KR101087287B1 - Method for primary user detecting in a cognitive radio systems - Google Patents

Abstract

A user detection method is disclosed in a Cognitive Radio (CR) system in which a primary user (PU) can be detected without a Quiet Period (QP).

In the disclosed wireless cognitive system, first, a user detection method includes removing a pilot signal already known by a wireless cognitive user (receiver or detector) from a signal received through a pilot channel in a wireless cognitive system, and receiving the received signal after removing the pilot signal. By detecting the presence of a user without a separate idle period based on the strength of the user, it is possible to accurately detect the first user without a idle period, thereby increasing the channel usage efficiency.

Wireless Cognitive System, Non-Pause Period, Preferred User, Preferred User Detection, Pilot

Description

Method for primary user detecting in a cognitive radio systems

The present invention relates to primary user (PU) detection in a cognitive radio (CR) system, and more particularly, a wireless cognitive system that enables the detection of a primary user without a quiet period (QP). First of all, the present invention relates to a user detection method.

In general, in the ubiquitous era using ubiquitous sensor network (USN: Ubiquitous Sensor Network), telematics, home network, etc. as well as mobile communication and digital multimedia broadcasting (DMB), radio waves are used ubiquitous, which is a finite resource. Changes in the use of radio waves are required. Therefore, research has been conducted on a new concept system of flexible use as a method of increasing the efficiency of propagation used exclusively. J.Mitola proposed a wireless recognition (CR) concept that can detect frequencies that are allocated but are not actually used and are vacant and can be effectively shared.

In other words, a radio aware (CR) system is intended to use spectrum bands that were originally assigned to authorized preferred users (PUs) but are not used at a particular time and location. First, when the user is newly activated, the radio recognition system must shift the spectrum band. Therefore, detecting the presence of a user is one of the most important tasks in a wireless recognition system.

In order to detect a user first without interference from the radio aware users themselves, the radio aware system typically has a period of idleness (QP) in which not all radio aware users access the channel. However, using the idle period reduces the channel utilization of the wireless recognition system and worsens the quality of service (QoS) of the wireless recognition users.

In order to overcome this difficulty, the preferred user detection method without a rest period has recently been SSJeong, WSJeon, and DGJeong, "Dynamic channel sensing management for OFDMA-based cognitive radio systems," in Proc.IEEE VTC 2007-Spring, Dublin, Ireland, Apt. 2007. and S.S.Jeong, W.S.Jeon, and D.G.Jeong, "Nonquiet primary user detection for OFDMA-based cognitive radio systems," IEEE Trans. Proposed in Wireless Commun, in revision, 2008. This is a non-pause period first user detection scheme for a wireless recognition system based on Orthogonal Frequency Division Multiple Access (OFDMA), which detects a user first by using subcarriers utilized for data transmission by wireless aware users.

This method can improve the performance of both the radio recognition system and the preferred user, but only considers the data subcarrier and does not use the pilot subcarrier for user detection.

As another approach, D. Chen, J. Li, and J. Ma, "In-band sensing without quite period in cognitive radio," in Proc. In IEEE WCNC 2008, Las Vegas, USA, Apr, 2008, a preferred user detection scheme using a complementary symbol couple (CSC) in a pilot signal has been proposed. When the sum of two adjacent pilot symbols of the radio recognition system is zero, the compensation condition is satisfied. If two OFDM symbols satisfying the compensation conditions are added, the pilot interference will be zero while the noise and preferred user signal will still remain. As a result, user detection without a rest period can simply be achieved. However, its detection performance is very limited because only some pilot symbols satisfy the compensation conditions.

Accordingly, the present invention has been proposed to solve various problems arising from various methods proposed for user detection in the conventional radio recognition system as described above.

An object of the present invention is to provide a first user detection method in a wireless cognitive system capable of first detecting a user without a Quiet Period (QP).

Another object of the present invention is to provide a preferred user detection method in a radio recognition system capable of increasing channel utilization by providing a priority user detection method without a rest period based on pilot cancellation.

