The disclosed method of processing a digital broadcast signal comprises encoding signaling data for signaling of mobile service data, forming data groups, wherein the data groups include a first data group, a second data group and a third data group, and transmitting the digital broadcast signal including the data groups, wherein the signaling data includes first information indicating whether a segmented known data sequence of the second data group is concatenated to a segmented known data sequence of the first data group to form a known data sequence, and/or second information indicating whether a segmented known data sequence of the second data group is concatenated to a segmented known data sequence of the third data group to form a known data sequence.