WO2012091342A2 - Communication method for a base station in a cooperative multi-cell communication system, base station therefor, communication method for a terminal, and terminal therefor - Google Patents

Abstract

The present invention relates to a cooperative multi-cell communication system, to a communication method therefor, and to a device therefor.

Description

A communication method of a base station, a communication method of the base station, a terminal, and the terminal in a cooperative multi-cell communication system

The present invention relates to a cooperative multi-cell communication system in which two or more base stations cooperate to transmit a signal.

As communication systems have evolved, consumers, such as businesses and individuals, have used a wide variety of wireless terminals.

Accordingly, communication service providers are continuously attempting to expand the existing communication service market by creating a new communication service market for wireless terminals and providing reliable and inexpensive services.

The present invention provides a method and apparatus for transmitting information through cooperative communication between two or more base stations including two or more transmission antennas and receiving the channel information directly or indirectly from the terminal, a method for the terminal to report channel information to the base station, and the same. Provide the device.

In an embodiment, in a cooperative multi-cell communication system, at least one base station of at least two or more base stations transmits a signal to a terminal through at least one antenna group of two or more antenna groups of different polarizations; And another base station except the at least one base station among the base stations transmits a signal to the terminal through a polarization antenna group having a polarity different from the at least one antenna group among two or more antenna groups of different polarizations. It provides a cooperative communication method of a cooperative multi-cell communication system comprising a transmission step.

According to another embodiment of the present invention, in a cooperative multi-cell communication system, a first base station precodes a data symbol using only components of a precoding matrix corresponding to at least one antenna group of two or more antenna groups of different polarizations, and transmits the data symbols to the terminal. Transmitting a signal; And a second base station precodes a data symbol using only components of a precoding matrix corresponding to the at least one antenna group of two or more antenna groups of different polarizations and the antenna group of a polarization having a different polarity, thereby signaling the terminal. It provides a cooperative communication method of a cooperative multi-cell communication system comprising transmitting a.

In another embodiment, in a cooperative multi-cell communication system, one base station of at least two or more base stations may transmit its own channel state information from a terminal and channel state information of another base station except the one of the base stations. A receiving step of receiving channel information including; By using the channel information, at least one of two or more antenna groups of different polarizations corresponding to some of the components of the precoding matrix used by the other base station to precode the data symbol, the polarity is different Provided is a communication method of a base station comprising a transmission step of transmitting a signal to the terminal by precoding a data symbol using only components of a precoding matrix corresponding to a polarization antenna group.

Still another embodiment provides a method of receiving a signal transmitted through at least one antenna group of two or more antenna groups of different polarizations in at least one of at least two base stations in a cooperative multi-cell communication system; And a signal transmitted through an antenna group of a polarization having a polarity different from that of the antenna group in the at least one base station among two or more antenna groups of different polarizations of another base station except the at least one base station among the base stations. It provides a cooperative communication method of the terminal comprising the step of receiving.

In another embodiment, in a cooperative multi-cell communication system, data symbols are precoded and transmitted using only components of a precoding matrix corresponding to at least one antenna group of two or more antenna groups of different polarizations of a first base station. Receiving the received signal; And a data symbol precoded using only components of a precoding matrix corresponding to the at least one antenna group of the at least one antenna group of the different polarizations of the second base station and the antenna group of the polarization having a different polarity. It provides a cooperative communication method of the terminal comprising the step of receiving.

Yet another embodiment provides a method of receiving a reference signal of a first base station in a cooperative multi-cell communication system; A first base station channel state information estimating step of estimating channel state information only for n antenna pairs of the first base station reference signal when there are 2n antenna pairs of different polarized antennas in the first base station; Receiving a reference signal of a second base station; When there are 2m antenna pairs of different polarized antennas in the second base station, channel state information is applied only to m antenna pairs (m is a natural number greater than or equal to 1 or greater than 1) of the second base station reference signals. Estimating a second base station channel state information; And channel information transmitting the channel information including the first base station channel state information and the second base station channel state information to the first base station.

1 is a block diagram illustrating a cooperative multi-cell communication system to which embodiments are applied.

2 is a block diagram illustrating a cooperative multi-cell communication system to which embodiments are applied.

FIG. 3 illustrates an antenna array structure of a base station and a terminal and a propagation channel according to the cooperative multi-cell communication system of FIG. 1 or 2.

4 is a conceptual diagram of rank 1 cooperative communication of each base station in a cooperative multi-cell communication system according to an embodiment.

5 is a flowchart illustrating a cooperative communication method between terminals and base stations of a cooperative multi-cell communication system according to another embodiment.

6 is a conceptual diagram of a cooperative multi-cell communication system according to another embodiment.

7 is a conceptual diagram of a cooperative multi-cell communication system according to another embodiment.

8 is a flowchart illustrating a cooperative communication method between terminals and base stations of a cooperative multi-cell communication system according to another embodiment.

9 is a configuration diagram of each of the base stations and the terminal in the cooperative multi-cell communication system according to another embodiment.

10 is a flowchart illustrating a communication method of a transmitting apparatus according to another embodiment.

11 is a flowchart of a communication method of a receiving apparatus according to another embodiment.

12 and 13 are block diagrams illustrating a cooperative multi-cell communication system according to another embodiment.

Hereinafter, some embodiments of the present invention will be described in detail through exemplary drawings. In adding reference numerals to the components of each drawing, it should be noted that the same reference numerals are assigned to the same components as much as possible even though they are shown in different drawings. In addition, in describing the present invention, when it is determined that the detailed description of the related well-known configuration or function may obscure the gist of the present invention, the detailed description thereof will be omitted.

1 is a block diagram illustrating a cooperative multi-cell communication system to which embodiments are applied.

In the cooperative multi-cell communication system 100 to which the embodiments are applied, a coordinated multi-point transmission / reception system (CoMP) or cooperative multi-antenna transmission in which two or more transmitters cooperate to transmit a signal There is a coordinated multi-antenna transmission system, a cooperative multi-cell communication system (hereinafter referred to as a "cooperative multi-cell communication system").

The cooperative multi-cell communication system 100 to which the embodiments are applied is a cooperative multi-cell communication system in which two or more transmission terminals cooperate to transmit a signal. Each transmission terminal includes two or more transmission antennas and one or more transmission terminals are provided. Multi-antenna transmission may be performed by receiving channel information from a receiver.

In this cooperative multi-cell communication system 100, two or more, for example, three base stations (110, 112, 114) to the same frequency resource at the same time when attempting cooperative transmission and reception to one user terminal 120 Allocate it to service. That is, three base stations 110, 112, and 114 selected as cooperative base stations at the same time may transmit and receive data with one user terminal 120 using the same frequency resource.

Terminals using such a communication method may be terminals having weaker signal strength than cells in the center region of a cell mainly in an intercell boundary region, and are relatively close to other base stations, and thus may receive signals from two or more base stations. It may be terminals. Since two or more base stations transmit signals in a cooperative manner to these terminals, the terminal may obtain better performance than receiving signals from one base station. At this time, two base stations may cooperate or three or more base stations may cooperate. In addition, the present invention can be applied not only to a single user multiple antenna (SU-MIMO) scheme but also to a multi user multiple antenna (MU-MIMO) scheme.

The cooperative multi-cell communication system 100 may be widely deployed to provide various communication services such as voice and packet data.

Terminal 120 (User Equipment, UE) in the present specification is a generic concept that means a user terminal in wireless communication, WCDMA, UE (User Equipment) in LTE, HSPA, etc., as well as MS (Mobile Station) in GSM It should be interpreted as a concept that includes a user terminal (UT), a subscriber station (SS), and a wireless device.

One terminal 120 may be connected to two or more base stations (110, 112, 114) at the same time to receive the service, and the plurality of base stations (110, 112, 114) with a plurality of base stations at regular intervals according to the channel situation It may be connected to a base station having a good channel to receive service. Therefore, the base station selected as the cooperative base station should be a base station having a good channel performance for any frequency band for one terminal.

