A transmission device comprising: a low-density parity-check, LDPC, encoder that generates a codeword from a data string by using a quasi-cyclic low-density parity-check, QC-LDPC, coding scheme, the codeword being composed of 45 cyclic blocks, each cyclic block including 360 bits; an interleaver that performs a first permutation and a second permutation on the codeword, the first permutation dividing the 45 cyclic blocks into 15 sections according to a first rule shown in Table 1, according to a code rate of the QC-LDPC coding scheme, each section including 3 cyclic blocks, thereby rearranging the 45 cyclic blocks, the second permutation rearranging bits within each section according to a second rule, thereby generating 180 spatial-multiplexing blocks for each section, each spatial-multiplexing block including 2 bits from each of the 3 cyclic blocks that constitute the section; [Table 1] Code rate 7/15 8/15 3/5 Section 1 1st 13 12 32 2nd 11 27 38 3rd 44 14 25 Section 2 1st 41 35 18 2nd 24 13 28 3rd 12 38 34 Section 3 1st 16 7 7 2nd 27 39 39 3rd 14 9 15 Section 4 1st 22 19 20 2nd 32 43 40 3rd 5 33 44 Section 5 1st 17 24 19 2nd 29 25 12 3rd 39 10 29 Section 6 1st 6 6 14 2nd 35 45 17 3rd 30 21 21 Section 7 1st 10 2 33 2nd 8 28 5 3rd 37 4 24 Section 8 1st 3 3 36 2nd 38 17 41 3rd 1 15 31 Section 9 1st 7 40 10 2nd 42 42 6 3rd 26 22 27 Section 10 1st 15 8 45 2nd 28 41 42 3rd 34 11 37 Section 11 1st 9 32 13 2nd 23 16 43 3rd 43 18 11 Section 12 1st 4 44 26 2nd 40 31 16 3rd 2 37 22 Section 13 1st 20 30 2 2nd 25 26 1 3rd 36 29 3 Section 14 1st 21 34 8 2nd 33 36 30 3rd 31 23 9 Section 15 1st 18 5 23 2nd 19 20 4 3rd 45 1 35 a constellation mapper that modulates each spatial-multiplexing block to generate a quadrature phase shift keying, QPSK, complex symbol and a 16 quadrature amplitude modulation, 16QAM, complex symbol; and a transmitter that transmits, in an identical time slot at an identical frequency, a signal generated from the QPSK complex symbol from a first antenna and a signal generated from the 16QAM complex symbol from a second antenna, wherein a ratio of transmission strength of the first antenna to transmission strength of the second antenna is 1:1. a low-density parity-check, LDPC, encoder that generates a codeword from a data string by using a quasi-cyclic low-density parity-check, QC-LDPC, coding scheme, the codeword being composed of 45 cyclic blocks, each cyclic block including 360 bits; an interleaver that performs a first permutation and a second permutation on the codeword, the first permutation dividing the 45 cyclic blocks into 15 sections according to a first rule shown in Table 1, according to a code rate of the QC-LDPC coding scheme, each section including 3 cyclic blocks, thereby rearranging the 45 cyclic blocks, the second permutation rearranging bits within each section according to a second rule, thereby generating 180 spatial-multiplexing blocks for each section, each spatial-multiplexing block including 2 bits from each of the 3 cyclic blocks that constitute the section; [Table 1] Code rate 7/15 8/15 3/5 Section 1 1st 13 12 32 2nd 11 27 38 3rd 44 14 25 Section 2 1st 41 35 18 2nd 24 13 28 3rd 12 38 34 Section 3 1st 16 7 7 2nd 27 39 39 3rd 14 9 15 Section 4 1st 22 19 20 2nd 32 43 40 3rd 5 33 44 Section 5 1st 17 24 19 2nd 29 25 12 3rd 39 10 29 Section 6 1st 6 6 14 2nd 35 45 17 3rd 30 21 21 Section 7 1st 10 2 33 2nd 8 28 5 3rd 37 4 24 Section 8 1st 3 3 36 2nd 38 17 41 3rd 1 15 31 Section 9 1st 7 40 10 2nd 42 42 6 3rd 26 22 27 Section 10 1st 15 8 45 2nd 28 41 42 3rd 34 11 37 Section 11 1st 9 32 13 2nd 23 16 43 3rd 43 18 11 Section 12 1st 4 44 26 2nd 40 31 16 3rd 2 37 22 Section 13 1st 20 30 2 2nd 25 26 1 3rd 36 29 3 Section 14 1st 21 34 8 2nd 33 36 30 3rd 31 23 9 Section 15 1st 18 5 23 2nd 19 20 4 3rd 45 1 35 a constellation mapper that modulates each spatial-multiplexing block to generate a quadrature phase shift keying, QPSK, complex symbol and a 16 quadrature amplitude modulation, 16QAM, complex symbol; and a transmitter that transmits, in an identical time slot at an identical frequency, a signal generated from the QPSK complex symbol from a first antenna and a signal generated from the 16QAM complex symbol from a second antenna, wherein a ratio of transmission strength of the first antenna to transmission strength of the second antenna is 1:1.