According to the present invention for solving the above problems, "a method of detecting a user first in a wireless recognition system",

In a method of detecting a user first, the wireless recognition users (recipients) in the wireless recognition system,

Removing a pilot signal that is already known from a signal received through a pilot channel, and detecting a presence of a preferred user without a rest period based on the strength of the received signal after removing the pilot signal; .

Priority user detection process according to the present invention,

A sampling step of collecting received signal samples;

Calculating a channel coefficient using the received signal sample and a known pilot sequence;

Pilot canceling the pilot interference from the received signal sample;

And performing a statistic of the received signal sample from which the pilot interference has been removed, and comparing the statistic with a reference value set for determining the presence of the user first.

According to the present invention, since the user detection is possible based on pilot elimination and without a rest period, there is an advantage of increasing channel utilization.

Hereinafter, described in detail with reference to the accompanying drawings a preferred embodiment of the present invention. In the following description, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail.

The present invention contemplates that the information content of the pilot signal is preferentially known to all other radio aware users in the system, so that receiver (ie, detector) radio aware users can easily remove it from the received signal. If, after pilot cancellation, a pilot signal is transmitted over a particular channel (s) (eg, pilot subcarriers in OFDM systems) and radio-aware users confirm the presence of the user in the channel (s) first, the dormant period Priority user detection without this can be performed. Although the proposed concept can be applied to any system using a pilot signal on a specific channel, for convenience of description, the present invention only considers an OFDMA based radio recognition system such as IEEE 802.22 in which some subcarriers are assigned to a pilot signal. In contrast to the conventional scheme, firstly, all OFDM symbols of pilot subcarriers for user detection can be used, so that radio-aware users can achieve better performance in the proposed scheme, which will be described in more detail below. Explain.

First, prior to describing the present invention, a general OFDMA-based wireless recognition system is as follows.

The spectral band of the radio recognition system is divided into multiple subcarriers which are equally spaced apart. Of these, the M subcarriers are used to transmit pilot sequences known to all radio aware users. Pilot signals are commonly used for channel estimation and synchronization. The present invention can be applied to both systems having a single radio aware transmitter (eg, downlink of a radio aware cell) and systems having multiple radio aware transmitters (eg, uplink of a radio aware cell). In the former case, a single radio aware transmitter uses all pilot subcarriers, and in the latter case pilot subcarriers can be distributed among multiple radio aware transmitters.

Define a time unit "frame" that is L times the OFDM symbol period. For the pilot signal, the entirety of the M × L OFDM symbols is transmitted in one frame. It is assumed that the length of the frame is determined according to the channel synchronization time. Thus, the channel state from the radio aware transmitter does not change during the frame period. In addition, in the case of multiple radio aware transmitters, it is assumed that each pilot subcarrier is assigned to a specific radio aware transmitter for the entire frame. The frame is first a basic time unit of user detection.

를 프레임 내의 m번째 상관기의 OFDM 심벌 l(1≤l≤L)로 나타낸다. T_O가 OFDM 심벌 기간들이면,

는 아래의 [수식 1]이 된다.Since there are in-phase and quadrature branches for each pilot subcarrier, 2M correlators are needed for the radio aware receiver to extract all pilot components. Correlators are indexed as 1, ..., M for in-phase components and M + 1, ..., 2M for square components, respectively. Let t be the time index defined for the frame. And

Denotes the OFDM symbol l (1 ≦ l ≦ L) of the m th correlator in the frame. If T _O is OFDM symbol periods,

Becomes Equation 1 below.

이며

는 무선 인지 시스템의 중심 주파수이다. 파일럿 신호가 매우 중요한 제어신호이므로, 일반적으로 이진 위상 편이 변조(BPSK)와 같은 잡음에 매우 강한 변조 기술이 실제 파일럿 신호를 전송하는데 사용된다. BPSK 변조된 파일럿 신호가 제안된 방식을 설명하는 것으로 가정한다. 또한, 무선 인지 시스템의 모든 사용자들은 동기되는 것으로 가정한다.here,

And

Is the center frequency of the radio recognition system. Since the pilot signal is a very important control signal, a modulation technique that is very resistant to noise, such as binary phase shift modulation (BPSK), is typically used to transmit the actual pilot signal. Assume that the BPSK modulated pilot signal describes the proposed scheme. In addition, it is assumed that all users of the radio recognition system are synchronized.

