Joint modulation and coding method and system in coherent optical communication digital multicarrier system

Abstract

This invention provides a joint modulation and coding method and system in a coherent optical communication digital multicarrier system, comprising: Step S1: Transmitter encoding and modulation, where the input information bit sequence is encoded and digitally modulated to obtain a symbol sequence; Step S2: Receiver demodulation and decoding, where the received symbols are digitally demodulated and decoded for error correction to obtain an information bit sequence. This invention proposes a joint modulation and coding method in a digital multicarrier system, relating to the field of coherent optical communication applications, and possesses the ability to modulate, encode, demodulate, and decode bit information. This invention designs a subcarrier joint modulation and coding method, which can flexibly adjust the modulation and coding parts of each subcarrier according to channel conditions, better achieving a trade-off between performance and complexity. This invention is easy to implement, convenient to use, and has low implementation complexity, overcoming the shortcomings of existing technologies.

Description

Technical Field

[0001] This invention relates to the field of optical transmission detection technology, specifically to a joint modulation and coding method and system in a coherent optical communication digital multicarrier system. More specifically, it relates to a modulation and coding method and system for multiple subcarriers in a coherent optical communication digital multicarrier system. Background Technology

[0002] Coherent optical communication is the lifeline of global communications, handling over 95% of communication traffic. To meet the ever-increasing demand for communication traffic, the speed of coherent optical communication needs continuous improvement. To achieve higher-speed coherent optical communication, transceiver bandwidth is constantly increasing, enabling high baud rate signals. Furthermore, compared to single-carrier signals, digital multi-carrier signals offer better fiber nonlinearity performance and better resistance to filtering impairments; therefore, digital multi-carrier signals are being used in coherent optical communication.

[0003] To achieve error-free transmission in coherent optical communication, powerful digital signal processing (DSP) technology is required. Advanced modulation and forward error correction (FEC) coding are crucial components, and FEC is also a significant source of algorithm power consumption. Traditional coherent optical communication systems typically use a bit-interleaved coded modulation (BICM) structure. In this structure, bits mapped from Quadrature Amplitude Modulation (QAM) symbols are fully interleaved, and binary FEC corrects errors. In BICM, for the same modulation format, the burden of FEC increases linearly with the signal baud rate. Therefore, for high baud rate systems, FEC introduces significant power consumption. Thus, low-complexity FEC algorithms are essential. Compared to BICM, multi-level coding (MLC) offers a better trade-off between complexity and performance. By protecting only the least reliable bit (LRB), MLC can significantly reduce the complexity and latency associated with FEC decoding without sacrificing performance.

[0004] In digital multicarrier systems, different subcarriers may have different performance characteristics due to filtering effects and fiber nonlinearity. To ensure error-free transmission for each subcarrier without leaving any performance margin, joint modulation and coding of subcarriers that match channel conditions is essential.

[0005] Patent document CN115441954A (application number: CN202210933923.7) discloses a probability-shaped pulse amplitude modulation method, apparatus, and system, relating to the field of coherent optical communication technology. The method includes the following steps: transmitting a PAM-N signal with equal probability for each PAM symbol; receiving the PAM-N signal and obtaining the symbol error distribution of the PAM symbols in the PAM-N signal; adjusting the transmission probability of the PAM symbols according to the symbol error distribution of the PAM symbols, so that the symbol error rate is consistent when transmitting each PAM symbol; transmitting a probability-shaped PAM-N signal obtained by re-encoding based on the adjusted transmission probability of the PAM symbols; and receiving the probability-shaped PAM-N signal. However, this invention does not perform encoding and digital modulation of the input information bit sequence to obtain a symbol sequence, and then perform digital demodulation and decoding error correction to obtain the information bit sequence. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the purpose of this invention is to provide a joint modulation and coding method and system in a coherent optical communication digital multicarrier system.

