CN105007585A - Power distribution method based on maximum outage probability energy efficiency - Google Patents

Abstract

The invention discloses a power distribution method based on maximum outage probability energy efficiency and mainly solves a problem that a conventional cognitive radio power distribution method cannot acquire energy efficiency maximization. The method comprises steps of: 1 setting and initializing a parameter; 2 solving a Lagrange multiplier [tau] satisfying an average sending power constraint condition and a Lagrange multiplier [mu] satisfying an average interference power constraint condition; computing sending power Pn based on an outage probability after the nth iteration according to the multipliers [tau] and [mu]; 4 computing an energy efficiency function fn ([eta]) and energy efficiency [eta]n when the sending power is Pn; and 5, determining the energy efficiency function fn ([eta]), and acquiring the optimum energy efficiency and the optimum sending power under the optimum energy efficiency if the energy efficiency function fn ([eta]) satisfies an iteration stop condition, or continuing the cycle until the energy efficiency function fn ([eta]) satisfies the iteration stop condition or the maximum iteration number is achieved, thereby obtaining the optimum sending power and the optimum sending power. The power distribution method has advantages of maximum energy efficiency, a few iteration stop steps, and easy implement, and can be used in wireless communication.

Description

Based on the power distribution method that outage probability efficiency is maximum

Technical field

The invention belongs to wireless communication technology field, particularly a kind of power distribution method maximum based on outage probability efficiency, can be used for the maximized power division of secondary user's efficiency in green cognitive radio system.

Background technology

Along with developing rapidly of wireless and mobile communication, contradiction between growing wireless frequency spectrum demand and limited frequency spectrum resource has become the conspicuous contradiction of Current wireless communication industry, but meanwhile, there is again a large amount of phenomenon that frequency spectrum is idle or utilance is extremely low of authorizing.In order to improve the low present situation of the availability of frequency spectrum, the people such as J.Mitola propose the concept of cognitive radio, and its main thought is in the frequency range of having authorized, under the prerequisite not affecting primary user's proper communication, allow secondary user's to be linked into current frequency range, thus significantly improve the availability of frequency spectrum.Secondary user's transmission rate is maximized and the object as far as possible protecting authorized user in order to reach; the necessary optimal allocation transmitted power of secondary user's; to reduce the interference to authorized user proper communication as far as possible, the power division research therefore in cognitive radio receives the extensive concern of Chinese scholars.

Meanwhile, ubiquitous wireless traffic and the mobile device quantity sharply increased cause a large amount of energy ezpenditure and the discharge of greenhouse gas.Green communications network is that future wireless network designs inevitable trend.The thought of green communications network is, when maximization network efficiency, provides optimal user to experience.

Existing optimal power contribution strategy designs mainly for following two kinds of mechanism:

1) opportunistic spectrum access mechanism.The thought of opportunistic spectrum access mechanism is, secondary user's is under detecting that primary user does not exist situation, and secondary user's uses primary user's frequency range to transmit.Under this mechanism, secondary user's needs to detect primary user's frequency range quickly and accurately.Because existing frequency spectrum perception technology can not reach the Detection results of entirely accurate, when primary user does not exist, but when secondary user's erroneous judgement primary user exists, secondary user's can be abandoned using this frequency range to protect primary user; And when primary user exists, but when secondary user's erroneous judgement primary user does not exist, secondary user's uses primary user's frequency range to transmit, and will produce interference to primary user.Therefore the design of optimal power contribution strategy can not only play the effect of protection primary user in this mechanism, and can provide secondary user's peak transfer rate.

2) spectrum sharing mechanisms.Under spectrum sharing mechanisms, secondary user's and primary user share same frequency range, and secondary user's does not need to detect primary user's state.Under this mechanism, in order to ensure the service quality of primary user, secondary user's needs its transmitted power of optimal design.Due under spectrum sharing mechanisms, spectrum efficiency is higher and secondary user's can obtain better service quality, and therefore under spectrum sharing mechanisms, design optimal power contribution strategy is even more important.

