KR101422026B1 - A method for transmitting/receiving signal in a Multiple Input Multiple Output system - Google Patents

Abstract

This document discloses a method for transmitting and receiving signals in a MIMO system.

An example of a method for transmitting and receiving a signal in a MIMO system is to receive a signal in which a first MIMO coding and a second MIMO coding are performed from a base station in a mobile station and the first MIMO coding is performed by a plurality of base stations And the second MIMO coding is performed for at least some base stations among the plurality of base stations for each base station.

MIMO, Collaborative MIMO, STC

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for transmitting and receiving signals in a multi-

This document relates to a MIMO system, and more particularly to a method for transmitting and receiving signals in a MIMO system.

Recently, demands for wireless communication services are rapidly increasing due to the generalization of information communication services, the emergence of various multimedia services, and the emergence of high quality services. To actively cope with this, it is necessary to increase the capacity of the communication system and increase the data transmission reliability.

As a way to increase the communication capacity in a wireless communication environment, a method of newly finding an available frequency band and a method of increasing the efficiency of a given resource can be considered. In the latter method, a plurality of antennas are installed in the transceiver to obtain a diversity gain by further securing a spatial area for resource utilization, or transmission capacity is increased by transmitting data in parallel through each antenna. An MIMO (Multiple Input Multiple Output Antenna) has recently been actively developed.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for transmitting and receiving signals in a MIMO system.

A method for receiving a signal in a multiple input multiple output (MIMO) system according to an embodiment of the present invention includes receiving a signal from a base station in which a first MIMO coding and a second MIMO coding are performed, The first MIMO coding is performed by cooperative MIMO coding considering a plurality of base stations including the base station, and the second MIMO coding is performed for at least some base stations among the plurality of base stations for each base station .

The first MIMO coding may be performed in the scheduler connected to the plurality of base stations or the plurality of base stations.

The second MIMO coding may include precoding such that at least some of the plurality of base stations transmit the same signal to the terminal at a specific time.

The first MIMO coding and the second MIMO coded signal may comprise the second MIMO coded signal applying a predetermined cyclic delay to the first MIMO coded signal and the first MIMO coded signal. have.

Wherein a portion of the plurality of base stations transmits the first MIMO coded signal and the other of the plurality of base stations receives the second MIMO coded signal to which a predetermined cyclic delay is applied to the first MIMO coded signal Lt; / RTI >

The method may further include transmitting, by the terminal, feedback information based on a received signal.

The feedback information may include at least one of information related to the first MIMO coding and information related to the second MIMO coding.

The feedback information includes at least one of a Precoding Matrix Index (PMI), Channel Quality Information (CQI), Rank Indicator (RI), and Mode Indicator (MI) .

The information related to the first MIMO may be transmitted to the scheduler.

In another aspect of the present invention, in a multiple input multiple output (MIMO) system, a method of transmitting a signal includes performing a second MIMO coding on a signal on which a first MIMO coding is performed at a base station, And transmitting the coded signal to the terminal, wherein the first MIMO coding is cooperative MIMO coding considering a channel formed between a plurality of base stations including the base station and the terminal.

The first MIMO coding may be performed in the scheduler connected to the plurality of base stations or the plurality of base stations.

The first MIMO coding and the second MIMO coding may be performed using at least one of a space-time coding scheme, a space-time trellis coding scheme, a space-frequency coding scheme, a space- At least one of the techniques can be used.

In the second MIMO coding step, a precoding scheme may be applied in which the same signal is transmitted from the plurality of base stations to the mobile station at a specific time.

In the second MIMO coding step, a cyclic delay technique may be applied to at least some of the first MIMO coded signals.

The cyclic delay scheme can be applied as a cyclic delay of a certain bit in the time domain or as a product of a phase sequence in the frequency domain.

In the MIMO system disclosed in this document, it is possible to provide a more efficient signal transmission / reception method in a multi-cell environment through a method of transmitting and receiving signals.

