Patent ID: 8719656

Claim:
A method for communicating signals, comprising: receiving a K-symbol-long input block from a 2 m -ary source channel; encoding the input block into a 2 m -ary non-binary low-density parity-check (LDPC) codeword of length N; and mapping each 2 m -ary symbol to a point in a signal constellation comprised of 2 m points, wherein the non-binary LDPC code is used as the component code for forward error correction in a coded four-dimensional modulation scheme capable of achieving optical fiber communication at rates beyond 100 Gb/s; and determining a log-likelihood ratio (LLR) matrix, wherein each row k, 0≦k<N, of the LLR matrix is comprised of 2 m entries each corresponding to: λ ⁡ ( s k ( a ) ) = log ⁡ [ P ⁡ ( s k ( a ) | r ) P ⁡ ( s k ( 0 ) | r ) ] .