KR101525619B1 - Method of transmitting data in multiple antenna system - Google Patents

Abstract

A method for transmitting data in a multi-antenna system is provided. The method includes a CDD indicator indicating whether precoding supports CDD (Cyclic Delay Diversity) using path delays between antennas of multiple antennas and a Precoding Matrix Indicator (PMI) indicating a precoding matrix Transmitting downlink scheduling information to the MS through a physical downlink control channel (PDCCH), and transmitting downlink data, which is precoded according to the precoding matrix indicated by the PMI, and the CDD indicator, And transmitting the downlink shared channel (PDSCH) to the MS through a Physical Downlink Shared CHannel (PDSCH). It is possible to provide a multi-antenna system service quickly responding to a rapidly changing channel environment by transmitting a CDD indicator to a terminal immediately at a lower layer level.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a multi-

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to wireless communication, and more particularly, to a method of transmitting data in a multi-antenna system.

Recently, demands for wireless communication services are rapidly increasing due to the generalization of information communication services, the emergence of various multimedia services, and the emergence of high quality services. Various multi-antenna systems using multiple antennas for transmitters and receivers have been proposed to provide high-speed, high-quality data services in wireless communications. A multi-antenna system is also referred to as a Multiple Input Multiple Output (MIMO) system. Various multi-antenna transmission and reception techniques applied to a multi-antenna system are being studied.

Cyclic Delay Diversity (CDD) and precoding are as follows. CDD is to obtain a diversity gain using the delay of the transmission path between each transmission antenna. For example, data transmitted to the first transmission antenna is directly transmitted to the receiver, but data transmitted to the second transmission antenna is transmitted after being cyclically delayed as compared with the first transmission antenna.

Precoding includes precoding for transmit diversity and precoding for spatial multiplexing. Precoding for transmit diversity is a precoding technique used to obtain a signal-to-noise ratio (SNR) gain by transmitting the same data through several transmit antennas and to increase data transmission reliability. Precoding for spatial multiplexing is a precoding technique used to increase the data rate by transmitting different data through several transmit antennas. Precoding for spatial multiplexing includes precoding without supporting CDD and CDD supporting precoding supporting CDD.

Hereinafter, the downlink means communication from the base station to the terminal, and the uplink means communication from the terminal to the base station. In the downlink, the transmitter may be part of the base station and the receiver may be part of the terminal. On the uplink, the transmitter may be part of the terminal and the receiver may be part of the base station.

In order for the CDD and precoding based multi-antenna system to operate efficiently, the BS and the UE can exchange various control information. First, if the UE transmits feedback information to the BS, the BS performs scheduling on the data channel based on the feedback information. The base station transmits the scheduling information, which is a result of the scheduling, to the mobile station, and the mobile station receives the downlink data or transmits the uplink data according to the scheduling information.

The feedback information includes a scheduling request for requesting a radio resource allocation, a channel quality information (CQI), a band selection, an ACK / NACK (acknowledgment) for a downlink data transmission, / not-acknowledgment signal, Rank Indicator (RI), and Precoding Matrix Indicator (PMI). Of these, feedback information required for the multi-antenna transmission scheme includes CQI, RI, and PMI. The feedback information required in the multi-antenna system may be referred to as MIMO information separately.

As described above, precoding for spatial multiplexing is divided into precoding that does not support CDD and precoding that supports CDD. Therefore, when the multi-antenna system is in the spatial multiplexing mode, the base station needs to inform the UE of the CDD information as to whether or not the precoding supports CDD according to the channel change. Also, when the multi-antenna system is not in the spatial multiplexing mode such as the transmission diversity mode, it is necessary to inform the terminal of the CDD information even when switching to the spatial multiplexing mode.

If a delay occurs in transmitting the feedback information and CDD information, the data transmission based on these control information will also be delayed, which may lead to a decrease in the overall throughput of the multi-antenna system. Therefore, there is a need for a data transmission method capable of maintaining the performance of a multi-antenna system even when feedback information and CDD information are transmitted.

An object of the present invention is to provide a method of transmitting data that reduces time delay when transmitting information about feedback information and CDD indicator in a multi-antenna system.

