# US 12,113,611 B2 · Method and apparatus for downstream transmission > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,113,611 B2 - Document ID: US12113611B2 - Status: Granted - Kind: B2 - Application number: 18/061,668 - Filed: 2022-12-05 - Published: 2023-06-08 - Granted: 2024-10-08 - Earliest claimed: 2021-12-08 - Assignees: Nokia Solutions and Networks Oy - Applicants: Nokia Solutions and Networks Oy - Inventors: Yannick Lefevre - Web page: https://patentgrep.com/patent/US12113611B2 ## CPC - H04B 10/516: Details of coding or modulation - H04J 14/0245: {for downstream transmission, e.g. optical line terminal [OLT] to ONU} - H03M 13/255: {with Low Density Parity Check [LDPC] codes} - H03M 13/2792: {Interleaver wherein interleaving is performed jointly with another technique such as puncturing, multiplexing or routing} - H04B 10/272: Star-type networks {or tree-type networks} - H04L 1/0057: {Block codes (H04L1/0061, H04L1/0064 take precedence)} - H04L 1/0071: {Use of interleaving (interleaving per se H03M13/27)} - H04Q 11/0067: {Provisions for optical access or distribution networks, e.g. Gigabit Ethernet Passive Optical Network (GE-PON), ATM-based Passive Optical Network (A-PON), PON-Ring} - H04B: TRANSMISSION - H04J: MULTIPLEX COMMUNICATION (transmission in general H04B; peculiar to transmission of digital information H04L5/00; systems for the simultaneous or sequential transmission of more than one television signal H04N7/08; in exchanges H04Q11/00; stereophonic systems H04S) - H03M: CODING; DECODING; CODE CONVERSION IN GENERAL (using fluidic means F15C4/00; optical analogue/digital converters G02F7/00; coding, decoding or code conversion, specially adapted for particular applications, see the relevant subclasses, e.g. G01D, G01R, G06F, G06T, G09G, G10L, G11B, G11C, H04B, H04L, H04M, H04N; ciphering or deciphering for cryptography or other purposes involving the need for secrecy G09C) - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) - H04Q: SELECTING (switches, relays, selectors H01H; wireless communication networks H04W) ## Abstract In one embodiment, an apparatus is configured to perform mapping an interleaved bit stream into a sequence of 4-level pulse amplitude modulation (PAM4) labels according to a mapping scheme, with a respective PAM4 label including a least significant bit (LSB) and a most significant bit (MSB) respectively corresponding to a bit in the interleaved bit stream; transmitting a sequence of PAM4 symbols generated based on the sequence of PAM4 labels to the ONUs; and wherein, bits from respective one of the N codewords are assigned to LSBs of a first subset of labels, and to MSBs of a second subset of labels, with the first and the second subset of labels being determined based on the interleaving scheme and the mapping scheme and respectively comprising labels located N labels apart in the sequence of PAM4 labels. ## Claims ### Claim 1 An apparatus for use by an Optical Line Terminal (OLT) communicatively connected to optical network units (ONUs), comprising: at least one memory storing computer program code; and at least one processor configured to execute the computer program code and cause the apparatus to perform, interleaving a first number N of codewords according to an interleaving scheme, obtaining an interleaved bit stream, wherein, N is an even number; mapping the interleaved bit stream into a sequence of 4-level pulse amplitude modulation (PAM4) labels according to a mapping scheme, with a respective PAM4 label comprising a least significant bit (LSB) and a most significant bit (MSB) respectively corresponding to a bit in the interleaved bit stream; transmitting a sequence of PAM4 symbols generated based on the sequence of PAM4 labels to the ONUs; wherein, bits from respective one of the N codewords are assigned to LSBs of a first subset of labels, and to MSBs of a second subset of labels, with the first and the second subset of labels being determined based on the interleaving scheme and the mapping scheme and respectively comprising labels located N labels apart in the sequence of PAM4 labels. ### Claim 2 (depends on 1) The apparatus according to claim 1, wherein, the second subset of labels comprises the labels of the first subset. ### Claim 3 (depends on 2) The apparatus according to claim 2, the interleaving scheme indicates an interleaving step of two bits. ### Claim 4 (depends on 1) The apparatus according to claim 1, wherein, the second subset of labels comprises labels that are N/2 labels apart from labels of the first subset. ### Claim 5 (depends on 4) The apparatus according to claim 4, wherein the interleaving scheme indicates an interleaving step of one bit; and that, in the interleaved bit stream, bits from respective one of the N codewords are spaced alternatingly with N and N−2 bits from other codewords therebetween. ### Claim 6 (depends on 4) The apparatus according to claim 4, wherein the interleaving scheme indicates an interleaving step of one bit; and wherein, the mapping scheme comprises inverting the mapping of the interleaved bit stream into PAM4 labels every N/2 PAM4 labels. ### Claim 7 (depends on 1) The apparatus according to claim 1, wherein the apparatus is further caused to perform sending a message indicating at least one of, the