Base stations (110, 112, 114: base station, BS) or cell (cell) generally refers to a fixed station (fixed station) to communicate with the terminal 120, Node-B (Node-B), evolved (eNB) Node-B), BTS (Base Transceiver System), access point (Access Point) may be called other terms.

That is, in the present specification, the base station 110, 112, 114, or cell should be interpreted in a comprehensive sense to indicate some areas covered by a base station controller (BSC) in CDMA, a NodeB in WCDMA, and the like. It is meant to cover all of the various coverage areas, such as macrocell, microcell, picocell, femtocell, etc.

In the present specification, the base stations 110, 113, 114, and the terminal 120 are two transmission / reception entities used to implement the technology or the technical idea described in this specification, and are used in a generic sense and specifically referred to in a term or word. It is not limited by.

There is no limitation on the multiple access scheme applied to the wireless communication system. Various multiple access techniques such as Code Division Multiple Access (CDMA), Time Division Multiple Access (TDMA), Frequency Division Multiple Access (FDMA), Orthogonal Frequency Division Multiple Access (OFDMA), OFDM-FDMA, OFDM-TDMA, OFDM-CDMA Can be used.

The uplink transmission and the downlink transmission may use a time division duplex (TDD) scheme that is transmitted using different times, or may use a frequency division duplex (FDD) scheme that is transmitted using different frequencies.

One embodiment of the present invention provides asynchronous wireless communication that evolves into Long Term Evolution (LTE) and LTE-advanced through GSM, WCDMA, HSPA, and synchronous wireless communication that evolves into CDMA, CDMA-2000 and UMB). Applicable to resource allocation. The present invention should not be construed as being limited or limited to a specific wireless communication field, but should be construed as including all technical fields to which the spirit of the present invention can be applied.

Meanwhile, in the present specification, when a cooperative multi-cell communication system (CoMP) is implemented by another transmission terminal of the same base station that is in charge of another cell, this is referred to as an intra-eNB coMP and is responsible for another cell. When a cooperative multi-cell communication system (CoMP) is implemented by another base station, this is called an inter-cooperative multi-cell communication system (inter-eNB CoMP).

In particular, to provide a higher reception sensitivity to a terminal located in a cell or sector boundary area where the reception strength of the radio wave region or the radio wave is relatively weak, and to reduce the interference between cells or to use the radio resources more effectively or to cooperate with one or more transmitters. Signal can be transmitted. The transmitter may be a transmitter that belongs to another base station or a transmitter that is responsible for another cell belonging to the same base station.

The terminal 120 receives data from the base stations 110, 112, and 114, respectively, but since the frequency bands for receiving the federated data are the same, the terminal 120 may be regarded as receiving data from one transmission point. That is, the terminal 120 may regard the set of three base stations 110, 112, and 114 as one transmission point.

2 is a block diagram illustrating another cooperative multi-cell communication system to which embodiments are applied.

2, in another cooperative multi-cell communication system 100 to which embodiments are applied, a base station performing cooperative communication with a terminal 120 may be the macro base stations 110, 112, and 114 shown in FIG. 1. Can be located within the cell radius of one macro base station (110, 112, 114), femto cell (115), pico cell (Pico cell, 116), relay (Relay, 117), hot spot (118) Various types of micro or local base stations, such as

If each transmitting end is provided with two or more transmitting antennas and MIMO transmission is possible, the cooperative multi-cell communication system 100 may not only perform cooperative communication between macro base stations 110, 112, and 114 but also micro base stations or pico. Even among the base stations having different driving characteristics such as the base stations 115, 116, and 117, superior system performance can be obtained through cooperative communication.

Alternatively, if beamforming or precoding values are set in consideration of only channel conditions with existing base stations during beamforming or precoding, in a cooperative multi-cell communication system, a base station estimates or interferes with channel conditions with neighboring base stations. It is possible to set the beamforming or precoding value by estimating.

1 and 2, the terminal 120 analyzes reference signals transmitted from each of the base stations 110 through 117 to determine a channel state of each antenna of each base station 110 through 117. After identifying each channel condition, the information is fed back to each base station 120 directly or indirectly. Base stations 110 to 117 or higher layers fed back with this information select base stations that exhibit good channel performance to form a cooperative base station set or a CoMP set, and the base stations included in the cooperative base station set or CoMP set are cooperatively transmit and receive. Will be started.

3 illustrates an antenna array structure of a base station and a terminal and a propagation channel according to the cooperative multi-cell communication system of FIG. 1 or 2.

Referring to FIG. 3, each of the base stations illustrated in FIGS. 1 and 2, for example, the base station 110 may include an antenna array 310 including two or more antennas. Although the base station 110 is exemplarily described, other macro or micro base stations described with reference to FIGS. 1 and 2 may be the same. Similarly, the terminal 120 illustrated in FIGS. 1 and 2 may also include an antenna array 320 including two or more antennas.

In this case, the antenna arrays 310 may use a dual polarized antenna array in which two antennas having different polarizations are alternately installed to arrange more antennas in a limited space in a communication system. Antennas equally polarized in one polarity (direction) of the antennas included in the antenna arrays 310 are referred to as the first domain or the first antenna group 310a of the base station (hereinafter referred to as 'first antenna group of base station'). Antennas equally polarized in the other polarity (direction) may be referred to as the second domain or the second antenna group 310b of the base station (hereinafter referred to as 'the second antenna group of the base station'). It is not limited to. In this case, the first antenna group 310a of the base station and the second antenna group 310b of the base station may be orthogonal, but are not limited thereto.

Similarly, the antenna arrays 320 included in the terminal 120 are dual polarized antenna arrays in which two antennas having different polarizations are alternately installed in order to arrange more antennas in a limited space in a communication system. ) Can be used. Antennas equally polarized in one direction among the antennas included in the antenna array 320 may be called a first domain or a first antenna group 320a (hereinafter, referred to as a 'first antenna group of a terminal') of a terminal. And the same polarized antennas in the other direction may be referred to as a second domain or a second antenna group 320b of the terminal (hereinafter, referred to as a “second antenna group of a terminal”), but is not limited thereto. In this case, the first antenna group 320a of the terminal and the second antenna group 320b of the terminal may be orthogonal, but are not limited thereto.

In the above embodiment, a dual polarization antenna array has been described as an example, but the present invention is not limited thereto. For example, it may be a multi-polarized antenna array such as a triple polarized wave or a quadrupole polarized antenna array. In addition, the base station and the terminal are not limited to including a multi-polarized antenna array such as a single polarized antenna, and may include two or more multi-polarized antenna arrays and a single array antenna. At this time, the base station and the terminal may use all of two or more multiple polarization antenna arrays or some of them selectively.

Meanwhile, the base station 110 may perform dual structure precoding as described later in downlink transmission. In this structure, W ₁ and W ₂ constituting the precoding matrix may be transferred from the terminal 120 to the base station 110 through PMI1 or PMI2, which are different precoding matrix indicators, respectively. have.

W ₁ may be a precoder matrix selected for the entire system bandwidth. On the other hand, W ₂ is selected as one precoding matrix for the entire system bandwidth or one precoding matrix for each subband, which is a subset of the system band. ) May be selected.

In other words, the terminal 120 may report one W ₁ and a plurality of W ₂ generally within a reporting period, and one digital factor indicating W ₁ for all bands to which the terminal 120 intends to receive a signal. The value PMI1 is reported to the base station 110, and the digital factor values PMI2 are determined to be suitable for use as W ₂ in each subband after the full band is divided into several subbands. You can report it. The reason for using this method is to perform precoding using a different precoder matrix for each subband. In order to use a different precoder matrix for each subband, W ₁ and W ₂ may have a structure as follows.

[Equation 1]

W = W ₁ W ₂

In Equation 1, W ₁ is [X _n 0; 0 x _n ] block diagonal matrix. W ₂ is a matrix that performs beam selection and performs co-phasing to correct for phase mismatch between antenna groups.

For example, when performing rank 1 and 2 transmissions, the precoding matrix W ₁ indicated by the digital index n may be as follows.

[Equation 2]

In this case, W ₁ ^(K) is a block diagonal matrix as follows.

