WO2012046998A2

WO2012046998A2 - Transmitting apparatus and communication method therefor, and receiving apparatus and communication method therefor

Info

Publication number: WO2012046998A2
Application number: PCT/KR2011/007328
Authority: WO
Inventors: 박경민
Original assignee: (주)팬택
Priority date: 2010-10-08
Filing date: 2011-10-04
Publication date: 2012-04-12
Also published as: KR20120036698A; WO2012046998A3

Abstract

Certain embodiments of the present invention relate to a wireless communication system, i.e. to a wireless communication system that uses multi-input multi-output (MIMO) antennas on both the transmitting end and on the receiving end.

Description

Transmission apparatus and its communication method, receiving apparatus and its communication method

The present specification relates to a wireless communication system, and relates to a wireless communication system using a multiple input multiple output antenna (MIMO) at both a transmitting and receiving end.

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

Currently, wireless communication systems such as 3GPP, Long Term Evolution (LTE), and LTE-A (LTE Advanced) are high-speed and large-capacity communication systems that can transmit and receive various data such as video and wireless data beyond voice-oriented services. In addition to the development of technology capable of transmitting large amounts of data comparable to wired communication networks, it was necessary to improve the system performance by minimizing the reduction of information loss and increasing the system transmission efficiency.

An object of the present invention is to provide a communication method of a transmission device.

Another object of the present invention is to provide a transmission apparatus.

Another object of the present invention is to provide a communication method of a receiving apparatus.

Another object of the present invention is to provide a receiving apparatus.

In one embodiment, a transmission apparatus including multi-stage precoders for transmitting a signal through two layers, the precoding matrix including four adjacent beamforming vectors for performing beam forming from the receiver A first channel state information indicating one, one of a first beamforming vector and a second beamforming vector of the four beamforming vectors, and a beam selection vector for selecting one of a third beamforming vector and a fourth beamforming vector; One of the combination of beam selection vectors for overlapping selection of the first beamforming vector, the beam selection vector combination for overlapping selection of the third beamforming vector, and the beam for overlapping selection of the second beamforming vector, including combinations; One of the beam selection vector combinations for overlapping selection of the selection vector combination and the fourth beamforming vector, and the first beamforming vector and the second beam. Containing one of the beam selection vector combinations for selecting the beam selection vector of the combination and the third beamforming vector for selecting a property vector and fourth beamforming vectors Alternatively, the combinations of the beam selection vector (S _a ^1, S _a channel information receiving step of receiving channel information including second channel state information indicating one of _a ² ); And multi-stage precoding using a first precoding matrix corresponding to the received first channel state information and a second precoding matrix corresponding to the received second channel state information to transmit a signal. It is possible to provide a communication method of the device.

Another embodiment includes a layer mapper that maps codewords to two layers; A first channel indicating one of precoding matrices including four adjacent beamforming vectors for beamforming a data symbol mapped to the layer by the layer mapper from a receiver; A beam selection vector including a combination of a first precoding matrix corresponding to the state information and beam selection vectors for selecting one of the first and second and the third and fourth of the four beamforming vectors And one of the combinations of the second and the third beam selection vectors, and one of the combinations of the fourth and the second and the third and the combination of the beam selection vectors. And one of the combinations of the beam selection vector (S _a ¹ , S _a ² ), optionally including one of a combination of A multi-stage precoder for precoding using a second precoding matrix corresponding to the indicated second channel state information; And an antenna array configured to transmit signals output from the precoder.

Another embodiment is a wireless communication system in which a transmitter including a multi-stage precoder for transmitting a signal over two layers transmits a signal, the method comprising: receiving a reference signal for estimating a propagation channel from the transmitter; And first channel state information indicating one of the precoding matrices including four adjacent beamforming vectors for performing beam forming, one of the first and second of the four beamforming vectors, and a third one. And a combination of beam selection vectors for selecting one of the fourth, a combination of beam selection vectors for overlapping the first, and a combination of overlapping selection for the third, and a combination of beam selection vectors for overlapping the second; Combinations of the beam selection vectors S _a ¹ , optionally including one of a combination of selecting a fourth and a combination of beam selection vectors for selecting a first and a second, and a combination for selecting a third and a fourth; S ² _a) of the communication method of a receiving apparatus comprising a transmission step of transmitting the information channel and a second channel state information indicative of the one in the transmitter It can provide.

Another embodiment is an antenna array for receiving a reference signal for estimating a propagation channel from a transmitter in a wireless communication system in which a transmitter including a multi-stage precoder transmitting a signal through two layers transmits the signal. ; And

First channel state information indicating one of the precoding matrices including four adjacent beamforming vectors for performing beam forming, and one of the first, second, and third and fourth of the four beamforming vectors. The combination of the beam selection vectors for selecting the other one and the combination of the beam selection vectors for selecting the first overlap and the combination of the third and overlapping selection, and the combination and the fourth of the beam selection vectors for the second overlapping selection. Combinations of the beam selection vectors S _a ¹ , S _a , optionally including one of a combination of overlapping selections, a combination of beam selection vectors for selecting first and second, and a combination for selecting third and fourth; ² ) a receiving device including a channel information feedback device for transmitting channel information including second channel state information indicating one of the transmitters to the transmitting device; Can be provided.

1 is a diagram schematically illustrating a wireless communication system to which embodiments are applied.

2 illustrates a wireless communication system in which a base station and a terminal exchange channel state information.

3 is a configuration diagram of each of a base station and a terminal according to an embodiment in a MIMO wireless communication system.

4 is a flowchart illustrating a communication method of a transmission apparatus according to another embodiment.

5 is a flowchart illustrating a communication method of a receiving apparatus 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 illustrates a wireless communication system to which embodiments are applied.

Wireless communication systems are widely deployed to provide various communication services such as voice and packet data.

Referring to FIG. 1, a wireless communication system includes a user equipment (UE) 10 and a base station 20 (BS).

Terminal 10 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), UT (User Terminal) in GSM ), SS (Subscriber Station), wireless device (wireless device), etc. should be interpreted as including the concept.

