Abstract: A precoding method in a multi-antenna system includes the following steps. A reference device transmits a first reference signal to base station antennas. A base station calculates uplink channel information and transmits it to a coordination server. The base station transmits a second reference signal to the reference device. The reference device calculates downlink channel information and transmits it to the coordination server.

Abstract: A communication system, a coordinator and an interference controlling method are provided. The communication system includes at least two user equipments, at least two remote radio heads (RRHs) and the coordinator. Each of the RRHs electrically connects a plurality of antennas. The coordinator includes a scanning unit, a storing unit and a scheduling unit. The scanning unit operates the measurement of a performance of each of the antennas used for each of the user equipments by antenna sweeping. The RRHs are classified into at least one group. The scheduling unit schedules the communication of the user equipments. At least some of the user equipments using the same one of the at least one group are scheduled in different time slots to prevent from interference.

Abstract: A precoding method in a multi-antenna system includes the following steps. A reference device transmits a first reference signal to base station antennas. A base station calculates uplink channel information and transmits it to a coordination server. The base station transmits a second reference signal to the reference device. The reference device calculates downlink channel information and transmits it to the coordination server.