CN102710349B - Data selection-based frequency spectrum sensing method used under pulse interference environment - Google Patents

Abstract

The invention discloses a data selection-based frequency spectrum sensing method used under a pulse interference environment, which comprises the steps as follows: firstly, an antenna in a cognitive radio system repeatedly executes time-domain sampling aiming at a signal in a monitoring channel; secondly, an absolute value discrete value of the signal of each time domain sampling point is computed, and each discrete value in a first absolute value discrete value sequence formed by all discrete values is compared with the average value of all the discrete values, when two or more than two continuous discrete values in the first absolute value discrete value sequence are large than the average value of the discrete values by three times, and the discrete values with interference pulse are removed; thirdly, the inspection statistical quantity of a second absolute value discrete value sequence formed by all discrete values without pulse interference is computed; and lastly, the sizes of the inspection statistical quantity and a decision threshold are compared, and whether the monitoring channel is idle or not is judged according to a comparison result. The method disclosed by the invention effectively solves a problem that the false alarm probability is increased owing to existing pulse interference, and improves the utilization ratio of frequency spectrum resources.

Description

The frequency spectrum sensing method of selecting based on data under a kind of impulse disturbances environment

Technical field

The present invention relates to the frequency spectrum perception technology in a kind of cognitive radio system, especially relate to the frequency spectrum sensing method of selecting based on data under a kind of impulse disturbances environment.

Background technology

Along with the appearance of increasing radio communication service, there is situation more and more in short supply in limited frequency spectrum resource.And in practice, the physics frequency spectrum resource that is assigned in a large number specific communication service on much time, space in idle condition, this shows that it is not to be lacked and caused by physics frequency spectrum resource that present frequency spectrum resource lacks phenomenon, but because fixing frequency spectrum resource distribution policy causes.The proposition of cognitive radio provides a feasible thinking for improving the availability of frequency spectrum, effectively utilize the mandate frequency range in idle condition, but before the mandate frequency range of utilizing these in idle condition, which must first effectively detect and authorize frequency range to occur idle condition, therefore frequency spectrum perception is one of key technology in cognitive radio.

Existing frequency spectrum sensing method has energy measuring method, covariance matrix detection method, feature detection method etc., these frequency spectrum sensing methods are all to consider under stationary noise environment, directly utilizes all sampled datas to carry out frequency spectrum detection.But when in the situation of the impulse disturbances that exists thunder and lightning, automobile sparking etc. to cause, the false alarm probability of existing frequency spectrum sensing method can sharply increase, and then makes frequency spectrum resource utilization rate seriously low.

Summary of the invention

Technical problem to be solved by this invention is to provide the frequency spectrum sensing method of selecting based on data under a kind of impulse disturbances environment, and it can effectively be reduced in the false alarm probability under impulse disturbances environment, improves frequency spectrum resource utilization rate.

The present invention solves the problems of the technologies described above adopted technical scheme: the frequency spectrum sensing method of selecting based on data under a kind of impulse disturbances environment, is characterized in that comprising the following steps: first the antenna in cognitive radio system carries out repeatedly to the signal in supervisory channel the time-domain sampling signal that signal that time-domain sampling obtains being put by multiple time-domain samplings forms; Then calculate the absolute value centrifugal pump of the signal of each time-domain sampling point, and the size of the mean value of the absolute value centrifugal pump of the signal of each absolute value centrifugal pump in the first absolute value centrifugal pump sequence of forming of the absolute value centrifugal pump of the signal of relatively being put by all time-domain samplings and all time-domain sampling points, in the time that being greater than 3 times of the mean value of the absolute value centrifugal pump of the signal of all time-domain sampling points, continuous two and above absolute value centrifugal pump in the first absolute value centrifugal pump sequence reject these and exist the absolute value centrifugal pump of impulse disturbances; Then calculate the test statistics that does not have the second absolute value centrifugal pump sequence that the absolute value centrifugal pump of impulse disturbances forms by all; The size of last comparing check statistic and decision threshold, judges that according to comparative result whether this supervisory channel is in idle condition.