A base station 20 or a cell generally refers to a fixed station communicating with the terminal 10 and includes a Node-B, an evolved Node-B, and a Base Transceiver. May be called other terms such as System, Access Point, Relay Node

In the present specification, the terminal 10 and the base station 20 are two transmitting and receiving entities used to implement the technology or the technical idea described in the present specification and are used in a comprehensive sense and are not limited by the terms or words specifically referred to.

One embodiment may be applied to asynchronous wireless communication evolving into Long Term Evolution (LTE) and LTE-advanced through GSM, WCDMA, HSPA, and synchronous wireless communication evolving to CDMA, CDMA-2000 and UMB. 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.

The wireless communication system to which the embodiments are applied may support uplink and / or downlink HARQ and use channel quality indicator (CQI) for link adaptation. In addition, multiple access schemes for downlink and uplink transmission may be different. For example, downlink uses Orthogonal Frequency Division Multiple Access (OFDMA), and uplink uses Single Carrier-Frequency Division Multiple Access (SC-FDMA). ) Can be used.

In order to support high-speed information transmission to a user, a wireless communication system considers using a multiple input multiple output (MIMO) technique in which information is transmitted through the same band using an antenna array including multiple antennas. .

Meanwhile, in order to implement an effective MIMO system, the MIMO wireless communication system transmits feedback information about a propagation channel or feedback information about a precoder or a precoding matrix (hereinafter referred to as a precoding matrix) suitable for a propagation channel to increase transmission capacity. Provided to the transmitter.

In this case, in order to implement a closed loop MIMO (CL-MIMO) that feeds back feedback information to a transmitting device with a small feedback overhead, an implicit feedback technique that transmits codebook-based channel information or information on a transmission scheme suitable for a channel is a commercial communication system. Is being used by. The precision of reporting on information is closely related to the size of the codebook or the amount of digital factors included in the codebook. This correlation allows the accuracy of the report to be proportional to the feedback overhead.

Implicit feedback refers to digital information that is considered to be the most effective for limiting the information to be reported to the transmitter by the finite digital information values and expressing channel information measured in each reporting period. A method of selecting and reporting a factor indicating the selected digital information to a transmitting device (transmitter), for example, a base station. To implement this technique, a set of information consisting of finite digital information values must be designed, and the set of designed digital information is called a codebook.

In other words, a codebook is designed to represent channel information as finite (N) digital information. In consideration of all channel information that can be measured by a receiver (receiver), for example, a terminal, N digital values that can represent the channel information most effectively are selected and designed as a codebook. The receiving device compares the digital values registered in the codebook with the measured channel information in each report period, selects a digital value that best represents the measured channel information, and delivers it to the transmitting device.

In the case of the Long Term Evolution (LTE) or Long Term Evolution-Advanced (LTE-A) wireless communication system, an implicit method is to transmit information about a precoder matrix which is determined to be most suitable for the measured channel. Feedback techniques can be used.

In order to increase the precision of precoding, a wireless communication system according to another embodiment of the present invention uses a technique of applying a different precoding matrix for each subband, and precoding and Increase the accuracy of the feedback information.

In this technique, the subband precoder matrix is divided into 'broadband portion' and 'subband portion' to reduce the feedback overhead increase caused by subband-specific PMI feedback compared to the conventional technique of reporting one PMI over the entire band. The terminal may report this separately.

In order to perform subband precoding with less feedback overhead, the MIMO wireless communication system uses a dual structure precoding (precoder) matrix expressed as W = W1W2. A wireless communication system according to another embodiment of the present invention may perform dual structure precoding as shown in FIG. 3 in downlink transmission.

In this structure, W1 and W2 constituting the precoding matrix may be transferred from the terminal to the base station through PMI1 or PMI2, which are different precoding matrix indicators. W1 may be a precoding matrix selected for the entire system bandwidth. On the other hand, W2 is selected as one precoder matrix for the entire system bandwidth or one precoder matrix for each subband that is a subset of the system bands. May be selected.

In other words, the UE may report one W1 and a plurality of W2s within a reporting period, and transmits one digital factor value PMI1 indicating W1 for all bands for which the UE wants to receive a signal. After splitting into several subbands, the digital factor values PMI2 determined to be suitable for use as W2 in each subband may be reported to the base station. 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, W1 and W2 may have a structure as follows.

[Equation 1]

In Equation 1, W1 is [V _n 0; 0 V _n ] block diagonal matrix. W2 is a matrix that performs a co-phasing operation to correct for phase mismatch between antenna groups.

In this structure, W1 reported through PMI1 is a subset containing a total number of beamforming vectors, for example n (n is an integer of 1 or more) out of 32 beamforming vectors. W2 reported through PMI2 selects the beamforming vectors of r out of these n beamforming vectors (r is an integer greater than or equal to 1 less than n) and co-phasing. Do the work. At this time, W2 may repeatedly select the same beamforming vector, and r is a value determined by a transmission rank. The value of n may vary according to the value of rank r to be transmitted.

When performing rank 2 transmission, the precoder matrix W1 indicated by the digital index n may be as follows.

[Equation 2]

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

Consists of zeros and is

Is the same column vector as.

In particular, adjacent overlapping beams at V _n of W1, for example four adjacent beams, can be used to reduce the edge effect in frequency selective procoding. For convenience, in the present specification, the case _where the size of V _n is 4 will be described as an example. The magnitude of V _n is not limited to four.

Thus, for each rank, 16 W1 matrices are expressed in terms of the indices of the beams: [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 W1 matrix may be formed of non-adjacent beams.

Meanwhile, in the W1 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, W1 may coincide with the spatial covariance of the dual polarized antenna array (see 428 of FIG. 3) polarized at a constant distance as described with reference to FIG. 3.

In this case, V _n is beam forming vectors that perform beam forming, and may be expressed by Equation 3 below.

[Equation 3]

Equation 3 is expressed as Equation 3 in θ =An example of the case of π / 16.

[Equation 4]

As a simpler example of the size of V _n is 4, the form of W1 by PMI1 = n indicating the precoder matrix of W1 may be set as follows.

