CN109150339A - Frequency spectrum sensing method and system based on the weak channel signal envelope of Rayleigh - Google Patents
Frequency spectrum sensing method and system based on the weak channel signal envelope of Rayleigh Download PDFInfo
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Abstract
The present invention relates to signal processing technology fields, a kind of frequency spectrum sensing method and system based on the weak channel signal envelope of Rayleigh are disclosed, to further increase detection performance.The method of the present invention includes: to intercept signal sampling value for isometric array by carrier cycle integral multiple, calculates the correlation properties in adjacent periods, constructs approximated correlation matrix, and matrix element is the sampling period signal autocorrelation amount of adjacent spaces；Then statistic is constructed according to approximated correlation matrix time diagonal element property, and judges that authorized user's frequency spectrum is in silent status or working condition according to statistic result.In the present invention, the statistic increases the centre distance of detection probability distribution function and false-alarm probability distribution function and improves the convergence rate of detection probability distribution function, detection performance is greatly optimized, realize unrelated with noise and has lesser dependence to signal correlation.
Description
Technical Field
The invention relates to the technical field of signal processing, in particular to a frequency spectrum sensing method and system based on Rayleigh fading channel signal envelope.
Background
With the development of wireless communication technology, the access amount of wireless devices is increasing, and the available spectrum resources are extremely scarce. However, the usage rate of some licensed bands (tv bands) is low, which results in a great waste of spectrum, and meanwhile, a large amount of newly developed communication devices can only be crowded in an unlicensed band (ISM) due to the availability of unlicensed bands, which seriously hinders the development of wireless communication technology. The cognitive radio technology realizes flexible management of frequency spectrum resources by opportunistic access of idle frequency spectrum, and has great significance for development of future radio communication technology.
Spectrum sensing is one of the key technologies of cognitive radio, and whether available wireless spectrum exists can be judged only through the sensing technology. The traditional three sensing technologies: matched filter detection, energy detection and cyclostationary detection are first proposed. Through years of research, the method plays an important role in promoting the development of cognitive radio technologies, but the technologies are limited in specific use, so that the detection performance is poor. The matched filtering detection has higher tolerance to prior information of an authorized user, and the actual meaning of the detection technology is not great if no authorized user is matched; energy detection is particularly suitable for sensing a user to perform spectrum sensing as a blind sensing algorithm, but the use of the detection technology firstly estimates the power of superimposed noise, and the energy detection cannot be realized due to a noise wall generated by the instability of the noise power, and the detection performance of a signal with low signal-to-noise ratio is sharply reduced. To overcome these deficiencies, some improved algorithms based on energy detection are also continuously proposed; the cyclostationary detection is provided based on the periodic characteristic of the authorized user signal, the receiving end signal must satisfy the cyclostationary in the broad sense, and the signal and the noise are required to be strictly uncorrelated, and the defects of large data computation amount, long perception time and the like are caused by the need of calculating the cyclostationary spectral density of the receiving signal. In order to overcome the defects of the traditional detection technology, signal period map related detection, eigenvalue detection, covariance matrix detection and the like are successively provided, however, new problems occur, the signal period map related detection solves the problems occurring when the signal-to-noise ratio is low, but partial prior information of signals is needed, and the covariance matrix detection needs stronger correlation of sampled signals.
Disclosure of Invention
The invention aims to disclose a frequency spectrum sensing method and a frequency spectrum sensing system based on Rayleigh fading channel signal envelope so as to further improve the detection performance.