It comprises following concrete steps:

1. the antenna in cognitive radio system carries out time-domain sampling K time to the signal in supervisory channel, obtains the time-domain sampling signal that is made up of the signal of K time-domain sampling point, the signal of k time-domain sampling point is designated as to x (k), wherein k ∈ [1, K];

2. the signal of each time-domain sampling point in time-domain sampling signal is asked respectively to absolute value operation, obtain the absolute value centrifugal pump of the signal of the each time-domain sampling point in time-domain sampling signal, the absolute value centrifugal pump of the signal x (k) of k time-domain sampling point is designated as to y (k), y (k)=| x (k) |, wherein, symbol " || " is modulo operation symbol;

3. the mean value that calculates the absolute value centrifugal pump of the signal of all time-domain sampling points in time-domain sampling signal, is designated as m _y, $m_y=\frac{1}{K}\underset{k=1}{\overset{K}{\mathrm{\Σ}}}y\left(k\right);$

4. the absolute value centrifugal pump of the signal of all time-domain sampling points is formed to a first absolute value centrifugal pump sequence, then compare each absolute value centrifugal pump and the m in the first absolute value centrifugal pump sequence _ysize, if continuous two and above absolute value centrifugal pump are all greater than m in the first absolute value centrifugal pump sequence _y3 times, judge in these absolute value centrifugal pumps and have impulse disturbances, and reject these and have the absolute value centrifugal pump of impulse disturbances, if do not exist continuous two and above absolute value centrifugal pump to be all greater than m in the first absolute value centrifugal pump sequence _y3 times, judge that all absolute value centrifugal pumps in the first absolute value centrifugal pump sequence all do not exist impulse disturbances;

5. calculate the test statistics that does not have the second absolute value centrifugal pump sequence that the absolute value centrifugal pump of impulse disturbances forms by all, be designated as T, wherein, n ∈ [1, N], N represents the number of the absolute value centrifugal pump in the second absolute value centrifugal pump sequence, and z (n) represents n absolute value centrifugal pump in the second absolute value centrifugal pump sequence, and symbol " || " is modulo operation symbol;

6. according to false alarm probability P _fcalculate decision threshold, be designated as λ _t, wherein, σ ²represent the power of noise, Q ^-1(P _f) expression Q (P _f) counter-transformation function, Q (P _f) be the tail area function of standardized normal distribution probability density, t is calculus variable;

7. comparing check statistic T and decision threshold λ _tsize, if T>=λ _t, judge that this supervisory channel is in busy condition, if T< is λ _t, judge that this supervisory channel is in idle condition.

Compared with prior art, the invention has the advantages that the comparison by utilizing time-domain sampling signal amplitude, there is the sampled point of impulse disturbances in rejecting, then utilize remaining sampled point, by judging that whether supervisory channel that the size of inspection statistics value and decision threshold judges the current perception cycle is in idle condition, realize frequency spectrum perception, the inventive method has effectively overcome the existing frequency spectrum sensing method problem that false alarm probability increases in the time there is impulse disturbances, thereby has improved frequency spectrum resource utilization rate.

Brief description of the drawings

Fig. 1 is the FB(flow block) of frequency spectrum sensing method of the present invention;

Fig. 2 is under different impulse disturbances and noise power ratio, the comparison schematic diagram of the false alarm probability of existing energy measuring method and the inventive method.

Embodiment

Below in conjunction with accompanying drawing, embodiment is described in further detail the present invention.

