KR20120036698A - Transmitter and communicating method thereof, receiver, communicating method thereof - Google Patents

Abstract

PURPOSE: A transmitter, a communication method thereof, a receiver, and a wireless communication system are provided to improve the efficiency of system transmission through a MIMO antenna. CONSTITUTION: A base station(420) receives first CSI(Channel State Information) and second CSI from a channel information feedback unit(414) through an antenna array(428). The base station determines first precoder(422) and a precoding matrix of a second precoder in a first code book and a second code book based on channel state information. The base station performs precoding of data symbols.

Description

Transmitter and its communication method, receiver, its communication method {Transmitter and Communicating 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, high-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.

In one embodiment, a transmission apparatus including multi-stage precoder for transmitting a signal through two layers, the first precoding matrix including four adjacent beamforming vectors for performing beam forming from the receiving apparatus A combination of first channel state information indicating one of the first precoding matrices and beam selection vectors for selecting one of the first and second of the four beamforming vectors and the other of the third and fourth ones. One of the combination of the beam selection vectors selected by overlapping the first one and the combination of the third overlapping selection, one of the combination of the beam selection vectors selected by overlapping the second and the combination of the fourth selection, and the first and second And optionally one of a combination of beam selection vectors for selecting and a combination for selecting third and fourth. A channel information receiving step of receiving channel information including second channel state information indicating one of combinations (S _a ¹ , S _a ² ) and a first precoding matrix corresponding to the received first channel state information. And multi-stage precoding using a second precoding matrix corresponding to the received beam selection vector of the second channel state information to transmit a signal.

Another embodiment is a layer mapper for mapping a codeword to two layers. Four adjacent beams for beamforming a data symbol whose codeword is mapped to the layer by the layer mapper from a receiving device. A first precoding matrix corresponding to first channel state information indicating a first precoding matrix of one of the first precoding matrices including the formation vectors, and one of the first and second of the four beamforming vectors; One of the combination of beam selection vectors that selects the first one and the third and the combination of beam selection vectors that overlaps the third, and the second and the second beam selection. One of the combination of the vectors and the combination of the fourth, and a combination of the beam selection vectors to select the first and second and the third Comprises one of a combination of selecting fourth Optionally, the corresponding to the beam selection vector corresponding to the second channel state information indicative of one of a combination of the beamforming vector _{^{(S a 1, S a 2}} ) The present invention can provide a transmitter including a multi-stage precoder for precoding using two precoding matrices and an antenna array for transmitting signals output from the precoder.

Another embodiment is a step of receiving a reference signal for estimating a propagation channel from a transmitter and a beam in a wireless communication system in which a transmitter including a multi-stage precoder transmitting a signal over two layers transmits the signal. First channel state information indicating one of the first precoding matrices of the first precoding matrices including four adjacent beamforming vectors for performing beam forming and the first and second of the four beamforming vectors. One of the combinations of the beam selection vectors that select one of the other ones of the third and the fourth, and the combination of the beam selection vectors that select the first overlap and the combination of the third selection, and the second overlap One of a combination of beam selection vectors and a combination of fourth selection, and beam selection to select first and second Comprises one of a combination of selecting the emitters of the combination with the third and fourth Alternatively, the combination of the beamforming vector _{^{(S a 1, S a 2}} ) channel and a second channel state information indicative of the one of the information It is possible to provide a communication method of a receiving apparatus including a transmitting step of transmitting to the transmitting apparatus.

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 first precoding matrices of the first precoding matrices including four adjacent beamforming vectors for performing beam forming and the first of the four beamforming vectors. And a combination of beam selection vectors that select one of the second and the other of the third and the fourth, and a combination of beam selection vectors that overlap the first and a combination of the third and the second One of the combinations of the beam selection vectors to be selected, and one of the combinations to select the fourth, and the first and second Comprises one of a combination of selecting the combination of the third and fourth of the beam selection vector optionally, and a second channel state information indicative of one of a combination of the beamforming vector _{^{(S a 1, S a 2}} ) It is possible to provide a receiving apparatus including a channel information feedback apparatus for transmitting channel information to the transmitting apparatus.

