Distributed Space-Time Code for Asynchronous Two-way Wireless Relay Networks under Frequency-Selective Channels

In this paper, we consider asynchronous two-way wireless relay networks with amplify-and-forward protocol (AF-TWRN), where the distributed space-time code (DSTC) is utilized without synchronization among relays to assist the communication between two terminals. We analyze the pairwise error probability (PEP) behavior of DSTC for AF-TWRN under frequency-selective channels. From our analysis, it is seen that of the paths from one terminal to relays and from relays to another terminal, those with smaller diversity order result in an overall system performance bottleneck. Considering both the timing errors among relays and the multipath fading, we then propose a family of distributed convolutional space-time codes (DCSTC) for AF-TWRN such that the full diversity order can be achieved. Finally, various numerical examples are provided to corroborate the analytical studies.