CN103281143A - Selecting type cooperation spectrum sensing method based on double-threshold energy detection - Google Patents

Abstract

The invention discloses a selecting type cooperation spectrum sensing method based on double-threshold energy detection. The selecting type cooperation spectrum sensing method comprises the following steps: (1) in a master user signal detection stage, adopting a double-threshold energy detection method by various cognitive users in a cognitive radio system to carry out local spectrum sensing, if an energy value exceeds two thresholds, carrying out local judgment 'H0 or H1'by the cognitive users, and if the energy value is between the two thresholds, reserving the energy value as a primary energy detection value by the cognitive users; (2) in an initial detection result reporting stage, evenly distributing a master user frequency band by the cognitive users, adopting a selecting type strategy by the cognitive users to report initial detection results respectively to a fusion center, preventing cognitive detection results with unreliable parameters from being introduced, meanwhile, saving traditional exclusive control channel resources, adopting the equal gain criterion by the fusion center to carry out master user judgment on the received primary energy detection value, allowing the judgment result to be equivalent to a node strategy by the fusion center, and then adopting the 'or' criterion by the fusion center to make the final judgment whether a master user exists. The simulation results show that according to the selecting type cooperation spectrum sensing method based on the double-threshold energy detection, and on the premise that ROC properties are not lost, the exclusive control channel resources are effectively saved, and meanwhile higher detection efficiency can be obtained.

Description

A kind of selecting type cooperative frequency spectrum sensing method based on the double threshold energy measuring

Technical field

The invention belongs to wireless communication technology field, relate to a kind of frequency spectrum sensing method, particularly a kind of selecting type cooperative frequency spectrum sensing method based on the double threshold energy measuring.

Background technology

Along with the sustainable growth of radio communication service, wireless communication system constantly increases the demand of frequency spectrum resource, thereby makes radio spectrum resources become more and more rare.But radio spectrum resources is a kind of non-renewable resources, can only be to the frequency spectrum resource recycling, and therefore how research improves the utilance of frequency spectrum resource, could alleviate the rare difficult problem of frequency spectrum resource.Cognitive radio technology is as a kind of emerging intelligent radio communication technology, broken through the policy of traditional fixed allocation frequency spectrum, by real-time monitoring objective frequency range, main user is not being caused under the prerequisite of any interference, allow cognitive user " to wait for an opportunity " to insert the idle frequency range of temporarily not used by main user, effectively raise the availability of frequency spectrum.If in case find that main user reuses this frequency range, cognitive user should in time withdraw from this frequency range, to guarantee the normal and reliable of main telex network.

Owing to have problems such as path loss, shadow effect, multipath effect and concealed terminal in the wireless environment, the detection probability that makes traditional single node detect reduces, even can't detect main user's existence, thereby main telex network is caused interference.Therefore collaboration frequency spectrum detects as improving the technology of frequency spectrum detection and is paid close attention to widely.Document " the collaborative spectrum sensing first in the cognitive radio: two users' network " (Cooperative spectrum sensing in cognitive radio, Part I:Two user networks, G.Ganesan and Y.G.Li, IEEE Transactions on Wireless Communications, 2007,6 (6): 2204-2213) point out in traditional collaborative spectrum sensing scheme, generally all suppose to exist between cognitive user and the fusion center proprietary control channel, but this needs extra radio spectrum resources, and need carry out dynamic management to proprietary control channel resource, increase the complexity that system realizes.

Summary of the invention

At the problems referred to above, the present invention proposes a kind of selecting type cooperative frequency spectrum sensing method based on the double threshold energy measuring at cognitive radio networks, this method is avoided being difficult to determine problems such as unique decision threshold, multipath fading and shadow fading in the collaboration frequency spectrum detection, based on the double threshold energy measuring, cognitive user mean allocation master user frequency range adopts the selecting type strategy to report its initial examination and measurement result to fusion center at the time slot that is assigned to; Fusion center is at first adjudicated the primary energy detected value according to the equal gain combining criterion, is the decision-making of node with this court verdict equivalence, again by " or " criterion (points to fusion center and reports initial examination and measurement H as a result with other decision nodes ₀Or H ₁Cognitive user) make the conclusive judgement whether main user exists, improved the detection probability of system.

