KR20120129575A - End-to-End level SVD transmission scheme in a multi-user MIMO Relay System - Google Patents

Abstract

PURPOSE: An end-to-end level singular value decomposition transmission method in an M-MIMO(Multiuser-Multiple Input Multiple Output) relay system is provided to simply relay a signal using an AF(Amplify and Forwarding) relay method. CONSTITUTION: A channel is divided into SU(Single-User)-MIMO channels using a pre-coding matrix. The channel is formed by multiplying the channel of a transmission end relay unit and the channel of a relay user in an MU-MIMO relay system. A space multiplexing signal is transmitted in the divided SU-MIMO channels using a SVD-MIMO method. The pre-coding matrix is obtained in a transmission end.

Description

End-to-End level SVD transmission scheme in a multi-user MIMO relay system

The present invention relates to an end-to-end level SVD transmission method in a multi-user multiple-input and multiple-output (MIMO) relay system. More particularly, the present invention relates to a transmitter-relay, a relay- in a multi-user MIMO relay system. A singular value decomposition of a channel multiplied by two channels of a user, and a plurality of independent single-user (MI) -MIMO relay channels using a precoding matrix based on the values. The present invention relates to a method for transmitting an interference-free spatial multiplexed signal using a single-value decomposition (SVD) -MIMO technique.

Recently, as the demand for a technology requiring high capacity data transmission increases, the conventional single input single output (SISO) communication method has adopted a single input multiple output (SIMO) communication method. Recently, multiple input multiple output (MIMO) schemes have been widely used for high capacity data transmission.

Such a MIMO system is considered to be an essential element in a fourth generation communication system requiring high frequency efficiency, by transmitting information through M antennas and receiving information through N antennas.

An example of such a conventional MIMO system is, for example, "signal transmission apparatus and method in a multiple input multiple output system" as described in Korean Patent No. 10-0459133 (registered November 19, 2004).

That is, the "signal transmission apparatus and method in a multiple input multiple output system" of the Patent No. 10-0459133 is to provide a MIMO system that takes advantage of the existing D-BLAST and complements the weak points of the V-BLAST. In other words, the present invention provides a signal transmission apparatus and method in a multi-input multi-output system that has high frequency utilization efficiency, allows each antenna array to be efficiently arranged in a limited space, and is simple to implement.

To this end, the above-mentioned Patent No. 10-0459133 is arranged at the same interval, M antennas for transmitting mutually orthogonal signals and M signal processors for encoding the input sub-data stream and encoded by each signal processor A plurality of transmission blocks including delay generation means for generating different transmission delay times in sub data streams and applying them to the respective antennas; and dividing an input data stream into the sub data streams and transmitting the plurality of transmissions for each sub data stream. In a multiple input multiple output system comprising a preprocessing encoder adding an indicator for identifying a block and demuxing means for inputting the sub data stream output from the preprocessing encoder to each signal processor of the plurality of transmission blocks. Disclosed is a signal transmission apparatus.

In addition, as another example of the prior art as described above, there is, for example, "transmitting and receiving apparatus using multiple antennas for multiple users" as disclosed in Korean Patent No. 10-0831987 (registered May 19, 2008). .

More specifically, the "transmitting and receiving apparatus using a multi-antenna for multi-user" of the Patent No. 10-0831987 described above, the conventional multi-user transmission scheme is difficult to optimize when the user receiver uses a multi-antenna In addition, in a communication system employing a frequency division scheme (FDD), since channel information must be transmitted from a receiving end to a transmitting end, in order to solve the problem of inefficient use of a channel, a high efficiency multiplex without information about a communication channel is required. It is an object of the present invention to provide a transmission and reception method using an antenna and an apparatus thereof.