[0007] A joint modulation and coding method in a coherent optical communication digital multicarrier system provided by the present invention includes:

[0008] Step S1: Transmitter encoding and modulation: After encoding and digitally modulating the input information bit sequence, a symbol sequence is obtained;

[0009] Step S2: Demodulation and decoding at the receiving end. After digital demodulation and decoding error correction of the received symbols, the information bit sequence is obtained.

[0010] Preferably, in step S1:

[0011] Step S1.1: After the information bit sequence is converted from serial to parallel, a portion of the information bits enter the distribution matcher for encoding. The input information bit sequence is converted into an amplitude sequence with a preset probability distribution. The obtained amplitude sequence is then converted into an information bit sequence through a preset mapping method.

[0012] Step S1.2: The bit sequence obtained in step S1.1 and another part of the information bits are encoded by the outer hard decision FEC to obtain a bit sequence containing the check bits. The bit sequence then enters the interleaving module.

[0013] Step S1.3: After interleaving, a portion of the bit sequence is sequentially encoded and interleaved using inner-layer soft-decision FEC, and then modulated together with other bits to obtain the symbol sequence that each subcarrier needs to transmit.

[0014] Preferably, in step S1.1, the signal-to-noise ratio of each subcarrier is estimated by sending training symbols, the rate of each subcarrier is allocated according to the signal-to-noise ratio of each subcarrier, and the amplitude probability distribution of the output amplitude sequence is determined at the same time.

[0015] In step S1.3, the implementation of the inner soft-decision FEC coding is determined based on the bit error rate of each subcarrier and the bit error rate threshold of the outer hard-decision FEC.

[0016] Set up inner soft-decision FEC encoding and decoding for a bit, calculate the normalized generalized mutual information of the bit, and calculate the bit error rate after inner soft-decision FEC decoding based on the error correction capability of soft-decision FEC. Then, combine the bit error rate with other bits that do not participate in inner soft-decision FEC encoding and decoding.

[0017] If the final bit error rate meets the bit error rate threshold requirement of the outer hard decision FEC, determine the bits that need to be encoded by the inner soft decision FEC; if the final bit error rate does not meet the bit error rate threshold requirement of the outer hard decision FEC, add one bit for inner soft decision FEC encoding and decoding, and repeat the steps until the final bit error rate meets the bit error rate threshold requirement of the outer hard decision FEC.

[0018] Preferably, in step S2:

[0019] Step S2.1: Receive each carrier symbol sequence, perform soft decision to obtain the log-likelihood ratio, and after deinterleaving, enter the inner soft decision FEC decoding to obtain a near error-free bit sequence. This bit sequence is used as prior information to assist hard decision to obtain a bit sequence containing errors.

[0020] Step S2.2: After deinterleaving, the bit sequence obtained in step S2.1 enters the outer hard decision FEC decoding to obtain the error-corrected bit sequence;

[0021] Step S2.3: A portion of the bit sequence is reverse mapped to obtain an amplitude sequence. The amplitude sequence is decoded and converted into a bit sequence by a distribution matcher. Then, it is combined with another portion of the bit sequence to obtain the final bit sequence.

[0022] Preferably, in step S2.1, soft decision is performed on the bits that need to be encoded and decoded by inner soft decision FEC, and the log-likelihood ratio is calculated; hard decision is performed on other bits that do not need to be encoded and decoded by inner soft decision FEC, and they are only determined to be bit 0 or bit 1, and the hard decision is based on the bits after inner soft decision FEC decoding as a priori conditions.

[0023] According to the present invention, a joint modulation and coding system in a coherent optical communication digital multicarrier system includes:

[0024] Module M1: Transmitter encoding and modulation, which encodes and digitally modulates the input information bit sequence to obtain a symbol sequence;

[0025] Module M2: Receiver demodulation and decoding. After digital demodulation and decoding error correction of the received symbols, the information bit sequence is obtained.

[0026] Preferably, in module M1:

[0027] Module M1.1: After the information bit sequence is converted from serial to parallel, a portion of the information bits enter the distribution matcher for encoding. The input information bit sequence is converted into an amplitude sequence with a preset probability distribution. The obtained amplitude sequence is then converted into an information bit sequence through a preset mapping method.

