Pre-coding Data Using Channel Statistics to Compensate Quantization Errors
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Solution Overview
Problem
In radio access technologies, particularly those using multiple-input multiple-output (MIMO) antenna systems, linear beamforming or pre-coding faces performance degradation due to channel quantization errors in frequency division duplex (FDD) systems, especially in long-term evolution (LTE) standards-based protocols, where implicit quantized channel state information (CSI) feedback does not accurately reflect channel conditions.
Innovation Solution
Compensating for quantization errors by incorporating channel statistics, such as mean and covariance, into the pre-coding process, allowing for improved signal gain and transmission performance by using a conditional covariance matrix or directly utilizing channel statistics for pre-coding, thereby enhancing beamforming and data transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If quantized CSI feedback is used in FDD systems, then feedback overhead is reduced, but channel quantization error increases causing performance degradation
Solution Approach 1:
The patent introduces channel statistics (covariance matrix) as an intermediary that bridges the gap between quantized CSI feedback and actual channel conditions. The base station uses the covariance matrix to compensate for quantization errors, effectively mediating between the limited feedback information and the required accurate channel knowledge for optimal pre-coding
Solution Approach 2:
The patent changes the parameter representation from direct quantized channel coefficients to statistical parameters (covariance matrix eigenvalues and eigenvectors). By transforming the channel information into statistical domain, the system achieves better performance with reduced feedback overhead, as statistics capture essential channel characteristics without requiring precise instantaneous channel knowledge
2Power
If channel statistics are incorporated into pre-coding, then signal gain increases, but computational complexity increases
Solution Approach 1:
The patent segments the channel information processing into two independent parts: (1) statistical parameters (covariance matrix) that change slowly and can be averaged over time, and (2) instantaneous quantized CSI feedback. This segmentation allows the system to use computationally efficient operations on the statistical part while incorporating limited instantaneous information, reducing overall complexity compared to processing full channel matrices
Solution Approach 2:
The patent performs preliminary computation of channel statistics (covariance matrix calculation and eigen-decomposition) in advance, before the actual pre-coding operation. The base station pre-computes the covariance matrix from received feedback and stores its eigenvalues and eigenvectors, so that when pre-coding is needed, the system only needs to perform simple matrix operations with pre-computed statistics rather than complex real-time channel analysis
Data Source
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Figure 2B~3A
Figure 3B~4
AI summary
Provided are an apparatus and method for pre-coding data based on quantized channel state information and channel statistics. In use, channel statistics are collected. Further, one or more reference signals are sent to a wireless device via at least one channel.Thereafter, quantized channel state information is received that corresponds to the at least one channel, where the quantized channel state information is sent by the wireless device based on the one or more reference signals. Data is pre-coded based on the quantized channel state information and the channel statistics. Further, the pre-coded data is transmitted to the wireless device.