To this end, the above-mentioned Patent No. 10-0831987, receives a predetermined signal and transmits it to a receiving device, and a multi-antenna unit having a plurality of antennas for receiving a signal transmitted from the receiving device, and a predetermined signal Input signal, V, which is a beamforming matrix of a predetermined communication channel, and an ESNR value, which is error information between the matrix V and the V and the V value obtained by the receiver, are input, and the input signal is based on the V and the ESNR value. A water-filling unit for water-filling and outputting the water, a V-generating unit for setting a value of V, which is a beamforming matrix for a predetermined communication channel, and providing the water-filling unit and the V-computing unit, an output signal of the water-filling unit, and A signal received from the V operation unit and the multi-antenna unit provided with the value of the matrix V set by the V generator and reflected to the output signal of the water peeling unit and provided to the multi-antenna unit. Disclosed is a transmission apparatus using multiple antennas for multiple users, comprising: an ESNR detection unit for detecting ESNR information, which is error information between the V value and the V value obtained from the reception apparatus, and providing the ESNR information to the water filling unit. .

In addition, as another example of the prior art as described above, there is a "multi-input multi-output hybrid automatic retransmission request method and apparatus using reference hopping" as disclosed in, for example, Japanese Patent Laid-Open No. 2003-134094.

That is, the above-described Japanese Patent Laid-Open Publication No. 2003-134094, "Multi-input multi-output hybrid automatic retransmission request method and apparatus using reference hopping", MIMO hybrid automatic retransmission request using basis hopping (Hybrid-ARQ In recent years, the use of multiple antennas to increase system throughput and data rates has attracted attention in communication systems such as third generation wireless systems such as the 3rd Generation Partnership Project (3GPP) and 3GPP2 standards. For such standards, different multi-antenna techniques have been proposed, such as the use of transmit diversity and multiple input multiple output (MIMO) antenna processing techniques, but provide improved data throughput and system capacity to improve the characteristics of MIMO channels. HARQ technology to fully utilize is to solve the problem that was not provided.

To this end, Japanese Patent Application Laid-Open No. 2003-134094 provides a hybrid ARQ (H-ARQ) to a transmitting apparatus having a plurality of transmitting antennas and linear transformation of the data before the data is transmitted to the receiving apparatus. (A) receiving a retransmission request (NACK) from the receiving device, (b) changing a basis used to perform a primary conversion in response to the NACK, and (c) Transmitting the pilot signal converted using the basis to the receiving apparatus through a pilot channel to enable the receiving apparatus to determine the basis after extracting the pilot signal. Doing.

However, in the conventional method as described above, in general, the communication using the MIMO technique has a high channel capacity, but when transmitting a signal to the user at the cell boundary in mobile communication, The limitation of signal reach due to constraints has not been solved.

Thus, to overcome this, for example, "On Achievable Sum Rates of A Multiuser MIMO Relay Channel", T. Tang C. B. Chae Heath, R.W. And S.C.Cho, IEEE ISIT 2006, pp. 1026-1030, July 2006 (hereinafter referred to as 'prior document 1'), the use of the relay between the transmitter and the user has attracted attention.

In addition, as another example of the prior art as described above, for example, "On the achievable throughput of a multi antenna Gaussian broadcast channel", G. Caire and S. Shamai, IEEE Trans. Inform. Theory, vol. 49, pp. 1691-706, July 2003 (hereinafter referred to as 'prior document 2').

In other words, as described in the above-mentioned prior art document, if two methods of MIMO and relay, which are being studied for high-speed communication at the same time, are used at the same time, the advantages of MIMO and relays can be used to obtain additional gains, thereby making it more efficient. Communication can be performed.

In addition, the relay transmission method using the MIMO relay increases the reach of the signal limited by the signal attenuation and improves the overall channel capacity through low cost and complexity.

However, in the case of the above-mentioned conventional document 1, there are fewer relays in the cell than the number of users, and as a result, a case in which one relay needs to support two or more users inevitably occurs.

In addition, for the above reasons, the MU (Multi-User) -MIMO relay system currently being studied has a high capacity by using the MIMO technique in the transmitter-relay channel, but the relay-multi-user channel is a broadcast channel (BC). For this reason, even in the case of the aforementioned conventional document 2, there is a problem that interference between users occurs and has a low channel capacity.

