A transmitting apparatus, comprising: an encoder configured to encode input bits to generate parity bits based on a low density parity check, LDPC code having a code rate of 3/15; an interleaver configured to interleave a codeword comprising the input bits and the parity bits; a modulator configured to demultiplex bits of the interleaved codeword to generate cells and map the cells onto at least one constellation point; and a transmitter configured to transmit a signal based on the at least one constellation point, wherein the modulator is configured to map the cells onto the at least one constellation point among constellation points represented as a table below for 64-quadrature amplitude modulation, QAM, 0.5472 + 1.1591i 0.5473 + 1.1573i 0.5467 + 1.1599i 0.5479 + 1.1585i 1.1578 + 0.5478i 1.1576 + 0.5475i 1.1591 + 0.5475i 1.1591 + 0.5475i 0.3163 + 0.5072i 0.3163 + 0.5072i 0.3163 + 0.5072i 0.3163 + 0.5072i 0.5087 + 0.3163i 0.5087 + 0.3163i 0.5087 + 0.3163i 0.5087 + 0.3163i -0.5472 + 1.1591i -0.5473 + 1.1573i -0.5467 + 1.1599i -0.5479 + 1.1585i -1.1578 + 0.5478i -1.1576 + 0.5475i -1.1591 + 0.5475i -1.1591 + 0.5475i -0.3163 + 0.5072i -0.3163 + 0.5072i -0.3163 + 0.5072i -0.3163 + 0.5072i -0.5087 + 0.3163i -0.5087 + 0.3163i -0.5087 + 0.3163i -0.5087 + 0.3163i -0.5472 - 1.1591i -0.5473 - 1.1573i -0.5467 - 1.1599i -0.5479 - 1.1585i -1.1578 - 0.5478i -1.1576 - 0.5475i -1.1591 - 0.5475i -1.1591 - 0.5475i -0.3163 - 0.5072i -0.3163 - 0.5072i -0.3163 - 0.5072i -0.3163 - 0.5072i -0.5087 - 0.3163i -0.5087 - 0.3163i -0.5087 - 0.3163i -0.5087 - 0.3163i 0.5472 - 1.1591i 0.5473 - 1.1573i 0.5467 - 1.1599i 0.5479 - 1.1585i 1.1578 - 0.5478i 1.1576 - 0.5475i 1.1591 - 0.5475i 1.1591 - 0.5475i 0.3163 - 0.5072i 0.3163 - 0.5072i 0.3163 - 0.5072i 0.3163 - 0.5072i 0.5087 - 0.3163i 0.5087 - 0.3163i 0.5087 - 0.3163i 0.5087 - 0.3163i an encoder configured to encode input bits to generate parity bits based on a low density parity check, LDPC code having a code rate of 3/15; an interleaver configured to interleave a codeword comprising the input bits and the parity bits; a modulator configured to demultiplex bits of the interleaved codeword to generate cells and map the cells onto at least one constellation point; and a transmitter configured to transmit a signal based on the at least one constellation point, wherein the modulator is configured to map the cells onto the at least one constellation point among constellation points represented as a table below for 64-quadrature amplitude modulation, QAM, 0.5472 + 1.1591i 0.5473 + 1.1573i 0.5467 + 1.1599i 0.5479 + 1.1585i 1.1578 + 0.5478i 1.1576 + 0.5475i 1.1591 + 0.5475i 1.1591 + 0.5475i 0.3163 + 0.5072i 0.3163 + 0.5072i 0.3163 + 0.5072i 0.3163 + 0.5072i 0.5087 + 0.3163i 0.5087 + 0.3163i 0.5087 + 0.3163i 0.5087 + 0.3163i -0.5472 + 1.1591i -0.5473 + 1.1573i -0.5467 + 1.1599i -0.5479 + 1.1585i -1.1578 + 0.5478i -1.1576 + 0.5475i -1.1591 + 0.5475i -1.1591 + 0.5475i -0.3163 + 0.5072i -0.3163 + 0.5072i -0.3163 + 0.5072i -0.3163 + 0.5072i -0.5087 + 0.3163i -0.5087 + 0.3163i -0.5087 + 0.3163i -0.5087 + 0.3163i -0.5472 - 1.1591i -0.5473 - 1.1573i -0.5467 - 1.1599i -0.5479 - 1.1585i -1.1578 - 0.5478i -1.1576 - 0.5475i -1.1591 - 0.5475i -1.1591 - 0.5475i -0.3163 - 0.5072i -0.3163 - 0.5072i -0.3163 - 0.5072i -0.3163 - 0.5072i -0.5087 - 0.3163i -0.5087 - 0.3163i -0.5087 - 0.3163i -0.5087 - 0.3163i 0.5472 - 1.1591i 0.5473 - 1.1573i 0.5467 - 1.1599i 0.5479 - 1.1585i 1.1578 - 0.5478i 1.1576 - 0.5475i 1.1591 - 0.5475i 1.1591 - 0.5475i 0.3163 - 0.5072i 0.3163 - 0.5072i 0.3163 - 0.5072i 0.3163 - 0.5072i 0.5087 - 0.3163i 0.5087 - 0.3163i 0.5087 - 0.3163i 0.5087 - 0.3163i