CN101944934B - Intercarrier interference elimination-based cognitive OFDMA system carrier detection method - Google Patents

Abstract

The invention discloses an intercarrier interference elimination-based cognitive OFDMA system carrier detection method. The method comprises the following steps of: pre-judging all carriers of which the states are not judged by using a high-conservation threshold lambda H and a low-conservation threshold lambda L by a cognitive user; starting an intercarrier interference elimination algorithm for the carriers of which the states are not judged; determining whether to remove interfering energy from the currently detected carrier energy according to the adjacent carrier state and whether to judge the currently detected carrier state by using a threshold lambda 1; updating the high-conservation threshold lambda H and the low-conservation threshold lambda L according to a set of the carriers of which the states are not judged; and continuously repeating the steps till the states of all carriers are judged. The method overcomes the disadvantage of high false alarm probability because the conventional energy detector cannot identify intercarrier interference and master user signals, and has the advantages of low computational complexity, capacity of resisting the intercarrier interference well, and high detection probability and low false alarm probability under the condition of larger carrier frequency deviation.

Description

A kind of cognitive OFDMA system carrier detection method of eliminating based on inter-carrier interference

Technical field

The present invention relates to wireless communication field, be specifically related to a kind of cognitive OFDMA system carrier detection method of eliminating based on inter-carrier interference.

Background technology

The key technology that cognitive radio technology is the current frequency spectrum resource scarcity of solution, the availability of frequency spectrum is low.It passes through perceived spectral environment reliably, surveys main user's active state, allows unauthorized user dynamically to utilize the available spectrum resource, does not bring harmful interference to authorized user simultaneously in whole communication process.It is the transmission technology that is easy to realize frequency spectrum resource control of generally acknowledging at present that OFDM inserts (OFDMA) technology.The OFDMA technology can be by frequency spectrum combination and cutting distributing system resource between the user neatly, this makes it to combine well with cognitive system.In cognitive OFDMA system, the detection of carrier wave is very crucial, is directly connected to cognitive user to the utilization ratio of usable spectrum with to the interference of authorized user, these two indexs that also design cognitive OFDMA system most critical just.

Traditional detection method mainly comprises: matched filter detects, cycle specificity detects and energy measuring.Wherein matched filter detects the priori (as modulation system, pulse-shaping function, frame format and synchronizing information etc.) that needs known authorized user; Cycle specificity detects utilizes the cyclostationarity of authorization user signal to carry out frequency spectrum perception, distinguishes authorization signal and noise, and this method also can reach the quite good detecting performance under low signal-to-noise ratio, but its computation complexity is very big; Energy measuring is a kind of irrelevant detection, and this method realizes simple, and complexity is low, does not need to know the priori of authorization user signal, therefore is fit to the designing requirement of cognitive system more.

But traditional energy detection method can't be distinguished authorization user signal and interference, therefore detects poor-performing when signal to noise ratio is low.Especially in cognitive OFDMA system, because the inter-carrier interference that carrier wave frequency deviation causes has had a strong impact on the detection performance of carrier wave.Existing way mainly contains two classes, one class is to select for use other detection method to replace energy measuring in order to obtain the quite good detecting performance, as cycle specificity detect (see " Robust Detection of OFDM Signals for Cognitive UWB in low SNR with Noise Uncertainty; " in Personal Indoor and Mobile Radio Communications, 2008.PIMRC2008.IEEE 19 ^ThInternational Symposium.), this method mainly makes up the purpose that auto-correlation function reaches the main subscriber signal of detection by the ofdm signal to main user.This method has the quite good detecting performance under low signal-to-noise ratio, but the computation complexity height of this method, and it is big to detect time-delay, and it can't be used in the middle of the system of reality.Another kind of method mainly is the characteristics that are subject to unknown noise and interference effect at the conventional energy detector, method by design multi-threshold or adaptive threshold can change the thresholding of energy measuring along with the variation of external interference, thereby reach the purpose that strengthen to detect performance (see " Adaptive Two Thresholds Based Energy Detection for Cooperative Spectrum Sensing; " in Consumer Conmmunications and Networking Conference (CCNC), 2,010 7 ^ThIEEE, 2010; " An Adaptive Threshold Method for Spectrum Sensing in Multi-Channel Cognitive Radio Networks, " in Telecommunications (ICT), 2010 IEEE 17 ^ThInternational Conference, 2010).These class methods mainly are to design at unknown disturbances, therefore initiatively do not use the characteristic of disturbing.

We are by finding that to the analysis of inter-carrier interference in the cognitive OFDMA system inter-carrier interference energy distributions is that certain feature is arranged.If we can reasonably develop this feature and use, can be very helpful to the detection performance that improves carrier wave in the cognitive OFDMA system.The analysis result of interference model shows between cognitive OFDMA system carrier, when having carrier wave frequency deviation, energy on each carrier wave is that the mode with weighting is leaked on all the other carrier waves, and weight factor depends on the frequency deviation of interfering carrier and the distance between interfering carrier and the current detection carrier wave.If therefore imagination we can detect the state of part carrier wave by pre-judgement, so just can progressively eliminate the interfering energy of busy carrier wave leakage to all the other carrier waves, thereby the minimizing inter-carrier interference detects Effect on Performance to carrier wave.

As inspiration, this patent is in conjunction with proposing a kind of cognitive OFDMA system carrier detection method of eliminating based on inter-carrier interference.

Summary of the invention

The objective of the invention is to overcome the deficiencies in the prior art, propose a kind of cognitive OFDMA system carrier detection method of eliminating based on inter-carrier interference.

