KR20160080061A - Two-way Relay System and Method using Space Frequency Block Coding with Physical Network Coding - Google Patents

Abstract

The present invention relates to a bidirectional station system and a method thereof. According to the present invention, physical network coding (PNC) and a bidirectional transmission scheme of two steps wherein user terminals perform transmission at the same time by using SFBC technology are applied. Therefore, both time efficiency of PNC and diversity of SFBC can be obtained in a circumstance where acquisition of a feedback path is difficult or acquisition of channel information is difficult as reversibility is not reliable. The method of the bidirectional station system includes a multi-connection step, a coding step, and a broadcast step.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-way relay station system and method using spatial frequency block coding and physical network coding,

The present invention relates to a bi-directional relay station system and method, and more particularly, to a bi-directional relay station system and method using spatial frequency block coding and physical network coding.

In the conventional relay station system, in order to exchange information between the two user terminals U _A and U _B using the relay station R, a total of four data transmission processes are required as shown in FIG.

A bidirectional relay station system using network coding is attracting attention in order to reduce the number of such four transmission processes. As shown in FIG. 2, in the first multiple access (MA) process, U _A and U _B simultaneously transmit respective information to the relay station R, and the relay station R receives this information Apply network coding. In the second broadcast (BC) process, the relay station R simultaneously transmits data generated through network coding to U _A and U _B. U _A and U _B can obtain the information of the other party by removing information transmitted from the received information.

At this time, the network coding method applied by the relay station R is analog network coding (ANC) and physical network coding (PNC). In the case of ANC, the relay station R generates network coding information to be transmitted in the BC process by adjusting the amount of power of signals received from both sides. The PNC decodes the information received from both the relay station R and the RNC, XOR) to generate network coding information to be transmitted to the BC process. However, the ANC has a disadvantage that the user terminals need not only channel information between themselves and the relay station (R) but also channel information between the relay station (R) and the counterpart user terminal, and a noise enhancement phenomenon. On the other hand, in the PNC, the user terminals only need to know the channel information between itself and the relay station (R), and the signal is decoded in the relay station (R).

Considering a relay station R having two antennas in a bidirectional relay communication system to which the PNC has this advantage, if the relay station R exchanges channel information between itself and two user terminals with channel reversibility channel reciprocity or a feedback path, a beam capable of deriving the diversity gain of the user terminal can be formed. However, there is a problem in that the relay station R can not form a meaningful beam in a situation where the acquisition of the feedback path is difficult or the channel reversibility is not established at a reliable level and channel information is difficult to obtain.

SUMMARY OF THE INVENTION Accordingly, the present invention has been made in view of the above problems, and it is an object of the present invention to provide a bi-directional relay station communication system in which a plurality of frequency subcarriers such as Orthogonal Frequency Division Multiplexing (OFDM) In the relay of signal transmission between user terminals, space frequency block coding (SFBC) is applied using the quasi-statistical property that the channels between adjacent subcarriers are similar to each other, And it is an object of the present invention to provide a bi-directional relay station system and method capable of forming a beam capable of deriving a diversity gain from a user terminal using space frequency block coding (SFBC) even when channel information is not known.

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 understood by those skilled in the art from the following description.

In order to accomplish the above object, according to one aspect of the present invention, there is provided a method of relaying signals in a two-way relay station apparatus, comprising: receiving a signal transmitted by a plurality of user terminals Connecting step; Extracting transmission target signals transmitted from the plurality of user terminals from the received signals, and coding the transmission target signals according to a physical network coding scheme; And a broadcasting step of simultaneously transmitting the coded signals to the plurality of user terminals using multi-frequency subcarriers, wherein the transmitting of the coded signals causes exchange of a corresponding transmission target signal between the plurality of user terminals .

Wherein the signal relaying method comprises the steps of: simultaneously receiving the signals to be transmitted from the plurality of user terminals and simultaneously transmitting the coded signals to the plurality of user terminals; So as to complete the information exchange between them.

The signal relaying method improves diversity gain according to a spatial frequency block coding scheme using the multi-frequency subcarrier and improves temporal efficiency according to the physical network coding scheme.

