KR101582880B1 - METHOD FOR amplifying and forwarding signal - Google Patents

Abstract

The present invention provides a signal amplification retransmission method in a repeater. The signal amplification retransmission method includes: a repeater receiving signals from a transmitter; Estimating a channel with the transmitter using the pilot signal of the transmitter within the received signals; Removing the pilot signal within the received signals; Amplifying the signals from which the pilot signal is removed according to the estimated channel; And transmitting the pilot signal of the repeater in the amplified signals.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal amplifying and forwarding method,

The present invention relates to a signal relaying method.

Many wireless communication technologies have been proposed for high-speed mobile communication today.

In order to accommodate such high-speed communications and higher call volumes, the radius of the cells is gradually decreasing. In this case, a centralized design using the current wireless network design method is expected to be impossible. Therefore, the next generation communication system should be distributedly controlled and constructed, and actively cope with environmental changes such as addition of a new base station.

A repeater has been proposed for this purpose.

1 shows a conventional relay system.

As shown in FIG. 1, one or more terminals 11, 12, and 13 exist in the area of the base station 20.

At this time, a specific one or more terminals among the one or more terminals 11, 12, 13 may operate as a repeater (or relay). The terminal operating as the repeater has a good channel environment and a high channel gain on average.

That is, when a terminal having a good channel environment operates as a repeater, another terminal having a poor channel environment can transmit / receive data to / from the base station through a terminal operating as the repeater.

A method of utilizing a terminal in a cellular system as a repeater enables improvement of transmission performance. That is, a terminal acting as a repeater can amplify a data signal and transmit it to each receiving terminal so that the terminal can communicate with the base station more stably to the terminal existing in the coverage of the base station, thereby improving the transmission performance.

On the other hand, there are two techniques in which each repeater relays signals. That is, there are an amplify and forward (AF) scheme and a decode and forward (DF) scheme.

In the case of the encoding retransmission technique, the repeater decodes the signal received from the transmitter, and re-encodes the signal, and transmits the generated message to the receiver. However, in the case of such an encoding retransmission technique, since the message signal of the transmitter is decoded and re-encoded by the repeater, the signal is less affected by the noise, but the hardware complexity increases due to decoding of the transmitter message signal.

In the case of the amplification retransmission technique, the repeater amplifies the message signal received from the transmitter to a predetermined size and then retransmits the signal. Since the amplification retransmission technique does not have a signal processing process according to decoding, it is possible to implement a simple hardware. However, since noise added to the repeater is transmitted to the receiver, performance deterioration occurs in a low signal-to-noise ratio (SNR) environment .

Such an amplification retransmission technique has been studied more recently due to the advantages of low complexity and processing delay in actual implementation as compared with the above-mentioned coding retransmission (DF).

However, according to the above-described amplification retransmission technique, in order to decode the signal received from the repeater, the receiver must not only estimate the channel between itself and the repeater but also know the channel between the transmitter and the repeater.

In the case of the above-described prior art amplification retransmission (AF) technique, the receiver must know not only the channel of the repeater but also the channel of the relay period with the transmitter, but this is practically a technical difficulty.

In order to allow the receiver to estimate the channel of the transmitter and the relay period, the transmitter and the repeater each use a subcarrier and a pilot signal.

However, a scheme in which a transmitter and a repeater each use a subcarrier and a pilot signal is very inefficient in terms of a channel and causes a waste of radio resources.

Accordingly, an object of the present invention is to solve the above-mentioned problems.

In particular, it is an object of the present invention to allow a receiver to estimate only the channel between repeaters in an amplification retransmission (AF) technique.

In order to achieve the above object, the present invention provides a signal amplification retransmission method in a repeater. The signal amplification retransmission method includes: a repeater receiving signals from a transmitter; Estimating a channel with the transmitter using the pilot signal of the transmitter within the received signals; Removing the pilot signal within the received signals; Amplifying the signals from which the pilot signal is removed according to the estimated channel; And transmitting the pilot signal of the repeater in the amplified signals.

In order to achieve the above object, the present invention provides a repeater. The repeater comprising: a receiver for receiving signals from a transmitter; Estimating a channel with the transmitter using the pilot signal of the transmitter in the received signals, removing the pilot signal in the received signals, A processor for amplifying the pilot signal of the repeater according to a channel and for incorporating the pilot signal of the repeater into the amplified signals; And a transmitter for transmitting a signal including the pilot signal of the repeater under the control of the processor.

The position of the pilot signal of the transmitter and the position of the pilot signal of the repeater may be the same. Or the position of the pilot signal of the transmitter and the position of the pilot signal of the repeater may be different from each other.

The processor may remove the pilot signal of the transmitter from the signals and then move a signal that is temporally subsequent to the pilot signal of the transmitter to a position of the pilot signal.

