Transmitting apparatus and modulation method thereof

A broadcast signal transmitting apparatus comprising:

• an encoder configured to encode input bits to generate parity bits based on a low density parity check (LDPC) code;
• an interleaver configured to interleave a codeword comprising the input bits and the parity bits;
• a mapper configured to demultiplex bits of the interleaved codeword to generate cells, and map the cells to 2-dimensional (2D) non-uniform constellation points using 64-quadrature amplitude modulation (QAM) and position vectors w, in which w comprises w0, and w15;
• and
• a transmitter configured to transmit a broadcast signal which is generated based on the constellation points,
• wherein the cells are mapped to the constellation points by determining a position vector wi, in which i is any one of 0 to 15, corresponding to a cell from among the position vectors w, and determining a quadrant of the position vector wi, and
• wherein the position vectors w are represented in a table below:
• w0
• 0.5472 + 1.1591i
• w1
• 0.5473 + 1.1573i
• w2
• 0.5467 + 1.1599i
• w3
• 0.5479 + 1.1585i
• w4
• 1.1578 + 0.5478i
• w5
• 1.1576 + 0.5475i
• w6
• 1.1591 + 0.5475i
• w7
• 1.1591 + 0.5475i
• w8
• 0.3163 + 0.5072i
• w9
• 0.3163 + 0.5072i
• w10
• 0.3163 + 0.5072i
• w11
• 0.3163 + 0.5072i
• w12
• 0.5087 + 0.3163i
• w13
• 0.5087 + 0.3163i
• w14
• 0.5087 + 0.3163i
• w15
• 0.5087 + 0.3163i