Under traditional cognitive radio frequency spectrum shared mechanism, existing power distribution method (1:X.Kang, Y.C.Liang, A.Nallanathan, H.K.Garg, R.Zhang, " Optimal power allocation for fading channels incognitive radio networks:ergodic capacity and outage capacity " IEEE Trans.WirelessCommun., vol.8, no.2, pp.940-950, 2009.2:L.Musavian and S.Aissa, " Capacity and powerallocation for spectrum sharing communications in fading channels " IEEE Trans.WirelessCommun., vol.8, no.1, pp.148-156, Jan.2009.) this method is under given constraints, according to channel condition, by adjustment secondary user's transmitted power, reach and secondary user's outage probability is minimized.This power distribution method, only relevant to the noise power of the channel gain of secondary user's receiving terminal, primary user's transmitted power, secondary user's receiving terminal to primary user's receiving terminal, primary user's transmitting terminal to secondary user's receiving terminal, secondary user's transmitting terminal with constraints, secondary user's transmitting terminal, and irrelevant with the power amplification factor of efficiency and secondary user's transmitting terminal.This power distribution method, owing to not considering that efficiency that secondary user's obtains is on the impact of power division, then can not ensure that secondary user's obtains maximum efficiency, produce a large amount of additional energy consumption and the discharge of greenhouse gas, cause unnecessary energy waste.

Summary of the invention

The object of the invention is to for above-mentioned the deficiencies in the prior art, propose a kind of power distribution method maximum based on outage probability efficiency, to improve the efficiency of secondary user's, reduce energy waste.

For achieving the above object, technical method of the present invention comprises the steps:

(1) secondary user's is according to required fault-tolerant error, Lagrangian iteration effect, the outage capacity of wishing acquisition and maximum demand iterations, arranges the fault-tolerant error ξ > 0 of efficiency function, outage capacity r _sbit/multiple dimension, maximum iteration time N, the convergence error ξ that average transmitting power constraint is corresponding ₁> 0, the convergence error ξ that average interference power constraint is corresponding ₂> 0, the Lagrange multiplier iteration step length t that average transmitting power constraint is corresponding ₁> 0, the Lagrange multiplier iteration step length t that average interference power constraint is corresponding ₂> 0;

(2) secondary user's initialization efficiency η=0, Lagrange multiplier τ=τ that average transmitting power constraint is corresponding ₀, Lagrange multiplier μ=μ that average interference power constraint is corresponding ₀, secondary user's transmitted power P ⁿwith efficiency η ⁿiterations n=0;

(3) the best transmitted power P of secondary user's iterative computation:

(3.1) secondary user's meets secondary user's outage capacity r under calculating each fading condition _stransmitted power y:

$y=\frac{(2^{r_s}-1)(h_{ps}{P}_m+{\mathrm{\σ}}_w^2)}{g_{ss}},$

Wherein g _ssfor secondary user's transmitting terminal is to receiving terminal channel power gain, h _psfor primary user's transmitting terminal is to secondary user's receiving terminal channel power gain, P _mfor the constant transmitted power of primary user, represent the noise variance of secondary user's receiving terminal;

(3.2) secondary user's calculates the transmitted power P under each fading condition ⁿ:

$P^n=\left\{\begin{array}{cc}0,& y>\frac{1}{{\mathrm{\η}}^{n-1}\mathrm{\ρ}+{\mathrm{\μ}}_0{g}_{sp}+{\mathrm{\τ}}_0}\\ y,& y\≤\frac{1}{{\mathrm{\η}}^{n-1}\mathrm{\ρ}+{\mathrm{\μ}}_0{g}_{sp}+{\mathrm{\τ}}_0}\end{array}\right.,$

Wherein ρ is the power amplification factor, g _spfor secondary user's transmitting terminal is to primary user's receiving terminal channel power gain, η ^n-1for the efficiency that secondary user's (n-1)th iteration obtains;

(3.3) secondary user's is according to average transmitting power constraints with average interference power constraints by subgradient iterative algorithm through k>=1 time iteration, calculate the Lagrange multiplier τ that average transmitting power constraint is corresponding ^kthe Lagrange multiplier μ corresponding with average interference power constraint ^k:

${\mathrm{\τ}}^k={\[{\mathrm{\τ}}^{k-1}-t_1(\stackrel{\‾}{P_{th}}-E\{P_{k-1}^n\left\}\right)\]}^{+},$