For achieving the above object, the present invention is based on the method for the selecting type collaborative spectrum sensing that need not proprietary control channel of double threshold energy measuring, it is characterized in that, may further comprise the steps: a kind of selecting type cooperative frequency spectrum sensing method based on the double threshold energy measuring, it is characterized in that, comprise following steps:

(1), main subscriber signal detection-phase:

(1a), each cognitive user is carried out local frequency spectrum perception to main subscriber signal, the main user's energy detection value Y that obtains perceiving in the cognitive radio system _i

(1b), judge the detected main user's energy value Y of each cognitive user _iWith two threshold value λ ₁And λ ₂Relation, as energy detection value Y _iDrop on two threshold value λ ₁And λ ₂Outside, directly carry out this locality judgement " H ₀Or H ₁", H ₀Represent that there is not H in main user ₁Represent that main user exists;

If (1c) energy detection value Y _iDrop on two threshold value λ ₁And λ ₂Between, directly do not carry out this locality judgement, cognitive user need keep primary energy detected value Y _i

(2) initial examination and measurement report stage as a result

(2a), each cognitive user mean allocation master user frequency range, cognitive user is given fusion center with separately test results report on the sub-slots that is assigned to;

(2b) adopt the selecting type strategy to report the initial examination and measurement result to fusion center, when perceiving main user at main subscriber signal detection-phase, cognitive user do not exist, then send one through the index signal of coding to fusion center, otherwise do not send any signal to avoid and main user produces interference to fusion center;

(2c), the primary energy detected value Y of fusion center to receiving _iMake main user's judgement " H ₀Or H ₁", be a node decision-making with the court verdict equivalence, the testing result of reporting to fusion center in the joint step (2b) (comprises H again ₀Or H ₁) make the conclusive judgement whether main user exists.

Further technical scheme comprises:

2 threshold value λ that vary in size are set in the step (1) ₁And λ ₂, λ ₁＜λ ₂, as energy detection value Y _i＞λ ₂The time, with testing result D _iBe judged to 1, namely there is H in main subscriber signal ₁As energy detection value Y _i＜λ ₁The time, with testing result D _iBe judged to 0, namely there is not H in main subscriber signal ₀When energy detection value is positioned at λ ₁＜Y _i＜λ ₂When interval, then keep primary energy detected value Y _iTesting result D _iBe expressed as:

$D_i=\left\{\begin{array}{cc}0,& 0<Y_i<{\mathrm{\&lambda;}}_1\\ Y_i,& {\mathrm{\&lambda;}}_1<Y_i<{\mathrm{\&lambda;}}_2\\ 1,& Y_i>{\mathrm{\&lambda;}}_2\end{array}---\left(1\right)\right.$

In step (2), cognitive user CU _iI subchannel in main user's frequency range sends signal beta to fusion center _i(k), fusion center receives signal indication accordingly and is:

$y_c^i(k,2)=\sqrt{p_s}{h}_{\mathrm{ic}}(k,2){\mathrm{\&beta;}}_i(k,2)+\sqrt{p_p}{h}_{\mathrm{pc}}\left(k\right)\mathrm{\&alpha;}(k,2)+n_c^i(k,2)---\left(2\right)$

Wherein k represents the time slot that cognitive user is assigned to, p _pThe transmitting power of representing main user, p _sThe transmitting power of expression cognitive user; h _Ic(k) and h _Pc(k) represent CU respectively _iArrive fusion center and main user to the wireless channel gain of fusion center;

(k, 2) expression zero-mean and variance are N ₀Additive white Gaussian noise;

${\mathrm{\&beta;}}_i\left(k\right)=\left\{\begin{array}{cc}{D}_i,& H_i(k,1)=H_0\\ 0,& H_i(k,1)=H_1\end{array}---\left(3\right)\right.$

$\mathrm{\&alpha;}(k,2)=\left\{\begin{array}{cc}0,& H\left(k\right)=H_0\\ s(k,2),& H\left(k\right)=H_1\end{array}---\left(4\right)\right.$

Wherein the main user of s (k, 2) expression is initial examination and measurement transmitting of report stage as a result, according to formula (2) fusion center decoding β _i(k);