[Equation 5]

That is, each element of the codebook for reporting W1 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, V ₀ ³² = (1,1,1,1}, V ₁ ³² = ( 1, e ^{j (π / 16)} , e ^{j (2 π / 16)} , e ^{j (3 π / 16)} }, V ₂ ³² = (1, e ^{j (2 π / 16)} , e ^{j (3 π / 16)} , e ^{j (4 π / 16)} }, ..., V ₃₁ ³² = (1, e ^{j (31 π / 16)} , e ^{j (32 π / 16)} , e ^{j (33 π / 16 )} }

W2 simultaneously performs the operation of selecting r of the plurality of beamforming vectors included in W1 _k and the co-phasing operation. W2 may be defined as in Equation 6.

[Equation 6]

In this case, S _a ¹ and S _a ² are beam selection vectors for performing beam selection, and C _a is _a co-phase element for performing phase matching.

In this case, S _a ¹ selects a beamforming vector to be used for the first layer transmission when the value of PMI2 indicating W2 is a from four beamforming vectors selected by W1, and S _a ² represents W2. When PMI2 indicating a is a, a beamforming vector to be used for the second layer transmission is selected from four beamforming vectors selected by W1.

S _a ¹ and S _a ² may be defined as follows.

[Equation 7]

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

It can have a value of. In the above structure, when PMI2 = 2 and S _a ¹ = [1; 0; 0; 0], S _a ² = [0; 1; 0; 0], and C _a = 1, the shape of W2 is represented by Equation 6 Substituting S _a ¹ and S _a ² into

[Equation 8]

As a result, W2 represented by Equation 8 selects the first beamforming vector among the four beamforming vectors selected by W1 as the beamforming vector to be used for the first layer transmission, and W1 as the beamforming vector to be used for the second layer transmission. The second beamforming vector is selected from the selected four beamforming vectors.

Therefore, when W = W1 × W2 = W1 _{PMI1 = 2} × W2 _{PMI2 = 2} , it may be as shown in Equation (9).

[Equation 9]

W1 selects four beamforming vectors V ₄ to V ₇ by PMI1, and W2 selects V ₄ and V ₅ by S _a ¹ and S _a ² . And finally by C _a = 1

Co-phasing is performed as follows.

In summary. The UE examines the precoder matrix or beam forming vector to be used for each subband when reporting the precoder matrix, and N vectors (four according to Equation 4) determined to be most frequently used And define it as broadband part information and report it through PMI1. Equation 5 is an example of a case in which the UE selects four adjacent beamforming vectors when reporting broadband information. In addition to selecting the broadband portion information, the subband portion information is also determined and reported to the base station using PMI2. Equation 8 is an example of a case in which the UE selects two of the four beamforming vectors and performs a co-phasing operation when reporting subband information.

In one embodiment, a structure of W2 for performing rank2 transmission is presented. When performing rank 2 transmission, W1 selects a subset consisting of four beamforming vectors, and W2 selects two beamforming vectors from the four beamforming vectors, A co-phase element for performing phase matching between two beamforming vectors is selected.

There are ten methods for repeatedly selecting two beamforming vectors among the four beamforming vectors. This means that 4 bits are required for selecting the beamforming vectors.

The present invention proposes a method of expressing a phase coincidence selection operation of W2 in 3 bits, but expressing all beamforming vectors or precoding matrices in the same manner as in the case of using all 10 beamforming vector selection methods.

That is, the method of selecting two beamforming vectors by allowing overlap in the n beamforming vectors is a total of _n H ₂ = n (n + 1) / 2 by combination with repetition, which is 1 Is the sum of whole numbers from n to n. In the above-described structure, since W1 includes four beamforming vectors, there are 4 + 3 + 2 + 1 = total methods for selecting two beamforming vectors through S _a ¹ and S _a ² . Can be.

[Equation 10]

In this formula

Is a beam selection vector whose nth element is 1 and the remainder is 0. For example, e ₁ is [1; 0; 0; 0] in Equation 6, e ₂ is [0; 1; 0; 0], e ₃ is [0; 0; 1; 0], e ₄ may represent [0; 0; 0; 1].

Since using 4 bits to express 10 beam selections is inefficient, selection of a method of representing only 8 out of 10 cases in 3 bits may be considered. In other words, according to an embodiment, a codebook or a combination of beam selection vectors representing PMI2 reporting W2 in three bits may be designed.

However, simply reducing the size of feedback information fed back to the base station by the terminal reduces the number of precoding matrices that can be expressed through the combination of W1 and W2, thereby reducing the resolution of the precoding. For example, when (e ₁ , e ₃ ) and (e ₃ , e ₄ ) are excluded as a combination of eight beam selection vectors, the following configuration may be performed.

[Equation 11]

When the values of PMI1 are substituted and (e ₁ , e ₃ ) are excluded, V ₀ and V _{2 are} used simultaneously, V ₂ and V _{4 are} used simultaneously. … , V _2n, can not be selected for the V _{2n + 1} coexistence including four beamforming vectors of the first and third beamforming vector constituting W1. As a result, the resolution of the precoding that can be expressed through the combination of W1 and W2 is reduced.

Looking at the structure of W1, when PMI1 = 0, W1 selects V ₀ to V ₃ and when PMI1 = 1, selects V ₂ to V5, where the beamforming vector overlaps V ₂ and V ₃ in each subset. Select as possible. By using the superposition feature of W1, it is possible to express all combinations of four adjacent beamforming vectors without using all 10 combinations of W2 beam selection vectors.

As described above, the combination rule of the beam selection vector for expressing the adjacent four beamforming vector combinations by the 3-bit W2 beam selection is as follows.

The essential combinations are as follows.

Since the two beamforming vectors are superimposed by W1 corresponding to the adjacent PMI1, the next vector set can be represented by only one PMI1 value or only one W1.

Therefore, (S _a ¹ , S _a ² ) should be selected to represent the above combination. That is, the following (S _a ¹ , S _a ² ) must be set. In other words, combinations of beam selection vectors for selecting one of the first and second of the beamforming vectors constituting W1 and the other of the third and fourth must be included as essential component combinations.

