Communication unit for soft-decision demodulation and method therefor

A communication unit for performing soft-decision demodulation comprising a receiver, wherein the receiver is arranged to receive a transmitted signal having a first set of bits comprising k bits that has been selected from a set of 2k possible signals according to values of the k bits, and includes a second set of bits comprising Qm bits based on a phase rotation of the transmitted signal selected from a set of 2Qm possible rotations, wherein the receiver comprises:

• a demodulator comprising a bank of 2k correlators and configured to:
• detect a transmission of each possible transmitted signal, and
• output 2k phases of the correlator outputs as a third set of inputs;
• a de-mapper circuit coupled to the demodulator and configured to:
• receive the third set of inputs;
• determine statistics derived from one aggregated correlator output phase distribution of the third set of inputs that approximates an aggregation of a 2k distributions of the output phases of the bank of 2k correlators when the corresponding one of the set of 2k possible signals was selected as the transmission signal;
• and
• output a second set of aposteriori soft bits comprising Qm soft bits.