Encoding Circuit for Probabilistic Shaping With FEC Quadrant Mapping

The patent applies preliminary action by determining the quadrant for symbol allocation before the FEC encoding process. The quadrant determination is performed on the original bit strings before conversion, ensuring that the quadrant information is established when the bit string structure is still intact and readable. This allows the system to maintain both FEC error correction capability and accurate quadrant determination for probabilistic shaping.

The patent introduces an intermediary mapping table that stores the association relationships between original bit strings and converted bit strings. This mapping table acts as a mediator that preserves the connection between the original bit string values and the converted values used for probabilistic shaping. The mapping table allows the system to maintain accurate association information even as bit strings undergo conversion to achieve the desired symbol distribution towards the constellation center.

The patent applies local quality by performing bit string conversion selectively for specific bit strings that are not used for quadrant determination. The conversion is applied locally to the appropriate bit strings to achieve the desired probability distribution, while leaving the quadrant-determining bit strings unchanged. This localized approach allows asymmetric symbol mapping to improve constellation utilization while maintaining noise tolerance by preserving the integrity of the bit strings needed for reliable quadrant identification.