Frequency-Domain Peak Power Reduction in OFDM Systems
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Solution Overview
Problem
Existing time domain solutions for reducing peak-to-average power ratio (PAPR) in OFDM signals face challenges in differentiating between sub-carriers and require reserved sub-carriers, leading to inefficiencies and increased complexity, particularly due to the need for conversions between time and frequency domains.
Innovation Solution
A frequency domain peak power reduction (FPPR) system that performs peak power reduction directly in the frequency domain using error path processing and weighting of sub-carriers based on their tolerance, minimizing computational complexity and utilizing the guard band for improved performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If time domain solutions are used for peak power reduction, then peak power can be reduced, but the ability to differentiate between sub-carriers is lost and reserved sub-carriers are required
Solution Approach 1:
The patent segments the frequency spectrum into multiple sub-carriers, each processed independently with individual weighting factors. This allows differentiation between sub-carriers in the frequency domain while achieving peak power reduction, avoiding the limitations of time-domain approaches that treat the signal as a whole.
Solution Approach 2:
The patent applies local quality by assigning different weighting factors to different sub-carriers based on their specific EVM requirements and tolerance to degradation. This localized approach allows optimal peak power reduction for each sub-carrier without uniformly affecting all carriers, thereby reducing overall system complexity.
2Power
If time domain solutions are used for peak power reduction, then peak power can be reduced, but conversions between time and frequency domains are required
Solution Approach 1:
Instead of converting time-domain signals to frequency domain for processing and then back (the conventional approach), the patent inverts the approach by working directly in the frequency domain. This eliminates the need for repeated FFT/IFFT conversions, reducing computational complexity while maintaining peak power reduction capability.
3Power
If reserved sub-carriers are used for peak power reduction, then peak power can be reduced, but allocated spectrum for communication is reduced
Solution Approach 1:
The patent changes the parameter of weighting factors applied to sub-carriers dynamically based on their EVM requirements and peak power conditions. By adjusting these parameters rather than reserving fixed sub-carriers, the system achieves peak power reduction while maximizing the use of available spectrum for communication.
Data Source
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AI summary
A system and method are provided for frequency domain peak power reduction on a plurality of orthogonal frequency divisional multiplexing (OFDM) signals in a communications system, wherein frequency domain processing of at least one OFDM signal carrier is iteratively performed to reduce peak power transmissions. OFDM signal carriers can include both in-band sub-carrier signals, and guard-band sub-carrier signals. Each iteration of peak power reduction takes as an input the frequency domain representation of the signal from the previous iteration that has been altered with respect to an error signal also represented in the frequency domain, determines an error signal (in the frequency domain), and subtracts this from the input to produce a further peak power reduced frequency domain signal. If there are no peaks above the configured peak power reduction threshold, then the signal passes through the FPPR iterations with no change.