KR101205996B1 - Method for transmitting/receiving video signal in two-way relaying system - Google Patents

Abstract

The present invention relates to a method for transmitting and receiving a signal in a two-way relaying system consisting of two or more user nodes and a relay node, wherein all user nodes transmit a transmission signal to at least one antenna, and at the relay node Receiving the transmission signal by at least one antenna; converting the received transmission signal into a relay transmission / reception process matrix at the relay node; and converting the signal converted by the relay node according to the transmission / reception process matrix to all user nodes. Broadcasting to the user node, and each user node receives the broadcast signal and cancels self-interference from the received broadcast signal.

Description

How to send and receive signals in two-way relay system {METHOD FOR TRANSMITTING / RECEIVING VIDEO SIGNAL IN TWO-WAY RELAYING SYSTEM}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for transmitting and receiving signals in a two-way relaying (TWR) system, and more particularly, to a method for transmitting and receiving signals in a multi-user TWR environment.

Relay (TWR) system is designed to improve the reliability of signal and widen transmission coverage by relay node located between source node and target node, amplifying or decoding source node signal and regenerating the signal to target node. .

Among the signal transmission methods using such a relay system, there is a half-duplex one-way relay (hereinafter referred to as OWR) transmission method.

This half-duplex one-way relaying (OWR) transmission requires two time slots for data transmission to the destination node, resulting in a half factor frequency efficiency loss.

In order to reduce such frequency efficiency loss, a bidirectional relay (TWR) scheme has been proposed. In this bidirectional relay (TWR) scheme, two nodes wishing to communicate simultaneously transmit a signal, and the relay processes the received signal and broadcasts the signals simultaneously to two nodes, thereby reducing the frequency efficiency degradation caused by the one-way relay (OWR). .

In the conventional techniques for the TWR system having such a high frequency efficiency, a method of maximizing the sum of transmission rates of two nodes in a system composed mainly of two nodes and one or a plurality of relay nodes that want to communicate is mainly studied. In this case, the two nodes focus on removing only self-interference present in the received signal.

However, in a multi-user environment in which a number of node pairs that want to communicate in recent years have been extended to a TWR system, it is desirable to consider not only self-interference but also multiuser interference.

The present invention provides a signal transmission / reception method in a bidirectional relay system that reduces self-interference and multi-user interference when designing a relay transmission / reception process matrix.

In the bidirectional relay system according to an aspect of the present invention for achieving the above objects, the method for transmitting and receiving a signal, all the user nodes to transmit a transmission signal to one or more antennas, and the transmission signal from the relay node to one or more antennas Receiving a signal; converting the received transmission signal into a relay transmission / reception process matrix at the relay node; broadcasting the signal converted according to the transmission / reception process matrix to all user nodes; Receiving, by the user node, the broadcast signal, and canceling self-interference from the received broadcast signal.

According to the present invention, not only self-interference but also multiuser interference can be reduced.

1 is a block diagram illustrating a multi-user bidirectional relay (TWR) system according to an embodiment of the present invention.
2 is a structural diagram of a transceiver of a user node and a relay node constituting a multi-user bidirectional relay (TWR) system according to an embodiment of the present invention.
3 is a graph comparing symbol error rates of the conventional scheme and the proposed scheme when transmitting 8-PSK modulation symbols on a Rayleigh fading channel in a multi-user bidirectional relay (TWR) system having 4 user nodes according to an embodiment of the present invention. .

 In the present invention, a method for overcoming the increase in relay complexity and reduction in diversity order provided by the relay multi-antenna by reducing both self-interference and multi-user interference in designing a relay transmission / reception process matrix is described in detail below. do.

In the present invention, a method of transmitting and receiving at a relay node and a method of processing a received signal at each node for reducing symbol error rates in a multi-user TWR system are described in detail below.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1 is a block diagram illustrating a multi-user bidirectional relay (TWR) system according to an embodiment of the present invention.

