Crest Factor Reduction in Multi-Carrier Beamforming
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Solution Overview
Problem
Conventional crest factor reduction (CFR) techniques in multi-carrier multi-channel networks result in low signal-to-noise ratios (SNRs) due to variations in clip noise patterns, leading to poor signal quality and increased dropped calls, as they introduce clipping noise after beamforming weight vectors are applied, causing the noise pattern to differ from the signal pattern.
Innovation Solution
Introducing clipping noise into carrier signals prior to digital beam forming and modulation, with the amount of clip noise determined based on estimated transmission signals, ensuring both signal and noise follow the same phase and amplitude manipulations, thereby maintaining consistent antenna patterns and reducing SNR issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If clipping noise is introduced after beamforming weight vectors are applied, then crest factor reduction is achieved, but signal-to-noise ratio deteriorates due to noise pattern variations
Solution Approach 1:
The patent applies clipping noise introduction before beamforming weight vector application, rather than after. This preliminary action ensures that the clipping noise undergoes the same beamforming processing as the signal, maintaining consistent antenna patterns and preventing noise pattern variations that would otherwise degrade SNR.
Solution Approach 2:
The patent merges the clipping noise processing with the beamforming processing by applying the same weight vectors to both signal and noise. This combining approach ensures that noise and signal follow identical spatial transformations, eliminating the mismatch between signal and noise antenna patterns.
2Loss of energy
If clipping noise is introduced into carrier signals, then power amplifier efficiency is improved, but device complexity increases due to additional processing stages
Solution Approach 1:
The clipping noise is introduced at the carrier signal stage, before modulation and beamforming, allowing the noise to be processed through the existing signal processing chain without requiring separate dedicated hardware for noise processing, thus limiting the increase in device complexity.
Solution Approach 2:
The existing beamforming and modulation processing stages serve dual purposes: they process both the clipped carrier signal and the introduced clipping noise simultaneously. This multi-functionality approach avoids the need for separate processing paths, minimizing additional device complexity.
Data Source
AI summary
Crest factor reduction (CFR) can be performed on the various carriers of a multi-carrier multi-channel signal prior to modulation and/or beamforming operations in order to improve signal-to-noise ratios (SNRs) in the resulting wireless communication. More specifically, clipping noise is introduced into each of the individual carrier signals prior to application of the beamforming weight vectors, as well as prior to carrier modulation, thereby causing the beamforming weight vectors to be applied to both the signal and the clipping noise. As a result, variations between the signal antenna pattern and the clipping noise antenna pattern are reduced, which mitigates and/or reduces low SNR spatial locations in which the signal would have been drowned out by the clipping noise under conventional CFR.