1 is a diagram schematically illustrating a wireless communication system to which embodiments are applied.
2 is a cross-sectional view of a transmitting end or a transmitting apparatus (base station) for performing layer mapping and precoding.
3 illustrates a wireless communication system in which a base station and a terminal exchange beam limitation information and channel state information during beam limitation.
4 is a configuration diagram of each of a base station and a terminal according to an embodiment in a MIMO wireless communication system.
5 is a flowchart illustrating a communication method of a transmitting apparatus according to another embodiment.
6 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 the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

In addition, in describing the component of this invention, terms, such as 1st, 2nd, A, B, (a), (b), can be used. These terms are intended to distinguish the constituent elements from other constituent elements, and the terms do not limit the nature, order or order of the constituent elements. If a component is described as being "connected", "coupled" or "connected" to another component, that component may be directly connected to or connected to that other component, but there may be another configuration between each component. It is to be understood that the elements may be "connected", "coupled" or "connected".

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

That is, in the present specification, the base station 20 or the cell should be interpreted in a comprehensive sense indicating some areas covered by the base station controller (BSC) in the CDMA, the NodeB of the WCDMA, and the like. It is meant to cover various coverage areas such as microcell, picocell, femtocell and relay node communication range.

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.

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.

A TDD (Time Division Duplex) scheme in which uplink and downlink transmissions are transmitted using different time periods, or an FDD (Frequency Division Duplex) scheme in which they are transmitted using different frequencies can be used.

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). ) Is the same as 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 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 transmitted 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 precoding matrix for the entire system bandwidth or one precoding matrix for each subband that is a subset of the system band. 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.

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.

은 0으로 구성되고 크기가

와 동일한 열벡터이다.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 as in Equation 3 below.

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

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.

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, if 32 beamforming vectors are represented by beam indices n of 0 to 31, V ₀ ³² = (1,1, e ^{j (π / 16)} , e ^j as column vectors. ^{(2 π / 16)} }, V ₁ ³² = (1, e ^{j (π / 16)} , e ^{j (2 π / 16)} , e ^{j (3 π / 16)} }, V ₂ ³² = (1, e ^{j (2π / 16)} , e ^{j (3π / 16)} , e ^{j (4π / 16)} }, ..., V ₃₁ ³² = (0, e ^{j (31π / 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.

At this time, 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.

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.

의 값을 가질 수 있다. 상기의 구조에서, PMI1 = 2이고 S_a ¹=[1;0;0;0], S_a ²=[0;1;0;0], Ca=1인 경우 W2의 형태는 수학식6에 S_a ¹, S_a ²를 대입하면 다음과 표현할 수 있다.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 PMI1 = 2 and S _a ¹ = [1; 0; 0; 0], S _a ² = [0; 1; 0; 0], and Ca = 1, the shape of W2 is expressed in Equation 6 Substituting S _a ¹ and S _a ² gives us

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.

인 경우 수학식 9와 같을 수 있다.therefore,

In the case of Equation 9 may be equal to (9).

와 같이 위상 일치(co-phasing) 작업이 수행된다. 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 searches N vectors (four according to the example of Equation 4) that are determined to be most frequently used. It is selected and defined as broadband part information and reported 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 in which the UE selects two of the four beamforming vectors and performs a co-phasing operation when the subband information is reported.

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, a total of n (n + 1) / 2 types of methods for selecting two beamforming vectors from the n beamforming vectors are selected. In the above-described structure, since W1 includes four beamforming vectors, there are 4 + 3 + 2 + 1 = totals in which W2 selects four beamforming vectors through S _a ¹ and S _a ² . Can be.

은 n번째 요소가 1이고 나머지는 0인 빔선택벡터(ebeam selection vector)이다. 예를 들어, e₁은 수학식 6에서 [1;0;0;0]을, e₂는 [0;1;0;0]을, e₃는 [0;0;1;0]을, e₄는 [0;0;0;1]을 나타낼 수 있다. 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.