[0028] Module M1.2: The bit sequence obtained from module M1.1 and another part of the information bits are encoded by the outer hard decision FEC to obtain a bit sequence containing the check bits. The bit sequence then enters the interleaving module.

[0029] Module M1.3: The interleaved bit sequence is sequentially encoded and interleaved by inner-layer soft-decision FEC, and then modulated together with other bits to obtain the symbol sequence that each subcarrier needs to transmit.

[0030] Preferably, in module M1.1, the signal-to-noise ratio of each subcarrier is estimated by sending training symbols, the rate of each subcarrier is allocated according to the signal-to-noise ratio of each subcarrier, and the amplitude probability distribution of the output amplitude sequence is determined at the same time.

[0031] In module M1.3, the implementation of the inner soft-decision FEC coding is determined based on the bit error rate of each subcarrier and the bit error rate threshold of the outer hard-decision FEC.

[0032] Set up inner soft-decision FEC encoding and decoding for a bit, calculate the normalized generalized mutual information of the bit, and calculate the bit error rate after inner soft-decision FEC decoding based on the error correction capability of soft-decision FEC. Then, combine the bit error rate with other bits that do not participate in inner soft-decision FEC encoding and decoding.

[0033] If the final bit error rate meets the bit error rate threshold requirement of the outer hard decision FEC, determine the bits that need to be encoded by the inner soft decision FEC; if the final bit error rate does not meet the bit error rate threshold requirement of the outer hard decision FEC, add one bit for inner soft decision FEC encoding and decoding, and repeat the steps until the final bit error rate meets the bit error rate threshold requirement of the outer hard decision FEC.

[0034] Preferably, in module M2:

[0035] Module M2.1: Receives each carrier symbol sequence, performs soft decision to obtain the log-likelihood ratio, and after deinterleaving, enters the inner soft decision FEC decoding to obtain a near error-free bit sequence. This bit sequence is used as prior information to assist hard decision to obtain a bit sequence containing errors.

[0036] Module M2.2: After deinterleaving, the bit sequence obtained in module M2.1 enters the outer hard decision FEC decoding to obtain the error-corrected bit sequence;

[0037] Module M2.3: A portion of the bit sequence is reverse mapped to obtain an amplitude sequence. The amplitude sequence is decoded and converted into a bit sequence by a distribution matcher. It is then combined with another portion of the bit sequence to obtain the final bit sequence.

[0038] Preferably, in module M2.1, soft decision is performed on the bits that need to be encoded and decoded by inner soft decision FEC, and the log-likelihood ratio is calculated; hard decision is performed on other bits that do not need to be encoded and decoded by inner soft decision FEC, and they are only determined to be bit 0 or bit 1, and the hard decision is based on the bits after inner soft decision FEC decoding as a priori conditions.

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] 1. This invention proposes a joint modulation and coding method in a digital multi-carrier system, which relates to the field of coherent optical communication applications and has the ability to modulate, code, demodulate, and decode bit information;

[0041] 2. This invention designs a method for joint modulation and coding of subcarriers, which can flexibly adjust the modulation and coding parts of each subcarrier according to channel conditions, and better achieve a trade-off between performance and complexity;

[0042] 3. This invention is easy to implement, convenient to use, and has low implementation complexity, thus overcoming the shortcomings of existing technologies. Attached Figure Description

[0043] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0044] Figure 1 This is a schematic diagram of the structure for encoding and modulation when the present invention is applied to the transmitting end of coherent optical fiber communication;

[0045] Figure 2 This is a schematic diagram of the structure for demodulation and decoding when the present invention is applied to a coherent optical fiber communication receiver.

[0046] Figure 3 This is a schematic diagram illustrating the performance of the present invention applied to a coherent optical fiber transmission simulation system. Detailed Implementation

[0047] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all fall within the scope of protection of the present invention.

