1 bit is assigned depending on whether it is an inner circle or an outer circle on the constellation mapping diagram, 2 bits are assigned to each quadrant, and the phase of the symbol of the inner circle or outer circle of the 8QAM received symbol set that has been bit mapped is phase-shifted. By generating the degree, a 2-bit likelihood assigned to the quadrant of the phase-rotated 8QAM symbol set is generated together with the likelihood of the received symbol of QPSK, and the phase-rotated 8QAM symbol set is further constellated. Rotate the phase to the first quadrant on the mapping diagram, move to the QPSK symbol mapping position, and generate 1-bit likelihood assigned to the inner circle or outer circle of the 8QAM symbol set by QPSK likelihood generation .
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