WO2024080519A1

WO2024080519A1 - System and method for communication security in multi-antenna system using power control space-time block code

Info

Publication number: WO2024080519A1
Application number: PCT/KR2023/011380
Authority: WO
Inventors: 짠삿탸; 이혜인; 김수영
Original assignee: 전북대학교산학협력단
Priority date: 2022-10-11
Filing date: 2023-08-03
Publication date: 2024-04-18
Also published as: KR102657928B1

Abstract

The present invention relates to a power control space-time block code (STBC) multi-antenna (MIMO) communication security system and method enabling minimization of total transmitted power by adding artificial noise after shifting the phase thereof in a multi-antenna system using a space-time block code scheme, wherein channel information pre-shared between a transmission side and a reception side is used to add artificial noise to a transmission signal and transmit same so as to minimize transmission power and prevent illegal acquisition of information by an eavesdropper according to communication security.

Description

Communication security system and communication security method in multi-antenna system of power control space-time block code

In the present invention, when adding artificial noise in a multi-antenna (Multi-Input Multi-Output, MIMO) system using the space-time block code (STBC) method, the total transmitted power can be minimized by shifting the phase of the artificial noise and adding it. It relates to a power control space-time block code multi-antenna communication security system and its communication security method.

The space-time block code (STBC) method is a technology that can improve performance while using the same power through time and space diversity gain by transmitting signals using multiple antennas. It has been used as a standard since the 4th generation mobile communication system. . More specifically, compared to the transmission method using a single antenna, there is no difference in transmission rate, but the final bit error rate (BER) performance is improved by modifying and transmitting the form of the signal to be transmitted through multiple antennas for each symbol period using a coding matrix. This is a way that can be improved.

Recently, as communication between devices such as the Internet of Things (IoT) has become more active, security performance is also considered an important performance factor in addition to bit error rate (BER) and capacity, which were considered performance measures in conventional communication methods, and physical layer Research is underway on physical layer security (PLS) technology to improve security performance in transmission technology.

Figure 1 shows that in a conventional system model capable of eavesdropping, the transmitter adds artificial noise located in the null space of the channel state information (CSI) corresponding to the signal path between the legal transmitter and receiver (10, 20). , the legal receiver (20) is able to acquire appropriate information as the artificial noise is automatically canceled, but the illegal eavesdropper (30) in a different channel environment is unable to acquire information due to interference due to similar noise. This is a wiretapping channel model using the existing artificial noise (AN)-supported PLS method for the Alamouti code, and is composed of three entities: a legal transmitter, a legal receiver, and an illegal wiretap. In this channel model, the legal receiver (20) and the illegal receiver (30) form a system with one legal receiving antenna (22) and one illegal receiving antenna (32), respectively, while the legal transmitter has two transmitting antennas ( 12, 14) is assumed to be in place. Additionally, the legitimate sender (10) and the legitimate receiver (20) share CSI, h = [h ₁ h ₂ ] ^T. Here, h ₁ and h ₂ are the channel gains of the signal path from the first transmitting antenna 12 and the second transmitting antenna 14 of the legal transmitter 10 to the legal receiving antenna 22 of the legal receiver 20, respectively. am. On the other hand, the illegal eavesdropper 30 knows the CSI between the legal sender 10 and the illegal eavesdropper 30, g = [g ₁ g ₂ ] ^T , where g ₁ and g ₂ are the legal sender, respectively. This is the channel gain of the signal path from the first transmitting antenna (12) and the second transmitting antenna (14) in (10) to the illegal receiving antenna (32) of the illegal eavesdropper (30).

However, the conventional method had the disadvantage of low power efficiency because additional power was required to add artificial noise. In other words, the legitimate sender 10 must consume more power so that the legitimate receiver 20 can obtain the same bit error rate (BER) performance. Alternatively, if the legal transmitter 10 transmits using the same power as when artificial noise was not added, the legal receiver 20 can maintain security, but the reception bit error rate (BER) performance is lower than when artificial noise was not added. The downside is that it deteriorates further. In addition, due to the addition of artificial noise, which is a function of the channel gain, there is a problem that the size of the signal is not maintained constant and the average power to maximum power ratio (PAPR) increases, which may adversely affect transmission performance.

