Distributive High-Rate Full-Diversity Space-Frequency Codes for Asynchronous Cooperative Communications

In user cooperative communications, relay nodes are usually asynchronous. By realizing that the processing in the frequency domain is insensitive to the errors in the time domain, Mei et. al., (2005) recently applied the OFDM technique to achieve the full cooperative diversity for asynchronous cooperative communications, where orthogonal space-time block codes, Alamouti code in particular, were used for relay nodes and the channels from nodes to nodes are assumed flat fading. In this paper, we also consider asynchronous cooperative communications, but the channels from nodes to nodes are assumed to be frequency-selective fading. We use high rate space-frequency codes to encode the correctly detected information symbols across some subcarriers at relay nodes to achieve both full cooperative diversity and full multipath diversity for asynchronous communications, which, we show, holds if the recent high rate space-frequency codes constructed in W. Zhang et al., (2005) are used