# Orthogonal Transform Multiplexing with Memoryless Nonlinearity: a Possible Alternative to Traditional Coded-Modulation Schemes

## TL;DR

This paper introduces a novel joint coding-modulation scheme using orthogonal transforms and memoryless nonlinearity, achieving near-capacity performance and reduced PAPR, offering a promising alternative to traditional coded modulation methods.

## Contribution

It presents a new modulation technique combining orthogonal transforms with nonlinearity, demonstrating capacity-approaching performance and potential integration with OFDM systems.

## Key findings

- Performance comparable to state-of-the-art coded schemes
- Approaches channel capacity with simple construction
- Reduces peak-to-average power ratio in OFDM systems

## Abstract

In this paper, we propose a novel joint coding-modulation technique based on serial concatenation of orthogonal linear transform, such as discrete Fourier transform (DFT) or Walsh-Hadamard transform (WHT), with memoryless nonlinearity. We demonstrate that such a simple signal construction may exhibit properties of a random code ensemble, as a result approaching channel capacity. Our computer simulations confirm that if the decoder relies on a modified approximate message passing algorithm, the proposed modulation technique exhibits performance on par with state-of-the-art coded modulation schemes that use capacity-approaching component codes. The proposed modulation scheme could be used directly or as a pre-coder for a conventional orthogonal frequency division multiplexing (OFDM) transmitter, resulting in a system possessing all benefits of OFDM along with reduced peak-to-average power ratio (PAPR).