Overcoming Half-Duplex Loss in Multi-Relay Networks: Multiple Relay Coded Cooperation for Optimal DMT

This paper studies diversity-multiplexing tradeoff (DMT) of decode-and-forward (DF)-based half-duplex relay networks without a direct path from source to destination. We propose a new multiple relay coded cooperation (MRCC) protocol to overcome the half-duplex loss in DF relay networks and show that the proposed MRCC protocol achieves the MISO/SIMO DMT upper bound as the number of assisting relays increases. The loss of multiplexing gain from the half-duplex constraint is recovered by coded cooperation and successive cancellation. Despite its notable gain in terms of DMT, the proposed MRCC protocol requires only limited feedback information/signaling for relay and operation mode selection. We also derive the achievable DMT of the proposed MRCC protocol when each node has multiple antennas. It is shown that the proposed MRCC protocol achieves K times diversity gain of the point-to-point N × N MIMO case. Compared with existing protocols, the MRCC protocol shows much higher diversity gain for almost all multiplexing gains. Furthermore, our numerical results verify that the proposed MRCC protocol outperforms existing protocols in terms of outage probability for the environments of practical interest.