[Equation 3]

At this time

Where X ^(K) is

to be.

Therefore, the precoding matrix W ₁ indicated by the digital index n may be as follows.

[Equation 4]

In this case, b _n is beam forming vectors that perform beam forming, and may perform beam forming according to a signal transmission and reception direction.

Is a column vector of zero and the same size as b _n .

In particular, adjacent overlapping beams at b _n of W ₁ , for example four adjacent beams, can be used to reduce the edge effect in frequency selective procoding. For convenience, in the present specification, a case _where the size of b _n is 4 will be described as an example. The size of b _n is not limited to four.

That is, in the case of rank 1 and rank 2, the codebook is an index for selecting four adjacent beam forming vectors, and the codebook is expressed as an index of the beamforming vector selected according to PMI1 of the codebook.

. Thus, 16 W ₁ matrices for each rank, [0,1,2,3], [2,3,4,5], [4,5,6,7] ,. ..., [28,29,30,31], [30,31,0,1]. In this case, although the beams are described as being adjacent, the present invention is not limited thereto, and the W ₁ matrix may be formed of non-adjacent beams.

Meanwhile, in the W ₁ matrices, two beamforming vectors may overlap each other. For example, [2,3] overlaps with [0,1,2,3] and [2,3,4,5].

In this case, W ₁ may coincide with the spatial covariance of the dual polarized antenna array polarized at a constant distance.

In this case, b _n are beam forming vectors that perform beam forming, and may be expressed as in the following equation.

[Equation 5]

the magnitude of b _n as a simple example of less than 4, in the form of W ₁ according to the PMI1 = n = 2 to refer to the precoder matrix W ₁ may be set as follows.

[Equation 6]

That is, each element of the codebook for reporting W ₁ may be composed of a combination of a plurality of beam forming vectors.

In the case of a transmission stage including 8 antennas, when 32 beamforming vectors are represented by beam indices n of 0 to 31, b ₀ ³² = (1,1,1,1) and b ₁ ³² = ( 1, e ^{j (π / 16)} , e ^{j (2 π / 16)} , e ^{j (3 π / 16)} }, b ₂ ³² = (1, e ^{j (2π / 16)} , e ^{j (4π / 16 )} , e ^{j (6π / 16)} ), ..., b ₃₁ ³² (1, e ^{j (31π / 16)} , e ^{j (62π / 16)} , e ^{j (93π / 16)} ).

W ₂ simultaneously performs a process of selecting r of a plurality of beam forming vectors included in W ₁ ^(K) and a co-phasing operation. In other words, the codebook of W ₂ (in the case of rank 1 transmission), one of the vectors of four beamforming selection by W ₁ or 2 for repeated selection (in the case of Rank 2 transmission) performs the task of, and at the same time each Determines the co-phase element applied to the beamforming vectors to be used for the transmit antenna group (or domain).

When performing rank 1 transmission, W ₂ may be defined as in the following equation.

[Equation 7]

In this case, Y is a beam selection vector for performing beam selection.

Is a co-phase element that performs a phase matching operation, and may be, for example, 1 or -1, j, -j.

That is, when performing rank 1 transmission, W ₂ is

For example, 1 or -1, j, -j can be defined as the following equation.

[Equation 8]

At this time

Is a 4 × 1 selection vector with a value of 1 for the nth component and a value of 1 for the remaining components.

Therefore, Y can be defined as follows.

[Equation 9]

In case of performing rank 2 transmission, W ₂ may be defined as follows.

[Equation 10]

That is, when performing rank 2 transmission, W ₂ is

For example, 1 or -1, j, -j can be defined as the following equation.

[Equation 11]

In this case, Y ₁ and Y ₂ are beam selection vectors for performing beam selection.

Is a phase matching element value for performing the phase matching operation, and may be, for example, 1 or -1, j, -j.

In this case, Y ₁ selects a beamforming vector to be used for the first layer transmission when the value of PMI2 indicating W ₂ is a from 4 beamforming vectors selected by W ₁ , and Y ₂ When the value of PMI2 indicating W ₂ is a, a beamforming vector to be used for the second layer transmission is selected from four beamforming vectors selected by W ₁ .

Y ₁ and Y ₂ may be defined as follows.

[Equation 12]

That is, Y ₁ , Y ₂ are column vectors of length 4 with one value equal to 1 and the other equal to zero.

In other words, for rank 2

When the beamforming vector selected through W ₁ and Y ₁ is applied to the transmitting antenna group (domain), the phase matching element value and the beam forming vector determined by W ₁ and Y ₂ are transmitted antenna group Z _1. And a phase match element value to be used when applied to Z ₂ , for example, from (1, j).

[Equation 13]

Therefore, when performing rank 1 transmission, W may have the following structure.

[Equation 14]

In the following equations, the relationship between the terminal and the n-th base station is represented by a superscript n. For example, the relationship between the terminal and the first base station is represented by superscript 1, and the relationship between the terminal and the second base station is represented by superscript 2.

In case of performing rank 2 transmission, W may have a structure as follows.

[Equation 15]

Meanwhile, the channel matrix or the propagation channel between the base station 110 and the terminal 120

Let's do it. Where the precoding matrix is rank1

When the signal is transmitted to the terminal 120 by precoding using the signal received from the terminal 120

Becomes On the other hand, the precoding matrix with rank 2 or higher, for example rank 2

When the signal is transmitted to the terminal 120 by precoding the signal, the signal received by the terminal may be as follows.

[Equation 16]

In this case, R _b means a signal received by the first antenna group 320a of the terminal, and R _r means a signal received by the second antenna group 320b of the terminal.

4 is a conceptual diagram of rank 1 cooperative communication of each base station in a cooperative multi-cell communication system according to an embodiment.

Referring to FIG. 4, in the cooperative multi-cell communication system 400 according to an embodiment, base stations and a terminal may perform cooperative communication as illustrated in FIGS. 1 and 2. In this case, only the two base stations, namely, the first base station 410 and the second base station 420 are described as base stations participating in the cooperative communication, but as described above, more than two base stations cooperate with the terminal. You can also join

Each of the first base station 410 and the second base station 412 may include antenna arrays 410a and 410b, 412a and 412b including antennas polarized into two antenna groups as described with reference to FIG. Can be. Similarly, the terminal 420 may also include an antenna array (not shown in FIG. 4) including antennas polarized into two antenna groups as described with reference to FIG. 3.

At this time, the channel matrix and the precoding matrix of the base stations 410 and 412 and the terminal 420 are the same as described with reference to FIG. 3, but the first base station 410 is one of the base stations to distinguish between the base stations and the terminal. The elements of the channel matrix and the precoding matrix related to are denoted by superscript 1, respectively, and the elements of the channel matrix and the precoding matrix associated with the second base station 412, respectively, are denoted by superscript 2.

For example, the first base station 410 uses its precoding matrix to precode the data symbols and 2n the precoded data symbols (n is a natural number greater than 1 or 1), for example, 8 polarized antennas. It may propagate to the air through the antenna array 410a including them.

Meanwhile, the first base station 410 and the second base station 412 may use a dual structure precoding (precoder) matrix represented by W = W ₁ W ₂ , respectively. As described above, the first base station 410 uses the precoding matrix used for transmitting the terminal 420.

And the propagation channel between the first base station 410 and the terminal 420

Can be displayed as Also, the precoding matrix used by the second base station 412 to transmit the terminal 420 is used.

(Superscript 2 means the relationship between the terminal and the second base station, which is the same below) and indicates a propagation channel between the first base station 410 and the terminal 420.

Can be displayed as

First base station 410 loses the channel

Precoding matrix with rank 1 MIMO transmission via

The second base station 420

Precoding matrix with rank 1 MIMO transmission via

(Superscript 1 means the relationship between the terminal and the first base station, the same below) The signal received by the terminal 420 when the first base station 410 and the second base station 412 transmits the same information is as follows. May be the same.

[Equation 17]

Meanwhile, when the first base station 410 and the second base station 412 transmit different information, the signal received by the terminal 420 may be as follows.