[Prior art literature]

[Patent Document]

Republic of Korea Patent Publication No. 10-0974120 (2010.08.04., notice)

U.S. Patent Publication No. 10069592 (2018.09.04., notice)

Republic of Korea Patent Publication No. 10-2002497 (July 23, 2019, notice)

Republic of Korea Patent Publication No. 10-1468894 (2014.12.09., notice)

Republic of Korea Patent Publication No. 10-0981554 (2010.09.10., notice)

The purpose of the present invention is to solve the above problem, and to provide a system for improving power efficiency while providing security functions for multiple antenna technology using the space-time block code (STBC) method.

In addition, the present invention provides closed-loop multi-antenna communication security using a new closed-loop space-time block code (STBC) multi-antenna system that minimizes the total power per transmission cycle and prevents illegal information acquisition by eavesdroppers. Another purpose is to provide a method.

In order to achieve the above object, the present invention includes a modulator that modulates data bits to generate a plurality of transmission signals; an STBC encoder that encodes a plurality of transmission signals modulated by the modulator into a space-time block code; A signal pair grouper for grouping the transmission signal encoded with the space-time block code into a complex symbol pair by combining two symbols for each symbol period into one pair; An artificial noise generator that generates artificial noise corresponding to each pair of signals grouped in the signal pair grouper using channel information pre-shared between legal transmitting and receiving ends; The phase shift calculation unit calculates the amount of phase shift so that the total power transmitted by the complex symbol pair of the signal pair grouping device through the transmission antenna is minimized, and the artificial noise phase shift unit calculates the amount of artificial noise generated by the artificial noise generator. An artificial noise adder that shifts the phase and adds the phase-shifted artificial noise of the artificial noise phase shift unit in the power control unit to each symbol pair grouped in the signal pair grouper; It is characterized by providing a communication security system in a multi-antenna system of a power-adjusted space-time block code, including a power-adjusted signal distributor that assigns and transmits each pair of signals whose power has been adjusted in the artificial noise adder to the corresponding transmission antenna. am.

In addition, the present invention (a) divides the data bits to be transmitted from the modulator into M symbols s _1, s ₂ ,... , modulating with s _N ; (b) generating, by the STBC encoder, from the modulated M symbols a coding matrix having a size T Х N to be transmitted through N transmission antennas during a T time period; (c) grouping the coding matrix generated to consist of N symbols for each symbol period into complex symbol pairs having two symbols in a signal pair grouper; (d) using pre-shared channel information in an artificial noise generator to generate artificial noise so that they can cancel each other out at a legal receiving end that will receive the transmitted signal; (e) After calculating the phase shift amount α in the phase shift calculation unit of the artificial noise adder, performing the phase shift process of the artificial noise generated by the artificial noise generator in the artificial noise phase shift unit, and then performing the phase shift process of the artificial noise generated in the artificial noise generator, the signal is generated in the power control unit. Adjusting power by adding artificial noise to each pair grouped in the pair grouping machine; (f) In the power control signal distributor, the power-adjusted signal of the artificial noise adder is transmitted through the transmission antennas (A ₁ and A ₂ ) to (x ₁ +μ ₁ e ^iα ) and (x ₂ +μ ₂ e ^iα ), respectively. It is characterized by providing a communication security method in a multi-antenna system of a power-adjusted space-time block code, including the step of distributing so that can be transmitted.

In addition, in the present invention, the signal pair grouping device is such that the first and second signals constituting each pair are x ₁ and x ₂ , and the transmission antennas through which x ₁ and x ₂ are transmitted are A ₁ and A ₂ , respectively, When the channel gains of the path transmitted to the legal receiving end through A ₁ and A ₂ are h ₁ and h ₂ , respectively, a total of N/2 {x ₁ , x ₂ } pairs are generated, and the artificial noise generator is x ₁ and Create artificial noise μ ₁ and μ ₂ to be added to x ₂ , where μ ₁ =-h ₂ v and μ ₂ =h ₁ v or μ ₁ =h ₂ v and μ ₂ =-h ₁ v, and v is the average This is an independent random variable that is 0, and within a pair, v can have the same value.

