KR102002497B1 - Multiple Antenna Communication Systems using Space-Time Line Code - Google Patents

Abstract

A multi-antenna communication system using space-time coding is disclosed. A transmitting apparatus according to an embodiment of the present invention includes a plurality of antennas for transmitting and receiving radio signals, a Space-Time (STLC) system for processing a transmission symbol in a space-time linear coding scheme and outputting a plurality of coded signals for transmission at different times, An artificial noise signal generator for generating an artificial noise signal to be removed by STLC decoding, and a transmitter for generating a transmission signal by allocating power to the coded signal and the artificial noise signal, and transmitting the transmission signal through the plurality of antennas And a power allocation processor for sequentially transmitting the power control signal.

Description

TECHNICAL FIELD [0001] The present invention relates to a multi-antenna communication system using space-time coding,

The present invention relates to a multi-antenna communication system and method using space-time coding. In particular, when transmitting security information from a base station to an authentication terminal using a downlink channel, a space- To an antenna communication system.

In the case of exchanging information wirelessly between a base station and a terminal, since a transmission signal is transmitted to a region other than a receiver, there is always a security threat such as an unauthorized terminal. In particular, with the recent rapid increase of smart devices supporting wireless Internet, demand for highly secure mobile services such as mobile banking, electronic settlement, telemedicine, and secure document transmission through e-mail is increasing rapidly. Currently, authentication and encryption / decryption methods using encryption technology are applied to higher application layers to maintain security. However, recently, when using multiple antennas, physical layer Security transmission techniques are actively being studied. Especially, the 5th generation mobile communication system, which is being standardized recently, and the physical layer security communication technique for security and privacy protection are emphasized in the next generation wireless LAN.

A value obtained by subtracting the channel capacity (C _E ) between the base station and the non-authentication terminal from the channel capacity (C _B ) between the base station and the authentication terminal in order to measure the physical layer security level of the specific wireless communication system is defined as Secrecy Capacity _B- C _E ). Existing physical layer security research has been focused on the theoretical transmission capacity analysis according to the degree of channel information retention in various channel environments, base stations, authentication terminals, and unauthorized terminals. For example, when a base station, an authentication terminal, and an unauthorized terminal know channel information between all the mutual devices and all devices use multiple antennas, an optimal secure transmission rate can be obtained by applying a security dirty paper coding technique.

In a typical wireless communication system, since signal transmission is continuously performed between the base station and the authentication terminal through the downlink and the uplink, the downlink and uplink channel information between the base station and the terminal can be easily estimated. On the other hand, in the case of an unauthorized terminal for the purpose of eavesdropping, in order to conceal the existence of the eavesdropper in the neighboring base station and the authentication terminal, the terminal normally does not perform the operation of receiving the signal of the peripheral device to acquire information and transmitting the signal. Therefore, it is very difficult to estimate the channel information between the base station and the authentication terminal between the base station and the non-authentication terminal or between the authentication terminal and the non-authentication terminal. Therefore, it is not possible to apply the result obtained under the assumption of knowing the channel information of the non-authentication terminal among the existing studies on the security transfer rate to the actual communication system.

Therefore, it is required to develop a technology capable of increasing the security transmission capacity in a state in which the base station and the authentication terminal do not know the channel information about the non-authentication terminal.

In this connection, Korean Patent No. 10-1275851 entitled " Transmitting / Receiving Device and Method Based on Space-Time Block Coding Using UW (unique-word) "

The present invention is directed to a multi-antenna communication system and method using space-time coding that can increase a physical layer security rate by applying a space-time coding scheme when security information is transmitted from a base station to an authentication terminal using a downlink channel .

The technical problems of the present invention are not limited to the above-mentioned technical problems, and other technical problems which are not mentioned can be clearly understood by those skilled in the art from the following description.

According to an aspect of the present invention, there is provided a transmission apparatus including a plurality of antennas for transmitting and receiving radio signals, a plurality of transmission antennas for processing transmission symbols in a space-time linear coding scheme, An artificial noise signal generator for generating an artificial noise signal to be removed by STLC decoding, a transmission signal generator for generating a transmission signal by allocating power to the encoding signal and the artificial noise signal, To be transmitted sequentially through the plurality of antennas.