Equation 18

Xp means information transmitted by the transmitter p, X _M means information transmitted by the transmitter M. As described above, R _b means a signal received by the first antenna group of the terminal and R _r means a signal received by the second antenna group of the terminal.

In the cooperative multi-cell communication system 400 according to an embodiment described with reference to FIG. 4, although the base stations 410 and 412 and the terminal 420 may perform cooperative communication, the following terminals may be used. There may be difficulties in the recovery of the received signal with a UE.

That is, when the first base station 410 and the second base station 412 transmit the same information, co-phasing between signals received from other base stations 410 and 412 is impossible, so that the multi-transmitter transmit gain. This can be reduced. In other words, phase correction between signals received at the other base stations 410 and 412 may not be performed, and thus the signal transmitted by the base stations may not be recovered or the recovery rate may be reduced. For example, a signal received by the first antenna group of the terminal is a signal received from the first base station 410.

And the signal received from the second base station 412

It consists of the sum of. Similarly, the signal received by the second antenna group of the terminal is a signal received from the first base station 410.

And the signal received from the second base station 412

It consists of the sum of. However, the phase mismatch between the signal received from the first base station 410 and the signal received from the second base station 412 may not be corrected, that is, the phase matching operation may not be possible.

Meanwhile, when the phase difference between the signals transmitted from the other base stations 410 and 412 is about 180 degrees or about 180 degrees, the signals are canceled with each other and thus the reception sensitivity of the signal may be reduced rather than the case of the single base station.

When the two base stations 410 and 412 transmit different information, the basis for distinguishing the information transmitted by the two base stations 410 and 412 in each receiving antenna group is the case of the first antenna group.

Wow

Intercorrelation or correlation, in the case of a second antenna group

Wow

It can be a difference or association between them. However, since each channel is not related to each other, there is no guarantee that the terminal 420 can distinguish signals transmitted from different base stations 410 and 412 in the cooperative multi-cell communication system 400.

5 is a flowchart illustrating a cooperative communication method between terminals and base stations of a cooperative multi-cell communication system according to another embodiment.

Referring to FIG. 5, in the cooperative communication method 500 of a terminal and base stations of a cooperative multi-cell communication system according to another exemplary embodiment, the terminal 420 receives reference signals transmitted from each base station 410 and 412. (S510, S515). In this case, the cooperative multi-cell communication system according to another exemplary embodiment is the cooperative multi-cell communication system 400 described with reference to FIG. 4, but is not limited thereto. Of course, the base station participating in the cooperative communication may be two as shown in FIG. 5, but is not limited thereto and may be three or more. However, for convenience of description, the base stations participating in the cooperative communication will be described as the first base station 410 and the second base station 412 as shown in FIG. 5.

Thereafter, the terminal 420 may estimate channel states or channel matrixes for each antenna by using the received reference signals (S520).

For example, the terminal 420 may estimate the downlink channel during downlink transmission. In particular, when transmitting an OFDM or Orthogonal Frequency Division Multiple Access (OFDMA) signal, the UE 410 may estimate a channel of each subband.

Certain signals or symbols may be inserted at regular or irregular intervals in the frequency-domain grid for estimation of the channel. In this case, the specific signal or symbol is variously named as a reference signal, a reference symbol, a pilot symbol, etc., but in this specification, the specific signal or symbol is referred to as a reference signal, but is not limited to the term. Do not. Of course, the reference signal is not only used for the estimation of the frequency domain channel but may also be used for position estimation, control information transmission / reception, transmission / reception of scheduling information, transmission / reception of feedback information, and the like, which are necessary in a wireless communication process between the terminal and the base station.

Different types of reference signals exist in downlink or uplink transmission, and new reference signals are defined and discussed for various purposes. For example, reference signals in uplink transmission include DM-RS (Demodulation RS) and SRS (Sounding RS). Reference signals in downlink transmission include DM-RS (Demodulation RS), CRS (Cell-specific RS), MBSFN RS, and UE-specific RS. In addition, there is a CSI-RS as a reference signal transmitted from a base station in order to obtain channel status information (CSI) of a center cell or neighbor cells in the downlink transmission. The CSI-RS may be used to report a Channel Quality Indicator (CQI) / Precoder Matrix Index (PMI) / Rank Index (RI). This CSI-RS is cell-specific to be distinguishable from each other in each cell included in the base station transmitting the CSI-RS and should be sufficiently scattered in frequency and time for low overhead.

Thereafter, the terminal 420 grasps each channel state or channel matrix of each base station 410 and 412, and then directly or indirectly sends channel information or channel state information related thereto to the serving base station or the main base station. The first base station 410 is fed back (S530). At this time, the channel state information (CSI ¹ and CSI ² ) is a propagation channel as shown in FIG.

Or indicators or indexes indicating precoding matrices suitable for this propagation channel, for example, PMI ¹ and PMI ² . The first base station 410 or a higher layer, which has received the feedback of the channel state information, selects base stations having good channel performance to form a cooperative base station set or a CoMP set, and includes at least one of the cooperative base station set or a CoMP set. May select a base station, for example, a second base station 412.

Subsequently, the first base station 410 transmits the information about the channel state or channel matrix corresponding to the second base station 412 to the second base station 412 corresponding to the neighboring base station or the cooperative base station in another X2 interface or one base station. It is transmitted to the link between the transport (link) responsible for inter-cell transmission (S540). At this time, the X2 interface is one of the X-series interfaces for data transmission through the public data network.

Thereafter, the first base station 410 and the second base station 412 may perform cooperative MIMO communication with the terminal 420 (S560 and S565). When the number of the base stations participating in the cooperative communication is three or more, the three or more base stations and the terminal 420 perform the cooperative MIMO communication.

However, in the cooperative multi-cell communication method 500 described with reference to FIG. 5, even if two or more base stations S410 and 412 transmit signals, the base station that reports channel information from the terminal corresponds to a serving base station or a main station. The first base station may be one (410). In this case, a precoding delay or a processing delay may occur in the process of implementing the precoding according to the channel information.

Hereinafter, a cooperative communication method 500 of a terminal and base stations of a cooperative multi-cell communication system 400 according to an embodiment described with reference to FIG. 4 or a cooperative multi-cell communication system according to another embodiment described with reference to FIG. 5. A cooperative multi-cell communication system and a communication method thereof according to another embodiment capable of performing cooperative communication more effectively will be described.

6 is a conceptual diagram of a cooperative multi-cell communication system according to another embodiment.

Referring to FIG. 6, in a cooperative multi-cell communication system 600 according to another embodiment, two or more base stations, for example, two base stations 610 and 612 and a terminal 620 perform cooperative communication. The first base station 610 includes an antenna array including antennas polarized into two antenna groups 610a and 610b, and the second base station 612 includes two antenna groups 612a and 612b. And an antenna array including antennas polarized by the antenna, and a propagation channel between the first base station 610 and the terminal 620

And the propagation channel between the first base station 610 and the terminal 620

In this regard, it may be the same as or substantially the same as the cooperative multi-cell communication system 400 according to another embodiment described with reference to FIG. 4.

However, in the cooperative multi-cell communication system 600 according to another embodiment, the two base stations 610 and 612 are precoding matrices, respectively.

And precoding matrices

Each of the data symbols to be transmitted to the terminal 620 without precoding

and

By using the data symbols transmitted to the terminal 620 can be precoded.

That is, the first base station 610 nulls or sets the power to the antennas corresponding to the second antenna group 610b of the first base station, so that the signal is not propagated to the air without first propagating the signal to the first base station. Only the antennas corresponding to the antenna group 610a propagate the signal to the air. Meanwhile, the second base station 612 nulls or “0” s power to antennas corresponding to the first antenna group 612a of the second base station having the same polarity as the first antenna group 610a of the first base station. In this way, the signal may be propagated to the air by only antennas corresponding to the second antenna group 612b of the second base station without propagating the signal to the air.