In addition, in the present invention, the phase shift amount for μ ₁ and μ ₂ in the artificial noise adder is commonly α, and the phase shift amount α is expressed in the following equation 1,

(The Re(x) and Im(x) are the real and imaginary parts of the complex signal x).

Additionally, in the present invention, the phase shift process in the artificial noise adder can be performed by multiplying μ ₁ and μ ₂ by e ^iα (where i=√(-1)), respectively.

Additionally, in the present invention, power control in the artificial noise adder can add μ ₁ e ^iα and μ ₂ e ^iα to x ₁ and x ₂ , respectively.

According to the present invention, a multi-antenna communication security system using a power-adjustable space-time block code transmits artificial noise to the transmission signal using channel information pre-shared between the transmitting side and the receiving side, thereby minimizing transmission power and ensuring communication security. It has the advantage of preventing illegal information acquisition by eavesdroppers in advance.

Figure 1 is a diagram illustrating a wiretapping channel model using the AN-supported PLS method for the conventional Alamouti code.

Figure 2 is a diagram illustrating a communication security system in a multi-antenna system of a power-adjusted space-time block code that allows total transmitted power to be minimized, according to an embodiment of the present invention.

Figure 3 is a flowchart showing a communication security method in a multi-antenna system with power control space-time block code according to the present invention.

A communication security system in a multi-antenna system of a power-adjustable space-time block code according to an embodiment of the present invention includes a modulator that modulates data bits to generate a plurality of transmission signals; an STBC encoder that encodes a plurality of transmission signals modulated by the modulator into a space-time block code; A signal pair grouper for grouping the transmission signal encoded with the space-time block code into a complex symbol pair by combining two symbols for each symbol period into one pair; An artificial noise generator that generates artificial noise corresponding to each pair of signals grouped in the signal pair grouper using channel information pre-shared between legal transmitting and receiving ends; The phase shift calculation unit calculates the amount of phase shift so that the total power transmitted by the complex symbol pair of the signal pair grouping device through the transmission antenna is minimized, and the artificial noise phase shift unit calculates the amount of artificial noise generated by the artificial noise generator. An artificial noise adder that shifts the phase and adds the artificial noise phase-shifted in the artificial noise phase shift unit in the power control unit to each symbol pair grouped in the signal pair grouper; It is characterized by comprising a power adjustment signal distributor that allocates and transmits each pair of signals whose power has been adjusted in the artificial noise adder to the corresponding transmission antenna.

Hereinafter, an embodiment of a communication security system in a power control space-time block code multiple antenna system according to the present invention will be described in detail with reference to the attached drawings.

In Figure 2, the communication security system in the multi-antenna system of the power control space-time block code of the present invention consists of a legal transmitting end 100 and a legal receiving end 200 that pre-share the channel phase information of the transmitting side according to the closed-loop transmission technique. It is composed. The legal transmitter 100 includes a modulator 110, an STBC encoder 120, a signal pair grouper 130, an artificial noise generator 140, an artificial noise adder 150, and a power control signal distributor 160.

The modulator 110 of the legal transmitting end 100 modulates the data bits to be transmitted into M complex transmission signals greater than 2 and transmits the plurality of data bits to the STBC encoder 120.

The STBC encoder 120 calculates a coding matrix Z, that is, T x N, representing signals to be simultaneously transmitted to N antennas during a T symbol period.

The signal pair grouper 130 groups a total of N symbols into two groups during each symbol period to generate a total of N/2 complex symbol pairs. At this time, N is a multiple of 2, and the number of grouped complex symbol pairs input from the signal pair grouper 130 to the artificial noise adder 150 is one each.

The artificial noise generator 140 generates artificial noise for each complex symbol pair generated by the signal pair grouping device 130 using channel information previously shared by the legal transmitting end 100 and the legal receiving end 200. create At this time, the artificial noise generated in the legal transmitting end 100 is automatically canceled at the legal receiving end 200, so information can be acquired.

The artificial noise adder 150 adjusts the power of the transmitted signal by shifting the phase of the artificial noise generated by the artificial noise generator 140 and adding it to the transmitted signal.

The power adjustment signal distributor 160 distributes the power-adjusted signal so that it can be transmitted from each antenna.

