KR101617269B1 - The method for transmitting channel state information in wireless communication system - Google Patents

Abstract

A method for transmitting channel state information in a wireless communication system is disclosed. The UE can transmit a spatial channel matrix or a spatial channel covariance matrix regardless of the feedback type. In addition, information corresponding to noise and interference dispersion values of the entire bandwidth used by the UE for channel state information can be additionally transmitted. At this time, the UE can precisely and efficiently transmit the spatial channel matrix, the spatial channel covariance matrix, and the noise and interference distribution information, and can normalize and transmit the spatial channel matrix. The MS may allocate uplink resources to the BS and map a spatial channel matrix or a spatial channel covariance matrix according to a specific pattern to the allocated resources. At this time, the data can be mapped prioritized on the time axis or the frequency axis, and can be mapped to each symbol or each subcarrier. In addition to being allocated a PUSCH, the UE can map channel state information using a sounding reference signal (SRS) symbol region.

Channel state information, resources

Description

[0001] The present invention relates to a method for transmitting channel state information in a wireless communication system,

The present invention relates to a wireless communication system, and more particularly, to a method of transmitting channel state information.

Recently, a multiple input multiple output (MIMO) system has attracted attention as a broadband wireless mobile communication technology. A MIMO system refers to a system that increases data communication efficiency by using a plurality of antennas. The MIMO system can be divided into a spatial multiplexing scheme and a spatial diversity scheme depending on whether the same data is transmitted or not.

Spatial multiplexing refers to a method of transmitting data at high speed without increasing the bandwidth of the system by simultaneously transmitting different data through a plurality of transmission antennas. The spatial diversity scheme refers to a scheme in which transmission diversity can be achieved by transmitting the same data in a plurality of transmission antennas. One example of such a space diversity technique is space time channel coding.

In addition, the MIMO technique can be divided into an open loop method and a closed loop method depending on whether feedback of channel information from a receiving side to a transmitting side is performed. In the open-loop method, information is transmitted in parallel at the transmitting end. In the receiving end, a blast (BLAST) capable of detecting signals by repeatedly using ZF (Zero Forcing) and MMSE (Minimum Mean Square Error) And a space-time trellis code (STTC) scheme that can obtain transmission diversity and coding gain using a space region. And a closed antenna scheme is a TxAA (Transmit Antenna Array) scheme.

Hereinafter, a spatial channel matrix that can be used in the present invention will be briefly described.

Where H (i, k) is a spatial channel _{matrix, h r, t (i,} k) is element, Nr receiving antennas of the channel matrix H (i, k), Nt the number of transmitting antennas, r indicates a receiving antenna. T denotes an index of a transmission antenna, i denotes an index of an OFDM (or SC-FDMA) symbol, and k denotes an index of a subcarrier.

는 채널 행렬 H(i,k)의 요소(element)로서, i번째 심볼 및 k번째 부반송파상에서의 r번째 채널 상태 및 t번째 안테나를 의미한다.

Is an element of the channel matrix H (i, k), which means the i-th symbol and the r-th channel state on the k-th subcarrier and the t-th antenna.

In addition, a spatial channel covariance matrix that can be used in the present invention will be briefly described. The spatial channel covariance matrix can be represented by the symbol R.

이고, 여기서 H는 공간 채널 행렬을, R은 공간 채널 공분산 행렬을 의미한다. E[]는 평균(mean)을 의미하며, i는 심볼 인덱스, k는 주파수 인덱스를 의미한다.

, Where H denotes a spatial channel matrix and R denotes a spatial channel covariance matrix. E [] denotes mean, i denotes a symbol index, and k denotes a frequency index.

Singular Value Decomposition (SVD) is one of the most important methods for decomposing a rectangular matrix and is a technique widely used in signal processing and statistics. The singular value decomposition is a generalization of the spectral theory of a matrix to an arbitrary rectangular matrix. Using the spectral theory, an orthogonal square matrix can be decomposed into a diagonal matrix with an eigenvalue as a basis. Suppose that matrix H is an m × m matrix of real or complex elements. At this time, the matrix H can be expressed as a product of three matrices as follows.

