Using Distributed Rotations for a Low-Complexity Dynamic   Decode-and-Forward Relay Protocol
  In this paper, we propose to implement the dynamic decode-and-forward (DDF) protocol with distributed rotations. In addition to being the first minimum-delay implementation 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 diversity-multiplexing gain tradeoff (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. 
Charlotte Hucher and Parastoo Sadeghi
cs.IT math.IT