The step of the cognitive OFDMA system carrier detection method of eliminating based on inter-carrier interference is as follows:

(a) cognitive user is utilized high conservative thresholding initial value

With minimum living limit on duty at the gate initial value

All carrier waves of not judging state are judged in advance energy is greater than the conservative thresholding initial value of height

Carrier State be judged as busyly, energy is less than the minimum living limit initial value of keeping goal Carrier State be judged as the spare time, remaining Carrier State temporarily can't be judged;

(b) to not judging the carrier wave of state, start the inter-carrier interference elimination algorithm, determine whether interfering energy will be removed according to adjacent Carrier State from the carrier energy of current detection, and whether utilize thresholding λ ₁Carrier State to current detection is judged;

(c) all be judged as Carrier State, then carrier wave detect to finish, all do not judged as Carrier State, then according to the carrier set of not judging state the more conservative thresholding of new peak be λ ' _H, upgrade the minimum living λ ' that is limited on duty at the gate _L, change step (d) over to;

(d) utilize the conservative thresholding λ ' of the height that upgrades in the step (c) _HWith the minimum living of upgrading limit on duty at the gate λ ' _LThe carrier wave of not judging state is judged in advance energy is greater than the conservative thresholding λ ' of the height that upgrades _HCarrier State be judged as busyly, energy is less than the minimum living of the upgrading limit λ ' that keeps goal _LCarrier State be judged as the spare time, remaining Carrier State temporarily can't be judged, changes step (b) over to.

Cognitive user described in the step (a) is utilized high conservative thresholding initial value

With minimum living limit on duty at the gate initial value

All carrier waves of not judging state are judged in advance energy is greater than the conservative thresholding initial value of height

Carrier State be judged as busyly, energy is less than the minimum living limit initial value of keeping goal

Carrier State be judged as the spare time, remaining Carrier State temporarily can't determining step be: utilize following formula to calculate the initial value of high conservative thresholding

Initial value with minimum living limit on duty at the gate

The initial value of high conservative thresholding ${\mathrm{\λ}}_H^{*}=P_{\mathrm{AVE}}+\frac{\underset{i=1}{\overset{N}{\mathrm{\Σ}}}{(P_i^r-P_{\mathrm{AVE}})}^{+}}{\mathrm{Num}(P_i^r>P_{\mathrm{AVE}})},$ Wherein ${\left(a\right)}^{+}=\left\{\begin{array}{c}a,a>0\\ 0,a\≤0\end{array}\right.$

The initial value that minimum living is kept goal and limit ${\mathrm{\&lambda;}}_L^{*}=P_{\mathrm{AVE}}+\frac{\underset{i=1}{\overset{N}{\mathrm{\&Sigma;}}}{(P_i^r-P_{\mathrm{AVE}})}^{-}}{\mathrm{Num}(P_i^r<P_{\mathrm{AVE}})},$ Wherein ${\left(a\right)}^{-}=\left\{\begin{array}{c}a,a<0\\ 0,a\&GreaterEqual;0\end{array}\right.$

I is the carrier wave label in the formula, and N is the carrier wave number,

Be cognitive user detected energy on i carrier wave, P _AVEBe the average energy of all carrier waves,

Expression is satisfied

The carrier wave number, utilize the conservative thresholding initial value of the height calculate

With minimum living limit on duty at the gate initial value

All carrier waves of not judging state are judged in advance energy is greater than the conservative thresholding initial value of height

Carrier State be judged as busyly, energy is less than the minimum living limit initial value of keeping goal

Carrier State be judged as the spare time, remaining Carrier State temporarily can't be judged.

Described in the step (b) to not judging the carrier wave of state, start inter-carrier interference elimination algorithm step and be:

The carrier wave of supposing current detection is i carrier wave, and the value of i satisfies 1≤i≤N,

Is 1) state of i-1 carrier wave of inspection busy? be not then to change step 2 over to), be that the energy that then upgrades i carrier wave is

Judge

Whether less than thresholding λ ₁Be, then judge i carrier wave for not busy, the judgement of current carrier wave finishes, and changes step 5) over to, and not, then the state of i carrier wave is still undetermined, changes step 2 over to), inter-carrier interference energy I _{K '}Calculated by following formula:

$I_{k^{\&prime;}}=E_{\mathrm{\&epsiv;}}\left[P_{k^{\&prime;}}^r{\left|\frac{\sin \left(\mathrm{\&pi;}(k^{\&prime;}-i+{\mathrm{\&epsiv;}}_{k^{\&prime;}})\right)}{K\sin \left(\frac{\mathrm{\&pi;}}{K}(k^{\&prime;}-i+{\mathrm{\&epsiv;}}_{k^{\&prime;}})\right)}\right|}^2\right]$

$=P_{k^{\&prime;}}^r{\&Integral;}_{-{\mathrm{\&epsiv;}}_m}^{{\mathrm{\&epsiv;}}_m}{\left|\frac{\sin \left(\mathrm{\&pi;}(k^{\&prime;}-i+{\mathrm{\&epsiv;}}_{k^{\&prime;}})\right)}{K\sin \left(\frac{\mathrm{\&pi;}}{K}(k^{\&prime;}-i+{\mathrm{\&epsiv;}}_{k^{\&prime;}})\right)}\right|}^{2}p\left(\mathrm{\&epsiv;}\right)\mathrm{d\&epsiv;}$

K ' is interfering carrier number in the formula, k '=i-1,

Be cognitive user detected energy on the individual carrier wave of k ', ε _mBe the frequency deviation region of authorized user maximum, p (ε) is the frequency deviation probability density function of authorized user, thresholding λ ₁Can be calculated by following formula:

${\mathrm{\&lambda;}}_1=(\frac{Q^{-1}\left(P_{\mathrm{fa}}\right)}{\sqrt{N}}+1){\mathrm{\&sigma;}}^2$

P in the formula _FaBe the false alarm probability binding occurrence of setting, N is sampling number, σ ²Be noise variance;

Is 2) state of i+1 carrier wave of inspection busy? be not, then change step 3) over to, be, the energy that then upgrades i carrier wave is

Judge

Whether less than thresholding λ ₁Be, then judge i carrier wave for not busy, the judgement of current carrier wave finishes, and changes step 5) over to, and not, then the state of i carrier wave is still undetermined, changes step 3) over to;

Is 3) state of i-2 carrier wave of inspection busy? be not, then change step 4) over to, be, the energy that then upgrades i carrier wave is

Judge Whether less than thresholding λ ₁Be, then judge i carrier wave for not busy, the judgement of current carrier wave finishes, and changes step 5) over to, and not, then the state of i carrier wave is still undetermined, changes step 4) over to;

Is 4) state of i+2 carrier wave of inspection busy? be not, then change step 5) over to, be, the energy that then upgrades i carrier wave is

Judge

Whether less than thresholding λ ₁Be, then judge i carrier wave for not busy, the judgement of current carrier wave finishes, and changes step 5) over to, and not, then the state of i carrier wave is still undetermined, changes step 5) over to;

5) judge whether that all carrier waves of not judging state all traverse? be, then the epicycle algorithm finishes, and not, selects the next carrier wave of not judging state, changes step 1) over to.