Preferably, the STLC encoder includes: a modulator for modulating input data with a predetermined modulation scheme to output a transmission symbol; a space-time coding unit for coding the transmission symbol in a space-time block coding scheme; And generates a coded signal.

Preferably, the encoded signal may be a signal of the following equation.

 [Mathematical Expression]

이고, H는 채널정보를 포함한 행렬, H ^H 는 행렬 H의 conjugate transpose를 나타냄.Here, S is a coded signal

H denotes a matrix including channel information, and H ^H denotes a conjugate transpose of matrix H.

Preferably, the artificial noise signal generator includes an antenna selector for selecting at least one of the plurality of antennas, an antenna corresponding to a number equal to or less than a half of the number of the plurality of antennas, And an artificial noise generator for generating artificial noise using the channel information and the complex noise for each of the generated groups, the artificial noise generator for each group, And an artificial noise signal generator for generating an artificial noise signal.

Preferably, the artificial noise signal should satisfy the following equation so as to be removed by STLC decoding.

[Mathematical Expression]

Here, a _{t , m} is the (t, m) th element of the artificial noise signal matrix A , h _{n , m} is the (n, m) th element of H , Channel gain between antennas.

Preferably, the artificial noise signal may be a signal of the following equation.

 [Mathematical Expression]

,

은 벡터 h _m 의 norm, z _n 은 랜덤하게 생성된 복소 잡음(Complex Noise)을 의미함.Here, h _m is an m-th column vector of the main channel H ,

,

Denotes the norm of the vector h _m , and z _n denotes the random noise (Complex Noise) randomly generated.

Preferably, the power allocation processor finds a power allocation ratio, which is a difference in data rate between an authenticated receiver and an unauthorized receiver, to a maximum using a grid search, A power corresponding to the power allocation ratio may be allocated to the signal, a remaining power may be allocated to the artificial noise signal, and a transmission signal may be generated by combining the transmission signal and the artificial noise signal.

Preferably, the transmission signal may be a signal of the following equation.

 [Mathematical Expression]

임.Here, X is a signal matrix transmitted by the transmitting apparatus, S is a coded signal, p is a power allocation ratio, A is an artificial noise signal,

being.

)을 간접적으로 추정하는 채널 이득 추정부, 상기 변환된 벡터에 상기 추정된 채널 이득을 적용하여 송신 심볼을 추정하는 스케일링부를 포함한다. According to another aspect of the present invention, there is provided a receiving apparatus including a plurality of antennas, a vector converting unit converting a signal received through the plurality of antennas into a vector, a blind SNR (signal-to-noise ratio ) Estimating scheme to estimate the channel gain < RTI ID = 0.0 >

), And a scaling unit for estimating a transmission symbol by applying the estimated channel gain to the transformed vector.

Preferably, the apparatus may further include a vector operation unit for transforming the signal converted into a vector in the vector conversion unit to demodulate the transmission symbol without CSI for the channel.

According to an aspect of the present invention, there is provided a multi-antenna communication system using space-time coding according to an exemplary embodiment of the present invention, which includes a plurality of antennas, encodes transmission symbols in a space-time linear coding scheme, A transmitting device for generating an encoded signal by selecting at least one antenna among the plurality of antennas to generate an artificial noise signal and combining the encoded signal and the artificial noise signal and transmitting the combined signal through the plurality of antennas, And a receiving apparatus for converting a signal received through the plurality of antennas provided into a vector and demodulating a transmission symbol in the signal converted into the vector using an asynchronous detection technique.

Preferably, the receiver indirectly estimates a channel gain included in the received signal using a blind SNR (Signal-to-Noise Ratio) estimation technique, and outputs the estimated channel gain to the transformed vector To estimate a transmission symbol.

According to the present invention, when the base station knows the main channel information ( H) , and when the authentication terminal and the non-authentication terminal do not know H , the signal is transmitted by combining the STLC coding technique and the artificial noise transmission technique, thereby maximizing the data transmission rate The transmission rate of the unauthorized terminal can be minimized.

