KR101039357B1 - Spectrum sesing apparatus and method using diversity combining in cognitive radio - Google Patents

Abstract

The present invention relates to a technique suitable for determining whether the licensed user occupies the spectrum by using a diversity technique using multiple antennas in a radio recognition system. This invention comprises: a licensed user station to which a signal of a licensed user is sent; And a non-licensed user system that senses the signal of the licensed user through multiple antennas and performs cooperative spectrum sensing to determine the presence or absence of the licensed user from the result of combining the sensing results. Therefore, the influence of multipath fading in real wireless communication is reduced, thereby improving the signal-to-noise ratio of the received signal, thereby improving the quality of spectrum sensing. In addition, by determining the presence or absence of the licensed user by applying the majority method, the reliability of the determination is improved.

Wireless Cognitive System, Diversity, Multiple Antenna, Licensed User, Unlicensed User

Description

SPECTRUM SESING APPARATUS AND METHOD USING DIVERSITY COMBINING IN COGNITIVE RADIO

The present invention relates to a spectrum sensing technology for detecting a licensed user in a wireless recognition system. In particular, the present invention relates to a diversity of a wireless recognition system suitable for determining whether a licensed user occupies the spectrum using a diversity technique using multiple antennas. The present invention relates to a spectrum sensing device and method used.

In a cognitive radio system, a cognitive radio uses the frequency band while the frequency band of the primary user (hereinafter referred to as "licensed user") is not used by the licensed user. Here, examples of the cognitive radio device may include a base station and a terminal. The wireless cognitive system is represented as a secondary user (hereinafter referred to as "unlicensed user") system.

Spectrum sensing technology in a cognitive radio system is a technique that examines the spectrum of a frequency band to see if a licensed user has appeared on that frequency channel while the cognitive radio is using the licensed user's frequency channel.

In general, a cognitive radio system should guarantee the vested interest in the licensee's use of the frequency channel as much as possible. This requires a spectral sensing technology that allows the cognitive radio to more accurately detect whether or not the licensee has appeared on that frequency channel. This is necessary.

In the conventional cognitive radio system, in order to improve the performance of spectrum sensing, cooperative spectrum sensing technology was used. This will be described with reference to FIG. 1.

The plurality of unlicensed user systems CR1-CR3 sense the signal of the licensed user from the licensed user station 11 and transmit it to the Fusion Center 12 through the control channel CH_CTL. At this time, the fusion center 12 determines whether the licensed user uses the frequency channel based on the spectrum of the licensed user received in a combined form from the unlicensed user system CR1-CR3 through the control channel CH_CTL. Judging whether or not.

When determining whether a licensed user exists from a plurality of combined results as described above, AND and OR methods are applied. Combining the individual sensing results to apply the AND method and the OR method is represented by Equation 1 below.

를 구하는 [수학식]이라 할 수 있다.As a result, Equation 1 takes the arithmetic mean of each individual sensing result in order to make a final determination of the existence of a licensed user, and thus the final spectrum detection value.

It can be said that [Equation] to obtain.

로 설정하는 것이 앤드AND) 방식이고

으로 설정하는 것이 오아(OR) 방식이다. 여기서,

은 개별 센싱 결과의 수 즉, 협력 스펙트럼 센싱에서는 비면허 사용자의 수이다.The calculated and displayed results are compared with the threshold value, and based on the comparison result, the presence or absence of a licensed user is determined.

Is set to AND)

Setting to is OR. here,

Is the number of individual sensing results, that is, the number of unlicensed users in cooperative spectrum sensing.

In the case of the AND method, it is determined that the licensed user exists only when the results of the individual sensing are all “1”, and the licensed user is determined not to exist in the spectrum when any of the individual sensing results is “0”. . In contrast, the Ora method determines that a licensed user exists if any one of the individual sensing results is "1".

As described above, in a conventional cognitive radio system, an unlicensed user system senses a signal of a licensed user from a licensed user station and transmits the signal to a convergence center through a control channel. The individual sensing results may change the amplitude and phase of the signal due to multipath fading occurring in the channel, thereby causing a problem of deterioration of the spectrum detection performance.

In addition, when judging the presence or absence of a licensed user, by applying an AND method or an OR method, an excessively precise or coarse sensing result is generated, thereby causing a problem of deterioration of reliability.

Accordingly, an object of the present invention is to determine whether a licensed user occupies the spectrum by using a diversity technique using multiple antennas.

Another object of the present invention is to determine whether a licensed user uses a corresponding frequency channel by applying a majority threshold when performing cooperative spectrum sensing.

The objects of the present invention are not limited to the above-mentioned objects. Other objects and advantages of the invention will be more clearly understood by the following description.