If i=1, then the value of i-1 is got N, and the value of i-2 is got N-1, if i=2, then the value of i-2 is got N, if i=N-1, then the value of i+2 gets 1, if i=N, then the value of the i+1 value of getting 1, i+2 gets 2, and all the other situations are according to the result of calculation value.

All not judged as Carrier State described in the step (c), then according to the carrier set of not judging the more conservative thresholding of new peak be λ ' _H, upgrade the minimum living λ ' that is limited on duty at the gate _LStep is:

According to the carrier set of not judging the more conservative thresholding of new peak be λ ' _HWith the renewal minimum living λ ' that is limited on duty at the gate _LFormula as follows:

The conservative thresholding of the height that upgrades ${\mathrm{\&lambda;}}_H^{\&prime;}=P_{\mathrm{AVE}\_D}+\frac{\underset{i\&Element;D}{\mathrm{\&Sigma;}}{(P_i^r-P_{\mathrm{AVE}\_D})}^{+}}{\mathrm{Num}(P_i^r>P_{\mathrm{AVE}\_D}|i\&Element;D)},$ Wherein ${\left(a\right)}^{+}\text{=}\left\{\begin{array}{c}a,a>0\\ 0,a\&le;0\end{array}\right.$

The minimum living of upgrading is kept goal and is limit ${\mathrm{\&lambda;}}_L^{\&prime;}=P_{\mathrm{AVE}\_D}+\frac{\underset{i\&Element;D}{\mathrm{\&Sigma;}}{(P_i^r-P_{\mathrm{AVE}\_D})}^{-}}{\mathrm{Num}(P_i^r<P_{\mathrm{AVE}\_D}|i\&Element;D)},$ Wherein ${\left(a\right)}^{-}=\left\{\begin{array}{c}a,a<0\\ 0,a\&GreaterEqual;0\end{array}\right.$

D represents the current carrier set of not judging, P in the formula _{AVE_D}Represent the current average energy of not judging carrier wave.Num (P _i＜P _{AVE_D}| i ∈ D) be illustrated in the carrier wave of not judging and satisfy carrier energy less than average value P _{AVE_D}The carrier wave number.

The present invention has overcome traditional energy detector can't disturb the defective that produces high false-alarm with main subscriber signal between discriminatory carrier.The computation complexity of this method is low, but can resist inter-carrier interference well, is still keeping very high detection probability and very low false alarm probability under the bigger situation of carrier wave frequency deviation.

Description of drawings

Fig. 1 is based on the carrier wave testing process block diagram that inter-carrier interference is eliminated;

The carrier wave that Fig. 2 is based on the inter-carrier interference elimination algorithm detects realization flow figure;

Fig. 3 utilizes conservative thresholding λ _HAnd λ _LCarrier State is carried out the schematic diagram of pre-estimation;

Fig. 4 is the schematic diagram of inter-carrier interference energy elimination algorithm;

Fig. 5 is that given false alarm probability is 0.01, and sampling number is 100, and peak carrier deviation is respectively 0.125 and at 0.25 o'clock, the simulation curve figure that the detection probability of algorithm changes with signal to noise ratio among traditional algorithm and the present invention;

Fig. 6 is that given false alarm probability is 0.01, and sampling number is 1000, and peak carrier deviation is respectively 0.125 and at 0.25 o'clock, the simulation curve figure that the detection probability of algorithm changes with signal to noise ratio among traditional algorithm and the present invention;

Fig. 7 is that given false alarm probability is 0.01, and sampling number is 100, and peak carrier deviation is respectively 0.125 and at 0.25 o'clock, the simulation curve figure that the false alarm probability of algorithm changes with signal to noise ratio among traditional algorithm and the present invention;

Fig. 8 is that given false alarm probability is 0.01, and sampling number is 1000, and peak carrier deviation is respectively 0.125 and at 0.25 o'clock, the simulation curve figure that the false alarm probability of algorithm changes with signal to noise ratio among traditional algorithm and the present invention.

Embodiment

The step of the cognitive OFDMA system carrier detection method of eliminating based on inter-carrier interference is as follows:

(a) cognitive user is utilized high conservative thresholding initial value

With minimum living limit on duty at the gate initial value

All carrier waves of not judging state are judged in advance energy is greater than the conservative thresholding initial value of height

Carrier State be judged as busyly, energy is less than the minimum living limit initial value of keeping goal

Carrier State be judged as the spare time, remaining Carrier State temporarily can't be judged;

(b) to not judging the carrier wave of state, start the inter-carrier interference elimination algorithm, determine whether interfering energy will be removed according to adjacent Carrier State from the carrier energy of current detection, and whether utilize thresholding λ ₁Carrier State to current detection is judged;

(c) all be judged as Carrier State, then carrier wave detect to finish, all do not judged as Carrier State, then according to the carrier set of not judging state the more conservative thresholding of new peak be λ ' _H, upgrade the minimum living λ ' that is limited on duty at the gate _L, change step (d) over to;

(d) utilize the conservative thresholding λ ' of the height that upgrades in the step (c) _HWith the minimum living of upgrading limit on duty at the gate λ ' _LThe carrier wave of not judging state is judged in advance energy is greater than the conservative thresholding λ ' of the height that upgrades _HCarrier State be judged as busyly, energy is less than the minimum living of the upgrading limit λ ' that keeps goal _LCarrier State be judged as the spare time, remaining Carrier State temporarily can't be judged, changes step (b) over to.

