Adaptive amplify-and-forward relaying for cellular downlink

This paper presents an adaptive amplify-and-forward (AF)-type relaying method appropriate for the cellular downlink. The proposed method adaptively selects active relay stations (RSs) based on the path loss between each set of user equipment (UE) and the base station (BS) and that between each RS in order to avoid unnecessary enhancement of inter-cell interference and bandwidth reduction due to transmission relay. Furthermore, to enhance the spectrum efficiency when relaying, the frequency used for the relay transmission from the RS to the cell-edge user is reused for the direct transmission from the BS to the cell-center user. Based on computer simulation, the system-level average throughput and cell-edge user throughput of the proposed method are compared to those for a case using no relaying and a conventional repeater. The simulation results show the effectiveness of the proposed method.