${\mathrm{\μ}}^k={\[{\mathrm{\μ}}^{k-1}-t_2(\stackrel{\‾}{P_{In}}-E\{g_{sp}{P}_{k-1}^n\left\}\right)\]}^{+},$

Wherein with be respectively the constraint of secondary user's maximum average transmitting power and secondary user's retrains the maximum average interference power of primary user, E{} represents asking mathematic expectaion;

(3.4) according to the Lagrange multiplier τ calculated ^kand μ ^k, calculate transmitted power

$P_k^n=\left\{\begin{array}{cc}0,& y>\frac{1}{{\mathrm{\η}}^{n-1}\mathrm{\ρ}+{\mathrm{\μ}}^k{g}_{sp}+{\mathrm{\τ}}^k}\\ y,& y\≤\frac{1}{{\mathrm{\η}}^{n-1}\mathrm{\ρ}+{\mathrm{\μ}}^k{g}_{sp}+{\mathrm{\τ}}^k}\end{array}\right.;$

(3.5) the Lagrange multiplier τ that each iterative computation goes out is judged ^kand μ ^kwhether meet stopping criterion for iteration: $\left|{\mathrm{\τ}}^k(\stackrel{\‾}{P_{th}}-E\{P_k^n\left\}\right)\right|\≤{\mathrm{\ξ}}_1,\left|{\mathrm{\μ}}^k(\stackrel{\‾}{p_{In}}-E\{g_{sp}{P}_k^n\left\}\right)\right|\≤{\mathrm{\ξ}}_2,$ If meet, then perform step (3.6), otherwise, return step (3.3);

(3.6) secondary user's calculates n-th iteration efficiency function f respectively _n(η) He the n-th iteration efficiency η ⁿ:

$f_n\left(\mathrm{\η}\right)=E\{1-{\mathrm{\χ}}_s\left(P_k^n\right)\}-{\mathrm{\η}}^{n-1}E\{{\mathrm{\ρP}}_k^n+P_C\},$

${\mathrm{\η}}^n=\frac{E\{1-{\mathrm{\χ}}_s\left(P_k^n\right)\}}{E\{{\mathrm{\ρP}}_k^n+P_C\}},$

Wherein P _cfor the consumed power of permanent circuit, calculation expression be:

(3.7) secondary user's is to efficiency function f _n(η) adjudicate: if | f _n(η) |≤ξ, the then transmitted power of n-th time for secondary user's efficiency best transmitted power P, efficiency η ⁿbe the maximum efficiency η that secondary user's obtains; Otherwise, judge whether iterations reaches maximum iteration time n≤N, if reach maximum iteration time, then transmitted power now for secondary user's efficiency best transmitted power P, efficiency η ⁿfor the maximum efficiency η that secondary user's obtains; Otherwise, continue iteration, until meet iteration ends constraints.

The present invention has the following advantages:

1, the present invention is under secondary user's average transmitting power and average interference power constraints, can obtain the maximum efficiency obtained based on the best transmit power method of frequency spectrum share cognitive radio higher than tradition.

2, the present invention can obtain the efficiency optimal power contribution in maximum efficiency situation fast.

3, the present invention while guarantee primary user service quality, can ensure the QoS of customer of secondary user's in maximum efficiency situation.

4, computation complexity of the present invention is low, can extensive use in practice.

Accompanying drawing explanation

Fig. 1 is realization flow figure of the present invention;

Fig. 2 adopts the present invention and existing two kinds of power distribution methods, the maximum efficiency comparison diagram that its secondary user's obtains;

Fig. 3 adopts the present invention and existing two kinds of power distribution methods, and the probability comparison diagram interrupted occurs its secondary user's;

Fig. 4 adopts the present invention under different channels model, the maximum efficiency figure that secondary user's obtains;

Fig. 5 adopts the present invention and existing two kinds of transmit power method, the maximum efficiency comparison diagram that its secondary user's obtains under different transmitted power.

Embodiment

With reference to Fig. 1, performing step of the present invention is as follows:

Step 1, cognitive user Offered target parameter.

