On the Diversity-Multiplexing Tradeoff of an Improved Amplify-and-Forward Relaying Strategy

The diversity-multiplexing tradeoff (DMT) is one of the most important criteria to evaluate the performance of wireless relay networks. Previous work shows that, compared to decode-and-forward (DF) and estimate-and-forward (EF) relaying protocols, amplify-and-forward (AF) achieves the worst DMT and cannot reach the DMT upper bound. In this paper, we propose a new relaying protocol, called dynamic AF (DAF), which allows the relay to adapt the receiving and forwarding time durations to the channel conditions. We show that DAF achieves the DMT upper bound when the multiplexing gain r is between 0 and alpha, where 0 < alpha < 0.5 is a constant set according to the relaying channel conditions.