Essential combinations:

Optional element combinations are as follows.

Some elements of the rank 2 configuration consisting of two combinations of four adjacent beamforming vectors may be represented by two PMI1 values or two W1.

That is, even if only one of the following combinations exists, all six combinations of the above can be expressed.

That is, the combination (e ₁ , e ₁ ) of the beam selection vectors overlappingly selecting the first of the beamforming vectors constituting W1 and the combination (e ₃ , e ₃ ) overlappingly selecting the third may be selectively included. This is because four adjacent beamforming vectors constituting W1 overlap two beamforming vectors. Specifically, in (e _{_1,} e ₁₎ of four adjacent beamforming vector that (e _{_3,} e ₃₎ to _{_{(V 0, V 1, V}} 2, V 3) overlapping the first to the V ₀ of the selected four This is because overlapping selection of the third ones V ₀ of the adjacent beamforming vectors V ₃₀ , V ₃₁ , V ₀ , V ₁ is the same. At this time, the first channel state information for W1 is PMI1 = 0 in the former and PMI1 = 15 in the latter.

Similarly, a combination (e ₂ , e ₂ ) of beam selection vectors for overlapping the second selection of the beamforming vectors constituting W1 and a combination (e ₄ , e ₄ ) for overlapping the fourth selection may be selectively included. Finally, a combination (e ₁ , e ₂ ) of beam selection vectors for selecting the first and second of the beamforming vectors constituting W1 and a combination for selecting the third and fourth (e ₃ , e ₄ ) may be optionally included. .

Therefore, if the (S _a ¹ , S _a ² ) combination is designed by including the four essential element combinations and selecting one from each of the three optional element combinations, the W2 beam selection is performed using seven combinations or three bits. In this case, all beamforming vector combinations for rank 2 transmission can be expressed.

This method proposes a method of setting eight (S _a ¹ , S _a ² ) combinations with three bits, and the combination of the other beam selection vector is selected from (1) each of the three selection element combinations. Add the most frequently used combination of the remaining three (S _a ¹ , S _a ² ) combinations, or (2) one of the eight cases that can be represented by 3 bits, or is reserved. One of the three (S _a ¹ , S _a ² ) combinations may be completed in any manner or a predetermined rule to complete the W2 beam selection.

In optional combination of three kinds of (e _{_1,} e ₁₎ and (e _{_3,} e ₃₎ of the (e _{_1,} e ₁₎ of which is selected and (e _{_2,} e ₂₎ and _{_{(e 4, e 4) (}} e Suppose _{_2,} e ₂₎ is selected and that (e _1, e ₂₎ and (e _3, e ₄₎ of the (e _1, e ₂₎ is selected.

In other words, the first case is selected one by one and the remaining three (S _a ¹ , S _a ² ) combinations, namely (e ₃ , e ₃ ) and (e ₄ , e ₄ ), (e ₃ , e ₄ ) Among the most frequently used combinations can be added. In the third case, one of the other three combinations of (S _a ¹ , S _a ² ), namely (e ₃ , e ₃ ) and (e ₄ , e ₄ ), (e ₃ , e ₄ ) To a predetermined rule.

For example, the above example is as follows.

[Equation 12]

In other words, the essential combinations (e ₁ , e ₃ ) and (e ₁ , e ₄ ), (e ₂ , e ₃ ), (e ₂ , e ₄ ) are essentially included and optional combinations, i.e. ( _{_{e 1, e 1): (}} e 3, e 3) of the (e _1, the _{_{e 1), (e 2,}} e 2) :( e 4, e 4) of the _{_{(e 2, e 2),}} (e ₁ , e ₂ ): select (e ₃ , e ₄ ) from (e ₃ , e ₄ ) and select the remaining three (S _a ¹ , S _a ² ) combinations, namely (e ₃ , e ₃ ) Since one of (e ₄ , e ₄ ) and (e ₁ , e ₂ ) is added (e ₄ , e ₄ ), the above combinations can be configured as beam selection vectors.

In this case, when configuring a combination of beam selection vectors, PMI1 may be expressed as follows.

At this time, when the _first of four adjacent beamforming vectors is overlapped with (e ₁ , e ₁ ), PMI1 = 2n may be reported. For example, to select a V ₀ of the n = 0 (PMI1 = 0) in the case (e _{_1,} e ₁₎ by the 4 adjacent beamforming vectors _{_{(V 0, V 1, V}} 2, V 3). If n = 1 (PMI1 = 2) (e 1, e 1) in the four adjacent beamforming vector _{_{(V 4, V 5, V}} 6, V 7) can be selected from V _4. The same applies to the case where n is other than 0 and 1.

In this case, when the third and fourth of four adjacent beamforming vectors are selected as (e ₃ , e ₄ ), PMI1 = 2n−1 may be reported. For example, n = 0 if _{(PMI1 = 15) (e 3} , e 4) of four adjacent beamforming vectors to choose from among _{_{_{V 0, V 1 (V 14}}} , V 15, V 0, V 1) have. If n = 1 (PMI1 = 1) (e 3, e 4) to four adjacent beamforming vector _{_{(V 2, V 3, V}} 4, V 5) can be selected from V _4, V _5. On the other hand, the case where n is other than 0 and 1 is also the same.

In the following cases, desired beamforming vectors may be selected using the same principle.

In this case, when the first and third of four adjacent beamforming vectors are selected as (e ₁ , e ₃ ), PMI1 = 2n may be reported.

In this case, when (e ₁ , e ₄ ) is selected as the first and fourth of four adjacent beamforming vectors, PMI1 = 2n may be reported.

In this case, when the second of four adjacent beamforming vectors is overlapped with (e ₂ , e ₂ ), PMI1 = 2n may be reported.

At this time, when the second and the third of four adjacent beamforming vectors are selected as (e ₂ , e ₃ ), PMI1 = 2n may be reported.