Secondary user's, according to required fault-tolerant error, Lagrangian iteration effect, the outage capacity of wishing acquisition and maximum demand iterations, arranges the fault-tolerant error ξ > 0 of efficiency function, outage capacity r _sbit/multiple dimension, maximum iteration time N, the convergence error ξ that average transmitting power constraint is corresponding ₁> 0, the convergence error ξ that average interference power constraint is corresponding ₂> 0, the Lagrange multiplier iteration step length t that average transmitting power constraint is corresponding ₁> 0, the Lagrange multiplier iteration step length t that average interference power constraint is corresponding ₂> 0;

The fault-tolerant error of efficiency function is less, and the iterations that may need is more, and iterations also depends on average interference constraints, average transmitting power constraints, road fading condition and efficiency optimum power level size.The selection of iteration step length is the key influence factor of step number needed for iteration stopping, loose according to constraints, selects suitable iteration step length, can ensure to obtain optimum solution fast, when iteration step length is set to constant, what subgradient algorithm can ensure to obtain dissociates optimum solution closely;

Step 2, initialization secondary user's parameter.

The selection of Lagrange multiplier initial value is larger on step number impact needed for iteration, when the Lagrangian initial value selected is close to when meeting the Lagrange multiplier of constraints, needed for iteration stopping, step number is less, if the initial value selected is undesirable, subgradient algorithm needs successive ignition just can obtain final Lagrange multiplier.Therefore, the selection of Lagrangian initial value is extremely important, usually suitably selects according to the loose of constraints, and when constraints is tighter, Lagrangian initial value is selected relatively large, otherwise Lagrange multiplier initial value is selected relatively little;

Secondary user's initialization efficiency η=0 in this example, Lagrange multiplier τ=τ that average transmitting power constraint is corresponding ₀, Lagrange multiplier μ=μ that average interference power constraint is corresponding ₀, secondary user's transmitted power P ⁿwith efficiency η ⁿiterations n=0;

Step 3, the best transmitted power P of secondary user's iterative computation.

(3.1) secondary user's ensures secondary user's outage capacity r under calculating each fading condition _sminimum transmit power y:

$y=\frac{(2^{r_s}-1)(h_{ps}{P}_m+{\mathrm{\σ}}_w^2)}{g_{ss}},$

Wherein g _ssfor secondary user's transmitting terminal is to receiving terminal channel power gain, h _psfor primary user's transmitting terminal is to secondary user's receiving terminal channel power gain, P _mfor the constant transmitted power of primary user, represent the noise variance of secondary user's receiving terminal;

(3.2) secondary user's calculates the transmitted power P under each fading condition ⁿ:

$P^n=\left\{\begin{array}{cc}0,& y>\frac{1}{{\mathrm{\η}}^{n-1}\mathrm{\ρ}+{\mathrm{\μ}}_0{g}_{sp}+{\mathrm{\τ}}_0}\\ y,& y\≤\frac{1}{{\mathrm{\η}}^{n-1}\mathrm{\ρ}+{\mathrm{\μ}}_0{g}_{sp}+{\mathrm{\τ}}_0}\end{array}\right.,$

Wherein ρ is the power amplification factor, g _spfor secondary user's transmitting terminal is to primary user's receiving terminal channel power gain, η ^n-1for the efficiency that secondary user's (n-1)th iteration obtains;

According to the calculation expression of the transmitted power under each fading condition, can see that the transmitted power of each fading condition can be adaptive according to channel status situation adjustment transmitted power, thus can reach under various fading condition, average efficiency is best;

(3.3) secondary user's is according to average transmitting power constraints with average interference power constraints by subgradient iterative algorithm through k>=1 time iteration, calculate the Lagrange multiplier τ that average transmitting power constraint is corresponding ^kthe Lagrange multiplier μ corresponding with average interference power constraint ^k:

${\mathrm{\τ}}^k={\[{\mathrm{\τ}}^{k-1}-t_1(\stackrel{\‾}{P_{th}}-E\{P_{k-1}^n\left\}\right)\]}^{+},$

${\mathrm{\μ}}^k={\[{\mathrm{\μ}}^{k-1}-t_2(\stackrel{\‾}{P_{In}}-E\{g_{sp}{P}_{k-1}^n\left\}\right)\]}^{+},$