(111, 112, 113, 114, 115, 116)와 단일 릴레이 노드(120: R) 구성된다. 여기서, 일반성 상실 없이 서로 데이터를 교환하는 통신 사용자 노드 쌍을 (

,

)이라 가정한다. 1, a multi-user two-way relay (TWR) system according to an embodiment of the present invention basically one or more pair of user nodes to exchange data

(111, 112, 113, 114, 115, 116) and a single relay node 120 (R). Here, a pair of communication user nodes that exchange data with each other without loss of generality (

,

Assume that

All user nodes exchange data with communication counterparts in two stages, multiple access and broadcast. In the multiple access stage, all users transmit a signal to the relay, and the relay processes the received signal and broadcasts it to all user nodes in the broadcasting stage. Therefore, in the multi-user TWR system, not only self-interference caused by signals transmitted from each user node, but also multi-user interference caused by other pairs of user nodes in communication exist.

In the prior art as described above, a method for reducing the above-mentioned multi-user interference has been proposed by transmitting a signal through a code division multiple access scheme and performing power control for each user node. However, this code division multiple access scheme has a disadvantage in that frequency efficiency is lowered.

In addition, in the above-described other conventional technology, all user data is decoded in a relay node, and multi-user interference is reduced by XOR operation of user data bits or pre-coding by a DPC (dirty-paper coding) technique to deliver them in a broadcasting step. However, this approach increases relay complexity because all user data must be restored to the bit level in the relay.

As a method of reducing relay complexity, the prior art has proposed a method of linearly converting a received signal into a transceiver processing matrix and transmitting the signal by a relay transmitting a signal in a broadcasting step. However, this method increases relay complexity and reduces the diversity order provided by the multi-antenna relay node by designing a relay transmit / receive matrix based on reducing both multi-user interference and self-interference at each node, thereby increasing symbol error rate. .

로, 릴레이 노드의 안테나 수는

로 한다. In order to solve this problem, the multi-user TWR system of FIG. 1 according to an embodiment of the present invention will be described in detail. For convenience of description, various variables are defined. First, the number of antennas on your node

The number of antennas in the relay node is

Shall be.

로 할 때, 사용자 노드

에서 릴레이 노드(120: R)로의 채널 응답을 크기가

×

인 행렬

로 나타낼수 있으며, 여기서,

는 사용자 노드

의 i 번째 송신 안테나에서 릴레이 노드(120: R)로의 j번째 수신 안테나로의 채널 응답이다. In addition, user nodes

When doing so, the user node

Channel response to relay node 120 (R)

×

Phosphorus matrix

Where,

Is your node

Is the channel response from the i th transmit antenna to the j th receive antenna from the i th transmit antenna to the relay node 120 (R).

로의 채널 응답은

로 나타낼 수 있으며, 여기서 (?) ^T 는 행렬의 전치(transpose)를 나타낸다. Thus, the user node in the relay node 120 (R)

Channel response to

Where ( ? ) ^T represents the transpose of the matrix.

의 송신 전력은

, 릴레이 노드 송신 전력은

로 표기한다. In addition, each user node

Transmit power of

Relay node transmit power

.

가 통신하고자 하는 상대 노드를

(여기서, k가 짝수이면 k'=k-1이고 k가 홀수이면 k'=k+1임)로 가정할 때, 사용자 노드 가 상대 노드로 전송하는 송신 심볼을

로 한다.User node

To communicate with the other node

(Where k ' = k -1 if k is even and k ' = k +1 if k is odd).

Shall be.

는 크기가

×1 송신 빔형성 벡터

로 송신 심볼

를 전송한다. 그에 따른 릴레이 노드에서 안테나에 수신된 신호를 벡터로 표현하면 아래의 수학식 1과 같다.
User Nodes in the Multiple Access Phase

Is the size

× 1 transmission beamforming vector

Send symbol to

. In the relay node, the signal received by the antenna is expressed in vector as shown in Equation 1 below.