In order to achieve the above object, the present invention discloses a spectrum sensing method based on rayleigh fading channel signal envelope, comprising:
step S1, obtaining the transmitting-end modulation signal propagated through the rayleigh fading channel, to obtain:
wherein, L is the number of propagation paths; cnThe nth propagation path amplitude;is the instantaneous phase of the received signal at time t; tau isnDelay time for the nth propagation path; w (t) is additive noise at the receiving end,complex envelope for the transmit baseband signal; f. ofcModulating a carrier frequency; re [. C]Representing a real part;
step S2, based on y (t), a time-varying nonlinear signal with Rayleigh complex envelope is obtained, the envelope waveform is a (t), comprisingLet the sampling period be Ts＝1/(Nfc) That is, if the number of samples collected in one carrier period is N, then t is nTsThe sampling signal at the moment is:
ignore TsAnd constructing a vector:
intercepting the signal sampling value into an array with equal length according to integral multiple of carrier period, calculating the correlation characteristic in adjacent periods, and constructing an approximate correlation matrix as follows:
wherein K is an odd number of 3 or more, i is 0 or more and K is j or less,
and step S3, constructing statistic according to the sub-diagonal element property of the approximate correlation matrix, and judging whether the frequency spectrum of the authorized user is in a silent state or a working state according to the statistic result.
In order to achieve the above object, the present invention also discloses a spectrum sensing system based on rayleigh fading channel signal envelope, comprising:
the first processing module is used for acquiring the transmitting end modulation signal after being propagated through the rayleigh fading channel, and obtaining:
wherein, L is the number of propagation paths; cnThe nth propagation path amplitude;is the instantaneous phase of the received signal at time t; tau isnDelay time for the nth propagation path; w (t) is additive noise at the receiving end,complex envelope for the transmit baseband signal; f. ofcModulating a carrier frequency; re [. C]Representing a real part;
a second processing module for making the envelope waveform a (t) based on y (t) being a time-varying nonlinear signal with Rayleigh complex envelope, havingLet the sampling period be Ts＝1/(Nfc) That is, if the number of samples collected in one carrier period is N, then t is nTsThe sampling signal at the moment is:
ignore TsAnd constructing a vector:
intercepting the signal sampling value into an array with equal length according to integral multiple of carrier period, calculating the correlation characteristic in adjacent periods, and constructing an approximate correlation matrix as follows:
wherein K is an odd number of 3 or more, i is 0 or more and K is j or less,
and the third processing module is used for constructing statistic according to the property of the sub-diagonal elements of the approximate correlation matrix and judging that the frequency spectrum of the authorized user is in a silent state or a working state according to the statistic result.
Based on the method and system of the present invention, optionally, the constructing statistics according to the secondary diagonal element properties of the approximate correlation matrix, and determining that the spectrum of the authorized user is in the silent state or the working state according to the statistics result specifically includes:
step S31, the spectrum sensing can be equivalent to the following binary assumption problem, including:
wherein H0 denotes the silence of the authorized user; h1 denotes authorized user work;
when the authorized user is silent,obtaining: the matrix when H0 is assumed to be true is:
when the user is authorized to work with the device,wherein rho is not less than 0ij1 is less than or equal to 1 in the ith 1/fcTime period and jth 1/fcCorrelation coefficient of envelope magnitude in time period, and pij＝ρji(ii) a Obtaining: the matrix when H1 is assumed to be true is:
step S32, the frequency change based on the envelope is very weak relative to the carrier frequency, the envelopes of the sending end signal after channel attenuation in the adjacent carrier period have the same correlation coefficient, and the rho is led to beijρ, where | i-j | ═ 1;
step S33, transforming the above-mentioned silence and true approximate correlation matrix in working state to obtain matrix M respectively:
and
wherein,
step S34, taking the sub diagonal element M of the matrix MijAnalysis was performed to construct a statistic T:
obtaining: if T>1, authorizing the user to be in a working state; if T is 1, the authorized user is in a silent state.
Optionally, the method and system further include: and setting the false alarm probability of the statistic, and calculating a detection threshold value and a detection probability according to the false alarm probability.