When the values of PMI1 are substituted and the combination of the beams is excluded in (e ₁ , e ₃ ), V ₀ , V _{2 are} used simultaneously, V ₂ , 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, W1 selects V ₀ to V ₃ when PMI1 = 0 and V ₂ to V4 when PMI1 = 1, and 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 duplicate 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 other one of the beamforming vectors is selected from (1) three selected element combinations and the remaining ones. 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.

In other words, the necessary element combinations (e ₁ , e ₃ ) and (e ₁ , e ₄ ), (e ₂ , e ₃ ), (e ₂ , e ₄ ) are essentially included and optional element 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.

In this case, when (e ₁ , e ₁ ) is the first selection of four adjacent beamforming vectors overlapping, PMI1 = 2n may be reported. For example, when n = 0 (PMI1 = 0), (e ₁ , e ₁ ) V ₀ may be selected from four adjacent beamforming vectors V ₀ , V ₁ , V ₂ , and 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 first and second 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. The same applies to the case where n is other than 0 and 1.

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 first and 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. In this case, _a combination of the eight (S _a ¹ , S _a ² ) combinations of three bits is selected by (1) each of the three selection element combinations and the remaining three ( S _a ¹ , S _a ² ) add the most frequently used combinations, or (3) select one of the three (S _a ¹ , S _a ² ) combinations, Assume that it was used. .

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.

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

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].

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 constructed based on the combination of necessary elements of Equation 12, it can be expressed as shown in the following table.

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 four bits to represent ten beam selections is inefficient, so only eight of the ten cases are represented by three bits, and the beam selection can represent all combinations of four adjacent beamforming vectors. The combinatorial rule of vectors has been described above.

That is, combinations of essential beam selection vectors (S _a ¹ , S _a ² ) = (e ₁ , e ₁ ), which select one of the first and second beam forming vectors constituting W1 and the other of the third and fourth ones, a combination of beam selection vectors that essentially include (e ₁ , e ₄ ), (e ₂ , e ₃ ), (e ₂ , e ₄ ) and overlapping the first of the beamforming vectors constituting W1; Combinations to select the third overlap (S _a ¹ , S _a ² ) = (e ₁ , e ₁ ) or (S _a ¹ , S _a ² ) = (e ₃ , e ₃ ) Combination of beam selection vectors and combinations of fourth selection (S _a ¹ , S _a ² ) = (e ₂ , e ₂ ) or (S _a ¹ , S _a ² ) = (e ₄ , e ₄ ) , A 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 beamforming 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 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. 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 thus formed for the selected one 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 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 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 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 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 a 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. However, the MIMO wireless communication system for transmitting and receiving channel ecological information will be described in detail.

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

Referring to FIG. 3, the MIMO wireless communication system 400 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 store the first codebook 112 in the form of, for example, Equation 2 or 5, and W1 _{PMI1 = 0} = [V ₀ , V ₁ , V ₂ , V ₃ ] and the like. Likewise, only the beamforming vector may be stored or only the indices of the beamforming vector may be stored as [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. In the second codebook 124, a co-phase element C _a , which performs a co-phasing operation, may store 1 or j.

The channel information feedback device 414 determines the thus formed first channel state information 132 and the second precoding matrix for the one selected from the first codebook 112 and the second channel state for the second precoding matrix. Information 134 may be reported / feedback to base station 120.

When the combinations of the beam selection vectors of W2 are configured in the above-described manner, when W1 and W2 of Equation 9 are expressed, the channel state information 1 and the channel state information 2 are described when W4 and V5 are selected by W1W2. First, since the beamforming vectors are [V4, V5, V6, V7], PMI1 = 2, and PMI2 which selects the first and second of these beamforming vectors should 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 the beam selection vectors to select 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 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 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 / feed back 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 term, and the second channel information may be fed back to the base station 420 in a long term. In other words, the long period / long term and the short period / short term mean relative to each other, and the long period / long term means a longer period than the short 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.