이다. 이와 같이 세 행렬의 곱으로 나타내는 것을 특이값 분해라고 한다. 특이값 분해는 직교 정사각행렬만을 분해할 수 있는 고유값 분해보다 훨씬 일반적인 행렬을 다룰 수 있다. 이러한 특이값 분해와 고유값 분해 서로 관련되어 있다.Where U and V represent unitary matrices and Σ is an m × n diagonal matrix containing singular values that are not negative. The singular value

to be. The product of these three matrices is called singular value decomposition. Singular value decomposition can deal with a much more general matrix than eigenvalue decomposition, which can only decompose an orthonormal square matrix. These singular value decomposition and eigenvalue decomposition are related to each other.

When the matrix H is a Hermitian matrix with positive positive numbers, all eigenvalues of H are nonnegative real numbers. At this time, the singular value and singular vector of H are all non-negative real numbers of H eigenvalues. The singular value and singular vector of H are equal to the eigenvalues and eigenvectors of H.

Eigen Value Decomposition (EVD) can be expressed as follows.

Here, the eigenvalues may be λ _{1, ..,} λ _r .

SUMMARY OF THE INVENTION The present invention is directed to a method for transmitting channel state information in a wireless communication system.

The technical problems to be solved by the present invention are not limited to the technical problems and other technical problems which are not mentioned can be understood by those skilled in the art from the following description.

According to another aspect of the present invention, there is provided a method for transmitting channel state information, including: allocating uplink resources for transmitting channel state information from a base station; Each element corresponding to an upper triangle matrix in a spatial channel matrix or a spatial channel covariance matrix is mapped to the allocated resource on a symbol or a subcarrier basis and nulls or a garbage value is mapped on the mapped remaining region Mapping; And transmitting the mapped channel state information to the base station.

According to the present invention, accurate and efficient channel state information can be transmitted.

The effects obtained by the present invention are not limited to the above-mentioned effects, and other effects not mentioned can be clearly understood by those skilled in the art from the following description will be.

Hereinafter, preferred embodiments according to the present invention will be described in detail with reference to the accompanying drawings. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The following detailed description, together with the accompanying drawings, is intended to illustrate exemplary embodiments of the invention and is not intended to represent the only embodiments in which the invention may be practiced. The following detailed description includes specific details in order to provide a thorough understanding of the present invention. However, those skilled in the art will appreciate that the present invention may be practiced without these specific details. For example, the following detailed description is based on the assumption that the mobile communication system is a 3GPP LTE system, but it is applicable to any other mobile communication system except for the specific aspects of 3GPP LTE.

In some instances, well-known structures and devices may be omitted or may be shown in block diagram form, centering on the core functionality of each structure and device, to avoid obscuring the concepts of the present invention. In the following description, the same components are denoted by the same reference numerals throughout the specification.

In the following description, it is assumed that the UE collectively refers to a mobile stationary or stationary user equipment such as a UE (User Equipment) and an MS (Mobile Station). It is also assumed that the base station collectively refers to any node of a network end that communicates with a terminal such as a Node B, an eNode B, and a base station.

In a mobile communication system, a user equipment can receive information through a downlink from a base station, and the terminal can also transmit information through an uplink. The information transmitted or received by the terminal includes data and various control information, and various physical channels exist depending on the type of information transmitted or received by the terminal.

1 is a view for explaining physical channels used in a 3rd Generation Partnership Project (3GPP) LTE (Long Term Evolution) system, which is an example of a mobile communication system, and a general signal transmission method using the same.

In step S101, an initial cell search operation such as synchronizing with a base station is performed, such as when the power is turned off or the terminal that has newly entered the cell is powered on again. To this end, the UE can receive a Primary Synchronization Channel (P-SCH) and a Secondary Synchronization Channel (S-SCH: Secondary Synchronization Channel) from the BS to synchronize with the BS and acquire information such as a cell ID . Then, the terminal can receive the physical broadcast channel from the base station and acquire the in-cell broadcast information. Meanwhile, the UE can receive the downlink reference signal (DL RS) in the initial cell search step and check the downlink channel state.

Upon completion of the initial cell search, the UE receives a physical downlink control channel (PDCCH) and a physical downlink control channel (PDSCH) according to physical downlink control channel information to obtain more specific system information (S102).

On the other hand, if the base station is initially connected or there is no radio resource for signal transmission, the terminal can perform a random access procedure such as steps S103 to S106. To this end, the UE transmits a specific sequence as a preamble through a physical random access channel (PRACH) (S103), and transmits the preamble to the physical downlink control channel and the corresponding physical downlink shared channel A response message can be received (S104). In the case of the contention-based random access except for the handover, a conflict resolution procedure such as transmission of an additional physical random access channel (S105) and physical downlink control channel / physical downlink shared channel reception (S106) Resolution Procedure).

