Outage Probability Analysis of HARQ-Aided Terahertz Communications

TL;DR

This paper analyzes the outage probability of HARQ-assisted terahertz communications, considering fading and misalignment, and derives closed-form expressions showing HARQ-CC outperforms Type-I HARQ in reliability.

Contribution

It provides the first closed-form outage probability analysis for HARQ-aided THz communications considering realistic impairments, highlighting the benefits of HARQ schemes.

Findings

HARQ schemes significantly improve reliability in THz communications.

HARQ-CC outperforms Type-I HARQ due to higher diversity gain.

Full time diversity can be achieved with HARQ schemes.

Abstract

Although terahertz (THz) communications can provide mobile broadband services, it usually has a large path loss and is vulnerable to antenna misalignment. This significantly degrades the reception reliability. To address this issue, the hybrid automatic repeat request (HARQ) is proposed to further enhance the reliability of THz communications. This paper provides an in-depth investigation on the outage performance of two different types of HARQ-aided THz communications, including Type-I HARQ and HARQ with chase combining (HARQ-CC). Moreover, the effects of both fading and stochastic antenna misalignment are considered in this paper. The exact outage probabilities of HARQ-aided THz communications are derived in closed-form, with which the asymptotic outage analysis is enabled to explore helpful insights. In particular, it is revealed that full time diversity can be achieved by using HARQ assisted schemes. Besides, the HARQ-CC-aided scheme performs better than the Type-I HARQ-aided one due to its high diversity combining gain. The analytical results are eventually validated via Monte-Carlo simulations.