As described above, various techniques have been studied to solve the interference problem occurring in BC. However, as in the case of the prior art documents 1 and 2, most researches in the related art have a special transmission process using channel information in the relay for the interference problem. To solve it.

Therefore, in order to solve the problems of the prior art as described above, in order to solve the problem of the user-to-user interference occurring in the channel between the transmitter and the user as in the conventional methods, the transmission signal is not DPC encoded at the transmitter, thus relay-user It is desirable to provide an end-to-end level SVD transmission method in a new MU-MIMO relay system that has no transmission process to eliminate interference occurring in a channel and has a low cost and complexity. The method is not provided.

The present invention is to solve the problems of the prior art as described above, and therefore an object of the present invention, as in the conventional technique, the transmission signal at the transmitting end to solve the inter-user interference problem occurring in the transmitting end-user channel By not DPC encoding, in the relay, there is no transmission process for eliminating interference occurring in the relay-user channel, and the relay has a low cost and complexity by simply transmitting an amplify and forwarding relay relay signal. It is to provide end-to-end level SVD transmission technique in multi-user MIMO relay system in which transmitter and user become one-to-one MIMO channel and simply obtain channel capacity.

In order to achieve the above object, according to the present invention, in the end-to-end level SVD transmission method in a multi-user-multi-input and multiple-output (MIMO) relay system, the multi-user MIMO Decomposing a channel obtained by multiplying two channels of a transmitter-relay and a relay-user into a plurality of independent SU-MIMO channels using a precoding matrix, and decomposing the end-to-end SU-MIMO channel. In the present invention, there is provided an end-to-end level SVD transmission method comprising transmitting an interference-free spatial multiplexing signal using a SVD (singular value decomposition) -MIMO technique.

Here, the precoding matrix is characterized in that the precoding matrix F is obtained by using Equation 1 below when the precoding matrix is F at the transmitting end.

[Equation 1]

에서 다른 사용자의 신호 Sp(p=1,...,i-1, 1+1,...,Nu)로부터 발생하는 간섭을 제거하고,

을 다수의 독립된 SU(Single-User)-MIMO 채널로 분해하기 위한 행렬 Ti는, 이하의 [수학식 2]에 나타낸 바와 같은 조건을 만족하는 것을 특징으로 한다.
Also, in the method, when the channel between the transmitter-relay is H ₁ and the channel of the relay-i-th user is h _{i , 2,} the channel transmitted from the transmitter to the i-th user via the relay is passed through.

Removes interference from another user's signal Sp (p = 1, ..., i-1, 1 + 1, ..., Nu),

The matrix Ti for decomposing into a plurality of independent SU (Single-User) -MIMO channels is characterized by satisfying the conditions as shown in Equation 2 below.

&Quot; (2) "

의 곱을 다수의 독립된 SU-MIMO 채널로 분해하고, 그 후, 분해된 채널

에 특이값 분해(Singular Value Decomposition, SVD)를 수행하며, 이때, 상기 [수학식 1]의 상기 Vi는 상기 SVD 값의 우특이(Right singular) 행렬인 것을 특징으로 한다. In addition, the method is a channel through which the signal transmitted to the i-th user via the relay from the transmitting end via the Ti obtained from Equation (2) via

Decompose the product of into a number of independent SU-MIMO channels, and then decompose the

Singular Value Decomposition (SVD) is performed, wherein Vi in Equation 1 is a right singular matrix of SVD values.

In addition, in the above method, when the channel between the relay and the i-th user is represented by a matrix h _{i , 2} having a size of Mr × Mu, a signal transmitted from the relay is received by the i-th user via h _{i , 2} . The received signal Xi of the i-th user, which has undergone such a process, is characterized by the following [Equation 3].

&Quot; (3) "

(Where, vector n _{2 , i} is the noise of the i-th user with magnitude Mb × 1, and noise matrix n ₁ and noise n _{2 , i} are independent with mean 0 and variance σ ₁ ² , σ ₂ ² , respectively) Have the same distribution Gaussian.)