The MS having performed the procedure described above transmits a physical downlink control channel / physical downlink shared channel reception (S107) and a physical uplink shared channel (PUSCH) / physical downlink shared channel A physical uplink control channel (PUCCH) transmission may be performed (S108). At this time, the control information transmitted by the UE to the BS through the uplink or received from the BS by the UE includes a downlink / uplink ACK / NACK signal, a channel quality indicator (CQI), a precoding matrix A Precision Matrix Index (PMI), a Rank Indicator (RI), and the like. In the 3GPP (Third Generation Partnership Project) Long Term Evolution (LTE) system, a UE transmits control information such as a spatial channel matrix and a spatial channel covariance matrix in addition to the CQI, PMI, Through a physical uplink shared channel and / or a physical uplink control channel.

The UE may report to the serving BS the recommended transmission characteristics (e.g., CQI, PMI, RI) and other channel state information (CSI). Generally, the CSI feedback method includes a quantization CSI feedback method and an analogue CSI feedback method. Regardless of the type of the CSI feedback scheme, the CSI reported by the UE to the serving cell includes a spatial channel matrix H (hereinafter referred to as 'channel matrix H' or 'matrix H') or a spatial channel covariance matrix R Quot; covariance matrix R " or " matrix R ", etc.).

That is, the UE may transmit the spatial channel matrix H or the spatial channel covariance matrix R information as CSI feedback information to the serving base station, and may generate a noise variance (for example, Interference level) can be additionally transmitted. That is, the UE can transmit the noise plus interference variance information to the base station along with the spatial channel matrix H or the spatial channel covariance matrix R value.

In order for the UE to perform transmission of the CSI feedback information more accurately and efficiently, the UE can normalize the CSI and transmit the CSI to the serving BS. This normalization method may vary depending on the type of CSI feedback information transmitted by the UE.

First, a method in which a terminal normalizes and transmits analog CSI feedback information will be described.

When the MS transmits the analog CSI feedback information, the MS can normalize the channel matrix H and the noise variance value through the total power sum value of all symbols corresponding to the uplink resources allocated by the MS. A matrix element may be loaded in the uplink resource allocated by the corresponding terminal and then normalized using a power sum of one symbol having the largest power value among the matrix elements.

For example, if the UE is allocated M subbands with the best channel state of three (that is, M = 3) and the channel matrix H and / or the covariance matrix R for the best M subbands Assume that the noise and variance of the entire bandwidth can be reported to the base station. The noise and interference variance with each matrix R can be normalized as: < EMI ID = 1.0 >

값은 총 전력합 값 또는 가장 전력 크기가 큰 특정 심볼의 전력값이 될 수 있다.In Equation (1)

The value may be a total power sum value or a power value of a specific symbol having the largest power magnitude.

을 유도할 수 있고, 기지국은 상기 수학식 1과 같이 정규화된 양자화 R 행렬 피드백 정보에 기초하여 다음 수학식 2에 표현된 바와 같이, 최상의 부대역 m (m=1,2,...,M)개의 채널 용량(channel capacity)을 계산할 수 있다. From the above Equation 1,

, And the base station calculates the best subband m (m = 1, 2, ..., M) based on the normalized quantized R matrix feedback information as shown in Equation (1) ) ≪ / RTI > channel capacity.

Also, the base station can obtain rank, precoding matrix (or vector), MCS, and the like based on such information.

Hereinafter, a method of mapping CSI information to a resource allocated by a terminal and transmitting the CSI information will be described. First, a resource grid structure used in the LTE system for mapping the CSI information will be briefly described.

2 is a diagram illustrating an uplink time-frequency resource grid structure used in a 3rd Generation Partnership Project (3GPP) LTE (Long Term Evolution) system, which is an example of a mobile communication system.

개의 부반송파(subcarrier)와

개의 OFDM 심볼로 구성되는 도 2와 같은 자원 격자(resource grid)에 의해 묘사될 수 있다. 여기서,

은 상향링크에서의 자원 블록(Resource Block; RB)의 개수를 나타내고,

는 하나의 RB을 구성하는 부반송파의 개수를 나타내고,

는 하나의 상향링크 슬롯에서의 OFDM 심볼의 개 수를 나타낸다.