과

)을 전송하고 동시에 제2주파수 대역의 부반송파를 이용해

를 전송하는(*는 공액 복소수) 단계를 포함하고, 상기 복수의 사용자 단말들은 각각 상기 브로드캐스트된 신호를 수신하여 단일(unitary) 행렬을 이용해

과

을 획득하고

과

로부터 자기 간섭 제거를 통해 상대방의 전송 대상 신호를 획득하는 것을 특징으로 한다.Wherein the broadcasting step comprises the steps of: using the subcarrier of the first frequency band to generate the coded signals (

and

) And at the same time using subcarriers of the second frequency band

(Where * is a complex conjugate), each of the plurality of user terminals receiving the broadcast signal and using a unitary matrix

and

And

and

And acquires the transmission target signal of the other party through magnetic interference cancellation from the base station.

A bidirectional relay station apparatus according to another aspect of the present invention includes: a receiver for receiving signals transmitted by a plurality of user terminals simultaneously using multiple frequency subcarriers; A coding unit for extracting transmission target signals transmitted from the plurality of user terminals from the received signals and coding the transmission target signals according to a physical network coding scheme; And a transmitter for broadcasting the coded signals to the plurality of user terminals at the same time using a multi-frequency subcarrier, wherein the transmitting of the coded signals causes exchange of a corresponding transmission target signal among the plurality of user terminals .

Wherein the bidirectional relay station apparatus simultaneously receives the signals to be transmitted from the plurality of user terminals and simultaneously transmits the coded signals to the plurality of user terminals, So as to complete the information exchange between them.

The bidirectional relay station apparatus improves diversity gain according to a spatial frequency block coding scheme using the multi-frequency subcarrier and improves temporal efficiency according to the physical network coding scheme.

과

)을 전송하고 동시에 제2주파수 대역의 부반송파를 이용해

를 전송하며(*는 공액 복소수), 상기 복수의 사용자 단말들은 각각 상기 브로드캐스트된 신호를 수신하여 단일(unitary) 행렬을 이용해

과

을 획득하고

과

로부터 자기 간섭 제거를 통해 상대방의 전송 대상 신호를 획득하는 것을 특징으로 한다.The transmitter may be configured to transmit the coded signals using the subcarriers of the first frequency band

and

) And at the same time using subcarriers of the second frequency band

(* Is a complex conjugate), the plurality of user terminals each receive the broadcast signal and use a unitary matrix

and

And

and

And acquires the transmission target signal of the other party through magnetic interference cancellation from the base station.

According to the system and method of the present invention, only the unidirectional relay station system to which the existing SFBC technology is applied is considered. However, in the present invention, the SFNC technique is applied while the physical network coding (PNC) In this case, it is difficult to acquire the feedback path, or the channel reversibility can not be established at a reliable level, so that it is difficult to acquire the channel information. Efficiency and SFBC diversity gain can be obtained.

1 is a diagram for explaining a process in which two end user terminals exchange information with each other using a relay station in a conventional relay station system.
2 is a diagram for explaining a process of exchanging information in a two-way relay station system using general network coding.
3 is a view for explaining a two-way relay station system according to an embodiment of the present invention.
4 is a flowchart illustrating an operation of a two-way relay station system according to an exemplary embodiment of the present invention.
5 is a view for explaining an example of a method of implementing a two-way relay station system according to an embodiment of the present invention.

Hereinafter, some embodiments of the present invention will be described in detail with reference to exemplary drawings. It should be noted that, in adding reference numerals to the constituent elements of the drawings, the same constituent elements are denoted by the same reference numerals whenever possible, even if they are shown in different drawings. In the following description of the embodiments of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the difference that the embodiments of the present invention are not conclusive.

In describing the components of the embodiment of the present invention, terms such as first, second, A, B, (a), and (b) may be used. These terms are intended to distinguish the constituent elements from other constituent elements, and the terms do not limit the nature, order or order of the constituent elements. Also, unless otherwise defined, 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 should be interpreted as having a meaning consistent with the meaning in the context of the relevant art and are to be interpreted in an ideal or overly formal sense unless explicitly defined in the present application Do not.

FIG. 3 is a view for explaining a bidirectional relay station system (or apparatus) 100 according to an embodiment of the present invention. For the purpose of describing the operation of the bi-directional relay station system 100 according to an embodiment of the present invention, reference is made to the flowchart of Fig.

Referring to FIG. 4, a two-way relay station system 100 according to an embodiment of the present invention includes two or more antennas 10 and 20, a receiving unit 110, a coding unit 120, and a transmitting unit 130 do. The components of such a two-way relay station system 100 of the present invention may be implemented by hardware, software, or a combination thereof. Here, it is assumed that there are two antennas 10 and 20 for signal transmission and reception, but the present invention is not limited thereto, and a larger number of antennas can be used for transmission of two or more multi-frequency subcarriers such as OFDM.

