PAPR Reduction in Single-Carrier Telecommunications Systems
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Solution Overview
Problem
In telecommunications, particularly in battery-powered devices, power amplifiers face inefficiencies due to high Peak-to-Average-Power Ratio (PAPR) in single-carrier modulation schemes, leading to reduced talk time and increased heat dissipation, especially with the adoption of higher-order modulation technologies like 16-QAM and 64-QAM.
Innovation Solution
The method involves using a Discrete Fourier Transform (DFT) to generate complex frequency components, permuting them through various shifts or permutations, and applying an Inverse DFT to find the time-domain symbols with the lowest PAPR, which are then selected for processing and transmission, potentially using shaping filters to further reduce PAPR.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If higher-order modulation schemes (16-QAM, 64-QAM) are used to increase data rate, then system capacity is improved, but PAPR increases leading to reduced power amplifier efficiency
Solution Approach 1:
The patent applies preliminary action by performing PAPR reduction processing on the signal before it reaches the power amplifier. Specifically, the system generates multiple candidate signals through signal processing (including permutation and transformation operations) and selects the candidate with the lowest PAPR, thereby preparing the signal in advance to be compatible with the power amplifier's efficiency requirements while maintaining high data rate capabilities
Solution Approach 2:
The patent changes the signal parameters by transforming the signal from the time domain to the frequency domain and back, applying permutations to frequency components, and adjusting signal characteristics to reduce peak power levels. This parameter transformation allows the system to maintain high-order modulation for high data rate while reducing PAPR to improve power amplifier efficiency
2Loss of energy
If constant-envelope signals are used to maintain high power amplifier efficiency, then power amplifier efficiency is improved, but data rate capability is limited
Solution Approach 1:
The patent segments the signal processing into distinct stages: generating multiple candidate signals through permutation operations, evaluating their PAPR characteristics, and selecting the optimal candidate. This segmentation allows the system to separate the high data rate capability (through higher-order modulation) from the power amplifier efficiency requirement (through PAPR reduction), resolving the contradiction between the two
Solution Approach 2:
The patent creates multiple copies or variants of the signal through permutation operations on frequency components. By generating Ns different candidate signals from the same data, the system can select the copy with the most favorable PAPR characteristics, thereby achieving both high data rate and high power amplifier efficiency
3Reliability
If signal amplitude excursions are kept in linear region to avoid distortion, then signal quality is improved, but power amplifier efficiency is reduced
Solution Approach 1:
The system performs preliminary signal processing to reduce the peak amplitude excursions before the signal enters the power amplifier. By pre-computing and selecting signal candidates with lower peak power (through permutation and transformation operations), the system ensures that the power amplifier operates in a more efficient region while still maintaining linear operation to avoid distortion
Solution Approach 2:
The patent incorporates feedback by evaluating the PAPR of generated signal candidates and using this information to select the optimal signal for transmission. The system continuously monitors and adjusts signal characteristics to maintain the best balance between signal quality and power amplifier efficiency
Data Source
AI summary
A single-carrier signal is generated from a number, N, of symbols in a way that results in a low PAPR. This includes generating an initial set of N complex frequency components from the N symbols. Ns different sets of N complex frequency components are generated by, for each of Ns times, permuting the initial set of N complex frequency components by one of Ns possible permutations. Ns different sets of M complex frequency components are generated by mapping each of the Ns different sets of N complex frequency components onto a set of M carrier frequencies. After shaping, an IDFT generates a candidate set of N time-domain symbols from each of the Ns different sets of M complex frequency components. That one of the Ns different candidate sets of N time-domain symbols that is associated with the smallest PAPR is selected for further processing.