의 크기는 셀 내에서 구성된 상향링크 전송 대역폭에 따라 달라지며

을 만족해야 한다. 여기서,

는 무선 통신 시스템이 지원하는 가장 작은 상향링크 대역폭이며,

는 무선 통신 시스템이 지원하는 가장 큰 상향링크 대역폭이다.

=6이고

=110일 수 있지만, 이에 한정되는 것은 아니다. 하나의 슬롯 내에 포함된 SC-FDMA 심볼의 개수는 상위 계층에서 구성된 순환 전치(Cyclic Prefix, CP)의 길이 및 부반송파의 간격에 따라 다를 수 있다.Referring to FIG. 2, an uplink signal transmitted in each slot is

Subcarriers < RTI ID = 0.0 >

And can be described by a resource grid as shown in FIG. 2, which is composed of OFDM symbols. here,

Denotes the number of resource blocks (RBs) in the uplink,

Represents the number of sub-carriers constituting one RB,

Represents the number of OFDM symbols in one uplink slot.

Depends on the uplink transmission bandwidth configured in the cell

. here,

Is the smallest uplink bandwidth supported by the wireless communication system,

Is the largest uplink bandwidth supported by the wireless communication system.

= 6

= 110, but is not limited thereto. The number of SC-FDMA symbols included in one slot may be different depending on the length of a cyclic prefix (CP) configured in an upper layer and intervals of subcarriers.

-1 중 어느 하나의 값을 갖고, i는 0,..,

-1 중 어느 하나의 값을 갖는다. Each element in the resource grid is called a Resource Element (RE) and is uniquely identified by the index pair (k, i) in the slot. Where k is the index in the frequency domain, i is the index in the time domain, k is 0, ...,

-1, i has a value of 0, ...,

-1. ≪ / RTI >

개의 연속적인 SC-FDMA 심볼 및 주파수 영역에서

개의 연속적인 부반송파로 정의된다.

및

는 미리 결정된 값일 수 있다. 예를 들어,

및

는 아래 표 2와 같이 주어질 수 있다. 따라서 상향링크에서 하나의 PRB는

개의 자원 요소로 이루어질 수 있다. 또한, 하나의 PRB는 시간 영역 에서 하나의 슬롯 그리고 주파수 영역에서는 180kHz에 대응한다. 주파수 영역에서의 PRB 넘버 n_PRB 와 슬롯 내의 자원 요소 인덱스 (k,l)는

의 관계를 만족할 수 있다.A physical resource block (PRB)

RTI ID = 0.0 > SC-FDMA < / RTI >

Lt; / RTI > subcarriers.

And

May be a predetermined value. E.g,

And

Can be given as shown in Table 2 below. Therefore, in the uplink, one PRB

Can be composed of four resource elements. Also, one PRB corresponds to one slot in the time domain and 180 kHz in the frequency domain. The PRB number n _PRB in the frequency domain and the resource element index (k, l) in the slot are

Can be satisfied.

Configuration

Normal cyclic prefix 12 7 Extended cyclic prefix 12 6

Embodiments in which a channel element is mapped to an uplink resource (e.g., a physical uplink shared channel (PUSCH)) allocated by the UE based on the resource structure used in the LTE system will be described.

The MS may be allocated uplink resources (e.g., physical uplink shared channel (PUSCH)) from the base station for transmission of analog CSI feedback information. At this time, the basic unit of the PUSCH to be allocated may be one resource block. In the present invention, a mobile station can periodically receive a PUSCH from a base station. This can reduce the overhead rather than the event-triggered and aperiodic allocation.

A terminal includes a wideband including a plurality of subbands, each subband, the best M subbands, The components of the corresponding channel matrix or covariance matrix R may be mapped to the PUSCH and transmitted for any one or more of the average best M subbands. At this time, in order for the UE to transmit through the PUSCH, it is necessary to define the mapping pattern in advance. These resource mappings can be mapped consecutively on the time axis first, or consecutively on the frequency axis first.

The manner in which the terminal maps to the PUSCH can be divided into several patterns.

The first mapping pattern will be described with reference to FIGS. 3 and 4 attached hereto. The terminal can continuously map elements of a plurality of channel matrices H or matrix R to be transmitted on a time axis or a frequency axis. This mapping method is advantageous in that a larger amount of CSI feedback information can be sent while minimizing the overhead of uplink resources for transmission of CSI feedback information. However, since the elements of the channel matrix H or the covariance matrix R are composed of various values, there is a problem that the peak to average power ratio (PAPR) increases.

