On the Diversity Gain in Dynamic Decode-and-Forward Channels with Imperfect CSIT

We investigate the impact of imperfect channel state information at the transmitter (CSIT) on the diversity gain in dynamic decode-and-forward (DF) relaying channels. A diversity and multiplexing tradeoff analysis is presented, which reveals that power control based on imperfect CSIT significantly improves the achievable diversity gain. It is found that if the multiplexing gain is higher than 1/2, the achievable diversity gain only depends on the CSIT of the source-destination (S-D) link and the relay-destination (R-D) link; otherwise the CSIT of the source-relay (S-R) link might also contribute. It is also found that the CSIT of the R-D link does not contribute to the overall diversity gain if the source has no CSIT. The presented results show that dynamic DF relaying supports not only a higher multiplexing gain but also a higher diversity gain than conventional DF relaying protocols.