By adopting the technical scheme of the invention, the correlation requirement on the sampling signal is changed to the requirement on the correlation of the signal envelope, and the signal envelope has lower frequency spectrum and stronger correlation on the same sampling signal. In order to improve the detection performance, carrier information of a signal is utilized, a signal sampling value is intercepted into an array with equal length according to integral multiple of a carrier (central frequency spectrum) period, and an approximate correlation matrix based on signal envelope is constructed by only calculating correlation characteristics in adjacent periods. Compared with the traditional correlation matrix, the approximate correlation matrix detection increases the center distance (the expected distance is increased) of the detection probability distribution function and the false alarm probability distribution function and improves the convergence speed (the variance is reduced) of the detection probability distribution function and the false alarm probability distribution function, so that the detection performance of the approximate correlation matrix detection is better for the same false alarm probability, and the detection threshold is only related to the intercepted array quantity and is not related to the system noise. Compared with energy detection, the method has no relation with noise power, so that the problem of incapability of detection due to uncertainty of noise does not occur. Compared with the traditional correlation detection, the method has the advantages that the requirement of signal correlation is lowered, the same false alarm probability constraint is realized, the calculation of the detection threshold is simplified, and the detection performance is greatly improved.
Detailed Description
The present invention will be described in further detail below in order to enable those skilled in the art to better understand the technical solution of the present invention.
Example 1
The embodiment discloses a spectrum sensing method based on Rayleigh fading channel signal envelope.
The method is provided with a transmitting end modulation signal:
wherein,complex envelope for the transmit baseband signal; f. ofcModulating a carrier frequency; re [. C]The representation takes the real part.
After propagation through the rayleigh fading channel, at the receiving end:
wherein, L is the number of propagation paths; cnThe nth propagation path amplitude;for the instantaneous phase of the received signal at time t；τnDelay time for the nth propagation path; w (t) is the additive noise at the receiving end.
It is easy to know that y (t) is a time-varying nonlinear signal with complex envelope being rayleigh distribution, and let the envelope waveform be a (t) as follows:
wherein a (t) obeys Rayleigh distribution, and the envelope average power is 2 deltaa 2The corresponding probability density function is:
the uniform distribution is satisfied, and the corresponding probability density function is:
and a (t) andare independent of each other.
Thus, spectrum sensing can be equivalent to the following binary assumption problem:
h0 denotes the silence of the authorized user; h1 denotes an authorized user working.
Let the sampling period be Ts＝1/(Nfc) That is, if the number of samples collected in one carrier period is N, then t is nTsThe sampling signal at the moment is:
ignore TsLet us order
Defining K as an odd number greater than or equal to 3, and constructing an approximate correlation matrix as:
where 0 ≦ i, j ≦ K, E is the expectation in statistics. In the matrix shown in formula (9), the distribution characteristics are: the diagonal line is the autocorrelation quantity of the sampling signal; the elements in the same row are consistent from the diagonal line to the left and are all related quantity of the sampling period corresponding to the elements in the diagonal line and the previous period; and taking the diagonal line to the right and the elements in the same row are not consistent, starting with the sampling period corresponding to the elements in the diagonal line, solving the signal correlation quantity of two adjacent sampling periods one by one according to the sampling sequence, and sequentially arranging the obtained results on the right side of the diagonal line elements corresponding to the row in the approximate correlation matrix.
1. When the authorized user is silent:
for noise power, there is a matrix when H0 is assumed to be true:
2. when the authorized user is working:
wherein rho is not less than 0ij1 is less than or equal to 1 in the ith 1/fcTime period and jth 1/fcNumber of correlations of the envelope amplitudes within the time period, and pij＝ρji. The matrix with the assumption that H1 is true is:
further observation shows that both matrices are symmetric matrices, and the main diagonal elements of the matrices satisfy formula (15):
then one can define M (M) of K if H0 is trueij) The matrix is:
for the case that H1 is true, further analysis shows that the frequency variation of the envelope varies very weakly with respect to the carrier frequency, so that the envelopes of the transmitting-end signal after channel attenuation in adjacent carrier periods can be considered to have the same correlation coefficient, and ρ can be made to beijρ (where | i-j | ═ 1). Obtaining:
wherein,
and (3) taking the sub diagonal elements of the matrix M for analysis, and constructing a statistic T:
since K is an odd number, ideally: if T is greater than 1, the authorized user is in a working state; if T is 1, the authorized user is in a silent state.