In addition, by using cooperative MIMO coding for a plurality of base stations and MIMO coding using a plurality of transmit antennas provided in each base station, a gain due to the MIMO technique can be additionally obtained between each base station and the mobile station.

Hereinafter, preferred embodiments according to the present invention will be described in detail with reference to the accompanying drawings. The detailed description set forth below in conjunction with the appended drawings is intended to illustrate exemplary embodiments of the invention and is not intended to represent the only embodiments in which the invention may be practiced. The following detailed description includes specific details for a better understanding of the present invention. However, those skilled in the art will appreciate that the present invention may be practiced without these specific details. For example, in the following description, certain terms are mainly described, but they need not be limited to these terms, and they may have the same meaning when they are referred to as arbitrary terms.

In some instances, well-known structures and / or devices may be omitted to avoid obscuring the concepts of the present invention, and may be represented in block diagrams and / or flowchart diagrams centered on the core functions of each structure and / or device have. In the following description, the same components are denoted by the same reference numerals throughout the specification.

In this document, embodiments of the present invention have been described mainly on the data transmission / reception relationship between a base station and a mobile station. Here, the BS has a meaning as a terminal node of a network that directly communicates with the MS. The particular operation described herein as performed by the base station may be performed by an upper node of the base station, as the case may be. That is, it is apparent that various operations performed for communication with a terminal in a network composed of a plurality of network nodes including a base station can be performed by a network node other than the base station or the base station. A 'base station' may be replaced by terms such as a fixed station, a Node B, an eNode B (eNB), an access point, and the like. The term 'terminal' may be replaced with terms such as User Equipment (UE), Mobile Station (MS), and Mobile Subscriber Station (MSS).

1 is a diagram for explaining a method of performing cooperative MIMO scheme.

1, a communication system of a multi-cell environment in which a cooperative MIMO scheme can be applied includes a terminal MS 10, a serving base station BS_1 (11) for receiving uplink data transmitted from the terminal MS 10 And a neighbor base station BS_2 12 corresponding to an adjacent cell. In addition, when a plurality of base stations cooperatively perform MIMO, a scheduler 13 for scheduling transmission data to each base station may be included.

A method for diversity reception by receiving signals for the same channel from base stations located in adjacent cells in a manner similar to a method of increasing reception performance by a single user MIMO or multiple user MIMO through multiple antennas of the same cell base station, Or multi-user MIMO. In particular, a UE located at an edge of a cell, which is susceptible to interference from a neighbor cell, can reverse the situation and receive signals for the same channel from neighbor BSs to implement diversity, single user MIMO, or multiuser MIMO There will be.

The scheduler 13 applies various MIMO schemes so that the base stations located in the adjacent cells can cooperatively transmit signals to the mobile station, in particular, the mobile stations located at the edge of the cell, And transmit the data to each base station. A coding scheme that enables a plurality of base stations to transmit signals to a mobile station in a cooperative manner is referred to as cooperative MIMO coding. Various known MIMO techniques may be applied to the cooperative MIMO coding in the same or similar manner.

Meanwhile, the scheduler 13 may receive the channel information acquired through the signal received from the terminal at each base station, and configure the data to be transmitted to the corresponding terminal according to the channel condition for each base station. For example, the channel information may include channel quality information (CQI) and rank information. Then, the scheduler 13 selects the optimal coding and modulation scheme for the channel state of the corresponding terminal through the channel information, and constructs the data by applying the coding and modulation scheme.

When the cooperative MIMO scheme is applied, cooperative MIMO coding is performed according to the MIMO scheme in the scheduler 13 in order to provide a signal to the UE 10 as shown in FIG. The coded information bits are transmitted to the base stations 11 and 12 separately. Each of the base stations 11 and 12 may perform cooperative MIMO coding and then transmit the modulated signal to the UE 10 to provide cooperative MIMO.

Hereinafter, the operation of each base station will be described in more detail in applying the cooperative MIMO scheme. The cooperative MIMO scheme can be classified into an open loop scheme and a closed loop scheme depending on whether the UE provides feedback information related to cooperative MIMO coding. The following two cases should be explained in order.

