Distributed space-time codes: relays delays and code word overlays

We consider decode and forward strategy in the relay channel, where in the first time interval the source communicates its message to its neighboring relays, and in the second time interval, the relays form a distributed space-time code and forward the source message to the destination. In particular, we tackle the problem of overlapping code words in asynchronous distributed coded transmission. We show that the class of delay-tolerant TAST codes [1], with a small modification, can achieve full spatial diversity even when considering overlapping code words from the different asynchronous relays. Simulation results confirm our analysis.