Patent ID: 9496941
Filing Date: 2016-11-15
CPC Classification: H04B,H04L

Claim Text:
1. A method of feedback for a 4-antenna downlink channel in a Multiple Input Multiple Output (MIMO) system, comprising: detecting a downlink multiple-antenna channel; determining a first codeword in a first level codebook corresponding to the rank of R according to a long-term broadband channel characteristic estimated from a result of the detection, wherein any codeword in the first level codebook is a diagonal matrix, two same 2×C block matrices exist on a diagonal line, and C column vectors of the 2×C block matrix are selected from Q feeding back an index of the first codeword; determining a second codeword in a second level codebook corresponding to the rank of R according to a short-term channel characteristic estimated from the result of the detection and the first codeword, wherein any codeword in the second level codebook is a 2C×R matrix, and each column of the 2C×R matrix is formed of one C×1 beam selection vector and one C×1 beam selection vector comprising phase offset information; and feeding back an index of the second codeword; and wherein: