Recovering multiplexing loss through concurrent Decode-and-Forward (DF) relaying

In this paper, we develop a novel digital cooperative diversity transmission protocol for a two-source scenario by combining the two sources' two classic decode-and-forward (DF) relaying steps and using 2L + 1 time slots to transmit L codewords from each source. Assuming the relays can perfectly decode their associated source messages, we give an information-theoretic average achievable capacity region for this transmission scheme. Through diversity-multiplexing tradeoff analysis, we show that our so called concurrent DF relaying protocol can effectively recover the multiplexing loss induced by the half-duplex operation in the relays, while still obtaining some diversity gain. Numerical results reveal our scheme offers significant performance advantages over the classic DF relaying protocols, especially for high signal-to-noise ratio (SNR) and large frame length L regime.