The signal pair grouper 130 inputs the generated N/2 plural symbol pairs into a plurality of artificial noise adders 150, and the artificial noise adders 150 change the phase to the corresponding power control signal distributor 160. The transmitted artificial noise is added to the transmission signal and transmitted.

Therefore, in the present invention, the legal transmitting end 100 and the legal receiving end 200, which pre-share channel information, add the artificial noise generated by the artificial noise generator 140 to the artificial noise adder 150 using the channel information, thereby creating a legal The receiving end 200 maximizes power efficiency by shifting and adding the phase of the artificial noise so that the total transmission power is minimized while being completely unaffected by the artificial noise.

Regarding the communication security method in the power control space-time block code multi-antenna communication security system of the present invention, the operation process at the legal transmitting end will be described with reference to the flowchart of FIG. 2.

The modulator 110 divides the data bits to be transmitted into M symbols, that is, s _1, s ₂ ,... , modulated with s _N. In addition, as channel information of the path of the signal transmitted from a total of N transmitting antennas (A ₁ , A ₂ , ..., A _N ) to the legal receiving end 200, h _1, h ₂ , ... , h _N is input (S110). At this time, the modulator 110 receives channel information on the path of a signal transmitted from a plurality of M symbols and N transmission antennas (A ₁ , A ₂ , ..., A _N ).

And the STBC encoder 120 constructs an STBC encoding matrix Z for transmission for T time from the M modulated symbols to N transmission antennas (A ₁ , A ₂ , ..., A _N ) (S120). At this time, N is the number of transmission antennas, T is the symbol period required to transmit M symbols, and Z is a matrix with a size of (T × N), and each row vector of matrix Z is the STBC transmitted during each symbol period. It is an encoded complex signal.

For reference, when T=N, it is called a full rate method that can achieve maximum transmission efficiency, and this is also called a method with a coding rate of 1.

In order to transmit the signals generated in step S120 during the T symbol period, the first transmission time is set (S125).

Then, the signal pair grouper 130 groups signals to be transmitted to each of the N transmission antennas into two pairs during the corresponding symbol period (S130). At this time, the first and second signals constituting each pair are x ₁ and x ₂ , the transmitting antennas through which x ₁ and x ₂ are transmitted are A ₁ and A ₂ , respectively, and the transmitting antennas A ₁ and A ₂ are If the channel gains of the transmitted paths are h ₁ and h ₂ , respectively, a total of N/2 {x ₁ , x ₂ } pairs are generated.

Next, the artificial noise generator 140 generates artificial noises μ ₁ and μ ₂ to be added to x ₁ and x ₂ (S140). In this case, μ ₁ =-h ₂ v and μ ₂ =h ₁ v or μ ₁ =h ₂ v and μ ₂ =-h ₁ v, and within a pair, v is the same value, and each pair is an independent variable with an average of 0. It is a random variable.

The phase shift calculation unit 152 in the artificial noise adder 150 calculates the common phase shift amount α for μ ₁ and μ ₂ using the following equation 1 (S152). The phase shift amount α is calculated using Equation 1 below.

Here, Re(x) and Im(x) are the real and imaginary parts for the complex signal x.

The artificial noise phase shift unit 154 included in the artificial noise adder 150 uses the phase shift amount α calculated in the artificial noise calculation unit 152 to calculate e ^iα for the artificial noises μ ₁ and μ ₂ , respectively. Multiply (S154). At this time, i=√(-1) is an imaginary number.

And the power control unit 156 in the artificial noise adder 150 adds μ ₁ e ^iα and μ ₂ e ^iα to x ₁ and x ₂ , respectively (S156).

For the signal pairs performed in steps S140 to _S156 in a total of N/2 pairs, the power control signal distributor ₁₆₀ provides (x ₁ +μ ₁ e ^iα ) and (x ₂ +μ ₂ e ^iα ) is distributed so that it can be transmitted (S160).

Additionally, it is checked whether the transmission symbol period has reached T (S170), and if not, the symbol period is increased by 1 (S175), and the process is repeated from step S130.

Artificial noise addition and power control according to the method of FIG. 3 are added and adjusted so that they can all be canceled at the legal receiving end 200 using the channel information between the legal transmitting end 100 and the legal receiving end 200, so that the legal receiving end (200) In 200), it is possible to obtain transmission information using a normal detection method, and since the eavesdropper does not know this channel information, the signal cannot be decoded even if an appropriate signal detection method is used due to serious interference due to the added artificial noise. .