[0048] Example 1:

[0049] This invention relates to the technical field of modulation and coding in coherent optical communication systems. It provides a modulation and coding scheme method for multiple carriers in a coherent optical communication digital multi-carrier system, comprising the following steps: Transmitter encoding and modulation step: encoding and digitally modulating the input information bit sequence to obtain a symbol sequence; Receiver demodulation and decoding step: digitally demodulating and decoding the received symbols to obtain the information bit sequence. This invention allows for flexible adjustment of the modulation and coding portions of each subcarrier according to channel conditions, achieving a better trade-off between performance and complexity.

[0050] This invention provides a joint modulation and coding method for coherent optical communication digital multicarrier systems. This invention is applied to modulation and coding technology in coherent optical communication systems and relates to the field of optical fiber communication applications. By designing a joint modulation and coding method for subcarriers, the modulation and coding parts of each subcarrier can be flexibly adjusted according to channel conditions, achieving a better trade-off between performance and complexity.

[0051] According to the present invention, a joint modulation and coding method is provided in a coherent optical communication digital multicarrier system, such as... Figures 1-3 As shown, it includes:

[0052] Step S1: Transmitter encoding and modulation: After encoding and digitally modulating the input information bit sequence, a symbol sequence is obtained;

[0053] Specifically, in step S1:

[0054] Step S1.1: After the information bit sequence is converted from serial to parallel, a portion of the information bits enter the distribution matcher for encoding. The input information bit sequence is converted into an amplitude sequence with a preset probability distribution. The obtained amplitude sequence is then converted into an information bit sequence through a preset mapping method.

[0055] Step S1.2: The bit sequence obtained in step S1.1 and another part of the information bits are encoded by the outer hard decision FEC to obtain a bit sequence containing the check bits. The bit sequence then enters the interleaving module.

[0056] Step S1.3: After interleaving, a portion of the bit sequence is sequentially encoded and interleaved using inner-layer soft-decision FEC, and then modulated together with other bits to obtain the symbol sequence that each subcarrier needs to transmit.

[0057] Specifically, in step S1.1, the signal-to-noise ratio of each subcarrier is estimated by sending training symbols, the rate of each subcarrier is allocated according to the signal-to-noise ratio of each subcarrier, and the amplitude probability distribution of the output amplitude sequence is determined at the same time.

[0058] In step S1.3, the implementation of the inner soft-decision FEC coding is determined based on the bit error rate of each subcarrier and the bit error rate threshold of the outer hard-decision FEC.

[0059] Set up inner soft-decision FEC encoding and decoding for a bit, calculate the normalized generalized mutual information of the bit, and calculate the bit error rate after inner soft-decision FEC decoding based on the error correction capability of soft-decision FEC. Then, combine the bit error rate with other bits that do not participate in inner soft-decision FEC encoding and decoding.

[0060] If the final bit error rate meets the bit error rate threshold requirement of the outer hard decision FEC, determine the bits that need to be encoded by the inner soft decision FEC; if the final bit error rate does not meet the bit error rate threshold requirement of the outer hard decision FEC, add one bit for inner soft decision FEC encoding and decoding, and repeat the steps until the final bit error rate meets the bit error rate threshold requirement of the outer hard decision FEC.

[0061] Step S2: Demodulation and decoding at the receiving end. After digital demodulation and decoding error correction of the received symbols, the information bit sequence is obtained.

[0062] Specifically, in step S2:

[0063] Step S2.1: Receive each carrier symbol sequence, perform soft decision to obtain the log-likelihood ratio, and after deinterleaving, enter the inner soft decision FEC decoding to obtain a near error-free bit sequence. This bit sequence is used as prior information to assist hard decision to obtain a bit sequence containing errors.

[0064] Step S2.2: After deinterleaving, the bit sequence obtained in step S2.1 enters the outer hard decision FEC decoding to obtain the error-corrected bit sequence;

[0065] Step S2.3: A portion of the bit sequence is reverse mapped to obtain an amplitude sequence. The amplitude sequence is decoded and converted into a bit sequence by a distribution matcher. Then, it is combined with another portion of the bit sequence to obtain the final bit sequence.

