KR101268730B1 - System and method for enhancement of physical layer security in cognitive radio networks - Google Patents

Abstract

Disclosed are a physical layer security enhancement system and method using a frequency reuse technique. In the CR (Cognitive Radio) network, a device for enhancing the security of the physical layer by using a frequency reuse scheme is transmitted from a primary transmitter (primary Tx) to a primary receiver (primary Rx) by using signal transmission through the frequency reuse scheme. By interfering with the eavesdropping signal of the eavesdropper, the signal transmitted to the primary receiver can be enhanced.

Description

Physical layer security enhancement system and method using frequency reuse technique {SYSTEM AND METHOD FOR ENHANCEMENT OF PHYSICAL LAYER SECURITY IN COGNITIVE RADIO NETWORKS}

Embodiments of the present invention relate to a physical layer security enhancement apparatus and method using a frequency reuse technique for enhancing the security of a transmitted signal using physical layer signal processing technology in a wireless communication network.

Research on security technology has been addressed in the physical layer of wireless communications since the introduction of the concept of security rate in an environment where wiretap channels exist.

1 is a diagram illustrating a wireless communication system in which an eavesdropping node exists.

As shown, when the signal transmitted by the transmitter 110 is x, the channel between the transmitter 110 and the receiver 120 is h , and the channel between the transmitter 120 and the eavesdropper 130 is g . The signal received by the receiver 120 and the eavesdropper 130 is shown in Equation 1 below.

Where y _r is the signal received by the receiver, y _e Are signals received by the eavesdropper, and n _r and n _e represent noise generated during the reception process at the receiver and the eavesdropper's terminal, respectively.

Here, the power used by the transmitter 110 is P _t In this case, the security capacity (C _secret ) can be obtained using Equation 2 below. The security capacity refers to the maximum transmission capacity that can transmit information to the receiver without error and prevent the eavesdropper from receiving the information.

Here, σ _r and σ _e mean noise magnitudes. In the present invention, it is assumed that noise follows a Gaussian distribution.

Equation 2 is a value obtained by subtracting the transmittable channel capacity between the transmitter 110 and the eavesdropper 130 from the transmittable channel capacity between the transmitter 110 and the receiver 120. Therefore, when the channel between the transmitter 110 and the eavesdropper 130 is better than the channel between the transmitter 110 and the receiver 120 according to the channel state, the security capacity value is '0'. . It should be noted that, in the case of a wireless communication channel, the channel state changes frequently, so that the security capacity of the wire-tap channel also moves back and forth between '+' and '0'.

In order to solve the above problems and provide stable security capacity, a system has been proposed in which a helper node is installed and used in a basic wire tap channel model.

As one of the techniques related to this, Korean Patent Publication No. 10-2008-0067680 (published July 21, 2008) "method and system for secure communication" in the first to provide secure communication without using encryption The transmitter transmits a noise signal over a communication channel in a range used by the receiver, and the receiver receives a transmission transmitted by a second transmitter over one or more of the communication channels in a range, and the Disclosing the transmission by the second transmitter from the noise signal using information from the first transmitter is described.

2 is a diagram illustrating a wireless communication system model in which a wiretap node and a helper node for increasing security capacity exist.

The helper node 240 may improve the security capacity between the transmitter 210 and the receiver 220 by using a multi-antenna signal processing technique. The beamforming vector used by the helper node 240 to transmit a signal using multiple antennas is w _2. If so, the security capacity (R _secret ) in the system shown in Figure 2 can be summarized as in Equation 3 below.

When the maximum power used by the helper node 240 is P _t , in order to design a transmission scheme of the helper node 240 to maximize the security capacity in such a system, the following equation 4 should be solved.

Equation 4 is not an equation form that can be solved at one time. Therefore, various methods have been devised to find a solution. Finally, it is known that the transmitter can be designed using Equation 5 below.