According to an aspect of the present invention, there is provided a method of transmitting data in a multi-antenna system. The method includes a CDD indicator indicating whether precoding supports CDD (Cyclic Delay Diversity) using path delays between antennas of multiple antennas and a Precoding Matrix Indicator (PMI) indicating a precoding matrix Transmitting downlink scheduling information to the MS through a physical downlink control channel (PDCCH), and transmitting downlink data, which is precoded according to the precoding matrix indicated by the PMI, and the CDD indicator, And transmitting the downlink shared channel (PDSCH) to the MS through a Physical Downlink Shared CHannel (PDSCH).

According to another aspect of the present invention, there is provided a method of receiving data in a multi-antenna system. The method includes transmitting an RI to a base station indicating a rank that is a number of layers related to a data stream that can be simultaneously transmitted in parallel via multiple antennas, determining whether precoding supports CDD using path delays between the antennas of the multiple antennas Receiving a downlink scheduling information including a CDD indicator and a PMI pointing to a precoding matrix from the base station via a PDCCH, and a precoding matrix pointed by the PMI, And receiving precoded downlink data from the base station via a PDSCH.

According to yet another aspect of the present invention, a method of operating a multi-antenna system is provided. The method includes transmitting an RRC setup request message, receiving an RRC setup complete message, which is a response to the RRC setup request message, and performing a first downlink transmission according to a multi-antenna transmission / reception scheme of a default mode Receiving rank information for deriving a spatial multiplexing mode as feedback information for the first downlink transmission, transmitting a CDD indicator indicating whether precoding for spatial multiplexing supports CDD, and And performing a second downlink transmission according to the spatial multiplexing mode.

It is possible to provide a multi-antenna system service quickly responding to a rapidly changing channel environment by transmitting a CDD indicator to a terminal immediately at a lower layer level.

1 is a block diagram illustrating a wireless communication system. Wireless communication systems are widely deployed to provide various communication services such as voice, packet data, and the like.

Referring to FIG. 1, a wireless communication system includes a user equipment (UE) 10 and a base station (BS) 20. The terminal 10 may be fixed or mobile and may be referred to by other terms such as a Mobile Station (MS), a User Terminal (UT), a Subscriber Station (SS), a wireless device, The base station 20 generally refers to a fixed station that communicates with the terminal 10 and may be referred to in other terms such as a Node-B, a Base Transceiver System (BTS), an Access Point Can be called. One base station 20 may have more than one cell.

Hereinafter, downlink (DL) means communication from the base station 20 to the terminal 10, and uplink (UL) means communication from the terminal 10 to the base station 20. In the downlink, the transmitter may be part of the base station 20 and the receiver may be part of the terminal 10. In the uplink, the transmitter may be part of the terminal 10 and the receiver may be part of the base station 20.

The wireless communication system may be an Orthogonal Frequency Division Multiplexing (OFDM) / Orthogonal Frequency Division Multiple Access (OFDMA) based system. OFDM uses multiple orthogonal subcarriers. OFDM utilizes the orthogonality property between IFFT (inverse fast Fourier transform) and FFT (fast Fourier transform). The transmitter performs IFFT on the data and transmits it. The receiver performs an FFT on the received signal to recover the original data. The transmitter uses an IFFT to combine multiple subcarriers, and the receiver uses a corresponding FFT to separate multiple subcarriers.

The wireless communication system may be a multiple antenna system. The multi-antenna system may be a multiple-input multiple-output (MIMO) system. Or multiple antenna systems may be implemented using a multiple input single-output (MISO) system or a single-input single-output (SISO) system or a single- ) System. A MIMO system uses multiple transmit antennas and multiple receive antennas. The MISO system uses multiple transmit antennas and one receive antenna. The SISO system uses one transmit antenna and one receive antenna. The SIMO system uses one transmit antenna and multiple receive antennas.

2 is a block diagram illustrating the structure of a transmitter having multiple antennas.

2, the transmitter 100 includes an encoder 110-1, ..., 110-K, modulators 120-1, ..., 120-K, a layer mapper 130, 140, subcarrier mappers 150-1, ..., 150-K and OFDM signal generators 160-1, ..., 160-K. Transmitter 100 includes Nt (Nt 1) transmit antennas 170-1, .., 170-Nt.

Encoders 110-1,..., 110-K encode input data according to a predetermined coding scheme to form coded data. The modulators 120-1,..., 120-K arrange the coded data into symbols representing positions on the signal constellation. The modulation scheme is not limited and may be m-Phase Shift Keying (m-PSK) or m-Quadrature Amplitude Modulation (m-QAM). For example, m-PSK may be BPSK, QPSK, or 8-PSK. The m-QAM may be 16-QAM, 64-QAM, or 256-QAM.

