CN109217937B - Data receiving method and receiving device - Google Patents
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Abstract
The invention discloses a data receiving method and a data receiving device applied to an optical FTN-PAM4 system, wherein the data receiving method is mainly characterized in that the data receiving method adopts a combined algorithm based on an improved frequency domain equalizer and maximum likelihood sequence detectionThe method is used for eliminating intersymbol interference, wherein the frequency domain equalizer for improving signals comprises a traditional frequency domain equalizer and a frequency domain post filter, and the traditional frequency domain equalizer and the frequency domain post filter are combined, and the process specifically comprises the following steps: firstly, carrying out fast Fourier transform on received data to generate a frequency domain signal; then dividing the generated frequency domain signal by a matrix H to obtain an equalized frequency domain signal, wherein the matrix H is equal to a frequency domain channel matrix HChannelFrequency domain division post-filtering matrix HPostFilter(ii) a And finally, performing fast Fourier inverse transformation on the equalized frequency domain signal to obtain an equalized time domain signal. The invention adopts a simple frequency domain equalization algorithm to replace a time domain feedforward equalizer and post-filtering in the traditional combined algorithm, achieves higher interference elimination performance and has lower algorithm complexity.
Description
Technical Field
The invention relates to the technical field of optical communication, in particular to a data receiving method and a data receiving device applied to an optical FTN-PAM4 system.
Background
In recent years, with the rapid development of data centers, the transmission rate of short-distance optical interconnection systems reaches 400Gbit/s, and is expected to reach 1Tbit/s in 2020. Multi-order modulation is widely studied in research and commercial fields in order to transmit higher-rate data within a limited bandwidth. The 4-order pulse amplitude modulation (PAM4) has been adopted by IEEE p802.3bs as the 200G and 400G short-range optical interconnect standards. The 4 x 50-Gbit/s and 8 x 50-Gbit/s optical PAM4 systems are options for short-haul optical interconnect systems 200-G and 400-G interfaces, respectively. Short-haul optical interconnects typically require the use of low-cost, low-power systems. Therefore, the 50-Gbit/s optical PAM4 system tends to employ 10-G devices. But due to the bandwidth limitation of 10-G devices, the receiving end needs to compensate the high frequency damage of the received signal by using a Digital Signal Processing (DSP) algorithm. Meanwhile, the complexity of a digital signal processing algorithm needs to be controlled to reduce the power consumption of the system.
A high-spectral efficiency super-nyquist PAM4(FTN-PAM4) system is used for a bandwidth-limited system to transmit a larger capacity signal. However, the FTN-PAM4 system requires complex DSP algorithms to compensate for the severe intersymbol interference caused by the bandwidth limitation. As is well known, a feed forward equalizer is a commonly used algorithm for compensating for intersymbol interference. The feed forward equalizer, however, enhances the in-band noise while compensating for inter-symbol interference. A joint algorithm based on a feed forward equalizer, a post filter and maximum likelihood sequence detection can simultaneously handle intersymbol interference and enhanced in-band noise. However, in the algorithm, in order to effectively compensate for inter-carrier interference and suppress timing errors, a feed-forward equalizer with a half symbol interval and a large number of taps is required, so that the combined algorithm has high complexity and limits the application of the FTN-PAM4 system in a short-range optical interconnect system.
A frequency domain equalizer is also a DSP algorithm commonly used in the art, which has the advantage that the algorithm complexity is much lower than the feedforward equalizer algorithm in the joint algorithm described above. The conventional frequency domain equalizer may use the estimated channel matrix HChannelChannel impairments are compensated for, but a conventional frequency domain equalizer also enhances in-band noise. Currently, no joint algorithm based on frequency domain equalization exists that solves the problems of intersymbol interference and enhanced inband noise at the same time.
Disclosure of Invention
The technical problem to be solved by the invention is to provide a data receiving method and a receiving device, which are used for solving the problems of high algorithm complexity or poor performance of the existing FTN-PAM4 signal receiving method and receiving device.
In order to solve the above technical problem, the present invention provides a data receiving method, including the steps of:
1) directly detecting a received optical FTN-PAM4 signal, and converting the optical FTN-PAM4 signal into an analog electrical signal;
2) converting the analog electrical signal to a digital FTN-PAM4 signal;
3) performing intersymbol interference elimination on the digital FTN-PAM4 signal to output a digital PAM4 signal;
4) and decoding the digital PAM4 signal to obtain received data in a bit sequence form.