Wherein with be respectively the constraint of secondary user's maximum average transmitting power and secondary user's retrains the maximum average interference power of primary user, E{} represents asking mathematic expectaion;

Described maximum average transmitting power constraint and maximum average interference power constraints loose, on step number needed for iteration stopping, there is larger impact, when maximum average transmitting power constraint and maximum average interference power retrain looser, needed for iteration stopping, step number is less, otherwise step number is larger needed for iteration stopping;

(3.4) according to the Lagrange multiplier τ calculated ^kand μ ^k, calculate transmitted power

$P_k^n=\left\{\begin{array}{cc}0,& y>\frac{1}{{\mathrm{\η}}^{n-1}\mathrm{\ρ}+{\mathrm{\μ}}^k{g}_{sp}+{\mathrm{\τ}}^k}\\ y,& y\≤\frac{1}{{\mathrm{\η}}^{n-1}\mathrm{\ρ}+{\mathrm{\μ}}^k{g}_{sp}+{\mathrm{\τ}}^k}\end{array}\right.;$

(3.5) the Lagrange multiplier τ that each iterative computation goes out is judged ^kand μ ^kwhether meet stopping criterion for iteration: $\left|{\mathrm{\τ}}^k(\stackrel{\‾}{P_{th}}-E\{P_k^n\left\}\right)\right|\≤{\mathrm{\ξ}}_1,\left|{\mathrm{\μ}}^k(\stackrel{\‾}{p_{In}}-E\{g_{sp}{P}_k^n\left\}\right)\right|\≤{\mathrm{\ξ}}_2,$ If meet, then perform step (3.6), otherwise, return step (3.3);

(3.6) secondary user's calculates n-th iteration efficiency function f respectively _n(η) He the n-th iteration efficiency η ⁿ:

$f_n\left(\mathrm{\η}\right)=E\{1-{\mathrm{\χ}}_s\left(P_k^n\right)\}-{\mathrm{\η}}^{n-1}E\{{\mathrm{\ρP}}_k^n+P_C\},$

${\mathrm{\η}}^n=\frac{E\{1-{\mathrm{\χ}}_s\left(P_k^n\right)\}}{E\{{\mathrm{\ρP}}_k^n+P_C\}},$

Wherein P _cfor permanent circuit consumed power, calculation expression be:

What efficiency function can react that secondary user's under per unit joule power obtains goes through state capacity, and namely under the various fade condition of channel, user obtains the mathematic expectaion of efficiency, thus embodies the average efficiency of secondary user's;

As can be seen from efficiency calculation expression, the maximization of efficiency, under being not equal to conventional cognitive radio, goes through state maximum capacity, therefore goes through the best transmitted power under state maximum capacity under conventional cognitive radio, can not ensure that secondary user's obtains maximum efficiency;

(3.7) secondary user's is to efficiency function f _n(η) adjudicate: if | f _n(η) |≤ξ, the then transmitted power of n-th time for secondary user's efficiency best transmitted power P, efficiency η ⁿbe the maximum efficiency η that secondary user's obtains; Otherwise, judge whether iterations reaches maximum iteration time n≤N, if reach maximum iteration time, then transmitted power now for secondary user's efficiency best transmitted power P, efficiency η ⁿfor the maximum efficiency η that secondary user's obtains; Otherwise, continue iteration, until meet iteration ends constraints;

The selection of maximum iteration time, the fault-tolerant error size reached can be needed to select according to secondary user's, if the fault-tolerant error that secondary user's needs is very little, then maximum iteration time is selected large, otherwise, secondary user's can select relatively smaller maximum iteration time, thus can obtain efficiency and power sending strategy fast.

The impact of performance of the present invention can be further illustrated by following emulation:

A, simulated conditions

Secondary user's transmitting terminal power amplification factor ρ and circuit constant power consume P _cbe set to 0.2 and 0.05 watt respectively, secondary user's receives noise variance and is set to 0.01, primary user through-put power P _mbe set to 60 milliwatts, Lagrangian iteration step length t ₁, t ₂all be set to 0.1, fault-tolerant error ξ, ξ ₁, ξ ₂all be set to 0.0001, it is 100000, g that channel realizes number of times _ss, g _spand h _psfor power gain under Rayleigh channel, obeys index distribution, average is set to 2,1.5 and 1.5 respectively, secondary user's target outage capacity r _sbe set to 1 bit/multiple dimension.

