Three-Level Precoding for Massive MIMO CSI Feedback
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Solution Overview
Problem
In massive MIMO systems with a large number of antennas, the pilot overhead and CSI feedback occupy significant time-frequency resources, severely affecting system throughput.
Innovation Solution
A three-level precoding method is introduced, where the precoding matrix F is determined as F=C1C2W, with C1 using beam information for virtual sector division, C2 reducing spatial dimensions using long-term wideband channel information, and W performing instantaneous channel information feedback, thereby reducing pilot and CSI feedback overheads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a large quantity of antennas are used in massive MIMO, then link quality and spectrum efficiency are improved, but pilot overhead and CSI feedback amount occupy large quantity of time-frequency resources, severely affecting system throughput
Solution Approach 1:
The patent segments the precoding matrix into three levels: first-level precoding matrix based on beam information, second-level precoding matrix based on long-term wideband channel information, and third-level precoding matrix based on instantaneous channel information. This segmentation allows different granularity of channel state information to be feedback at different frequencies, reducing overall feedback overhead while maintaining link quality.
Solution Approach 2:
The patent extracts and separates the channel state information into different components (beam information, long-term wideband channel information, instantaneous channel information) that can be feedback independently. This extraction enables the system to feedback only the essential components at appropriate rates, reducing the total feedback overhead that was previously consuming excessive time-frequency resources.
2Adaptability or versatility
If a large quantity of antennas are used in massive MIMO, then spatial degree of freedom is improved, but pilot overhead and CSI feedback amount increase, compressing time-frequency resources available for data transmission
Solution Approach 1:
The patent applies local quality by differentiating the feedback requirements for different components of channel state information. Beam information (first-level) is feedback at a lower rate as it changes slowly, while instantaneous channel information (third-level) is feedback at a higher rate as it changes rapidly. This localized differentiation of feedback quality reduces overall overhead while maintaining the spatial degree of freedom provided by large-scale antennas.
3Device complexity
If conventional one-level precoding structure is used, then implementation is simple, but when there are relatively large quantity of antennas, pilot overhead and CSI feedback amount occupy large quantity of time-frequency resources
Solution Approach 1:
The patent implements a nested three-level precoding structure where the first-level precoding matrix (beam information) forms the outer layer, the second-level precoding matrix (long-term wideband channel information) forms the middle layer, and the third-level precoding matrix (instantaneous channel information) forms the inner layer. This nested structure allows the system to maintain manageable complexity while efficiently reducing feedback overhead, thereby improving system throughput.
Data Source
AI summary
The present disclosure discloses a channel state information feedback method, a base station, a terminal device, and a system. The method includes: receiving, by a terminal device, a reference signal sent by a base station; determining, by the terminal device, channel state information based on the reference signal; and sending, by the terminal device, the channel state information to the base station, so that the base station determines a precoding matrix F. The precoding matrix F=C1C2W, where C1 is a first-level precoding matrix, C2 is a second-level precoding matrix, and W is a third-level precoding matrix. Channel state information corresponding to C1 includes beam information, channel state information corresponding to C2 includes long-term wideband channel information, and channel state information corresponding to W includes instantaneous channel information. This patent application can reduce total pilot and CSI feedback overheads, thereby improving a system throughput.