Downlink Precoder Design for Coordinated Regenerative Multi-User Relaying

Relays are used in the current wireless standards to enhance the cell throughput and coverage. In this paper, we evaluate the system performance by considering the duplexing loss with over-the-air transmission for relay with decode-and-forward as the relaying protocol. The overhead involved in providing the relay with the data prior to the transmission is often neglected. We demonstrate that the impact of relays can be even detrimental if the in-band signaling needs are not properly accounted for. Both precoder design and user allocation between the base station and the relay are considered. The precoder design objectives are transmit power minimization and throughput maximization each of which two different precoding approaches are considered. Zero-forcing precoder design is proposed to achieve reduced computation complexity and low signaling overhead. For higher efficiency and performance, we provide coordinated solutions, which allow more flexible interference control. We also consider user allocation by providing heuristic allocation methods.