OFDM Constellation Adjustment for PAPR Reduction Under EVM Limits

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Solution Overview

Problem

OFDM and OFDMA systems exhibit high peak-to-average power ratios (PAPR), which reduce power amplifier efficiency, and existing Active Constellation Extension (ACE) methods introduce constellation errors that violate error vector magnitude (EVM) limits set by standards like 3GPP-LTE and IEEE 802.16e.

Innovation Solution

A method for signal processing using a constellation points adjustment module to perform an ACE procedure, identifying and translating symbols outside a bounded region to minimize EVM, with the option to move symbols to the origin, border, or interior of the bounded region, thereby reducing PAPR while maintaining compliance with EVM standards.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If Active Constellation Extension (ACE) is used to reduce PAPR, then power amplifier efficiency is improved, but error vector magnitude (EVM) limits are violated

Engineering Contradiction:

Improvepower amplifier efficiencyVSAvoiderror vector magnitude compliance

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

The patent applies parameter changes by modifying the constellation points in the frequency domain before IFFT transformation. Specifically, it adjusts the amplitude and phase parameters of selected subcarriers to reduce time-domain signal peaks while maintaining frequency-domain spectral properties. This resolves the contradiction by changing signal parameters to achieve both PAPR reduction and EVM compliance simultaneously

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent implements preliminary action by performing constellation manipulation in the frequency domain before the IFFT operation. By pre-adjusting the frequency-domain symbols and applying windowing functions, the system prepares the signal to have reduced peaks in the time domain, thereby achieving PAPR reduction before power amplification occurs while maintaining EVM specifications

Inventive Principle:

Principle #10Preliminary action

2Use of energy by moving object

If constellation points are adjusted to reduce PAPR, then power efficiency is improved, but signal accuracy deteriorates

Engineering Contradiction:

Improvepower efficiencyVSAvoidsignal accuracy

Core Design Contradiction:

Use of energy by moving objectVSMeasurement precision

Solution Approach 1:

The patent applies local quality by selectively adjusting only specific constellation points rather than uniformly modifying the entire signal. It identifies and manipulates only those frequency-domain symbols that contribute to peak formation, leaving other symbols unchanged. This localized approach reduces PAPR while minimizing impact on overall signal accuracy and maintaining spectral integrity

Inventive Principle:

Principle #3Local quality

Data Source

PatentUS20100272195A1Peak-to-average power ratio reduction with bounded error vector magnitude

Publication Date: 2010.10.28 XILINX INC

AI summary

Method and apparatus for signal processing to minimize the peak to average power ratio of an Orthogonal Frequency Division Multiplexing (“OFDM”) or Orthogonal Frequency Division Multiple Access (“OFDMA”) signal with bounded error vector magnitude for an integrated circuit are described. An Active Constellation Extension (“ACE”) iteration, using a constellation points adjustment module, is performed. Symbols outside of a bounded region after the ACE iteration are identified. The bounded region is determined responsive to an error vector magnitude target. The symbols identified are translated to the bounded region.