In other words, the first base station 610 sets the values of the components corresponding to the antennas corresponding to the second antenna group 610b among the components of the precoding matrix to nulling or “0” and to the first antenna. The data symbols may be precoded using a precoding matrix that retains only the components corresponding to the antennas corresponding to the group 610a. On the other hand, the second base station 612 sets the values of the components corresponding to the antennas corresponding to the first antenna group 612a of different polarity among the components of the precoding matrix to be nulling or “0”. The data symbols may be precoded using a precoding matrix that maintains only the components corresponding to the antennas corresponding to the second antenna group 612b.

At this time, the antenna group in which the first base station 610 nulls or sets the values of the components to “0” is a co-phase element for performing phase matching.

It may be an antenna group including a. Because the first base station 610 corresponds to the serving base station, the terminal 620 receives the channel state information from the terminal 620 to perform the location matching operation of the cooperative communication between the first base station 610 and the second base station 612. .

On the contrary, an antenna group in which the second base station 612 nulls or sets the value of the elements to “0” is a co-phase element in which phase matching is performed.

It may be an antenna group that does not include.

Therefore, since the first base station 610 uses only one group 610a of the two antenna groups 610a and 610b, the antenna power can be doubled. Similarly, since the second base station 612 uses only one group 612b of the two antenna groups 612a and 612b, respectively, the antenna power can be doubled.

In this case, the power of the antennas is nulling or “0” or the value of the elements is nulling or “0” in the physical sense, as well as substantially propagating the signal to the air as well as when no antenna power exists at all. This case includes a case in which the signal propagates in the air to an unreasonable or meaningless level.

The signals received by the two antenna groups of the terminal 620 are as shown in the following equation.

[Equation 19]

In this case, X _P and X _M may be different information (X _P ≠ X _M ) or the same information (X _P = X _M = x).

The signals received by the two antenna groups of the terminal 620 each include a co-phase element that performs a phase matching operation. Accordingly, since the first base station 610 corresponding to the serving base station selects a co-phase element, for example, 1, -1, j, and -j, the phase matching operation can be performed.

7 is a conceptual diagram of a cooperative multi-cell communication system according to another embodiment.

Referring to FIG. 7, in the cooperative multi-cell communication system 700 according to another embodiment, two or more base stations, for example, two base stations 710 and 712 and a terminal 720 perform cooperative communication. The first base station 710 includes an antenna array including antennas polarized into two antenna groups 710a and 710b, and the second base station 712 includes two antenna groups 712a and 712b. And an antenna array including antennas polarized by the antenna, and a propagation channel between the first base station 710 and the terminal 720

And the propagation channel between the first base station 710 and the terminal 720

In this regard, it is the same as or substantially the same as the cooperative multi-cell communication system 400 according to another embodiment described with reference to FIG. 4 or the cooperative multi-cell communication system 600 according to another embodiment described with reference to FIG. 6. May be the same.

However, in the cooperative multi-cell communication system 700 according to another embodiment, the two base stations 710 and 712 are precoding matrices, respectively.

And the precoding matrix

Without precoding the data symbols transmitted to the terminal 620 using the

and

By using the data symbols transmitted to the terminal 720 can be precoded.

That is, the first base station 710 does not propagate a signal to the air by nulling or powering the antennas corresponding to the second antenna group 710b of the first base station to the first base station of the first base station. Only the antennas corresponding to the antenna group 710a propagate the signal to the air. Meanwhile, the second base station 712 nulls or “0” s powers to antennas corresponding to the first antenna group 712a of the second base station having the same polarity as the first antenna group 710a of the first base station. In this way, the signal may be propagated to the air by only antennas corresponding to the second antenna group 712b of the second base station without propagating the signal to the air.

In other words, the first base station 710 nulls or “0” values of the components corresponding to the antennas corresponding to the second antenna group 710b among the components of the precoding matrix and nulls the first antenna. The data symbols may be precoded using a precoding matrix that maintains only the components corresponding to the antennas corresponding to the group 710a. On the other hand, the second base station 712 sets the values of the components corresponding to the antennas corresponding to the first antenna group 712a of different polarity among the components of the precoding matrix to be nulling or “0”. The data symbols may be precoded using a precoding matrix that maintains only the components corresponding to the antennas corresponding to the second antenna group 712b.

At this time, the antenna group in which the first base station 710 nulls or sets the value of the components to “0” is a co-phase element for performing phase matching.

It may be an antenna group including a. Because the first base station 710 corresponds to the serving base station, the terminal 720 receives the channel state information from the terminal 720 to perform the location matching operation of the cooperative communication between the first base station 710 and the second base station 712. .

On the contrary, the antenna group in which the second base station 712 nulls or sets the value of the elements to “0” is a co-phase element for performing phase matching.

It may be an antenna group that does not include.

Therefore, since the first base station 710 uses only one group 710a of the two antenna groups 710a and 710b, the antenna power can be doubled. Similarly, since the second base station 712 uses only one group 712b of the two antenna groups 712a and 712b, respectively, the antenna power can be doubled.

The signals received by the two antenna groups of the terminal 720 are as shown in the following equation.

[Equation 20]

In this case, X _P and X _M may be different information (X _P ≠ X _M ) or the same information (X _P = X _M = x).

The signals received by the two antenna groups of the terminal 720 each include a co-phase element that performs a phase matching operation. Accordingly, since the first base station 710 corresponding to the serving base station selects a co-phase element, for example, 1, -1, j, and -j, phase matching may be performed.

8 is a flowchart illustrating a cooperative communication method between terminals and base stations of a cooperative multi-cell communication system according to another embodiment.

Referring to FIG. 8, in the cooperative communication method 800 of a terminal and base stations of a cooperative multi-cell communication system according to another exemplary embodiment, the terminal 820 receives reference signals transmitted from each base station 810, 812. (S810, S815). In this case, the terminal 820 may receive all reference signals for all transmission antennas of the base stations 810 and 812, for example, eight transmission antennas. In particular, when the transmission antennas of the base stations 810 and 812 are polarized, the terminal 820 may receive reference signals of the polarized antennas.

At this time, the cooperative multi-cell communication system according to another embodiment is a cooperative multi-cell communication system (400, 500, 600, 700) described below, but is not limited thereto. Of course, at this time, the base stations participating in the cooperative communication may be two, as shown in FIGS. 5 to 7, but may be three or more. However, for convenience of description, two base stations participating in the cooperative communication will be described as the first base station 810 and the second base station 812.

Thereafter, the terminal 820 may estimate channel states or channel matrices of each antenna of the base stations 810 and 812 using the received reference signals (S820).

Thereafter, the terminal 820 identifies each channel state or channel matrix of each base station 810, 812 and then directly or indirectly corresponds to the serving base station or channel state information CSI ¹ and CSI ² . The first base station 810 is fed back (S830).

At this time, the channel state information of the first base station 810 is a propagation channel.

It may be itself or an indicator or index indicating a channel matrix suitable for this propagation channel. For example, the terminal 820 selects a precoder matrix suitable for each of the base stations 810 and 812 when using 8 transmit antennas 8Tx, and prints PMI _n ¹ and PMI _n ² by factoring them. The channel information may be reported to the first base station 810.

In particular, when the first base station 810 performs two-stage precoding, the channel state information for the first base station 810 may be PMI1 _n ¹ and PMI2 _n ¹ which are indices for W ₁ and W ₂ . The channel state information for the second base station 812 may also be in the same form or format as the channel state information for the first base station 810, for example, PMI1 _n ² and PMI2 _n ² .

The terminal 820 may identify the channel states or channel matrices of the base stations 810 and 812 and report the channel information or channel state information CSI ¹ and CSI ² (S825). In step S830, the terminal 820 may report the reported channel state information to the first base station 810.