According to the present invention, physical layer security is considered to be very important in the case of the fifth generation mobile communication and the next generation wireless LAN, which are being standardized recently, and the physical layer security of the next generation wireless communication system can be enhanced.

The effects of the present invention are not limited to the effects mentioned above, and other effects not mentioned can be clearly understood to those of ordinary skill in the art from the following description.

1 is a diagram for explaining a transmission / reception relationship of a MIMO system according to an embodiment of the present invention.
2 is a view for explaining a transmission apparatus for transmitting security information using a downlink channel according to an embodiment of the present invention.
3 is a block diagram for explaining the STLC encoder shown in FIG.
4 is a block diagram for explaining an artificial noise signal generator shown in FIG.
5 is a view for explaining a receiving apparatus for demodulating a transmission signal according to an embodiment of the present invention.

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that the invention is not intended to be limited to the particular embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention. Like reference numerals are used for like elements in describing each drawing.

The terms first, second, A, B, etc. may be used to describe various elements, but the elements should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be referred to as a second component, and similarly, the second component may also be referred to as a first component. And / or < / RTI > includes any combination of a plurality of related listed items or any of a plurality of related listed items.

It is to be understood that when an element is referred to as being "connected" or "connected" to another element, it may be directly connected or connected to the other element, . On the other hand, when an element is referred to as being "directly connected" or "directly connected" to another element, it should be understood that there are no other elements in between.

The terminology used in this application is used only to describe a specific embodiment and is not intended to limit the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In the present application, the terms "comprises" or "having" and the like are used to specify that there is a feature, a number, a step, an operation, an element, a component or a combination thereof described in the specification, But do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or combinations thereof.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in commonly used dictionaries are to be interpreted as having a meaning consistent with the contextual meaning of the related art and are to be interpreted as either ideal or overly formal in the sense of the present application Do not.

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

1 is a diagram for explaining a transmission / reception relationship of a MIMO system according to an embodiment of the present invention.

Referring to FIG. 1, a MIMO system according to an embodiment of the present invention includes a transmitter 100 having a plurality of antennas, and a receiver 200 having a plurality of antennas.

The transmitting apparatus 100 encodes a transmission symbol using a space-time linear coding (STLC) scheme, applies channel information H to the coded signal to generate a transmission signal, selects at least one antenna among a plurality of antennas, Generates a noise signal, combines it with a transmission signal and an artificial noise signal, and transmits through a plurality of antennas. The STLC enables asynchronous detection at the receiving device without channel information and achieves complete spatial diversity. Artificial noise may be removed after STLC decoding at the receiving device. That is, the artificial noise is transparent to the authentication terminal, but keeps the reception signal of the non-authentication terminal as interference.

The transmitting apparatus 100 may be, for example, a base station.

The receiving apparatus 200 converts a signal received through a plurality of antennas provided therein to a vector, and demodulates the signal converted into a vector by using an asynchronous detection technique. The receiving apparatus 200 includes an authentication terminal 210 having N _B antennas and an unauthenticated terminal 220 having N _E antennas. The transmitting apparatus 100 and the authentication terminal 210 send and receive signals through the authentication terminal channel H and the transmission apparatus 100 and the unauthenticated terminal 220 receive and transmit signals through the unauthorized terminal channel G. [ I will tap.

The present invention relates to a multi-antenna communication system for transmitting a downlink signal, wherein H denotes a matrix representing an N _B × M downlink main channel, G denotes a N _E × M downlink (Eavesdropper Channel). Accordingly, the authentication terminal 210 receives a signal from the base station 100 via the downlink main channel, and the non-authentication terminal 220 receives a signal from the base station 100 through the downlink channel.

A plurality of authentication terminals 210 and a plurality of unauthenticated terminals 220 coexist within the base station transmission range. Hereinafter, for convenience of description, it is assumed that one authentication terminal 210 and one unauthenticated terminal 220 exist I will explain. Also, in the present invention, it is assumed that the base station 100 only knows the main channel H and the authentication terminal 210 does not know the channel information H in order to enhance security in the downlink transmission. In addition, since the unauthenticated terminal 220 does not transmit a signal, it is assumed that the wired channel G does not know both the base station 100 and the authentication terminal 210. Since the authentication terminal 210 does not need to estimate the main channel H , the base station 100 does not transmit a pilot or training symbol for downlink channel estimation and the authentication terminal 210 does not have information on H , (Noncoherent Detection) technique is used to demodulate the transmitted signal. Since the base station 100 does not transmit a pilot or training symbol for channel estimation, the non-authentication terminal 220 can not estimate its own channel information G. In order to demodulate the security information in the signal received at the base station, Should be used.

