A transmitting system and a method of transmitting digital broadcast signal are disclosed. The method of transmitting digital broadcasting signal in a transmitter includes encoding mobile data for forward error correction to build RS frames, wherein the RS frames includes the mobile data belonging to ensembles, each ensemble being a collection of services providing same quality of service, encoding signaling data including binding information between the ensembles and the services, forming data groups, forming mobile data packets including data in the data groups, wherein each mobile data packet include an additional mobile data packets, interleaving data in the mobile data packets, wherein a fifth region of each data group includes the additional mobile data packets, transmitting the interleaved data, wherein the signaling data includes an identifier indicating a number of ensembles transmitted through a data group having the fifth region.