As is apparent from the theorem of majorities, the statistic T follows a normal distribution. The performance analysis for statistic T is as follows:
1. when the authorized user is in the silent state, there are:
a1, mean value:
b1, variance:
2. when the authorized user is in the working state, the statistic T is as follows:
a2, mean value:
b2, variance:
then under two assumptions, the probability density function for the statistic T is:
in practical situation, because the number of sampling points is not infinite, the noise signal is not completely white noise, and the detection threshold value is η, the detection probability P of the statistic T is provided according to the Bayesian criterionD|TAnd false alarm probability PFA|TComprises the following steps:
wherein:
in spectrum sensing, a false alarm probability P needs to be assumedFA|TUnder the constraint of α, making the detection probability PD|TAnd max. According to the Neyman-Pearson criterion, the detection threshold values can be obtained as follows:
η＝2ε0 2Q-1(α)+μ0(25)
there is therefore a probability of detection:
in summary, the spectrum sensing method based on the rayleigh fading channel signal envelope in the embodiment of the present invention can be further summarized as the following steps:
(1) determining N, K and false alarm probability α;
(2) constructing a vector Y (i) from the sampled values y (n);
(3) calculating r from equation (10)ijTo construct a matrix
(4) To matrixAll elements are divided by the value of the main diagonal element to construct the matrix M (M)ij)；
(5) And a structural statistic T, and calculating μ from equations (19) to (20)0,ε0 2,μ1,ε1 2Obtaining a probability density function (21) of the statistic T1;
(6) calculating a detection threshold η from equation (25);
(7) calculating a detection probability P from the formula (26)D|T。
In this embodiment, further, to verify the performance of the statistics, the spectrum sensing algorithm of the envelope matrix is simulated under different parameter conditions.
Simulating one, setting correlation coefficient rho of received signal enveloped in adjacent carrier wave period as 0.9, false alarm probability PFA|TThe detection probability obtained under different limiting conditions is known from simulation results, the envelope noise power has larger influence than the detection probability, and the signal-to-noise ratio is greatly improvedThe detection performance is improved. If the false alarm probability is limited to PFA|T0.1, when γ is 0.01(-40dB), PD|TWhen the value is 0.3, the detection performance is obviously extremely low; when γ is 0.2(-14dB), PD|TAnd (0.96) to completely meet the requirement of detection performance. If the algorithm only analyzes the envelope power of the sampling signal theoretically, the envelope noise power ratio is likely to be further improved and the performance is also greatly improved due to the fact that the sampling signal contains the carrier power in actual use.
And simulating two, and assuming that gamma is 0.1(-20dB), wherein the influence of the correlation coefficient of the sampling signal on the detection performance is influenced. According to the simulation result, the following results are obtained: the stronger signal correlation performance greatly improves the detection performance, and therefore, the signal correlation can be improved by increasing the sampling frequency, but the requirement of sampling equipment is increased and the calculation amount is increased.
Simulation three, limit PFA|TAnd when the envelope noise power ratio is 0.1, the envelope noise power ratio corresponds to the detection probability. According to the simulation result, the following results are obtained: when the signal envelope noise power is lower, the influence of the correlation coefficient on the detection performance is limited, and with the increase of the signal envelope noise power ratio, the signal with the larger correlation coefficient (more dense sampling) can quickly improve the detection performance, but when rho is lower>At 0.9, the improvement of the detection performance is not remarkable, and therefore it is not preferable to improve the detection performance by increasing the sampling rate without limitation.