3 and 4 are diagrams illustrating an example of a method of mapping analog CSI feedback information according to the present invention.

Referring to FIG. 3, a terminal may continuously map elements of a plurality of channel matrices H or a covariance matrix R to be transmitted on a frequency axis. At this time, the channel matrix H or the elements of the covariance matrix R are added to the remaining symbols except for the middle symbols (fourth and eleventh symbols) (symbols of the hatched area) of each slot including the reference symbols (RS: Reference Symbol) Can be mapped. For example, in the symbol i = 0, the elements of the channel matrix H or the covariance matrix R are successively mapped on the frequency axis, and the symbols of i = 1 can be continuously mapped on the frequency axis again. At this time, the mapping may not be performed for the symbols i = 4, 11 including the reference symbol.

Referring to FIG. 4, the UE can continuously map the elements of the channel matrix H or the covariance matrix R on the frequency axis except for a specific subcarrier (k = 1, k = 12). As in FIG. 4, the mapping may not be performed for the symbols i = 4, 11 including the reference symbol.

As a second mapping pattern, when the number of components to be transmitted for one channel matrix H or covariance matrix R is equal to or less than the number of subcarriers or symbols (for example, 12) constituting one resource block, One channel matrix H or a covariance matrix R can be mapped for each symbol (in this case, mapping on the frequency axis first) or for each subcarrier (in this case, mapping on the time axis first). After mapping each element, the terminal can arbitrarily insert a garbage value that nulls the remaining symbols of each symbol or each subcarrier, or lowers the PAPR of the corresponding symbol or subcarrier. If there are two transmit antennas of the base station, one or more channel matrix H or covariance matrix R may be mapped for each symbol or each subcarrier.

A third mapping pattern according to the present invention will be described with reference to FIGS. 5 and 6 attached hereto.

5 and 6 are diagrams illustrating an example of a method of mapping analog CSI feedback information according to the present invention.

As a third mapping pattern, the UE may map each channel matrix H or an element of the covariance matrix R to an uplink resource (e.g., PUSCH) in a specific pattern, and map the remaining part or nullify the corresponding symbol or subcarrier A garbage value capable of lowering the PAPR can be arbitrarily inserted. As shown in FIG. 5, according to this specific mapping pattern, when the terminal preferentially maps on the frequency axis, it can map matrix elements to odd subcarriers. Then, the UE can insert a garbage value capable of nulling the even subcarrier or lowering the PAPR. Alternatively, as shown in FIG. 6, the terminal may map matrix elements to even-numbered subcarriers. Then, the UE can insert a garbage value capable of nulling the odd subcarrier or lowering the PAPR.

On the other hand, in order to increase the reception ratio of the analog CSI feedback information in the base station, matrix elements may be mapped to a specific area having a good reception ratio, the mapping may be performed, the remaining part may be nullified, or a garbage value may be inserted. Alternatively, for a relay backhaul link, a matrix element may be mapped to a portion excluding a first symbol and a last symbol of one resource block, and the remaining portion may be nullified or a garbage value may be inserted.

In addition to this, the UE may consider any method capable of arbitrarily inserting a garbage value, which maps a matrix element to a PUSCH region, nulls the remaining portion of the mapping, or lowers the PAPR of the corresponding symbol or subcarrier.

It is assumed that the MS has been allocated uplink resources (for example, one resource block of the PUSCH) from the base station to transmit the analog CSI feedback information. Then, a MIMO system having four transmission antennas of the base station is assumed. In order to satisfy the single carrier property, the remaining symbols excluding the intermediate symbols (for example, the 4th and 11th symbols) of each slot including the reference symbol (RS) among the 14 symbols It is possible to map the analog CSI. That is, the UE can map the elements of each channel matrix H or the covariance matrix R to the PUSCH region. Here, it is assumed that a covariance matrix R is transmitted.

값을 가지게 된다. 이를 해결하기 위해 전체 심볼의 전력합으로 정규화할 수 있다. 송신 안테나가 4개인 MIMO 시스템에서 공분산 행렬은 다음 수학식 3과 같이 4×4 행렬로 표현될 수 있다. The covariance matrix element mapping to each resource element can be normalized through the total power sum of the remaining symbols excluding the symbol including the reference symbol. Each symbol can have a different power level depending on the covariance matrix element. Therefore, when normalization is performed with each symbol power,

. In order to solve this problem, the power sum of all symbols can be normalized. In a MIMO system with four transmit antennas, a covariance matrix can be expressed by a 4x4 matrix as shown in Equation (3).

