Encoded signal demodulation method, apparatus, device, and computer readable storage medium

An encoded signal demodulation apparatus comprising a non-transitory computer readable medium storing instructions that, when executed by at least one processor, cause the at least one processor to:

• obtain a local ideal signal of a transmitted signal corresponding to each encoding state of a number of states at a current time based on a phase-free information waveform of each encoding state at the current time and a practical accumulated phase corresponding to each encoding state at the current time,
• wherein each encoding state is determined based on a first predetermined number of information bits and each fixed accumulated phase corresponding to a first modulation index,
• wherein the local ideal signal is based on the first predetermined number of information bits included in each encoding state,
• wherein the fixed accumulated phase is obtained based on the first modulation index, a practical accumulated phase at a previous time and each encoded information bits at the previous time,
• wherein the phase-free information waveform of each encoding state is obtained based on a second modulation index, a second predetermined number of encoded information bits before the current time, and each encoded information bits at the current time,
• wherein the practical accumulated phase at each current time is obtained based on the second modulation index, the practical accumulated phase at the previous time, and each encoded information bit at the previous time,
• wherein 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, and the first predetermined number is equal to a memory depth of encoding rules;
• obtain a branch metric for each branch path at the current time based on the local ideal signal and a received signal corresponding in time to the local ideal signal;
• obtain first and second modulation index error correction path metrics for the first and second modulation indices at the current time based on the branch metric for each encoding state at the current time, and at least one of a survivor path metric for a survivor path at the previous time or a third predetermined number of surviving branch metrics for the survivor path at the previous time;
• and
• in response to a determination that the received signal is not an ending signal, jump to each encoding state at a next time until a backtracking predetermined requirement is satisfied, backtracking any of the survivor paths of each encoding state at the current time, and outputting demodulated information bits.