In the amplification retransmission method according to the present invention, a receiver estimates only a channel between repeaters, thereby reducing complexity. In addition, the amplification retransmission method according to the present invention uses the pilot signal only once, thereby effectively utilizing radio resources. In addition, the amplification retransmission method according to the present invention does not deteriorate the performance, while allowing the pilot signal to be used only once.

The present invention is not limited to this, and can be applied to all communication systems to which the technical idea of the present invention can be applied, for example, 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE), IEEE standard, Ad-Hoc network.

It is noted that the technical terms used herein are used only to describe specific embodiments and are not intended to limit the invention. It is also to be understood that the technical terms used herein are to be interpreted in a sense generally understood by a person skilled in the art to which the present invention belongs, Should not be construed to mean, or be interpreted in an excessively reduced sense. Further, when a technical term used herein is an erroneous technical term that does not accurately express the spirit of the present invention, it should be understood that technical terms that can be understood by a person skilled in the art are replaced. In addition, the general terms used in the present invention should be interpreted according to a predefined or prior context, and should not be construed as being excessively reduced.

Also, the singular forms "as used herein include plural referents unless the context clearly dictates otherwise. In the present application, the term "comprising" or "comprising" or the like should not be construed as necessarily including the various elements or steps described in the specification, Or may be further comprised of additional components or steps.

Furthermore, terms including ordinals such as first, second, etc. used in this specification can 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.

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, but other elements may be present in between. 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.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings, wherein like reference numerals refer to like or similar elements throughout the several views, and redundant description thereof will be omitted. In the following description, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail. It is to be noted that the accompanying drawings are only for the understanding of the present invention and should not be construed as limiting the scope of the present invention. The spirit of the present invention should be construed as extending to all modifications, equivalents, and alternatives in addition to the appended drawings.

Hereinafter, the term 'terminal' is used, but the terminal may be referred to as a user equipment (UE), a mobile equipment (ME), or a mobile station (MS). The terminal may be a portable device such as a cellular phone, a PDA, a smart phone, or a notebook, or may be a portable device such as a PC or a vehicle-mounted device.

2

Figure 2 shows an amplification retransmission (AF) scheme in a MIMO-based system.

As can be seen with reference to FIG. The MIMO-based system includes a transmitter 200, a repeater 300, and a reception terminal 110.

The transmitter 200 is represented by the abbreviation S as a source, the repeater 300 is represented by R as an abbreviation of Relay, and the receiving terminal 110 is represented by D as an abbreviation of Destination .

The transmitter 200, the repeater 300, and the reception terminal 110 have Nt, Nr, and Nd antennas, respectively.

An H channel exists between the transmitter 200 and the repeater 300 and a G channel exists between the repeater 300 and the receiver terminal 110. The H channel and the G channel may assume flat fading based on orthogonal frequency division multiplexing (OFDM). All the elements of the H channel and the G channel are i.i.d. complex Gaussian random variable.

2, communication between the transmitter 200 and the reception terminal 110 is relayed by one repeater 300, and each input / output is represented by the following equation.

y _R = HFx + n ₁

y _D = GQHFx + GQn ₁ + n ₂

y _D = W _D y _D = W _D GQHFx + W _D GQn1 + WDn ₂

Where F is the filter used in the transmitter 200 and Q and W _D are the linear filters used between the repeater 300 and the receiving terminal 110 respectively. And n1 and n2 are noise.

On the other hand, the receiving terminal 110 optimized in the MMSE optimization criterion can be defined by the following equation.

here

As shown in Equation (2), in the case of the conventional amplification re-transmission scheme, the receiving terminal 110 should be able to know both efficient GQHF and GQ.

를 사용했을 경우 error matrix 는 다음과 같이 주어진다. In the receiving terminal 110,

, The error matrix is given by

R _E = (F ^H H ^H Q ^H G ^H R _n ^-1 GQHF + σ _x ^-2 I) ^-1

As described above, the channel estimation in the system shown in FIG. 2 is performed based on the model shown in FIG.

Figure 3 shows the system shown in Figure 2 as a matrix model.

As can be seen with reference to Figure 3, the transmitter 200 may be viewed as having a F filters, the repeater 300 can be seen to have the Q filter, the receiving terminal 110 W _D Filter. ≪ / RTI >

Then, the signal transmitted from the transmitter 200 undergoes the H channel, and noise n1 is added to reach the repeater 300. The signal transmitted by the repeater 300 undergoes a G channel, and noise n2 is added to reach the receiving terminal 110.

At this time, in order to decode the received signal, the receiving terminal 110 has to know both the H channel and the G channel in the related art as described above.

3, when the transmitter 200 transmits not only a subcarrier for its own pilot but also an empty subcarrier, the repeater 300 transmits its empty pilot signal to a position of the empty subcarrier, The signal is transmitted and transmitted.

