  Design criteria and full-diversity Distributed Space Time Codes (DSTCs) for
the two phase transmission based cooperative diversity protocol of Jing-Hassibi
and the Generalized Nonorthogonal Amplify and Forward (GNAF) protocol are
reported, when the relay nodes are assumed to have knowledge of the phase
component of the source to relay channel gains. It is shown that this under
this partial channel state information (CSI), several well known space time
codes for the colocated MIMO (Multiple Input Multiple Output) channel become
amenable for use as DSTCs. In particular, the well known complex orthogonal
designs, generalized coordinate interleaved orthogonal designs (GCIODs) and
unitary weight single symbol decodable (UW-SSD) codes are shown to satisfy the
required design constraints for DSTCs. Exploiting the relaxed code design
constraints, we propose DSTCs obtained from Clifford Algebras which have low ML
decoding complexity.
