On the number of relays for orthogonalize-and-forward relaying

Relaying can significantly improve spectral efficiency and extend coverage of two-hop wireless communications between two end nodes. To support the relaying transmission between multiple end nodes, technologies like orthogonalize-and forward (OF) Relaying are proposed, which can also achieve interference-free communications between end nodes. However, this scheme requires a large number of relays. Therefore, in this paper, we investigate three modified OF Relaying schemes with fewer relays and derived their transmission rate respectively. They are fair OF Relaying with insufficient relays, OF Relaying with Pre-coding and Group Division OF Relaying. The numerical results show that these schemes can reduce the number of relays. Furthermore, OF Relaying with pre-coding can also achieve ideal transmission rate.