We denote r (t) as a signal received by the radio aware user, and first there may be assumptions for the next two pilot subcarriers depending on whether or not a user (PU) signal is present.

: r(t) = i(t) + n(t) + s(t);(1) first assume the presence of a user (PU),

r (t) = i (t) + n (t) + s (t);

: r(t) = i(t) + n(t).(2) first assume the absence of a user (PU),

r (t) = i (t) + n (t).

의 양면 스펙트럼 밀도를 가지는 백색 가우스 잡음이라고 가정한다. 비-휴지기간 우선 사용자 검출을 하므로, 휴지기간을 가지는 경우와 반대로 의사결정을 위한 수신된 신호가 파일럿 신호를 포함한다는 것에 주목해야 한다.Where i (t), n (t) and s (t) are pilot signals, noise and preferred user signals, respectively. n (t) is

Suppose it is a white Gaussian noise with a double-sided spectral density of. It is to be noted that since the non-pause period first user detection is performed, the received signal for decision making includes a pilot signal as opposed to having a dormant period.

In the present invention, a radio-aware user performing first user detection first separates the pilot signal from the signal received on pilot subcarriers (i.e., i (t) is removed from r (t)), and first of all for the presence of the user. Make a decision. This procedure consists of four steps as shown in FIG. 1 for each frame.

First, as the sampling step S10, the radio aware user (receiver) collects signal samples (ie, correlator output) received during the frame period.

Secondly, in the channel estimation step S20, at the end of the frame, the radio aware user calculates channel coefficients from the transmitter radio aware user using the received signal samples and the pilot sequences that are already known.

Third, as a pilot cancellation step (S30), the radio aware user removes the pilot interference from the received signal sample.

Fourth, as a decision step (S40), the wireless cognitive user generates test statistics, and first compares the reference values calculated by the experiment in advance to determine the existence of the user, and as a result determines the existence of the user first. do.

Here, it should be noted that the first two steps S10 and S20 are normal operation in a system using a pilot signal. The final step S40 is necessary for any preferred user detection scheme. However, the third step (S30) is additionally required to implement the method proposed in the present invention with low complexity, as described in detail later.

이 OFDM 심벌 l(l≤l≤L)에서 m번째 상관기(1≤m≤2M)로부터의 신호 샘플로 표기된다면, 아래와 같은 [수식 2]이 성립한다.In more detail, the received signal passes through the correlator to generate a signal sample (S10). As already explained, user detection is first performed at the end of a frame containing L OFDM symbols indexed 1, 2, ..., L.

If this is denoted by the signal sample from the mth correlator (1 ≦ m ≦ 2M) in the OFDM symbol l (l ≦ l ≦ L), the following equation (2) holds.

은 수신된 파일럿 심벌의 동상 또는 사각 성분이다.

하에서

,

하에서

이다.

은

의 편차를 가지는 0의 평균 가우시안 랜덤 변수이고,

은 우선 사용자 신호의 샘플값이다.

의 통계적 성질은 우선 사용자 신호의 심벌 기간, 정보 비트 시퀀스 및 변조 형태에 좌우된다.here,

Is the in-phase or square component of the received pilot symbol.

Under

,

Under

to be.

silver

Is an average Gaussian random variable of 0 with a deviation of

Is a sample value of the user signal first.

The statistical nature of the first depends on the symbol period, information bit sequence and modulation form of the user signal.