The matrix shown in Equation (3) is symmetric with respect to a diagonal term. Accordingly, even if the UE transmits only the diagonal elements of the covariance matrix and the upper triangle, the BS can obtain sufficient information about the channel. That is, the UE may feed back 10 elements of a triangular portion (a hatched region in Equation 3) in a 4x4 matrix for each channel.

The mapping method of the covariance matrix elements may map one channel to each symbol as in the method of the first mapping pattern that continuously maps on the frequency axis shown in FIG. 3 and FIG. For example, in the case of a MIMO system having four transmit antennas, as shown in FIG. 4, 10 channel elements may be mapped to one symbol, and the remainder may be nulled or a garbage value may be inserted to lower the PAPR. Alternatively, as in the third mapping pattern, the UE may map each channel matrix H or the elements of the covariance matrix R to the PUSCH in a specific pattern, and map the remaining part to null or lower the PAPR of the corresponding symbol or subcarrier You can insert arbitrary garbage values.

As shown in FIG. 5, when the specific pattern is mapped to the frequency axis, a matrix element is mapped to odd subcarriers, and a garbage value capable of nulling or remaining PAPR lower can be inserted in the remaining subcarriers have. Alternatively, as shown in FIG. 7, a matrix element may be mapped to an even-numbered subcarrier, and a garbage value capable of nulling an odd-numbered subcarrier or lowering a PAPR may be inserted. Alternatively, as shown in FIG. 6, one covariance matrix that can be represented by 10 elements may be divided into two symbols by five elements and mapped to even-numbered subcarriers, and the remaining part may be nullified or inserted by inserting a garbage value. Alternatively, in order to increase the reception ratio of the analog CSI feedback information at the base station, matrix elements may be mapped to a specific area having a good reception ratio, the remaining part may be nulled, or a garbage value may be inserted.

FIGS. 7 to 11 are diagrams illustrating an example of a method of mapping analog CSI feedback information according to the present invention. FIGS. 12 to 16 illustrate mapping of analog CSI feedback information according to the present invention on a time axis Fig.

If it is assumed that the middle part of the subcarrier in one resource block has a good reception ratio, the matrix element value may be mapped as shown in FIG. 4 or FIG. Also, as shown in FIGS. 12 to 16, matrix element values may be mapped prioritized on the time axis.

Suppose that a terminal is allocated an uplink resource (e.g., one resource block of a PUSCH) from a base station to transmit analog CSI feedback information. And a MIMO system with eight transmit antennas of the base station. In a MIMO system with eight transmit antennas, the covariance matrix can be expressed by Equation (4).

Equation (4) is expressed by an 8x8 matrix and is symmetric with respect to a diagonal term. Therefore, even if the terminal transmits only the diagonal elements of the covariance matrix and the triangular part (hatched areas), the base station can obtain sufficient information about the channel. That is, the UE may feed back 36 elements in an 8x8 matrix for each channel.

The mapping method of the covariance matrix elements includes a first mapping pattern that continuously maps on the frequency axis as shown in FIG. When elements constituting a matrix exceed the number of subcarriers or symbols constituting one resource block, matrix elements may be mapped to a plurality of symbols or subcarriers.

For example, in the case of a MIMO system having 8 transmit antennas, as shown in FIG. 8, a terminal maps 36 channel elements to 4 symbols each by 9 elements, maps the remaining symbols to nulls, or PAPR You can insert a garbage value to lower it. Alternatively, when mapping is performed on the frequency axis in advance, as shown in FIG. 5, a matrix element may be mapped to an odd subcarrier, and a garbage value capable of nulling an even subcarrier or lowering PAPR may be inserted. Alternatively, as shown in FIG. 6, matrix elements may be mapped to even-numbered subcarriers. The odd-numbered subcarriers may be inserted with a garbage value capable of nulling or lowering the PAPR. It is also possible to perform mapping on the time axis with preference as shown in Figs. 12 and 17.

As another embodiment according to the present invention, suppose that a terminal is allocated an uplink resource (e.g., PUSCH 1 resource block) for analog CSI feedback. And a MIMO system with two transmit antennas of the base station. In a MIMO system with two transmit antennas, the covariance matrix can be expressed by Equation (5).

