Walsh-Domain Neural Network for Power Amplifier Behavioral Modelling and Digital Predistortion

Abstract

This paper investigates the use of Neural Network (NN) nonlinear modelling for Power Amplifier (PA) linearization in the Walsh-Hadamard transceiver architecture. This novel architecture has recently been proposed for ultra-high band width systems to reduce the transceiver power consumption by extensive parallelization of the digital baseband hardware. The parallelization is achieved by replacing two-dimensional quadra ture modulation with multi-dimensional Walsh-Hadamard mod ulation. The open research question for this architecture is whether conventional baseband signal processing algorithms can be similarly parallelized while retaining their performance. A key baseband algorithm, digital predistortion using NN models for PA linearization, will be adapted to the parallel Walsh architecture. A straighforward parallelization of the state-of-the-art NN archi tecture is extended with a cross-domain Knowledge Distillation pre-training method to achieve linearization performance on par with the quadrature implementation. This result paves the way for the entire baseband processing chain to be adapted into ultra high bandwidth, low-power Walsh transceivers. Index Terms—digital predistortion (DPD), power amplifier(PA), time-delay neural network (TDNN), Walsh-Hadamard transform.