Superposition Modulation for IBOC PAPR Reduction

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Solution Overview

Problem

Broadcast amplifiers in digital radio systems face inefficiencies due to high peak-to-average power ratios (PAPR) in OFDM signals, requiring larger transmitters and reduced efficiency, and existing methods to reduce PAPR often compromise signal quality.

Innovation Solution

The method involves using superposition modulation within the OFDM waveform to reduce PAPR-induced constellation noise, allowing for additional bandwidth and flexible trade-offs between data capacity and transmitter power performance, while maintaining compliance with established signal quality specifications.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If PAPR reduction clipping is applied to OFDM signal peaks, then transmitter power efficiency is improved, but constellation noise increases and signal quality deteriorates

Engineering Contradiction:

Improvetransmitter power efficiencyVSAvoidsignal quality

Core Design Contradiction:

Loss of energyVSManufacturing precision

Solution Approach 1:

The patent converts the harmful clipping noise, traditionally viewed as distortion to be minimized, into a beneficial carrier for superposition modulation. By embedding secondary data within the PAPR reduction noise, the system transforms energy that would otherwise be wasted as distortion into useful information transmission, simultaneously improving power efficiency and maintaining signal quality through deliberate noise utilization

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The patent merges two previously separate functions into one: the PAPR reduction clipping operation and the data transmission process. By superimposing an additional modulation layer onto the clipped signal, the system combines power efficiency optimization with enhanced data capacity in a single integrated signal processing chain, eliminating the need to choose between efficiency and quality

Inventive Principle:

Principle #5Merging (Combining)

2Productivity

If higher order modulation is used to increase data capacity, then bandwidth efficiency is improved, but PAPR increases requiring larger transmitters

Engineering Contradiction:

Improvedata capacityVSAvoidtransmitter size

Core Design Contradiction:

ProductivityVSVolume of stationary object

Solution Approach 1:

The patent adds another dimension to the signal by superimposing a second modulation layer onto the existing IBOC signal. This dimensional addition allows simultaneous transmission of primary and secondary data streams without increasing the physical transmitter size, as both data streams share the same frequency spectrum through orthogonal superposition rather than requiring separate channels

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Loss of energy

If transmitter power is reduced to improve efficiency, then energy consumption is improved, but signal coverage and reliability deteriorate

Engineering Contradiction:

Improveenergy consumptionVSAvoidsignal coverage

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

The patent changes the modulation parameters by employing hierarchical modulation with different power allocations for primary and secondary layers. The primary IBOC signal maintains sufficient power for reliable coverage, while the secondary superposition layer uses the remaining power capacity, enabling the system to reduce overall transmitter power while maintaining coverage through optimized parameter distribution

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS11855825B2IBOC compatible superposition modulation by independent modulators utilizing clipping noise from peak-to-average power reduction

Publication Date: 2023.12.26 NAUTEL LTD

AI summary

According to an aspect of the present invention, there is provided a method for providing additional bandwidth to receivers that can decode a higher modulation comprising trading a peak-to-average power ratio (PAPR) reduction induced constellation noise of all or a subset of in-band on-channel (IBOC) carriers within an orthogonal frequency division multiplexing (ODFM) waveform with data carrying superposition modulation.