Coded polarization-multiplexed iterative polar modulation
View Patent ↗Systems and methods for optical communication that use a transmitter/receiver. The systems and methods include receiving a modulated, encoded input stream. Channel memory is reduced using coarse digital backpropagation and other channel impairments are removed using turbo equalization. Symbols are detected in the input stream that conform to a non-uniform, polar constellation having a Gaussian source distribution to produce a stream of encoded data. The stream of encoded data is decoded with one or more low density parity check (LDPC) decoders.
1. A method for receiving, comprising:
receiving a modulated, encoded input stream;
reducing channel memory using coarse digital backpropagation;
removing channel impairments using turbo equalization;
detecting symbols in the input stream that conform to a non-uniform, polar constellation having a Gaussian source distribution to produce a stream of encoded data; and
decoding the stream of encoded data with one or more low density parity check (LDPC) decoders.
2. The method of claim 1 , wherein the constellation is an iterative polar modulation (IPM) constellation.
3. The method of claim 1 , wherein the input stream is decoded with a large-girth, high-rate, quasi-cyclic LDPC code.
4. The method of claim 1 , wherein said decoding includes iterating extrinsic LLRs between a maximum a posteriori (MAP) equalizer and one or more LDPC decoders until convergence or until predetermined number of iterations has been reached.
5. The method of claim 1 , further comprising:
receiving an optical carrier beam; and
splitting the optical carrier beam into two orthogonal polarizations, each having a modulated, encoded input stream.
6. The method of claim 1 , wherein points of the constellation are determined by iteratively applying
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where L i number of constellation points in the i th circle, m i is the radius of the i th circle, L is the total number of constellation points, p(r) is the Rayleigh distribution function, and the limits of integration r i are determined by r i =π(m i 2 −m i−1 2 )/2[m i L i sin(Δθ i /2)−m i−1 L i−1 sin(Δθ i /2)], i=1, 2, . . . , L r .
7. A receiver, comprising:
one or more detectors, each configured to extract symbols that conform to a non-uniform, polar constellation having a Gaussian source distribution from a carrier beam and to output a coded stream;
one or more log likelihood ratio (LLR) modules configured to generate LLR information for the respective coded streams, comprising a lookup table configured to store correspondences between bit sequences and the symbols; and
one or more decoder, each configured to accept a coded stream and the associated LLR information and to produce a decoded data stream;
a digital backpropagation module configured to reduce channel memory; and
a turbo equalization module configured to compensate for channel impairments.
8. The receiver of claim 7 , wherein the digital backpropagation module is configured to use coarse backpropagation.
9. The receiver of claim 7 , comprising:
a beam splitter configured to accept a transmission carrier beam and split the transmission carrier beam into two orthogonally polarized carrier beams;
two detectors configured to receive the respective polarized carrier beams and to output IPM signals.
10. The receiver of claim 7 , wherein the decoders are large-girth, high-rate, quasi-cyclic LDPC decoders.
11. The receiver of claim 7 , wherein the number of decoders is equivalent to twice the number of bits represented by each IPM symbol.
12. The receiver of claim 7 , wherein each orthogonally polarized carrier beam has an associated number of decoders and the numbers of decoders associated with the respective orthogonally polarized carrier beams are different.