TECHNICAL FIELD

The present disclosure relates to a wireless communication system, and more particularly, to a method and an apparatus for transmitting and receiving channel state information in a wireless communication system supporting a multi-antenna system (in particular, 2 dimensional active antenna system (2D AAS)).

BACKGROUND ART

Mobile communication systems have been developed to provide voice services, while guaranteeing user activity. Service coverage of mobile communication systems, however, has extended even to data services, as well as voice services, and currently, an explosive increase in traffic has resulted in shortage of resource and user demand for a high speed services, requiring advanced mobile communication systems.

The requirements of the next-generation mobile communication system may include supporting huge data traffic, a remarkable increase in the transfer rate of each user, the accommodation of a significantly increased number of connection devices, very low end-to-end latency, and high energy efficiency. To this end, various techniques, such as small cell enhancement, dual connectivity, massive Multiple Input Multiple Output (MIMO), in-band full duplex, non-orthogonal multiple access (NOMA), supporting super-wide band, and device networking, have been researched.

DISCLOSURE

Technical Problem

An object of the present disclosure is to propose a method for transmitting and receiving channel state information in a wireless communication system supporting a multi-antenna system (e.g., a 2D AAS system or a 3 dimensional multi-input multi-output (3D-MIMO) system with a massive antenna port).

An object of the present disclosure is to propose a method for transmitting and receiving channel state information and a codebook designing method in a wireless communication system supporting a linear combining codebook for combining beams in units of subbands.

The technical objects of the present disclosure are not limited to the aforementioned technical objects, and other technical objects, which are not mentioned above, will be apparently appreciated by a person having ordinary skill in the art from the following description.

Technical Solution

According to an aspect of the present disclosure, a method for transmitting, by a user equipment (UE), Channel State Information (CSI) in a wireless communication system may include: receiving, from a base station, a channel state information reference signal (CSI-RS) through multiple antenna ports; and reporting, to the base station, CSI, in which the CSI may include selection information indicating a plurality of codewords used for generating a precoding matrix in a codebook for reporting the CSI, and a power coefficient, a phase offset, and a phase shift value applied to each of the plurality of codewords in terms of a configured bandwidth, and the precoding matrix may be generated in units of subbands within the configured bandwidth based on a linear combination of the power coefficient, the phase offset, and the phase change value.

According to another aspect of the present disclosure, a user equipment (UE) for transmitting V (CSI) in a wireless communication system may include: a radio frequency (RF) unit transmitting and receiving a radio signal; and a processor controlling the RF unit, in which the processor may be configured to receive, from a base station, a Channel State Information Reference Signal (CSI-RS) through multiple antenna ports, and report, to the base station, CSI, the CSI may include selection information indicating a plurality of codewords used for generating a precoding matrix in a codebook for reporting the CSI, and a power coefficient, a phase offset, and a phase shift value applied to each of the plurality of codewords in terms of a configured bandwidth, and the precoding matrix may be generated in units of subbands within the configured bandwidth based on a linear combination of the power coefficient, the phase offset, and the phase change value.

Preferably, the phase change value may be derived from a Fast Fourier Transform (FFT) size in the configured band, an oversampling value, a speed at which a phase of a beam formed by each of the plurality of codewords is changed.

Preferably, the power coefficient, the phase offset, and the phase change value may be derived in units of the subbands with respect to each of the plurality of codewords by projecting the plurality of codewords to a channel matrix in units of the subbands.

Preferably, a frequency domain sample for each of the plurality of codewords may be calculated by projecting the plurality of codewords to the channel matrix in units of the subbands, and the phase change value may be derived from one or more time domain samples for each of the plurality of codewords acquired by applying Inverse Fast Fourier Transform (IFFT) to the frequency domain sample and the Fast Fourier Transform (FFT) size in the configured band.

Preferably, as the one or more time domain samples, a time domain sample having a strongest value or a maximum delay value may be used.

Preferably, as the one or more time domain samples, one or more consecutive time domain samples having the time domain sample having the strongest value or the maximum delay value may be used.

Preferably, the number of time domain samples used for deriving the phase change value may be determined based on a delay spread of a channel.

Preferably, as the one or more time domain samples, K time domain samples having a strong power value and a time domain sample having the strongest value or the maximum delay value among the remaining time domain samples except for the K time domain samples are used.

Preferably, in the case of rank 2, the linear combination may be independently applied for each precoding matrix for each layer.

Preferably, after the precoding matrix is generated, an orthogonal process may be applied to the precoding matrix for each layer in order to maintain orthogonality for each layer.

Preferably, Channel Quality Information (CQI) may be calculated based on the precoding matrix to which the orthogonal process is applied.

Preferably, in the case of rank 2, a first precoding matrix for any one layer may be generated by using the linear combination and a second precoding matrix for the remaining layer is generated by applying an orthogonal code to the first precoding matrix.

Preferably, quantization may be performed or higher granularity quantization is performed for reporting the power coefficient, the phase offset, and/or the phase change value only for a beam which exceeds a specific power threshold among the beams formed by the plurality of codewords.

Preferably, when the configured bandwidth is divided into a plurality of subband groups, the precoding matrix is independently generated by using the plurality of codewords for each subband group.

Preferably, the plurality of codewords may include a first codeword forming a leading beam and one or more second codewords forming a combining beam, and the combining beam may be selected in a set of beams orthogonal to the leading beam and the set of the beams orthogonal to the leading beam may be determined dependent on an uplink payload size for the CSI transmission.

Advantageous Effects

According to an embodiment of the present disclosure, more accurate channel state information of a user equipment can be reported to a base station in a wireless communication system supporting a multi-antenna system.

Further, according to an embodiment of the present disclosure, in a wireless communication system supporting a multi-antenna system, in particular, when a linear combining codebook that combines beams in units of subbands is used, a feedback size of channel state information can be reduced.

Advantages which can be obtained in the present disclosure are not limited to the aforementioned effects and other unmentioned advantages will be clearly understood by those skilled in the art from the following description.