It should be noted that, in this embodiment, the process of proving the formula (13) is as follows:
because a (t) andare independent of each other, andsatisfy [ -pi, pi [ -pi [ ]]Evenly distributed, having:
then there are:
when i is not equal to j, the envelope spectrum of the received signal is lower, and the correlation is larger (rho is more than or equal to 0)ij1) and additive white noise is uncorrelated, thus:
when i ═ j, the received signal envelope follows the following exponential distribution with a probability density of:
then there are:
and the following steps:
namely, the method comprises the following steps:
in summary, the spectrum sensing method based on rayleigh fading channel signal envelope disclosed in this embodiment switches the correlation requirement for the sampled signal to the requirement for the signal envelope correlation, and because the signal envelope has a lower spectrum, there is a stronger correlation for the same sampled signal. In order to improve the detection performance, carrier information of a signal is utilized, a signal sampling value is intercepted into an array with equal length according to integral multiple of a carrier (central frequency spectrum) period, and an approximate correlation matrix based on signal envelope is constructed by only calculating correlation characteristics in adjacent periods. Compared with the traditional correlation matrix, the approximate correlation matrix detection increases the center distance (expected distance is increased) between the detection probability distribution function and the false alarm probability distribution function and improves the convergence speed (variance is reduced) of the detection probability distribution function and the false alarm probability distribution function, so that the detection performance of the approximate correlation matrix detection is better for the same false alarm probability, and the detection threshold is only related to the intercepted array quantity and is not related to the system noise. Compared with energy detection, the method has no relation with noise power, so that the problem that the detection cannot be carried out due to uncertainty of noise does not occur. Compared with the traditional correlation detection, the method has the advantages that the requirement of signal correlation is lowered, the same false alarm probability constraint is realized, the calculation of the detection threshold is simplified, and the detection performance is greatly improved.
Example 2
Corresponding to the above method embodiments, this embodiment discloses a spectrum sensing system based on rayleigh fading channel signal envelope, including:
the first processing module is used for acquiring the transmitting end modulation signal after being propagated through the rayleigh fading channel, and obtaining:
wherein, L is the number of propagation paths; cnThe nth propagation path amplitude;is the instantaneous phase of the received signal at time t; tau isnDelay time for the nth propagation path; w (t) is additive noise at the receiving end,complex envelope for the transmit baseband signal; f. ofcModulating a carrier frequency; re [. C]Representing a real part;
a second processing module for making the envelope waveform a (t) based on y (t) being a time-varying nonlinear signal with Rayleigh complex envelope, havingLet the sampling period be Ts＝1/(Nfc) That is, if the number of samples collected in one carrier period is N, then t is nTsThe sampling signal at the moment is:
ignore TsAnd constructing a vector:
intercepting the signal sampling value into an array with equal length according to integral multiple of carrier period, calculating the correlation characteristic in adjacent periods, and constructing an approximate correlation matrix as follows:
wherein K is an odd number of 3 or more, i is 0 or more and K is j or less,
and the third processing module is used for constructing statistic according to the property of the sub-diagonal elements of the approximate correlation matrix and judging that the frequency spectrum of the authorized user is in a silent state or a working state according to the statistic result.
Optionally, the third processing module further includes:
the first submodule is used for equating the spectrum sensing as a binary hypothesis problem which comprises the following steps:
wherein H0 denotes the silence of the authorized user; h1 denotes authorized user work;
when the authorized user is silent,obtaining: the matrix when H0 is assumed to be true is:
when the user is authorized to work with the device,wherein rho is not less than 0ij1 is less than or equal to 1 in the ith 1/fcTime period and jth 1/fcCorrelation coefficient of envelope magnitude in time period, and pij＝ρji(ii) a Obtaining: the matrix when H1 is assumed to be true is:
and the second submodule is used for enabling the envelope of the signal at the transmitting end after channel attenuation in adjacent carrier periods to have the same correlation coefficient based on the extremely weak change of the frequency change of the envelope relative to the carrier frequency to enable rhoijρ, where | i-j | ═ 1;
and a third submodule for transforming the said silence and true approximate correlation matrix under working state to obtain matrix M:
and
wherein,
submodule four for taking sub diagonal element M of matrix MijAnalysis was performed to construct a statistic T:
obtaining: if T>1, authorizing the user to be in a working state; if T is 1, the authorized user is in a silent state.
