Closed-Loop LOS MIMO Codebook Design With Low Feedback Overhead
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing wireless communications systems face challenges in achieving accurate precoding for line-of-sight (LOS) multiple-input multiple-output (MIMO) communications, particularly when using open loop precoders, which can be inaccurate and have high overhead, especially with large numbers of antennas.
Innovation Solution
The use of closed loop precoders that incorporate distance feedback and LOS MIMO channel state feedback, based on transmitter and receiver array configurations, to improve precoding accuracy with reduced overhead, using Slepian sequences or Hermite-Gaussian polynomials for precoder design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If open loop precoders are used for LOS MIMO communications, then device complexity is reduced, but precoding accuracy deteriorates
Solution Approach 1:
The patent implements closed-loop precoding where the receiver feeds back channel state information (CSI) including distance metrics to the transmitter. This feedback mechanism enables the transmitter to select appropriate precoders from codebooks designed for LOS MIMO channels, achieving high precoding accuracy without requiring full channel knowledge at the transmitter side, thus maintaining relatively low device complexity.
Solution Approach 2:
The patent changes the parameter representation by using distance-based metrics and geometric channel state information instead of full channel matrices. The codebooks are designed based on distance intervals and LOS channel characteristics, allowing the system to adapt precoder selection to varying channel conditions while reducing the computational burden compared to traditional methods.
2Measurement precision
If SVD precoder with full channel knowledge is used, then precoding accuracy is improved, but overhead increases
Solution Approach 1:
The patent extracts only the essential components needed for LOS MIMO precoding - specifically distance metrics and geometric channel state information - rather than requiring full channel matrix feedback. The codebooks are designed to work with this extracted information, achieving accurate precoding while significantly reducing the amount of feedback overhead compared to full channel knowledge requirements.
Solution Approach 2:
The patent creates simplified codebooks that capture the essential characteristics of LOS MIMO channels based on distance intervals. These codebooks serve as pre-computed solutions that approximate the optimal precoders without requiring the transmitter to perform complex SVD calculations on full channel matrices, thus reducing overhead while maintaining accuracy.
3Measurement precision
If codebook size is increased for better precision, then precoding accuracy is improved, but device complexity increases
Solution Approach 1:
The patent segments the codebook into multiple sub-codebooks, each corresponding to specific distance intervals. This segmentation allows the receiver to first determine the distance interval and then select from the appropriate sub-codebook, achieving high precoder selection accuracy without requiring the system to handle a single large complex codebook. The segmented structure reduces computational complexity while maintaining precision.
Data Source
AI summary
Methods, systems, and devices for wireless communications are described. A transmitted may use a closed loop precoder for line-of-sight (LOS) multiple-input multiple-output (MIMO) communications that uses information such as distance feedback or LOS MIMO channel state feedback. A closed loop precoder may be associated with less overhead than a precoder based on full channel knowledge, such as an SVD precoder. A receiver may estimate a channel based on channel state information reference signals transmitted by the transmitter and calculate a spectral efficiency for one or more precoders of a set of precoders associated with the channel for a LOS MIMO mode. The receiver may send feedback to the transmitter that indicates a selected precoder of the set of LOS MIMO precoders based on the calculated spectral efficiencies. The transmitter may precode messages using the reported closed loop precoder.