In this case, when the second and the fourth of four adjacent beamforming vectors are selected as (e ₂ , e ₄ ), PMI1 = 2n may be reported.

In this case, when the first of four adjacent beamforming vectors is overlapped with (e ₁ , e ₁ ), PMI1 = 2n + 1 may be reported.

In this case, when the third and fourth of four adjacent beamforming vectors are selected as (e ₃ , e ₄ ), PMI1 = 2n may be reported.

In this case, when the fourth of four adjacent beamforming vectors is overlapped with (e ₄ , e ₄ ), PMI1 = 2n may be reported.

In this manner, all cases in which rank 2 transmission is performed using a combination of two adjacent four beamforming vectors can be represented.

Combination of the beam selection vectors possible according to the above rule is shown in Table 1 below only by subscripts of the beam selection vectors. At this time, eight (S _a ¹ , S _a ² ) combinations are set by 3 bits. The combination of the other beam selection vector is selected from (1) three combinations of selection elements, and the remaining three ( S _a ¹ , S _a ² ) add the most frequently used combination of combinations, or (2) one of the eight cases that can be represented by three bits is reserved without use, or (3) Assume that one of the remaining three (S _a ¹ , S _a ² ) combinations used any scheme or predetermined rule. .

TABLE 1

As shown in FIG. 2, the aforementioned dual structure precoder enables signal transmission through a different beam for each subband when transmitting a signal to each terminal, and also reduces feedback overhead through dual structure feedback. Has an effect.

Although a wireless communication system to which the above embodiments are applied has been described below, a process of exchanging channel state information between a base station and a terminal in a wireless communication system when using a precoder having a multi-stage structure will be described with reference to FIGS. 2 and 3.

Referring to FIG. 2, the wireless communication system 100 stores at least one terminal, for example, n terminals 110, in the base station 120 and the base station 120, similarly to the wireless communication system of FIG. 1. It may include. The terminals 110 may be terminals currently connected or attempting additional access, but only one terminal is shown in FIG. 3.

The base station 120 includes a multi-stage precoder including at least two first and second precoders as described below. The base station 120 uses the first precoding matrices used for the first precoder and the first pre-coding matrices representing the first indexes indexing them and the second precoding matrices used for the second precoder and these. The second codebook 124 representing the second indexes to be indexed may be stored or generated.

In this case, the first codebook 122 may be stored, for example, in the form of Equation 2 or 5, and store only the beamforming vector such as W1 _{PMI1 = 0} = [V ₀ , V ₁ , V ₂ , V ₃ ]. It may also store only the indices of the beamforming vector, such as [0,1,2,3]. If the first codebook is configured to store only the beamforming vector, it can be expressed as shown in Table 2 below.

TABLE 2

Similarly, the second codebook 124 may store a combination of beam selection vectors, such as Equation 8, or the like. If the second codebook is configured based on the combination of essential elements of Equation 12, it can be expressed as shown in Table 3 below.

TABLE 3

The second codebook 124 may store 1 or j as C _{a, which} is _a co-phase element that performs a phase matching operation. That is, W2 simultaneously performs a task of selecting one of a plurality of beam forming vectors included in W1 _n and a co-phasing operation.

As described above, since W1 includes four beamforming vectors, there may be a total of 10 ways in which W2 selects four beamforming vectors through S _a ¹ and S _a ² . Therefore, using 4 bits to express 10 beam selections is inefficient, so only 8 out of 10 cases are represented by 3 bits, and the beam selection can express all combinations of four adjacent beamforming vectors. The combinatorial rule of vectors has been described above.

That is, the combinations of the essential beam selection vectors (S _a ¹ , S _a ² ) = (e ₁ , e ₃ ), which select one of the first and second and one of the third and fourth of the beamforming vectors constituting W1 ( Combination of the beam selection vectors and the third of the beam formation vectors constituting W1, which are essentially including e ₁ , e ₄ ), (e ₂ , e ₃ ), (e ₂ , e ₄ ) Combinations for selecting a duplicate (S _a ¹ , S _a ² ) = (e ₁ , e ₁ ) or (S _a ¹ , S _a ² ) = (e ₃ , e ₃ ) Combinations of beam selection vectors and the fourth overlapping selection (S _a ¹ , S _a ² ) = (e ₂ , e ₂ ) or (S _a ¹ , S _a ² ) = (e ₄ , e ₄ ), Combination of beam selection vectors for selecting the first and second and combinations for selecting the third and fourth (S _a ¹ , S _a ² ) = (e ₁ , e ₂ ) or (S _a ¹ , S _a ² ) = (e ₃ , e ₄ ) may optionally be included.

Since eight (S _a ¹ , S _a ² ) combinations can be represented by three bits, the combination of the other beam selection vector is selected from (1) each of the three selection element combinations and the remaining three (S _a ¹ , S _a ² ) add the most frequently used combination of combinations, or (2) one of eight cases that can be represented with three bits, is reserved without use, or (3) One of the three (S _a ¹ , S _a ² ) combinations can complete the W2 beam selection in any manner or with a predetermined rule.

When setting eight (S _a ¹ , S _a ² ) combinations with three bits, including the required component combinations and the optional component combinations, the combination of possible beam selection vectors according to the above rules is represented by subscripts of the beam selection vectors only. , Already mentioned in Table 1.

Referring to FIG. 2, in order to transmit and receive data between the terminal 110 and the base station 120, the sender side base station 120 transmits a reference signal 128, and the receiver side terminal 110 receives the reference signal. (128) can be used to estimate the channel. For example, the terminal 110 may estimate the downlink channel during downlink transmission. In particular, during OFDM transmission, the terminal 110 may estimate a channel of each subband. In contrast, the base station 120 may estimate the uplink channel during uplink transmission.

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 acquire channel state information (CSI) of a center cell or neighbor cells in the terminal 20 during 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.

The terminal 110 includes a basic first codebook 112 representing the first precoding matrices used for the first precoder and the first indexes for indexing them, and a second precoding matrices used for the second precoder; A second codebook 114 representing the second indexes indexing them may be stored or generated. The first codebook 112 and the second codebook 114 are the same or the same as the first codebook 122 and the second codebook 124 stored in the base station 120, respectively. Can be generated.

