Clipped ADC Sample Reconstruction for Massive MIMO Receivers
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Solution Overview
Problem
In massive MIMO systems, overload distortion caused by clipping in ADCs severely affects signal quality, leading to inaccurate channel state information and data estimation, especially in multiuser MIMO systems, where existing solutions discard information in clipped samples, resulting in suboptimal performance.
Innovation Solution
A method and apparatus for reconstructing clipped samples by exploiting the correlation between clipped and non-clipped samples using a probability density function, replacing clipped sample values with expected values based on this function to minimize mean-squared error, thereby reducing overload distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by stationary object
If ADC resolution is reduced to lower power consumption and hardware costs, then power consumption and system costs decrease, but overload distortion increases
Solution Approach 1:
The patent converts the harmful overload distortion caused by clipping into beneficial information by detecting which samples are clipped and using this information in the MMSE estimation process. The clipping information, which was previously discarded as harmful distortion, is now exploited to improve signal reconstruction accuracy, allowing low-resolution ADCs to achieve performance comparable to high-resolution systems.
2Ease of manufacture
If ADC resolution is reduced to reduce hardware costs, then hardware costs decrease, but signal quality deteriorates
Solution Approach 1:
The patent transforms the harmful clipping effect into useful information by identifying clipped samples and incorporating their clipping status into the MMSE estimation. This allows the system to recover signal quality that would otherwise be lost due to quantization, enabling the use of lower-cost, low-resolution ADCs without sacrificing measurement precision.
Solution Approach 2:
The patent introduces a feedback mechanism where the receiver detects clipping events and feeds this information back into the estimation process. By using the clipped sample information to update the MMSE estimator, the system continuously improves its signal reconstruction, thereby maintaining high measurement precision despite using cost-effective low-resolution ADCs.
3Device complexity
If clipped samples are discarded to simplify processing, then device complexity decreases, but loss of information increases
Solution Approach 1:
Instead of discarding clipped samples as harmful distortion, the patent converts them into beneficial information sources. By detecting clipping events and using the clipped sample indicators in the MMSE estimation, the system recovers information that would otherwise be lost, proving that simple processing decisions can lead to significant information loss.
4Quantity of substance
If ADC resolution is reduced to limit data transfer amount, then data transfer requirements decrease, but overload distortion increases
Solution Approach 1:
The patent converts the harmful overload distortion into useful information by exploiting the clipping pattern. The reduced data transfer from low-resolution ADCs is compensated by using the clipping information to enhance signal reconstruction, thereby maintaining signal quality while minimizing data transfer requirements between RF components and baseband processing units.
Data Source
AI summary
Using information contained in clipped samples from analog-to-digital (ADC) conversion to improve receiver performance, by, for example, reducing the clipping distortion caused by ADCs due to its data resolution constraints. This provides an advantage over existing solutions, which perform suboptimally because the existing solution discard information in tire clipped samples.