Cognitive user described in the step (a) is utilized high conservative thresholding initial value With minimum living limit on duty at the gate initial value

All carrier waves of not judging state are judged in advance energy is greater than the conservative thresholding initial value of height

Carrier State be judged as busyly, energy is less than the minimum living limit initial value of keeping goal

Carrier State be judged as the spare time, remaining Carrier State temporarily can't determining step be: utilize following formula to calculate the initial value of high conservative thresholding

Initial value with minimum living limit on duty at the gate

The initial value of high conservative thresholding ${\mathrm{\&lambda;}}_H^{*}=P_{\mathrm{AVE}}+\frac{\underset{i=1}{\overset{N}{\mathrm{\&Sigma;}}}{(P_i^r-P_{\mathrm{AVE}})}^{+}}{\mathrm{Num}(P_i^r>P_{\mathrm{AVE}})},$ Wherein ${\left(a\right)}^{+}=\left\{\begin{array}{c}a,a>0\\ 0,a\&le;0\end{array}\right.$

The initial value that minimum living is kept goal and limit ${\mathrm{\&lambda;}}_L^{*}=P_{\mathrm{AVE}}+\frac{\underset{i=1}{\overset{N}{\mathrm{\&Sigma;}}}{(P_i^r-P_{\mathrm{AVE}})}^{-}}{\mathrm{Num}(P_i^r<P_{\mathrm{AVE}})},$ Wherein ${\left(a\right)}^{-}=\left\{\begin{array}{c}a,a<0\\ 0,a\&GreaterEqual;0\end{array}\right.$

I is the carrier wave label in the formula, and N is the carrier wave number,

Be cognitive user detected energy on i carrier wave, P _AVEBe the average energy of all carrier waves,

Expression is satisfied

The carrier wave number, utilize the conservative thresholding initial value of the height calculate

With minimum living limit on duty at the gate initial value

All carrier waves of not judging state are judged in advance energy is greater than the conservative thresholding initial value of height Carrier State be judged as busyly, energy is less than the minimum living limit initial value of keeping goal

Carrier State be judged as the spare time, remaining Carrier State temporarily can't be judged.

Described in the step (b) to not judging the carrier wave of state, start inter-carrier interference elimination algorithm step and be:

The carrier wave of supposing current detection is i carrier wave, and the value of i satisfies 1≤i≤N,

Is 1) state of i-1 carrier wave of inspection busy? be not then to change step 2 over to), be that the energy that then upgrades i carrier wave is Judge

Whether less than thresholding λ ₁Be, then judge i carrier wave for not busy, the judgement of current carrier wave finishes, and changes step 5) over to, and not, then the state of i carrier wave is still undetermined, changes step 2 over to), inter-carrier interference energy I _{K '}Calculated by following formula:

$I_{k^{\&prime;}}=E_{\mathrm{\&epsiv;}}\left[P_{k^{\&prime;}}^r{\left|\frac{\sin \left(\mathrm{\&pi;}(k^{\&prime;}-i+{\mathrm{\&epsiv;}}_{k^{\&prime;}})\right)}{K\sin \left(\frac{\mathrm{\&pi;}}{K}(k^{\&prime;}-i+{\mathrm{\&epsiv;}}_{k^{\&prime;}})\right)}\right|}^2\right]$

$=P_{k^{\&prime;}}^r{\&Integral;}_{-{\mathrm{\&epsiv;}}_m}^{{\mathrm{\&epsiv;}}_m}{\left|\frac{\sin \left(\mathrm{\&pi;}(k^{\&prime;}-i+{\mathrm{\&epsiv;}}_{k^{\&prime;}})\right)}{K\sin \left(\frac{\mathrm{\&pi;}}{K}(k^{\&prime;}-i+{\mathrm{\&epsiv;}}_{k^{\&prime;}})\right)}\right|}^{2}p\left(\mathrm{\&epsiv;}\right)\mathrm{d\&epsiv;}$

K ' is interfering carrier number in the formula, k '=i-1,

Be cognitive user detected energy on the individual carrier wave of k ', ε _mBe the frequency deviation region of authorized user maximum, p (ε) is the frequency deviation probability density function of authorized user, thresholding λ ₁Can be calculated by following formula:

${\mathrm{\&lambda;}}_1=(\frac{Q^{-1}\left(P_{\mathrm{fa}}\right)}{\sqrt{N}}+1){\mathrm{\&sigma;}}^2$

P in the formula _FaBe the false alarm probability binding occurrence of setting, N is sampling number, σ ²Be noise variance;

Is 2) state of i+1 carrier wave of inspection busy? be not, then change step 3) over to, be, the energy that then upgrades i carrier wave is

Judge Whether less than thresholding λ ₁Be, then judge i carrier wave for not busy, the judgement of current carrier wave finishes, and changes step 5) over to, and not, then the state of i carrier wave is still undetermined, changes step 3) over to;

Is 3) state of i-2 carrier wave of inspection busy? be not, then change step 4) over to, be, the energy that then upgrades i carrier wave is

Judge

Whether less than thresholding λ ₁Be, then judge i carrier wave for not busy, the judgement of current carrier wave finishes, and changes step 5) over to, and not, then the state of i carrier wave is still undetermined, changes step 4) over to;

Is 4) state of i+2 carrier wave of inspection busy? be not, then change step 5) over to, be, the energy that then upgrades i carrier wave is Judge

Whether less than thresholding λ ₁Be, then judge i carrier wave for not busy, the judgement of current carrier wave finishes, and changes step 5) over to, and not, then the state of i carrier wave is still undetermined, changes step 5) over to;

5) judge whether that all carrier waves of not judging state all traverse? be, then the epicycle algorithm finishes, and not, selects the next carrier wave of not judging state, changes step 1) over to.

If i=1, then the value of i-1 is got N, and the value of i-2 is got N-1, if i=2, then the value of i-2 is got N, if i=N-1, then the value of i+2 gets 1, if i=N, then the value of the i+1 value of getting 1, i+2 gets 2, and all the other situations are according to the result of calculation value.