The terminal 110 may report / feed back the first channel state information 132 for the first precoding matrix selected from the first codebook 112 to the base station 120. In addition, each terminal 110 may determine a second precoding matrix and report / feed back the second channel state information 134 of the second precoding matrix to the base station 120.

When configuring the combination of the beam selection of W2 vector in the manner described above, if you want to select a V _4, V ₅ by, W1W2 when rendering the W1 and W2 of equation (9) at the CSI 1 and CSI 2 see. First, since the beamforming vectors are [V ₄ , V ₅ , V ₆ , V ₇ ], PMI1 = 2, and PMI2 that selects the first and second of these beamforming vectors must be determined. However, when the second codebook is composed of combinations of beam selection vectors as shown in Equation 12, the combination of beam selection vectors for selecting the first and second beamforming vectors does not exist, but instead of the beam selection vectors for selecting the third and fourth. The combination (e ₃ , e ₄ ) is present.

Accordingly, the terminal 110 may report PMI1 = 1 to the base station instead of PMI1 = 2, and may report PMI2 = 6 representing a combination (e ₃ , e ₄ ) of beam selection vectors for selecting the third and fourth instead. . At this time, the value of PMI2 is determined in the order of combinations of beam selection vectors in Equation 12, PMI2 = 0, PMI2 = 1,... PMI2 = 6 and PMI2 = 7, but not limited thereto.

In this case, the second channel state information may include 1 or j as 1 bit, which is _a co-phase element C _a performing a phase matching operation. In other words, the second channel state information may be 4 bits in total, 3 bits may represent a combination of beam selection vectors, and the remaining 1 bit may represent C _a , which is _a co-phase element.

The base station 120 receives the first channel state information and the second channel state information from the terminal 110 and then transmits each layer when the rank 2 is transmitted by the first channel state information and the second channel state information in the reverse order as described above. Beamforming vectors and beam selection vectors for may be determined.

In the above-described example, when the base station 120 receives a report of the first channel state information PMI1 = 1 and the second channel state information PMI2 = 6 from the terminal 110, the base station 120 has PMI1 = 1, so that Vn = Since [V ₂ , V ₃ , V ₄ , V ₅ ] and PMI2 = 6, it can be seen that V ₄ and V ₅ are selected by the combination (e ₃ , e ₄ ) of the beam selection vectors. In this case, the second channel state information may include, as one bit, C _a (1 or j), which is _a co-phase element performing a phase matching operation. In other words, the second channel state information may be 4 bits in total, 3 bits may represent a combination of beam selection vectors, and the remaining 1 bit may represent C _a , which is _a co-phase element.

The base station 120 uses the

channel state information

132 and 134 reported from each terminal 110 as a basis for the first precoder and the second precoder in the first codebook 122 and the second codebook 124. Determine the precoding matrices of and precode the data symbols using the precoding matrices.

Finally, the base station 120 transmits the precoded signal to the terminal 110. In contrast, the terminal 110 decodes the original data after receiving the signal.

In the case of using the multi-stage precoder, a process of exchanging channel state information between a base station and a terminal in a wireless communication system has been described. Hereinafter, a MIMO wireless communication system for transmitting and receiving channel ecological information will be described in detail.

Referring to FIG. 3, the MIMO wireless communication system may include a terminal 410 and a base station 420. In this case, the terminal 410 and the base station 420 perform a process of exchanging channel state information between the base station and the terminal in the wireless communication system described with reference to FIG. 2.

The terminal 410 is an antenna array 411 for receiving a signal through a downlink channel and a post-decoder 412 for processing the received signal and decoding the original data symbol using a precoding matrix. And an information feedback device 414.

Antenna array 411 may use multiple antennas. In this case, the antenna array 411 may form a polarized antenna array. In order to arrange more antennas in a limited space in a wireless communication system, an array may be implemented using a dual polarized antenna array in which two antennas having different polarizations are alternately installed.

The post decoder 412 corresponds to the first precoder 422 and the second precoder 424 of the base station 420. The post decoder 412 transmits the received reference signal to the channel information feedback device 414.

The channel information feedback device 414 may receive the reference signal and estimate the channel using the reference signal. The channel information feedback device 414 may generate channel information including the first channel state information and the second channel state information described with reference to FIG. 2. The channel information feedback device 414 may feed back this channel information to the base station 420.

The channel information feedback device 414 may be stored as a first codebook 112, for example, in the form of Equation 2 or 5, and W1 _{PMI1 = 0} = [V ₀ , V ₁ , V ₂ , V ₃ ] Only the beamforming vector may be stored as shown in the drawing, or only the indices of the beamforming vector may be stored as shown in [0, 1, 2, 3].

The channel information feedback device 414 may store the second codebook 114 in the form of Equation 8 or store combinations of beam selection vectors such as Equation 10. W2 simultaneously performs a task of selecting one of a plurality of beam forming vectors included in W1 _n and a co-phasing operation. The second codebook 124 may store 1 or j as C _{a, which} is _a co-phase element performing a co-phasing operation.

The channel information feedback device 414 may report / feed back the first channel state information 132 for the first precoding matrix selected from the first codebook 112 to the base station 120. In addition, the channel information feedback apparatus 414 may determine the second precoding matrix and report / feed back the second channel state information 134 for the second precoding matrix to the base station 120.

When configuring combinations of the beam selection vectors of W2 in the above-described manner, when W1 and W2 of Equation 9 are represented, channel state information 1 and channel state information 2 will be described when W4 and V5 are selected by W1W2. First, since the beamforming vectors are [V4, V5, V6, V7], PMI1 = 2, and PMI2 that selects the first and second of these beamforming vectors must be determined. However, when the second codebook is composed of combinations of beam selection vectors as shown in Equation 12, the combination of beam selection vectors for selecting the first and second beamforming vectors does not exist, but instead of the beam selection vectors for selecting the third and fourth. Combinations (e3, e4) are present.