According to the Shannon channel coding theorem, as cognitive user CU _iWhen produce interrupting with fusion center, fusion center can't receive signal or successfully decoding on respective sub-channel, and this moment, fusion center was thought cognitive user CU _iDo not send signal, acquiescence CU _iInitial examination and measurement H as a result _i(k, 2)=H ₁Or Y _iWhen fusion center successfully receives signal and decoding on respective sub-channel, fusion center is thought CU so _iSent signal, i.e. fusion center acquiescence CU _iInitial examination and measurement result be H _i(k, 2)=H ₀Fusion center receive from cognitive user CU _iInitial examination and measurement result be expressed as:

Wherein Θ (k, 2)=1 represents cognitive user CU _iInterrupt between the fusion center, wherein μ represents time bandwidth product, γ _sExpression cognitive user transmitting power, γ _pRepresent main user emission power; Θ (k, 2)=0 expression cognitive user CU _iDo not interrupt between the fusion center;

The generation interrupt table is shown:

$\frac{1-a}{M}{\log }_2(1+\frac{{\left|h_{\mathrm{ic}}\left(k\right)\right|}^2{\&CenterDot;\mathrm{\&gamma;}}_s{\left|{\mathrm{\&beta;}}_i\left(k\right)\right|}^2}{{\left|h_{\mathrm{pc}}\left(k\right)\right|}^2{\&CenterDot;\mathrm{\&gamma;}}_p{\left|\mathrm{\&alpha;}(k,2)\right|}^2+1})<\frac{1}{\mathrm{\&mu;}}---\left(6\right)$

Wherein a is the input overhead time, and M is cognitive user quantity.

In step 2 (c), fusion center adopts the primary energy detected value Y of equal gain combining criterion to receiving _iMake main user's judgement " H ₀Or H ₁", again by " or " testing result of reporting to fusion center in criterion and the step (2b) comprehensively makes the conclusive judgement whether main user exists.

The sensing results of conclusive judgement correspondence is expressed as:

(7) wherein

Y refers to main user's court verdict that fusion center adopts the equal gain combining criterion that the primary energy detected value that receives is made,

H _i(k, 2) handle the result who obtains for adopting the logical "or" criterion to the testing result of this locality judgement.

Beneficial effect of the present invention: the present invention adopts the collaborative spectrum sensing technology, avoided because there being problems such as path loss, shadow effect, multipath effect and concealed terminal in the wireless environment, the detection probability that makes traditional single node detect reduces, even can't detect main user's existence, thereby main telex network is caused interference.Because in traditional collaborative spectrum sensing scheme, generally all suppose to exist between cognitive user and the fusion center proprietary control channel, but this needs extra radio spectrum resources, and need carry out dynamic management to proprietary control channel resource, increased the complexity that system realizes, the present invention casts aside traditional proprietary control channel, the frequency range of not used by main user by mean allocation, each cognitive user is the data transmission scheme by selecting type on the time slot that is assigned to, the initial examination and measurement result is reported to fusion center, avoid main telex network is produced interference, effectively raise detection probability, and improved the availability of frequency spectrum.

Description of drawings

Fig. 1 is collaborative spectrum sensing system model block diagram of the present invention;

Fig. 2 is double threshold energy measuring decision diagram;

Fig. 3 is under the different detection probabilities, and the false alarm probability of traditional scheme and improvement project is performance chart relatively;

Fig. 4 is that false alarm probability is with the change curve of detection probability under the different main subscriber signal detection overhead times;

Fig. 5 is the flow chart of the selecting type cooperative frequency spectrum sensing method based on the double threshold energy measuring of the present invention.

Specific embodiments

Below in conjunction with accompanying drawing principle of the present invention and embodiment are described in further detail:

Figure 1 shows that collaborative spectrum sensing system model figure of the present invention, comprise a main user, a M cognitive user and an information fusion center in the collaborative spectrum sensing system.

