Delay-tolerant distributed-TAST codes for cooperative diversity

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 (e.g.,in cases of broadcast to dispersed recipients or in networks without a shared, high-quality timing reference). Recent work by Xia et al. and Hammons et al. have investigated the design of distributed space-time codes that are delay tolerant, in the sense that full spatial diversity is achieved regardless of timing offsets. In general, the previously known space-time block codes belonging to the class of C-linear codes, however, which are important because they achieve full spatial diversity and admit near-optimal lattice decoding algorithms, are not delay tolerant. in this paper, we present a new family of such codes that are. fully delay tolerant. The new codes generalize the threaded algebraic space-time (TAST) codes introduced by El Gamal and Damen. Like their brethren, the new Distributed-TAST codes are effective And flexible, enabling use of different signaling constellations, transmission rates, numbers of transmit and receive antennas, and decoders of varying levels of complexity.