Accordingly, the channel information feedback device 414 may report PMI1 = 1 to the base station instead of PMI1 = 2, and report PMI2 = 6 representing a combination (e3, e4) of beam selection vectors for selecting the third and fourth instead. have. At this time, the value of PMI2 is PMI2 = 0, PMI2 = 1,... In order of combinations of beam selection vectors in Equation 12. PMI2 = 6 and PMI2 = 7, but not limited thereto.

In this case, the second channel state information may include, as one bit, C _a (1 or j), which is _a co-phase element performing a phase matching operation. In other words, the second channel state information may be 4 bits in total, 3 bits may represent a combination of beam selection vectors, and the remaining 1 bit may represent C _a , which is _a co-phase element.

The base station 420 includes a layer mapper 421 that maps codewords to a layer, and a precoder 425 that includes precoding the layer mapped data symbols using a precoding matrix. antenna array 428 for transmitting in air. The precoder 425 may include a first precoder 422 and a second precoder 424 for precoding data symbols. In this case, the first precoder 422 and the second precoder 424 may precode the data symbols by their first precoding matrix and the second precoding matrix, respectively.

A characteristic of the precoder having the dual structure shown in FIG. 3 is that when the terminal reports channel state information for W1 and W2, the frequency bands to which W1 and W2 respectively correspond are different. On the other hand, the position of the precoder to feed back the first channel information for W1 and the second channel information for W2 shown in FIG. That is, the first channel information may be fed back to the second precoder 424 and the second channel information may be fed back to the first precoder 422.

Antenna array 428 of base station 420 may use multiple antennas. In this case, the antenna array 428 may form a polarized antenna array. In order to arrange more antennas in a limited space in a wireless communication system, an array may be implemented using a dual polarized antenna array in which two antennas having different polarizations are alternately installed. In this case, the

antenna arrays

411 and 428 are exemplarily described as using a dual polarized antenna array, but the present invention is not limited thereto.

The base station 420 may report / feedback the first channel state information and the second channel state information from the channel information feedback device 414 of the terminal 410 through the antenna array 428.

The base station 420 determines precoding matrices of the first precoder 422 and the second precoder 424 in the first codebook and the second codebook based on the channel state information reported from each terminal 410. The precoding matrices are used to precode the data symbols.

The feedback period or the interval between the first channel state information and the second channel state information may be different. For example, the first channel state information may be fed back to the base station 420 in a short feedback period / short term, and the second channel information may be fed back to the base station 420 in a long feedback period / long term. In other words, the long feedback period / long term and the short feedback period / short term mean relative to each other, and the long feedback period / long term means a longer period than the short feedback period / short term.

The MIMO wireless communication system for transmitting and receiving codebook restriction information and channel ecological information according to another embodiment has been described above. Hereinafter, a communication method of a transmission apparatus according to another embodiment will be described.

Referring to FIG. 4, a communication method 600 of a transmitter according to another embodiment includes a reference signal transmission step (S610) of transmitting a reference signal for estimating a propagation channel to a terminal, and first channel state information from the terminal. Channel information receiving step (S620) for receiving the channel information including the second channel state information, it may include a transmission step (S630) for propagating a precoded symbol or signal through the two or more antennas to the air.

The transmitting step 630 may include a layer mapping step S632 of mapping a codeword to a layer, a precoding step S634 of precoding symbols, and a transmission step of propagating precoded symbols through the two or more antennas to the air (S636). ) May be included.

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.

Referring to FIG. 5, in a communication method 700 of a receiving apparatus according to another embodiment, a reference signal receiving step S710 and a channel information transmitting step of transmitting first channel state information and second channel state information to a transmitting device. (S720).

In step S720, the terminal 10 may determine a first precoding matrix and report / feed back the first channel state information 132 to the base station 120. In addition, each terminal 110 may determine a second precoding matrix and report / feed back the second channel state information 134 of the second precoding matrix to the base station 120.

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

Embodiments as described above may be applied to uplink / downlink MIMO systems, as well as a single cell environment, as well as a coordinated multi-point transmission / reception system (CoMP) and heterogeneous networks. It may be applied to all uplink / downlink MIMO systems.

In the above-described embodiment, a communication method and system for configuring and transmitting channel information with reference to rank 2 have been described, but the present invention is not limited thereto. Ranks 1 and 3 through 8 may apply in the same manner or system.

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 quadrupole antenna array. In addition, the present invention is not limited to the polarized antenna array but may be applicable to a general antenna array.

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 APPLICATIONCROSS-REFERENCE TO RELATED APPLICATION

This patent application claims priority under No. 119 (a) (35 USC § 119 (a)) of the Patent Application No. 10-2010-0098513, filed with Korea on 8 October 2010. 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

In a transmission device including a multi-stage precoder for transmitting a signal through two layers,

First channel state information indicating one of the precoding matrices including four adjacent beamforming vectors for beamforming from a receiver, the first beamforming vector and the second of the four beamforming vectors; A combination of beam selection vectors for selecting one of the beamforming vectors, one of the third beamforming vector, and a fourth beamforming vector, and a combination of beam selection vectors and third beamforming for overlapping selection of the first beamforming vector; One of the beam selection vector combination for overlapping selection of the vector, one of the beam selection vector combination for overlapping selection of the second beamforming vector, and the beam selection vector combination for overlapping selection of the fourth beamforming vector, and the first beam Combination of beam selection vectors for selecting the formation vector and the second beamforming vector, and selecting the third and fourth beamforming vectors Beam selection vector one of the combinations optionally including, in a combination of the beam selection vector (S a 1, S a 2 ) the channel information for receiving channel information for a second channel state information indicating one of to group Receiving step; And

And transmitting a signal by precoding multiple stages using a first precoding matrix corresponding to the received first channel state information and a second precoding matrix corresponding to the received second channel state information. Communication method.
The method of claim 1,

And the second channel state information further includes information about a co-phase element performing a co-phasing operation.
The method of claim 2,

