1. A communication system that performs encoding and decoding for communication, comprising: a transmitting apparatus; and a receiving apparatus, wherein the transmitting apparatus includes: a turbo encoding unit including a first encoding unit that encodes an input signal and generates a first parity bit by bit-based encoding and n (n=1, 2, 3,. .. ) second encoding units that encode the input signal and generate second parity bits by bit-based encoding; and a symbol mapping unit that maps an output from the turbo encoding unit to a symbol by bit-based mapping operation and modulates the output, and the receiving apparatus includes: a demodulating unit that demodulates a transmission signal; and a turbo decoding unit that performs turbo decoding on the demodulated signal by bit-based decoding.