Over-the-Air DPD Training for PA Nonlinearity Compensation
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Solution Overview
Problem
Current wireless communication systems, particularly in new radio (NR) and LTE technologies, face limitations in improving spectral efficiency and power efficiency due to non-linear distortions caused by high-power amplifiers, which are not effectively addressed by existing methods such as power back-off or conventional digital pre-distorters (DPDs) that require expensive feedback hardware.
Innovation Solution
The method involves training digital pre-distorters using real-time over-the-air transmissions and receptions, allowing for the estimation and configuration of DPD coefficients without the need for expensive feedback hardware, thereby reducing non-linear distortions and improving power efficiency by digitally pre-distorting signals to account for PA non-linearity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional digital pre-distorters are used to reduce non-linear distortions, then power efficiency is improved, but device complexity and cost increase due to expensive feedback hardware requirements
Solution Approach 1:
The patent extracts and removes the expensive feedback hardware component from the DPD system. Instead of using traditional feedback paths that require additional receivers and processing chains, the invention uses over-the-air self-feedback where the transmitted signal itself serves as the reference, eliminating the need for complex feedback hardware while maintaining DPD functionality
Solution Approach 2:
The patent makes the transmitter serve multiple functions: it both transmits the signal and captures the received signal for DPD coefficient calculation. The same RF chain and antenna are used for both transmission and reception purposes, eliminating the need for separate feedback hardware and reducing overall device complexity
2Reliability
If power back-off is used to avoid non-linear distortions, then signal quality is maintained, but power efficiency deteriorates
Solution Approach 1:
The patent applies preliminary action by pre-distorting the signal before transmission to compensate for expected non-linear distortions. The DPD calculates correction coefficients based on over-the-air measurements and applies them in advance to the transmitted signal, allowing the power amplifier to operate at higher power levels without producing harmful distortions
Solution Approach 2:
The patent converts the harmful non-linear distortions produced by power amplifiers into beneficial information. By measuring the actual distortions through over-the-air reception and using them to calculate DPD coefficients, the system transforms the harmful effect into useful data that enables correction and improves overall power efficiency
Data Source
AI summary
Certain aspects of the present disclosure provide techniques for training a digital pre-distorter (DPD) using real-time over-the-air transmissions and receptions by a user equipment (UE). A method for training the DPD generally includes transmitting a signal, generated by a transmitter front end, via a first port; sampling the signal, received over the air, at a second port; performing signal processing cleaning (e.g., synchronization, linear over-the-air channel estimation and equalization); calculating coefficients for a DPD; and configuring the DPD with the coefficients, for use in digitally pre-distorting sub sequent transmissions.