Then, the receiving terminal 110 estimates the H channel between the transmitter 200 and the repeater 300 through the pilot signal of the transmitter 200.

However, such a technique causes waste of radio resources as described above.

Another aspect of the present invention is that the receiving terminal 110 amplifies a noise component in the pilot signal of the transmitter 200 when the repeater 300 amplifies the signal so that the distance between the transmitter 200 and the repeater 200 There was a difficulty in accurately knowing the H channel.

Hereinafter, FIG. 4 illustrates a relaying method of the present invention in which the receiving terminal 110 can estimate only the G channel.

Figure 4 shows a system according to the invention in a matrix model.

필터를 가지는 것으로 볼 수 있고, 상기 수신 단말(110)은 W_D 필터를 가지는 것으로 볼 수 있다.As can be seen with reference to Figure 4, the transmitter 200 may be viewed as having a filter F, and the repeater 300 is L ^R Q filters of filter

Filter, and the receiving terminal 110 can be regarded as having a W _D filter.

The signal transmitted from the transmitter 200 undergoes an H channel and arrives at the repeater 300 as a yR signal added with noise n1. The signal transmitted by the repeater 300 passes through the G channel, and noise n2 is added to reach the receiving terminal 110 as a yD signal.

Here, SVD (Singular Value Decomposition) of each channel is defined as follows.

Y = H _h ^H _h ΦV

G = U _g ^H _h ΩV

Relative-Destination Joint Optimal Design between the transmitter, the relay, and the receiving terminal is as follows.

는 다음과 같은 형태를 가짐을 증명할 수 있다.Optimal relay filter using Convex optimization theory

Can be proved to have the following form.

와

은 Relay power normalizing 상수와 전체 중계기의 전송 파워를 각각 의미한다.Where B and L _R correspond to transmit Wiener filter and receive Wiener filter (R-WF), respectively.

Wow

Denotes the relay power normalizing constant and the transmission power of the entire repeater, respectively.

는 두 개의 개별적인 에러 행렬(error matrix)의 합으로 나타내어 질 수 있다.Using this result, the existing error matrix (error matrix)

Can be expressed as the sum of two separate error matrices.

The problem formulation is given as follows.

는 Relay precoder

에 포함되어 있다고 가정하므로

이라 두어도 무방하다.

는 다음과 같이 정의될 수 있다.Here, the relay power normalizing constant

Relay precoder

And therefore,

.

Can be defined as follows.

),

는 identity matrix (

)로 근사 될 수 있다.In real situations (

),

Identity matrix (

). ≪ / RTI >

Therefore, the problem formulation is corrected as follows.

와

는 다음과 같은 form 을 가진다고 가정할 수 있다.therefore

Wow

Can be assumed to have the following form.

We can solve this problem by solving and solving the closed form solution as below. This solution is an optimal solution in high signal-to-noise ratio (SNR).

의 i번째 대각 엘리먼트를 의미한다. Where r _i is

Quot; i "

, 즉 receiver Wiener filter (R-WF) 를 사용하였을 경우,

는 다음과 같이 수정될 수 있다.On the other hand, the receiver of the receiving terminal 110 receives the optimal relay filter formula

, Ie receiver Wiener filter (R-WF)

Can be modified as follows.

는 identity matrix (

) 에 근접하기 때문에,

는 다음과 같이 근사될 수 있다.As mentioned before, in real situations

Identity matrix (

),

Can be approximated as follows.

를 사용할 경우

의 경우와는 달리 첫 번째 채널

에 대한 정보는 필요로 하지 않는다. Above

If you use

Unlike the case of the first channel

Information is not required.

의 경우 high SNR (

) 에서 optimal 에 근접하며 Simulation 결과를 통해서 low SNR 영역에서도 최적의 경우에 비하여 성능 열화가 크지 않음을 확인할 수 있다.

The high SNR (

) And it is confirmed that the performance degradation is not large compared with the optimal case in the low SNR region through the simulation result.

4, the repeater 300 estimates the channel with the transmitter 200 through the pilot of the transmitter 200 on the received subcarrier. The repeater 300 removes (punctures) the pilot of the transmitter 200, amplifies the pilot-removed signal of the transmitter 200 according to the estimated channel, and outputs the punctured position And includes the pilot of the repeater 300 and transmits it to the receiving terminal 110. At this time, the position of the pilot signal of the transmitter and the position of the pilot signal of the repeater may be the same. Or the position of the pilot signal of the transmitter and the position of the pilot signal of the repeater may be different from each other. For example, if the pilot signal of the transmitter is located at the third position, the next data is shifted to the third position where the pilot signal is removed. And the pilot signal of the repeater may be included in the sixth position.

As described above, in the repeater 300 according to the present invention, the receiving terminal 110 estimates only the G channel between the repeaters 300, and the repeater 300 and the transmission period It is not necessary to estimate the H channel of the channel. In addition, since only one pilot signal and subcarriers are used without consuming two pilot and subcarriers, the efficiency of radio resources can be increased.