The present invention maximizes the data rate of the authentication terminal 210 using the asynchronous detection technique using the new space-time coding technique using the channel information H , and in the unauthorized terminal 220 using the asynchronous detection technique, So that the transmission rate is very low.

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates generally to a STLC encoder, and more particularly, 2 is a block diagram for explaining an artificial noise signal generator shown in FIG.

2, a transmitter 100 for transmitting security information using a downlink channel according to an embodiment of the present invention includes a plurality of antennas (not shown), an STLC encoder 110, an artificial noise signal generator 120, and a power allocation processor 130.

The STLC encoder 110 encodes transmission symbols in a space-time linear coding scheme to generate a coded signal. That is, the STLC encoder 110 encodes a transmission symbol using Space-Time Line Code (STLC), which is a space-time coding scheme using channel information H.

STLC transmission method will be described on the assumption that one could also possible if the number of antennas of the authentication terminal 3 or more, the antenna of the authentication terminal for convenience of explanation hereinafter as 2 (N _B = 2).

When the number of antennas of the authentication terminal is 2 and the signal transmission interval is T, the STLC encoder 110 divides the symbols into two and sequentially transmits them for a time of 2T. That is, when STLC is used, the transmission symbols are encoded for two consecutive time intervals.

The STLC encoder 110 includes a modulation unit 112, a space-time coding unit 114, and a multiplication with channel.

The modulator 112 modulates the input data by a predetermined modulation scheme and outputs a transmission symbol. have. Various modulation methods such as Binary Phase Shift Keying (BPSK), Quadrature Phase Shift Keying (QPSK), Quadrature Amplitude Modulation (QAM), Pulse Amplitude Modulation (PAM), and Phase Shift Keying (PSK) Any of the modulation schemes can be applied.

The space-time coding unit 114 codes the transmission symbols modulated by the modulation unit 112 in a space-time linear coding scheme. That is, when the space-time coding unit 114 performs space-time coding by applying STLC to the two transmission symbols s ₁ and s ₂ modulated, the space-time coding unit 114 outputs symbols shown in Table 1 below.

Specifically, the space-time coding unit 114 encodes the two transmission data s1 and s2 in a time-space line coding scheme at time t and time t + T, respectively. Then, the two data signals s1 and s2 are generated as the signal components s1 and s2 at time t. Then, the two data signals s1 and s2 can be encoded into the signal components (-s2 *, s1 *) at time t + T.

를 생성한다. Therefore, the space-time coding unit 114

.

The channel operation unit 116 applies channel information to the signal encoded by the space-time encoding unit 114 to generate a coded signal. That is, the channel operation unit 116 multiplies the signal S encoded by the space-time encoding unit 114 by the channel information H ^H to generate a coded signal as shown in Equation (1). At this time, the encoded signal may be a matrix-shaped signal, and the value of the matrix X encoded according to the channel information H is changed.

That is, the channel operation unit 116 generates an M * 2 encoding matrix X to be transmitted through M base station antennas. The encoding matrix X is represented by Equation 1 below.

이고, Alamouti 부호 기반 시공간 블록 부호화 행렬을 나타내며,

는

-의 complex conjugation이다. H는 채널정보를 포함한 행렬, H ^H 는 행렬 H의 conjugate transpose를 나타낸다. 종래 시공간 부호화 기법에서는 행렬 S를 송신 안테나를 통해 전송하므로 송신장치에서 채널정보 H를 사용하지 않는다. 반면에 수학식 1로 표현된 STLC 부호화 기법에서는 H ^H 이 곱해지므로, 채널 정보 H에 따라 부호화된 행렬 X의 값이 변경된다. 이때 행렬 X의 (m,t)번째 원소 x _{m ,t} 는 시간 t에서 m번째 송신안테나를 통해 전송되는 부호화 심볼을 나타낸다.Here, S is a coded signal