First, the functions of the components of the two-way relay station system 100 will be briefly described.

The receiving unit 110 receives signals transmitted through the antennas 10 and 20 by a plurality of user terminals (for example, two user terminals) simultaneously using multiple frequency subcarriers. The coding unit 120 extracts transmission target signals transmitted from the plurality of user terminals from the signals received by the receiving unit 110 and codes corresponding transmission target signals according to a physical network coding scheme (PNC). The transmitter 130 broadcasts signals encoded by the coding unit 120 through the antennas 10 and 20 to the plurality of user terminals simultaneously using a multi-frequency subcarrier. The PNC coded signals can be exchanged between the plurality of user terminals.

The system 100 of the present invention can exchange signals between two user terminals U _A and U _B in accordance with a multiple access (MA) process and a broadcast (BC) process as shown in FIG. a two-way relay system to relay, user terminals (U _a, U _B), a space-frequency block coding (SFBC) is to transmit a multi-frequency sub-carrier signal is applied at the same time, bi-directional relay station by receiving it from the system 100, physical network by transmitting multi-frequency sub-carrier signals by applying the coding (PNC) to the user terminal (U _a, U _B) at the same time, the other side in the space-frequency block coding (SFBC) scheme diversity gain, and physical network coding (PNC) method of So that it is possible to obtain all of the temporal efficiency without acquiring the channel information of the terminal.

)를 두 개의 주파수 부반송파를 이용하여 중계국(R)로 동시에 전송하고, 양방향 중계국 시스템(100)의 수신부(110)는 안테나(10, 20)를 통하여 사용자 단말들(U_A, U_B)가 송신하는 신호를 수신한다(도 4의 S110 참조). 즉, 사용자 단말(U_A)은 두 개의 주파수에서 직교하는 전송 대상 신호들

을 전송하고, 사용자 단말(U_B)은 두 개의 주파수에서 직교하는 전송 대상 신호들

을 전송한다. 여기서 f∈{1,2}이다. In detail, in the multiple access (MA) procedure, the user terminals U _A and U _B each receive two signals

), The two frequencies transmitted sub-carriers at the same time as the relay station (R) used, and a two-way receiver 110 of the relay station system 100, the user terminal through an antenna (10, 20) to (U _A, U _B) is transmitted (See S110 in Fig. 4). That is, the user terminal U _A transmits the transmission target signals

And the user terminal U _B transmits transmission signals to be orthogonalized at two frequencies

Lt; / RTI > Where f? {1,2}.

The user terminal of the signal (y ¹⁾ of a first frequency band to the receiving receiver 110 from the (U _A, U _B) may be represented by a vector, such as Equation 1, the user terminal (U _A, The signal y ^{2 in} the second frequency band received by the receiving unit 110 from U _B can be expressed as a vector as shown in Equation ( ² ). Where n ¹ and n ² are noise in each frequency band and h _A and h _B are channel coefficients indicating channel characteristics between each of the user terminals U _A and U _B and the relay station system 100 .

[Equation 1]

&Quot; (2) "

In this way multiple frequency sub-carrier transmission scheme such as OFDM or the like, the orthogonality so established between the sub-carrier, the coding section 120 of the bi-directional relay station system 100 by using this, is received in this way signals (y ^1, y ^2), the decoding So that the original transmission target signals transmitted by the user terminals can be separated and extracted (refer to S120 in FIG. 4).

,

)에 대하여 브로드캐스트(BC) 과정에서 사용자 단말들(U_A, U_B)로 전송할 물리적 네트워크 코딩(PNC) 방식으로 코드화한 신호들

(

과

)을 생성한다(도 4의 S130 참조).Coding section 120 decodes the extracted received signal (y ^1, y ^2), the decoded signal (for example,

,

(PNC) scheme to be transmitted to the user terminals U _A and U _B in the broadcast (BC)

(

and

(See S130 in Fig. 4).

The method of decoding the received signals y ¹ and y ² in each frequency band includes a nonlinear method including a maximum likelihood detector ML method and a nonlinear method including ZF (Zero-Forcing), MMSE Minimum Mean Square Error) filter method and the like can be used.