Optionally, the system of this embodiment further includes:
and the fourth processing module is used for setting the false alarm probability of the statistic and calculating a detection threshold value and a detection probability according to the false alarm probability.
Similarly, the spectrum sensing system based on the rayleigh fading channel signal envelope disclosed in this embodiment switches the correlation requirement on the sampled signal to the requirement on the signal envelope correlation, and has stronger correlation on the same sampled signal because the signal envelope has a lower spectrum. In order to improve the detection performance, carrier information of a signal is utilized, a signal sampling value is intercepted into an array with equal length according to integral multiple of a carrier (central frequency spectrum) period, and an approximate correlation matrix based on signal envelope is constructed by only calculating correlation characteristics in adjacent periods. Compared with the traditional correlation matrix, the approximate correlation matrix detection increases the center distance (expected distance is increased) between the detection probability distribution function and the false alarm probability distribution function and improves the convergence speed (variance is reduced) of the detection probability distribution function and the false alarm probability distribution function, so that the detection performance of the approximate correlation matrix detection is better for the same false alarm probability, and the detection threshold is only related to the intercepted array quantity and is not related to the system noise. Compared with energy detection, the method has no relation with noise power, so that the problem that the detection cannot be carried out due to uncertainty of noise does not occur. Compared with the traditional correlation detection, the method has the advantages that the requirement of signal correlation is lowered, the same false alarm probability constraint is realized, the calculation of the detection threshold is simplified, and the detection performance is greatly improved.
While certain exemplary embodiments of the present invention have been described above by way of illustration only, it will be apparent to those of ordinary skill in the art that the described embodiments may be modified in various different ways without departing from the spirit and scope of the invention. Accordingly, the foregoing description is illustrative in nature and is not to be construed as limiting the scope of the invention as claimed.
Claims (6)
1. A method for spectrum sensing based on a rayleigh attenuated channel signal envelope, comprising:
step S1, obtaining the transmitting-end modulation signal propagated through the rayleigh fading channel, to obtain:
wherein, L is the number of propagation paths; cnThe nth propagation path amplitude;is the instantaneous phase of the received signal at time t; tau isnDelay time for the nth propagation path; w (t) is additive noise at the receiving end,complex envelope for the transmit baseband signal; f. ofcModulating a carrier frequency; re [. C]Representing a real part;
step S2, based on y (t), a time-varying nonlinear signal with Rayleigh complex envelope is obtained, the envelope waveform is a (t), comprisingLet the sampling period be Ts＝1/(Nfc) That is, if the number of samples collected in one carrier period is N, then t is nTsThe sampling signal at the moment is:
ignore TsAnd constructing a vector:
intercepting the signal sampling value into an array with equal length according to integral multiple of carrier period, calculating the correlation characteristic in adjacent periods, and constructing an approximate correlation matrix as follows:
wherein K is an odd number of 3 or more, i is 0 or more and K is j or less,
and step S3, constructing statistic according to the sub-diagonal element property of the approximate correlation matrix, and judging whether the frequency spectrum of the authorized user is in a silent state or a working state according to the statistic result.
