Distributed space-time block coding in multi-way amplify-and-forward relaying networks

The multi-way relaying networks (MWRNs) are investigated, in which multiple users exchange their information with the help of a relay node. We constraint that all users form a single group to share information with each other by using half-duplex communication mode. For such networks, an universal linear dispersion space-time block code (STBC) is introduced based on amplify-and-forward (AF) relaying protocol. Furthermore, a lower bound of pairwise error probability (PEP) of maximum likelihood (ML) detector is first derived, which reveals that the best-achievable diversity gain function is determined by the signal to noise ratio ρ, the user number K and the antenna number of the relay M, i.e., In ρ/ρM(K-1). Specifically, we design a distributed quasi-orthogonal STBC for the MWRN with K = 3 and demonstrate that the design can obtain a larger diversity gain than those in the one-way and two-way relaying networks by Monte Carlo simulations.