An Efficient Frequency Diversity Scheme for Ultra-Reliable Communications in Two-Path Fading Channels

TL;DR

This paper proposes a frequency diversity scheme using two frequencies to enhance ultra-reliability in two-path fading channels, optimizing frequency spacing to maximize worst-case receive power with limited transmitter knowledge.

Contribution

It introduces an optimized frequency spacing algorithm for two-frequency diversity in two-path fading, improving reliability without extensive channel information.

Findings

Significant reliability improvement over single frequency

Optimized frequency spacing maximizes worst-case receive power

Effective in UAV communication scenarios

Abstract

We consider a two-ray ground reflection scenario with unknown distance between transmitter and receiver. By utilizing two frequencies in parallel, we can mitigate possible destructive interference and ensure ultra-reliability with only very limited knowledge at the transmitter. In order to achieve this ultra-reliability, we optimize the frequency spacing such that the worst-case receive power is maximized. Additionally, we provide an algorithm to calculate the optimal frequency spacing. Besides the receive power, we also analyze the achievable rate and outage probability. It is shown that the frequency diversity scheme achieves a significant improvement in terms of reliability over using a single frequency. In particular, we demonstrate the effectiveness of the proposed approach by a numerical simulation of an unmanned aerial vehicle (UAV) flying above flat terrain.