For example, the terminal 820 selects a precoder matrix suitable for each of the base stations 810 and 812 when using 8 transmit antennas 8Tx, and prints the precoder matrix to PMI _n ¹ and PMI _n ² . Instead of reporting to the first base station 810, the terminal 820 generates the parameters PMI _n ¹ and PMI _n ² for the precoding matrix suitable for use of the four transmit antennas 4Tx as channel information. In PMI _n ¹ and PMI _n ² , PMI _n ¹ includes information on co-phasing a phase mismatch between signals received at two base stations. In other words, if there are 2n transmit antennas of the first base station (n is a natural number greater than 1 or 1) and there are 2m transmit antennas of the second base station (m is a natural number greater than 1 or 1 not equal to or not equal to n). The terminal 820 may generate a factor or indicator for a suitable precoding matrix when using n transmit antennas and an indicator for one precoding matrix suitable when using m transmit antennas.

For another example, the terminal 820 may use a total of eight transmit antennas of the first base station 810 and four transmit antennas of the second base station 812, which may be used for one precoding matrix. One argument, PMI _n , can be created. In other words, there are 2n transmit antennas of the first base station 810 (n is a natural number greater than 1 or 1) and 2m transmit antennas of the second base station 812 (m is 1 or 1 which is equal to or not equal to n). Greater than a natural number), the terminal 820 may generate an indicator for one precoding matrix suitable for using (n + m) transmit antennas.

As can be seen through the above examples, only a portion of the antennas of the antennas in which the terminal 820 measures the channel through a reference signal, for example, common RS or CSI-RS (Channel Status Information-RS) The CSI can be estimated and reported to the base stations. This method may be applied to any type or mode of communication system or communication method regardless of cooperative multi-cell communication. For example, when only the strengths of some of the eight antennas are greater than or equal to a threshold value, only channel state information of the antennas may be estimated or only this channel state information may be transmitted to the base station. As a result, estimation and / or transmission of channel state information for unnecessary antennas can be eliminated.

In addition, as can be seen from the above examples, the UE 820 estimates channel state information only for some of the channel measurement values obtained by measuring a channel through a reference signal, for example, CRS or CSI-RS, You can report them. For example, if only CRS or CSI-RS transmission antennas among the eight CRS or CSI-RS transmission antennas have strengths greater than or equal to a threshold value, only channel state information of the corresponding antennas may be estimated or only this channel state information may be transmitted to the base station. have.

Thereafter, the first base station 810 transmits information on the channel state or channel matrix corresponding to the second base station 812 to the second base station 812 corresponding to the neighboring base station or the cooperative base station (S840). One factor PMI for one precoding matrix suitable for the terminal 820 using a total of eight transmit antennas with four transmit antennas of the first base station 810 and four transmit antennas of the second base station 812. _{If n} is reported, the first base station 810 generates a precoding matrix using PMI _n , and then prints a portion that should be used by the second base station 812 and transmits it within the X2 interface or one base station. The channel state information (CSI ² ) for the second base station 812 is transmitted to the second base station 812 through the inter-link.

Thereafter, the first base station 810 may perform cooperative MIMO communication with the terminal 820 (S850). In this case, the first base station 810 precodes the data symbol by using the channel state information of the first base station 810, the channel state information of the first base station 810, and the channel state of the second base station 812. Phase correction may be performed on the data symbol using the information (S835).

In other words, as described with reference to FIGS. 6 and 7, the first base station 810 uses the antennas corresponding to the second antenna group or the precoding matrix corresponding to the second antenna group to perform data symbols using only the components. Can be precoded. In this case, since the precoding matrix includes a phase matching element, the first base station 810 performs the phase correction of the data symbol by using the channel state information of the first base station 810 and the channel state information of the second base station 812. Can be done.

In more detail, when the first base station 810 performs two-stage precoding, PMI1 _t ¹ and PMI2 _t ¹ , which are indexes for W ₁ and W _{2, which} are channel state information for the first base station 810 at the time of “t”. The two-stage precoding of the data symbols can be performed by determining the precoding matrices using.

Thereafter, the second base station 812 may perform cooperative MIMO communication with the terminal 820 (S860). In this case, the second base station 812 may precode the data symbol using the channel state information of the second base station received from the first base station 810 (S855). In other words, as described with reference to FIGS. 6 and 7, the second base station 812 uses the antennas corresponding to the first antenna group or the precoding matrix corresponding to the first antenna group only to perform data symbols. Can be precoded. In this case, since the components of the precoding matrix corresponding to the first antenna group do not include a phase matching element, the second base station 812 does not perform phase correction of the data symbol.

Specifically, when the second base station 812 performs two-stage precoding, PMI1 _t ² and PMI2 _t ² , which are indexes for W ₁ and W _{2, which} are channel state information for the second base station 812 at the time “t”, are used. The two-stage precoding of the data symbols can be performed by determining the precoding matrices using.

The terminal 820 is the delay of the link between the transmission end or the channel state of the first base station 810 and the second base station 812 that is responsible for the transmission between the other cells in the X2 interface or one base station at the time "t + 1" The first base station 810 before updating the precoding matrix of the second base station 812, that is, receiving a reference signal from the second base station 812 and estimating the channel of the second base station 812 due to the delay in processing the information. In operation S870, a channel of the first base station 810 may be estimated by receiving a reference signal from the reference signal.

After step S870, the terminal 820 reports the channel state information (CSI _{t + 1} ¹ and CSI _{t + 1} ² ) for the first base station and the second base station to the first base station 810 in the same manner as step S830. The step may be repeated (S880). The terminal 820 may report the channel state information in the same manner as the step S825 of reporting the channel state information before the step S830 (S875).

At this time, the first base station 810 precodes the data symbol with the channel state information (CSI _{t + 1} ¹ ) of the first base station at time t + 1, and the channel for the first base station and the second base station at time t + 1. The phase correction may be performed using the channel state information CSI _t ² of the second base station at time t together with the state information CSI _{t + 1} ¹ and CSI _{t + 1} ² (S885). Thereafter, the first base station 810 may perform cooperative MIMO communication with the terminal 820 (S890). In detail, when the first base station 810 performs two-stage precoding, the first base station 810 may transmit channel state information (CSI _{t + 1} ¹ and CSI) for the first base station and the second base station at time _{t + 1. t + 1} ² ) and _two- stage precoding of data symbols using PMI1 _t ² and PMI2 _t ^{2, which} are indexes for W ₁ and W _{2, which} are channel state information for the second base station 810 at the time “t”, In more detail, phase matching may be performed. In addition, in the nulling and phase correction operations, the uplink is connected to the UE in an uplink, so that the transmitting terminal capable of acquiring channel information more smoothly performs the phase correction operation. By doing this, it is possible to reduce the effect of phase correction error due to the delay of channel information exchange through the X2 interface.

Meanwhile, when the number of the base stations participating in the cooperative communication is three or more, the three or more base stations and the terminal 820 perform the cooperative MIMO communication.

Accordingly, in the cooperative multi-cell communication method 800 described with reference to FIG. 8, the base stations may be configured in consideration of occurrence of a precoding delay or a processing delay in the process of implementing precoding according to channel information. Precoding or phase correction allows base stations to more efficiently collaborate and implement CoMP-compliant precoding with minimal reporting.

9 is a configuration diagram of each of the base stations and the terminal in the cooperative multi-cell communication system according to another embodiment.

Referring to FIG. 9, the cooperative multi-cell wireless communication system 900 according to another embodiment may include at least two base stations 910 and 912 for performing cooperative communication with the terminal 920. In this case, the terminal 920 and the base stations 910 and 912 perform transmission and reception of reference signals, exchange of channel information, and cooperative multiplex communication in the cooperative multicell wireless communication system described with reference to FIGS. 1 to 8.

The terminal 920 is an antenna array 921 for receiving a signal through a downlink channel, a post-decoder 922 for processing the received signal and decoding the original data symbol using a precoding matrix. An information feedback device 924.

Antenna array 921 may use multiple antennas. In this case, the antenna array 921 may form a polarized antenna array. In order to arrange more antennas in a limited space in a communication system, an antenna array may be implemented using a dual polarized antenna array in which two antennas having different polarizations are alternately installed.

The post decoder 922 corresponds to the precoders of the base stations 910 and 912 described later. The post decoder 922 transfers the reference signals received from the base stations 910 and 912 to the channel information feedback device 924.

