Distributed Space-Time Trellis Code for Asynchronous MIMO Relays over Frequency-Selective Channels

In most cooperative communications works, perfect synchronization among relay nodes is assumed. However, this assumption is not realistic due to the distributed nature of each relay node. In this paper, we consider the downlink in a MIMO cellular network utilizing two-hop transmission protocols with fixed infrastructure relay stations (RS) to enhance coverage and data rates. We propose a family of distributed space-time trellis code (DSTTC) for two RSs without the synchronization assumption. It is shown that the construction of the proposed DSTTCs is equivalent to using the generator matrices that have full row rank regardless of sub-matrices shifting problem, where a sub-matrix corresponds to the generator matrix of a RS under frequency-selective channels. Finally, various numerical examples are provided to verify the analytical studies.