[0066] Specifically, in step S2.1, soft decision is made for the bits that need to be encoded and decoded by inner soft decision FEC, and the log-likelihood ratio is calculated; hard decision is made for other bits that do not need to be encoded and decoded by inner soft decision FEC, and they are only determined to be bit 0 or bit 1, and the hard decision is based on the bits after inner soft decision FEC decoding as a priori conditions.

[0067] Example 2:

[0068] Example 2 is a preferred embodiment of Example 1, and is used to illustrate the present invention in more detail.

[0069] The present invention also provides a joint modulation and coding system in a coherent optical communication digital multicarrier system. The joint modulation and coding system in the coherent optical communication digital multicarrier system can be implemented by executing the process steps of the joint modulation and coding method in the coherent optical communication digital multicarrier system. That is, those skilled in the art can understand the joint modulation and coding method in the coherent optical communication digital multicarrier system as a preferred embodiment of the joint modulation and coding system in the coherent optical communication digital multicarrier system.

[0070] According to the present invention, a joint modulation and coding system in a coherent optical communication digital multicarrier system includes:

[0071] Module M1: Transmitter encoding and modulation, which encodes and digitally modulates the input information bit sequence to obtain a symbol sequence;

[0072] Specifically, in module M1:

[0073] Module M1.1: After the information bit sequence is converted from serial to parallel, a portion of the information bits enter the distribution matcher for encoding. The input information bit sequence is converted into an amplitude sequence with a preset probability distribution. The obtained amplitude sequence is then converted into an information bit sequence through a preset mapping method.

[0074] Module M1.2: The bit sequence obtained from module M1.1 and another part of the information bits are encoded by the outer hard decision FEC to obtain a bit sequence containing the check bits. The bit sequence then enters the interleaving module.

[0075] Module M1.3: The interleaved bit sequence is sequentially encoded and interleaved by inner-layer soft-decision FEC, and then modulated together with other bits to obtain the symbol sequence that each subcarrier needs to transmit.

[0076] Specifically, in module M1.1, the signal-to-noise ratio of each subcarrier is estimated by sending training symbols, the rate of each subcarrier is allocated according to the signal-to-noise ratio of each subcarrier, and the amplitude probability distribution of the output amplitude sequence is determined at the same time.

[0077] In module M1.3, the implementation of the inner soft-decision FEC coding is determined based on the bit error rate of each subcarrier and the bit error rate threshold of the outer hard-decision FEC.

[0078] Set up inner soft-decision FEC encoding and decoding for a bit, calculate the normalized generalized mutual information of the bit, and calculate the bit error rate after inner soft-decision FEC decoding based on the error correction capability of soft-decision FEC. Then, combine the bit error rate with other bits that do not participate in inner soft-decision FEC encoding and decoding.

[0079] If the final bit error rate meets the bit error rate threshold requirement of the outer hard decision FEC, determine the bits that need to be encoded by the inner soft decision FEC; if the final bit error rate does not meet the bit error rate threshold requirement of the outer hard decision FEC, add one bit for inner soft decision FEC encoding and decoding, and repeat the steps until the final bit error rate meets the bit error rate threshold requirement of the outer hard decision FEC.

[0080] Module M2: Receiver demodulation and decoding. After digital demodulation and decoding error correction of the received symbols, the information bit sequence is obtained.

[0081] Specifically, in module M2:

[0082] Module M2.1: Receives each carrier symbol sequence, performs soft decision to obtain the log-likelihood ratio, and after deinterleaving, enters the inner soft decision FEC decoding to obtain a near error-free bit sequence. This bit sequence is used as prior information to assist hard decision to obtain a bit sequence containing errors.

[0083] Module M2.2: After deinterleaving, the bit sequence obtained in module M2.1 enters the outer hard decision FEC decoding to obtain the error-corrected bit sequence;

[0084] Module M2.3: A portion of the bit sequence is reverse mapped to obtain an amplitude sequence. The amplitude sequence is decoded and converted into a bit sequence by a distribution matcher. It is then combined with another portion of the bit sequence to obtain the final bit sequence.