The average transmitting power constraint of emulation 1 and emulation 2 is set to 100 milliwatts, and average interference power is set to 0 milliwatt to 100 milliwatts.The m of the nagakami-m fading channel of emulation 3 is set to 0.5, and average transmitting power constraint is set to 100 milliwatts, and average interference power is set to 0 milliwatt to 100 milliwatts.The average interference power of emulation 4 is set to 10 milliwatts and 50 milliwatts, and average transmitting power is set to 0 milliwatt to 100 milliwatts.

B, emulation content

Emulation 1: adopt the present invention and the existing power distribution method minimum based on outage probability, contrast the maximum efficiency that secondary user's obtains, result as shown in Figure 2.The maximum efficiency that in Fig. 2, " efficiency maximization " expression adopts secondary user's of the present invention to obtain under the average transmitting power constraints of 100 milliwatts, " outage probability minimizes " represents that employing is based on the best transmit power method of traditional frequency spectrum share outage probability, the maximum efficiency that secondary user's obtains under the average transmitting power constraints of 100 milliwatts.

Emulation 2: adopt the present invention and the existing power distribution method minimum based on outage probability, contrast secondary user's generation outage probability, result as shown in Figure 3.The outage probability that in Fig. 3, " efficiency maximization " expression sampling secondary user's of the present invention obtains under the average transmitting power constraints of 100 milliwatts, " outage probability minimizes " represents that employing is based on the best transmit power method of traditional frequency spectrum share outage probability, the outage probability that secondary user's obtains under the average transmitting power constraints of 100 milliwatts.

Emulation 3: under different channels model, under average transmitting power is constrained to 100 milliwatt situations, the maximum efficiency that secondary user's adopts the present invention to obtain emulates, and result as shown in Figure 4.Four curves are had in Fig. 4, wherein:

Curve 1 expression the present invention is Gaussian channel at secondary user's transmitting terminal to secondary user's receiving terminal, primary user's transmitting terminal is Rayleigh channel to secondary user's receiving terminal, under secondary user's transmitting terminal is the channel model of Rayleigh channel to primary user's receiving terminal channel, the maximum efficiency that secondary user's obtains;

Curve 2 expression the present invention is Rayleigh channel at secondary user's transmitting terminal to secondary user's receiving terminal, nakagami-m fading channel when primary user's transmitting terminal be m is 0.5 to secondary user's receiving terminal, under secondary user's transmitting terminal is the channel model of Rayleigh channel to primary user's receiving terminal channel, the maximum efficiency that secondary user's obtains;

Curve 3 expression the present invention is Rayleigh channel at secondary user's transmitting terminal to secondary user's receiving terminal, primary user's transmitting terminal is Rayleigh channel to secondary user's receiving terminal, under nakagami-m fading channel model when secondary user's transmitting terminal be m is 0.5 to primary user's receiving terminal channel, the maximum efficiency that secondary user's obtains;

Curve 4 expression the present invention is Rayleigh channel at secondary user's transmitting terminal to secondary user's receiving terminal, primary user's transmitting terminal is Rayleigh channel to secondary user's receiving terminal, under secondary user's transmitting terminal is the channel model of Rayleigh channel to primary user's receiving terminal channel, the maximum efficiency that secondary user's obtains.

Emulation 4: adopt the present invention and the existing power distribution method minimum based on outage probability, the maximum efficiency obtained under different transmitted power secondary user's contrasts, and result as shown in Figure 5.

C, simulation result

Can be obtained by Fig. 2, under average interference power and average transmitting power constraints, existingly can not ensure that secondary user's obtains maximum efficiency based on the best transmit power method of frequency spectrum share outage probability, and the present invention can ensure that secondary user's obtains maximum efficiency.The present invention is compared with average transmitting power constraints, average interference power constraints is loose, namely when average interference power does not play effect of contraction, the maximum efficiency that secondary user's obtains only depends on average transmitting power, average transmitting power constraint is looser, and the maximum efficiency that secondary user's obtains is larger.

Can be obtained by Fig. 3, although the present invention can not ensure that secondary user's Transmission probability is minimum, can ensure that secondary user's obtains maximum efficiency.

