Patent ID: 7450613

Claim:
A digital broadcast transmission system for use with main data and first and second enhanced data, the digital broadcast transmission system comprising: a multiplexer unit for multiplexing a first enhanced data packet and a second enhanced data packet according to a first predetermined multiplexing rule, subjecting the multiplexed first and second enhanced data packet to a forward error correction code to produce formatted enhanced data, and multiplexing the formatted enhanced data and the main data in response to a second predetermined multiplexing rule; a first encoder in communication with the multiplexer unit for performing data randomizing, parity supplementing and data interleaving to a data packet output from the multiplexer unit; a symbol processor in communication with the first encoder for converting the data packet output from the first encoder to a plurality of symbols, encoding only enhanced data symbols at a rate of 1/L, L being an integer equal to or greater than 2, and converting the symbols to byte unit data; a first decoder for deinterleaving the byte unit data output from the symbol processor, removing parity data added by the first encoder from the deinterleaved byte unit data, and derandomizing the parity-removed data; and a transmitter including a trellis coder for performing parity supplementing, data interleaving, and trellis coding to the data output from the first decoder to produce a converted data packet and transmitting the converted data packet, wherein the first enhanced data is encoded at a code rate of 1/M, M being an integer equal to or greater than 2, and the second enhanced data is encoded at a code rate of 1/N, N being an integer greater than M, wherein a number of the first enhanced data packets is defined as ‘H’, and a number of the second enhanced data packets is defined as ‘Q’, such that the first and the second enhanced data packets are multiplexed in one data field in accordance with 0≦(MH+NQ)≦K, wherein K is a number of data segments in one data field.