Space-Time Block Codes for Quasi-synchronous Cooperative Diversity

Li and Xia have recently investigated the design of space-time codes that achieve full spatial diversity for quasi-synchronous cooperative communications. They show that certain of the binary space-time trellis codes derived from the Hammons-El Gamal stacking construction are delay tolerant and can be used in the multilevel code constructions by Lu and Kumar to produce delay tolerant space-time codes for PSK and QAM signaling. In prior work, the first author has developed generalizations of the Lu-Kumar construction for more general AM-PSK constellations that also preserve the delay tolerance of the underlying constituent codes and exhibited a new construction of short block codes that achieve significant levels of delay tolerance. Use of space-time block codes (STBC) of short length in the Li-Xia transmission framework results in a significant loss of rate. We present generalizations of that framework that make short STBC a potentially attractive option for quasi-synchronous cooperative diversity