A kind of selecting type cooperative frequency spectrum sensing method based on the double threshold energy measuring comprises the steps:

1, main subscriber signal detection-phase

In the phase I of time slot k, i.e. main subscriber signal detection-phase.What main subscriber signal detection-phase adopted is the double threshold energy detection method, by 2 threshold value λ that vary in size are set ₁And λ ₂(λ ₁＜λ ₂) divide reception signal energy value (Fig. 2 is double threshold energy measuring judgement block diagram), M cognitive user carried out frequency spectrum perception to main subscriber signal alone, obtains energy detection value Y _i, i=1,2 ... M.As energy detection value Y _i＞λ ₂The time, with testing result D _iBe judged to 1, namely there is H in main subscriber signal ₁, as energy detection value Y _i＜λ ₁The time, with testing result D _iBe judged to 0, namely there is not H in main subscriber signal ₀When the detected energy value drops on λ ₁＜Y _i＜λ ₂When interval, then cognitive user keeps primary energy detected value Y _i

Testing result D then _iCan be expressed as:

$D_i=\left\{\begin{array}{cc}0,& 0<Y_i<{\mathrm{\&lambda;}}_1\\ Y_i,& {\mathrm{\&lambda;}}_1<Y_i<{\mathrm{\&lambda;}}_2\\ 1,& Y_i>{\mathrm{\&lambda;}}_2\end{array}---\left(1\right)\right.$

2, initial examination and measurement report stage as a result

In the second stage of time slot k, i.e. initial examination and measurement report stage as a result.Each cognitive user CU _iMean allocation master user frequency range, each cognitive user CU _iOn the sub-slots that is assigned to, give fusion center with test results report separately.Each cognitive user CU _iAdopt the selecting type strategy to report the initial examination and measurement result to fusion center, if cognitive user CU _iDo not perceive main user at main user's detection-phase and have that (local court verdict is H ₀Cognitive user), then send one through the index signal behind the coding to fusion center; Otherwise do not send any signal avoiding and main user produces interference to fusion center, the testing result that report to fusion center this moment is defaulted as Y _iOr H ₁, this testing result is not that the transmission by index signal reports to fusion center, but by this form performance of signal interruption.

Cognitive user CU _iI subchannel in main user's frequency range sends signal beta to fusion center _i(k), fusion center receives signal accordingly and can be expressed as:

$y_c^i(k,2)=\sqrt{p_s}{h}_{\mathrm{ic}}(k,2){\mathrm{\&beta;}}_i(k,2)+\sqrt{p_p}{h}_{\mathrm{pc}}\left(k\right)\mathrm{\&alpha;}(k,2)+n_c^i(k,2)---\left(2\right)$

P wherein _pThe transmitting power of representing main user, p _sThe transmitting power of expression cognitive user; h _Ic(k) and h _Pc(k) represent CU respectively _iArrive fusion center and main user to the wireless channel gain of fusion center;

(k, 2) expression zero-mean and variance are N ₀Additive white Gaussian noise.

${\mathrm{\&beta;}}_i\left(k\right)=\left\{\begin{array}{cc}{D}_i,& H_i(k,1)=H_0\\ 0,& H_i(k,1)=H_1\end{array}\right.---\left(3\right)$

$\mathrm{\&alpha;}(k,2)=\left\{\begin{array}{cc}0,& H\left(k\right)=H_0\\ s(k,2),& H\left(k\right)=H_1\end{array}---\left(4\right)\right.$

Wherein the main user of s (k, 2) expression is the transmitting of time slot k second stage, according to formula (2) fusion center decoding β _i(k).

According to the Shannon channel coding theorem, if channel capacity is lower than the rate of information throughput, adopt which kind of decoder all can not correctly recover primary signal, and be called and interrupt.As cognitive user CU _iWhen produce interrupting with fusion center, fusion center can't receive signal or successfully decoding on respective sub-channel, and this moment, fusion center was thought cognitive user CU _iDo not send signal, acquiescence CU _iInitial examination and measurement H as a result _i(k, 2)=H ₁Or Y _i, namely the initial examination and measurement result of cognitive user is that main user exists or detected value is the primary energy value.If fusion center successfully receives signal and decoding on respective sub-channel, fusion center is then thought CU so _iSent signal, i.e. fusion center acquiescence CU _iInitial examination and measurement result be H _i(k, 2)=H ₀Therefore, fusion center receives from cognitive user CU _iInitial examination and measurement result can be expressed as:

