  Previous work on relay networks has concentrated primarily on the diversity
benefits of such techniques. This paper explores the possibility of also
obtaining multiplexing gain in a relay network, while retaining diversity gain.
Specifically, consider a network in which a single source node is equipped with
one antenna and a destination is equipped with two antennas. It is shown that,
in certain scenarios, by adding a relay with two antennas and using a
successive relaying protocol, the diversity multiplexing tradeoff performance
of the network can be lower bounded by that of a 2 by 2 MIMO channel, when the
decode-and-forward protocol is applied at the relay. A distributed D-BLAST
architecture is developed, in which parallel channel coding is applied to
achieve this tradeoff. A space-time coding strategy, which can bring a maximal
multiplexing gain of more than one, is also derived for this scenario. As will
be shown, while this space-time coding strategy exploits maximal diversity for
a small multiplexing gain, the proposed successive relaying scheme offers a
significant performance advantage for higher data rate transmission. In
addition to the specific results shown here, these ideas open a new direction
for exploiting the benefits of wireless relay networks.