The frequency spectrum sensing method of selecting based on data under a kind of impulse disturbances environment that the present invention proposes, its FB(flow block) as shown in Figure 1.It comprises the following steps: first the antenna in cognitive radio system carries out repeatedly to the signal in supervisory channel the time-domain sampling signal that signal that time-domain sampling obtains being put by multiple time-domain samplings forms; Then calculate the absolute value centrifugal pump of the signal of each time-domain sampling point, and the size of the mean value of the absolute value centrifugal pump of the signal of each absolute value centrifugal pump in the first absolute value centrifugal pump sequence of forming of the absolute value centrifugal pump of the signal of relatively being put by all time-domain samplings and all time-domain sampling points, in the time that being greater than 3 times of the mean value of the absolute value centrifugal pump of the signal of all time-domain sampling points, continuous two and above absolute value centrifugal pump in the first absolute value centrifugal pump sequence reject these and exist the absolute value centrifugal pump of impulse disturbances; Then calculate the test statistics that does not have the second absolute value centrifugal pump sequence that the absolute value centrifugal pump of impulse disturbances forms by all; The size of last comparing check statistic and decision threshold, judges that according to comparative result whether this supervisory channel is in idle condition.Specifically comprise following concrete steps:

1. the antenna in cognitive radio system carries out time-domain sampling K time to the signal in supervisory channel, obtains the time-domain sampling signal that is made up of the signal of K time-domain sampling point, the signal of k time-domain sampling point is designated as to x (k), wherein k ∈ [1, K].In actual mechanical process, generally the signal in supervisory channel is carried out to minimum hundreds of time time-domain sampling.

2. the signal of each time-domain sampling point in time-domain sampling signal is asked respectively to absolute value operation, obtain the absolute value centrifugal pump of the signal of the each time-domain sampling point in time-domain sampling signal, the absolute value centrifugal pump of the signal x (k) of k time-domain sampling point is designated as to y (k), y (k)=| x (k) |, wherein, symbol " || " is modulo operation symbol.

3. the mean value that calculates the absolute value centrifugal pump of the signal of all time-domain sampling points in time-domain sampling signal, is designated as m _y, $m_y=\frac{1}{K}\underset{k=1}{\overset{K}{\mathrm{\&Sigma;}}}y\left(k\right).$

4. the absolute value centrifugal pump of the signal of all time-domain sampling points is formed to a first absolute value centrifugal pump sequence, then compare each absolute value centrifugal pump and the m in the first absolute value centrifugal pump sequence _ysize, if continuous two and above absolute value centrifugal pump are all greater than m in the first absolute value centrifugal pump sequence _y3 times, judge in these absolute value centrifugal pumps and have impulse disturbances, and reject these and have the absolute value centrifugal pump of impulse disturbances, if do not exist continuous two and above absolute value centrifugal pump to be all greater than m in the first absolute value centrifugal pump sequence _y3 times, judge that all absolute value centrifugal pumps in the first absolute value centrifugal pump sequence all do not exist impulse disturbances.

5. calculate the test statistics that does not have the second absolute value centrifugal pump sequence that the absolute value centrifugal pump of impulse disturbances forms by all, be designated as T, wherein, n ∈ [1, N], N represents the number of the absolute value centrifugal pump in the second absolute value centrifugal pump sequence, and z (n) represents n absolute value centrifugal pump in the second absolute value centrifugal pump sequence, and symbol " || " is modulo operation symbol.At this, the the second absolute value centrifugal pump sequence forming comprises two kinds of situations, the first situation is to reject and have the new absolute value centrifugal pump sequence forming after the absolute value centrifugal pump of impulse disturbances in the first absolute value centrifugal pump sequence, and the number of the absolute value centrifugal pump comprising in this new absolute value centrifugal pump sequence is less than the number of the absolute value centrifugal pump comprising in the first absolute value centrifugal pump sequence; The second situation is that the absolute value centrifugal pump comprising in the second absolute value centrifugal pump sequence is original absolute value centrifugal pump in the first absolute value centrifugal pump sequence without any absolute value centrifugal pump of rejecting in the first absolute value centrifugal pump sequence.

6. according to false alarm probability P _fcalculate decision threshold, be designated as λ _t, wherein, σ ²represent the power of noise, Q ^-1(P _f) expression Q (P _f) counter-transformation function, Q (P _f) be the tail area function of standardized normal distribution probability density, t is calculus variable.

