Joint source and LDPC coding based coding modulation for ultra-high-speed optical transport
A method for optical communication includes combining jointly source coding with LDPC channel coding into a nonuniform signalling by mapping low-complexity variable-length prefix codes onto a constellation; and performing arbitrary nonuniform signalling, where information bits and parity bits are transmitted with different modulation schemes.
1. A method for optical communication, comprising:
combining joint source coding with low density parity-check (LDPC) channel coding into a nonuniform signaling by mapping low-complexity variable-length prefix codes onto a constellation; and
generating an arbitrary form of the nonuniform signaling where information bits and parity bits are transmitted with different modulation schemes;
generating a nonuniform constellation with an overall search method to determine a radius of each layer and a relative angle for each layer of the constellation, wherein a constellation structure is based on a Huffman code with a number of points on each layer and number of layers, represented as N i and S, where i in N i denotes a sequence of N values, further comprising:
searching over all possible R i as a radius of each layer, with a defined step size Δr and where i in R i denotes a sequence of R values;
searching over a relative angle for each layer with another step size Δθ;
after increasing each step size, determining a constellation figure of merit (CFM) and searching over a given range of radius and angle and determining a combination with maximum CFM; and
with the radius of each layer and the relatively angle for each layer specified, determining constellation sets with N i and S.
2. The method of claim 1 , comprising choosing constellation points with a nonuniform probability distribution.
3. The method of claim 1 , comprising selecting constellation points according to a Maxwell-Boltzmann distribution to achieve shaping gain in any dimension.
4. The method of claim 1 , wherein a coded modulation is used for the arbitrary nonuniform signaling.
5. The method of claim 1 , comprising the information bits and the parity bits being transmitted with different modulation schemes in order to achieve a data rate with a modulation scheme.
6. The method of claim 1 , comprising the nonuniform signaling being achieved by employing either Huffman coding or Ziv-Lempel algorithm.
7. The method of claim 1 , comprising systematic low-density parity-check LDPC coding being used as channel coding.
8. The method of claim 1 , comprising systematic low-density parity-check LDPC coding being used as channel coding, wherein bits from source codes are transmitted unchanged, while generalized parity bits, derived from a parity matrix of the LDPC coding, are transmitted.
9. The method of claim 1 , comprising providing signal constellation designs for a joint source or low-density parity-check LDPC coding.
10. The method of claim 1 , wherein the nonuniform constellation comprises employing either a Huffman coding or Ziv-Lempel method.
11. The method of claim 1 , wherein source and channel coding are jointly performed.
12. The method of claim 1 , wherein information bits are source-encoded and mapped to specially designed constellation.
13. The method of claim 1 , comprising obtaining parity-bits by a systematic LDPC encoder.
14. The method of claim 1 , comprising transmitting parity-bits over signal constellations.