The present invention for achieving the above object,

A licensed user station to which a signal of a licensed user is sent;

And an unlicensed user system that senses the signal of the licensed user through multiple antennas and performs cooperative spectrum sensing to determine the presence or absence of the licensed user from the combined results of the sensing results. .

Preferably, the unlicensed user system determines whether a licensed user uses a corresponding frequency channel by applying a majority scheme when performing the role of cooperative spectrum sensing.

Another invention for achieving the above object is,

A first step of an unlicensed user system (radio recognition station) receiving a signal of a licensed user from a licensed user station via multiple antennas;

A second step of comparing each energy value of the signal of the licensed user received through each channel with a preset threshold value to obtain respective individual sensing values accordingly;

And a third process of adding all of the respective sensing values and comparing the resultant value with a majority threshold to obtain a final determination value.

According to the present invention, by applying a multi-antenna diversity technique in a wireless recognition system, the effect of multipath fading is reduced in actual wireless communication, thereby improving the signal-to-noise ratio of a received signal, thereby improving the performance of spectrum sensing.

In addition, by applying the majority method that reflects the majority of the individual sensing results sensed through the multiple antennas in the final decision, the presence or absence of the licensed user is determined, so that problems in the AND method or the OR method are compensated for and reliability is improved. It is effective.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 2 is a block diagram of a spectrum sensing device using diversity of a wireless recognition system according to the present invention. As shown therein, an unlicensed licensed user station 21 and a multi-antenna (ANT 1 to ANT M) are provided. It consists of a user system 22.

In the present invention, multiple antennas are applied to one unlicensed user system to perform cooperative spectrum sensing. That is, the unlicensed user system 22 corresponding to the unlicensed user station is provided with multiple antennas ANT 1 to ANT M, through which the signals of the licensed user are sensed from the licensed user station 21.

In addition, the unlicensed user system 22 does not transmit the spectrum of a licensed user received through the multiple antennas ANT 1 to ANT M to a fusion center as usual, but directly evaluates the corresponding frequency channel by itself. Determine whether to use.

By applying the multi-antenna diversity technique as described above, it combines the individual sensing results sensed by a number of unlicensed users to play the role of cooperative spectrum sensing to determine the existence or absence of a licensed user. The effects of fading are reduced to improve the signal-to-noise ratio of the received signal, which improves the performance of spectral sensing.

In addition, the unlicensed user system 22 directly evaluates the spectrum of the licensed user received through the multiple antennas ANT 1 to ANT M to determine whether to use a corresponding frequency channel, and applies a majority scheme. It was.

로 설정하는 방식이다. 여기서,

은 개별 센싱 결과의 수 즉, 비면허 사용자의 수이다.The majority method is a method of reflecting the result of the majority of individual sensing results sensed through the multiple antennas ANT 1 to ANT M in the final determination. That is, the arithmetic mean value is obtained by combining the individual sensing results sensed through the multiple antennas (ANT 1 to ANT M) as shown in [Equation 1], and the arithmetic mean value thus obtained is compared with a threshold to compare the result. On the basis of this, the existence of the licensed user is determined.

It is set as. here,

Is the number of individual sensing results, i.e. the number of unlicensed users.

By finally making a determination as to whether or not a licensed user is applied by applying the majority method, the problem in the normal AND method or the OR method is solved and the reliability is improved.

Meanwhile, a process of the spectrum sensing method according to the present invention will be described with reference to FIG. 3.

를 수신한다.(S1)First, the unlicensed user system 22 signals the licensed user from the licensed user station 21 via the multiple antennas ANT 1 to ANT M.

(S1)

의 에너지

를 기 설정된 임계값

와 비교하여 그에 따른 각각의 개별 센싱값

를 구한다.(S2,S3)Then, the licensed user's signal received through each corresponding channel of the multiple antennas (ANT 1 to ANT M)

Energy

Preset threshold

And each individual sensing value accordingly

(S2, S3)

가 상기 임계값

보다 크거나 같으면 상기 개별 센싱값

를 '1'로 출력하고, 작으면 '0'으로 출력하며, 나머지의 에너지

에 대해서도 동일한 방식으로 임계값

와 비교하여 그에 따른 각각의 개별 센싱값

를 출력한다.For example, the energy

Is above the threshold

Greater than or equal to the individual sensing value

Is output as '1', if it is small, it is output as '0' and the remaining energy

In the same way for the threshold

And each individual sensing value accordingly

.

를 모두 더하여(

)이 결과값을 본 발명에 따른 메이저러티 임계값

과 비교하여 최종 판정값

를 얻게 된다.(S4,S5)Subsequently, each individual sensing value

Plus all of

This result is the majority threshold according to the present invention.

Final judgment compared with

(S4, S5)

보다 크거나 같으면 상기 최종 판정값

를 '1'로 출력하고, 작으면 '0'으로 출력한다. 상기 최종 판정값

가 1이면 면허 사용자가 존재하는 것을 의미하고, 0이면 존재하지 않음을 의미한다.In this case, the result value is the majority threshold value.

