The present invention relates to a wireless communication system and, particularly, to a method and a device therefor, the method comprising the steps of: configuring a cell group including multiple Ucells; identifying subframe configuration information on a particular cell within the cell group; and configuring subframe transmission directions of cells within the cell group so as to be the same at the same time point, on the basis of the subframe configuration information on the particular cell, wherein the particular cell is one Ucell among the multiple Ucells within the cell group when the cell group includes only Ucells, and the particular cell is an Lcell when the cell group includes the Lcell.