mapping scheme used by the OLT, or the interleaving scheme used by the OLT to respective one of the ONUs. ### Claim 8 An apparatus, for use by an Optical Network Unit (ONU) communicatively connected to an Optical Line Terminal (OLT), comprising: at least one memory storing computer program code; and at least one processor configured to execute the computer program code and cause the apparatus to perform, receiving a sequence of 4-level pulse amplitude modulation (PAM4) symbols from the OLT; deriving, for a codeword to be processed, from the received sequence of PAM4 symbols, a sequence of pairs of bit indicators, respective one of the pairs corresponding to respective one of the symbols and comprising a least significant bit (LSB) indicator and a most significant bit (MSB) indicator, the sequence of pairs comprising a first subset of pairs and a second subset of pairs, the first and the second subset being determined based on a de-mapping scheme and a de-interleaving scheme, and respectively comprising pairs corresponding to PAM4 symbols located N symbols apart in the sequence of PAM4 symbols; determining said codeword based on LSB indicators of the first subset of pairs, and MSB indicators of the second subset of pairs; wherein, the de-mapping scheme indicates a relationship between bit indicators of a respective pair and the corresponding PAM4 symbol, and the de-interleaving scheme indicates a de-interleaving step of k bit indicators and a first number N of codewords that are interleaved at the OLT, with N being an even number. ### Claim 9 (depends on 8) The apparatus according to claim 8, wherein the determining of said codeword is implemented by: de-mapping the sequence of pairs of bit indicators into a stream of bit indicators according to the de-mapping scheme; extracting a set of bit indicators related to said codeword from the stream of bit indicators according to the de-interleaving scheme; determining said codeword based on the set of bit indicators related to said codeword. ### Claim 10 (depends on 8) The apparatus according to claim 8, wherein, the second subset of pairs comprises the pairs of the first subset. ### Claim 11 (depends on 8) The apparatus according to claim 8, wherein, the symbols corresponding to the pairs of the second subset are N/2 symbols apart from symbols corresponding to the pairs of the first subset. ### Claim 12 (depends on 8) The apparatus according to claim 8, wherein the de-interleaving scheme and/or the de-mapping scheme is preconfigured in the ONU. ### Claim 13 (depends on 8) The apparatus according to claim 8, wherein the apparatus is further caused to perform, determining the de-interleaving scheme and/or the de-mapping scheme by trying out a plurality of de-interleaving schemes and/or a plurality of de-mapping schemes preconfigured in the ONU; and/or receiving from the OLT a message indicating at least one of a mapping scheme used by the OLT, or a interleaving scheme used by the OLT. ### Claim 14 A method, for use by an Optical Line Terminal (OLT) communicatively connected to optical network units (ONUs) comprising: interleaving a first number N of codewords according to an interleaving scheme, obtaining an interleaved bit stream, wherein, N is an even number; mapping the interleaved bit stream into a sequence of 4-level pulse amplitude modulation (PAM4) labels according to a mapping scheme, with a respective PAM4 label comprising a least significant bit (LSB) and a most significant bit (MSB) respectively corresponding to a bit in the interleaved bit stream; transmitting a sequence of PAM4 symbols generated based on the sequence of PAM4 labels to the ONUs; wherein, bits from respective one of the N codewords are assigned to LSBs of a first subset of labels, and to MSBs of a second subset of labels, with the first and the second subset of labels being determined based on the interleaving scheme and the mapping scheme and respectively comprising labels located N labels apart in the sequence of PAM4 labels. ### Claim 15 A method, for use by an Optical Network Unit (ONUs) communicatively connected to an Optical Line Terminal (OLT) comprising: receiving a sequence of 4-level pulse amplitude modulation (PAM4) symbols from the OLT; deriving, for a codeword to be processed, from the received sequence of PAM4 symbols, a sequence of pairs of bit indicators, respective one of the pairs corresponding to respective one of the symbols and comprising a least significant bit (LSB) indicator and a most significant bit (MSB) indicator, the sequence of pairs comprising a first subset of pairs and a second subset of pairs, the first and the second subset being determined based on a de-mapping scheme and a de-interleaving scheme, and respectively comprising pairs corresponding to PAM4 symbols located N symbols apart in the sequence of PAM4 symbols; determining said codeword based on LSB indicators of the first subset of pairs, and MSB indicators of the second subset of pairs; wherein, the de-mapping scheme indicates a relationship between bit indicators of a respective pair and the corresponding PAM4 symbol, and the de-interleaving scheme indicates a de-interleaving step of k bit indicators and a first number N of codewords that are interleaved at the OLT, with N being an even number.