Demodulation method, apparatus, device and computer readable storage medium

A demodulation apparatus, comprising:

• a local ideal signal acquisition unit configured to obtain a local ideal signal corresponding to each state at a current moment based on a phase-free information waveform of each state at the current moment and a practical accumulated phase corresponding to each state at the current moment, wherein each state is determined based on a first predetermined number of information bits and a fixed accumulated phase corresponding to a first modulation index, the fixed accumulated phase is obtained based on the first modulation index, the practical accumulated phase of a previous moment and information bits of the previous moment, the phase-free information waveform is obtained based on a second modulation index, the first predetermined number of information bits before the current moment and the information bits of the current moment, the practical accumulated phase of each current moment is obtained based on the second modulation index, the practical accumulated phase of the previous moment and the information bits of the previous moment, the first modulation index is a rational number in a range of modulation indices, the second modulation index is any value in the range of modulation indices;
• a branch metric acquisition unit configured to obtain a branch metric for each branch path based on each local ideal signal and a received signal corresponding to the local ideal signal;
• an addition comparison selection—survivor path determination—metric recording unit configured to obtain each modulation index error correction path metric for the current moment based on each branch metric for the current moment, and at least one of a survivor path metric for a survivor path of the previous moment and a second predetermined number of surviving branch metrics for the survivor path of the previous moment, compare modulus of each modulation index error correction path metric into the same state, and obtain the survivor path metric, survivor paths and information bits for each state at the current moment that satisfies requirements;
• and
• a state jumping and backtracking output unit configured to jump to each state of a next moment until a backtracking predetermined requirement is reached in response to a determination that the received signal is a non-ending signal, and backtrack any of the survivor paths of each state at the current moment, and output the information bits corresponding to a backtracking moment.