  Explicit codes are constructed that achieve the diversity-multiplexing gain
tradeoff of the cooperative-relay channel under the dynamic decode-and-forward
protocol for any network size and for all numbers of transmit and receive
antennas at the relays.
  A particularly simple code construction that makes use of the Alamouti code
as a basic building block is provided for the single relay case.
  Along the way, we prove that space-time codes previously constructed in the
literature for the block-fading and parallel channels are approximately
universal, i.e., they achieve the DMT for any fading distribution. It is shown
how approximate universality of these codes leads to the first DMT-optimum code
construction for the general, MIMO-OFDM channel.
