On Delay-Tolerant Distributed Space-Time Codes

In cooperative networks using a decode-and-forward strategy, the multiple relays effectively transmit a distributed space-time code, the performance of which can be severely degraded when timing synchronization among the relays is not assured. Recent work by Xia et al., Hammons et al., and Damen et al. has investigated the design of distributed space-time codes that are delay tolerant, in the sense that full spatial diversity is achieved regardless of relative timing offsets. In this paper, we survey these contributions.