Multicarrier Spread Spectrum Communications with Noncontiguous Subcarrier Bands for HF Skywave Links

TL;DR

This paper introduces a multicarrier spread-spectrum waveform with noncontiguous subcarriers for HF skywave links, enhancing robustness and spectral efficiency in congested and harsh channel conditions.

Contribution

It proposes a novel filter-bank based multicarrier waveform with noncontiguous subcarriers and a modified receiver structure for improved HF communication performance.

Findings

Demonstrates robustness of the noncontiguous waveform in harsh HF channels.

Shows improved spectral efficiency in congested environments.

Validates performance through simulated and over-the-air experiments.

Abstract

Growing traffic over the high-frequency (HF) band poses significant challenges to establishing robust communication links. While existing spread-spectrum HF transceivers are, to some degree, robust against harsh HF channel conditions, their performance significantly degrades in the presence of strong co-channel interference. To improve performance in congested channel conditions, we propose a filter-bank based multicarrier spread-spectrum waveform with noncontiguous subcarrier bands. The use of noncontiguous subcarriers allows the system to at once leverage the robustness of a wideband system while retaining the frequency agility of a narrowband system. In this study, we explore differences between contiguous and noncontiguous systems by considering their respective peak-to-average power ratios (PAPRs) and matched-filter responses. Additionally, we develop a modified filter-bank receiver structure to facilitate both efficient signal processing and noncontiguous channel estimation. We conclude by presenting simulated and over-the-air results of the noncontiguous waveform, demonstrating both its robustness in harsh HF channels and its enhanced performance in congested spectral conditions.