Wherein Θ (k, 2)=1 represents cognitive user CU _iInterrupt between the fusion center, wherein μ represents time bandwidth product, γ _sExpression cognitive user transmitting power and γ _pRepresent main user emission power; Θ (k, 2)=0 expression cognitive user CU _iDo not interrupt between the fusion center.The generation interrupt table is shown:

$\frac{1-a}{M}{\log }_2(1+\frac{{\left|h_{\mathrm{ic}}\left(k\right)\right|}^2{\&CenterDot;\mathrm{\&gamma;}}_s{\left|{\mathrm{\&beta;}}_i\left(k\right)\right|}^2}{{\left|h_{\mathrm{pc}}\left(k\right)\right|}^2{\&CenterDot;\mathrm{\&gamma;}}_p{\left|\mathrm{\&alpha;}(k,2)\right|}^2+1})<\frac{1}{\mathrm{\&mu;}}---\left(6\right)$

Wherein a is the input overhead time, and M is cognitive user quantity.

Fusion center is at first with the primary energy detected value Y that keeps in the step (1) and received by fusion center _iWait gain (EGC) to merge and merge, make main user " H ₀Or H ₁" judgement, be the decision-making of node with this court verdict equivalence, again according to " or " (at the cognitive user of transmission index signal, testing result is H to criterion with other decision nodes ₀At not sending index signal and not keeping the cognitive user of primary energy detected value Yi, testing result is H ₁) make final sensing results, namely make the conclusive judgement whether main user exists.

Consider the logical "or" criterion, sensing results can be expressed as: (7)

Under rayleigh fading channel, initial examination and measurement probability, false alarm probability, the false dismissal probability of cognitive user is expressed as follows respectively in the cognitive radio system:

${\mathrm{Pd}}_i\left(\mathrm{\&mu;}\right)=P\{Y_i>{\mathrm{\&lambda;}}_2|H_1\}$

$={\&Integral;}_x{Q}_{\mathrm{\&mu;}}(\sqrt{2\stackrel{\&OverBar;}{\mathrm{\&gamma;}}},\sqrt{{\mathrm{\&lambda;}}_2})\&CenterDot;f_{\mathrm{\&gamma;}}\left(x\right)\mathrm{dx}---\left(8\right)$

$=e^{-\frac{{\mathrm{\&lambda;}}_2}{2}}\underset{n=0}{\overset{\mathrm{\&mu;}-2}{\mathrm{\&Sigma;}}}\frac{1}{n!}{\left(\frac{{\mathrm{\&lambda;}}_2}{2}\right)}^n+{\left(\frac{1+\stackrel{\&OverBar;}{\mathrm{\&gamma;}}}{\stackrel{\&OverBar;}{\mathrm{\&gamma;}}}\right)}^{\mathrm{\&mu;}-1}\left[e^{-\frac{{\mathrm{\&lambda;}}_2}{2(1+\stackrel{\&OverBar;}{\mathrm{\&gamma;}})}}\right]-e^{-\frac{{\mathrm{\&lambda;}}_2}{2}}\underset{n=0}{\overset{\mathrm{\&mu;}-2}{\mathrm{\&Sigma;}}}\frac{1}{n!}{\left(\frac{{\mathrm{\&lambda;}}_2\stackrel{\&OverBar;}{\mathrm{\&gamma;}}}{2(1+\stackrel{\&OverBar;}{\mathrm{\&gamma;}})}\right)}^n]$

${\mathrm{Pm}}_i=1-{\mathrm{\&Delta;}}_{1,j}-{\mathrm{Pd}}_i---\left(9\right)$

${\mathrm{Pf}}_i=P\{Y_i>{\mathrm{\&lambda;}}_2|H_o\}=\frac{\mathrm{\&Gamma;}(\mathrm{\&mu;},\frac{{\mathrm{\&lambda;}}_2}{2})}{\mathrm{\&Gamma;}\left(\mathrm{\&mu;}\right)}---\left(10\right)$

Q wherein _uExpression broad sense horse khoum (Marcum) function; Γ (μ) and Γ (μ, λ ₂/ 2) the imperfect Gamma function of expression complete sum;

The expression average signal-to-noise ratio, f _γ(x) probability-distribution function of signal to noise ratio under the expression decline situation.

