Outage Performance of Cross-Packet HARQ

TL;DR

This paper investigates the outage performance of cross-packet HARQ, deriving exact and bound outage expressions, and demonstrates that XP-HARQ can achieve full time diversity in high SNR regimes.

Contribution

It provides the first exact outage expression for XP-HARQ with two transmissions and tight bounds for more, along with asymptotic analysis showing full diversity.

Findings

Exact outage expression for two transmissions

Tight outage bounds for more than two transmissions

Full time diversity achieved at high SNR

Abstract

As opposed to hybrid automatic repeat request with incremental redundancy (HARQ-IR) that all the resources are occupied to resend the redundant information, cross-packet HARQ (XP-HARQ) allows the introduction of new information into retransmissions to substantially exploit the remaining resources. This letter provides a profound investigation into the outage performance of XP-HARQ. In particular, the exact outage expression of XP-HARQ is derived if the maximum number of transmissions is two, and tight outage bounds are obtained for more than two transmissions. Moreover, the asymptotic outage analysis of XP-HARQ in the high signal-to-noise ratio (SNR) regime is carried out not only to simplify the outage expression, but also to show that full time diversity is achievable by XP-HARQ. The simulation results are eventually presented for verifications.