와

는 각각 h₂₁ 와 h₂₁의 직교방향으로 투영시키는 프로젝션(projection) 행렬이고, λ 는 0과 1 사이의 실수이다. W_{2 , opt} 값을 최종적으로 구하기 위해서는 λ 값을 0과 1 사이에서 변화시켜가면서, R_secret을 최대화시키는 λ 값을 선택하는 과정이 필요하다.
here,

Wow

Is a projection matrix projecting in the orthogonal directions of h ₂₁ and h ₂₁ , respectively, and λ is a real number between 0 and 1. In order to finally determine the value of W _{2 , opt} , it is necessary to select a value of λ that maximizes R _secret while changing the value of λ between 0 and 1.

Therefore, using the technology utilizing the helper node 240, even if the channel situation between the transmitter 210 and the receiver 220 is not better than the channel situation between the transmitter 210 and the wiretap 230, a high security capacity Can transmit However, since the technology using the helper node 240 has to install an additional node only for the purpose of providing security, it is too expensive to be utilized in a real situation and the possibility of realization is very low. There is this.

Additionally, a physical layer security enhancement apparatus and method using a frequency reuse technique that can increase security capacity at a low cost without installing a helper node is disclosed.

In the CR (Cognitive Radio) network, a device for enhancing the security of the physical layer by using a frequency reuse scheme is transmitted from a primary transmitter (primary Tx) to a primary receiver (primary Rx) by using signal transmission through the frequency reuse scheme. By interfering with the eavesdropping signal of the eavesdropper, the signal transmitted to the primary receiver can be enhanced.

According to one side, the security enhancement device may enhance the security of the signal transmitted to the primary receiver by transmitting a signal using multiple antennas.

According to another aspect, the security enhancement apparatus may cause interference to the eavesdropping signal while simultaneously transmitting a signal to a secondary receiver (secondary Rx).

According to another aspect, the security enhancement apparatus combines a real value of a channel vector value with each of the primary receiver, the wiretap and the secondary receiver to calculate a beamforming vector, and uses the calculated beamforming vector to calculate data. The amount of transmission can be determined.

According to another aspect, the beamforming vector may be calculated through the following equation.

는 총 합이 1 이 되게 하는 0 과 1 사이의 값을 갖는 파라미터, h_sp, h_se, h_ss는 각각 2차 송신기와 1차 수신기, 도청기, 2차 수신기의 채널임.Where w is the beamforming vector, v _max {Z} is the eigenvector corresponding to the Z matrix,

Is a parameter with a value between 0 and 1 that adds up to 1, h _sp , h _se , and h _ss are the channels of the secondary transmitter, primary receiver, eavesdropper and secondary receiver, respectively.

A system for enhancing the security of the physical layer by using a frequency reuse scheme in a Cognitive Radio (CR) network includes a primary Tx for transmitting a signal through the CR network, and a signal transmitted from the primary transmitter. A primary receiver (primary Rx), an eavesdropper for eavesdropping signals transmitted from the primary transmitter to the primary receiver, and by interfering with the eavesdropping signal of the eavesdropper using signal transmission via the frequency reuse technique; It may include a secondary transmitter (secondary Tx) for enhancing the security of the signal transmitted to the secondary receiver and a secondary receiver (secondary Rx) for receiving the signal transmitted from the secondary transmitter.

In the CR (Cognitive Radio) network, a method of enhancing the security of the physical layer by using a frequency reuse technique includes transmitting a signal by a secondary transmitter (secondary Tx) using the frequency reuse technique and the transmitted signal is primary And enhancing the security of the signal transmitted to the primary receiver by interfering with the interceptor's eavesdropping signal, which intercepts the signal transmitted from the transmitter (primary Tx) to the primary receiver (primary Rx).

The frequency reuse technique uses signals transmitted from the secondary transmitter to interfere with the eavesdropping signal, thereby increasing security capacity at low cost without additional helper nodes.

1 is a diagram illustrating a wireless communication system model in which an eavesdropping node exists.
2 is a diagram illustrating a wireless communication system model in which a wiretap node and a helper node for increasing security capacity exist.
3 is a diagram illustrating a physical layer security enhancement system using a frequency reuse technique according to an embodiment of the present invention.
4 is a graph illustrating an increase in physical layer security capacity through a secondary transmitter according to an embodiment of the present invention.
5 is a flowchart illustrating a physical layer security enhancement method using a frequency reuse technique according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

In general, a cognitive radio network has a primary user who is licensed for frequency use and a secondary user who reuses frequency without interfering with the primary user but who is not authorized to use the frequency. exist.

