Transmitting system and method of processing digital broadcast signal in transmitting system, receiving system and method of receiving digital broadcast signal in receiving system

An apparatus for transmitting a broadcast signal, the apparatus comprising:

• an encoder configured to encode mobile data for forward error correction (FEC) to build RS (Reed-Solomon) frames depending on an RS frame mode, wherein the RS frames include the mobile data belonging to ensembles, each ensemble being a collection of services providing same quality of service;
• a signaling encoder configured to encode signaling data including binding information between the ensembles and the services;
• a data formatter configured to form data groups including the encoded mobile data and the encoded signaling data;
• a packet formatter configured to form mobile data packets including data in the data groups, wherein the mobile data packets in the data groups include a specific number of mobile data packets and a scalable number of mobile data packets, wherein the scalable number is scalable up to 38;
• an interleaver configured to interleave data in the mobile data packets, wherein each of the data groups includes a plurality of regions, the plurality of regions including data blocks, wherein a first region includes central 4 data blocks in the data group, a second region includes 2 data blocks being concentric about the first region, a third region includes 2 data blocks being concentric about the first and second regions and a fourth region includes 2 data blocks being concentric about the first, second and third regions, and a fifth region includes the scalable number of mobile data packets;
• and
• a transmission unit configured to transmit the interleaved data in a transmission frame, wherein the signaling data includes an identifier indicating a number of ensembles transmitted through a data group having the fifth region,
• wherein the ensembles include a primary ensemble of the mobile data and a secondary ensemble of the mobile data, wherein the first and second regions include the primary ensemble of the mobile data, a third, fourth and fifth regions include the secondary ensemble of the mobile data.