All not judged as Carrier State described in the step (c), then according to the carrier set of not judging the more conservative thresholding of new peak be λ ' _H, upgrade the minimum living λ ' that is limited on duty at the gate _LStep is:

According to the carrier set of not judging the more conservative thresholding of new peak be λ ' _HWith the renewal minimum living λ ' that is limited on duty at the gate _LFormula as follows:

The conservative thresholding of the height that upgrades ${\mathrm{\&lambda;}}_H^{\&prime;}=P_{\mathrm{AVE}\_D}+\frac{\underset{i\&Element;D}{\mathrm{\&Sigma;}}{(P_i^r-P_{\mathrm{AVE}\_D})}^{+}}{\mathrm{Num}(P_i^r>P_{\mathrm{AVE}\_D}|i\&Element;D)},$ Wherein ${\left(a\right)}^{+}=\left\{\begin{array}{c}a,a>0\\ 0,a\&le;0\end{array}\right.$

The minimum living of upgrading is kept goal and is limit ${\mathrm{\&lambda;}}_L^{\&prime;}=P_{\mathrm{AVE}\_D}+\frac{\underset{i\&Element;D}{\mathrm{\&Sigma;}}{(P_i^r-P_{\mathrm{AVE}\_D})}^{-}}{\mathrm{Num}(P_i^r<P_{\mathrm{AVE}\_D}|i\&Element;D)},$ Wherein ${\left(a\right)}^{-}=\left\{\begin{array}{c}a,a<0\\ 0,a\&GreaterEqual;0\end{array}\right.$

D represents the current carrier set of not judging, P in the formula _{AVE_D}Represent the current average energy of not judging carrier wave.Num (P _i＜P _{AVE_D}| i ∈ D) be illustrated in the carrier wave of not judging and satisfy carrier energy less than average value P _{AVE_D}The carrier wave number.

Embodiment

In a kind of cognitive OFDMA system carrier detection method of eliminating based on inter-carrier interference of the present invention, cognitive OFDMA system is made up of N=256 carrier wave, licenses to the individual main user's use of M=256, and each main user uses 1 carrier wave.The situation that authorized user takies carrier wave is a vector by 0,1 256 length that constitute that generates at random, and wherein 0 represents the vacant carrier wave of authorized user, and 1 expression authorized user takies carrier wave, and the geometry that 0,1 number is obeyed (0.5,0.5) distributes.Authorized user is according to the energy of noise and the energy of signal to noise ratio decision transmission data, and The data BPSK modulation system.The carrier wave frequency deviation value of authorized user is obeyed [ε _m, ε _m] interior even distribution, ε _mBe peak carrier deviation, get 0.125 and 0.25 two kind of situation respectively and compare that the false alarm probability binding occurrence of setting is 0.01, it is 0 that noise is obeyed average, and variance is 1 Gaussian Profile.Sampled point is got 100 and 1,000 two kinds of situations respectively and is compared.A kind of cognitive OFDMA system carrier detection method of eliminating based on inter-carrier interference of the present invention may further comprise the steps as shown in Figure 2:

(a) cognitive user is utilized high conservative thresholding initial value

With minimum living limit on duty at the gate initial value

All carrier waves of not judging state are judged in advance energy is greater than the conservative thresholding initial value of height

Carrier State be judged as busyly, energy is less than the minimum living limit initial value of keeping goal

Carrier State be judged as the spare time, remaining Carrier State temporarily can't be judged;

(b) to not judging the carrier wave of state, start the inter-carrier interference elimination algorithm, determine whether interfering energy will be removed according to adjacent Carrier State from the carrier energy of current detection, and whether utilize thresholding λ ₁Carrier State to current detection is judged;

(c) all be judged as Carrier State, then carrier wave detect to finish, all do not judged as Carrier State, then according to the carrier set of not judging state the more conservative thresholding of new peak be λ ' _H, upgrade the minimum living λ ' that is limited on duty at the gate _L, change step (d) over to;

(d) utilize the conservative thresholding λ ' of the height that upgrades in the step (c) _HWith the minimum living of upgrading limit on duty at the gate λ ' _LThe carrier wave of not judging state is judged in advance energy is greater than the conservative thresholding λ ' of the height that upgrades _HCarrier State be judged as busyly, energy is less than the minimum living of the upgrading limit λ ' that keeps goal _LCarrier State be judged as the spare time, remaining Carrier State temporarily can't be judged, changes step (b) over to.

High conservative thresholding initial value in the step (a)

With minimum living limit on duty at the gate initial value

Can be calculated by following formula:

${\mathrm{\&lambda;}}_H^{*}=P_{\mathrm{AVE}}+\frac{\underset{i=1}{\overset{256}{\mathrm{\&Sigma;}}}{(P_i^r-P_{\mathrm{AVE}})}^{+}}{\mathrm{Num}(P_i^r>P_{\mathrm{AVE}})},$ Wherein ${\left(a\right)}^{+}=\left\{\begin{array}{c}a,a>0\\ 0,a\&le;0\end{array}\right.$

${\mathrm{\&lambda;}}_L^{*}=P_{\mathrm{AVE}}+\frac{\underset{i=1}{\overset{256}{\mathrm{\&Sigma;}}}{(P_i^r-P_{\mathrm{AVE}})}^{-}}{\mathrm{Num}(P_i^r<P_{\mathrm{AVE}})},$ Wherein ${\left(a\right)}^{-}=\left\{\begin{array}{c}a,a<0\\ 0,a\&GreaterEqual;0\end{array}\right.$

I is the carrier wave label in the formula, Be cognitive user detected energy on i carrier wave, P _AVEBe the average energy of all carrier waves,

Expression is satisfied

The carrier wave number.