According to formula (6), (7), (8), can draw when adopting the logical "or" criterion, the detection probability of collaborative spectrum sensing when fusion center that need not proprietary control channel is:

${\mathrm{Pd}}_{\mathrm{or}}^{\mathrm{proposed}}=1-\underset{K=0}{\overset{M-1}{\mathrm{\&Sigma;}}}\left(\begin{array}{c}M\\ K\end{array}\right)\underset{i=1}{\overset{K}{\mathrm{\&Pi;}}}\mathrm{Pm}\&CenterDot;\underset{j=1}{\overset{M-K}{\mathrm{\&Pi;}}}{\mathrm{\&Delta;}}_{1,j}\&CenterDot;\{1-{\mathrm{Pd}}_j[(M-K)\&CenterDot;\mathrm{\&mu;}\left]\right\}-\underset{i=1}{\overset{M}{\mathrm{\&Pi;}}}\mathrm{Pm}$

（11）

In the formula

Detection limit Y when it represents that main user exists _iDrop on threshold value λ ₁And λ ₂Between probability.

With

Represent that respectively cognitive user CUi is to the wireless channel gain h of fusion center _IcThe average of (k) obeying and main user are to the wireless channel gain h of fusion center _PcThe average of (k) obeying.

According to formula (6), (7), (10), can draw when adopting the logical "or" criterion, the false alarm probability of collaborative spectrum sensing when fusion center that need not proprietary control channel is:

${\mathrm{Pf}}_{\mathrm{or}}^{\mathrm{proposed}}=1-\underset{K=0}{\overset{M-1}{\mathrm{\&Sigma;}}}\left(\begin{array}{c}M\\ K\end{array}\right)\underset{i=1}{\overset{K}{\mathrm{\&Pi;}}}\mathrm{Pn}\&CenterDot;\underset{j=1}{\overset{M-K}{\mathrm{\&Pi;}}}{\mathrm{\&Delta;}}_{0,j}\&CenterDot;\{1-\frac{\mathrm{\&Gamma;}\left\{\right[(M-K)\&CenterDot;\mathrm{\&mu;}],\frac{\mathrm{\&lambda;}}{2}\}}{\mathrm{\&Gamma;}[(M-K)\&CenterDot;\mathrm{\&mu;}]}\}-\underset{i=1}{\overset{M}{\mathrm{\&Pi;}}}\mathrm{Pn}$

（13）

In the formula

Δ _{0, j}=P{ λ ₁＜Y _i＜λ ₂| H ₀Detection limit Y when the main user of expression does not exist _iDrop on threshold value λ ₁And λ ₂Between probability.

The false alarm probability comparison based on the false alarm probability of the method for the selecting type collaborative spectrum sensing that need not proprietary control channel of double threshold energy measuring and traditional double threshold energy measuring method that the present invention proposes can be consulted Fig. 3.As can be seen from Figure 3, the false alarm probability of the collaborative spectrum sensing scheme that proposes in low detection probability zone is obviously greater than traditional collaborative spectrum sensing scheme, this is because unaffected in order to guarantee main telex network service quality, makes the initial examination and measurement probability P d of cognitive user _iMust satisfy certain threshold value condition (as the formula (15));

${\mathrm{Pd}}_i\&GreaterEqual;1-\frac{{\mathrm{\&gamma;}}_p\&CenterDot;{\mathrm{\&sigma;}}_{\mathrm{pd}}^2\&CenterDot;M[1-{(1-\mathrm{Pout})}^{1/M}]}{{\mathrm{\&gamma;}}_s\&CenterDot;{\mathrm{\&sigma;}}_{\mathrm{id}}^2\&CenterDot;{(1-\mathrm{Pout})}^{1/M}\&CenterDot;(2^{R_p}-1)}---\left(15\right)$

Pout represents given main telex network outage probability thresholding, R _pRepresent main user data transmission speed.

In the high detection probability region, almost the collaborative spectrum sensing scheme with traditional is the same for the false alarm probability of the collaborative spectrum sensing scheme that proposes, in the actual cognitive radio system, for example the detection probability of IEEE radio area network standard code frequency spectrum perception must be greater than 0.9, under the prerequisite of not losing the ROC performance, saved proprietary reporting channel resource from this angle scheme in this paper effectively.