As described above, according to the present invention, the transmitter-relay channel information and the relay-user do not perform DPC encoding on the transmitter in order to solve the problem of user-to-user interference occurring in the transmitter-user channel as in the conventional method. The precoding matrix is created using the channel information, multiplied by the signal, and then transmitted, where the precoding matrix is formed as an independent end-to-end SU-MIMO channel through the channel and is made as an independent end-to-end SU-MIMO channel. By communicating the channel using the SVD transmission technique, the transmission process for eliminating interference occurring in the relay-user channel can be eliminated, and the relay is low cost since the signal is simply relayed by an amplify and forwarding relay. It has the effect of having and complexity.

In addition, according to the present invention, the transmitting end and the user become a one-to-one MIMO channel, so that the channel capacity can be simply obtained.

1 is a diagram schematically showing the configuration of a MU-MIMO relay system model for performing the end-to-end level SVD transmission technique in a multi-user MIMO relay system according to the present invention.
2 is a view showing channel capacity according to transmission power when user interference exists in the MU-MIMO relay channel according to the present invention.

Hereinafter, the details of the end-to-end level SVD transmission method in the multi-user MIMO according to the present invention as described above (sometimes referred to herein simply as 'MU-MIMO') relay system will be described.

Hereinafter, it is to be noted that the following description is only an embodiment for carrying out the present invention, and the present invention is not limited to the contents of the embodiments described below.

That is, the present invention uses the transmitter-relay channel information and the relay-user channel information without performing DPC encoding of the transmission signal at the transmitter in order to solve an inter-user interference problem occurring in the transmitter-to-user channel, as will be described later. This method differs from the conventional technique in that a precoding matrix is created, multiplied by the signal, and transmitted.

In addition, such a precoding matrix makes the transmitting end and each user an independent end-to-end SU-MIMO channel through the channel, and communicates the SU-MIMO channel thus formed using the SVD transmission technique.

Thereby, the present invention eliminates the transmission process for eliminating the interference occurring in the relay-user channel in the relay, and by simply relaying an amplify and forwarding relay relay signal to the relay, the relay provides low cost and complexity. It has its advantages.

In addition, according to the present invention, the transmitting end and the user become a one-to-one MIMO channel, so that the channel capacity can be simply obtained.

More specifically, in the multi-user MIMO relay system according to the present invention, the end-to-end level SVD transmission method uses a precoding matrix to multiply two channels of a transmitter-relay and a relay-user in a multi-user MIMO relay system. Decomposition into a plurality of independent single-user (MI) channels, and the interference-free single-to-end SU-MIMO channel obtained by decomposing the channel using a single value SVD (singular value decomposition) -MIMO technique. And transmitting the spatial multiplexing signal.

Here, the precoding matrix is defined as in Equation 1 below.

에서 다른 사용자의 신호 Sp(p=1,...,i-1, 1+1,...,Nu)로부터 발생하는 간섭을 제거하고,

을 다수의 독립된 SU(Single-User)-MIMO 채널로 분해하기 위한 행렬 Ti는, 이하의 [수학식 2]에 나타낸 바와 같은 조건을 만족하는 것을 특징으로 한다.
At this time, when the channel between the transmitter-relay is H ₁ , and the channel of the relay-i-th user is h _{i , 2,} the channel transmitted from the transmitter to the i-th user via the relay is passed through.

Removes interference from another user's signal Sp (p = 1, ..., i-1, 1 + 1, ..., Nu),

The matrix Ti for decomposing into a plurality of independent SU (Single-User) -MIMO channels is characterized by satisfying the conditions as shown in Equation 2 below.

의 곱을 다수의 독립된 SU(Single-User)-MIMO 채널로 분해하게 된다. Ti obtained from [Equation 2] is a channel through which the signal transmitted to the i-th user passes through the relay from the transmitting end.

The product of is decomposed into multiple independent SU-MIMO channels.

에 특이값 분해(Singular Value Decomposition, SVD)를 수행하고, 이때, 상기한 [수학식 1]의 Vi는 상기 SVD 값의 우특이(Right singular) 행렬이다. Then, the channel decomposed as described above

Singular Value Decomposition (SVD) is performed, wherein Vi in Equation 1 is a right singular matrix of the SVD values.