로 표현될 수 있고, 여기서

은 프레임 기간 동안의 상수인 채널 계수이고,

은 무선 인지 사용자에게 알려진 파일럿 시퀀스와 전송 진폭 양자에 의해 제공된 결정적인 양이다. 파일럿 신호의 동상 성분의 위상 편이 버전만이 본 발명에서 가정한 BPSK 변조를 가지는 사각 분기에서 수신되므로, M+1≤M≤2M에 대하여

임을 주의해야 한다.For the wireless cognitive user, Equation 2 is

Can be expressed as

Is the channel coefficient, which is a constant for the frame period,

Is the critical amount provided by both the pilot sequence and the transmission amplitude known to the radio aware user. Since only the phase shifted version of the in-phase component of the pilot signal is received in the quadrature branch with the BPSK modulation assumed in the present invention, for M + 1 ≦ M ≦ 2M

Care should be taken.

을 채널 계수의 추정으로 나타낼 수 있다면,

이 된다. 그러면,

이 된다. 만일, 우선 사용자 신호도 노이즈도 없다면, 완전한 채널 추정이 달성될 수 있다(즉, 1≤l≤에 대하여

).The radio-aware user calculates the channel coefficient by applying the least square channel estimation technique to the received signal samples (S20).

If can be expressed as an estimate of the channel coefficients,

Becomes then,

Becomes If there is no user signal and no noise first, then full channel estimation can be achieved (i.e. for 1 < l <

).

의 불확실성을 가지게 된다. 다중 샘플에 대한 최소제곱 추정이 샘플 평균 추정기이므로, 프레임에 대한 채널 계수의 추정은, 아래의 [수식 3]이 된다.However, first of all, due to the influence of user signal and noise, channel coefficient estimation

There is an uncertainty of. Since the least squares estimation for the multiple samples is a sample average estimator, the estimation of the channel coefficients for the frame is given by Equation 3 below.

을 OFDM 심벌l의 m번째 상관기 출력에 대한 제거 결과로 나타내면 아래의 [수식 4]와 같이 표현할 수 있다.After channel estimation, pilot cancellation is performed on each received signal sample (S30).

Denotes the removal result of the mth correlator output of OFDM symbol l, can be expressed as Equation 4 below.

Here, the last term in [Equation 4] represents the residual pilot rejection error.

Finally, "test statistics" corresponding to the energy received during the frame period are generated using the removal results. That is, the test statistic is the sum of squares of 2ML removal results, as shown in Equation 5 below.

이면, 무선 인지 사용자는 우선 사용자가 존재한다고 결정한다. 이와는 달리

가 아닐 경우, 무선 인지 사용자는 스펙트럼 대역이 비었다고 간주한다(S40).The resulting test statistics are then compared to the reference value [epsilon]. if

, The radio aware user first determines that the user exists. Unlike this

If not, the radio-aware user considers that the spectrum band is empty (S40).

인 경우 발생하고, 오검출은 우선 사용자가 실제로 존재하지만

인 경우이다. 이러한 검출 오류는 무선 인지 시스템과 우선 사용자의 성능을 저하시키고 결정 기준치에 매우 민감하다.There may be two forms of detection error, referred to herein as "failure alarm" and "false detection". Failed alarms will not be activated first

Occurs, and false detection first occurs when the user actually exists.

If This detection error degrades the performance of the wireless recognition system and the user first and is very sensitive to decision criteria.

The present invention described above may be applied to a radio recognition system using a frame preamble. Frame preambles containing sequences known to the receiver are utilized for synchronization and original channel estimation as the pilot does. Since there is no conceptual difference between preferred user detection with preamble removal and preferred user detection with pilot removal, the detailed procedure thereof is omitted.

On the other hand, the proposed invention can be easily adopted for sequential and cooperative detection structures. That is, if the radio recognition system has multiple test statistics generated during multiple frame periods and / or generated by multiple radio recognition users, the radio recognition system may combine them by using an appropriate combining technique. In this case, the detection performance can be improved as the number of combined test statistics increases. In order to focus on the core subjects (ie, non-pause detection using pilot removal) within the limited space of the present invention, the application of the proposed scheme to sequential and collaborative detection is not addressed.

