Towards a low-complexity dynamic decode-and-forward relaying protocol

We first provide an overview of the dynamic decode-and-forward (DDF) relaying protocol, which is a recently proposed technique for cooperative wireless communications. DDF is based on the idea that each relay in the system should listen to the transmission from other active nodes till it receives enough information to decode, and retransmit only then. It has been proven to outperform any amplify and forward (AF) protocol in terms of diversity-multiplexing gain tradeoff (DMT). However, this protocol is quite complex and providing a simple implementation for the case of multiple relays is still an open problem. We then discuss our recently proposed technique to implement DDF with distributed rotations. In addition to being one of the first implementations of the DDF protocol proposed for any number of relays, this technique allows to exploit cooperative diversity without inducing the high decoding complexity of a space-time code. The analysis of outage probabilities for different number of relays and rotations shows that the performance of this technique is close to optimal. Moreover, a lower-bound on the DMT is provided in the case of a single relay and two rotations. This lower-bound reaches the optimal DDF's DMT when the frame-length grows to infinity, which shows that even a small number of rotations is enough to obtain good performance.