2. The method for sensing frequency spectrum based on rayleigh attenuated channel signal envelope according to claim 1, wherein the step S3 includes:
step S31, the spectrum sensing can be equivalent to the following binary assumption problem, including:
wherein H0 denotes the silence of the authorized user; h1 denotes authorized user work;
when the authorized user is silent,obtaining: the matrix when H0 is assumed to be true is:
when the user is authorized to work with the device,wherein rho is not less than 0ij1 is less than or equal to 1 in the ith 1/fcTime period and jth 1/fcCorrelation coefficient of envelope magnitude in time period, and pij＝ρji(ii) a Obtaining: the matrix when H1 is assumed to be true is:
step S32, the frequency change based on the envelope is very weak relative to the carrier frequency, the envelopes of the sending end signal after channel attenuation in the adjacent carrier period have the same correlation coefficient, and the rho is enabled to beijρ, where | i-j | ═ 1;
step S33, transforming the above-mentioned silence and true approximate correlation matrix in working state to obtain matrix M respectively:
and
wherein,
step S34, taking the sub diagonal element M of the matrix MijAnalysis was performed to construct a statistic T:
obtaining: if T>1, authorizing the user to be in a working state; if T is 1, the authorized user is in a silent state.
3. The method for sensing spectrum based on rayleigh attenuated channel signal envelope according to claim 1 or 2, further comprising:
and setting the false alarm probability of the statistic, and calculating a detection threshold value and a detection probability according to the false alarm probability.
4. A system for spectrum sensing based on a rayleigh attenuated channel signal envelope, comprising:
the first processing module is used for acquiring the transmitting end modulation signal after being propagated through the rayleigh fading channel, and obtaining:
wherein, L is the number of propagation paths; cnThe nth propagation path amplitude;is the instantaneous phase of the received signal at time t; tau isnDelay time for the nth propagation path; w (t) is additive noise at the receiving end,complex envelope for the transmit baseband signal; f. ofcModulating a carrier frequency; re [. C]Representing a real part;
a second processing module for making the envelope waveform a (t) based on y (t) being a time-varying nonlinear signal with Rayleigh complex envelope, havingLet the sampling period be Ts＝1/(Nfc) That is, if the number of samples collected in one carrier period is N, then t is nTsThe sampling signal at the moment is:
ignore TsAnd constructing a vector:
intercepting the signal sampling value into an array with equal length according to integral multiple of carrier period, calculating the correlation characteristic in adjacent periods, and constructing an approximate correlation matrix as follows:
wherein K is an odd number of 3 or more, i is 0 or more and K is j or less,
and the third processing module is used for constructing statistic according to the property of the sub-diagonal elements of the approximate correlation matrix and judging that the frequency spectrum of the authorized user is in a silent state or a working state according to the statistic result.
5. The system according to claim 4, wherein the third processing module comprises:
the first submodule is used for equating the spectrum sensing as a binary hypothesis problem which comprises the following steps:
wherein H0 denotes the silence of the authorized user; h1 denotes authorized user work;
when the authorized user is silent,obtaining: the matrix when H0 is assumed to be true is:
when the user is authorized to work with the device,wherein rho is not less than 0ij1 is less than or equal to 1 in the ith 1/fcTime period and jth 1/fcCorrelation coefficient of envelope magnitude in time period, and pij＝ρji(ii) a Obtaining: the matrix when H1 is assumed to be true is:
and the second submodule is used for enabling the envelope of the signal at the transmitting end after channel attenuation in the adjacent carrier period to have the same correlation coefficient based on the extremely weak change of the frequency change of the envelope relative to the carrier frequency to enable rhoijρ, where | i-j | ═ 1;
and a third submodule for transforming the said silence and true approximate correlation matrix under working state to obtain matrix M:
and
wherein,
submodule four for taking sub diagonal element M of matrix MijAnalysis was performed to construct a statistic T:
obtaining: if T>1, authorizing the user to be in a working state; if T is 1, the authorized user is in a silent state.
6. The system for spectrum sensing based on rayleigh attenuated channel signal envelopes of claim 4 or 5, further comprising:
and the fourth processing module is used for setting the false alarm probability of the statistic and calculating a detection threshold value and a detection probability according to the false alarm probability.
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