When analyzing the performance of the user detection method without the idle period according to the present invention. To simplify the analysis, the following two assumptions are adopted.

은

의 편차를 가지는 영 평균 가우시안 랜덤 변수이다. 더욱이, 우선 사용자 신호 샘플은 서로에 독립적이다.First, user signal sample

silver

A zero mean Gaussian random variable with a deviation of. Moreover, firstly user signal samples are independent of each other.

Second, pilot subcarriers always transmit information bit "1".

이다.These assumptions are generally not made in practice. Nevertheless, the calculation results of this analysis are consistent with the simulation results that can be obtained without these assumptions, as shown below in showing the practical utility of the analysis. First, the user signal-to-noise ratio (SNR) is defined as the ratio of signal power and noise power received from the user. In other words, the first user SNR is

to be.

In the above assumption, it can be expressed as the following Equation 6.

을 고려한다. 그러면

은

의 편차를 가지는 영 평균 가우시안 랜덤 변수이다. 따라서,

은 L 자유도를 가지는 중심 카이자승분포를 따르고,

은 하나의 자유도를 가지는 중심 카이자승 랜덤 변수이다.First, the hypothesis

Consider. then

silver

A zero mean Gaussian random variable with a deviation of. therefore,

Follows the central chi-square distribution with L degrees of freedom,

Is a central chi-square random variable with one degree of freedom.

이라 하자. 그리고,

를 각각 가설

하에서의 랜덤 변수 X의 평균과 분산으로 나타낸다고 하자. 그러면 아래의 [수식 7] 및 [수식 8]과 같이 표현할 수 있다.

Let's say And,

Each hypothesis

Suppose it is represented by the mean and variance of the random variable X below. Then, it can be expressed as Equation 7 and Equation 8 below.

의 네 번째 모멘트가

이라는 사실을 이용하여,

을 용이하게 검증할 수 있다. 따라서

이다.

The fourth moment of

Using the fact that

Can be easily verified. therefore

to be.

에 의하여,

이 된다. 결국, Δ은 독립적이고 동일하게 분포되는 랜덤 변수들의 합으로 볼 수 있게 된다. 2M이 큰 수이면, 중심 한정정리에 따라 아래의 [수식 9]로 표현할 수 있다.Δ and

By

Becomes As a result, Δ can be viewed as the sum of independent and identically distributed random variables. If 2M is a large number, it can be expressed by the following [Equation 9] according to the central limit theorem.

이

의 평균과

의 분산을 가지는 가우시안 분포를 나타내고, "~"은 "처럼 분포된다"를 의미한다. 이와 유사한 절차(procedure)에서, H₀하에서의 테스트 통계의 분포는 아래의 [수식 10]과 같이 유도될 수 있다.

this

With the average of

Represents a Gaussian distribution having a variance of "," In a similar procedure, the distribution of test statistics under H ₀ can be derived as shown in Equation 10 below.

를 우선 사용자 검출이 단 한 번만 실행될 때(즉, 우선 사용자 존재에 대한 한 번의 결정)의 실패 알람과 오검출 확률로 각각 나타내자. 현존하는 대부분의 연구들은 이러한 성능 측정에만 초점을 맞추고 있다. 하지만, 실제 더 효과적으로 무선 인지 시스템의 성능을 나타내는 추가적인 몇 가지 측정방법을 검토한다.

Let us first denote the failure alarm and false detection probability, respectively, when user detection is performed only once (i.e., one determination of user presence first). Most of the existing research focuses only on these performance measures. In practice, however, we review some additional measures that represent the performance of a wireless cognitive system.

