Method, device and system for feeding back precoding matrix indication

Abstract

The invention discloses a method, a device and a system for feeding back a precoding matrix indication (PMI), through which the accuracy of the PMI fed back through a terminal side can be improved. The method is applied to a multi-carrier system, wherein the system bandwidth of the multi-carrier system is divided into at least two frequency bands; each frequency band includes a plurality of subbands; after the number of the frequency bands in the system is determined by the terminal, a corresponding broad band codebook and a corresponding subband codebook of each frequency band are respectively chosen by the teminal, and then the corresponding broad band codebook and the corresponding subband codebook of each frequency band are reported to a network side as the PMI. In this way, compared with the traditional mechanism in which one PMI is fed back in the whole system bandwidth, the accuracy of the PMI which is fed back is improved greatly, the network environment of each frequency band in the system bandwidth can be obtained accurately through the network side according to the PIM which is reported through the terminal and consequently a corresponding precoding matrix can be chosen through the network side and then the precoding gain is effectively improved. The invention simultaneously discloses the device for feeding back the PMI and the system for feeding back the PMI.

Description

technical field [0001] The present invention relates to the communication field, in particular to a channel quality feedback method, device and system. Background technique [0002] In a system using Orthogonal Frequency Division Multiplexing (OFDM) technology, such as an Advanced Evolution (LTE) system, multiple data symbols can be sent simultaneously on different subcarriers, and the frequency interval of the subcarriers Orthogonality between multiple data symbols is precisely guaranteed. The OFDM modulator converts the input data symbol stream into multiple parallel data symbol streams through serial-to-parallel conversion. The output of the serial-to-parallel conversion can be viewed as frequency-domain data symbols. The subcarriers on both sides of the bandwidth are not used for data transmission and are called guard bandwidth. The data symbols on some subcarriers within the data bandwidth range will be set as known symbols at the receiving end, and the symbols on th...

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Problems solved by technology

If the system bandwidth is large (for example, the system bandwidth is 20MHz), then these phase rotations in the frequency domain caused by different delays between antennas will make any precoding matrix in the codebook unable to fit the entire system bandwidth

For example, if the codebook uses 8-DFT (DFT, Discrete FourierTransform) vectors, the phase difference between two adjacent vectors is π / 4, then the bandwidth range of the same precoding vector that can be applied is (The delay difference between antennas stipulated by the LTE system cannot exceed 65 nanoseconds at most), which is about 2MHz bandwidth; considering that even if the deviation to the adjacent precoding matrix may not bring too much performance loss, the bandwidth The range is also far from reaching the system bandwidth of 20MHz

In this case, if only a broadband will inevitably result in some sub-bands does not match the channel state of the subband, so that the final precoding matrix does not match the channel state of the subband, so that the base station cannot obtain an accurate precoding matrix, so that the maximum precoding gain cannot be obtained, and then degrade system performance

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