Peak Power Reduction in Eigenmode MIMO Systems
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Solution Overview
Problem
Eigenmode MIMO transmission systems face challenges in reducing peak power without deteriorating bit error rates, particularly due to nonlinear distortion in power amplifiers caused by large amplitude peaks in OFDM signals, which leads to EVM deterioration and increased bit error rates.
Innovation Solution
A peak power reduction device that divides digital information into streams, selects modulation schemes based on eigenvalues, performs singular-value decomposition, and limits SNR to reduce peak power by converting peak signals into the frequency domain and subtracting peak components, thereby controlling EVM deterioration according to modulation schemes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If peak power reduction is performed by filtering peak signals in OFDM transmission, then peak power is reduced, but EVM deterioration occurs and bit error rate increases
Solution Approach 1:
The transmission signal is divided into multiple streams corresponding to different singular values. Peak power reduction is applied selectively to specific streams based on their eigenvalues and modulation schemes, rather than uniformly to the entire signal. This segmentation allows differential treatment of peak components in different streams.
Solution Approach 2:
Different quality requirements are applied to different streams. Streams with higher eigenvalues and more robust modulation schemes can tolerate greater peak power reduction, while streams with lower eigenvalues maintain higher quality. This local quality approach optimizes the balance between peak power reduction and EVM deterioration for each stream.
2Productivity
If transmission capacity is increased by using high-order modulation schemes in eigenmode MIMO, then data rate increases, but the system becomes more sensitive to EVM deterioration from peak power reduction
Solution Approach 1:
The system dynamically adjusts the peak power reduction amount based on modulation scheme parameters and eigenvalue characteristics. For high-order modulation schemes (e.g., 64QAM, 256QAM), the peak power reduction is controlled to be more conservative, while for robust schemes (e.g., QPSK), greater reduction is permitted. This parameter-based adaptation resolves the contradiction between capacity and reliability.
3Reliability
If power amplifier back-off is increased to avoid nonlinear distortion, then EVM deterioration is reduced, but power amplifier efficiency decreases
Solution Approach 1:
Instead of applying uniform peak power reduction to all signals (excessive action), the system applies partial peak power reduction only to specific streams and time instances where it is most effective. This partial action approach achieves sufficient EVM protection while minimizing the impact on power amplifier efficiency and overall system performance.
Data Source
AI summary
A peak power reduction device includes a unit for dividing digital information to be transmitted into a plurality of streams; a unit for selecting the modulation level of the streams and distribution of transmission power according to a transmission state; a unit for performing singular-value decomposition on the transmission path characteristic of a streams and precoding the resultant data by a right singular value matrix; a unit for performing complex mapping on the subcarrier of a stream according to the modulation level; a unit for converting a complex mapping signal into a time domain signal; a first unit for storing a conversion result as a time domain signal; a second unit for calculating a peak time signal exceeding a predetermined threshold value from a peak value, if any exists, that exceeds a prescribed threshold value for the amplitude of the time domain signal.