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EP-4738717-A2 - METHOD FOR DETERMINING PRECODING MATRIX INDICATOR, USER EQUIPMENT, AND BASE STATION

EP4738717A2EP 4738717 A2EP4738717 A2EP 4738717A2EP-4738717-A2

Abstract

A method for determining a precoding matrix indicator, user equipment, and a base station are disclosed in embodiments of the present invention. The method includes: receiving a first reference signal set sent by a base station, where the first reference signal set is associated with a user equipment-specific matrix or matrix set; selecting a precoding matrix based on the first reference signal set, where the precoding matrix is a function of the user equipment-specific matrix or matrix set; and sending a precoding matrix indicator to the base station, where the precoding matrix indicator corresponds to the selected precoding matrix. In the embodiments of the present invention, CSI feedback precision can be improved without excessively increasing feedback overhead, thereby improving system performance.

Inventors

  • WANG, JIANGUO
  • ZHOU, YONGXING
  • WU, YONG
  • XIA, LIANG

Assignees

  • Huawei Technologies Co., Ltd.

Dates

Publication Date
20260506
Application Date
20130510

Claims (14)

  1. A method for determining a precoding matrix indicator, PMI, comprising: receiving (101) a first reference signal set sent by a base station, wherein the first reference signal set is associated with a user equipment-specific matrix set, and each matrix in the user equipment-specific matrix set comprises at least one column, and each column comprises at least two rows, and wherein a reference signal in the first reference signal set is channel state information reference signal, CSI-RS; selecting (102) a precoding matrix W based on the first reference signal set; wherein the precoding matrix W is a product of two matrices W 1 and W 2 , W = W 1 W 2 , the matrix W 1 is a block diagonal matrix comprising two same block matrices X, each block matrix X is a kronecker product of two matrices C and D, X=C ⊗ D, and at least one matrix in the two matrices C and D is associated with the user equipment-specific matrix set, each matrix of the matrix W 2 , the matrix C and the matrix D comprises at least one column, and each column comprises at least two rows; and sending (103) a PMI to the base station, wherein the PMI corresponds to the selected precoding matrix W.
  2. The method according to claim 1, wherein the PMI comprises three indexes i 6 , i 7 and i 8 , wherein the index i 6 indicates the matrix C, the index i 7 indicates the matrix D, and the index i 8 indicates the matrix W 2 .
  3. The method according to claim 1 or 2, wherein the matrix C and the matrix D are respectively a function of matrix A and matrix B in the user equipment-specific matrix set.
  4. The method according to any one of claims 1 to 3, wherein the matrix C is not equal to the matrix A, and the matrix D is not equal to the matrix B.
  5. The method according to any one of claims 1 to 4, wherein each column in the matrix C is a column in the matrix A; and each column in the matrix D is a column in the matrix B.
  6. The method according to any one of claims 1 to 5, wherein the matrix A is a matrix whose columns are discrete Fourier Transformation, DFT, vectors; and the matrix B is a matrix whose columns are DFT vectors.
  7. The method according to any one of claims 1 to 6, wherein the matrix W 2 is used for selection or weighted combination of column vectors in the matrix W 1 , so as to form the matrix W.
  8. The method according to any one of claims 1 to 7, wherein the user equipment-specific matrix set is notified by the base station.
  9. The method according to any one of claims 1 to 8, wherein the precoding matrix W supports quantization in a vertical direction and a horizontal direction.
  10. The method according to any one of claims 2 to 9, wherein the PMI is sent using a physical uplink control channel, PUCCH, or a physical uplink shared channel, PUSCH.
  11. A mobile apparatus, configured to perform the method according to any one of claims 1 to 10.
  12. A computer-readable storage medium comprising instructions which, when executed by a computer, cause the computer to carry out a method according to any one of claims 1 to 10.
  13. A computer program comprising instructions which, when the program is executed by a computer, cause the computer to carry out a method according to any one of claims 1 to 10.
  14. A processing chip, configured to perform the method according to any one of claims 1 to 10.

