Probabilistic shaping techniques for high performance coherent optical transceivers
View Patent ↗A method and structure for probabilistic shaping and compensation techniques in coherent optical receivers. According to an example, the present invention provides a method and structure for an implementation of distribution matcher encoders and decoders for probabilistic shaping applications. The techniques involved avoid the traditional implementations based on arithmetic coding, which requires intensive multiplication functions. Furthermore, these probabilistic shaping techniques can be used in combination with LDPC codes through reverse concatenation techniques.
1. A communication device comprising:
a distribution matcher encoder module including n encoder function blocks coupled in series, the series of encoder function blocks being configured to convert data from a first form (x) to a second form (b);
wherein the series of encoder function blocks is configured to receive data x, a code length n, and a bits per codeword n′ as inputs;
wherein the series of encoder function blocks includes a plurality of encoder storage units configured to store the following initial values: a n =x and n′ n =n′;
wherein the series of encoder function blocks is configured to perform the following actions for i=n−1 to 0:
wherein the series of encoder function blocks includes encoder comparison and adder circuits configured, when a first condition characterized by
a
i
+
1
≥
(
i
n
i
+
1
′
-
1
)
or a second condition characterized by n′ i+1 ≤0 is satisfied, to compute and store in the plurality of encoder storage units the following intermediate values
a
i
=
a
i
+
1
-
(
i
n
i
+
1
′
-
1
)
,
b i =0, and n′ i =n′ i+1 ;
wherein the series of encoder function blocks is configured using the encoder comparison and adder circuits, when neither the first condition nor the second condition is satisfied, to compute and store in the plurality of encoder storage units the following intermediate values: a i =a i+1 , b i =1, and n′ i =n′ i+1 −1; and
wherein the series of encoder function blocks is configured to output converted data b;
a distribution matcher decoder module including n decoder function blocks coupled in series, the series of decoder function blocks being configured to convert data from the second form to the first form;
wherein the series of decoder function blocks is configured to receive the converted data b, the code length n, and the bits per codeword n′ as inputs;
wherein the series of decoder function blocks includes a plurality of decoder storage units configured to store the following initial values: a n =0 and n′ n =n′;
wherein the series of decoder function blocks is configured to perform the following actions for i=n−1 to 0:
wherein the series of decoder function blocks includes decoder comparison and adder circuits configured, when a first condition characterized by b i ==1 or a second condition characterized by n′ i+1 ==0 is satisfied, to compute and store in the plurality of decoder storage units the following intermediate value: a i =a i+1 ;
wherein the series of decoder function blocks is configured using the decoder comparison and adder circuits, when neither the first condition nor the second condition is satisfied, to compute and store in the plurality of decoder storage units the following intermediate value:
a
i
=
a
i
+
1
+
(
i
n
i
+
1
′
-
1
)
;
wherein the series of decoder function blocks is configured using the decoder comparison and adder circuits, when the first condition is satisfied, to compute and store in the plurality of decoder storage units the following intermediate value: n′ i =n′ i+1 −1;
wherein the series of decoder function blocks is configured using the decoder comparison and adder circuits, when the first condition is not satisfied, to compute and store in the plurality of decoder storage units the following intermediate value: n′ i =n′ i+1 ; and
wherein the series of decoder function blocks is configured to store in the plurality of decoder storage units the following final value: x=a 0 ; and
wherein the series of decoder function blocks is configured to output restored data x; and
a channel module electrically coupled between the distribution matcher encoder module and the distribution matcher decoder module.
2. The device of claim 1 wherein each of the encoder function blocks comprises one or more carry save adders.
3. The device of claim 1
further comprising a splitter module electrically coupled to the distribution matcher encoder module and configured to receive data;
further comprising a forward error correction (FEC) encoder module electrically coupled to the splitter module and the distribution matcher encoder module; and
further comprising a mapper module electrically coupled to the FEC encoder module and the channel module.
4. The device of claim 1 wherein each of the decoder function blocks comprises one or more carry save adders.
5. The device of claim 1
further comprising a demapper module electrically coupled to the channel module;
further comprising a forward error correction (FEC) decoder module electrically coupled to the demapper module and the distribution matcher decoder module; and
further comprising a merger module electrically coupled to the distribution matcher decoder module and the FEC decoder module, and configured to output data.