Described in the step b) to not judging the carrier wave of state, start inter-carrier interference elimination algorithm step and be:

The carrier wave of supposing current detection is i carrier wave, and the value of i satisfies 1≤i≤N,

Is 1) state of i-1 carrier wave of inspection busy? be not then to enter step 2), be that the energy that then upgrades i carrier wave is

Judge

Whether less than thresholding λ ₁Be, then judge i carrier wave for not busy, the judgement of current carrier wave finishes, and changes step 5) over to, and not, then the state of i carrier wave is still undetermined, changes step 2 over to), i-1 carrier wave to the interfering energy of i carrier wave is:

Peak carrier deviation ε _m=0.125 o'clock:

$I_{i-1}=E_{\mathrm{\&epsiv;}}\left[P_{i-1}^r{\left|\frac{\sin \left(\mathrm{\&pi;}(-1+\mathrm{\&epsiv;})\right)}{256\sin \left(\frac{\mathrm{\&pi;}}{256}(-1+\mathrm{\&epsiv;})\right)}\right|}^2\right]$

$=P_{i-1}^r{\&Integral;}_{-0.125}^{0.125}{\left|\frac{\sin \left(\mathrm{\&pi;}(-1+\mathrm{\&epsiv;})\right)}{256\sin \left(\frac{\mathrm{\&pi;}}{256}(-1+\mathrm{\&epsiv;})\right)}\right|}^2\frac{1}{0.25}\mathrm{d\&epsiv;}=0.0052P_{i-1}^r$

Peak carrier deviation ε _m=0.25 o'clock:

$I_{i-1}=E_{\mathrm{\&epsiv;}}\left[P_{i-1}^r{\left|\frac{\sin \left(\mathrm{\&pi;}(-1+\mathrm{\&epsiv;})\right)}{256\sin \left(\frac{\mathrm{\&pi;}}{256}(-1+\mathrm{\&epsiv;})\right)}\right|}^2\right]$

$=P_{i-1}^r{\&Integral;}_{-0.25}^{0.25}{\left|\frac{\sin \left(\mathrm{\&pi;}(-1+\mathrm{\&epsiv;})\right)}{256\sin \left(\frac{\mathrm{\&pi;}}{256}(-1+\mathrm{\&epsiv;})\right)}\right|}^2\frac{1}{0.5}\mathrm{d\&epsiv;}=0.0207P_{i-1}^r$

In the formula

Be cognitive user detected energy on i-1 carrier wave, thresholding λ ₁Can be calculated by following formula:

During sampled point N=100:

${\mathrm{\&lambda;}}_1=(\frac{Q^{-1}\left(0.01\right)}{\sqrt{100}}+1)\&times;1=1.2326$

During sampled point N=100:

${\mathrm{\&lambda;}}_1=(\frac{Q^{-1}\left(0.01\right)}{\sqrt{100}}+1)\&times;1=1.0736$

Is 2) state of i+1 carrier wave of inspection busy? be not, then enter step 3), be, the energy that then upgrades i carrier wave is

Judge

Whether less than thresholding λ ₁Be, then judge i carrier wave for not busy, the judgement of current carrier wave finishes, and changes step 5) over to, and not, then the state of i carrier wave is still undetermined, changes step 3) over to, and i+1 carrier wave to the interfering energy of i carrier wave is:

Peak carrier deviation ε _m=0.125 o'clock:

$I_{i+1}=E_{\mathrm{\&epsiv;}}\left[P_{i+1}^r{\left|\frac{\sin \left(\mathrm{\&pi;}(1+\mathrm{\&epsiv;})\right)}{256\sin \left(\frac{\mathrm{\&pi;}}{256}(1+\mathrm{\&epsiv;})\right)}\right|}^2\right]$

$=P_{i+1}^r{\&Integral;}_{-0.125}^{0.125}{\left|\frac{\sin \left(\mathrm{\&pi;}(1+\mathrm{\&epsiv;})\right)}{256\sin \left(\frac{\mathrm{\&pi;}}{256}(1+\mathrm{\&epsiv;})\right)}\right|}^2\frac{1}{0.25}\mathrm{d\&epsiv;}=0.0052P_{i+1}^r$

Peak carrier deviation ε _m=0.25 o'clock:

$I_{i+1}=E_{\mathrm{\&epsiv;}}\left[P_{i+1}^r{\left|\frac{\sin \left(\mathrm{\&pi;}(1+\mathrm{\&epsiv;})\right)}{256\sin \left(\frac{\mathrm{\&pi;}}{256}(1+\mathrm{\&epsiv;})\right)}\right|}^2\right]$

$=P_{i+1}^r{\&Integral;}_{-0.25}^{0.25}{\left|\frac{\sin \left(\mathrm{\&pi;}(1+\mathrm{\&epsiv;})\right)}{256\sin \left(\frac{\mathrm{\&pi;}}{256}(1+\mathrm{\&epsiv;})\right)}\right|}^2\frac{1}{0.5}\mathrm{d\&epsiv;}=0.0207P_{i+1}^r$

In the formula

Be cognitive user detected energy on i+1 carrier wave;

Is 3) state of i-2 carrier wave of inspection busy? be not, then enter step 4), be, the energy that then upgrades i carrier wave is Judge Whether less than thresholding λ ₁Be, then judge i carrier wave for not busy, the judgement of current carrier wave finishes, and changes step 5) over to, and not, then the state of i carrier wave is still undetermined, changes step 4) over to, and i-2 carrier wave to the interfering energy of i carrier wave is:

Peak carrier deviation ε _m=0.125 o'clock:

$I_{i-2}=E_{\mathrm{\&epsiv;}}\left[P_{i-2}^r{\left|\frac{\sin \left(\mathrm{\&pi;}(-2+\mathrm{\&epsiv;})\right)}{256\sin \left(\frac{\mathrm{\&pi;}}{256}(-2+\mathrm{\&epsiv;})\right)}\right|}^2\right]$

$=P_{i-2}^r{\&Integral;}_{-0.125}^{0.125}{\left|\frac{\sin \left(\mathrm{\&pi;}(-2+\mathrm{\&epsiv;})\right)}{256\sin \left(\frac{\mathrm{\&pi;}}{256}(-2+\mathrm{\&epsiv;})\right)}\right|}^2\frac{1}{0.25}\mathrm{d\&epsiv;}=0.0013P_{i-2}^r$

Peak carrier deviation ε _m=0.25 o'clock:

$I_{i-2}=E_{\mathrm{\&epsiv;}}\left[P_{i-2}^r{\left|\frac{\sin \left(\mathrm{\&pi;}(-2+\mathrm{\&epsiv;})\right)}{256\sin \left(\frac{\mathrm{\&pi;}}{256}(-2+\mathrm{\&epsiv;})\right)}\right|}^2\right]$