7. comparing check statistic T and decision threshold λ _tsize, if T>=λ _t, judge that this supervisory channel is in busy condition, if T< is λ _t, judge that this supervisory channel is in idle condition.

By following emulation to further illustrate feasibility and the validity of frequency spectrum sensing method of the present invention.

Suppose the signal time-domain sampling number of times K=1000 in each perception cycle of cognitive radio system, wherein in the signal of 30 continuous sampling points, have impulsive noise, default false alarm probability is P _f=0.1.Fig. 2 has provided under different impulse disturbances and noise power ratio, and existing energy measuring method and the inventive method are by the comparison of the false alarm probability of 10000 Monte Carlo simulation acquisitions.As can be seen from Figure 2, when impulse disturbances and noise power are when lower, existing energy measuring method can realize default false alarm probability, and along with the increase of impulse disturbances power, it departs from default false alarm probability can become large gradually, even reach 1, and the inventive method can make the false alarm probability of emulation maintain all the time near default false alarm probability.

Claims (1)

1. a frequency spectrum sensing method of selecting based on data under impulse disturbances environment, is characterized in that comprising the following steps:

1. the antenna in cognitive radio system carries out time-domain sampling K time to the signal in supervisory channel, obtains the time-domain sampling signal that is made up of the signal of K time-domain sampling point, the signal of k time-domain sampling point is designated as to x (k), wherein k ∈ [1, K];

2. calculate the absolute value centrifugal pump of the signal of each time-domain sampling point, the signal of each time-domain sampling point in time-domain sampling signal is asked respectively to absolute value operation, obtain the absolute value centrifugal pump of the signal of the each time-domain sampling point in time-domain sampling signal, the absolute value centrifugal pump of the signal x (k) of k time-domain sampling point is designated as to y (k), y (k)=| x (k) |, wherein, symbol " || " is modulo operation symbol;

3. the mean value that calculates the absolute value centrifugal pump of the signal of all time-domain sampling points in time-domain sampling signal, is designated as m _y, $m_y=\frac{1}{K}\underset{k=1}{\overset{K}{\mathrm{\&Sigma;}}}y\left(k\right);$

Each absolute value centrifugal pump and m in the first absolute value centrifugal pump sequence that the absolute value centrifugal pump of the signal of 4. relatively being put by all time-domain samplings forms _ysize, if continuous two and above absolute value centrifugal pump are all greater than m in the first absolute value centrifugal pump sequence _y3 times, judge in these absolute value centrifugal pumps and have impulse disturbances, and reject these and have the absolute value centrifugal pump of impulse disturbances, if do not exist continuous two and above absolute value centrifugal pump to be all greater than m in the first absolute value centrifugal pump sequence _y3 times, judge that all absolute value centrifugal pumps in the first absolute value centrifugal pump sequence all do not exist impulse disturbances;

5. calculate the test statistics that does not have the second absolute value centrifugal pump sequence that the absolute value centrifugal pump of impulse disturbances forms by all, be designated as T, wherein, n ∈ [1, N], N represents the number of the absolute value centrifugal pump in the second absolute value centrifugal pump sequence, and z (n) represents n absolute value centrifugal pump in the second absolute value centrifugal pump sequence, and symbol " || " is modulo operation symbol;

6. according to false alarm probability P _fcalculate decision threshold, be designated as λ _t, wherein, σ ²represent the power of noise, Q ^-1(P _f) expression Q (P _f) counter-transformation function, Q (P _f) be the tail area function of standardized normal distribution probability density, t is calculus variable;

7. comparing check statistic T and decision threshold λ _tsize, judge that according to comparative result whether this supervisory channel is in idle condition, if i.e.: T>=λ _t, judge that this supervisory channel is in busy condition, if T< is λ _t, judge that this supervisory channel is in idle condition.