Fig. 4 provided under the different main subscriber signal detection overhead times, and false alarm probability is with the change curve of detection probability.By reasonably increasing the detection time of main subscriber signal, can effectively improve the initial examination and measurement performance of cognitive user as can be seen from Figure 4, the present invention program's false alarm probability also descends thereupon.

The contribution of method of the present invention is in sum:

1, adopts the collaborative spectrum sensing technology, avoid because there being problems such as path loss, shadow effect, multipath effect and concealed terminal in the wireless environment, the detection probability that makes traditional single node detect reduces, even can't detect main user's existence, thereby main telex network is caused interference.

2, adopt the selecting type strategy to report the testing result technology, avoided the insecure transfer of data of some testing results to fusion center, reduced the complexity that the fusion center data are handled, avoided the interference to main telex network simultaneously.

3, adopt the proprietary control channel technology that need not, minimizing is because existing proprietary control channel between hypothesis cognitive user and the fusion center in traditional collaborative spectrum sensing scheme, reduced extra radio spectrum resources, avoided proprietary control channel resource is carried out dynamic management, reduced the complexity that system realizes.

4, adopt the double threshold energy detection technique, avoided existing in the collaboration frequency spectrum detection being difficult to determine problems such as unique decision threshold, multipath fading and shadow fading.

Above-described embodiment does not limit the present invention in any form, and all employings are equal to replaces or technical scheme that the mode of equivalent transformation obtains, all drops on protection scope of the present invention.

Claims (5)

1. the selecting type cooperative frequency spectrum sensing method based on the double threshold energy measuring is characterized in that, comprises following steps:

(1), main subscriber signal detection-phase:

(1a), each cognitive user is carried out local frequency spectrum perception to main subscriber signal, the main user's energy detection value Y that obtains perceiving in the cognitive radio system _i

(1b), judge the detected main user's energy value Y of each cognitive user _iWith two threshold value λ ₁And λ ₂Relation, as energy detection value Y _iDrop on two threshold value λ ₁And λ ₂Outside, directly carry out this locality judgement " H ₀Or H ₁", H ₀Represent that there is not H in main user ₁Represent that main user exists;

If (1c) energy detection value Y _iDrop on two threshold value λ ₁And λ ₂Between, directly do not carry out this locality judgement, cognitive user need keep primary energy detected value Y _i

(2) initial examination and measurement report stage as a result

(2a), each cognitive user mean allocation master user frequency range, cognitive user is given fusion center with separately test results report on the sub-slots that is assigned to;

(2b) adopt the selecting type strategy to report the initial examination and measurement result to fusion center, do not exist when cognitive user perceives main user at main subscriber signal detection-phase, then send one through the index signal of coding to fusion center; Otherwise do not send any signal avoiding and main user produces interference to fusion center, testing result is defaulted as Y _iOr H ₁;

(2c), the primary energy detected value Y of fusion center to receiving _iMake main user's judgement " H ₀Or H ₁", be a node decision-making with the court verdict equivalence, the testing result of reporting to fusion center in the joint step (2b) is made the conclusive judgement whether main user exists again.

2. a kind of selecting type cooperative frequency spectrum sensing method based on the double threshold energy measuring according to claim 1 is characterized in that, 2 threshold value λ that vary in size are set in the step (1) ₁And λ ₂, λ ₁＜λ ₂, as energy detection value Y _i＞λ ₂The time, with testing result D _iBe judged to 1, namely there is H in main subscriber signal ₁As energy detection value Y _i＜λ ₁The time, with testing result D _iBe judged to 0, namely there is not H in main subscriber signal ₀When energy detection value is positioned at λ ₁＜Y _i＜λ ₂When interval, then keep primary energy detected value Y _i

Testing result D _iBe expressed as:

$D_i=\left\{\begin{array}{cc}0,& 0<Y_i<{\mathrm{\&lambda;}}_1\\ Y_i,& {\mathrm{\&lambda;}}_1<Y_i<{\mathrm{\&lambda;}}_2\\ 1,& Y_i>{\mathrm{\&lambda;}}_2\end{array}\right.---\left(1\right)$