Can be obtained by Fig. 4, the maximum efficiency that secondary user's transmitting terminal obtains to the channel fading of secondary user's receiving terminal for secondary user's plays detrimental effect, secondary user's transmitting terminal plays advantageous effect to the channel fading of secondary user's receiving terminal to the maximum efficiency that secondary user's obtains to primary user's receiving terminal and primary user's transmitting terminal, and primary user's transmitting terminal is more conducive to secondary user's to the decline of secondary user's receiving terminal and obtains higher maximum efficiency.Its reason is, secondary user's transmitting terminal can increase the outage probability of secondary user's to the decline of secondary user's receiving terminal, and secondary user's transmitting terminal can play to the decline of primary user's receiving terminal the effect reduced primary user's interference, primary user's transmitting terminal can play to the channel fading of primary user's receiving terminal the effect reduced secondary user's interference, thus reduce the outage probability of secondary user's, promote the maximum efficiency of secondary user's.

Can be obtained by Fig. 5, the present invention can ensure that secondary user's obtains maximum efficiency, and existing method can not ensure that secondary user's obtains maximum efficiency.Under " average transmission power constraints is tighter; average interference power constraint is more loose " this situation, best transmitted power only depends on average transmission power, and now the best transmitted power of two kinds is identical, thus two kinds of power distribution methods can obtain maximum efficiency; And under " average transmission power constraints is more loose, and average interference power constraint is tighter " this situation, best transmitted power only depends on average interference power, and now the present invention can obtain higher efficiency.

Comprehensive above-mentioned simulation result and analysis, proposed by the invention based on outage probability efficiency optimal power contribution method, secondary user's can be made to obtain maximum efficiency, and needed for iteration stopping, step number is few, be easy to realize, this makes this invention can better be applied in practice.

Claims (3)

1., based on the power distribution method that outage probability efficiency is maximum, comprise the steps:

(1) secondary user's is according to required fault-tolerant error, Lagrangian iteration effect, the outage capacity of wishing acquisition and maximum demand iterations, arranges the fault-tolerant error ξ > 0 of efficiency function, outage capacity r _sbit/multiple dimension, maximum iteration time N, the convergence error ξ that average transmitting power constraint is corresponding ₁> 0, the convergence error ξ that average interference power constraint is corresponding ₂> 0, the Lagrange multiplier iteration step length t that average transmitting power constraint is corresponding ₁> 0, the Lagrange multiplier iteration step length t that average interference power constraint is corresponding ₂> 0;

(2) secondary user's initialization efficiency η=0, Lagrange multiplier τ=τ that average transmitting power constraint is corresponding ₀, Lagrange multiplier μ=μ that average interference power constraint is corresponding ₀, secondary user's transmitted power P ⁿwith efficiency η ⁿiterations n=0;

(3) the best transmitted power P of secondary user's iterative computation:

(3.1) secondary user's meets secondary user's outage capacity r under calculating each fading condition _sminimum transmit power y:

$y=\frac{(2^{r_s}-1)(h_{ps}{P}_m+{\mathrm{\σ}}_w^2)}{g_{ss}},$

Wherein g _ssfor secondary user's transmitting terminal is to receiving terminal channel power gain, h _psfor primary user's transmitting terminal is to secondary user's receiving terminal channel power gain, P _mfor the constant transmitted power of primary user, represent the noise variance of secondary user's receiving terminal;

(3.2) secondary user's calculates the transmitted power P under each fading condition ⁿ:

$P^n=\left\{\begin{array}{cc}0,& y>\frac{1}{{\mathrm{\η}}^{n-1}\mathrm{\ρ}+{\mathrm{\μ}}_0{g}_{sp}+{\mathrm{\τ}}_0}\\ y,& y\≤\frac{1}{{\mathrm{\η}}^{n-1}\mathrm{\ρ}+{\mathrm{\μ}}_0{g}_{sp}{\mathrm{\τ}}_0}\end{array}\right.,$

Wherein ρ is the power amplification factor, g _spfor secondary user's transmitting terminal is to primary user's receiving terminal channel power gain, η ^n-1for the efficiency that secondary user's (n-1)th iteration obtains;