은 크기가

×1인 릴레이 노드에서 수신 안테나의 잡음을 나타내는 잡음 벡터이다.
here,

Is the size

A noise vector representing the noise of a receiving antenna at a relay node of × 1.

×

인 송수신 처리 행렬 F로 변환한 신호

를 방송 단계에서 모든 사용자 노드에게 전송한다. 이때 사용자 노드

에서의 수신 신호는 아래의 수학식 2와 같다.
In the prior art, the size of the relay node received signal

×

Signal converted to the transceiving matrix F

Is transmitted to all user nodes in the broadcast phase. The user node

The received signal in is equal to Equation 2 below.

는 크기가

×1인 사용자 노드

에서의 수신 빔형성 벡터이고,

는 크기가

×1인 사용자 노드

에서 수신 안테나 잡음 벡터이다.
here,

Is the size

× 1 user node

Is the reception beamforming vector at

Is the size

× 1 user node

Is the receive antenna noise vector.

는 수신 심볼

에서 상대방 노드의 송신 심볼

를 검출한다. 이때, 상기 수학식 2에서 볼 수 있듯이, 사용자 노드

의 수신 신호에는 자신이 보낸 송신 심볼

에 의한 자가 간섭과 다른 사용자 노드 쌍의 송신 심볼

에 의한 다중사용자 간섭이 함께 존재함을 볼 수 있다.
User node

Receive symbol

Transmit symbol of the other node in

. At this time, as shown in Equation 2, the user node

Received signal contains the transmitted symbol

Self-interference Caused by Different User Node Pairs

It can be seen that there is a multi-user interference by.

와 수신 빔형성 벡터

는 송신 시 채널상태정보유무 및 정보 내용에 따라 균일 (uniform) 빔형성 벡터

, 고유 빔형성(eigen beamforming)

(여기서,

는 채널

를

로 SVD(singular value decomposition)했을 때

의 최대 고유치에 해당하는 역 벡터, 그리고 안테나 선택 기법에 의해

,

의 오직 한 원소만 1이고 다른 원소는 0인 벡터를 적용할 수 있다.
In this case, the transmission beamforming vector

And receive beamforming vectors

Uniform beamforming vector depends on channel status information and information content.

Eigen beamforming

(here,

Channel

To

SVD (singular value decomposition)

By the inverse vector corresponding to the maximum eigenvalue of

,

You can apply a vector whose only element is 1 and the other element is 0.

로 나타내면 아래의 수학식 3과 같다.Multi-user reception vector by collecting received signals of all user nodes for easy description of the prior art and the technique proposed by the present invention.

It is represented by Equation 3 below.

는 모든 사용자 노드 송신 심볼로 구성된 다중사용자 송신 심볼 벡터이고,

는 모든 사용자 노드와 릴레이 노드 사이의 채널 응답 행렬로 구성된 다중사용자 채널 행렬이고,

은 모든 사용자 노든 잡음 벡터로 구성된 다중사용자 잡읍 벡터이고, here,

Is a multiuser transmit symbol vector of all user node transmit symbols,

Is a multiuser channel matrix consisting of the channel response matrix between all user nodes and relay nodes,

Is a multiuser population vector of all user nord noise vectors,

는 모든 사용자 노드의 송신 빔형성 벡터로 구성된 다중사용자 송신 빔형성 행렬이고,

는 모든 사용자 노드의 수신 빔형성 벡터로 구성된 다중사용자 수신 빔형성 행렬이다. 그리고

는 원소가 모두 영인 길이가

인 벡터이다.

Is a multi-user transmit beamforming matrix composed of transmit beamforming vectors of all user nodes,

Is a multi-user receive beamforming matrix composed of receive beamforming vectors of all user nodes. And

Is a zero length element

Phosphorus vector.