The physical layer security enhancement system and method using the frequency reuse technique according to the present invention can increase the security capacity of the primary user by utilizing the transmission technique of the secondary user without additionally installing a helper node.

3 is a diagram illustrating a physical layer security enhancement system using a frequency reuse technique according to an embodiment of the present invention.

Referring to the drawings, the physical layer security enhancement system using the frequency reuse technique includes the primary transmitter 310, the primary receiver 320, the eavesdropper 330, the secondary transmitter 340 and the secondary receiver 350. can do.

The primary transmitter 310 transmits a signal through the CR network, and the primary receiver 320 receives a signal transmitted from the primary transmitter 310.

The interceptor 330 eavesdrops a signal transmitted from the primary transmitter 310 to the primary receiver 320.

The secondary transmitter 340 enhances the security of the signal transmitted to the primary receiver 320 by generating interference to the eavesdropping signal of the eavesdropper 330 using signal transmission through a frequency reuse technique. That is, the signal of the secondary transmitter 340 ensures that the signal of the primary transmitter 310 is safely transmitted to the secondary receiver 320, while making it difficult for the eavesdropper to recover, thereby enhancing the security of the primary network. Let's do it.

Here, the secondary transmitter 340 may enhance the security of the signal transmitted to the primary receiver 320 by transmitting a signal using multiple antennas. In a multi-antenna design, by properly designing a beamforming vector that maximizes the security capacity according to the channel vector direction of the primary receiver 320 and the eavesdropper 330, it is possible to enhance the security of the signal transmitted to the primary receiver 320. have.

At this time, the secondary transmitter 340 transmits a signal to the secondary receiver 350 and may cause interference with the tapping signal. To this end, the secondary transmitter 340 calculates a beamforming vector by combining the real value of the channel vector value with each of the primary receiver 320, the eavesdropper 330, and the secondary receiver 350, and calculates the calculated beam. The amount of data transmission can be determined using the forming vector.

The secondary receiver 350 receives a signal transmitted from the secondary transmitter.

In the following, first, mathematically define a secondary transmitter design problem for the operation of the present technology. Secondly, we describe in detail how the secondary transmitter works by solving a defined problem.

Secondary transmitter ( Secondary Tx Design Technique Problem Definition

The design of the secondary transmitter 340 has to achieve two goals of helping to secure the signal from the primary transmitter 310 and transmitting data to the secondary receiver 350 at the same time.

For the first goal, the secondary transmitter 340 should be designed in such a way as to generate the maximum interference to the eavesdropping signal from the wiretap 330 while minimizing interference to the primary receiver 310. Mathematically speaking, it should be designed to maximize security capacity.

Second, the goal of transmitting data to the secondary receiver 350 must be achieved. In other words, the quality of service (QoS) of the secondary network must be met or exceeded. When the maximum power that can be used in the secondary transmitter 340 is P _s , these two goals can be summarized by Equation 6 below.

In Equation 6, the power of the primary transmitter 310 is P _p. When we define, the security capacity R _secret Is defined as in Equation 7.

In Equation 6, R _s (w), which is the data transmission amount of the secondary network, and R _{min, which is} a value for guaranteeing the data transmission amount. The definition of is as shown in Equation 8.

When the secondary transmitter 340 transmits the maximum amount of data transmission to the secondary receiver 350 as R _{s, max} , the secondary transmitter 340 finally designed in the present invention is '0' and '1'. The amount of data transmission to be transmitted to the secondary receiver 350 is determined according to the α value having a value between '. The α value can vary depending on the requirements of the system. In addition, R _{s and max} refer to the amount of data transmission when the secondary transmitter 340 uses a maximum ratio transmission technique for transmitting data at the transmitting end.

Finally, in the present invention, the beamforming vector w used in the secondary transmitter 340 is provided based on the solution of Equation 6 for the design of the secondary transmitter 340.

Find the optimal w value

Hereinafter, a detailed transmitter design for increasing security capacity, that is, a method of obtaining an optimal w in Equation 6 will be described.

