Diversity–Multiplexing Tradeoff Analysis of AF Two-Way Relaying Channel With Hybrid ARQ Over Rayleigh Fading Channels

This paper investigates the diversity-multiplexing tradeoff (DMT) performance of the two-way relaying channel (TWRC) with hybrid automatic repeat request (HARQ) in Rayleigh fading channels. We focus on the amplify-and-forward (AF) mode and the scenario without a direct link. Two implementation schemes for the TWRC with retransmission are presented. In one scheme (Scheme I), the source does not immediately transmit new message in the next round after its message is decoded successfully. It waits until the message of the other source is also successfully decoded via retransmission, and then, the two sources transmit new message simultaneously. In the other scheme (Scheme II), the source immediately transmits new message after its message is successfully decoded, regardless of the transmission state of the other source. To calculate the DMT of Scheme I, we first propose both lower and upper bounds on its outage probability. The exact DMT is then derived in closed form based on these bounds. Furthermore, the DMT of Scheme II is obtained. The DMT results reveal that both schemes achieve the same DMT performance, and reliability (i.e., diversity) could be enhanced by leveraging on transmission delay (i.e., retransmission).