6. A communication device comprising:
a distribution matcher encoder module including n encoder function blocks coupled in series, the series of encoder function blocks being configured to convert data from a first form (x) to a second form (b) using an encoder lookup table (LUT);
wherein the series of encoder function blocks is configured to receive data x, a code length n, and a bits per codeword n′ as inputs;
wherein the series of encoder function blocks includes a plurality of encoder storage units configured to store the following initial values: a n =x and n′ n =n′;
wherein the series of encoder function blocks is configured to perform the following actions for i=n−1 to 0:
wherein t i [n] is the function to access the encoder LUT;
wherein the series of encoder function blocks includes encoder comparison and adder circuits configured, when a first condition characterized by a i+1 ≥t i [n′ i+1 −1] or a second condition characterized by n′ i+1 ≤0 is satisfied, to compute and store in the plurality of encoder storage units the following intermediate values: a i =a i+1 −t i [n′ i+1 −1], b i =0, and n′ i =n′ i+1 ;
wherein the series of encoder function blocks is configured using the encoder comparison and adder circuits, when neither the first condition nor the second condition is satisfied, to compute and store in the plurality of encoder storage units the following intermediate values: a i =a i+1 , b i =1, and n′ i =n′ i+1 −1; and
wherein the series of encoder function blocks is configured to outputting converted data b;
a distribution matcher decoder module including n decoder function blocks coupled in series, the series of decoder function blocks being configured to convert data from the second form to the first form using a decoder LUT;
wherein the series of decoder function blocks is configured to receive the converted data b, the code length n, and the bits per codeword n′ as inputs;
wherein the series of decoder function blocks includes a plurality of decoder storage units configured to store the following initial values: a n =0 and n′ n =n′;
wherein the series of decoder function blocks is configured to perform the following actions for i=n−1 to 0:
wherein t i [n] is the function to access the decoder LUT;
wherein the series of decoder function blocks includes decoder comparison and adder circuits configured, when a first condition characterized by b i ==1 or a second condition characterized by n′ i+1 ==0 is satisfied, to compute and store in the plurality of decoder storage units the following intermediate value: a i =a i+1 ;
wherein the series of decoder function blocks is configured using the decoder comparison and adder circuits, when neither the first condition nor the second condition are satisfied, to compute and store in the plurality of decoder storage units the following intermediate value: a i =a i+1 +t i [n′ i+1 −1];
wherein the series of decoder function blocks is configured using the decoder comparison and adder circuits, when the first condition is satisfied, to compute and store in the plurality of decoder storage units the following intermediate value: n′ i =n′ i+1 −1;
wherein the series of decoder function blocks is configured using the decoder comparison and adder circuits, when the first condition is not satisfied, to compute and store in the plurality of decoder storage units the following intermediate value: n′ i =n′ i+1 ; and
wherein the series of decoder function blocks is configured to store in the plurality of decoder storage units the following final value: x=a 0 ; and
wherein the series of decoder function blocks is configured to output restored data x; and
a channel module electrically coupled between the distribution matcher encoder module and the distribution matcher decoder module.
7. The device of claim 6 wherein each of the encoder function blocks comprises one or more carry save adders.
8. The device of claim 6
further comprising a splitter module electrically coupled to the distribution matcher encoder module and configured to receive data;
further comprising an forward error correction (FEC) encoder module electrically coupled to the splitter module and the distribution matcher encoder module; and
further comprising a mapper module electrically coupled to the FEC encoder module and the channel module.
9. The device of claim 6 wherein each of the decoder function blocks comprises one or more carry save adders.
10. The device of claim 6
further comprising a demapper module electrically coupled to the channel module;
further comprising an forward error correction (FEC) decoder module electrically coupled to the demapper module and the distribution matcher decoder module; and
further comprising a merger module electrically coupled to the distribution matcher decoder module and the FEC decoder module, and configured to output data.
