On the Performance of Millimeter Wave-based RF-FSO Links with HARQ Feedback

TL;DR

This paper analyzes the performance of millimeter wave RF and FSO hybrid links with HARQ, deriving formulas for key metrics and showing how HARQ improves reliability and efficiency under various conditions.

Contribution

It provides closed-form expressions for RF-FSO link performance considering mmwave and pointing errors, and evaluates HARQ's effectiveness in enhancing reliability.

Findings

HARQ improves outage probability and energy efficiency.

Performance depends on power amplifier efficiency and pointing errors.

HARQ compensates hardware impairments in RF-FSO links.

Abstract

This paper studies the performance of hybrid radio-frequency (RF) and free-space optical (FSO) links in the cases with and without hybrid automatic repeat request (HARQ). Considering millimeter wave (mmwave) characteristics in the RF link and pointing errors in the FSO link, we derive closed-form expressions for the message decoding probabilities as well as the throughput and the outage probability of the RF-FSO setups. We also evaluate the effect of various parameters such as power amplifiers efficiency, different transmission techniques in the FSO link, pointing errors in the FSO link as well as different coherence times/symbol rates of the RF and the FSO links on the throughput and outage probability. The results show the efficiency of the RF-FSO links in different conditions. Moreover, the HARQ can effectively improve the outage probability/energy efficiency, and compensate the effect of hardware impairments in RF-FSO links.