(3.3) secondary user's according to average transmitting power constraints and average interference power constraints by subgradient iterative algorithm through k>=1 time iteration, calculate the Lagrange multiplier τ that average transmitting power constraint is corresponding ^kthe Lagrange multiplier μ corresponding with average interference power constraint ^k;

(3.4) according to the Lagrange multiplier τ calculated ^kand μ ^k, calculate transmitted power

$P_k^n=\left\{\begin{array}{cc}0,& y>\frac{1}{{\mathrm{\η}}^{n-1}\mathrm{\ρ}+{\mathrm{\μ}}^k{g}_{sp}+{\mathrm{\τ}}^k}\\ y,& y\≤\frac{1}{{\mathrm{\η}}^{n-1}\mathrm{\ρ}+{\mathrm{\μ}}^k{g}_{sp}{\mathrm{\τ}}^k}\end{array}\right.,$

(3.5) the Lagrange multiplier τ that each iterative computation goes out is judged ^kand μ ^kwhether meet stopping criterion for iteration: $\left|{\mathrm{\τ}}^k(\stackrel{\‾}{P_{th}}-E\{P_k^n\left\}\right)\right|\≤{\mathrm{\ξ}}_1,\left|{\mathrm{\μ}}^k(\stackrel{\‾}{P_{In}}-E\{g_{sp}{P}_k^n\left\}\right)\right|\≤{\mathrm{\ξ}}_2,$ If meet, then perform step (3.6), otherwise, return step (3.3);

(3.6) secondary user's calculates n-th iteration efficiency function f respectively _n(η) He the n-th iteration efficiency η ⁿ:

$f_n\left(\mathrm{\η}\right)=E\{1-{\mathrm{\χ}}_s\left(P_k^n\right)\}-{\mathrm{\η}}^{n-1}E\{{\mathrm{\ρP}}_k^n+P_C\},$

${\mathrm{\η}}^n=\frac{E\{1-{\mathrm{\χ}}_s\left(P_k^n\right)\}}{E\{{\mathrm{\ρP}}_k^n+P_C\}},$

Wherein P _cfor the consumed power of permanent circuit, calculation expression be:

(3.7) secondary user's is to efficiency function f _n(η) adjudicate: if | f _n(η) |≤ξ, the then transmitted power of n-th time for secondary user's efficiency best transmitted power P, efficiency η ⁿbe the maximum efficiency η that secondary user's obtains; Otherwise, judge whether iterations reaches maximum iteration time n≤N, if reach maximum iteration time, then transmitted power now for secondary user's efficiency best transmitted power P, efficiency η ⁿfor the maximum efficiency η that secondary user's obtains; Otherwise, continue iteration, until meet iteration ends constraints.

2. method according to claim 1, the average transmitting power constraints in wherein said step (3.3) and average interference power constraints, its formula is as follows:

Average transmitting power constraints is:

Average interference power constraints is:

Wherein, with be respectively the constraint of secondary user's maximum average transmitting power and secondary user's retrains the maximum average interference power of primary user, for kth time calculates the transmitted power after Lagrange multiplier, E{} represents asking mathematic expectaion.

3. method according to claim 1, calculates Lagrange multiplier τ corresponding to average transmitting power constraint by subgradient iterative algorithm in wherein said step (3.3) ^kthe Lagrange multiplier μ corresponding with average interference power constraint ^k, calculated by following formula:

${\mathrm{\τ}}^k={\[{\mathrm{\τ}}^{k-1}-t_1(\stackrel{\‾}{P_{th}}-E\{P_{k-1}^n\left\}\right)\]}^{+},$

${\mathrm{\μ}}^k={\[{\mathrm{\μ}}^{k-1}-t_2(\stackrel{\‾}{P_{In}}-E\{g_{sp}{P}_{k-1}^n\left\}\right)\]}^{+},$

Wherein, with be respectively the constraint of secondary user's maximum average transmitting power and secondary user's retrains the maximum average interference power of primary user, E{} represents asking mathematic expectaion, t ₁for the Lagrange multiplier iteration step length that average transmitting power constraint is corresponding, t ₂for the Lagrange multiplier iteration step length that average interference power constraint is corresponding.