FIG. 2 illustrates a cooperative MIMO scheme in an open-loop scheme according to an embodiment of the present invention. Referring to FIG.

2, a multi-cell environment communication system to which a cooperative MIMO scheme can be applied includes a MS MS 20, a serving BS BS 21 providing an uplink service to the MS MS 20, And a plurality of base stations including a neighbor base station BS_2 22 corresponding to a neighbor cell. The scheduler 23 may include a scheduler 23 for scheduling data transmitted from each base station to the mobile station when a plurality of base stations cooperatively perform MIMO.

The operation of the scheduler 23 for performing the cooperative MIMO scheme is the same as that described above with reference to FIG. According to the present embodiment shown in FIG. 2, a plurality of transmit antennas included in each of the base station BS_1 21 and the base station BS_2 22 are targeted, and each base station receives a cooperative MIMO-encoded signal In addition, separate MIMO coding can be performed.

2, in order to provide a signal to the terminal 20, the scheduler 23 performs a predetermined MIMO operation on the information bits to be transmitted to the terminal 20, Cooperative MIMO coding is performed according to the technique. The coded data can be separately transmitted to the base stations 21 and 22 according to the scheduling. Each of the base stations 21 and 22 performs MIMO coding again on the cooperative MIMO coded signal according to the present embodiment. Then, a plurality of base stations can modulate the signal subjected to the secondary MIMO coding and transmit the modulated signals to the terminal 20, thereby providing cooperative MIMO.

Meanwhile, the base station may perform spatial beamforming on a signal to be transmitted. That is, each base station can determine the channel state with the terminal and multiply it by a weight so as to form a beam that directs the terminal. At this time, spatial nulling may be performed for other users, and spatial beamforming may be applied to cooperative MIMO transmission.

In addition, when the spatial beamforming is performed using the antenna of each base station, the base station may transmit feedback information for beamforming in order to generate beamforming weights. If a beamforming scheme based on a codebook is applied, the UE can transmit a precoding matrix index (PMI) of a codebook as feedback information.

The scheduler that performs cooperative MIMO coding in FIGS. 1 and 2 may be separately provided outside the base station as shown in FIG. In this case, each base station and the scheduler can be connected through a backbone network on the communication system. Alternatively, the scheduler may be provided within each base station. In this case, the scheduler may be additionally provided for cooperative MIMO coding, or may be configured to perform cooperative MIMO coding in an existing scheduler.

In this way, cooperative MIMO coding for a plurality of base stations and MIMO coding using a plurality of transmit antennas included in each base station are used together, so that a gain due to the MIMO technique can be additionally obtained between each base station and the mobile station.

The cooperative MIMO coding described above and the MIMO coding at each base station can be performed through various techniques. For example, a block coding scheme, a spatial multiplexing scheme (SM) scheme, a cyclic delay diversity scheme (CDD) scheme, and a precoding scheme using a variety of space-time codes (STC) , Antenna Selection (AS), Antenna Hopping (AH), and Beamforming (BF) techniques. Hereinafter, the various techniques described below with respect to the main MIMO scheme among the schemes listed above will be described in more detail.

The spatial multiplexing technique can increase the data rate by dividing the input signal into several parallel signals and simultaneously transmitting them. When the sequence of the information bits corresponding to the input signal is defined as s1, s2, s3, s4, it can be expressed as shown in Table 1 below.

The coding determinant # of ANT

(One)

2 (2)

3 (3)

4

A block coding scheme using space-time codes is a technique for simultaneously obtaining diversity and coding gain by applying coding to spatial and temporal axes corresponding to antennas. When a sequence of information bits is defined as s1, s2, s3, and s4, various space-time codes can be expressed as shown in Table 2 below.

Space-time code rank # of ANT

(One)

One 2 (2)

2 2 (3)

One 4 (4)

One 4 (5)

2 4

In Table 2, a rank represents the number of transmission streams to be transmitted in one block coding and may be referred to as a spatial multiplexing rate. Also, it is shown that different space-time codes are required according to the number of antennas (# of ANT), for example, the structure of an antenna. In each determinant of Table 2, the rows represent antennas and the columns represent time slots.