$=P_{\text{i-2}}^{\text{r}}{\&Integral;}_{-0.25}^{0.25}{\left|\frac{\sin \left(\mathrm{\&pi;}(-2+\mathrm{\&epsiv;})\right)}{256\sin \left(\frac{\mathrm{\&pi;}}{256}(-2+\mathrm{\&epsiv;})\right)}\right|}^2\frac{1}{0.5}\mathrm{d\&epsiv;}=0.0048P_{i-2}^r$

In the formula

Be cognitive user detected energy on i-2 carrier wave;

Is 4) state of i+2 carrier wave of inspection busy? be not, then enter step 5), be, the energy that then upgrades i carrier wave is Judge

Whether less than thresholding λ ₁Be, then judge i carrier wave for not busy, the judgement of current carrier wave finishes, and changes step 5) over to, and not, then the state of i carrier wave is still undetermined, changes step 5) over to, and i+2 carrier wave to the interfering energy of i carrier wave is:

Peak carrier deviation ε _m=0.125 o'clock:

$I_{i+2}=E_{\mathrm{\&epsiv;}}\left[P_{i+2}^r{\left|\frac{\sin \left(\mathrm{\&pi;}(2+\mathrm{\&epsiv;})\right)}{256\sin \left(\frac{\mathrm{\&pi;}}{256}(2+\mathrm{\&epsiv;})\right)}\right|}^2\right]$

$=P_{i+2}^r{\&Integral;}_{-0.125}^{0.125}{\left|\frac{\sin \left(\mathrm{\&pi;}(2+\mathrm{\&epsiv;})\right)}{256\sin \left(\frac{\mathrm{\&pi;}}{256}(2+\mathrm{\&epsiv;})\right)}\right|}^2\frac{1}{0.25}\mathrm{d\&epsiv;}=0.0013P_{i+2}^r$

Peak carrier deviation ε _m=0.25 o'clock:

$I_{i+2}=E_{\mathrm{\&epsiv;}}\left[P_{i+2}^r{\left|\frac{\sin \left(\mathrm{\&pi;}(2+\mathrm{\&epsiv;})\right)}{256\sin \left(\frac{\mathrm{\&pi;}}{256}(2+\mathrm{\&epsiv;})\right)}\right|}^2\right]$

$=P_{i+2}^r{\&Integral;}_{-0.25}^{0.25}{\left|\frac{\sin \left(\mathrm{\&pi;}(2+\mathrm{\&epsiv;})\right)}{256\sin \left(\frac{\mathrm{\&pi;}}{256}(2+\mathrm{\&epsiv;})\right)}\right|}^2\frac{1}{0.5}\mathrm{d\&epsiv;}=0.0048P_{i+2}^r$

In the formula

Be cognitive user detected energy on i+2 carrier wave;

5) judge whether that all carrier waves of not judging state all traverse? be, then the epicycle algorithm finishes, and not, then selects the next carrier wave of not judging state, enters step 1).

If i=1, then the value of i-1 is got N, and the value of i-2 is got N-1, if i=2, then the value of i-2 is got N, if i=N-1, then the value of i+2 gets 1, if i=N, then the value of the i+1 value of getting 1, i+2 gets 2, and all the other situations are according to the result of calculation value.

In the step (c) according to the carrier set of not judging state the more conservative thresholding of new peak be λ ' _HWith the renewal minimum living λ ' that is limited on duty at the gate _LFormula as follows:

The conservative thresholding of the height that upgrades ${\mathrm{\&lambda;}}_H^{\&prime;}=P_{\mathrm{AVE}\_D}+\frac{\underset{i\&Element;D}{\mathrm{\&Sigma;}}{(P_i^r-P_{\mathrm{AVE}\_D})}^{+}}{\mathrm{Num}(P_i^r>P_{\mathrm{AVE}\_D}|i\&Element;D)},$ Wherein ${\left(a\right)}^{+}=\left\{\begin{array}{c}a,a>0\\ 0,a\&le;0\end{array}\right.$

The minimum living of upgrading is kept goal and is limit ${\mathrm{\&lambda;}}_L^{\&prime;}=P_{\mathrm{AVE}\_D}+\frac{\underset{i\&Element;D}{\mathrm{\&Sigma;}}{(P_i^r-P_{\mathrm{AVE}\_D})}^{-}}{\mathrm{Num}(P_i^r<P_{\mathrm{AVE}\_D}|i\&Element;D)},$ Wherein ${\left(a\right)}^{-}=\left\{\begin{array}{c}a,a<0\\ 0,a\&GreaterEqual;0\end{array}\right.$

D represents the current carrier set of not judging, P in the formula _{AVE_D}Represent the current average energy of not judging carrier wave.Num (P _i＜P _{AVE_D}| i ∈ D) be illustrated in the carrier wave of not judging and satisfy carrier energy less than average value P _{AVE_D}The carrier wave number.

Fig. 5 be sampled point be the detection probability of 100 o'clock methods of the present invention and conventional energy detection method with the change curve of signal to noise ratio, Fig. 6 is that sampled point is that the detection probability of 1000 o'clock methods of the present invention and conventional energy detection method is with the change curve of signal to noise ratio.Both detection probabilities all increase along with the increase of signal to noise ratio as can be seen, reduce along with the increase of carrier wave frequency deviation.When adopting point to increase, both detection probabilities all are greatly improved.Fig. 7 be sampled point be the false alarm probability of 100 o'clock methods of the present invention and conventional energy detection method with the change curve of signal to noise ratio, Fig. 8 is that sampled point is that the false alarm probability of 1000 o'clock methods of the present invention and conventional energy detection method is with the change curve of signal to noise ratio.As can be seen from Figures 7 and 8, traditional energy detection method false alarm probability increases fast along with the increase of signal to noise ratio, method of the present invention then good restraining the generation of false-alarm under the high s/n ratio.Even there is very big carrier wave frequency deviation in authorized user, method of the present invention still can obtain higher detection probability and lower false alarm probability.