[0085] Specifically, in module M2.1, soft decision is performed on the bits that need to be encoded and decoded by inner soft decision FEC, and the log-likelihood ratio is calculated; hard decision is performed on other bits that do not need to be encoded and decoded by inner soft decision FEC, and they are only determined to be bit 0 or bit 1, and the hard decision is based on the bits after inner soft decision FEC decoding as a priori conditions.

[0086] Example 3:

[0087] Example 3 is a preferred example of Example 1, and is used to illustrate the present invention in more detail.

[0088] This invention discloses a joint modulation and coding method in a multi-carrier system of a coherent optical communication system, such as... Figure 1 and Figure 2 As shown, the process includes the following steps: Transmitter encoding and modulation: After encoding and digitally modulating the input information bit sequence, a symbol sequence is obtained. Receiver demodulation and decoding: After digitally demodulating and decoding the received symbols, an information bit sequence is obtained.

[0089] The transmitter coding and modulation steps are as follows Figure 1 As shown, the process includes the following steps: Step S1: After the information bit sequence undergoes serial-to-parallel conversion, a portion of the information bits enters the Distribution Matcher (DM) for encoding. The input bit sequence is converted into an amplitude sequence with a certain probability distribution. The obtained amplitude sequence is then transformed back into a bit sequence through a specific mapping method. The encoding of the DM is determined by the Signal-to-Noise Ratio (SNR) of each subcarrier. By transmitting training symbols, the rate of each subcarrier is allocated based on its SNR, and the amplitude probability distribution of the output amplitude sequence is determined simultaneously.

[0090] Step S2: The bit sequence obtained in step S1 and another part of the information bits are encoded by outer hard-decision (HD) FEC (Forward Error Correction) to obtain a bit sequence containing parity bits. The bit sequence then enters the interleaving module.

[0091] Step S3: After interleaving, a portion of the bit sequence is sequentially encoded and interleaved using inner soft-decision (SD) FEC, and then modulated together with other bits to obtain the symbol sequence to be transmitted on each subcarrier. The implementation of inner SD-FEC encoding is determined based on the bit error rate (BER) of each subcarrier in S1 and the BER threshold of outer HD-FEC.

[0092] Specifically, we first assume that inner SD-FEC encoding and decoding are performed on a single bit, calculate the Normalized Generalized Mutual Information (NGMI) of that bit, and then determine the BER (Best Error Rate) after inner SD-FEC decoding based on the error correction capability of SD-FEC. Then, we combine this with other bits that do not participate in inner SD-FEC encoding and decoding to calculate the final BER.

[0093] If the final BER meets the BER threshold requirement of the outer HD-FEC, the bits that need to be encoded by the inner SD-FEC are determined; if the final BER does not meet the BER threshold requirement of the outer HD-FEC, an additional bit is added for inner SD-FEC encoding and decoding, and the above steps are repeated until the final BER meets the BER threshold requirement of the outer HD-FEC.

[0094] Demodulation and decoding at the receiving end, such as Figure 2 As shown, it includes the following steps:

[0095] Step S4: The received carrier symbol sequences are first subjected to soft decision to obtain the log-likelihood ratio (LLR). After deinterleaving, they enter the inner SD-FEC decoding to obtain a near error-free bit sequence. This bit sequence is used as prior information to assist hard decision to obtain a bit sequence containing errors.

[0096] For the bits that require inner SD-FEC encoding and decoding as determined in step S3, a soft decision is made, i.e., the LLR is calculated. For other bits that do not require inner SD-FEC encoding and decoding, a hard decision is made, i.e., it is only necessary to determine whether it is bit 0 or bit 1, and the hard decision is based on the bits after inner SD-FEC decoding as a priori conditions.

[0097] Step S5: After the bit sequence obtained in step S4 is deinterleaved, all the bit sequences enter the outer HD-FEC decoding to obtain the error-corrected bit sequence;

[0098] Step S6: A portion of the bit sequence is reverse mapped to obtain an amplitude sequence. The amplitude sequence is then converted into a bit sequence by DM decoding and combined with another portion of the bit sequence to obtain the final bit sequence.