Meanwhile, space-time codes of Table 2 may be extended to implement not only space-time coding but also space-frequency coding and space-time-frequency coding. For example, if extended by a space-frequency coding scheme, the columns in each matrix of Table 2 may represent subcarriers.

Space-Time Trellis Code (STTC) is a diversity and coding scheme for a multi-antenna system under a fading channel. The space-time trellis coding scheme can obtain the temporal / spatial diversity gain by transmitting the coded signal through the multiple antennas, and the coding gain can be obtained without increasing the additional bandwidth in the conventional scheme.

The STTC encoding process of the transmitting end is performed as follows. When information bits are input, symbols are allocated to each of multiple antennas according to constellation so that diversity gain and coding gain are maximized according to a given trellis, and the allocated symbols are simultaneously transmitted through the respective antennas. The symbols transmitted through the respective transmit antennas undergo independent fading, thereby achieving a diversity gain.

The Space-Frequency Trellis Code (SFTC) is a technique in which a coding process is performed in a frequency domain when a space-time trellis coding scheme is applied to an OFDM (Orthogonal Frequency Division Multiplexing) scheme And can be performed basically in the same manner as the space-time trellis coding technique described above.

In the case of OFDM signal transmission in a system having multiple transmit antennas, the cyclic delay diversity scheme is a technique in which all antennas transmit signals with different delays or different sizes to obtain a frequency diversity gain at a receiver.

According to the cyclic delay diversity scheme, OFDM symbols are separated and transmitted for each antenna through a serial-parallel converter and a multi-antenna encoder, and then a cyclic prefix (CP) for preventing interchannel interference is attached, . At this time, the data sequence transmitted to the first antenna is directly transmitted to the receiving end, but the data sequence transmitted to the next antenna is cyclically delayed by a certain bit compared to the immediately preceding antenna.

If the cyclic delay diversity scheme is implemented in the frequency domain, the cyclic delay can be expressed as a product of a phase sequence. Each data sequence in the frequency domain is multiplied by a predetermined phase sequence set differently for each antenna and then subjected to an inverse fast Fourier transform (IFFT) to be transmitted to a receiving end. This can be referred to as a phase shift diversity technique It is possible.

According to the phase shift diversity scheme, a flat fading channel can be changed to a frequency selective channel, and frequency diversity gain or frequency scheduling gain can be obtained through a channel code. In the phase shift diversity technique, when a phase sequence is generated using a large value of the cyclic delay, the frequency selectivity period is shortened, so that the frequency selectivity is increased and the channel code can obtain the frequency diversity gain. This is mainly used in open-loop systems.

In addition, since the period of frequency selectivity is long when a cyclic delay of a small value is used, a frequency scheduling gain can be obtained by allocating resources to the best channel using the closed-loop system. In the phase shift diversity scheme, when a phase sequence is generated using a small value of the cyclic delay, the channel size of a certain subcarrier region of a flat fading channel becomes larger and the channel size of another subcarrier region becomes smaller. In this case, in an OFDMA (Orthogonal Frequency Division Multiple Access) system that accommodates a large number of users, signal-to-noise ratios can be increased by transmitting a signal through a subcarrier having a larger channel size for each user.

On the other hand, the precoding scheme is a codebook based precoding scheme used in a case where feedback information is finite in a closed-loop system, and a scheme of quantizing and feedbacking channel information. In the codebook-based precoding, a signal-to-noise ratio (SNR) gain is obtained by feeding back the index of a precoding matrix already known to the transmitting and receiving end to the transmitting end.

,

과 같이 구성된 프리코딩 행렬을 특정 시간을 기준으로 교차하여 이용한다면 각 기지국에서 전송되는 신호의 안테나를 교차 이용하는 결과를 얻을 수 있다.On the other hand, for example, when two antennas are used as an intersection

,

If a precoding matrix constructed as shown in FIG. 5 is used in a crossing manner based on a specific time, a result of crossing the antennas of the signals transmitted from the respective base stations can be obtained.