Therefore, through the above process, the transmitter and the i-th user can transmit the spatial multiplexed signal without interference using the end-to-end SVD-MIMO technique.

In other words, in the multi-user MIMO relay system according to the present invention, the first step of the end-to-end level SVD transmission method is that the received signal X _i of the i-th user is expressed by Equation 3 below.

이 되고, 상기의 채널에 [수학식 2]를 만족하는 Ti를 구하여 송신단과의 독립된 SU-MIMO 채널로 만드는 단계이다. As a result, the channel via the i-th user's signal

In this step, Ti satisfying [Equation 2] is obtained in the above channel to make a SU-MIMO channel independent of the transmitter.

와 같게 되며, 상기한 식은 단대단 독립된 SU-MIMO 채널과 같게 되고, SU-MIMO 채널은 SVD-MIMO 전송이 가능하게 된다. Going forward, the Ti obtained in the step

The above equation is equivalent to an end-to-end independent SU-MIMO channel, and the SU-MIMO channel is capable of SVD-MIMO transmission.

Vi of Equation 2 can be obtained, which corresponds to the second stage of the end-to-end level SVD transmission method in a multi-user MIMO relay system.

Therefore, based on the matrix containing Ti and Vi obtained as mentioned above, the said precoding matrix F can be calculated | required.

Subsequently, with reference to the drawings, more details of the end-to-end level SVD transmission method in the multi-user MIMO relay system according to the present invention as described above will be described.

First, with reference to Figure 1 will be described a specific embodiment of the end-to-end SVD transmission method in the MU-MIMO relay channel according to the present invention.

That is, here, as shown in Fig. 1, consider a two hop relay system for relaying signals between the transmitting end and the user.

First, it is assumed that the transmitter and the relay know the entire channel information through the CQI (Channel Quality Index).

In addition, it is assumed that a direct channel between a transmitter and a user can be ignored due to signal attenuation, and the transmitter selects a user group having the highest channel capacity by using channel information for each time slot.

It is also assumed that the transmitting end has Mb antennas, the relay has Mr antennas, and the user has Mu antennas.

In addition, it is assumed that the total number of users is Nu, and the users communicate with the transmitting end at the same time.

는 Mb×1을 가진다. Subsequently, when the signal of the i < th > user is called Nu × 1 magnitude vector Si, the transmission signal

Has Mb × 1.

This is Mb = Nu × Mu because a user having Nu antennas having the number of antennas Mb at the transmitting end has Nu names.

When the precoding matrix is F at the transmitting end and the transmission power of the transmitting end is Pt, the transmission power constraint is as shown in Equation 4 below.

Where E (?) Is average and η represents the power of each transmission antenna at the transmitting end.

At this time, the precoding F is the same as the above [Equation 1].

In Equation 1 above, the matrix Ti is the signal Sp (p = 1, ..., i-1, 1 + 1,) of another user occurring in the channel h _{i , 2} between the relay and the i th user. .., Nu) to remove the interference, and the conditions as shown in the above [Equation 2] must be satisfied.

에 잡음행렬 n1을 더한 후, 계수

의 크기로 증폭한 후 다중사용자에게 전송한다. The relay receives and transmits signals with Mr antennas, and the relay receives signals.

Add noise matrix n1 to

Amplify to size and send to multi-user.

는 이하의 [수학식 5]와 같다.
Amplification factor

Is as shown in Equation 5 below.

Where _F is Frobenius-norm.

When a channel between the relay and the i-th user is represented by a matrix h _{i , 2} having a size of Mr × Mu, a signal transmitted from the relay is received by the i-th user via h _{i , 2} .

Received signal Xi of the i-th user who has undergone the above process is as shown in Equation 3 above.

Here, the vector n _{2 , i} is the noise of the i-th user having the size Mb × 1.