[0099] This invention also provides an embodiment of the performance of the designed algorithm applied to a digital multicarrier system, such as... Figure 3 The diagram illustrates the transmission performance when the two subcarriers have inconsistent performance. The channel is an additive white Gaussian noise channel, and the horizontal axis represents the channel ratio of the two subcarriers. The two curves represent the BER performance before and after the inner SD-FEC (Pre-FEC). The modulation format is a probabilistically shaped 64-ary quadrature amplitude modulation (64QAM) signal. Figure 3 As can be seen, the proposed scheme can effectively correct transmission errors.

[0100] Those skilled in the art will understand that, in addition to implementing the system, apparatus, and their modules provided by this invention in purely computer-readable program code, the same program can be implemented in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers, and embedded microcontrollers by logically programming the method steps. Therefore, the system, apparatus, and their modules provided by this invention can be considered a hardware component, and the modules included therein for implementing various programs can also be considered structures within the hardware component; alternatively, modules for implementing various functions can be considered both software programs implementing the method and structures within the hardware component.

[0101] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

Claims

1. A joint modulation and coding method in a coherent optical communication digital multicarrier system, characterized in that, include: Step S1: Transmitter encoding and modulation: After encoding and digitally modulating the input information bit sequence, a symbol sequence is obtained; Step S2: Demodulation and decoding at the receiving end. After digital demodulation and decoding error correction of the received symbols, the information bit sequence is obtained. In step S1: Step S1.1: After the information bit sequence is converted from serial to parallel, a portion of the information bits enter the distribution matcher for encoding. The input information bit sequence is converted into an amplitude sequence with a preset probability distribution. The obtained amplitude sequence is then converted into an information bit sequence through a preset mapping method. Step S1.2: The bit sequence obtained in step S1.1 and another part of the information bits are encoded by the outer hard decision FEC to obtain a bit sequence containing the check bits. The bit sequence then enters the interleaving module. Step S1.3: After interleaving, a portion of the bit sequence is sequentially encoded and interleaved using inner-layer soft-decision FEC, and then modulated together with other bits to obtain the symbol sequence that each subcarrier needs to transmit; In step S2: Step S2.1: Receive each carrier symbol sequence, perform soft decision to obtain the log-likelihood ratio, and after deinterleaving, enter the inner soft decision FEC decoding to obtain a near error-free bit sequence. This bit sequence is used as prior information to assist hard decision to obtain a bit sequence containing errors. Step S2.2: After deinterleaving, the bit sequence obtained in step S2.1 enters the outer hard decision FEC decoding to obtain the error-corrected bit sequence; Step S2.3: A portion of the bit sequence is reverse mapped to obtain an amplitude sequence. The amplitude sequence is decoded and converted into a bit sequence by a distribution matcher. Then, it is combined with another portion of the bit sequence to obtain the final bit sequence.

2. The joint modulation and coding method in a coherent optical communication digital multicarrier system according to claim 1, characterized in that: In step S1.1, the signal-to-noise ratio of each subcarrier is estimated by sending training symbols, the rate of each subcarrier is allocated according to the signal-to-noise ratio of each subcarrier, and the amplitude probability distribution of the output amplitude sequence is determined at the same time. In step S1.3, the implementation of the inner soft-decision FEC coding is determined based on the bit error rate of each subcarrier and the bit error rate threshold of the outer hard-decision FEC. Set up inner soft-decision FEC encoding and decoding for a bit, calculate the normalized generalized mutual information of the bit, and calculate the bit error rate after inner soft-decision FEC decoding based on the error correction capability of soft-decision FEC. Then, combine the bit error rate with other bits that do not participate in inner soft-decision FEC encoding and decoding. If the final bit error rate meets the bit error rate threshold requirement of the outer hard decision FEC, determine the bits that need to be encoded by the inner soft decision FEC. If the final bit error rate does not meet the bit error rate threshold requirement of the outer hard decision FEC, add one bit for inner soft decision FEC encoding and decoding, and repeat the steps until the final bit error rate meets the bit error rate threshold requirement of the outer hard decision FEC.