Description

TECHNICAL FIELD Embodiments of the present invention relate to the field of wireless communications, and in particular, to a method for determining a precoding matrix indicator, user equipment, and a base station. BACKGROUND By using a transmit BF (Beam Forming, beam forming) or precoding technique and by using a receive signal combination technology, an MIMO (Multiple Input Multiple Output, multiple input multiple output) wireless system can obtain diversity and array gains. A typical system that uses BF or precoding may usually be represented as: y=HVs+n where y is a received signal vector, H is a channel matrix, V is a precoding matrix, S is a transmitted symbol vector, and n is measured noise. Optimal precoding usually requires that a transmitter know entirely CSI (Channel State Information, channel state information). In a common method, user equipment quantizes instantaneous CSI and feeds back the instantaneous CSI to a base station. CSI information fed back by an existing LTE R8 system includes an RI (Rank Indicator, rank indicator), a PMI (Precoding Matrix Indicator, precoding matrix indicator), a CQI (Channel Quality Indicator, channel quality indicator), and the like, where the RI and the PMI indicate respectively a quantity of used layers and a used precoding matrix. A set of used precoding matrices is generally referred to as a codebook (sometimes each precoding matrix in the set is referred to as a code word). An existing LTE (Long Term Evolution, Long Term Evolution) R8 4-antenna codebook is designed based on Householder (Househoulder) transformation, and an R10 system further introduces double-codebook design for 8-antenna. The foregoing two codebooks are mainly for antenna design of a common base station. A common base station uses a fixed or remote electrical tilt downtilt to control a beam direction of an antenna in a vertical direction, and a beam direction of the antenna may be adjusted dynamically through precoding or beam forming only in a horizontal direction. To reduce system costs and to achieve a higher system capacity and coverage requirement at the same time, an AAS (Active Antenna Systems, active antenna system) has been widely deployed in practice. For the currently launched LTE R12 standard, enhancement of communication performance after the AAS system is introduced is considered. Compared with a conventional base station antenna, the AAS further provides design flexibility in a vertical direction, and meanwhile, for convenience of deployment, antenna ports in the ASS may be further increased. For example, a quantity of antenna ports included in the current LTE R12 and future evolved versions may be 8, 16, 32, 64 or even larger. A new requirement for codebook design, especially in aspects such as precoding performance, feedback overhead compromise, and air interface support, is proposed. In such a background, a new design solution for an AAS base station antenna, and especially for a precoding matrix and a feedback process of the AAS base station antenna, needs to be proposed. SUMMARY Embodiments of the present invention provide a method for determining a precoding matrix indicator, user equipment, and a base station, which can improve CSI feedback precision without excessively increasing feedback overhead, thereby improving system performance. According to a first aspect, a method for determining a precoding matrix indicator is provided, including: receiving a first reference signal set sent by a base station, where the first reference signal set is associated with a user equipment-specific matrix or matrix set; selecting a precoding matrix based on the first reference signal set, where the precoding matrix is a function of the user equipment-specific matrix or matrix set; and sending a precoding matrix indicator PMI to the base station, where the PMI corresponds to the selected precoding matrix. With reference to the first aspect and the foregoing implementation manner of the first aspect, in a first implementation manner of the first aspect, the user equipment-specific matrix or matrix set is notified by the base station to user equipment. With reference to the first aspect and the foregoing implementation manners of the first aspect, in a second implementation manner of the first aspect, the first reference signal set includes one or more reference signal subsets, and the reference signal subset corresponds to a co-polarized antenna port subset, or corresponds to an antenna port subset that is arranged in a same direction in an antenna port array, or corresponds to an antenna port subset that is located at a quasi-co-location. With reference to the first aspect and the foregoing implementation manners of the first aspect, in a third implementation manner of the first aspect, that the precoding matrix is a function of a subset of the user equipment-specific matrix or matrix set includes that: the precoding matrix W is a product of two matrices W1 and W2, W = W1W2 , where th