The layer mapper 130 defines a layer of input symbols such that the precoder 140 can distribute the antenna specific symbols to the paths of each antenna. The layer is defined as an information path that is input to the precoder 140. The information path before the precoder 140 may be referred to as a virtual antenna or a layer.

The precoder 140 processes the input symbols according to the MIMO scheme according to the multiple transmit antennas 170-1, .., and 170-Nt, and outputs antenna specific symbols. The precoder 140 may support Cyclic Delay Diversity (CDD) as codebook based precoding, especially when the multiple antenna system is in a spatial multiplexing mode. This will be described later. The precoder 140 distributes the antenna specific symbols to the sub-carrier mappers 150-1,..., 150-K in the path of the corresponding antenna. Each information path sent by one precoder 140 to one antenna through one subcarrier mapper is called a stream. This can be referred to as a physical antenna.

The subcarrier mappers 150-1,..., 150-K allocate antenna specific symbols to appropriate subcarriers and multiplex them according to users. The OFDM signal generators 160-1,..., 160-K modulate the antenna specific symbols using the OFDM scheme and output OFDM symbols. The OFDM signal generators 160-1, ..., and 160-K may perform Inverse Fast Fourier Transform (IFFT) on antenna-specific symbols, and a CP (cyclic prefix) . An OFDM symbol is transmitted via each transmit antenna 170-1, .., 170-Nt.

Hereinafter, a multi-antenna transmission / reception technique used for a multi-antenna system will be described. The scheme of multi-antenna transmission and reception schemes used for operation of a multi-antenna system may vary according to rank. For example, in Rank 1, Space-Time Coding (STC), Cyclic Delay Diversity (CDD), Frequency Switched Transmit Diversity (FSTD), and TSTD switched transmit diversity) may be used. Spatial Multiplexing (SM), Generalized Cyclic Delay Diversity (GCDD), Selective Virtual Antenna Permutation (S-VAP), or the like can be used in Rank 2 or higher.

SFBC is a technique that can efficiently obtain diversity gain and multi-user scheduling gain at the corresponding dimension by efficiently applying selectivity in the spatial domain and frequency domain. STBC is a technique for applying selectivity in space and time domain. FSTD is a technique for dividing signals transmitted by multiple antennas into frequencies, and TSTD is a technique for dividing signals transmitted by multiple antennas by time. Spatial multiplexing is a technique for increasing the transmission rate by transmitting different data for each antenna. GCDD is a technique that applies selectivity in time domain and frequency domain. The S-VAP is a technique using a single precoding matrix. The S-VAP uses MCC (Multi Codeword) S-VAP, which mixes multiple codewords between antennas in spatial diversity or spatial multiplexing, and Single Codeword -VAP.

CDD is a technique for obtaining a diversity gain using a path delay between transmission antennas. Regarding CDD, precoding for spatial multiplexing includes precoding that supports CDD and precoding that does not support CDD. Pre-coding that does not support CDD may be referred to as precoding without CDD, and pre-coding that supports CDD may be referred to as precoding for CDD.

Precoding that does not support CDD is defined by Equation (1) below.

Referring to Equation 1, and ^{x (i) = [x (} 0) (i), ..., x (υ-1) (i)] T is a vector (vector) input to the precoder, y ( ^{i) = [y (0)} (i), ..., y (P-1) (i)] T is a vector that is mapped to the resources for the respective transmission antennas, W (i) is of size P × υ Is a precoding matrix. Where υ is the number of layers (layer), i = 0,1, ..., M layer symb -1 is the number of each of the hierarchical modulation symbol (modulation symbol) per (layer) (M _symb ^layer is for each antenna Is equal to M ^antenna _symb , the number of modulation symbols) and y ^(P) (i) is the signal for the Pth transmit antenna. Therefore, if there is only one transmission antenna, y ^(P) (i) = x ⁽⁰⁾ (i). For spatial multiplexing, the value of W (i) may be selected from among the precoder elements in the codebook.

On the other hand, the precoding supporting CDD is defined by the following equation (2).

Referring to Equation (2), x (i), y (i) and W (i) are the same as in Equation (1). i = 0,1, ..., M ^antenna _symb -1 is the number of modulation symbols per antenna, and the matrix D (i) and the matrix U are of the size of υ × υ supporting circular delay diversity As a square matrix, it can be defined as shown in Table 1 according to the number of layers.