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

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 includes 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 to the air through two or more antennas (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.

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

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.

Although the above-described embodiment has described a communication method and system for configuring and transmitting channel information with reference to ranks 1 and 2, the present invention is not limited thereto. Ranks 3 to 8 may apply 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.

In the above description, all elements constituting the embodiments of the present invention are described as being combined or operating in combination, but the present invention is not necessarily limited to the embodiments. In other words, within the scope of the present invention, all of the components may be selectively operated in combination with one or more. In addition, although all of the components may be implemented in one independent hardware, each or all of the components may be selectively combined to perform some or all functions combined in one or a plurality of hardware. It may be implemented as a computer program having a. Codes and code segments constituting the computer program may be easily inferred by those skilled in the art. Such a computer program may be stored in a computer readable storage medium and read and executed by a computer, thereby implementing embodiments of the present invention. The storage medium of the computer program may include a magnetic recording medium, an optical recording medium, a carrier wave medium, and the like.

In addition, the terms "comprise", "comprise" or "having" described above mean that the corresponding component may be included, unless otherwise stated, and thus excludes other components. It should be construed that it may further include other components instead. All terms, including technical and scientific terms, have the same meanings as commonly understood by one of ordinary skill in the art unless otherwise defined. Terms commonly used, such as terms defined in a dictionary, should be interpreted to coincide with the contextual meaning of the related art, and shall not be construed in an ideal or excessively formal sense unless explicitly defined in the present invention.

The foregoing description is merely illustrative of the technical idea of the present invention, and various changes and modifications may be made by those skilled in the art 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.

Claims (24)

In a transmission device including a multi-stage precoder for transmitting a signal through two layers,
First channel state information indicating one first precoding matrix among one of first precoding matrices including four adjacent beamforming vectors for beamforming from a receiver, and the four beamforming One of a combination of beam selection vectors that essentially includes a combination of beam selection vectors for selecting one of the first and second and another of the third and fourth of the vectors, and a combination of beam selection vectors for overlapping the first selection, and And optionally including 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, channel for receiving channel information for a second channel state information indicative of one of a combination of the beamforming vector (s ¹ _a, s ^2, _a) positive Receiving step; 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 beam selection vector of the received second channel state information to transmit a signal; Communication method of a transmitting device comprising. 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 matrices

(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 matrices

(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). Communication method of the transmitting device, characterized in that. The method of claim 1,
One of the combinations (S _a ¹ , S _a ² ) of the beamforming vectors indicated by the second channel state information may be one of a combination of beam selection vectors for overlapping first selection and a combination of third and overlapping 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 and the most frequently used combination among the remaining combinations or selecting the predetermined one by a predetermined rule. The method of claim 4, wherein
Combinations of the beamforming vectors

When the elements of (e _n , e _m ) are represented, n and m values of the combination of (e _n , e _m ) are one of the combinations represented by the following table.

The method of claim 1,
The transmitting device is a communication method of the transmitting device, characterized in that the base station. A layer mapper that maps codewords to two layers;
A first pre of one of the first precoding matrices including four adjacent beamforming vectors for beamforming a data symbol mapped by the layer mapper to the layer by the layer mapper from a receiver; Essentially a combination of a first precoding matrix corresponding to the first channel state information indicating a coding matrix, and beam selection vectors for selecting one of the first and second of the four beamforming vectors and the other of the third and fourth One of the combination of the beam selection vectors including the first selection and the combination of the third selection, and the combination of the selection of the beam selection vectors and the second selection. The beam type, optionally including one of a combination of beam selection vectors for selecting a second and a combination for selecting third and a fourth A multistage precoder for precoding using a second precoding matrix corresponding to the beam selection vector corresponding to the second channel state information indicating one of the combinations of the sex vectors (S _a ¹ , S _a ² ); And
And an antenna array for transmitting signals output from the precoder. The method of claim 7, wherein
The second channel state information further includes information on a co-phase element for performing a co-phasing operation. The method of claim 8,
The first precoding matrices