In addition, the noise matrix n ₁ and noise n _{2 , i} have independent equally distributed Gaussians with mean 0 and variance σ ₁ ² , σ ₂ ² , respectively.

Therefore, through the above process, it is possible to implement the end-to-end level SVD transmission method in the multi-user MIMO relay system according to the present invention.

Next, a result of the simulation of the end-to-end level SVD transmission method in the multi-user MIMO relay system according to the present invention configured as described above will be described.

In the simulation, it is assumed that the distance between the transmitter and the user is normalized to 1 and the relay is centered.

In addition, the path loss index is 4, and the shadow has an average of 0 and a standard deviation of 8 dB.

Subsequently, referring to FIG. 2, FIG. 2 is a diagram illustrating a result of observing channel capacity according to a change in transmission power when two users and the number of antennas Mu are two.

That is, as shown in Figure 2, according to the method of the present invention as described above, has a capacity higher than the channel capacity when the user interference in the MU-MIMO relay channel.

As described above, according to the present invention, by applying precoding based on singular value decomposition, the MU-MIMO relay channel is decomposed into a plurality of independent SU-MIMO channels without interference between users, and each SU-MIMO An end-to-end level SVD transmission method is provided in a multi-user MIMO relay system, which is configured to transmit a spatial multiplexed signal using an equivalent channel formed by decomposing a channel.

Therefore, according to the present invention, since the relay does not use a special transmission process, there is an advantage that can simplify the transmission process.

Moreover, according to the above method, since the relay transmits the AF relay, there is an advantage of low cost and complexity.

As described above, the details of the end-to-end level SVD transmission technique in the multi-user MIMO relay system according to the present invention have been described through the embodiments of the present invention, but the present invention is limited only to the contents described in the above-described embodiments. Therefore, it is a matter of course that the present invention can be variously modified, changed, combined and replaced by those skilled in the art according to the design needs and various other factors. would.

Claims (5)

In the end-to-end level SVD transmission method in a multi-user-multi-input and multiple-output (MIMO) relay system,
Decomposing a channel obtained by multiplying two channels of a transmitter-relay and a relay-user into a plurality of independent SU-MIMO channels using a precoding matrix in the multi-user MIMO relay system;
And transmitting an interference-free spatial multiplexing signal to a resolved end-to-end SU-MIMO channel using a SVD (singular value decomposition) -MIMO technique. The method of claim 1,
In the precoding matrix, when the precoding matrix is F at the transmitting end, the precoding matrix F is obtained by using Equation 1 below. .

[Equation 1]

The method of claim 2,
When the channel between the transmitter-relay is H ₁ and the channel of the relay-i-th user is h _{i, 2} , the channel transmitted by the signal transmitted from the transmitter to the i-th user via the relay.

Removes interference from another user's signal Sp (p = 1, ..., i-1, 1 + 1, ..., Nu),

The matrix Ti for decomposing the signal into a plurality of independent SU (Single-User) -MIMO channels satisfies a condition as shown in Equation 2 below. Transmission method.

&Quot; (2) "

The method of claim 3,
A channel through which a signal transmitted to the i-th user passes through a relay from a transmitter by using Ti obtained from Equation 2

Decompose the product of into a number of independent SU-MIMO channels, and then decompose the

Perform Singular Value Decomposition (SVD) on,
In this case, the Vi of Equation 1 is a single-ended level SVD transmission method in a multi-user MIMO relay system, characterized in that the right singular matrix of the SVD value. The method of claim 4, wherein
When the channel between the relay and the i-th user is represented by the matrix h _{i , 2} having the size of Mr × Mu, the signal transmitted from the relay is received by the i-th user via h _{i , 2} , and i The received signal Xi of the second user is the end-to-end level SVD transmission method in the multi-user MIMO relay system, characterized by the following [Equation 3].

&Quot; (3) "

(Where, vector n _{2 , i} is the noise of the i-th user with magnitude Mb × 1, and noise matrix n ₁ and noise n _{2 , i} are independent with mean 0 and variance σ ₁ ² , σ ₂ ² , respectively) Have the same distribution Gaussian.)

Images