A wireless communication system base station, and a remote radio head (RRH) and a computer-implemented synchronization method for the wireless communication system base station. The RRH is communicably coupled to a baseband unit (BBU) of the wireless communication system base station through a network, and the BBU processes and transmits downlink data to the RRH. The RRH includes: a time-delay measurement unit for measuring a time-delay for the downlink data to arrive at the RRH from the BBU; and a time-delay notification unit for notifying from the RRH to the BBU of time-delay data on the time-delay measured by the time-delay measurement unit, wherein the time-delay data is used to advance the starting time for the BBU to process and transmit the downlink data by an amount of time obtained based on the time-delay data.