가 커질수록 증가한다. 상기 무선 인지 시스템에서(예를 들면, IEEE 802.22 WRAN), 시스템 요건 중 하나는 시간 한계(즉, 용인가능한 검출 지연) 내에 주어진 값보다 큰 확률로 우선 사용자의 존재를 검출하는 것이다. 이 시간 한계를 T_limit(=

)으로 나타내자.The detection delay is defined as the time from when the user first appears to when the detection is completed when the user is successfully detected. Since the detection decision is made every frame, the detection delay is

Increases as is increased. In the radio recognition system (eg IEEE 802.22 WRAN), one of the system requirements is to first detect the presence of the user with a probability greater than a given value within a time limit (ie an acceptable detection delay). Set this time limit to T _limit (=

Let's express it.

로 각각 나타내자. 일반적으로, 검출-이론적인 시점으로부터가 아닌 시스템 전체시점으로부터 검출 지연, 최종 실패 알람 확률 및 최종 오검출 확률이 한 번의 우선 사용자 검출에 대한 실패 알람과 오검출 확률보다 더 실질적인 성능 측정방법이다.The final false detection probability for the radio aware user is defined as the probability that the radio aware user cannot detect the presence of the preferred user within the T _limit when the user is first activated. The final failure alarm probability is defined as the probability that at least one failure alarm is generated during the T _limit . The final failure alarm and the final false positive probability

Let's represent each. In general, detection delay, final failure alarm probability, and final false detection probability from a system-wide point of view, rather than from a detection-theoretical point of view, are more practical performance measures than failure alarm and false detection probability for a single preferred user detection.

(또는, 목표

)에 의해 주어질 수 있다. 본 발명에서, 시스템 요건으로서 목표

를 채택하는 시스템을 고찰한다. 주어진 T_limit와

대하여, 목표

는 아래의 [수식 11]과 같이 계산된다.First of all, the system requirements for user detection performance are T _limit and target.

(Or goal

Can be given by In the present invention, a goal as a system requirement

Consider a system that adopts With the given T _limit

Against

Is calculated as shown in Equation 11 below.

Then, based on the distribution of test statistics, the radio-aware user can determine the decision threshold ε for one preferred user detection as follows.

은 역 Q함수이다.here,

Is the inverse Q function.

를 계산한다. 우선 사용자가 프레임 내에서 임의의 OFDM 심벌의 초기에 활성화된다고 가정하자. 우선 사용자가 프레임(1≤l≤L) 내의 OFDM 심벌l에서 활성화될 때, 무선 인지 사용자는 (L-l+1) OFDM 심벌 시간 동안에만 우선 사용자 신호를 수신한다. 결국, 이러한 조건에서의

는 다음과 같이 표현될 수 있다.Next, when these thresholds are used

Calculate First assume that the user is activated at the beginning of any OFDM symbol in the frame. When the first user is activated at OFDM symbol l in frame 1 ≦ l ≦ L, the radio aware user receives the priority user signal only during the (L−1 + 1) OFDM symbol time. After all, under these conditions

Can be expressed as follows.

를 사용하면, 최종 오검출 확률 P는 다음과 같다.

Using, the final false detection probability P is

이다. N(1)+1은 T_limit내의 우선 사용자 검출 시도의 수에 상당하다. 마지막으로 평균 검출 지연 D는 다음과 같이 계산된다.here,

to be. N (1) +1 corresponds to the number of preferred user detection attempts within the T _limit . Finally, the average detection delay D is calculated as follows.

는 0.01로 설정된다.Looking at the radio recognition system summarized in Figure 2 based on the IEEE 802.22 WRAN specification, the parameters are

Is set to 0.01.

In order to generate a pilot signal in the simulation, a long pseudo noise (PN) sequence is used. First, consider an analog TV system that transmits random data by using residual sideband (VSB) modulation as a user. On the other hand, a simulation was first performed when the user is a wireless microphone using a frequency modulation (FM) having a bandwidth of 200 kHz. However, since the result is almost the same as when the user is an analog TV, the present invention does not include it.

First, when L = 10, first, the performance of the proposed scheme according to the user SNR is examined. It is clear from FIG. 3 that a preferred user having a strong signal can be more easily detected by the radio aware user. 1 also shows that the simulation and theoretical results fit well together. This indicates that the theoretical analysis is accurate, although derived first under simplified assumptions about user signals and pilot sequences. Therefore, from now on, only the theoretical results of the proposed method will be explained.