로부터 모든 사용자 노드의 상대방 송신 심볼를 나타내는 벡터

를 잘 검출할 수 있도록 릴레이 송수신 처리 행렬

를 설계하였다. 여기서,

는 통신 사용자 노드 쌍 사이의 심볼 교환을 나타내는 크기가

인 블록 대각 행렬로 k 번째 부분 대각 행렬이 2x2 행렬

이다.
Conventionally, multi-user received signal vector

A vector representing the far-end transmission symbol of all user nodes from

Relay transmission and reception process matrix to detect the

Was designed. here,

Is a size representing the symbol exchange between a pair of communicating user nodes

Block diagonal matrix with k-th partial diagonal matrix being 2x2 matrix

to be.

를 설계하는 기준으로 ZF (zero forcing) 기준 또는 MMSE(Minimum Mean Square Error)기준을 적용하였는데, ZF 기준으로 얻은 릴레이 송수신 처리 행렬은 아래의 수학식 4에, MMSE 기준으로 얻은 릴레이 송수신 처리 행렬은 아래의 수학식 5와 같다.
In the conventional relay transmission and reception process matrix

The ZF (zero forcing) criterion or the minimum mean square error (MMSE) criterion was applied as a design criteria. The relay transmit / receive processing matrix obtained based on ZF is shown in Equation 4 below. Equation 5 is as follows.

는 무어-판로즈 의사 역행렬 (Moore-Penrose pseudo inverse)이고,

는

를 적용할 때 릴레이 송신 전력 제한 조건을 만족시키는 상수이다.
here,

Is the Moore-Penrose pseudo inverse,

The

This constant satisfies the relay transmission power constraint when applying.

는 행렬의 허미션(Hermitian),

는 conjugate, here,

Is the Hermitian of the matrix,

Is conjugate,

는 크기가

×

인 항등 행렬,

는 각 사용자 노드의 각 수신 안테나에서의 복소 잡음 분산,

는 k번째 원소가 사용자 노드 에서의 송신 전력으로 구성된 대각 행렬, 그리고

는

적용 시 릴레이 송신 전력 제한 조건을 만족시키는 상수이다.

Is the size

×

Identity matrix,

Is the complex noise variance at each receive antenna at each user node,

Is a diagonal matrix whose kth elements are the transmit powers at the user nodes, and

The

Constant for satisfying the relay transmission power constraint when applied.

According to the prior art, when the relay transmission / reception processing matrix is applied to Equation 4 or Equation 5, the number of relay antennas must be at least 2 K −1 to remove multi-user interference and self-interference to provide performance.

The present invention proposes a scheme for separating self-interference cancellation and multi-interference cancellation to provide performance even when the number of relay antennas is 2 K -2. That is, in the present invention, the relay node transmits and receives a relay transmission / reception process matrix that does not consider self-interference, and removes self-interference by using transmission symbols known to each user node.

는 아래의 수학식 6에서와 같이 상기 수학식 2의 수신 신호로부터 자가 간섭을 제거한 뒤 상대방 노드의 송신 심볼

를 검출한다. User node according to one embodiment of the present invention

Is a transmission symbol of the other node after removing self interference from the received signal of Equation 2 as shown in Equation 6 below.

.

는 기존과 비슷하게 아래의 수학식 7과 같은 구조를 적용한다.
In the present invention, the transmission and reception processing matrix applied by the relay node when the self-interference cancellation is applied in the user node.

Similarly to the above, the following Equation 7 is applied.

는 크기가 인 수신 필터 행렬,

는 크기가 인 송신 필터 행렬,

는 대각에서의 k째 부분행렬이 인 블록 대각 행렬이며,

는 릴레이 전력 제한

을 만족시키는 상수로 다음과 같이 구할 수 있다.here,

Is a receive filter matrix of size,

Is a transmit filter matrix of size,

Is a block diagonal matrix with kth submatrix at diagonal,

Relay power limit

The constant that satisfies can be obtained as

,

,

이고, 는 행렬의 trace를 뜻한다.
here,

Is the trace of the matrix.

