Frequency Interleaving for OFDM PAPR Reduction

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Solution Overview

Problem

Existing wireless communication systems face challenges in managing high peak-to-average power ratio (PAPR) of OFDM signals, which leads to distortion and reduced efficiency in power amplifiers.

Innovation Solution

The implementation of PAPR-based frequency interleaving, where a transmitter selects a frequency interleaver that produces an interleaved sequence with the lowest PAPR, and transmits an indication of this interleaver to the receiver, allowing for efficient signal transmission.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If OFDM signals are transmitted using conventional frequency allocation, then spectral efficiency is maintained, but peak-to-average power ratio becomes high causing distortion and reduced power amplifier efficiency

Engineering Contradiction:

Improvepower amplifier efficiencyVSAvoidsignal distortion

Core Design Contradiction:

Loss of energyVSObject-affected harmful factors

Solution Approach 1:

The patent applies parameter changes by modifying the frequency domain representation of OFDM signals through interleaving operations. Specifically, it rearranges the spectral components according to different interleaving patterns (e.g., block interleaving, column-row interleaving) to change the temporal characteristics of the time-domain signal, thereby reducing PAPR while maintaining spectral efficiency

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent segments the frequency domain signal into multiple blocks or groups before applying interleaving operations. By dividing the spectrum into segments and rearranging them, the signal's peak power characteristics are modified, reducing the PAPR without losing overall spectral structure or efficiency

Inventive Principle:

Principle #1Segmentation

2Reliability

If frequency interleaving is applied to reduce PAPR, then power amplifier efficiency improves, but system complexity increases due to additional processing requirements

Engineering Contradiction:

Improvesignal qualityVSAvoidprocessing complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent implements preliminary action by pre-calculating and storing multiple interleaving patterns in lookup tables before transmission. The transmitter selects and applies the appropriate pre-computed pattern based on current signal conditions, avoiding real-time complex calculations and reducing processing complexity while maintaining signal quality

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system changes the parameter of interleaving depth or pattern type dynamically based on channel conditions and signal characteristics. By adjusting these parameters, the system optimizes the balance between PAPR reduction effectiveness and processing complexity, applying more aggressive interleaving only when necessary

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS20250158741A1Peak-to-average power ratio based frequency interleaving

Publication Date: 2025.05.15 QUALCOMM INC

AI summary

In some implementations, a transmitter may transmit an indication of a frequency interleaver, from a set of frequency interleavers, that provides an interleaved sequence for a communication, the frequency interleaver being selected based on a peak-to-average power ratio (PAPR) of the interleaved sequence. The transmitter may transmit the communication including the interleaved sequence, and an index of the interleaved sequence being associated with an input signal that is interleaved via the frequency interleaver when the input signal is in a frequency domain.