Outage Performance Analysis of Type-I HARQ Aided V2V Communications

TL;DR

This paper analyzes the outage performance of Type-I HARQ aided MIMO V2V communications in dense urban environments, deriving closed-form outage probability and providing insights into diversity orders and rate effects.

Contribution

It introduces a closed-form outage probability analysis for Type-I HARQ aided MIMO V2V systems under keyhole fading, revealing diversity limits and rate dependencies.

Findings

Full-time diversity order can be achieved.

Full spatial diversity order is not attainable due to keyhole effect.

Asymptotic outage probability increases monotonically with transmission rate.

Abstract

Vehicle-to-vehicle (V2V) communications under dense urban environments usually experience severe keyhole fading effect, especially for multi-input multi-output (MIMO) channels, which degrades the capacity and outage performance due to the rank deficiency. To avoid these, the integration of MIMO and Type-I hybrid automatic repeat request (HARQ) is proposed to assist V2V communications in this paper. By using the Meijer G-function, the outage probability of the proposed V2V communications system is derived in closed form. With the result, meaningful insights are gained by conducting the asymptotic outage analysis. Specifically, it is revealed that full-time diversity order can be achieved, while full spatial diversity order is unreachable as compared to Type-I HARQ aided MIMO systems without keyhole effect. Moreover, we prove that the asymptotic outage probability is a monotonically increasing and convex function of the transmission rate. Finally, the analytical results are validated through extensive numerical experiments.