Claims (2)

1. cognitive OFDMA system carrier detection method of eliminating based on inter-carrier interference is characterized in that its step is as follows:

(a) cognitive user is utilized high conservative thresholding initial value With minimum living limit on duty at the gate initial value All carrier waves of not judging state are judged in advance energy is greater than the conservative thresholding initial value of height

Carrier State be judged as busyly, energy is less than the minimum living limit initial value of keeping goal

Carrier State be judged as the spare time, remaining Carrier State temporarily can't be judged;

(b) to not judging the carrier wave of state, start the inter-carrier interference elimination algorithm, determine whether interfering energy will be removed according to adjacent Carrier State from the carrier energy of current detection, and whether utilize thresholding λ ₁Carrier State to current detection is judged;

(c) all be judged as Carrier State, then carrier wave detect to finish, all do not judged as Carrier State, then according to the carrier set of not judging state the more conservative thresholding of new peak be λ ' _H, upgrade the minimum living λ ' that is limited on duty at the gate _L, change step (d) over to;

(d) utilize the conservative thresholding λ ' of the height that upgrades in the step (c) _HWith the minimum living of upgrading limit on duty at the gate λ ' _LThe carrier wave of not judging state is judged in advance energy is greater than the conservative thresholding λ ' of the height that upgrades _HCarrier State be judged as busyly, energy is less than the minimum living of the upgrading limit λ ' that keeps goal _LCarrier State be judged as the spare time, remaining Carrier State temporarily can't be judged, changes step (b) over to;

Cognitive user described in the step (a) is utilized high conservative thresholding initial value With minimum living limit on duty at the gate initial value

All carrier waves of not judging state are judged in advance energy is greater than the conservative thresholding initial value of height

Carrier State be judged as busyly, energy is less than the minimum living limit initial value of keeping goal

Carrier State be judged as the spare time, remaining Carrier State temporarily can't determining step be: utilize following formula to calculate the initial value of high conservative thresholding

Initial value with minimum living limit on duty at the gate

The initial value of high conservative thresholding

Wherein

The initial value that minimum living is kept goal and limit

Wherein

I is the carrier wave label in the formula, and N is the carrier wave number, Be cognitive user detected energy on i carrier wave, P _AVEBe the average energy of all carrier waves,

Expression is satisfied

The carrier wave number, utilize the conservative thresholding initial value of the height calculate

With minimum living limit on duty at the gate initial value

All carrier waves of not judging state are judged in advance energy is greater than the conservative thresholding initial value of height

Carrier State be judged as busyly, energy is less than the minimum living limit initial value of keeping goal

Carrier State be judged as the spare time, remaining Carrier State temporarily can't be judged;

Described in the step (b) to not judging the carrier wave of state, start inter-carrier interference elimination algorithm step and be:

The carrier wave of supposing current detection is i carrier wave, and the value of i satisfies 1≤i≤N,

Is 1) state of i-1 carrier wave of inspection busy? be not then to change step 2 over to), be that the energy that then upgrades i carrier wave is

Judge

Whether less than thresholding λ ₁Be, then judge i carrier wave for not busy, the judgement of current carrier wave finishes, and changes step 5) over to, and not, then the state of i carrier wave is still undetermined, changes step 2 over to), inter-carrier interference energy I _{K '}Calculated by following formula:

K ' is interfering carrier number in the formula, k '=i-1, Be cognitive user detected energy on the individual carrier wave of k ', ε _mBe the frequency deviation region of authorized user maximum, p (ε) is the frequency deviation probability density function of authorized user, thresholding λ ₁Can be calculated by following formula:

P in the formula _FaBe the false alarm probability binding occurrence of setting, N is sampling number, σ ²Be noise variance;

Is 2) state of i+1 carrier wave of inspection busy? be not, then change step 3) over to, be, the energy that then upgrades i carrier wave is

Judge

Whether less than thresholding λ ₁Be, then judge i carrier wave for not busy, the judgement of current carrier wave finishes, and changes step 5) over to, and not, then the state of i carrier wave is still undetermined, changes step 3) over to;

Is 3) state of i-2 carrier wave of inspection busy? be not, then change step 4) over to, be, the energy that then upgrades i carrier wave is

Judge

Whether less than thresholding λ ₁Be, then judge i carrier wave for not busy, the judgement of current carrier wave finishes, and changes step 5) over to, and not, then the state of i carrier wave is still undetermined, changes step 4) over to;

Is 4) state of i+2 carrier wave of inspection busy? be not, then change step 5) over to, be, the energy that then upgrades i carrier wave is

Judge

Whether less than thresholding λ ₁Be, then judge i carrier wave for not busy, the judgement of current carrier wave finishes, and changes step 5) over to, and not, then the state of i carrier wave is still undetermined, changes step 5) over to;

5) judge whether that all carrier waves of not judging state all traverse? be, then the epicycle algorithm finishes, and not, selects the next carrier wave of not judging state, changes step 1) over to,

If i=1, then the value of i-1 is got N, and the value of i-2 is got N-1, if i=2, then the value of i-2 is got N, if i=N-1, then the value of i+2 gets 1, if i=N, then the value of the i+1 value of getting 1, i+2 gets 2, and all the other situations are according to the result of calculation value.

2. a kind of cognitive OFDMA system carrier detection method of eliminating based on inter-carrier interference according to claim 1, it is characterized in that all not judged as Carrier State described in the step (c), then according to the carrier set of not judging the more conservative thresholding of new peak be λ ' _H, upgrade the minimum living λ ' that is limited on duty at the gate _LStep is:

According to the carrier set of not judging the more conservative thresholding of new peak be λ ' _HWith the renewal minimum living λ ' that is limited on duty at the gate _LFormula as follows:

The conservative thresholding of the height that upgrades

Wherein

The minimum living of upgrading is kept goal and is limit

Wherein

D represents the current carrier set of not judging, P in the formula _{AVE_D}Represent the current average energy of not judging carrier wave; Num (P _i＜P _{AVE_D}| i ∈ D) be illustrated in the carrier wave of not judging and satisfy carrier energy less than average value P A _{VE_D}The carrier wave number.

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