Equation (5) can be expressed by a 2x2 matrix. The matrix of Equation (5) is symmetric with respect to the diagonal elements. Therefore, even if only the diagonal elements of the covariance matrix and the triangular part (hatched area) are transmitted, the base station can obtain sufficient information about the channel. That is, the UE may feed back three elements to the base station in a 2x2 matrix for each channel.

17 to 20 are diagrams showing an example of mapping CSI information on a frequency axis and transmitting the CSI information.

The mapping method of the covariance matrix elements may map one channel to each symbol as in the method of the first mapping pattern that continuously maps on the frequency axis shown in FIG. 3 and FIG. For example, in the case of a MIMO system with two transmit antennas, as shown in FIGS. 9 and 10, three channel elements are mapped to one symbol, and the remaining symbols are nulled or inserted to insert a garbage value for lowering the PAPR can do. Alternatively, as in the third mapping pattern, the UE may map each channel matrix H or the elements of the covariance matrix R to the PUSCH in a specific pattern, and map the remaining part to null or lower the PAPR of the corresponding symbol or subcarrier It is possible to insert arbitrary garbage values.

As shown in FIG. 5, when the specific pattern is mapped to the frequency axis, a matrix element may be mapped to an odd subcarrier, and a garbage value that nulls an even subcarrier or lower a PAPR may be inserted. Alternatively, as shown in FIG. 6, a matrix element may be mapped to an even-numbered subcarrier, and a garbage value capable of nulling an odd-numbered subcarrier or lowering a PAPR may be inserted. Alternatively, as shown in FIG. 11, three covariance matrices that can be represented by three elements may be simultaneously sent to one symbol, and the remaining part may be nullified or a garbage value may be inserted and transmitted. Also, as shown in FIG. 12 and FIG. 18 to FIG.

In another embodiment according to the present invention, the terminal transmits the analog CSI feedback information using the PUSCH allocated thereto. In addition to this method, the terminal may also transmit using a sounding reference signal (SRS) symbol.

21 is a diagram illustrating an example of a frame structure including CSI feedback information and a CRS symbol according to the present invention.

As shown in FIG. 21, the CSI feedback transmission using the CRS symbol can be transmitted in the last symbol of the first slot if the first slot can be allocated in the subframe including the CRS symbol. Alternatively, in addition to the method of additionally allocating the last symbol of the first slot, CSI feedback information may be transmitted instead of the CRS transmission in an arbitrary subframe during the existing CRS transmission period. In addition, the CSI feedback information transmission period may be shorter than the existing CRS transmission period, and the CSI feedback information may be transmitted to the CRS symbol of the subframe having the further allocated period. For example, when a UE having a CRS transmission period of 2 ms transmits CSI feedback information, a CRS transmission period of 1 ms is allocated, and CRS symbols and CSI feedback information are alternately transmitted every 1 ms. Can be performed.

The resource mapping method for CSI feedback transmission described above maps the analog CSI to the remaining symbols except for the middle symbols (for example, the fourth and eleventh symbols) of each slot including the reference symbols among the 14 symbols . However, without sending reference symbols, all of the resources can be used for CSI feedback transmission. The problem of channel estimation caused by not sending reference symbols is that the respective elements of channel matrix H or covariance matrix R are separated into real and imaginary values and the sign of the values (e.g., +, -, ) By sending the same value or another value repeatedly. The mapping rules can be applied to the mapping rules described above.

Assume a MIMO system with two transmit antennas at the base station. In a MIMO system with two transmit antennas, the covariance matrix can be expressed by Equation (6).

Equation (6) is expressed by a 2x2 matrix. This matrix is symmetric with respect to diagonal elements. Therefore, even if only the diagonal element of the covariance matrix and the upper triangular part (hatched area) are transmitted, the base station can obtain sufficient information about the channel. That is, the UE may feed back three elements (a, b, c) in a 2x2 matrix for each channel. The diagonal elements are composed only of real values and require at least two Resource Elements to transmit the real values. In order to transmit the real and imaginary values of the off-diagonal elements, the minimum Four resource elements are required. Therefore, 8 resource elements are required to transmit a 2x2 matrix without a reference symbol.

22 is a diagram illustrating an example of a method of mapping a covariance matrix element value.

를 전송하기 위해 4개의 자원요소에 매핑되는 값은 도 22와 같이

가 될 수 있다.For example, the component of (1,2)

The values mapped to the four resource elements for transmission are shown in FIG. 22

.