Cooperative MIMO coding is performed on the information bits according to the various MIMO coding schemes described above, and the resulting streams are branched and transmitted to the corresponding base stations participating in the cooperative MIMO scheme. Then, MIMO coding of each base station is performed according to the various MIMO coding schemes described above with respect to the input stream according to this embodiment. And then OFDMA-modulated for each antenna and transmitted to the UE through each antenna.

Either of the various MIMO coding schemes described above for cooperative MIMO coding and MIMO coding of each base station may be used. It is also possible to apply various MIMO coding schemes together when possible. For example, each base station receiving the cooperative MIMO-coded signal may transmit both the precoding using an antenna as an intersection and the cyclic delay diversity to the UE. In this case, it is preferable that the MIMO scheme is selected in a direction that can obtain higher diversity effect and interference cancellation effect in performing secondary MIMO coding.

Meanwhile, when cooperative MIMO coding is performed and a cooperative MIMO coded signal is transmitted to each base station, all of the same MIMO coded signals may be transmitted to each base station. In addition, a part of the MIMO-coded signals may be transmitted to each base station or a combination of the MIMO-coded signals may be distributed and transmitted by a plurality of base stations. Hereinafter, examples of configuring a signal to be transmitted from each base station to a mobile station by a part of or a combination of MIMO coded signals will be described.

A description will be made of a case where cooperative MIMO coding is performed using a space-time block coding scheme using space-time codes of Table 1 (1), Table 2 (1), or Table 2 (2). For example, when cooperative MIMO is performed using two base stations, the data to be transmitted to each base station is represented by (1 row: 2 rows) or (1, 2 rows: 1, 2, Row).

The cooperative MIMO coding is performed using the space-time block coding technique using the space-time codes of Table 1 (3), Table 2 (3), Table 2 (4), or Table 2 (5) do. For example, in the case of cooperative MIMO using two base stations, each row may be separated and combined and transmitted to the base station in various ways. In this case, the separated criteria may be a channel state of an antenna transmitted from each base station, scheduler scheduling, and the like.

For example, when two base stations are used, (rows 1, 2, 3 and 4), (rows 2, 1, 3 and 4) : 1, 2 and 3 lines), (1 and 2 lines: 3 and 4 lines), (1 and 3 lines: 2 and 4 lines), and (1,4 lines: 2 and 3 lines). (1, 2, 3 rows, 2, 3 and 4 rows), (1, 2, 3 and 4 rows: 1, 2, 3 and 4 rows) This is possible.

The two groups of separated rows are transmitted to each base station. Each base station may apply another MIMO coding according to the present embodiment to transmit data for each of the rows. That is, in addition to the cooperative MIMO scheme, additional gains can be obtained by applying other MIMO schemes such as a cyclic delay diversity scheme or a block coding scheme such as coding of an alamuti sequence. This will apply equally or similarly to three or more base stations.

FIG. 3 illustrates a method of performing cooperative MIMO schemes in a closed-loop manner according to an embodiment of the present invention. Referring to FIG.

3, a communication system of a multi-cell environment in which a cooperative MIMO scheme can be applied includes a terminal MS 30 and a serving base station BS_1 31 (see FIG. 3) for receiving uplink data transmitted by the terminal MS 30 And a neighbor base station BS_2 32 corresponding to an adjacent cell. And a scheduler 33 for scheduling transmission data to each base station when a plurality of base stations cooperatively perform MIMO.

The operation of the scheduler 33 for performing the cooperative MIMO scheme is the same as that described above with reference to FIG. According to the embodiment shown in FIG. 3, as shown in FIG. 2, in each of the base station BS_1 31 and the base station BS_2 32, a plurality of transmission antennas included in each base station are targeted, MIMO coding is performed on the received signal, and additional MIMO coding can be additionally performed on the received signal.