Various methods for solving Equation 6 may exist, but the present invention proposes a method with low complexity.

In Equation 6, the optimal value of w can be expected to be made of a combination of h _sp , h _se , and h _ss , which are channels directly connected to the secondary transmitter 340. However, since the channel vector values of h _sp , h _se , and h _ss are complex values, finding the optimal w through the combination of complex numbers requires high complexity. Therefore, in the present invention, this can be found by using only a combination of real numbers using Equation 9 below.

Here, v _max {Z} represents an eigenvector (hereinafter, referred to as a first eigenvector) corresponding to the maximum eigenvalue of the Z matrix.

의 조합으로 Z 행렬을 구성한다.

의 다양한 조합을 통해 Z 행렬의 제1 고유벡터를 구하고, 구해진 여러 가지 후보들 가운데, 수학식 6에서 2차 네트워크의 데이터 전송량을 충족시키면서 보안 용량을 최대화 시키는 w 를 찾게 되면 그 값이 최종 해가 될 수 있다.Specifically, it is a parameter having a value between '0' and '1' that adds up to '1'.

Combination constitutes Z matrix.

If we find the first eigenvector of the Z matrix through various combinations of, and find out w among the candidates obtained from Equation 6 that maximizes the security capacity while satisfying the data transmission capacity of the secondary network, the value will be the final solution. Can be.

Through the above method, the physical layer security enhancement system using the frequency reuse technique according to the present invention can effectively receive the data signal sent from the primary transmitter 310 through the design of the secondary transmitter 340 in the eavesdropper 330. While making it difficult, the reception performance at the primary receiver 320, which is the intended destination, can be increased. In addition, an appropriate amount of data may also be transmitted to the secondary receiver 350 at the same time.

Accordingly, the secondary transmitter 340 according to the present invention taps a signal of the eavesdropper 330 to eavesdrop a signal transmitted from the primary transmitter 310 to the primary receiver 320 by using signal transmission through a frequency reuse technique. By generating interference with respect to the signal transmitted to the primary receiver 320 can be enhanced.

4 is a graph illustrating an increase in physical layer security capacity through a secondary transmitter according to an embodiment of the present invention. Hereinafter, how the signal of the primary transmitter is received at the primary receiver and the eavesdropping node will be described through the security capacity value.

In the figure, it is shown in Equation 6 how the security capacity changes according to α, which is a data transmission requirement of the secondary network. When α is '0', the design purpose of the secondary transmitter is fully focused on the signal security of the primary transmitter, thus providing the highest security capacity.

In this respect, since the secondary transmitter must contribute to the transmission of the secondary network data simultaneously with the signal security of the primary transmitter, the security capacity is quite high even for high system requirements where the α value is about '0.8'. Is to maintain. In other words, it can be seen that even if the secondary transmitter devotes much of its data transmission, it shows the ability to protect the signal of the primary transmitter at the same time.

In the figure, the security capacity in the absence of an eavesdropping node and the security capacity without using the present invention are shown as reference curves.

5 is a flowchart illustrating a physical layer security enhancement method using a frequency reuse technique according to an embodiment of the present invention.

Hereinafter, a method of reinforcing the security of the physical layer using a frequency reuse scheme in a Cognitive Radio (CR) network will be described.

First, the secondary transmitter (secondary Tx) transmits a signal using a frequency reuse technique.

To this end, the beamforming vector of the secondary transmitter may be calculated through a combination of real values of channel vector values with each of the primary receiver, the wiretap and the secondary receiver (S510). The data transmission amount of the secondary transmitter is determined through the calculated beamforming vector (S520). In this case, the beamforming vector may be calculated using Equation 9 described above.

The signal of the secondary transmitter transmitted through the above process can enhance the security of the signal transmitted to the primary receiver by generating interference to the eavesdropping signal of the eavesdropper tapping the signal transmitted from the primary transmitter to the primary receiver. .

As described above, the present invention has been described by way of limited embodiments and drawings, but the present invention is not limited to the above embodiments, and those skilled in the art to which the present invention pertains various modifications and variations from such descriptions. This is possible.

Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined by the equivalents of the claims, as well as the claims.

