MIMO ARQ with Multibit Feedback: Outage Analysis
This paper studies the asymptotic outage performance of Incremental Redundancy Automatic-Repeat-reQuest (INR-ARQ) transmission over Multiple-Input Multiple-Output (MIMO) block-fading channels with discrete input constellations. The authors 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. The optimal SNR-exponent and outage diversity of INR-ARQ transmission over the MIMO block-fading channel are then analyzed. They show that a significant gain in outage diversity is obtained by providing more than one bit feedback at each ARQ round.