Link scanning method for cascaded remote control units, and remote electrical tilt antenna system

A remote electrical tilt antenna system, comprising cascaded remote control units RCUs communicating with a center control unit CCU;

• wherein
• the cascaded RCUs are configured to receive a link scanning message sent by the CCU, and among the cascaded RCUs, each of the RCUs, except an end RCU, sends the link scanning message to an RCU in the next cascaded RCU through a remote end serial communication bus;
• after receiving the link scanning message, each of the cascaded RCUs generates a link scanning response message, each of the RCUs, except an RCU directly communicating with the CCU, sends the link scanning response message to an RCU in the preceding cascaded RCU and reports the link scanning response message to the CCU cascaded RCU by cascaded RCU, and the RCU, directly communicating with the CCU, directly sends the link scanning message to the CCU;
• and
• among the cascaded RCUs, the time when each of the RCUs except the end RCU sends the link scanning message to the RCU in the next cascaded RCU is the time when each of the RCUs receives the link scanning message, plus a preset time delay;
• or, the time when each of the RCUs, except the end RCU and the RCU directly communicating with the CCU, sends the link scanning response message received from the RCU in the next cascaded RCU to the RCU in the preceding cascaded RCU is the time when each of the RCUs receives the link scanning response message sent by the RCU in the next cascaded RCU, plus a preset time delay;
• the time when the RCU directly communicating with the CCU sends the link scanning response message received from the RCU in the next cascaded RCU to the CCU is the time when the RCU receives the link scanning response message sent by the RCU in the next cascaded RCU, plus a preset time delay.