Base station system, wireless control unit, wireless communication method, and recording medium

A wireless control unit of a base station, the wireless control unit being connected, via communication cables, to a plurality of analog sections each of which outputs a downlink signal by radio waves through an antenna and communicating with the plurality of analog sections by a wavelength division multiplexing (WDM) scheme, the wireless control unit comprising:

• a memory configured to store instructions;
• and
• at least one processor which executes the instructions to
• transmit to the plurality of analog sections an observation signal for observing delay times in synchronization with an internal clock serving as a reference clock, the observation signal having a first wavelength,
• for each of the plurality of analog sections, count the number of clocks generated from when the observation signal is transmitted to when the observation signal is received, and calculate a path delay based on the number of clocks counted, and
• transmit a downlink signal at a timing calculated for each of the plurality of analog sections according to the path delay, to a specific one of the plurality of analog sections which corresponds to the timing, the downlink signal having a second wavelength different from the first wavelength.

A wireless communication method carried out by a base station system which includes a wireless control unit and a plurality of analog sections connected to the wireless control unit via communication cables, the wireless communication method comprising:

• the wireless control unit transmitting to the plurality of analog sections a control signal for performing control so as to cause the plurality of analog sections to transition to a loopback mode;
• the wireless control unit transmitting to the plurality of analog sections an observation signal for observing delay times in synchronization with an internal clock serving as a reference clock;
• the wireless control unit counting, for each of the plurality of analog sections, the number of clocks generated from the observation signal is when transmitted to when the observation signal is received, and calculating a path delay based on the number of clocks counted;
• the wireless control unit transmitting to the plurality of analog sections a control signal for canceling the loopback mode of the plurality of analog sections;
• the wireless control unit transmitting a downlink signal at a timing calculated for each of the plurality of analog sections according to the path delay, to a specific one of the plurality of analog sections which corresponds to the timing;
• the plurality of analog sections transitioning to the loopback mode in a case of receiving the control signal for causing a transition to the loopback mode;
• the plurality of analog sections reproducing, in the loopback mode, a transmission signal from a reception signal received from the wireless control unit, to transmit the transmission signal to the wireless control unit;
• the plurality of analog sections transitioning to a communication mode in a case of receiving a control signal for canceling the loopback mode;
• and
• the plurality of analog sections outputting, in the communication mode, the downlink signal received from the wireless control unit, by radio waves through an antenna.