Denotes an Alamouti code-based space-time block coding matrix,

The

- is a complex conjugation of. H denotes a matrix including channel information, and H ^H denotes a conjugate transpose of a matrix H. In the conventional space-time coding scheme, since the matrix S is transmitted through the transmission antenna, the channel information H is not used in the transmitting apparatus. On the other hand, in the STLC coding technique expressed by Equation (1), H ^H is multiplied, so that the value of the matrix X encoded according to the channel information H is changed. At this time, the (m, t) th element x _{m , t} of the matrix X at time t denotes an encoded symbol transmitted through an m < th > transmit antenna.

Specifically, the signal components s1 and s2 at time t are divided into components to be allocated to the respective transmit antennas TxAnt.0 to TxAnt.N-1 in the channel operation unit 116. [ That is, the signal components s1 and s2 are divided into components corresponding to the respective transmit antennas TxAnt.0 through TxAnt.N-1, and the signal components s1 and s2 are complex conjugates of channel information, Multiplied by the components. The signal components s1 and s2 multiplied by the complex conjugate of the estimated channel response are again combined for each transmit antenna.

The combined signal components for each antenna can be kept constant in transmission power through a normalization operation. In this process, the signals transmitted through the respective transmit antennas at time t are expressed by Equation (1). That is, at time t, transmission signals (? 0,? 1, ...,? N-1) are provided to the transmission antennas (TxAnt.0 to TxAnt.N-1).

The artificial noise generator 120 generates an artificial noise signal that is completely canceled in the authentication terminal and acts as a noise signal in the unauthorized terminal.

When the base station transmits a combined signal of the coded signal and the artificial noise signal, the authentication terminal simultaneously receives the STLC coded signal component and the artificial noise signal component. At this time, in order to prevent the data rate of the authentication terminal from being affected by the artificial noise, the artificial noise signal passing through the channel must be completely removed when passing through the authentication terminal. The condition for the artificial noise to be completely removed from the authentication terminal is expressed by Equation 2 below.

Where a _{t and m} are the (t, m) th elements of the noise signal signal matrix A , h _{n and m} are the (n, m) th elements of H , Represents the channel gain between the antennas.

The artificial noise generator 120 can design artificial noise signals in various ways using the condition of Equation (2).

Specifically, the artificial noise generator 120 may select at least one antenna among a plurality of antennas, group the antennas so that at least two antennas are included, and generate an artificial noise signal considering the number of antennas for each group. The artificial noise generator 120 may include an antenna selector 122, a grouping unit 124, an artificial noise generator 126, an artificial noise generator 126, (128).

The antenna selection unit 122 selects at least one antenna among the plurality of antennas, and selects antennas corresponding to the number of antennas equal to or less than half the number of the plurality of antennas. For example, the antenna selector 122 can arbitrarily select 2L antennas from M antennas, and L can be arbitrarily selected from natural numbers equal to or greater than 1 and equal to or smaller than M / 2.

And arbitrarily selects 2L antennas to transmit artificial noise signals among all the M base station transmission antennas. At this time, since the (M-2L) antennas that are not selected do not transmit artificial noise signals, a _{1 , m} = a _{2 , m} = 0, and the noise signal transmitted from the selected 2L antennas is removed from the authentication terminal. For convenience of explanation, artificial noise is transmitted from 1, 2, ..., 2Lth antenna among M antennas, artificial noise is transmitted from (2L + 1), (2L + 2) . At this time, if the artificial noise signal is defined as Equation (3), then Equation (2) is always satisfied.

은 벡터 h _m 의 norm을 나타내고,

으로 정의되며, z _n 은 랜덤하게 생성된 복소 잡음(Complex Noise)으로 2*1 벡터일 수 있다. 한편, 수학식 3으로 정의된 인공잡음 생성 방법은 다양한 방법으로 변형될 수 있다.Here, h _m is an m-th column vector of the main channel H ,

Denotes the norm of the vector h _m ,

, And z _n is a random noise (Complex Noise) randomly generated, and may be a 2 * 1 vector. Meanwhile, the artificial noise generation method defined by Equation (3) can be modified by various methods.