11. A communication device comprising:
a distribution matcher encoder module including n encoder function blocks coupled in series, the series of encoder function blocks being configured to convert data from a first form (x) to a second form (b) using an encoder lookup table (LUT);
wherein the series of encoder function blocks is configured to receive data x and a code length n as inputs;
wherein the series of encoder function blocks includes a plurality of encoder storage units configured to store the following initial value: n′=0;
wherein the series of encoder function blocks is configured to perform the following actions while
(
x
≥
(
n
n
′
)
)
:
wherein the series of encoder function blocks includes encoder comparison and adder circuits configured to compute and store in the plurality of encoder storage units the following intermediate value:
x
=
x
-
(
n
n
′
)
;
and
wherein the series of encoder function blocks is configured using the encoder comparison and adder circuits to compute and store in the plurality of encoder storage units the following intermediate value: n′=n′+1;
wherein the series of encoder function blocks is configured using the encoder comparison and adder circuits to compute and store in the plurality of encoder storage units the following intermediate value: a n =x;
wherein the series of encoder function blocks is configured to perform the following actions for i=n−1 to 0:
wherein t i [n] is the function to access the encoder LUT;
wherein the series of encoder function blocks is configured using the encoder comparison and adder circuits, when a first condition characterized by a i+1 ≥t i [n′−1] or a second condition characterized by n′≤0 is satisfied, to compute and store in the plurality of encoder storage units the following intermediate values: a i =a i+1 −t i [n′−1] and b i =0;
wherein the series of encoder function blocks is configured using the encoder comparison and adder circuits, when neither the first condition nor the second condition is satisfied, to compute and store in the plurality of encoder storage units the following intermediate values: a i =a i+1 , b i =1, and n′=n′−1; and
wherein the series of encoder function blocks is configured to output converted data b;
a distribution matcher decoder module including n decoder function blocks coupled in series, the series of decoder function blocks being configured to convert data from the second form to the first form using a decoder LUT;
wherein the series of decoder function blocks is configured to receive the converted data b and the code length n as inputs;
wherein the series of decoder function blocks includes decoder comparison and adder circuits and a plurality of decoder storage units, the series of decoder function blocks being configured using the decoder comparison and adder circuits to compute and store in the plurality of decoder storage units the following initial values: n′ n =ω H (b), where ω H (b) is the Hamming weight of b; and
a
n
=
∑
k
=
1
ω
H
(
b
)
(
n
k
)
;
wherein the series of decoder function blocks is configured to perform the following actions for i=n−1 to 0:
wherein t i [n] is the function to access the decoder LUT;
wherein the series of decoder function blocks is configured using the decoder comparison and adder circuits, when a first condition characterized by b i ==1 or a second condition characterized by n′ i+1 ==0 is satisfied, to compute and store in the plurality of decoder storage units the following intermediate value: a i =a i+1 ;
wherein the series of decoder function blocks is configured using the decoder comparison and adder circuits, when neither the first condition nor the second condition is satisfied, to compute and store in the plurality of decoder storage units the following intermediate value: a i =a i+1 +t i [n′ i+1 −1];
wherein the series of decoder function blocks is configured using the decoder comparison and adder circuits, when the first condition is satisfied, to compute and store in the plurality of decoder storage units the following intermediate value: n′ i =n′ i+1 −1;
wherein the series of decoder function blocks is configured using the decoder comparison and adder circuits, when the first condition is not satisfied, to compute and store in the plurality of decoder storage units the following intermediate value: n′ i =n′ i+1 ; and
wherein the series of decoder function blocks is configured to outputting the restored data x; and
a channel module electrically coupled between the distribution matcher encoder module and the distribution matcher decoder module.
12. The device of claim 11 wherein each of the encoder function blocks comprises one or more carry save adders.
13. The device of claim 11
further comprising a splitter module electrically coupled to the distribution matcher encoder module and configured to receive data;
further comprising an forward error correction (FEC) encoder module electrically coupled to the splitter module and the distribution matcher encoder module; and
further comprising a mapper module electrically coupled to the FEC encoder module and the channel module.
14. The device of claim 11 wherein each of the decoder function blocks comprises one or more carry save adders.
15. The device of claim 11
further comprising a demapper module electrically coupled to the channel module;
further comprising an forward error correction (FEC) decoder module electrically coupled to the demapper module and the distribution matcher decoder module; and
further comprising a merger module electrically coupled to the distribution matcher decoder module and the FEC decoder module, and configured to output data.