Methods and apparatus for transmitting and receiving broadcast signals are provided. The method for transmitting a broadcast signal includes encoding mobile data for forward error correction (FEC), encoding signaling data, forming data groups including the encoded mobile data and the encoded signaling data and transmitting a signal frame that includes the data groups.

A DTV transmitter includes a pre-processor pre-processing enhanced data, a data formatter generating enhanced data packets including the pre-processed enhanced data, and a multiplexer multiplexing the enhanced data packets with main data packets. The transmitter further includes an RS encoder RS-coding the multiplexed packets by adding systematic RS parity data to each main data packet and by adding non-systematic RS parity place holders to each enhanced data packet, and a data interleaver interleaving the RS-coded packets. The non-systematic RS parity place holders are placed after the enhanced data within each interleaved enhanced data packet, and a sequence of known data place holders is periodically included in the interleaved enhanced data packets.

A transmitting apparatus is provided. The transmitting apparatus includes: an encoder configured to generate a low density parity check (LDPC) codeword by LDPC encoding based on a parity check matrix; an interleaver configured to interleave the LDPC codeword; and a modulator configured to map the interleaved LDPC codeword onto a modulation symbol, wherein the modulator is further configured to map a bit included in a predetermined bit group from among a plurality of bit groups constituting the LDPC codeword onto a predetermined bit of the modulation symbol.

A transmitting apparatus is provided. The transmitting apparatus includes: an encoder configured to generate a low density parity check (LDPC) codeword by LDPC encoding based on a parity check matrix; an interleaver configured to interleave the LDPC codeword; and a modulator configured to map the interleaved LDPC codeword onto a modulation symbol, wherein the modulator is further configured to map a bit included in a predetermined bit group from among a plurality of bit groups constituting the LDPC codeword onto a predetermined bit of the modulation symbol.

A digital broadcasting system for transmitting/receiving a digital broadcasting signal and a data processing method are disclosed. A program table information has an identifier identifying mobile service data and main service data in a broadcasting signal. The program table information is multiplexed with the mobile service data and main service data. Then, broadcast receiving system can receive and output the mobile service data by parsing the program table information and using the identifier.

A transmitting system and a method of transmitting digital broadcast signal are disclosed. The method of transmitting digital broadcasting signal in a transmitter includes multiplexing a specified number of mobile data packets, a first scalable number of mobile data packets, and a second scalable number of main data packets, interleaving mobile data in the mobile data packets and main data in the main data packets, transmitting the interleaved mobile and main data during a slot, wherein the data group includes a plurality of first blocks, each first block including a plurality of data segments, specified block of the plurality of first blocks including the mobile data, known data sequence, trellis initialization data and RS parity bytes inserted in pre-determined position of the data group, wherein the data group includes a plurality of regions, wherein the last region includes the first scalable number of mobile data packets.

A transmitting apparatus is provided. The transmitting apparatus includes: an encoder configured to generate a low density parity check (LDPC) codeword by LDPC encoding based on a parity check matrix; an interleaver configured to interleave the LDPC codeword; and a modulator configured to map the interleaved LDPC codeword onto a modulation symbol, wherein the modulator is further configured to map a bit included in a predetermined bit group from among a plurality of bit groups constituting the LDPC codeword onto a predetermined bit of the modulation symbol.