The grouping unit 124 generates at least one group by grouping the antennas selected by the antenna selection unit 122 so that at least two antennas are included.

For example, the grouping unit 124 may divide the antennas into L groups of two antennas in the form of (1,2), (3,4), ..., (L-1,2L) to generate artificial noise. Artificial noise can be generated by the method of Equation (3) after arbitrarily changing the method of dividing the total of 2L antennas by two. For example, an artificial noise can be generated by dividing the antenna into (1,2L), (2,2L-1), ..., (L, L + 1).

The artificial noise generator 126 generates artificial noise using the channel information and the complex noise for each group generated by the grouping unit 124. [

When grouping the selected two antennas in the grouping unit 124, the artificial noise generator 126 generates artificial noise for each group. At this time, the number of antennas included in one group can be arbitrarily changed to a value of 2 or more. For example, a group can be formed by grouping three selected antennas, and artificial noise can be generated by a method similar to Equation (3). Alternatively, a group may be formed by grouping the entire antennas into two, partly by three, and the remaining four, and generate artificial noise considering the number of antennas for each group.

The artificial noise signal generator 128 combines the artificial noise of each group to generate an artificial noise signal. The generated artificial noise signal may be expressed by Equation (3).

A specific example for generating artificial noise has been described above. Basically, a method for generating artificial noise to satisfy Equation (2) is included in the scope of the present invention.

The power allocation processor 130 allocates power to the coded signal generated by the STLC encoder 110 and the artificial noise signal generated by the artificial noise signal generator 120 to generate a transmission signal. At this time, the power allocation processor 130 searches for a power allocation ratio, which is a difference in data rate between the authentication terminal and the non-authentication terminal, using the grid search, and transmits the power allocation The remaining power is allocated to the artificial noise signal, and the combined signal is generated by combining the transmission signal and the artificial noise signal to which the power is allocated.

Then, a transmission signal as shown in Equation (4) described below is generated.

는 최대 송신 전력 제약을 만족하도록 송신 전력을 조절하는 정규화 파라미터이다(

는 행렬 A의 Frobenius norm을 나타냄).Here, X is a signal matrix transmitted by the transmitting apparatus, S denotes a coded information symbol, p denotes a ratio of power allocated to security information transmission among the total transmission power, and 2 × M matrix A denotes an artificial noise signal transmitted to M base station antennas for 2T time.

Is a normalization parameter that adjusts the transmit power to satisfy the maximum transmit power constraint (

Represents the Frobenius norm of matrix A).

When the power is allocated to the STLC coded signal and the artificial noise signal, the secure transmission rate defined by the difference between the transmission rate of the authentication terminal and the non-authentication terminal must be maximized. In case of the authentication terminal, since the main channel H and the number of antennas N _B are known, the transmission rate according to the power allocation ratio p can be easily calculated. Since the transmission rate can not be known accurately for an unauthorized terminal, an estimate of the number of antennas N _E of the wired channel G and the unauthorized terminal is determined, and the expected transmission rate is calculated using the estimate. In general, when the power allocation ratio is p, the secure transmission rate is expressed by Equation 5 described below.

Here, since 0? P <1, the optimal power allocation ratio can be found using the grid search. That is, the value of C _s ( p ) is calculated while changing the value of p from 0 to 1 at a constant interval, and p is selected to maximize C _s ( p ).

The power allocation processor 130 allocates the transmission signal generated as shown in Equation (4) to the transmission antenna after allocating the optimal power.

일 수 있다. The combined signal components for each antenna can be kept constant in transmission power through a normalization operation. In this process, the signals transmitted through the respective transmit antennas at time t are expressed by Equation (4). That is, transmission signals are provided to the transmission antennas at time t. Here, the normalization parameter used for the normalization operation is

Lt; / RTI &gt;

5 is a view for explaining a receiving apparatus for demodulating a transmission signal according to an embodiment of the present invention.

5, a reception apparatus 200 for demodulating a transmission signal according to an embodiment of the present invention includes a plurality of antennas (not shown), a vector conversion unit 210, a vector operation unit 220, (230), and a scaling unit (240).

