MIMO ARQ with Multi-bit Feedback: Outage Analysis

TL;DR

This paper analyzes the outage performance of MIMO INR-ARQ systems with multi-bit feedback, demonstrating significant diversity gains and proposing a suboptimal feedback scheme that achieves optimal outage diversity with minimal overhead.

Contribution

It provides the first analysis of outage diversity for MIMO INR-ARQ with multi-bit feedback and introduces a practical feedback and power adaptation rule.

Findings

Multi-bit feedback significantly improves outage diversity.

Random coding with discrete constellations achieves the Singleton bound.

Proposed suboptimal feedback scheme attains optimal outage diversity.

Abstract

We study the asymptotic outage performance of incremental redundancy automatic repeat request (INR-ARQ) transmission over the multiple-input multiple-output (MIMO) block-fading channels with discrete input constellations. We first show that transmission with random codes using a discrete signal constellation across all transmit antennas achieves the optimal outage diversity given by the Singleton bound. We then analyze the optimal SNR-exponent and outage diversity of INR-ARQ transmission over the MIMO block-fading channel. We show that a significant gain in outage diversity is obtained by providing more than one bit feedback at each ARQ round. Thus, the outage performance of INR-ARQ transmission can be remarkably improved with minimal additional overhead. A suboptimal feedback and power adaptation rule, which achieves the optimal outage diversity, is proposed for MIMO INR-ARQ, demonstrating the benefits provided by multi-bit feedback.