3. The joint modulation and coding method in a coherent optical communication digital multicarrier system according to claim 1, characterized in that: In step S2.1, soft decision is performed on the bits that need to be encoded and decoded by inner soft decision FEC, and the log-likelihood ratio is calculated; hard decision is performed on other bits that do not need to be encoded and decoded by inner soft decision FEC, and they are only determined to be bit 0 or bit 1, and the hard decision is based on the bits after inner soft decision FEC decoding as a priori conditions.

4. A joint modulation and coding system in a coherent optical communication digital multicarrier system, characterized in that, include: Module M1: Transmitter encoding and modulation, which encodes and digitally modulates the input information bit sequence to obtain a symbol sequence; Module M2: Receiver demodulation and decoding. After digital demodulation and decoding error correction of the received symbols, the information bit sequence is obtained. In module M1: Module M1.1: After the information bit sequence is converted from serial to parallel, a portion of the information bits enter the distribution matcher for encoding. The input information bit sequence is converted into an amplitude sequence with a preset probability distribution. The obtained amplitude sequence is then converted into an information bit sequence through a preset mapping method. Module M1.2: The bit sequence obtained from module M1.1 and another part of the information bits are encoded by the outer hard decision FEC to obtain a bit sequence containing the check bits. The bit sequence then enters the interleaving module. Module M1.3: The interleaved bit sequence is sequentially encoded and interleaved by inner soft-decision FEC, and then modulated together with other bits to obtain the symbol sequence that each subcarrier needs to transmit; In module M2: Module M2.1: Receives each carrier symbol sequence, performs soft decision to obtain the log-likelihood ratio, and after deinterleaving, enters the inner soft decision FEC decoding to obtain a near error-free bit sequence. This bit sequence is used as prior information to assist hard decision to obtain a bit sequence containing errors. Module M2.2: After deinterleaving, the bit sequence obtained in module M2.1 enters the outer hard decision FEC decoding to obtain the error-corrected bit sequence; Module M2.3: A portion of the bit sequence is reverse mapped to obtain an amplitude sequence. The amplitude sequence is decoded and converted into a bit sequence by a distribution matcher. It is then combined with another portion of the bit sequence to obtain the final bit sequence.

5. The joint modulation and coding system in a coherent optical communication digital multicarrier system according to claim 4, characterized in that: In module M1.1, the signal-to-noise ratio of each subcarrier is estimated by sending training symbols, the rate of each subcarrier is allocated according to the signal-to-noise ratio of each subcarrier, and the amplitude probability distribution of the output amplitude sequence is determined at the same time. In module M1.3, the implementation of the inner soft-decision FEC coding is determined based on the bit error rate of each subcarrier and the bit error rate threshold of the outer hard-decision FEC. Set up inner soft-decision FEC encoding and decoding for a bit, calculate the normalized generalized mutual information of the bit, and calculate the bit error rate after inner soft-decision FEC decoding based on the error correction capability of soft-decision FEC. Then, combine the bit error rate with other bits that do not participate in inner soft-decision FEC encoding and decoding. If the final bit error rate meets the bit error rate threshold requirement of the outer hard decision FEC, determine the bits that need to be encoded by the inner soft decision FEC. If the final bit error rate does not meet the bit error rate threshold requirement of the outer hard decision FEC, add one bit for inner soft decision FEC encoding and decoding, and repeat the steps until the final bit error rate meets the bit error rate threshold requirement of the outer hard decision FEC.

6. The joint modulation and coding system in a coherent optical communication digital multicarrier system according to claim 4, characterized in that: In module M2.1, soft decision is performed on the bits that need to be encoded and decoded by inner soft decision FEC, and the log-likelihood ratio is calculated; hard decision is performed on other bits that do not need to be encoded and decoded by inner soft decision FEC, and they are only determined to be bit 0 or bit 1, and the hard decision is based on the bits after inner soft decision FEC decoding as a priori conditions.

Images