Optical line terminal and an optical network unit and methods therefor

1. An optical line terminal, OLT, configured to communicate in a passive optical network, PON, with optical network units, ONUs, the OLT comprising at least one processor and at least one memory including computer program code, the at least one memory and computer program code configured to, with the at least one processor, cause the OLT to perform:

grouping data units for the ONUs in groups, wherein a group comprises data units for a subset of the ONUs;

encoding the groups of data units into respective sets of codewords;

interleaving the codewords of the respective sets to obtain a stream of codewords; and

sequentially transmitting the stream of codewords to the ONUs,

wherein the OLT is further configured to perform providing, to the ONUs, subset information identifying the subset of ONUs.

2. The optical line terminal, OLT, according to claim 1 , wherein the interleaving further comprises displacing two consecutive codewords of a respective set of codewords by at least P codewords in the stream of codewords.

3. The optical line terminal, OLT, according to claim 1 , wherein the interleaving is performed based on a pre-determined pattern.

4. The optical line terminal, OLT, according to claim 1 , wherein an ONU is allocated to a respective subset of ONUs based on channel properties between the OLT and the ONUs.

5. The optical line terminal, OLT, according to claim 1 , wherein an ONU is allocated to a plurality of the subsets of ONUs.

6. The optical line terminal, OLT, according to claim 1 , wherein the OLT is further configured to perform constructing a subset frame from a respective group of data units; the constructing further comprising appending a messaging channel to the subset frame, wherein the messaging channel comprises the subset information.

7. The optical line terminal, OLT, according to claim 6 , wherein the encoding is performed on the subset frame.

8. The optical line terminal, OLT, according to claim 1 , wherein the encoding is performed using a different forward error correction, FEC, code for a different group of data units.

9. An optical network unit, ONU, configured to communicate in a passive optical network, PON, comprising an optical line terminal, OLT, the ONU comprising at least one processor and at least one memory including computer program code, the at least one memory and computer program code configured to, with the at least one processor, cause the ONU to perform:

receiving a stream of codewords from the OLT;

determining a set of codewords in the stream based on subset information identifying a subset of the ONUs, the set of codewords having data units for the subset of ONUs; and

decoding the set of codewords.

10. The optical network unit, ONU, according to claim 9 , wherein the ONU is further configured to perform providing its processing capabilities to the OLT for allocating the ONU to a respective subset of ONUs.

11. The optical network unit, ONU, according to claim 10 , wherein the processing capabilities include a decoding rate or a minimally supported displacement in the stream of codewords between two consecutive codewords of the set of codewords.

12. The optical network unit, ONU, according to claim 9 , wherein the ONU is configured to perform decoding sets of codewords; a respective set of codewords having data units for a respective subset of ONUs; and wherein the ONU is further configured to perform re-sequencing of data units encoded in the sets of codewords.

13. A method comprising:

grouping, by an optical line terminal, OLT, configured to communicate in a passive optical network, PON, with optical network units, ONUs, data units for the ONUs in groups, wherein a group comprises data units for a subset of the ONUs;

encoding the groups of data units into respective sets of codewords;

interleaving the codewords of the respective sets thereby obtaining a stream of codewords;

sequentially transmitting the stream of codewords to the ONUs; and

providing to the ONUs subset information identifying the subset of ONUs.

14. A method comprising:

receiving, from an optical line terminal, OLT, configured to communication in a passive optical network, PON, with optical network units, ONUs, a stream of codewords;

determining a set of codewords in the stream based on subset information identifying a subset of the ONUs, the set of codewords having data units for the subset of ONUs; and

decoding the set of codewords.