(

과

)을 추출하여, 이로부터 자신이 송신한 신호를 제거해 상대방이 송신한 신호를 획득할 수 있도록 디코딩된 신호들을 코드화한다. 예를 들어, U_A가

에서 자신이 송신한 신호(

)를 제거하여(자기간섭 제거) 상대방이 송신한 신호(

)를 얻을 수 있으며, 이와 동시에 U_B 역시

에서

를 제거하여

을 얻을 수 있는 방식으로 설계된 모든 네트워크 코딩 방식이, 물리적 네트워크 코딩(PNC) 방식으로 사용될 수 있다. 예를 들어, 전송 대상 신호 Q에 대하여 소정의 XOR 처리 신호 P에 의한 (Q XOR P)를 전송하고 수신측에서 (Q XOR P)에 다시 P를 이용해 한번더 XOR를 수행하여 본래의 신호 Q를 추출할 수 있다. In addition, the physical network coding (PNC) method is XOR scheme, Modulo method and the like are used, the user terminals (U _A, U _B) a coded signal from the signal a respective transmission

(

and

), Extracts the signal from which it is transmitted, and codes the decoded signals so as to obtain the signal transmitted by the other party. For example, if U _A

The signal transmitted by the user

) Is removed (magnetic interference cancellation) and the signal transmitted by the other party

), While at the same time U _B

in

To remove

Can be used in a physical network coding (PNC) scheme. For example, by transmitting (Q XOR P) by a predetermined XOR processing signal P to the transmission object signal Q and performing XOR again by using P again on the receiving side (Q XOR P), the original signal Q Can be extracted.

을 생성하면, 브로드캐스트(BC) 과정에서 송신부(130)는 서로 다른 각각의 주파수 대역 부반송파를 이용하여

등 관련 신호들을 두 개의 안테나(10, 20)를 통해 사용자 단말들(U_A, U_B)로 동시에 브로드캐스트 전송한다(도 4의 S140 참조). 즉, 두 개의 안테나(10, 20)를 통해 제3주파수 대역의 부반송파를 이용해

과

을 전송하고, 동시에 두 개의 안테나(10, 20)를 통해 제4주파수 대역의 부반송파를 이용해

를 전송한다. *는 공액 복소수(complex conjugate)이다.In this way, the signals encoded by the coding unit 120 in the physical network coding (PNC)

The transmitting unit 130 uses the different frequency band subcarriers in the broadcast (BC)

The like related signals via two antennas (10, 20) of the user terminal to broadcast transmissions at the same time (U _A, U _B) (see S140 in Fig. 4). That is, by using the subcarriers of the third frequency band through the two antennas 10 and 20

and

And at the same time, through the two antennas 10 and 20, using subcarriers of the fourth frequency band

. * Is a complex conjugate.

When the broadcasting process is performed as described above, the signal y _k ¹ received by the user terminals U _k ( _k ∈ {A, B}) in the third frequency band can be expressed by Equation (3) (Y _k ^{2 '} ) received by the user terminals U _k ( _k ∈ {A, B}) in the first to fourth frequency bands may be expressed by Equation (4). Here, n _k ¹ and n _k ² are AWGN (Additive White Gaussian Noise) noise in each frequency band for the user terminals U _A and U _B , and h _{(k, 1)} , h _(k, Is a channel coefficient indicating the channel characteristics between the user terminals U _A and U _B and the first and second antennas 10 and 20.

&Quot; (3) "

&Quot; (4) "

In this case, the conjugate complex number (y _k ² ) together with the expression (3) (y _k ¹ ) and the expression (4) can be expressed in a matrix form as shown in the following expression (5) Equation (6) "

&Quot; (5) "

&Quot; (6) "

과

를 획득하기 위하여, [수학식6]의 신호 벡터(y_k)에

를 곱하는 매치트 필터링(matched-filtering)을 수행한다. 그 결과는 하기의 [수학식 7]과 같다.Accordingly, the user terminals U _k can _{calculate the} received signal vector y _k in Equation (6)

and

(Y _k ) in Equation (6) to obtain the signal vector

Lt; RTI ID = 0.0 > matched-filtering < / RTI > The result is shown in Equation (7) below.