The above-described CSI feedback mapping method of the present invention has been described based on the covariance matrix R in the embodiments (2Tx, 4Tx, 8Tx). However, the present invention can also be applied to various channel matrices H according to various combinations of transmit antennas and receive antennas.

23 is a diagram for explaining a signal processing procedure for a UE to transmit an uplink signal.

In order to transmit the uplink signal, the scrambling module 2310 of the terminal may scramble the transmission signal using the user equipment specific scrambling signal. The scrambled signal is input to the modulation mapper 2320, and is modulated into a complex symbol according to the type and / or channel state of the transmission signal by BPSK, QPSK, or 16 QAM. The modulated complex symbols are then spread by the transform precoder 2330 corresponding to the DFT spreading and then input to the resource element mapper 2340 and the resource element mapper 2340 transforms the complex symbols to be used for the actual transmission Time-frequency resource element. The signal thus processed can be transmitted to the base station via the antenna via the SC-FDMA signal generator 2350. [

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The foregoing description of the preferred embodiments of the invention disclosed herein has been presented to enable any person skilled in the art to make and use the present invention. Although the present invention has been fully described by way of example with reference to the accompanying drawings, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the invention. For example, those skilled in the art can utilize each of the configurations described in the above-described embodiments in a manner of mutually combining them.

Accordingly, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

1 is a view for explaining physical channels used in a 3GPP (Third Generation Partnership Project) LTE (Long Term Evolution) system as an example of a mobile communication system and a general signal transmission method using them,

2 is a diagram illustrating an uplink time-frequency resource grid structure used in a 3rd Generation Partnership Project (3GPP) LTE (Long Term Evolution) system, which is an example of a mobile communication system;

3 and 4 are diagrams illustrating an example of a method of mapping analog CSI feedback information according to the present invention.

5 and 6 illustrate an example of a method of mapping analog CSI feedback information according to the present invention.

FIGS. 7 to 11 illustrate an example of a method of mapping analog CSI feedback information according to the present invention.

FIGS. 12 to 16 are diagrams showing an example in which the analog CSI feedback information according to the present invention is mapped in priority order on the time axis; FIG.

17 to 20 are diagrams showing an example of mapping CSI information prior to mapping on the frequency axis,

21 is a diagram illustrating an example of a frame structure including CSI feedback information and a CRS symbol according to the present invention;

22 is a diagram illustrating an example of a method of mapping a covariance matrix element value,

23 is a diagram for explaining a signal processing procedure for a UE to transmit an uplink signal.

Claims (10)

A method for a mobile station to transmit channel state information in a wireless communication system, Receiving uplink resources for transmitting channel state information from a base station; Each element corresponding to an upper triangle matrix in a spatial channel matrix or a spatial channel covariance matrix is mapped to the allocated resource on a symbol or a subcarrier basis and nulls or a garbage value is mapped on the mapped remaining region Mapping; And And transmitting the channel state information including the mapped spatial channel matrix or the spatial channel covariance matrix to the BS through the allocated resources. The method according to claim 1, Further comprising normalizing the channel state information using a total power value of the mapped total symbols or a power value of a specific symbol having a highest power value. 3. The method according to claim 1 or 2, Wherein the channel state information further includes noise plus interference variance information for the entire bandwidth. The method according to claim 1, The spatial channel matrix or the spatial channel covariance matrix information may include at least one of a subband, a wide band including a plurality of subbands, a predetermined number of subbands having the best channel state, or a plurality of subbands having the best average channel state Channel state information. The method according to claim 1, Wherein each symbol is a symbol other than a symbol including a reference symbol. The method according to claim 1, Wherein each element corresponding to the upper triangle matrix is mapped to an odd-numbered symbol or an odd-numbered subcarrier. The method according to claim 1, Wherein each element corresponding to the upper triangle matrix is mapped to an even-numbered symbol or an even-numbered subcarrier. The method according to claim 1, Wherein the uplink resource is a Physical Uplink Shared Channel (PUSCH). 9. The method of claim 8, Wherein the uplink resource further comprises a sounding reference signal symbol region, Wherein the sounding reference signal symbol is a last symbol of a first slot temporally preceding one subframe. The method according to claim 1, And separating a real value and an imaginary value of each element corresponding to an upper triangle matrix in the spatial channel matrix or the spatial channel covariance matrix and mapping the separated values to the allocated resources.

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