In accordance with embodiments, methods for data communications are disclosed. A device obtains a forward error correction (FEC) encoded bit stream. The device maps the FEC encoded bit stream to produce a set of symbols according to a bit-to-symbol mapping rule. The bit-to-symbol mapping rule comprises a first mapper bit position associated with a first mapper error protection level and a second mapper bit position associated with a second mapper error protection level. The first mapper error protection level is greater than the second mapper error protection level. The device then transmits the set of symbols in the communications system.