Inner FEC encoding systems and methods
The present invention is directed to communication systems and methods. According to a specific embodiment, FEC data streams from multiple FEC data lanes are received. First stage interleaving and inner encoding are performed on the FEC data streams to generate inner encoded data streams. A second stage interleaving process is performed to interleave the inner encoded data streams. There are other embodiments as well.
1. A communication device for transmitting data over an optical communication link in a communication system, the communication device comprising:
a plurality of first interleavers, each first interleaver configured to (i) receive a forward error correction (FEC) data stream from a respective FEC data lane, and (ii) interleave the FEC data stream to generate an interleaved stream;
a plurality of encoders configured to receive the interleaved streams from respective ones of the plurality of first interleavers and encode the interleaved streams to generate encoded interleaved streams containing soft-decodable code corresponding to the interleaved streams;
a second interleaver configured to interleave the encoded interleaved streams previously encoded by the plurality of encoders to generate an outgoing data stream comprising time-interleaved inner codewords of the encoded interleaved streams, the second interleaver being further configured to apply different delays to the encoded interleaved streams received by the second interleaver by applying a delay to respective ones of the encoded interleaved streams in a group of the encoded interleaved streams, wherein a respective delay being applied to a respective stream is different than delays applied to each other encoded interleaved stream in the group of the encoded interleaved streams, to reduce latency associated with the second interleaver receiving the encoded interleaved streams at a same time; and
a mapper configured to map the outgoing data stream into symbols for transmission over the optic communication link.
2. The communication device of claim 1 wherein the encoders comprise Hamming encoders.
3. The communication device of claim 1 wherein the encoders comprise parity-check encoders configured to add parity symbols to the interleaved streams.
4. The communication device of claim 1 wherein the mapper comprises a Gray mapper configured to prepare data for PAM4 communication.
5. The communication device of claim 1 , the second interleaver comprising M lines corresponding to an interleaving depth of N, the M lines comprising a first delay line and a second delay line, the first delay line comprising N−1 delay units, and the second delay line comprising N−2 delay units, wherein N is 21.
6. The communication device of claim 1 , the second interleaver comprising M lines corresponding to an interleaving depth of N, the M lines comprising a first delay line and a second delay line, the first delay line comprising N−1 delay units, and the second delay line comprising N−2 delay units, wherein N is 4.
7. The communication device of claim 1 , the second interleaver comprising M lines corresponding to an interleaving depth of N, the M lines comprising a first delay line and a second delay line, the first delay line comprising N−1 delay units, and the second delay line comprising N−2 delay units, wherein N is 7.
8. The communication device of claim 1 , the second interleaver comprising M lines corresponding to an interleaving depth of N, the M lines comprising a first delay line and a second delay line, the first delay line comprising N−1 delay units, and the second delay line comprising N−2 delay units, wherein N is 10.
9. A method of operating a communication device for transmitting data over an optical communication link in a communication system, the method comprising:
using each first interleaver of a plurality of first interleavers, (i) receiving a forward error correction (FEC) data stream from a respective FEC data lane, and (ii) interleaving the FEC data stream to generate an interleaved stream;
using a plurality of encoders, receiving the interleaved streams from respective ones of the plurality of first interleavers and encoding the interleaved streams to generate encoded interleaved streams containing soft-decodable code corresponding to the interleaved streams;
using a second interleaver, interleaving the encoded interleaved streams previously encoded by the plurality of encoders to generate an outgoing data stream comprising time-interleaved inner codewords of the encoded interleaved streams, interleaving the encoded interleaved streams including applying different delays to the encoded interleaved streams received by the second interleaver by applying a delay to respective ones of the encoded interleaved streams in a group of the encoded interleaved streams, wherein a respective delay being applied to a respective stream is different than delays applied to each other encoded interleaved stream in the group of the encoded interleaved streams, to reduce latency associated with the second interleaver receiving the encoded interleaved streams at a same time; and
mapping the outgoing data stream into symbols for transmission over the optic communication.
10. The method of claim 9 wherein encoding the interleaved streams comprises encoding the interleaved streams using Hamming encoders.
11. The method of claim 9 wherein encoding the interleaved streams comprises using parity-check encoders configured to add parity symbols to the interleaved streams.
12. The method of claim 9 wherein mapping the outgoing data stream comprises a using a Gray mapper configured to prepare data for PAM4 communication.
13. The method of claim 9 , wherein using the second interleaver comprises using M lines corresponding to an interleaving depth of N, the M lines comprising a first delay line and a second delay line, the first delay line comprising N−1 delay units, and the second delay line comprising N−2 delay units, wherein N is 21.
14. The method of claim 9 , wherein using the second interleaver comprises using M lines corresponding to an interleaving depth of N, the M lines comprising a first delay line and a second delay line, the first delay line comprising N−1 delay units, and the second delay line comprising N−2 delay units wherein N is 4.
15. The method of claim 9 , wherein using the second interleaver comprises using M lines corresponding to an interleaving depth of N, the M lines comprising a first delay line and a second delay line, the first delay line comprising N−1 delay units, and the second delay line comprising N−2 delay units, wherein N is 7.
16. The method of claim 9 , wherein using the second interleaver comprises using M lines corresponding to an interleaving depth of N, the M lines comprising a first delay and a second delay line, the first delay line comprising N−1 delay units, and the second delay line comprising N−2 delay units, wherein N is 10.