The vector conversion unit 210 converts a signal received through a plurality of antennas into a vector.

The signals received by the two antennas of the receiving device during a time of 2T are as shown in Equation 6 below.

Here, (n, t) th element r _{B , n , t} of the 2 * 2 matrix R _B denotes a signal received at the nth antenna at time t, W _B denotes a 2 * 2 noise matrix (n, t) th element is represented by w _{B , n , t} .

When the vectorization process of the vector transform unit 210 is performed, the matrix R _B is represented as a vector form, and is expressed by Equation (7) described below.

Here, h _{n , m} denotes the (n, m) th element of H , and denotes the channel gain between the m th base station transmit antenna and the n th authentication terminal receive antenna.

The vector manipulation unit 220 transforms the signal transformed into a vector to demodulate the transmission symbol without CSI for the channel.

That is, the vector manipulation unit 220 transforms the received signal through a vector manipulation process as shown in Equation (8) to demodulate the transmission symbols s ₁ and s ₂ using the received signal expressed by Equation (7).

)을 간접적으로 추정한다.The channel gain estimator 230 estimates a channel gain (hereinafter referred to as &quot; channel gain &quot;) included in the received signal using a blind SNR (Signal-to-Noise Ratio)

) Is indirectly estimated.

The scaling unit 240 estimates a transmission symbol by applying a channel gain estimated by the channel gain estimating unit 230 to a vector transformed by the vector manipulating unit 220. [ That is, the scaling unit 240 estimates transmission symbols s ₁ and s ₂ as shown in Equation (9) described below.

)은 채널 행렬 H를 직접 추정하지 않고, blind SNR (Signal-to-Noise Ratio) 추정 기법을 이용해서 간접적으로 추정할 수 있다. Here, the channel gain (

) Can be indirectly estimated using the blind SNR (Signal-to-Noise Ratio) estimation technique, without directly estimating the channel matrix H.

Therefore, when the base station transmits the security information using the STLC coding scheme, the authentication terminal can demodulate the transmission information by simply scaling r _{B , c} using Equation (9) without using the channel information H.

On the other hand, when the base station transmits STLC using the STLC coding scheme, the reception signal of the non-authentication terminal is expressed by Equation (10).

It is very difficult to reconstruct the transmission symbols s ₁ and s ₂ from R _E since the information about the own channel G and the main channel H can not be known. However, since the structure of the space-time coding matrix S is known, if the temporal change of the channel is very slow, there is a possibility of restoring a part of transmission symbols from the viewpoint of information theory. That is, although the transmission rate of the non-authentication terminal is very low compared to the transmission rate of the authentication terminal, it may be a value greater than zero. In consideration of such a risk, a transmission method combining the STLC coding method and the artificial noise transmission method is used to further lower the transmission rate of the unauthorized terminal.

The present invention has been described with reference to the preferred embodiments. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. Therefore, the disclosed embodiments should be considered in an illustrative rather than a restrictive sense. The scope of the present invention is defined by the appended claims rather than by the foregoing description, and all differences within the scope of equivalents thereof should be construed as being included in the present invention.

100: transmitting apparatus
110: STLC encoder
112:
114: space-
116: Channel operation unit
120: artificial noise signal generator
122: Antenna selection unit
124:
126: artificial noise generator
128: artificial noise signal generating unit
130: Power allocation processor
200: Receiver
210: vector conversion unit
220: Vector control unit
230: channel gain estimating unit
240: Scaling unit

Claims (13)

A plurality of antennas for transmitting and receiving radio signals;
A Space-Time Line Code (STLC) encoder for processing a transmission symbol in a space-time linear coding scheme and outputting a plurality of coded signals for transmission at different times;
An artificial noise signal generator for generating an artificial noise signal removed by STLC decoding; And
And a power allocation processor for allocating power to the coded signal and the artificial noise signal to generate a transmission signal and sequentially transmit the transmission signal through the plurality of antennas,
Wherein the artificial noise signal generator selects at least one or more antennas among a plurality of antennas to group at least two or more antennas and generates an artificial noise signal using channel information and complex noise for each group. . The method according to claim 1,
The STLC encoder includes:
A modulation unit for modulating input data with a predetermined modulation scheme and outputting a transmission symbol;
A space-time coding unit for coding the transmission symbol using a space-time block coding scheme;
And a channel operation unit for generating an encoded signal by applying channel information to the encoded signal. 3. The method of claim 2,
Wherein the encoded signal is a signal of the following formula:
[Mathematical Expression]