The first precoding matrix is
(V n is beam forming vectors for performing beam forming,
Is a column vector of 0 and the same size as V n, and the second precoding matrix is
(S a 1 , S a 2 are beam selection vectors that perform beam selection, and C a is represented by a co-phase element that performs phase matching). A communication method of a transmitting device, characterized in that.
The method of claim 1,

One of the combinations (S a 1 , S a 2 ) of the beam selection vectors indicated by the second channel state information is a combination of beam selection vectors for overlapping the first selection and a beam selection vector for overlapping the third selection. The combination of one of the combinations of the beam selection vectors to select the second and the second and the beam selection vectors to overlap the fourth and the combination of the beam selection vectors to select the first and the second and the third and the fourth. Selecting one of the beam selection vectors that selectively includes one of a combination of beam selection vectors, and selecting one of the most frequently used combinations among the remaining combinations or a predetermined rule; .
A layer mapper that maps codewords to two layers;

A first channel indicating one of precoding matrices including four adjacent beamforming vectors for beamforming a data symbol mapped to the layer by the layer mapper from a receiver; A beam selection vector including a combination of a first precoding matrix corresponding to the state information and beam selection vectors for selecting one of the first and second and the third and fourth of the four beamforming vectors One of the combinations of the first and second combinations of beam selection vectors, and one of the combinations of the second and second beam selection vectors. And one of the combinations of the beam selection vector (S a 1 , S a 2 ), optionally including one of a combination of A multi-stage precoder for precoding using a second precoding matrix corresponding to the indicated second channel state information; And

And an antenna array for transmitting signals output from the precoder.
The method of claim 5,

The second channel state information further includes information on a co-phase element for performing a co-phasing operation.
The method of claim 6,

The first precoding matrix is
(V n is beam forming vectors for performing beam forming,
Is a column vector of 0 and the same size as V n, and the second precoding matrix is
(S a 1 , S a 2 are beam selection vectors that perform beam selection, and C a is represented by a co-phase element that performs phase matching). Transmitter characterized in that.
The method of claim 5,

One of the combinations (S a 1 , S a 2 ) of the beam selection vectors indicated by the second channel state information is one of a combination of beam selection vectors that select the first overlap and a combination that selects the third overlap. And optionally one of a combination of beam selection vectors for overlapping the second and a combination for overlapping selection for the fourth, and a combination of beam selection vectors for selecting the first and second and combinations for selecting the third and fourth. And selecting one of the beam selection vectors as the most frequently used combination among the remaining combinations, or selecting the predetermined one as a predetermined rule.
In a wireless communication system in which a transmitter including a multi-stage precoder transmitting a signal through two layers transmits a signal,

Receiving a reference signal for estimating a propagation channel from the transmitter; And

First channel state information indicating one of the precoding matrices including four adjacent beamforming vectors for performing beam forming, one of the first and second of the four beamforming vectors, and a third and A combination of beam selection vectors that select one of the fourth ones and a combination of beam selection vectors that select the first one repeatedly, and a combination of the third and overlapping selections; Combinations of the beam selection vector (S a 1 , S), optionally including one of the combination of selecting the overlap, and one of the combination of the beam selection vectors for selecting the first and second and the combination for selecting the third and fourth a 2) the communication method in the reception apparatus including a transmission step of transmitting the information channel and a second channel state information indicative of the one in the transmitter.
The method of claim 9,

And the second channel state information further includes information about a co-phase element performing a co-phasing operation.
The method of claim 10,

The precoding matrix corresponding to the first channel state information is
(V n is beam forming vectors for performing beam forming,
Is a column vector of 0 and the same size as V n ), and the precoding matrix corresponding to the first channel state information is
(S a 1 , S a 2 are beam selection vectors that perform beam selection, and C a is represented by a co-phase element that performs phase matching). Communication method of the receiving device, characterized in that.
The method of claim 9,

One of the combinations (S a 1 , S a 2 ) of the beam selection vectors indicated by the second channel state information is one of a combination of beam selection vectors that select the first overlap and a combination of the third selection. And optionally one of a combination of beam selection vectors for overlapping the second and a combination for overlapping selection for the fourth, and a combination of beam selection vectors for selecting the first and second and combinations for selecting the third and fourth. And selecting one of the beam selection vectors as the most frequently used combination among the remaining combinations, or selecting the selected one by a predetermined rule.
In a wireless communication system in which a transmitter including a multi-stage precoder transmitting a signal through two layers transmits a signal,

An antenna array for receiving a reference signal for estimating a propagation channel from the transmitter; And

First channel state information indicating one of the precoding matrices including four adjacent beamforming vectors for beamforming, and one of the first and second of the four beamforming vectors, and one of the third and fourth The combination of the beam selection vectors for selecting the other one and the combination of the beam selection vectors for selecting the first overlap and the combination of the third and overlapping selection, and the combination and the fourth combination of the beam selection vectors for the second selection Combinations of the beam selection vectors S a 1 , S a , optionally including one of a combination of overlapping selections, a combination of beam selection vectors for selecting first and second, and a combination for selecting third and fourth; 2 ) a reception device including a channel information feedback device for transmitting channel information including second channel state information indicating one of the channel information to the transmitter; .
The method of claim 13,

The second channel state information further includes information on a co-phase element for performing a co-phasing operation.
The method of claim 14,

The precoding matrix corresponding to the first channel state information is
(Vn is beam forming vectors for performing beam forming,
Is a column vector of 0 and the same size as Vn), and the precoding matrix corresponding to the second channel state information is
(S a 1 , S a 2 are beam selection vectors for performing beam selection, and C a is a co-phase element for performing phase matching). Receiving device, characterized in that.
The method of claim 13,

One of the combinations (S a 1 , S a 2 ) of the beam selection vectors indicated by the second channel state information is one of a combination of beam selection vectors that select the first overlap and a combination that selects the third overlap. And optionally one of a combination of beam selection vectors for overlapping the second and a combination for overlapping selection for the fourth, and a combination of beam selection vectors for selecting the first and second and combinations for selecting the third and fourth. And selecting one of the beam selection vectors as the most frequently used combination among the remaining combinations or selecting the predetermined one as a predetermined rule.