In this way, precoding for spatial multiplexing includes precoding that supports CDD and precoding that does not support CDD, which are different from each other. Therefore, the BS needs to inform the UE whether precoding supports CDD when in the spatial multiplexing mode.

3 is a flowchart illustrating a method of transmitting data in a multi-antenna system according to an exemplary embodiment of the present invention.

Referring to FIG. 3, the terminal transmits feedback information to the base station (S100). The feedback information may be at least one of Channel Quality Information (CQI), Rank Indicator (RI), and Precoding Matrix Indicator (PMI). Each of the feedback information will be described in detail below. The CQI is information indicating the state of the downlink channel to the base station in order to allocate the downlink resources. The CQI includes a Signal-to-Interference plus Noise Ratio (SINR), a Modulation and Coding Scheme (MCS) rate indicator, received signal strength indicator, and the like. RI is an indicator that indicates a rank, which is the number of parallel data streams that can be simultaneously transmitted by the base station through multiple antennas. The PMI is an indicator for indicating a specific precoding matrix in a set of precoding matrices used for precoding data.

The transmission method of the feedback information is as follows. The UE may periodically transmit the feedback information according to a preset period, or may request feedback information from the UE whenever the base station needs it. In the former case, the base station can inform the terminal of information on the CQI report period as a Radio Resource Control (RRC) message. The MS can transmit the feedback information to the BS through a Physical Uplink Control Channel (PUCCH). Alternatively, if the UE has received uplink scheduling information from the BS in advance and the time of transmitting the feedback information corresponds to the time of transmitting uplink data according to the uplink scheduling information, the UE transmits a physical uplink shared channel The uplink data and the feedback information may be transmitted to the base station through an uplink shared channel (PUSCH).

The base station transmits downlink scheduling information (DL scheduling information) according to the feedback information to the mobile station (S110). The base station performs scheduling on a Physical Downlink Shared CHannel (PDSCH) from feedback information required for the operation of the multi-antenna system, and transmits downlink scheduling information, which is a result of the scheduling, to the UE. The downlink scheduling information is transmitted through a physical downlink control channel (PDCCH) and is also referred to as a downlink grant. As described above, the multi-antenna transmission / reception scheme applied to the multi-antenna system may be different according to the rank, and the format of the downlink scheduling information may be changed according to the multi-antenna transmission / reception scheme.

The downlink scheduling information used for the purpose of spatial multiplexing among the multiple antenna transmission / reception scheme includes at least one of various fields in Table 2.

Field Bits Comments Resource allocation header One RB (Resource Block) allocation 25 The resource blocks of the UE shall transmit upon. TPC 2 Power control of PUCCH Number of layers 2 information path to precoder 1st MCS 5 Modulation and Coding for the 1st transport block Hybrid ARQ process number 3 the number of HARQ process 1st NDI One New data indicator for the 1st transport block 1st Redundancy version 2 HARQ redundancy version for the first transport block 2nd MCS 5 Modulation and Coding for the 2nd transport block HARQ swap flag One 2nd NDI One New data indicator for the 1st transport block 2nd Redundancy version 2 HARQ redundancy version for the first transport block Precoding information 4 information for precoding matrix Precoding confirmation One CDD indicator One indicates the type of cyclic delay diversity RNTI / CRC 16 Total 72

Referring to Table 2, the downlink scheduling information includes a resource allocation header, RB allocation information, TPC information, a number of layers, A first modulation and coding scheme (MCS), a HARQ process number, a first new data indicator (NDI), a first redundancy version, a second modulation and coding A second MCS, a HARQ swap flag, a second new data indicator (NDI), a second redundancy version, precoding information, precoding confirmation, , A CDD indicator, and a Radio Network Temporary Identifier (RNTI) / Cyclic Redundancy Check (CRC). The number of bits in each field and each field belonging to the downlink scheduling information is only an example, and a part of fields in Table 2 may be omitted, and the bit number of each field may be set differently from Table 2. [

The base station transmits downlink data (DL data) generated according to the field information included in the downlink scheduling information to the mobile station in step S120. The base station precodes the downlink data according to the precoding matrix indicated by the PMI, which is the precoding information, and the CDD indicator. The base station transmits the precoded downlink data to the terminal.