In the case of FIG. 3, when the cooperative MIMO scheme is performed in a closed-loop scheme, the MS MS 30 transmits various feedback information calculated in the current channel state to the serving BS BS_1 31. At this time, the MS 30 transmits feedback information related to a plurality of neighbor BSs to the serving BS_1 31, and transmits feedback information necessary for cooperative MIMO performance to the scheduler or neighbor BS in the serving BS_1 31 And perform cooperative MIMO using this feedback information.

At this time, the feedback information may include channel quality information for a plurality of neighbor base stations including the serving base station. If the codebook-based precoding scheme is performed in the serving base station BS_1 31 and the neighbor BS_2 32 in the base station, the MS may further include a precoding matrix index (PMI) When the beamforming scheme is applied to the base station, the beamforming scheme may include beam forming information for weighting transmission power for each antenna.

Meanwhile, the terminal MS 30 can allocate predetermined uplink resources from each neighboring base station and construct feedback information for the corresponding base station to each base station and transmit the feedback information. At this time, each base station may also transmit feedback information necessary for cooperative MIMO performance among the feedback information received from the UE to the scheduler so as to more effectively perform cooperative MIMO.

The cooperative MIMO operation of the closed-loop scheme can be performed by estimating the precoding matrix that can be used in each base station and feeding back the result. The precoding matrix may be used to enable beamforming to the UE. In addition, by calculating the optimal code for the channel condition, it is possible to obtain a higher SNR at the UE and guarantee the reception performance.

FIG. 4 is a diagram for explaining an example of a method of performing cooperative MIMO scheme according to an embodiment of the present invention. Referring to FIG.

A case where the cooperative MIMO scheme is applied through two base stations, i.e., the base station BS_1 41 and the base station BS_2 42 will be described. The input signals of base station BS_1 41 and base station BS_2 42 represent data determined by the cooperative MIMO coding scheme in scheduler 43 and may be grouped in cooperative MIMO coding and transmitted to the base station.

~

의 소정의 지연 값(45)이 적용된 신호도 함께 전송으로써 순환 지연 다이버시티(CDD) 기법을 적용한다.In the case of Figure 4, the cooperative MIMO coded by the space-time code (1) in Table 1 in the scheduler 43, and: is a branch with a (1 row 2 lines) as s ₁ is the base station BS_1 (41), respectively, s ₂ Is transmitted to the base station BS_2 (42). This signal is weighted by the precoding matrix 44 with secondary MIMO coding at each base station

~

(CDD) technique by transmitting a signal to which a predetermined delay value 45 of the delayed value 45 is applied.

의 지연만 고려한다면, 단말에서 수신되는 신호는 수학식 1과 같이 나타낼 수 있다.At this time,

The signal received at the terminal can be expressed by Equation (1). &Quot; (1) "

는 도 4에 나타난 바와 같이 순환 지연 다이버시티 기법을 적용하기 위해 적용되는 소정의 지연 값을 나타낸다.In Equation 1 h _{BSk _ rt} refers to a channel formed between the r-th antenna of a terminal in a cooperative base station and performing the MIMO BS_k in the t-th transmit antenna. And, h in equation 1 _{BSk _ rt} refers to a channel formed between the r-th antenna of a terminal in a cooperative base station and performing the MIMO BS_k in the t-th transmit antenna. And,

Represents a predetermined delay value applied to apply the cyclic delay diversity scheme as shown in FIG.

(1, 0) and (0, 1) for the channel estimation are arranged in (s ₁ , s ₂ ) as can be seen by checking the reception signal of Equation (1) The equivalent channel generated when transmitting s ₁ and s ₂ can be easily obtained, so that the terminal can more easily perform signal restoration. In addition, since the reference signal structure used in the case of applying the existing MIMO scheme, that is, when the MIMO scheme is applied to one base station, can be applied as it is, cooperative MIMO can be easily implemented.

In addition to the cooperative MIMO coding gain applied in the scheduler, if the cyclic delay diversity (CDD) scheme is applied to the secondary MIMO in each base station, the scheduling gain if the delay value is set to be small, the diversity gain . In addition, there is an advantage that the channel estimation between each terminal and each base station is facilitated.