The channel information feedback apparatus 924 may receive the reference signals and estimate the channels of the base stations 910 and 912 by using the reference signals. The channel information feedback device 924 includes channel information (hereinafter referred to as 'first channel status information') for the first base station described with reference to FIGS. 5 and 8 and channel information for the second base station (hereinafter, referred to as 'first'). Channel information, including '2 channel status information'. The channel information feedback device 924 may feed back the channel information to the first base station 910 corresponding to the serving base station.

An indicator or identifier (PMI) indicating a precoding matrix for the first base station 910 selected from the stored codebook for the first base station 910 may be generated as the first channel state information. Similarly, the channel information feedback apparatus 924 generates an indicator or identifier (PMI) indicating a precoding matrix for the second base station 912 selected from the stored codebook for the second base station 912 as the second channel state information. Can be.

In this case, the channel information feedback device 924 selects and prints a precoder matrix suitable for each of the base stations 910 and 912 when using eight transmit antennas 8Tx as described with reference to FIG. 8. PMI _n ¹ and PMI _n ² are generated as channel information, or the base stations 910 and 912 use the channel information PMI _n ¹ and PMI _n ² for a precoding matrix suitable for the use of four transmit antennas 4Tx. Generate one factor PMI _n for one precoding matrix suitable for use with a total of eight transmit antennas with four transmit antennas of the first base station 910 and four transmit antennas of the second base station 812 Can be generated.

The channel information feedback apparatus 924 may feed back one channel information including the first channel status information and the second channel status information to the first base station 910 and provide the first channel status information and the second channel status information. Separately, the first base station 910 may be fed back, or one channel information reporting the first channel state information and the second channel state information may be fed back to the first base station 910. The period, channel, or format through which the channel information feedback device 924 feeds back channel information may be various.

The channel information feedback apparatus 924 may feed back the aforementioned various types of channel information to one of the components of the first base station 910, for example, the scheduler 940.

The first base station 910 includes a layer mapper 930 for mapping a codeword to a layer, and a precoder 932 for precoding the layer-mapped data symbols using a precoding matrix, and a precoded signal to the air. antenna array 938 for transmitting on air. The first base station 910 includes a scheduler 940 that performs resource allocation and management of the first base station, such as determining a precoding matrix, determining a MIMO transmission mode, or selecting a terminal in MU-MIMO.

The precoder 932 may include a first precoder 934 and a second precoder 936 for precoding data symbols. In this case, the first precoder 934 and the second precoder 936 may precode the data symbols by their first precoding matrix and the second precoding matrix, respectively. As described with reference to FIGS. 6 and 7, the precoder 932 may precode the data symbol using only the components of the antennas corresponding to the second antenna group or the precoding matrix corresponding to the second antenna group. Can be.

Like the first base station 910, the second base station 912 also includes a layer mapper 942, a first precoder 946, and a second precoder 948, and an antenna array 950. And a scheduler 952.

As described with reference to FIGS. 6 and 7, the precoder 932 of the first base station 910 uses only components corresponding to antennas corresponding to the second antenna group or a precoding matrix corresponding to the second antenna group. The data symbol is precoded, and the precoder 944 of the second base station 912 uses the antennas corresponding to the first antenna group or the precoding matrix corresponding to the first antenna group using only the components. Can be precoded.

The antenna array 938 of the first base station 910 and the antenna array 950 of the second base station 912 are the dual polarized antenna arrays shown in FIGS. 3 and 4, 6, and 7. You can also implement the array using.

The scheduler 940 of the first base station 910 reports the channel information including the first channel state information and the second channel state information from the channel information feedback device 924 of the terminal 920 through the antenna array 938. Can receive feedback

The scheduler 940 of the first base station 910 uses the first precoder 934 as a basis for the first channel state information and / or the second channel state information included in the channel information reported from each terminal 920. The precoding matrices of the second precoder 936 are determined and the data symbols are precoded using the precoding matrices. In this case, as described with reference to FIG. 8, the scheduler 940 of the first base station 910 uses PMI1 _t ¹ and PMI2 _t ^1, which are first channel state information for the first base station 910 at the time “t”. By determining the precoding matrices, two-stage precoding of the data symbol can be performed. In particular, the scheduler 940 of the first base station 910 determines the precoding matrix to perform phase correction using the first channel state information for the first base station and the first channel state information for the second base station.

On the other hand, the second base station 912 may have a delay between the X-interface or a link between the transmitting end that is responsible for inter-cell transmission within one base station or processing delay of the channel state information of the first base station 910 and the second base station 912. Before the update of the precoding matrix, the " t + 1 " point of time, the scheduler 940 of the first base station 910 receives the channel state information (CSI _{t + 1} ) for the first base station and the second base station at the time _{t + 1.} ¹ and CSI _{t + 1} ² ) together with the data symbols using the PMI1 _t ² and PMI2 _t ² indexes for W ₁ and W _{2, which} are channel state information for the second base station 810, at the time “t”. Precoding, specifically phase matching.

On the other hand, the scheduler 940 of the first base station 910 transmits the second channel state information CSI ² of the second base station 812 to an X2 interface or an inter-transmission link that is responsible for inter-cell transmission within one base station. It passes to the second base station 912 through.

The second base station 912 may precode the data symbol with the second channel state information received from the first base station 910.

As a result, the first base station 910 and the second base station 912 may perform cooperative communication with the terminal 920.

10 is a flowchart illustrating a communication method of a transmitting apparatus according to another embodiment.

Referring to FIG. 10, a communication method 1000 of a transmitting apparatus according to another embodiment includes a reference signal transmitting step (S1010) of transmitting a reference signal for estimating a propagation channel to a terminal and a transmitting apparatus corresponding to a serving base station. In the case where the terminal or the transmitting apparatus corresponds to a cooperative base station, the channel information receiving step of receiving channel information through another transmitting apparatus (S1020), and transmitting the air pre-coded symbols or signals through two or more antennas ( S1030) may be included.

The transmitting step S1030 includes a layer mapping step S1032 of mapping a codeword to a layer, a precoding step S1034 of precoding symbols, and a transmission step of propagating a precoded symbol to the air through two or more antennas (S1036). ) May be included.

Each step described with reference to FIG. 10 is the same as described with reference to FIGS. 1 to 9, and thus a detailed description thereof will be omitted.

In the above, the communication method of the transmission apparatus according to another embodiment has been described. Hereinafter, the communication method of the reception apparatus according to another embodiment will be described.

11 is a flowchart of a communication method of a receiving apparatus according to another embodiment.

Referring to FIG. 11, a communication method 1100 of a receiving apparatus according to another embodiment includes a reference signal receiving step S1110 for receiving reference signals from transmitting apparatuses and a channel information transmitting step of transmitting channel information to the transmitting apparatus. In operation S1120, a transmission signal reception step S1130 for receiving a signal transmitted from a transmission device is included.

The channel information transmitting step S1120 includes a channel estimating step S1122 for estimating a channel with transmission apparatuses using reference signals, and includes first channel state information and second channel state information based on the estimated channels. A channel information generation step (S1124) of generating channel information, and a padback step (S1126) of feeding back the channel information to at least one of the transmitting apparatuses may be included.

 Each step described with reference to FIG. 10 is also the same as described with reference to FIGS. 1 to 9, and thus a detailed description thereof will be omitted.

Although the embodiments have been described in detail with reference to the drawings, the present invention is not limited thereto.

In the above-described embodiments, when two or more base stations transmit signals using one polarized dual antennas, one base station uses only one antenna group among the antenna groups and the other base station uses only antenna groups having different polarities. Although described as transmitting, the present invention is not limited thereto.

For example, as illustrated in FIGS. 12 and 13, one base station 1200 may include at least two antenna arrays 1210 and 1212. At this time, each of the antenna arrays 1210 and 1212 of one base station 1200 is cooperative communication in the same manner as the aforementioned base stations, for example, the first base station 610 and the second base station 612 of FIG. Can be performed. At this time, each of the antenna arrays 1210 and 1212 of one base station 1200 may perform cooperative communication with another base station or perform cooperative communication between the antenna arrays 1210 and 1212.

