A distributed antenna system connected to a first base station and a second base station, which provide a duplication-based service, and configured to support high availability, the distributed antenna system comprising: a first headend unit configured to receive a mobile communication signal from the first base station, generate and transmit a downlink frame, and configure and manage topology information of the distributed antenna system; a second headend unit configured to receive a mobile communication signal from the second base station, generate and transmit a downlink frame, and configure and manage topology information of the distributed antenna system; and a first branch group and a second branch group each comprising a hub unit (210, 310) branched from and connected to the first headend unit and the second headend unit and configured to distribute a downlink received from the first headend unit or the second headend unit to a plurality of remote units (212, 214, 312, 314) connected to the hub unit (210, 310) as a sub-node and configured to restore a mobile communication signal from the distributed downlink frame and transmit the mobile communication signal in a wireless manner, wherein one of the first headend unit or the second headend unit is in an active state (100-A), the other headend unit is in a standby state (100-S), and each headend unit (100-1, 100-2) adds a state bit indicating a duplication state to a control field of the downlink frame and then transmits the downlink frame, and the hub unit (210, 310) of the first branch group or the second branch group that has received the downlink frame delivers only a frame received from an active headend unit (100-A) to the plurality of remote units (212, 214, 312, 314) connected to the hub unit (210, 310) as a sub-node. a first headend unit configured to receive a mobile communication signal from the first base station, generate and transmit a downlink frame, and configure and manage topology information of the distributed antenna system; a second headend unit configured to receive a mobile communication signal from the second base station, generate and transmit a downlink frame, and configure and manage topology information of the distributed antenna system; and a first branch group and a second branch group each comprising a hub unit (210, 310) branched from and connected to the first headend unit and the second headend unit and configured to distribute a downlink received from the first headend unit or the second headend unit to a plurality of remote units (212, 214, 312, 314) connected to the hub unit (210, 310) as a sub-node and configured to restore a mobile communication signal from the distributed downlink frame and transmit the mobile communication signal in a wireless manner, wherein one of the first headend unit or the second headend unit is in an active state (100-A), the other headend unit is in a standby state (100-S), and each headend unit (100-1, 100-2) adds a state bit indicating a duplication state to a control field of the downlink frame and then transmits the downlink frame, and the hub unit (210, 310) of the first branch group or the second branch group that has received the downlink frame delivers only a frame received from an active headend unit (100-A) to the plurality of remote units (212, 214, 312, 314) connected to the hub unit (210, 310) as a sub-node. one of the first headend unit or the second headend unit is in an active state (100-A), the other headend unit is in a standby state (100-S), and each headend unit (100-1, 100-2) adds a state bit indicating a duplication state to a control field of the downlink frame and then transmits the downlink frame, and the hub unit (210, 310) of the first branch group or the second branch group that has received the downlink frame delivers only a frame received from an active headend unit (100-A) to the plurality of remote units (212, 214, 312, 314) connected to the hub unit (210, 310) as a sub-node.