310: primary transmitter
320: primary receiver
330: wiretap
340: secondary transmitter
350: secondary receiver

Claims (13)

In the device for enhancing the security of the physical layer by using a frequency reuse scheme in a CR (Cognitive Radio) network,
The signal is transmitted to the primary receiver by interfering with the eavesdropping signal of the eavesdropper, which intercepts the signal transmitted from the primary transmitter (primary Tx) to the primary receiver (primary Rx) by using the signal transmission through the frequency reuse technique. Strengthen the security of the signal,
And interfering with the eavesdropping signal simultaneously with transmitting the signal to a secondary receiver (secondary Rx). The method of claim 1,
The security strengthening device,
And strengthening the security of a signal transmitted to the primary receiver by transmitting a signal using multiple antennas. delete The method of claim 1,
The security strengthening device,
And a beamforming vector are calculated by combining real values of channel vector values with each of the primary receiver, the wiretap and the secondary receiver, and determining the amount of data transmission using the calculated beamforming vector. . 5. The method of claim 4,
The beamforming vector is
Security enhancing apparatus, characterized in that calculated through the following equation.

Where w is the beamforming vector, v _max {Z} is the eigenvector corresponding to the Z matrix,

Are parameters having a value between 0 and 1 such that the sum is 1, h _sp , h _se , and h _ss are the channels of the secondary transmitter, the primary receiver, the eavesdropper and the secondary receiver, respectively. In a system for enhancing the security of the physical layer by using a frequency reuse technique in a CR (Cognitive Radio) network,
A primary transmitter for transmitting a signal through the CR network;
A primary receiver for receiving a signal transmitted from the primary transmitter (primary Rx);
An eavesdropper for eavesdropping signals transmitted from the primary transmitter to the primary receiver;
A secondary transmitter (secondary Tx) for enhancing the security of the signal transmitted to the primary receiver by generating interference to the eavesdropping signal of the interceptor using the signal transmission through the frequency reuse technique; And
Secondary receiver (secondary Rx) for receiving a signal transmitted from the secondary transmitter
Including, security enhancement system. The method according to claim 6,
The secondary transmitter,
And strengthening the security of the signal transmitted to the primary receiver by transmitting the signal using multiple antennas. The method according to claim 6,
The secondary transmitter,
And interfering with the eavesdropping signal while transmitting a signal to a secondary receiver (secondary Rx). The method according to claim 6,
The secondary transmitter,
Security enhancement system, characterized in that to calculate the beamforming vector by combining the real value of the channel vector value with each of the primary receiver, the wiretap and the secondary receiver, and to determine the amount of data transmission using the calculated beamforming vector . 10. The method of claim 9,
The beamforming vector is
Security enhancement system characterized in that it is calculated through the following equation.

Where w is the beamforming vector, v _max {Z} is the eigenvector corresponding to the Z matrix,

Are parameters having a value between 0 and 1 such that the sum is 1, h _sp , h _se , and h _ss are the channels of the secondary transmitter, the primary receiver, the eavesdropper and the secondary receiver, respectively. In the method of strengthening the security of the physical layer by using a frequency reuse technique in a CR (Cognitive Radio) network,
A secondary transmitter (secondary Tx) transmitting the signal using the frequency reuse technique; And
Enhances the security of the signal transmitted to the primary receiver by interfering with the eavesdropping signal of the eavesdropper, which intercepts the transmitted signal from the primary transmitter (primary Tx) to the primary receiver (primary Rx). step
Lt; / RTI >
The step of transmitting the signal,
Calculating a beamforming vector by combining real values of channel vector values with each of the primary receiver, the wiretap and the secondary receiver; And
Determining a data transmission amount of the secondary transmitter using the calculated beamforming vector
Including, method for enhancing security. delete The method of claim 11,
Computing the beamforming vector,
Security enhancement method characterized in that for calculating the beamforming vector using the following equation.

Where w is the beamforming vector, v _max {Z} is the eigenvector corresponding to the Z matrix,

Are parameters having a value between 0 and 1 such that the sum is 1, h _sp , h _se , and h _ss are the channels of the secondary transmitter, the primary receiver, the eavesdropper and the secondary receiver, respectively.

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