Greater than or equal to the final determination value

Is printed as '1', and if it is small, it is printed as '0'. The final determination value

1 means that the licensee exists and 0 means that it does not exist.

  here,

,

,

,

,

은 헤비사이드 계단 함수,

Silverside staircase function,

,

,

의 관계가 성립한다.

The relationship is established.

4 and 5 show a performance comparison between conventional cooperative spectrum sensing according to signal-to-noise ratio and spectrum sensing using diversity of the present invention. However, it is assumed that the distance between licensed and unlicensed users in cooperative spectrum sensing and the distance between antennas applied to licensed and unlicensed users in spectrum sensing using diversity are equal.

FIG. 4 illustrates the AND method as the final decision method, and FIG. 5 illustrates the OR method as the final decision method. Here, "FC" means the detection probability of the cooperative spectrum sensing according to the prior art, and when compared with the detection probability of the spectrum sensing to which the antenna diversity of the present invention is applied, the detection probability of the spectrum sensing according to the present invention is It can be seen that it is higher than the detection probability of cooperative spectrum sensing.

Although the channel model is assumed to be AWGN (Additive White Gaussian Noise) in the cooperative spectrum sensing according to the prior art, the detection probability of the spectrum will be further reduced in the case of an actual wireless channel. Therefore, the spectrum sensing using the multi-antennas (ANT 1 to ANT M) proposed in the present invention is expected to exhibit much higher performance than the conventional cooperative spectrum sensing.

6 is a graph illustrating a detection probability (performance) according to the conventional AND / OR determination method according to the signal-to-noise ratio and the majority determination method of the present invention. As shown in the figure, it can be seen that the probabilities Pd_AND and Pd_OR of the conventional AND / or determination method show an excessively high detection probability or, on the contrary, an excessively low detection probability. On the other hand, it can be seen that the majority determination method Pd_MJR according to the present invention is reliable and reasonable.

FIG. 7 illustrates a detection probability when the majority determination method according to the present invention is applied to the signal-to-noise ratio for each number of the multiple antennas (ANT 1 to ANT M). That is, the experimental result of FIG. 7 shows detection probability according to the number of multiple antennas ANT 1 to ANT M in antenna diversity spectrum sensing to which a majority determination method is applied. According to the experimental results, when the number of antennas is 4 or more, similar detection probability is shown. This means that considering the complexity and performance of the system, it is inefficient to use four or more of the multiple antennas (ANT 1 to ANT M).

Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and may be implemented in various embodiments based on the basic concept of the present invention defined in the following claims. Such embodiments are also within the scope of the present invention.

1 is a schematic diagram of a conventional cognitive radio system.

2 is a schematic diagram of a wireless recognition system in accordance with the present invention.

3 is a flowchart of a spectrum sensing method using diversity of a radio recognition system according to the present invention;

4 and 5 are graphs showing performance comparison between conventional cooperative spectrum sensing according to signal-to-noise ratio and spectrum sensing using diversity of the present invention.

 FIG. 6 is a graph illustrating detection probabilities of the AND / OR determination method and the majority determination method according to the signal-to-noise ratio; FIG.

7 is a graph showing the detection probability when the majority determination method according to the present invention is applied to the signal-to-noise ratio for each number of multiple antennas.

*** Description of the symbols for the main parts of the drawings ***

21: Licensed User Station

22: Unlicensed User System

Claims (7)

A licensed user station to which a signal of a licensed user is sent; Sensing the licensed user's signal through multiple antennas, and acting as cooperative spectrum sensing to determine the presence or absence of a licensed user from the result of combining the sensing results, and performing the role of cooperative spectrum sensing. And an unlicensed user system that determines whether the licensed user uses the corresponding frequency channel by applying the determination method. The majority determination method is a spectrum sensing device using diversity of a radio recognition system, characterized in that the majority of the results of the individual sensing sensed through the multiple antennas. delete delete The spectrum sensing device using diversity of a radio recognition system according to claim 1, wherein the number of multiple antennas is four. A first step of the unlicensed user system receiving a signal of a licensed user from a licensed user station via multiple antennas; A second step of comparing each energy value of the signal of the licensed user received through each channel with a preset threshold value to obtain respective individual sensing values accordingly; By adding all of the individual sensing values and comparing the result with the majority threshold, a final judgment is obtained. If the result is greater than or equal to the majority threshold, it is determined that a licensed user exists. And a third process of determining that there is no licensed user. The method of claim 5, wherein the second process outputs an individual sensing value as '1' when the energy of the licensed user's signal is greater than or equal to a preset threshold, and outputs as '0' when the energy of the licensed user is less than or equal to a preset threshold. Spectrum sensing method using diversity of cognitive system. delete

Images