In the above, preferred embodiments of the present invention have been shown and described, but the present invention is not limited to the specific embodiments described above, and may be used in the technical field to which the invention pertains without departing from the gist of the present invention as claimed in the claims. Of course, various modifications can be made by those skilled in the art, and these modifications should not be understood individually from the technical idea or perspective of the present invention.

Claims

A modulator that modulates data bits to generate a plurality of transmission signals;

an STBC encoder that encodes a plurality of transmission signals modulated by the modulator into a space-time block code;

A signal pair grouper for grouping the transmission signal encoded with the space-time block code into a complex symbol pair by combining two symbols for each symbol period into one pair;

An artificial noise generator that generates artificial noise corresponding to each pair of signals grouped in the signal pair grouper using channel information pre-shared between legal transmitting and receiving ends;

The phase shift calculation unit calculates the amount of phase shift so that the total power transmitted by the complex symbol pair of the signal pair grouping device through the transmission antenna is minimized, and the artificial noise phase shift unit calculates the amount of artificial noise generated by the artificial noise generator. An artificial noise adder that shifts the phase and adds the artificial noise phase-shifted in the artificial noise phase shift unit in the power control unit to each symbol pair grouped in the signal pair grouper;

A communication security system in a multi-antenna system of a power-adjusted space-time block code, comprising a power-adjusted signal distributor that allocates and transmits each pair of signals whose power has been adjusted in the artificial noise adder to corresponding transmission antennas.
(a) The data bits to be transmitted from the modulator are divided into M symbols s 1, s 2 , … , modulating with s N ;

(b) generating, by the STBC encoder, from the modulated M symbols a coding matrix having a size of T

(c) grouping the coding matrix generated to consist of N symbols for each symbol period into complex symbol pairs having two symbols in a signal pair grouper;

(d) using pre-shared channel information in an artificial noise generator to generate artificial noise so that they can cancel each other out at a legal receiving end that will receive the transmitted signal;

(e) After calculating the phase shift amount α in the phase shift calculation unit of the artificial noise adder, performing the phase shift process of the artificial noise generated by the artificial noise generator in the artificial noise phase shift unit, and then performing the phase shift process of the artificial noise generated in the artificial noise generator, the signal is generated in the power control unit. Adjusting power by adding artificial noise to each pair grouped in the pair grouping machine;

(f) In the power control signal distributor, the power-adjusted signal of the artificial noise adder is transmitted through the transmission antennas (A 1 and A 2 ) to (x 1 +μ 1 e iα ) and (x 2 +μ 2 e iα ), respectively. A communication security method in a multi-antenna system of a power-adjusted space-time block code, including the step of distributing so that can be transmitted.
The method of claim 2, wherein the first and second signals constituting each pair are x 1 and x 2 , and the transmission antennas through which x 1 and x 2 are transmitted are A 1 and A 2 , respectively, When the channel gains of the path transmitted to the legal receiving end through A 1 and A 2 are h 1 and h 2 , respectively, a total of N/2 {x 1 , x 2 } pairs are generated, and the artificial noise generator is x 1 and Create artificial noise μ 1 and μ 2 to be added to x 2 , where μ 1 =-h 2 v and μ 2 =h 1 v or μ 1 =h 2 v and μ 2 =-h 1 v, and v is the average This is an independent random variable of 0, and v is the same value within a pair. A communication security method in a multi-antenna system of a power-adjusted space-time block code.
According to claim 2, in the artificial noise adder, the phase shift amounts for μ 1 and μ 2 are commonly α, and the phase shift amount α is expressed by the following equation 1,

(The Re(x) and Im(x) are the real and imaginary parts of the complex signal x). A communication security method in a multi-antenna system of a power-adjusted space-time block code.
The multi-antenna of claim 2, wherein the phase shift process in the artificial noise adder is performed by multiplying μ 1 and μ 2 by e iα (where i=√(-1)), respectively. Communication security method in the system.
The communication security method according to claim 2, wherein the artificial noise adder adds μ 1 e iα and μ 2 e iα to x 1 and x 2 , respectively.