는 사용자 노드가 상기 수학식 3에서와 같이 자가 간섭을 제거하는 것을 고려하여 릴레이 노드에서 자가 간섭을 고려하지 않고 수신 필터 행렬

를 설계하는 것이다. 릴레이 노드에서 수신 필터 적용 시의 출력 벡터

의 k번째 원소에 자가 간섭이 없다는 가정 하에 각 사용자 노드의 수신 신호대잡음비를 최대로 하는 최적 결합 (optimal combining) 수신 필터 행렬

를 적용할 수 있다. 이와 같은 수신 필터 행렬

의 k번째 열은 아래의 수학식 8과 같다 Relay node processing matrix proposed by the present invention

Receive filter matrix without considering self-interference at relay node in consideration of user node canceling self-interference as in Equation 3 above

To design. Output vector when receiving filter is applied in relay node

Optimal combining receive filter matrix that maximizes the received signal-to-noise ratio of each user node, assuming that there is no self interference in the kth element of

Can be applied. Receive filter matrix like this

The kth column of is equal to the following Equation 8

는 자가 간섭을 제외한 다중사용자 간섭과 배경 잡음의 분산 행렬이다.
here,

Is a variance matrix of multi-user interference and background noise excluding self-interference.

이 각각의 목적 사용자 노드에 잘 전달될 수 있도록 아래의 수학식 9의 다중 사용자 수신 신호의 간섭을 줄이도록 설계한다.
On the other hand, the transmit filter matrix B is the output of the receive filter matrix.

This is designed to reduce the interference of the multi-user reception signal of Equation 9 below so that each of the target user node can be transmitted well.

In an embodiment of the present invention for achieving the above object, the transmission filter matrix of Equation 10 below may be applied as ZF reference, and in another embodiment, the transmission filter matrix of Equation 11 below MMSE criterion may be applied. Applicable

FIG. 2 is a block diagram illustrating an apparatus for transmitting and receiving a user node and a relay node in a two-way relaying system including two or more user nodes and a relay node according to an embodiment of the present invention.

Referring to FIG. 2, a two-way relaying system according to an embodiment of the present invention includes a user node 2100 and a relay node 2200.

First, the user node 2100 may include one or more antennas 2111, 2112, and 2113, a modulator 2121 that outputs a transmission symbol corresponding to an information bit, and a transmission symbol that is output from the modulator 2121. A corresponding transmission beamformer 2122 and a duplexer 2130 for transmitting the output of the transmission beamformer 2122 to the antenna in a multiple access step or receiving a signal from the antenna in a broadcast step; A reception beamformer 2141 for linearly combining the signals received by the antenna, a self interference canceller 2142 for canceling self interference at the output of the reception beamformer 2141, and the self interference canceller 2142 And a demodulator 2143 for detecting the transmission symbol of the counterpart node from the output of the.

The relay node 2200 receives one or more antennas 2211, 2212, and 2213, the signals received by the antennas 2211, 2212, and 2213 in a multiple access stage, and the antennas 2211, 2212, and 2213 in a broadcast stage. A duplexer 2220 which transmits a signal to the antenna, and a relay transmission / reception processor 2230 which linearly converts a received signal received by the antennas 2211, 2212, and 2213 in the multiple access step to generate a signal to be transmitted in the broadcasting step. It includes.

, 데이터 교환기

, 송신 필터

와 신호 증폭기

를 포함할 수 있다. 이때 수신 필터

는 자가 간섭을 제외한 신호대간섭잡음비를 최대로 하는 전술한 수학식 8을 하드웨적으로 구현한 최적 결합기로 구현되고, 송신 필터

는 ZF 방식에 의한 전술한 수학식 9를 하드웨어적으로 구현하는 ZF 송신 필터로 구현되거나 MMSE (Minimum Mean Square Error) 방식에 의한 전술한 수학식 10을 하드웨어적으로 구현하는 MMSE 송신 필터로 구비될 수 있다.According to one embodiment of the invention, the relay transmission and reception processor 2230 provided in the relay node 220 of FIG. 2 is a reception filter for implementing the above equation (7) in hardware

Data exchanger

Transmission filter

And signal amplifier

. ≪ / RTI > Receive filter

Is an optimal combiner that implements the above Equation 8 to maximize the signal-to-interference noise ratio excluding self-interference, and is a transmission filter.