In the former case, each of the antenna arrays 1210 and 1212 of one base station 1200 may operate like the first base station 610 and the second base station 612 of FIG. 6. That is, one of the antenna arrays 1210 of one base station 1200 uses only one antenna group 1210b and another base station, for example, the first base station 610 of FIG. 6 has a different polarity antenna group 610a. ) Can also be used for MIMO transmission.

In the latter case, as shown in FIG. 13, all antennas included in the two antenna arrays 1210 and 1212 are used to transmit the reference signals, but one of the antenna arrays 1210 is one antenna group during MIMO transmission. Only 1210b may be used and another antenna array 1212 may transmit signals using only another antenna group 1212a.

At this time, the base station 1210 may include layer mappers and precoders corresponding to each of the antenna arrays 1210 and 1212, or may include one layer mapper and a precoder shared by the antenna arrays.

In the above embodiments, the number of transmit antennas of the base stations is described as eight, but is not limited thereto. For example, the number of transmit antennas of the base stations may be 2n (n is 1 or a natural number greater than 1). Similarly, the number of transmit antennas of the terminal may also be 2n (n is 1 or a natural number greater than 1).

In addition, in the above-described embodiment, the base station and the terminal have been described as using both the transmit antennas and the receive antennas. However, only some of the antennas may be used, or all and some may be selectively used.

Accordingly, in the present specification, two or more antenna arrays each including two or more antenna groups in one base station may be interpreted as separate base stations as described above.

In the above-described embodiment, two or more base stations and terminals are described as performing downlink cooperative communication. However, at least two terminals and at least one base station may perform uplink cooperative communication. In this case, each antenna array of the terminals may use one of two antenna groups.

In the above-described embodiment, the base station and the terminal (s) have been described as including two antenna groups, but may include three or more antenna groups to increase the space utilization. For example, three antenna groups may be polarized by 60 degrees each.

The above description is merely illustrative of the technical idea of the present invention, and those skilled in the art to which the present invention pertains may make various modifications and changes without departing from the essential characteristics of the present invention. Therefore, the embodiments disclosed in the present invention are not intended to limit the technical idea of the present invention but to describe the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments. The protection scope of the present invention should be interpreted by the following claims, and all technical ideas within the equivalent scope should be interpreted as being included in the scope of the present invention.

CROSS-REFERENCE TO RELATED APPLICATION

This patent application claims priority under Patent Application No. 10-2010-0138654, filed with South Korea on December 30, 2010, pursuant to Article 119 (a) (35 USC § 119 (a)). All content is incorporated by reference in this patent application. In addition, if this patent application claims priority to a country other than the United States for the same reason, all its contents are incorporated into this patent application by reference.

Claims (17)

1. In a cooperative multi-cell communication system,

   At least one of the at least one base station of the at least one base station transmitting a signal to the terminal through at least one antenna group of two or more antenna groups of different polarization; And

   The other base station except for the at least one base station of the base station transmits a signal to the terminal through the antenna group of the polarization polarization is different from the at least one antenna group of the two or more antenna groups of different polarization Cooperative communication method of a cooperative multi-cell communication system comprising a transmission step.
2. In a cooperative multi-cell communication system,

   The first base station transmits a signal to the terminal by precoding the data symbols using only components of a precoding matrix corresponding to at least one antenna group of two or more antenna groups of different polarizations; And

   The second base station precodes a data symbol using only components of a precoding matrix corresponding to the at least one antenna group of two or more antenna groups of different polarizations and the antenna group of a polarization having a different polarity, thereby providing a signal to the terminal. A cooperative communication method of a cooperative multi-cell communication system comprising the step of transmitting.
3. The method of claim 2,

   The components of the precoding matrix of the first base station include a phase match element,

   The components of the precoding matrix of the second base station do not include a phase coincidence element.
4. The method of claim 3,

   Receiving, by the first base station, channel information including channel state information of the first base station and channel state information of the second base station from the terminal;

   And the second base station further comprises receiving channel state information of the second base station from the first base station.
5. The method of claim 4, wherein

   In the receiving step of the first base station, the channel state information of the first base station corresponds to a precoding matrix suitable for using n transmit antennas when the number of transmit antennas of the first base station is 2n (n is 1 or greater than 1). The indicator indicates that the channel state information of the second base station is one free when the number of transmit antennas of the second base station is 2 m (m is a natural number larger than 1 or 1 which is equal to or not equal to n). A cooperative communication method of a cooperative multi-cell communication system, characterized in that the indicator for the coding matrix.
6. The method of claim 4, wherein

   In the receiving step of the first base station, 2n transmit antennas of the first base station (n is 1 or larger than 1) and 2m transmit antennas of the second base station (m is 1 or not equal to n And a natural number greater than 1, an indicator of one precoding matrix suitable for using (n + m) transmit antennas.
7. The method of claim 4, wherein

   In the transmitting step of the first base station, the first base station precodes the data symbol using the channel state information of the first base station and the channel state information of the second base station at time t and the first base station at t + 1. A cooperative communication method of a cooperative multi-cell communication system, comprising precoding data symbols using channel state information of a base station and channel state information of a second base station together with channel state information of a second base station at time t. .
8. In a cooperative multi-cell communication system,

   A base station of at least two or more base stations includes: receiving a channel information including channel state information of a base station and channel state information of another base station except the one of the base stations;

   By using the channel information, at least one of two or more antenna groups of different polarizations corresponding to some of the components of the precoding matrix used by the other base station to precode the data symbol, the polarity is different And transmitting a signal to the terminal by precoding a data symbol using only components of a precoding matrix corresponding to a polarization antenna group.
9. The method of claim 8,

   The components of its precoding matrix include phase matching elements,

   And the components of the precoding matrix of the other base station do not include a phase matching element.
10. The method of claim 8,

    And transmitting the channel state information of the other base station to the other base station.
11. In a cooperative multi-cell communication system,

    Receiving a signal transmitted through at least one antenna group of two or more antenna groups of different polarizations in at least one base station of the at least two base stations; And

    Receives a signal transmitted through an antenna group of a polarization having a polarity different from that of the antenna group in the at least one base station among two or more antenna groups of different polarizations of another base station except the at least one base station among the base stations Cooperative communication method of the terminal comprising the step of.
12. In a cooperative multi-cell communication system,

    Receiving a signal in which data symbols are precoded and transmitted using only components of a precoding matrix corresponding to at least one antenna group of two or more antenna groups of different polarizations of a first base station; And

    Receives a signal from which data symbols are precoded and transmitted using only components of a precoding matrix corresponding to the at least one antenna group of two or more antenna groups of different polarizations of a second base station and the antenna group of a polarization having a different polarity Cooperative communication method of the terminal comprising the step of.
13. The method of claim 12,

    The components of the precoding matrix of the first base station include a phase match element,

    The components of the precoding matrix of the second base station do not include a phase matching element.
14. The method of claim 13,

    And transmitting channel information including channel state information of the first base station and channel state information of the second base station to the first base station.
15. In a cooperative multi-cell communication system,

    Receiving a reference signal of the first base station;

    A first base station channel state information estimating step of estimating channel state information only for n antenna pairs of the first base station reference signal when there are 2n antenna pairs of different polarized antennas in the first base station;

    Receiving a reference signal of a second base station;

    When there are 2m antenna pairs of different polarized antennas in the second base station, channel state information is applied only to m antenna pairs (m is a natural number greater than or equal to 1 or greater than 1) of the second base station reference signals. Estimating a second base station channel state information; And

    And transmitting channel information including the channel information including channel information of the first base station and channel state information of the second base station to the first base station.
16. The method of claim 15,

    In the channel information transmission step, the channel state information of the first base station is an indicator for a suitable precoding matrix when using 2n transmit antennas.

    The channel state information of the second base station is an indicator for one precoding matrix suitable for the use of 2m transmit antennas.
17. The method of claim 15,

    In the channel information transmission step, the channel information is a cooperative communication method of the terminal, characterized in that the indicator for one precoding matrix suitable for using 2 (n + m) transmit antennas.

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