5 is a view for explaining another example of a method for performing cooperative MIMO scheme according to an embodiment of the present invention.

In another method, when each base station transmits a signal in which cooperative MIMO coding is performed, the role of each base station may be separated as shown in FIG. For example, FIG. 5 shows a structure in which a circulating delay diversity scheme is applied to each base station, and each base station cooperates with each other in transmitting a symbol with a cyclic delay diversity scheme.

For example, the scheduler 53 performs cooperative MIMO coding based on the space-time code of Table 1 (1), and these data are transmitted to each base station. At this time, assuming that the signals are transmitted in the branching method of (1, 2 rows: 1 and 2 rows), the input signals of all base stations are the same and the precoding matrix used in each base station is the same.

That is, the base station BS_1 transmitted to the 51 to base station BS_n (52) x _{BS1_0} (i) to x _{BSn _0} (i) are identically configured, the base station BS_1 51 to base station BS_n (52) each representing a respective input signal do. Then, the weights are determined by the precoding matrices 54 and 55 in the secondary MIMO coding in each base station, and the cyclic delay diversity scheme is extended and applied to each base station as described above.

의 소정의 지연 값(56)을 적용하여 단말로 전송한다. 따라서 단말 측에서 협력적 MIMO 기법으로 수신하는 신호는 협력적 MIMO 코딩에 의한 알라뮤티 코드에 대하여 각 신호가 순환 지연이 적용된 상태로 수신할 수 있게 된다.In order to extend and apply the cyclic delay diversity scheme to each base station, the base station BS_1 transmits to the mobile station without applying the delay value, and the base station BS_n (52)

And transmits the delay value 56 to the terminal. Therefore, the signal received by the cooperative MIMO scheme on the UE side can receive the allmuti code by the cooperative MIMO coding with each signal applied with the cyclic delay.

In each base station, not only the cyclic delay diversity scheme but also various MIMO schemes can be applied. At this time, the symbols are rearranged so that the symbols transmitted through the antenna of each base station are the same at any moment through a predetermined coding scheme or a precoding matrix can do.

Thereby, the terminal not only obtains the path diversity gain but also obtains an advantageous effect for channel estimation. As shown in FIG. 5, each base station applies a closed-loop MIMO scheme using a cyclic delay diversity (CDD) and a precoding matrix with secondary MIMO coding, and a precoding matrix The feedback overhead can be reduced when the feedback information is transmitted as compared with the case of independently transmitting the precoding matrix index (PMI) to be used for each base station.

와 같이 하고 두 번째 기지국의 코딩 결과도

와 같이 서로 동일하게 생성 시키도록 한다. For example, the first base station performs space-time code coding for s ₁ and -s ₂ ^* , and the second base station performs space-time code coding for s ₂ and s ₁ ^* . At this time, the coding result of the first base station

And the coding result of the second base station is also

As shown in FIG.

In this way, even if the scheduler 53 does not transmit the same data to each base station, it can be reconstructed in the same form through precoding at each base station, and the cyclic delay diversity gain between the base stations may be obtained. Each base station may determine the weight and order of the actually transmitted antennas using the precoding matrix and apply coding according to the channel condition of each base station.

It is clear that the claims that are not expressly cited in the claims may be combined to form an embodiment or be included in a new claim by an amendment after the application.

Embodiments in accordance with the present invention may be implemented by various means, for example, hardware, firmware, software, or a combination thereof. In the case of a hardware implementation, in a MIMO system according to an embodiment of the present invention, a method of receiving a signal may include one or more application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices, programmable logic devices (PLDs), field programmable gate arrays (FPGAs), processors, controllers, microcontrollers, microprocessors, and the like.

In the case of a firmware or software implementation, in a MIMO system according to an embodiment of the present invention, a method for receiving a signal may be implemented in the form of a module, a procedure, a function, have. The software code can be stored in a memory unit and driven by the processor. The memory unit may be located inside or outside the processor, and may exchange data with the processor by various well-known means.