May be implemented as a ZF transmission filter for hardware implementation of the above-described equation (9) by the ZF method or may be provided as an MMSE transmission filter for hardware implementation of the above equation (10) by the MMSE (Minimum Mean Square Error) method have.

In addition, according to an embodiment of the present invention, the transmit beamformer 2122 and the receive beamformer 2141 provided in the user node 2100 of FIG. 2 may be configured as devices having the same weight for each antenna based on uniform beamforming. Can be. In addition, the transmit beamformer 2122 and the receive beamformer 2141 perform a weighting process with a vector that derives a maximum singular value for the channel response between the user node 2100 and the relay node 2200. Only the antenna has a weight of 1 and the remaining antennas may be configured as a device having a weight of 0.

에 따른 심볼오류율을 종래의 기술과 본 발명이 제안하는 기술을 비교하여 보여주는 그래프이다. 3 is in when sending all users transmit symbols to 8-PSK scheme in the exemplary communication nodes in the example pair of K = 2 (that is, a total user number of nodes 2 K = 4) TWR system of the present invention, the user node Signal to noise ratio

Is a graph showing a symbol error rate according to a comparison between the conventional technique and the technique proposed by the present invention.

로 동일하고 릴레이 송신 전력은

이다. Referring to Figure 3, the transmit power of all user nodes

Same as the relay transmit power

to be.

In FIG. 3, 'ZF-ZF' and 'MMSE-MMSE' are performances of a method of applying a relay transmission / reception processing matrix of the ZF criterion of Equation 4 and the MMSE criterion of Equation 5 described above in the prior art, respectively. 'ZF-OC' and 'MMSE-OC' are performances when the ZF-based transmit filter matrix of Equation 10 and the MMSE-based transmit filter matrix of Equation 11 are applied in the technique proposed by the present invention. Respectively.

와 릴레이 안테나 수

의 조합이

×

= 2×4인 경우와

×

= 2×6인 경우 모두 종래의 기술 (‘ZF-ZF'와 `MMSE-MMSE')보다 본 발명이 제안하는 기술 ('ZF-OC'와 'MMSE-OC')의 심볼오류율이 크게 향상된다. 이는 본 발명이 제안하는 기술이 동일한 릴레이 안테나 수에 대해 제공 가능한 다양성 차수가 높기 때문이다. As can be seen from Figure 3, the number of user node antennas

And relay antenna number

The combination of

×

= 2 × 4

×

In the case of = 2 × 6, the symbol error rate of the technique proposed by the present invention ('ZF-OC' and 'MMSE-OC') is significantly improved compared to the conventional techniques ('ZF-ZF' and 'MMSE-MMSE'). . This is because the technique proposed by the present invention has a high degree of diversity that can be provided for the same number of relay antennas.

Claims (2)

Signal transmission and reception method in a two-way relaying system consisting of two or more user nodes and relay nodes.
All user nodes transmitting transmit signals to one or more antennas;
Receiving the transmission signal at one or more antennas at the relay node;
Converting the received transmission signal into a relay transmission / reception process matrix at the relay node;
The relay node broadcasting a signal converted according to the transmission / reception processing matrix to all user nodes;
Wherein each user node receives the broadcasted signal to cancel self-interference from the received broadcasted signal,
The relay transmit / receive process matrix includes a transmit filter matrix and a receive filter matrix,
The reception filter matrix of the relay transmission and reception processing matrix is a signal transmission and reception method in a two-way relaying system, characterized in that the optimal coupling matrix is applied to maximize the signal-to-interference noise ratio excluding self interference. delete

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