A monitoring device for a distributed antenna system including at least two node units communicatively coupled to each other transmits, to at least one target node unit among the node units, a data dump command for a first target signal passing through a first signal path in the target node unit. The monitoring device receives, from the target node unit, response data corresponding to the data dump command. The monitoring device generates first quality information indicative of the quality of the first target signal by using the response data.