OFDM Crest Factor Reduction with ISI Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
OFDM signals exhibit high peak-to-average power ratios, leading to difficulties in signal amplification and increased inter-symbol interference, which result in bandwidth expansion and elevated bit error rates, necessitating a reduction in peak power while controlling ISI.
Innovation Solution
The method involves splitting the OFDM signal into two parallel paths, performing peak reduction processing in the time domain, converting to the frequency domain to adjust ISI, and combining the results to produce a peak power-adjusted signal, utilizing clipping and normalization techniques to manage ISI effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If peak power is compressed or clipped during amplification, then signal amplification becomes easier, but bandwidth increases causing interference in neighboring frequency channels and inter-symbol interference increases
Solution Approach 1:
The patent segments the OFDM signal processing into two parallel paths: one path applies peak reduction processing to reduce peak power, while the other path processes the original signal. These paths are then combined to produce the final output. This segmentation allows the system to benefit from peak power reduction without fully suffering the harmful effects of bandwidth expansion and ISI, as the original signal components are preserved in the combination step.
Solution Approach 2:
The patent changes the parameter of peak power by applying compression or clipping functions to reduce the peak-to-average power ratio. By adjusting the compression ratio or clipping threshold parameters, the system can control the degree of peak power reduction while managing the trade-off with bandwidth expansion and inter-symbol interference.
2Power
If peak-to-average ratio is reduced, then signal amplification difficulty decreases, but inter-symbol interference is induced into the modulation
Solution Approach 1:
The patent divides the signal processing into multiple paths where peak reduction is applied in one path while the original signal is preserved in another path. By combining these paths, the system achieves peak power reduction while maintaining signal integrity and controlling bit error rate through the preservation of original signal components.
Solution Approach 2:
The system uses feedback mechanisms to monitor and control the amount of inter-symbol interference introduced by peak reduction processing. By adjusting processing parameters based on feedback regarding ISI levels and bit error rates, the system optimizes the balance between peak power reduction and maintaining communication reliability.
Data Source
AI summary
A system and method for providing a peak power reduced OFDM communications signal are disclosed. The system and method provide peak reduction processing in the time domain followed by inter-symbol interference (ISI) control processing in the frequency domain to maintain modulation errors introduced by the peak reduction processing to an acceptable level. The processing is preferably done on a parallel signal path and the peak corrections with ISI control are added into the main signal path to provide the peak reduced OFDM signal.