&Quot; (7) "

는 단일(unitary) 행렬이므로, 잡음 벡터의 성질을 변화시키지 않고 수신 신호의 신호 대 잡음비가 유지된다. [수학식7]에서 볼 수 있듯이, 신호의 채널이 사라지고 간단한 형태의 AWGN(Additive White Gaussian Noise) 채널의 형태가 되었고, 서로 다른 주파수의 신호를 간섭 없이 분리할 수 있으므로, U_k는 각 주파수 대역에서

과

을 간단하게 획득할 수 있게 된다. 이렇게 획득된

과

에서 자기 간섭인

과

를 네트워크 코딩의 성질을 이용하여 제거하면 상대방으로부터 온 정보(상대방이 전송한 전송 대상 신호)를 획득할 수 있다. 이에 따라 U_k 간에 해당 전송 대상 신호의 교환이 이루어질 수 있다. here,

Is a unitary matrix, the signal-to-noise ratio of the received signal is maintained without changing the nature of the noise vector. [Equation 7] in, as shown, the channel of the signal disappears and was in the form of a simple form of the AWGN (Additive White Gaussian Noise) channel, to each other it is possible to separate the signals of different frequencies without interference, U _k is the frequency bands in

and

Can be obtained easily. Thus obtained

and

Self interference

and

(The transmission target signal transmitted by the other party) from the other party by using the nature of the network coding. Accordingly, U _k The exchange of the transmission target signal can be performed.

FIG. 5 is a diagram for explaining an example of a method of implementing a two-way relay station system 100 according to an embodiment of the present invention. The bi-directional relay station system 100 according to an embodiment of the present invention may be implemented by hardware, software, or a combination thereof. For example, the computing system 1000 as shown in FIG.

The computing system 1000 includes at least one processor 1100, a memory 1300, a user interface input device 1400, a user interface output device 1500, a storage 1600, And an interface 1700. The processor 1100 may be a central processing unit (CPU) or a memory device 1300 and / or a semiconductor device that performs processing for instructions stored in the storage 1600. Memory 1300 and storage 1600 may include various types of volatile or non-volatile storage media. For example, the memory 1300 may include a ROM (Read Only Memory) and a RAM (Random Access Memory).

Thus, the steps of a method or algorithm described in connection with the embodiments disclosed herein may be embodied directly in hardware, in a software module executed by processor 1100, or in a combination of the two. The software module may reside in a storage medium (i.e., memory 1300 and / or storage 1600) such as a RAM memory, a flash memory, a ROM memory, an EPROM memory, an EEPROM memory, a register, a hard disk, a removable disk, You may. An exemplary storage medium is coupled to the processor 1100, which can read information from, and write information to, the storage medium. Alternatively, the storage medium may be integral to the processor 1100. [ The processor and the storage medium may reside within an application specific integrated circuit (ASIC). The ASIC may reside within the user terminal. Alternatively, the processor and the storage medium may reside as discrete components in a user terminal.

As described above, only the unidirectional relay station system to which the existing spatial frequency block coding (SFBC) technique is applied has been considered. However, in the bidirectional relay station system 100 according to the embodiment of the present invention, the physical network coding (PNC) Simultaneously, it is difficult to acquire the feedback path or establish the reliable channel reversibility by applying the two-way bi-directional transmission method in which two user terminals simultaneously transmit and receive using SFBC technology to complete mutual information exchange. So that it is possible to obtain both the temporal efficiency of the PNC and the diversity gain of the SFBC even in the case where acquisition of the channel information is difficult.

The foregoing description is merely illustrative of the technical idea of the present invention, and various changes and modifications may be made by those skilled in the art without departing from the essential characteristics of the present invention.

Therefore, the embodiments disclosed in the present invention are intended to illustrate rather than limit the scope of the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments. The scope of protection of the present invention should be construed according to the following claims, and all technical ideas within the scope of equivalents should be construed as falling within the scope of the present invention.

The antennas 10,
The receiving unit 110,
Coding section 120,
The transmitter 130,

Claims (1)

A signal relaying method in a bi-directional relay station apparatus,
A multiple access step in which a plurality of user terminals simultaneously receive signals transmitted using multiple frequency subcarriers;
Extracting transmission target signals transmitted from the plurality of user terminals from the received signals, and coding the transmission target signals according to a physical network coding scheme; And
And a broadcasting step of simultaneously transmitting the coded signals to the plurality of user terminals using a multi-frequency subcarrier,
Wherein the transmission of the signal to be transmitted is performed between the plurality of user terminals upon transmission of the coded signals.

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