Turbo packet combining for broadband MIMO relay communication

Abstract

In this paper, we provide a survey of cooperative automatic repeat request (ARQ) protocols for multi-relay systems operating over multiple-input-multiple-output (MIMO) broadband channels. We study three main operating modes: amplify-and-forward (AF), decode-and-forward (DF), and positive/negative acknowledgment (ACK/NACK)-aided DF. We describe efficient minimum mean square error (MMSE) frequency domain equalization (FDE) iterative turbo packet combining techniques for cooperative ARQ, and show that they outperform conventional log-likelihood ratio (LLR)-based turbo combining.