FIG. 5 shows the BER performance results in the 4QAM normalization model of the amplification retransmission technique of the present invention. And FIG. 6 shows the results of the 16QAM amplification retransmission technique of the present invention. And FIG. 7 shows the amplification retransmission technique of the present invention as a gain according to MSE (Mean Squared Error).

As can be seen with reference to FIG. 5, the amplification retransmission technique (SRD-JB) according to the present invention does not deteriorate the performance of the conventional technique (RD-JM). Also, it can be seen that there is no performance deterioration even though the receiving terminal 110 uses the D-sub filter which estimates only the G channel.

That is, the technique proposed by the present invention enables the repeater 300 and the receiving terminal 110 to achieve optimum performance even when only the channel information corresponding to the repeater 300 and the receiving terminal 110 is known.

)만 아는 경우로써,

의 가정하에 중계기(300)의 잡음(n1)을 무시한 채 검출을 수행한 경우에 해당한다. 또한 SRD-JB DF는 중계기(300)에서 부호화재전송(DF) 방식으로 시뮬레이션한 결과이다. H 채널과 G 채널 각각에 대해서 conventional point-to-point MIMO 방식에서의 joint MMSE (ARITH-BER) 기법을 적용하였다.Also, the illustrated SRD-JB DisrgN indicates that the receiving terminal 110 transmits a pilot signal

As a result,

And the noise (n1) of the repeater 300 is ignored. Also, the SRD-JB DF is the result of simulation by the repeater 300 in the encoding retransmission (DF) scheme. The joint MMSE (ARITH-BER) scheme in the conventional point-to-point MIMO scheme is applied to each of the H channel and the G channel.

Referring to FIG. 6, a result of 16 QAM is shown, and the technique proposed by the present invention can be confirmed regardless of the modulation-level.

Also, FIG. 7 shows the gain in MSE (Mean Squared Error) and shows almost no performance deterioration even when using D-Sub.

The method according to the present invention described so far can be implemented in software, hardware, or a combination thereof. For example, the method according to the present invention may be stored in a storage medium (e.g., mobile terminal internal memory, flash memory, hard disk, etc.) Lt; / RTI > in a software program that may be executed by a processor or other device.

While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, May be modified, modified, or improved.

1 shows a conventional relay system.

Figure 2 shows an amplification retransmission (AF) scheme in a MIMO-based system.

Figure 3 shows the system shown in Figure 2 as a matrix model.

Figure 4 shows a system according to the invention in a matrix model.

FIG. 5 shows the BER performance results in the 4QAM normalization model of the amplification retransmission technique of the present invention.

6 shows the results of the 16QAM amplification retransmission scheme of the present invention in a 16QAM congruential phase.

FIG. 7 shows the gain retransmission technique of the present invention according to the MSE (Mean Squared Error).

Claims (10)

A signal amplifying retransmission method in a repeater, The repeater receiving signals from the transmitter; Estimating a channel with the transmitter using the pilot signal of the transmitter within the received signals; Removing the pilot signal within the received signals; Amplifying the signals from which the pilot signal is removed according to the estimated channel; And transmitting the pilot signal of the repeater by including the pilot signal in the amplified signals and transmitting the piled signal. The method according to claim 1, Wherein the position of the pilot signal of the transmitter is the same as the position of the pilot signal of the repeater. The method according to claim 1, Wherein a position of a pilot signal of the transmitter and a position of a pilot signal of the repeater are different from each other. 2. The method of claim 1, wherein removing the pilot signal comprises: Removing a pilot signal of the transmitter from the signals; And shifting a signal that is temporally subsequent to the pilot signal of the transmitter to a position of the pilot signal. The method according to claim 1, Wherein the transmitter is a base station and the repeater is a mobile terminal. As a repeater, A receiver for receiving signals from a transmitter; Estimating a channel with the transmitter using the pilot signal of the transmitter in the received signals, removing the pilot signal in the received signals, A processor for amplifying the pilot signal of the repeater according to a channel and for incorporating the pilot signal of the repeater into the amplified signals; And a transmitter for transmitting a signal including a pilot signal of the repeater under the control of the processor. The method according to claim 6, Wherein the position of the pilot signal of the transmitter and the position of the pilot signal of the repeater are the same. The method according to claim 6, Wherein a position of the pilot signal of the transmitter and a position of the pilot signal of the repeater are different from each other. 7. The apparatus of claim 6, wherein the processor After removing the pilot signal of the transmitter from the signals, Wherein the controller is configured to move a signal that is temporally subsequent to the pilot signal of the transmitter to a position of the pilot signal. The method according to claim 6, Wherein the transmitter is a base station and the repeater is a mobile terminal.

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