First, we compared the performance of the proposed method with the user detection method using the idle period and the user detection method using the CSC. Performance results for these two approaches were obtained using simulation. In the simulation, the scheme with a dormant period performs energy detection for the entire band of the radio aware system during one OFDM symbol time per frame. The method having the CSC first detects the presence of a user by utilizing a compensation OFDM symbol transmitted by a pilot subcarrier every frame.

4 first shows the last false detection probability according to the last failure alarm probability when the user SNR is 14 dB. In Figure 4 the detection performance with CSC is lower than that of the proposed scheme for the same L. This is because only a part of the OFDM symbols transmitted by the pilot subcarriers satisfy the necessary compensation conditions. It can be seen that the probability of false detection of the proposed scheme decreases when L increases in FIG. 4. This is due to the fact that more samples can be included in one preferred user detection even if the number of preferred user detection attempts within the T _limit decreases as L increases. 4 also shows that the detection performance of the proposed scheme is better than the scheme having a rest period when L is not less than ten.

FIG. 5 first shows the maximum utilization and average detection delay of the radio recognition system according to L when the user SNR is 12 dB. Since the proposed method and the CSC have a non-rest period detection method, a utilization of 1.0 can be achieved, and a method having a rest period has a lower utilization than 1.0. Furthermore, the average detection delay of the proposed scheme is less than the scheme with CSC. Therefore, it can be concluded that the proposed scheme can significantly increase system utilization while achieving better detection performance compared to other schemes. 5 also shows that as L increases, the mean detection delay of the proposed scheme is preferentially reduced and then slightly increased. This is because the average detection delay is affected not only by the frame length but also by the false detection probability of one preferred user detection.

In accordance with the present invention described above, an efficient PU detection scheme for a CR system that performs non-pause channel detection using a pilot cancellation scheme is proposed. Theoretical analysis and simulation results show that the proposed method can effectively detect the PU while significantly improving the utilization of the CR system. Since the complexity of the proposed scheme is very low, there are practical advantages, especially when implementing a CR system that already utilizes pilot subchannels.

The present invention is not limited to the above-described specific preferred embodiments, and various modifications can be made by any person having ordinary skill in the art without departing from the gist of the present invention claimed in the claims. Of course, such changes will fall within the scope of the claims.

1 is a flowchart showing a user detection method in a wireless recognition system according to the present invention.

2 is a table in which parameters show parameter values of a radio recognition system based on the IEEE 802.22 WRAN specification.

FIG. 3 is a graph showing test results of the performance of the proposed scheme according to user SNR, when L = 10 in the present invention.

4 is a graph showing a last false detection probability according to the last failure alarm probability when the user SNR is 14 dB in the present invention.

5 is a graph showing the maximum utilization and the average detection delay of the radio recognition system according to L when the user SNR is 12dB in the present invention.

Claims (6)

delete In a method of detecting a user first, the wireless recognition users (recipients) in the wireless recognition system, Removing a pilot signal that is already known from a signal received through a pilot channel, and detecting a presence of a preferred user without a rest period based on the strength of the received signal after removing the pilot signal; , The first user detection process, A sampling step of collecting received signal samples; Calculating a channel coefficient using the received signal sample and a known pilot sequence; Pilot canceling the pilot interference from the received signal sample; And performing a statistic of the received signal sample from which the pilot interference has been removed, and comparing the statistic with a reference value set to determine the presence of the user first. First user detection method in. 3. The method of claim 2, wherein the sampling step collects received signal samples of pilot subcarriers in orthogonal frequency division multiple access systems. 4. The method of claim 3, wherein the collection of the received signal samples is performed in units of frames. The method of claim 4, wherein the channel estimation step, The first user detection method in a wireless recognition system, characterized in that performed at the end of the frame. The method of claim 2, wherein the decision step, And determining that a user exists first when the statistical value is larger than the reference value.

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