FT Pre-coding for PAPR Reduction in Multi-carrier Wireless
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Solution Overview
Problem
Conventional power amplifiers in OFDM and OFDMA systems face inefficiencies due to high peak-to-average power ratio (PAPR), leading to increased costs, heat dissipation, and performance degradation, as they often operate in back-off mode to accommodate large signal peaks, resulting in excessive heat and higher power ratings.
Innovation Solution
The implementation of Fourier Transform pre-coding techniques, specifically using Fast Fourier Transform (FFT) and Discrete Fourier Transform (DFT) blocks, to reduce the PAPR of transmitted signals by pre-coding input symbols before inverse Fourier Transform operations, thereby optimizing power amplifier efficiency and reducing heat dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If power amplifiers operate in back-off mode to accommodate large signal peaks, then PAPR is reduced, but system cost and heat dissipation increase
Solution Approach 1:
The patent applies preliminary action by performing FFT pre-coding on data symbols before they are transmitted through the power amplifier. This preprocessing step modifies the signal characteristics in advance to reduce PAPR, allowing the power amplifier to operate more efficiently without requiring back-off mode, thereby reducing heat dissipation while maintaining signal quality
2Reliability
If power amplifiers use higher power ratings to accommodate signal peaks, then PAPR is managed, but system cost increases
Solution Approach 1:
The patent changes the signal parameters by applying FFT pre-coding transformations to the data symbols, which modifies the amplitude distribution and reduces PAPR. This parameter transformation allows the use of lower-power-rated amplifiers while still handling signal peaks effectively, reducing system cost and complexity
3Device complexity
If conventional OFDM transmission is used without pre-coding, then system complexity is low, but PAPR is high causing performance degradation
Solution Approach 1:
The patent introduces preliminary FFT pre-coding action in the transmission chain, performed before the main IFFT operation. This additional preprocessing step increases system complexity slightly but dramatically improves power amplifier efficiency by reducing PAPR, resolving the contradiction between complexity and reliability
Data Source
AI summary
A subscriber station is provided for use in a wireless network communicating according to a multi-carrier protocol, such as OFDM or OFDMA. The subscriber station comprises: a size M1 Fourier Transform (FT) block that receives input symbols and generates M1 FT pre-coded outputs; a size M2 Fourier Transform (FT) block that receives input symbols and generates M2 FT pre-coded outputs; and a size N inverse Fourier Transform (IFT) block that receives N inputs, including the M1 FT pre-coded outputs and the M2 FT pre-coded outputs, and generates N outputs to be transmitted to a base station. The FT blocks are Fast Fourier Transform blocks or Discrete Fourier Transform blocks. The IFT block is an inverse Fast Fourier Transform block or an inverse Discrete Fourier Transform block.