Uplink-CSI-based downlink channel reconstruction method for FDD system

Abstract

The invention discloses an uplink-channel-state-information-(CSI)-based downlink channel reconstruction method for a frequency division duplex (FDD) system. A base station estimates an uplink CSI by using an uplink detection signal, wherein the uplink CSI includes a gain / gains, a direction angle / direction angles, and a delay / delays of one or more propagation paths; a downlink sparse pilot frequency is sent or a downlink pilot frequency is sent in the estimated one or more propagation path directions by using uplink and downlink angle reciprocity; user equipment carries out estimation again byusing the downlink pilot frequency and feeds back a gain of each propagation path; and then the base station reestablishes a downlink channel by using the direction angle and delay, estimated by the uplink, of each propagation path as well as the gain, re-estimated and fed back by the user equipment, of each propagation path. With the downlink CSI reconstruction method for the FDD system, a problem of obtaining downlink CSI of a large-scale multi-input multi-output system of the FDD is solved.

Description

technical field [0001] The present invention relates to a downlink channel reconstruction method based on uplink channel state information CSI for frequency division duplex FDD system, in particular to a downlink channel reconstruction method based on uplink CSI for FDD massive multiple input multiple output MIMO system. Background technique [0002] Massive MIMO is one of the important technologies of the fifth-generation mobile communication. By configuring a large-scale antenna array in the base station, it can greatly improve the spatial degree of freedom, improve the dimension of space division multiple access, smooth thermal noise and fast fading. In order to obtain high-dimensional CSI and control the overhead of pilots and control channels, massive MIMO systems often use pilot multiplexing, and non-orthogonal pilots are used between adjacent cells, resulting in serious pilot pollution. And because the coherence time of the channel is limited, how to complete the chan...

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Problems solved by technology

[0004] Preliminary research has been carried out on the CSI acquisition of FDD massive MIMO systems. At present, the widely used strategy is to obtain the channel correlation matrix for downlink transmission. However, this method requires a large overhead, and the information acquisition is difficult and the downlink transmission performance is not good.

Another research result proposes that the gain, direction angle, and delay of the uplink and downlink propagation paths are completely equal, and the downlink channel can be directly reconstructed only by using the uplink estimation results, so that no downlink training process is required. However, the actual channel measurement results show that the downlink channel without downlink training The error of the channel reconstruction result is relatively large, which cannot meet the needs of the actual system

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