(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 matrices

(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). Transmitter, characterized in that. The method of claim 8,
One of the combinations (S _a ¹ , S _a ² ) of the beamforming vectors indicated by the second channel state information may be one of a combination of beam selection vectors for overlapping first selection and a combination of third and overlapping 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 and the most frequently used combination from the remaining combinations, or selecting a predetermined rule. The method of claim 10,
Combinations of the beamforming vectors

When the elements of (e _n , e _m ) are represented, n and m values of the combination of (e _n , e _m ) are one of the combinations represented by the following table.

The method of claim 8,
And the transmitting device is a base station. 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 first precoding matrices of the first precoding matrices including four adjacent beamforming vectors for performing beam forming and the first of the four beamforming vectors. The combination of the beam selection vectors that selects one of the second and the other of the third and the fourth is essentially included, and the combination of the beam selection vectors that select the first overlap and the combination of the third and the second overlap The beamforming vector selectively comprising one of a combination of beam selection vectors to be selected and a combination of fourth and overlapping beam selection vectors; and a combination of beam selection vectors to select first and second and combinations to select third and fourth a combination of _(a s ^1, s ^2, _a) transmitting a channel of information and a second channel state information indicative of the one in the transmitter to the transmitting end The communication method of a receiving apparatus including a. The method of claim 13,
And a method for co-phase element performing the second channel state co-phasing operation. The method of claim 14,
The first precoding matrices

(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 matrices

(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). Communication method of the receiving device, characterized in that. The method of claim 13,
One of the combinations (S _a ¹ , S _a ² ) of the beamforming vectors indicated by the second channel state information may be one of a combination of beam selection vectors for overlapping the first selection and a combination of the third and overlapping 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 and the most frequently used combination among the remaining combinations or selecting the predetermined one by a predetermined rule. The method of claim 16,
When expressed in the combinations of the beamforming vector ^{_{(S a 1, S a 2}} ) (e n, e m) of elements of, (e _n, e _m) in combination n, m values are the combinations represented tabulated below Communication method of the receiving device, characterized in that one of.

The method of claim 13,
The transmitting apparatus is a base station, and the receiving apparatus is a communication method of a receiving apparatus, characterized in that the terminal. 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;
First channel state information indicating one of the first precoding matrices of the first precoding matrices including four adjacent beamforming vectors for performing beam forming and the first of the four beamforming vectors. The combination of the beam selection vectors that selects one of the second and the other of the third and the fourth is essentially included, and the combination of the beam selection vectors that select the first overlap and the combination of the third and the second overlap The beamforming vector selectively comprising one of a combination of beam selection vectors to be selected and a combination of fourth and overlapping beam selection vectors; and a combination of beam selection vectors to select first and second and combinations to select third and fourth a combination of _(a s ^1, s ^2, _a) channel for transmitting information of the channel and a second channel state information indicative of the one in the transmitter information The receiving device comprising a feedback device. 20. The method of claim 19,
The second channel state information further includes information on a co-phase element for performing a co-phasing operation. The method of claim 20,
The first precoding matrices

(Vn is beam forming vectors for performing beam forming,

Is a column vector of 0 and the same size as Vn), and the second precoding matrices

(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. 20. The method of claim 19,
One of the combinations (S _a ¹ , S _a ² ) of the beamforming vectors indicated by the second channel state information may be one of a combination of beam selection vectors for overlapping first selection and a combination of third and overlapping 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. Receiving apparatus, characterized in that for selecting one of the beam selection vectors and the most frequently used combination of the remaining combinations or by a predetermined rule. The method of claim 21,
When expressed in the combinations of the beamforming vector ^{_{(S a 1, S a 2}} ) (e n, e m) of elements of, (e _n, e _m) in combination n, m values are the combinations represented tabulated below Receiving device, characterized in that one of.

20. The method of claim 19,
The transmitting apparatus is a base station, and the receiving apparatus is characterized in that the terminal.

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