Method and device for feeding back channel state information (CSI) and method and device for determining CSI are provided. The method for feeding back CSI includes feeding back CSI according to a determined structure of the CSI, where the structure of the CSI includes M CSI subsets; an m-th CSI subset among the M CSI subsets includes km channel information components. The M CSI subsets include N CSI subsets, and an n-th CSI subset among the N CSI subsets includes Ln channel information components which are determined by transforming a group of base vectors.

[Object] To enable more appropriate recognition of an interference situation of a directional beam.

[Solution] Provided is an apparatus including: an acquisition unit that acquires a weight set for forming a directional beam; and a control unit that multiplies a reference signal for channel quality measurement by the weight set. The weight set is a weight set that is able to be generated from a first weight set for acquiring directivity in a first direction, a second weight set for acquiring directivity in a second direction, and a third weight set for phase adjustment of dual layer multiple-input multiple-output (MIMO). The third weight set is a specific one of a plurality of weight sets for phase adjustment of dual layer MIMO.

A wireless communication device can include a communication control interface. Beamforming circuitry coupled to the communication control interface receives, over the communication control interface, an index value into a coarse codebook and an offset vector. The index value indicates a value within the coarse codebook, and the offset vector indicates an offset value for a desired beam relative to the index value. The beamforming circuitry determines a new beam direction based on the index value and the offset vector using one of interpolation and extrapolation.

A method and apparatus for reporting Channel State Information (CSI) by a User Equipment (UE), for fractional beamforming using a massive antenna array of a Base Station (BS) in a wireless communication system are disclosed. The method includes receiving information about a plurality of Reference Signal (RS) resources from the BS, generating CSI including a sub-precoder for at least one of the plurality of RS resources, and a Channel Quality Indicator (CQI) and a Rank Indicator (RI) for all of the plurality of RS resources, and reporting the CSI to the BS. The massive antenna array is divided by rows or columns into partitions and the plurality of RS resources correspond to the partitions.

Embodiments relate to a feedback method channel state information. The method includes acquiring, by user equipment, first channel state information based on a first channel state information measurement resource that is configured by a base station and that corresponds to a first antenna port representing a horizontal dimension. The method also includes acquiring, based on a second channel state information measurement resource, which is configured by the base station, of a second antenna port representing a vertical dimension, second channel state information. The method also includes feeding back channel state information to the base station, which includes: feeding back the first channel state information to the base station according to a first feedback mode, and feeding back the second channel state information to the base station according to a second feedback mode, where the second feedback mode is different from the first feedback mode.

Disclosed in the present application is a method by which a terminal generates channel state information for multi-antenna-based beamforming in a wireless communication system. Specifically, the method comprises the steps of: receiving a first pilot signal and a second pilot signal from a base station; selecting a first rank on the basis of the first pilot signal and selecting a second rank on the basis of the second pilot signal; setting a rank search range for a three-dimensional channel on the basis of the first rank and the second rank; and selecting a rank for the three-dimensional channel within the rank search range and a precoder corresponding to the rank for the three-dimensional channel.

Enhanced channel state information (CSI) feedback is disclosed for full dimensional multiple input, multiple output (FD-MIMO) operations. In one aspect, a single CSI process is defined that is configured with an azimuth and elevation CSI-reference signal (RS) ports. A user equipment (UE) will send a precoding matrix indictor (PMI) report including a precoding matrix indicator (PMI) for the azimuth ports and a PMI for the elevation ports. One of the PMIs is assigned a low rank. The base station will use the two PMIs to create a whole channel precoding matrix. In another aspect, a single CSI process is configured having a plurality of CSI-RS resources. The UE generates channel measurement information for each of the CSI-RS resources, but only sets a CSI report to the base station of a subset of the total number of resources.

A communication method includes receiving, by a terminal device, first information from a network device. The first information indicates a precoding matrix. The communication method also includes determining, by the terminal device, the precoding matrix based on the first information. The precoding matrix is for sending an uplink signal. The precoding matrix is determined based on a first matrix and a second matrix. At least one of the first matrix is determined from a first matrix set based on the first information, wherein the first matrix set is determined based on a horizontal-dimension parameter of an antenna of the terminal device; or the second matrix is determined from a second matrix set based on the first information, wherein the second matrix set is determined based on a vertical-dimension parameter of the antenna.

In accordance with an example embodiment of the present invention, a method comprising: selecting, by a user equipment, a subset of linear combination coefficients from a linearized two-dimensional matrix having columns of frequency domain components and rows of spatial beams components for channel state information determination, wherein the number of linear combination coefficients in the subset is less than all of the linear combination coefficients; determining indication comprising information associated with column indices of the selected subset of linear combination coefficients from the linearized two-dimensional matrix, wherein the indication excludes the index of the column with lowest index of the linearized two-dimensional matrix; determining compressed channel state information comprising locations in the linearized two-dimensional matrix of the subset of linear combination coefficients and corresponding values of the linear combination coefficients at those locations; and reporting, from the user equipment toward the base station, the compressed channel state information.

A base station capable of communicating with a user equipment (UE) includes a transceiver configured to transmit downlink signals containing first and second antenna numbers, first and second oversampling factors indicating respective oversampling rates in first and second dimensions for each beam group, first and second quantities of beams indicating respective quantities of beams in the first and second dimensions for each beam group, and first and second beam skip numbers indicating respective differences of leading beam indices of two adjacent beam groups in the first and second dimensions, receive uplink signals containing a plurality of precoding matrix indicators (PMIs) from the UE. Other embodiments including methods and UEs and methods are disclosed.