Outage Effective Capacity of Buffer-Aided Diamond Relay Systems Using HARQ with Incremental Redundancy

TL;DR

This paper analyzes the outage effective capacity of buffer-aided diamond relay systems employing HARQ-IR under delay constraints, demonstrating that HARQ-IR can outperform DF protocols without CSI in certain conditions.

Contribution

It introduces the concept of outage effective capacity for buffer-aided diamond relay systems using HARQ-IR under delay constraints, providing new insights into system performance.

Findings

HARQ-IR achieves higher outage effective capacity than DF with perfect CSI under certain conditions.

Performance gains are notable at lower relay SNR levels and stricter delay constraints.

The study quantifies the maximum sustainable data rate under outage and delay limitations.

Abstract

In this paper, transmission over buffer-aided diamond relay systems under statistical quality of service (QoS) constraints is studied. The statistical QoS constraints are imposed as limitations on delay violation probabilities. In the absence of channel state information (CSI) at the transmitter, truncated hybrid automatic repeat request-incremental redundancy (HARQ-IR) is incorporated to make better use of the wireless channel and the resources for each communication link. The packets that cannot be successfully received upon the maximum number of transmissions will be removed from buffer, i.e., outage occurs. The \emph{outage effective capacity} of a communication link is defined as the maximum constant arrival rate to the source that can be supported by the \emph{goodput} departure processes, i.e., the departure that can be successfully received by the receiver. Then, the outage effective capacity for the buffer-aided diamond relay system is obtained for HARQ-IR incorporated transmission strategy under the \emph{end-to-end} delay constraints. In comparison with the DF protocol with perfect CSI at the transmitters, it is shown that HARQ-IR can achieve superior performance when the SNR levels at the relay are not so large or when the delay constraints are stringent.