Dynamic QMF for half-duplex relay networks

The value of relay nodes to enhance the error performance versus rate trade-off in wireless networks has been studied extensively. However, wireless nodes currently are constrained to only transmit or receive at a given frequency, i.e., half-duplex constraint. The diversity-multiplexing tradeoff (DMT) for half-duplex networks are less understood. In the special cases where the DMT is currently known, such as the relay channel and the line network, it is achieved by either dynamic decoding or a quantize-map-forward (QMF) strategy with a fixed half-duplex schedule. The main question we investigate in this paper is whether these two strategies are sufficient to achieve the DMT of half-duplex wireless networks or we need new strategies for general setups. We propose a generalization of the two existing schemes through a dynamic QMF strategy and show that in a parallel relay channel it outperforms both earlier schemes. We also establish the DMT for the relay channel with multiple relays and multiple antennas in some special cases.