  The assumption of nodes in a cooperative communication relay network
operating in synchronous fashion is often unrealistic. In the present paper, we
consider two different models of asynchronous operation in
cooperative-diversity networks experiencing slow fading and examine the
corresponding diversity-multiplexing tradeoffs (DMT). For both models, we
propose protocols and distributed space-time codes that asymptotically achieve
the transmit diversity bound for all multiplexing gains and for any number of
relays.