It will be apparent to those skilled in the art that the present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. Accordingly, the above detailed description is to be considered in all respects as illustrative and not restrictive. The scope of the present invention should be determined by rational interpretation of the appended claims, and all changes within the scope of equivalents of the present invention are included in the scope of the present invention.

1 is a diagram for explaining a method for performing cooperative MIMO scheme;

FIG. 2 illustrates a cooperative MIMO scheme in an open-loop scheme according to an embodiment of the present invention; FIG.

3 is a diagram illustrating a method of performing cooperative MIMO schemes in a closed-loop manner according to an embodiment of the present invention.

4 is a diagram for explaining an example of a method of performing cooperative MIMO scheme according to an embodiment of the present invention;

5 is a diagram for explaining another example of a method for performing cooperative MIMO scheme according to an embodiment of the present invention;

Claims (16)

In a multiple input multiple output (MIMO) system, in a method for a terminal to receive a signal, Receiving a second MIMO coded first signal for a first MIMO coded signal from a first base station; And Receiving a second MIMO coded second signal from the second base station for the first MIMO coded signal, Wherein the first MIMO coding is cooperative MIMO coding considering the first base station and the second base station and is performed in a scheduler connected to the first base station and the second base station, Wherein the second MIMO coding is performed for each base station in the first base station and the second base station, The signal subjected to the first MIMO coding is a matrix of N rows, Wherein the first signal comprises the second MIMO coded signal for N-M (where 0 <M <N-1) rows selected in the matrix, Wherein the second signal comprises the second MIMO coded signal for N-L (where 0 < L < N-1) rows selected in the matrix. delete The method according to claim 1, Wherein the second MIMO coding comprises precoding to cause the first base station and the second base station to transmit the same signal to the terminal at a particular time. The method according to claim 1, Receiving the first MIMO coded signal from one of the first base station and the second base station and receiving the second MIMO coded signal to which a predetermined cyclic delay is applied to the first MIMO coded signal from the other And the signal is received. The method according to claim 1, Wherein the first MIMO coding and the second MIMO coded signal comprise the second MIMO coded signal and applying a predetermined cyclic delay to the first MIMO coded signal and the first MIMO coded signal, &Lt; / RTI &gt; The method according to claim 1, And transmitting feedback information based on the first signal and the second signal. The method according to claim 6, Wherein the feedback information comprises at least one of information related to the first MIMO coding and information related to the second MIMO coding. 8. The method of claim 7, Wherein the information associated with the first MIMO is communicated to the scheduler. The method according to claim 6, The feedback information includes at least one of a Precoding Matrix Index (PMI), Channel Quality Information (CQI), Rank Indicator (RI), and Mode Indicator (MI) And the signal is received. In a multiple input multiple output (MIMO) system, in a method for a base station to transmit a signal, Generating a second signal by second MIMO coding the first MIMO coded first signal; And And transmitting the second signal to the terminal, Wherein the first MIMO coding is cooperative MIMO coding considering a channel formed between a plurality of base stations including the base station and the mobile station and is performed in a scheduler connected to the plurality of base stations, The first signal is a matrix of N rows, Wherein the second MIMIO coding is performed on N-M (where 0 < M < N-1) rows selected in the matrix. delete 11. The method of claim 10, The first MIMO coding and the second MIMO coding may be performed using at least one of a space-time coding scheme, a space-time trellis coding scheme, a space-frequency coding scheme, a space- Wherein at least one of the techniques is used. 11. The method of claim 10, And a precoding scheme is applied to transmit the same signal to the mobile station at a specific time from each of the plurality of base stations in the second MIMO coding step. 11. The method of claim 10, Wherein in the second MIMO coding step a cyclic delay technique is applied to at least a portion of the first MIMO coded signal. 15. The method of claim 14, Wherein the cyclic delay technique is applied as a cyclic delay of a predetermined number of bits in a time domain or as a product of a phase sequence in a frequency domain. The method according to claim 1, At least one of the N-M rows and the N-L rows, The channel state of at least one of the first base station and the second base station, and scheduling of the scheduler.

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