(1-p_{\mathrm{out}}^{s_i})R_{s_i}$

Wherein, for the outage probability of described delay sensitive authorized user, R _pfor the transmission rate of described delay sensitive authorized user, for the outage probability of described delay sensitive cognitive user, for the transmission rate of described delay sensitive cognitive user.

6. according to claim 5 in cognitive radio networks based on reciprocal benefited energy collaboration method, it is characterized in that: the outage probability of described delay sensitive authorized user and delay sensitive cognitive user is expressed as:

$\begin{array}{c}{P}_{\mathrm{out}}^p=\frac{1}{M}\underset{k=1}{\overset{M}{\mathrm{\&Sigma;}}}\frac{{(-1)}^{k-1}}{{\mathrm{\&sigma;}}_{\mathrm{sp}}^2}\left(\begin{array}{c}M\\ k\end{array}\right)-\frac{1}{M}\underset{k=1}{\overset{M}{\mathrm{\&Sigma;}}}\frac{{(-1)}^{k-1}}{{\mathrm{\&sigma;}}_{\mathrm{sp}}^2}\left(\begin{array}{c}M\\ k\end{array}\right)(\sqrt{\frac{{4\mathrm{k\&gamma;}}_p(1-\mathrm{\&alpha;}){\mathrm{\&sigma;}}_{\mathrm{sp}}^2{E}_s\mathrm{\&eta;T}}{{\mathrm{\&sigma;}}_{\mathrm{pp}}^{2}k}}{K}_1\left(\sqrt{\frac{{4\mathrm{k\&gamma;}}_p(1-\mathrm{\&alpha;})T}{E_s\mathrm{\&eta;}{\mathrm{\&sigma;}}_{\mathrm{sp}}^2{\mathrm{\&sigma;}}_{\mathrm{pp}}^2}}\right)\\ -{\&Integral;}_0^{E_p}\exp (-\frac{\mathrm{kx}}{{\mathrm{\&sigma;}}_{\mathrm{sp}}^2}-\frac{{\mathrm{\&gamma;}}_p(1-\mathrm{\&alpha;})T}{{\mathrm{\&sigma;}}_{\mathrm{pp}}^2(E_p+E_s\mathrm{\&eta;x})})\mathrm{dx}\left)\exp \right(\frac{{\mathrm{kE}}_p}{{\mathrm{\&sigma;}}_{\mathrm{sp}}^2{E}_s\mathrm{\&eta;}})\end{array}$

$P_{\mathrm{out}}^{s_i}=(1-\exp (-\frac{{\mathrm{\&gamma;}}_s\mathrm{\&alpha;T}}{{\mathrm{\&sigma;}}_{\mathrm{ss}}^2{E}_s}))\frac{1}{M}$

Wherein, E _pfor the energy that each transmission time slot of stable energy feed end of authorized user provides, E _sfor the energy that each transmission time slot of stable energy feed end of cognitive user provides, η is energy harvesting efficiency, for the parameter of the exponential distribution that the transmitting terminal of cognitive user is obeyed to the channel power gain of the transmitting terminal of authorized user, for the parameter of the exponential distribution that the transmitting terminal of cognitive user is obeyed to the channel power gain of receiving terminal, for the parameter of the exponential distribution that the transmitting terminal of authorized user is obeyed to the channel power gain of receiving terminal, for the target interrupt rate of described delay sensitive authorized user, for the target interrupt rate of described delay sensitive cognitive user, K ₁() is single order Bessel function.

7. according to claim 3 in cognitive radio networks based on reciprocal benefited energy collaboration method, it is characterized in that: for the insensitive cognitive user of time delay and the insensitive authorized user of time delay, solve following optimization problem by the method for linear search, obtain the optimum time slot allocation factor:

$\underset{\mathrm{\&alpha;}}{\max }{R}_{s_i}^{\mathrm{erg}}$

$s.t.R_p^{\mathrm{erg}}\&GreaterEqual;R_{p,\mathrm{tar}}^{\mathrm{un\; lim}}$

Wherein, for the target ergodic capacity of the insensitive authorized user of described time delay, for the actual ergodic capacity of the insensitive authorized user of described time delay, for the actual ergodic capacity of the insensitive cognitive user of described time delay, s _irepresent that the insensitive cognitive user of this time delay is a pair cognitive user of the optimum that the insensitive authorized user of described time delay is selected according to described selection criterion.

8. according to claim 7 in cognitive radio networks based on reciprocal benefited energy collaboration method, it is characterized in that: the actual ergodic capacity of the insensitive authorized user of described time delay is expressed as:

$R_p^{\mathrm{erg}}={\&Integral;}_0^{+\&infin;}{\log }_2(1+z)({2K}_1\left(a\right)-b)\exp \left(\frac{1}{E_s\mathrm{\&eta;}{\mathrm{\&sigma;}}_{\mathrm{sp}}^2}\right)\mathrm{dz}$

$\left\{\begin{array}{c}a=2\sqrt{\frac{(1-\mathrm{\&alpha;})\mathrm{Tz}}{E_s\mathrm{\&eta;}{\mathrm{\&sigma;}}_{\mathrm{sp}}^2{\mathrm{\&sigma;}}_{\mathrm{pp}}^2}}\\ b={\&Integral;}_0^{E_p}\frac{1}{y}\exp (-\frac{(1-\mathrm{\&alpha;})\mathrm{Tz}}{{\mathrm{\&sigma;}}_{\mathrm{pp}}^{2}y}-\frac{y}{E_s\mathrm{\&eta;}{\mathrm{\&sigma;}}_{\mathrm{sp}}^2})\mathrm{dz}\end{array}\right.$

Wherein, K ₁() is single order Bessel function, E _pfor the energy that each transmission time slot of stable energy feed end of authorized user provides, E _sfor the energy that each transmission time slot of stable energy feed end of cognitive user provides, η is energy harvesting efficiency, g _ppfor the transmitting terminal of authorized user is to the channel power gain of receiving terminal, for the parameter of the exponential distribution that the transmitting terminal of cognitive user is obeyed to the channel power gain of the transmitting terminal of authorized user, for the parameter of the exponential distribution that the transmitting terminal of authorized user is obeyed to the channel power gain of receiving terminal;

The actual ergodic capacity of the insensitive cognitive user of described time delay is expressed as:

$R_{s_i}^{\mathrm{erg}}=-\mathrm{\&alpha;exp}\left(\frac{\mathrm{\&alpha;T}}{E_s{\mathrm{\&sigma;}}_{\mathrm{ss}}^2}\right)\mathrm{Ei}(-\frac{\mathrm{\&alpha;T}}{E_s{\mathrm{\&sigma;}}_{\mathrm{ss}}^2})$

Wherein, for the parameter of the exponential distribution that the transmitting terminal of cognitive user is obeyed to the channel power gain of receiving terminal, $\mathrm{Ei}(-v)=-{\&Integral;}_v^{+\&infin;}{e}^{-t}{t}^{-1}\mathrm{dt}.$