Here, S is a coded signal

H denotes a matrix including channel information, and H ^H denotes a conjugate transpose of matrix H. The method according to claim 1,
Wherein the artificial noise signal generator comprises:
An antenna selection unit selecting at least one of the plurality of antennas and an antenna corresponding to a number equal to or less than a half of the number of the plurality of antennas;
A grouping unit for grouping the selected antennas so that at least two antennas are included to generate at least one group;
An artificial noise generator for generating artificial noise using channel information and complex noise for each of the generated groups;
And an artificial noise signal generator for generating an artificial noise signal by combining the artificial noise for each group. 5. The method of claim 4,
Wherein the artificial noise signal satisfies a condition of the following equation so as to be removed by STLC decoding:
[Mathematical Expression]

Here, a _{t , m} is the (t, m) th element of the artificial noise signal matrix A , h _{n , m} is the (n, m) th element of H , Channel gain between antennas. 6. The method of claim 5,
Wherein the artificial noise signal is a signal of the following equation:
[Mathematical Expression]

Here, h _m is an m-th column vector of the main channel H ,

,

Denotes the norm of the vector h _m , and z _n denotes the random noise (Complex Noise) randomly generated. The method according to claim 1,
Wherein the power allocation processor comprises:
A power allocation ratio, which is a difference in data rate between an authenticated receiving apparatus and an unauthorized receiving apparatus, is maximized using a grid search, and a power corresponding to the power allocation ratio Assigns the remaining power to the artificial noise signal, and combines the transmission signal and the artificial noise signal to which the power is allocated, thereby generating a transmission signal. 8. The method of claim 7,
Wherein the transmission signal is a signal of the following equation:
[Mathematical Expression]

Here, X is a signal matrix transmitted by the transmitting apparatus, S is a coded signal, p is a power allocation ratio, A is an artificial noise signal,

being. A transmission symbol is coded in a space-time linear coding scheme, a coded signal is generated by applying channel information to the coded signal, at least one antenna among a plurality of antennas is selected and grouped to include at least two antennas, And a transmitting apparatus for generating an artificial noise signal by using channel information and complex noise, and transmitting the combined signal and the artificial noise signal through the plurality of antennas, A receiving apparatus for receiving a transmitted signal and demodulating the transmitted symbol,
A plurality of antennas;
A vector converting unit for converting a signal received from the transmitting apparatus through the plurality of antennas into a vector;
A channel gain estimator indirectly estimating a channel gain included in the received signal; And
And a scaling unit for estimating the transmission symbol by applying the estimated channel gain to the transformed vector.
Receiving device. 10. The method of claim 9,
Further comprising a vector operation unit for transforming the signal converted into a vector in said vector conversion unit to demodulate the transmission symbol without CSI for the channel. 10. The method of claim 9,
The channel gain estimator may include:
wherein the channel gain is indirectly estimated using a blind SNR (Signal-to-Noise Ratio) estimation technique. A plurality of antennas are provided, the transmission symbols are coded in a space-time linear coding scheme, the coded signals are applied with channel information to generate coded signals, at least one antenna among the plurality of antennas is selected, A transmitter for generating an artificial noise signal using channel information and complex noise for each group, combining the encoded signal and the artificial noise signal, and transmitting the combined signal to the receiver through the plurality of antennas; And
And a receiving apparatus for converting a signal received from the transmitting apparatus through a plurality of antennas provided therein into a vector and demodulating the transmission symbol in the signal converted into the vector using an asynchronous detection technique,
Multi - Antenna Communication System Using Spatio - Temporal Coding. 13. The method of claim 12,
The receiving apparatus indirectly estimates a channel gain included in the received signal using a blind SNR (Signal-to-Noise Ratio) estimation technique, applies the estimated channel gain to the converted vector, And estimating a space-time coding of the multi-antenna communication system.

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