Hereinafter, the CDD indicator among the fields of Table 2 will be described in more detail. As described above, since precoding supporting CDD and precoding not supporting CDD are defined in different forms, the UE can not receive data successfully without knowing what precoding the downlink data is transmitted. Therefore, the BS needs to first inform the UE whether precoding supports CDD. An indicator indicating whether or not precoding supports CDD is referred to as a CDD indicator. The CDD indicator is control information necessary for a multi-antenna system in a spatial multiplexing mode, and is included in downlink scheduling information other than the RRC message, and is transmitted as a lower layer message.

If the CDD indicator is transmitted as an RRC message, the base station can not quickly respond to the high rank service requested by the terminal. For example, if the UE transmits rank 1 as feedback information, the base station can set the SFBC to a default mode as a multi-antenna transmission / reception scheme. At this time, if the channel environment is improved and the terminal feeds back rank 2 to the base station, the base station changes to the spatial multiplexing mode. In order for a base station to immediately transmit downlink data in a spatial multiplexing mode in response to a request from such a terminal, the base station must immediately inform the CDD. If the CDD indicator is transmitted as an RRC message, signaling must be performed up to the upper layer, so that it is relatively delayed so that it can not respond quickly to the request of the terminal. Therefore, the CDD indicator is transmitted as a message in the lower layer of the MAC layer or the physical layer, rather than being transmitted in the RRC message, so that the transmission yield of the system can be maintained.

The CDD indicator may be 1-bit information. For example, a CDD indicator of 1 indicates that precoding supports CDD, and a value of 0 indicates that precoding does not support CDD. The CDD indicator is included in the downlink scheduling information as shown in Table 2 and can be transmitted to the UE through the PDCCH.

4 is a flowchart illustrating a method of transmitting data in a multi-antenna system according to another example of the present invention. This is explained from the initial stage in which the RRC connection state is established between the BS and the MS.

Referring to FIG. 4, the BS transmits an RRC configuration request message to the MS (S200). The RRC setup request message may include at least one of a PUCCH resource allocation information, a CQI report period, and a PMI. In a multi-antenna system, CQI reporting is basically not implemented by selecting a wideband / selective band, but two modes must be transmitted at a constant period according to a multi-antenna transmission / reception scheme. In particular, when the multi-antenna system is in spatial multiplexing mode, the CQI report is transmitted on the PUSCH. The CQI reporting period transmitted through the PUSCH and the CQI reporting period transmitted via the PUCCH inform the UE of the RRC setting.

In response to the setup request message, the UE transmits an RRC configuration complete message to the BS in step S210.

At the time when the RRC setting is completed, since the base station has no information on the rank from the UE, the rank 1 is set as the default, the multi-antenna transmission / reception scheme according to rank 1 is set as the default mode, and the downlink scheduling information is transmitted via the PDCCH (S220). Here, the multi-antenna transmission / reception scheme of the default mode may be Space Frequency Block Coding (SFBC). The BS transmits the downlink data to the UE through the PDSCH according to the downlink scheduling information (S230).

The UE receiving the downlink scheduling information and the downlink data transmits an RI or a CQI to the base station in step S240. The UE transmits the CQI according to the CQI reporting period, and only the RI can be transmitted as the feedback information in the period in which the CQI is not transmitted. The feedback information is transmitted via the PUCCH. Here, steps S210 to S230 will be referred to as first downlink transmission. The first downlink transmission may be repeated until the terminal feeds back the RI indicating rank 2. [

When the downlink channel environment is suitable for rank 2, the terminal transmits RI indicating rank 2 to the base station as feedback information (S250). Upon receiving the RI indicating rank 2, the base station changes the multi-antenna transmission / reception scheme from the SFBC in the default mode to the spatial multiplexing (SM) mode. Accordingly, the BS first refers to the rank 2, and transmits downlink scheduling information and uplink scheduling information for which the format is set, to the UE through the PDCCH (S260). Then, in accordance with the downlink scheduling information, To the terminal (S270).

Herein, the downlink scheduling information includes a CDD indicator. Because the multi-antenna transmission and reception scheme has been changed to the spatial multiplexing mode, the base station must inform whether or not precoding for spatial multiplexing supports CDD. However, since the base station has not yet received PMI, which is the feedback information from the UE, it can not decide whether to apply precoding supporting CDD or precoding not supporting CDD. Therefore, the base station can set the CDD indicator to any one of the default values and notify the terminal. The default value of the CDD indicator may be set to indicate that precoding may support CDD and not CDD. The PMI used in the second downlink transmission may be the same PMI as the PMI transmitted by the base station when the RRC is set.