3. a kind of selecting type cooperative frequency spectrum sensing method based on the double threshold energy measuring according to claim 1 is characterized in that, in step (2),

Cognitive user CU _iI subchannel in main user's frequency range sends signal beta to fusion center _i(k), fusion center receives signal indication accordingly and is:

$y_c^i(k,2)=\sqrt{p_s}{h}_{\mathrm{ic}}(k,2){\mathrm{\&beta;}}_i(k,2)+\sqrt{p_p}{h}_{\mathrm{pc}}\left(k\right)\mathrm{\&alpha;}(k,2)+n_c^i(k,2)---\left(2\right)$

Wherein k represents the time slot that cognitive user is assigned to, p _pThe transmitting power of representing main user, p _sThe transmitting power of expression cognitive user; h _Ic(k) and h _Pc(k) represent CU respectively _iArrive fusion center and main user to the wireless channel gain of fusion center;

(k, 2) expression zero-mean and variance are N ₀Additive white Gaussian noise;

${\mathrm{\&beta;}}_i\left(k\right)=\left\{\begin{array}{cc}{D}_i,& H_i(k,1)=H_0\\ 0,& H_i(k,1)=H_1\end{array}\right.---\left(3\right)$

$\mathrm{\&alpha;}(k,2)=\left\{\begin{array}{cc}0,& H\left(k\right)=H_0\\ s(k,2),& H\left(k\right)=H_1\end{array}\right.---\left(4\right)$

Wherein the main user of s (k, 2) expression is initial examination and measurement transmitting of report stage as a result, according to formula (2) fusion center decoding β _i(k);

According to the Shannon channel coding theorem, as cognitive user CU _iWhen produce interrupting with fusion center, fusion center can't receive signal or successfully decoding on respective sub-channel, and this moment, fusion center was thought cognitive user CU _iDo not send signal, acquiescence CU _iInitial examination and measurement H as a result _i(k, 2)=H ₁Or Y _iWhen fusion center successfully receives signal and decoding on respective sub-channel, fusion center is thought CU so _iSent signal, i.e. fusion center acquiescence CU _iInitial examination and measurement result be H _i(k, 2)=H ₀Fusion center receive from cognitive user CU _iInitial examination and measurement result be expressed as:

Wherein Θ (k, 2)=1 represents cognitive user CU _iInterrupt between the fusion center, wherein μ represents time bandwidth product, γ _sExpression cognitive user transmitting power, γ _pRepresent main user emission power; Θ (k, 2)=0 expression cognitive user CU _iDo not interrupt between the fusion center;

The generation interrupt table is shown:

$\frac{1-a}{M}{\log }_2(1+\frac{{\left|h_{\mathrm{ic}}\left(k\right)\right|}^2{\&CenterDot;\mathrm{\&gamma;}}_s{\left|{\mathrm{\&beta;}}_i\left(k\right)\right|}^2}{{\left|h_{\mathrm{pc}}\left(k\right)\right|}^2{\&CenterDot;\mathrm{\&gamma;}}_p{\left|\mathrm{\&alpha;}(k,2)\right|}^2+1})<\frac{1}{\mathrm{\&mu;}}---\left(6\right)$

Wherein a is the input overhead time, and M is cognitive user quantity.

4. a kind of selecting type cooperative frequency spectrum sensing method based on the double threshold energy measuring according to claim 1 is characterized in that, in step 2 (c), fusion center adopts the primary energy detected value Y of equal gain combining criterion to receiving _iMake main user's judgement " H ₀Or H ₁", again by " or " testing result of reporting to fusion center in criterion and the step (2b) comprehensively makes the conclusive judgement whether main user exists.

5. according to claim 3 or 4 any described a kind of selecting type cooperative frequency spectrum sensing methods based on the double threshold energy measuring, it is characterized in that the sensing results of conclusive judgement correspondence is expressed as:

$H_c\left(k\right)=\&CirclePlus;Y\underset{i=1}{\overset{K}{\&CirclePlus;}}{H}_i(k,2)---\left(7\right)$

Wherein

Y refers to main user's court verdict that fusion center adopts the equal gain combining criterion that the primary energy detected value that receives is made,

H _i(k, 2) handle the result who obtains for adopting the logical "or" criterion to the testing result of this locality judgement.

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