Meanwhile, since the base station transmits the uplink scheduling information to the UE in accordance with the CQI reporting period in order to receive the feedback information through the PUSCH, the UE transmits RI, CQI and PMI to the base station according to the uplink scheduling information (S280 ). That is, in the spatial multiplexing mode, if the time to transmit the uplink data matches the time to transmit the feedback information, the feedback information is transmitted together with the uplink data through the PUSCH. The uplink scheduling information may be referred to as an uplink grant. The steps S260 to S280 may be referred to as a second downlink transmission.

If the UE changes its channel environment after the second downlink transmission and transmits another PMI to the BS, the BS can transmit the changed CDD indicator to the UE again.

As described above, the CDD indicator is immediately transmitted to the MS at the physical layer or MAC layer level, thereby providing a multi-antenna system service that responds rapidly to a rapidly changing channel environment.

All of the functions described above may be performed by a processor such as a microprocessor, a controller, a microcontroller, an application specific integrated circuit (ASIC), etc. according to software or program code or the like coded to perform the function. The design, development and implementation of the above code will be apparent to those skilled in the art based on the description of the present invention.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those skilled in the art that various changes and modifications may be made therein without departing from the spirit and scope of the invention. You will understand. Therefore, it is intended that the present invention covers all embodiments falling within the scope of the following claims, rather than being limited to the above-described embodiments.

1 is a block diagram illustrating a wireless communication system.

2 is a block diagram illustrating the structure of a transmitter having multiple antennas.

3 is a flowchart illustrating a method of transmitting data in a multi-antenna system according to an exemplary embodiment of the present invention.

4 is a flowchart illustrating a method of transmitting data in a multi-antenna system according to another example of the present invention.

Claims (16)

A CDD indicator indicating whether precoding supports CDD (Cyclic Delay Diversity) using path delays between antennas of multiple antennas, a Precoding Matrix Indicator (PMI) indicating a precoding matrix, Transmitting downlink scheduling information including a Rank Indicator (RI) indicating a number of layers to a mobile station through a physical downlink control channel (PDCCH); Transmitting a precoding matrix for the PMI indicated by the PMI and a first downlink data precoded according to the CDD indicator to the MS through a physical downlink shared channel (PDSCH); And Determining whether to apply CDD to a precoding matrix for second downlink data based on the PMI when a PMI determined based on the first downlink data is received from the UE, Wherein the downlink scheduling information is set in a format corresponding to a spatial multiplexing mode, and the precoding is precoding for spatial multiplexing. The method according to claim 1, Wherein the precoding is defined by the following equation.

Here, W (i) is a = size of the precoding matrix of P × υ (precoding matrix), a matrix D (i) and matrix U is a square matrix of size υ × υ supporting CDD, x (i) [x ( ⁰⁾ (i), ..., x ^(v-1) (i)] ^T is a vector input to the precoding, y (i) = [y ⁽⁰⁾ ., y ^(P-1) (i)] ^T is a vector mapped to a resource for each of the multiple antennas. Where υ is the number of layers (layer), i = 0,1, ..., M layer symb -1 is the number of each of the hierarchical modulation symbol (modulation symbol) per (layer) (M _symb ^layer is the multi-antenna Is equal to M ^antenna _symb , which is the number of modulation symbols for each ^antenna , and y ^(P) (i) is the signal for the Pth antenna. 3. The method of claim 2, Wherein the number of layers is two or more. 3. The method of claim 2, Wherein the matrix D (i) and the matrix U are determined according to the following table.

In the base station, Memory; And And a processor coupled to the memory, wherein the processor A CDD indicator indicating whether precoding supports CDD (Cyclic Delay Diversity) using path delays between antennas of multiple antennas, a Precoding Matrix Indicator (PMI) indicating a precoding matrix, And transmits downlink scheduling information including a Rank Indicator (RI) indicating the number of layers to a UE through a Physical Downlink Control Channel (PDCCH)  Transmits a precoding matrix for the PMI and precoding according to the CDD indicator to the MS through a Physical Downlink Shared CHannel (PDSCH) When the PMI determined based on the first downlink data is received from the MS, determines whether to apply CDD to the precoding matrix for the second downlink data based on the PMI, Wherein the downlink scheduling information is set in a format corresponding to a spatial multiplexing mode, and the precoding is precoding for spatial multiplexing. delete delete delete delete delete delete delete delete delete delete delete

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