It is characterized in that the preparation method is characterized in that,
the process of performing intersymbol interference cancellation on the digital FTN-PAM4 signal to output a digital PAM4 signal specifically includes:
3-1) performing improved frequency domain equalizer processing on the digital FTN-PAM4 signal;
3-2) carrying out maximum likelihood sequence detection on the equalized signal to output a digital PAM4 signal;
step 3-1) carrying out improved frequency domain equalizer processing on the digital FTN-PAM4 signal, adopting a traditional frequency domain equalizer and a frequency domain post filter, and combining the traditional frequency domain equalizer and the frequency domain post filter, wherein the process specifically comprises the following steps:
3-11) carrying out fast Fourier transform on the digital FTN-PAM4 signal to transform the signal into a frequency domain signal;
3-12) carrying out frequency domain equalization on the frequency domain signal subjected to the fast Fourier transform; transfer matrix H-H for frequency domain equalizationChannel/HPostFilter，HChannelFor the estimated frequency channel matrix, HPostFilterIs the frequency domain transfer matrix of the frequency domain postfilter;
3-13) performing inverse fast Fourier transform on the signal after frequency domain equalization to recover an equalized time domain PAM4 signal.
The method is mainly characterized in that a combined algorithm based on an improved frequency domain equalizer and maximum likelihood sequence detection is adopted in the step 3) to eliminate the intersymbol interference. The conventional frequency domain equalizer may use the estimated frequency channel matrix HChannelThe invention firstly changes the traditional method of post-filtering in the time domain and adopts frequency domain transmission to reduce the enhanced in-band noiseThe transition matrix is HPostFilterThen the transfer matrix of the digital FTN-PAM4 signal is H ═ H by combining the conventional frequency domain equalizer with the above frequency domain post-filterChannel/HPostFilterThe improved frequency domain equalization of (2) simplifies the structure of the frequency domain equalizer.
Tests prove that the improved frequency domain equalizer can realize the same functions of a feedforward equalizer and a post filter of a combined algorithm in the background technology, and the known intersymbol interference is inevitably introduced when the improved frequency domain equalization is carried out, but the interference can be easily eliminated through maximum likelihood sequence detection.
Further, the process of converting the analog electrical signal into the digital FTN-PAM4 signal in step 2) specifically includes:
2-1) carrying out analog-to-digital conversion on the analog electric signal to generate a digital signal;
2-2) performing serial-to-parallel conversion on the digital signals to generate parallel digital signals;
2-3) removing the prefix and suffix output digital FTN-PAM4 signals of the parallel digital signal.
Further, the process of decoding the digital PAM4 signal after the inter-symbol interference is removed in step 4) to obtain received data in the form of a bit sequence specifically includes:
4-1) decoding the digital PAM4 signal;
4-2) performing parallel-to-serial conversion on the decoded data to generate received data in the form of a bit sequence.
Further, step 3-2) carries out maximum likelihood sequence detection on the equalized signals, and a Viterbi algorithm is adopted.
The present invention also provides a data receiving apparatus, the apparatus comprising:
the direct detection unit is used for directly detecting the received optical FTN-PAM4 signal and converting the optical FTN-PAM4 signal into an analog electrical signal;
an FTN-PAM4 signal conversion unit for converting the analog electrical signal into a digital FTN-PAM4 signal;
an inter-symbol interference cancellation unit, configured to perform inter-symbol interference cancellation on the digital FTN-PAM4 signal to output a digital PAM4 signal;
a decoding unit, configured to decode the digital PAM4 signal after intersymbol interference cancellation, to obtain received data in a bit sequence form;
it is characterized in that the preparation method is characterized in that,
the intersymbol interference cancellation unit includes:
a frequency domain equalization subunit, configured to perform improved frequency domain equalization on the digital FTN-PAM4 signal to eliminate inter-symbol interference introduced by the optical FTN-PAM4 system, reduce enhanced in-band noise, and introduce known inter-symbol interference;
a maximum likelihood sequence detection subunit, configured to perform maximum likelihood sequence detection on the equalized signal to output a digital PAM4 signal, so as to eliminate introduced known inter-symbol interference and recover a digital PAM4 signal;
the frequency domain equalizing subunit includes:
the fast Fourier transform module is used for carrying out fast Fourier transform on the digital FTN-PAM4 signal and transforming the signal into a frequency domain signal;
the frequency domain equalization module is used for carrying out frequency domain equalization on the frequency domain signal subjected to the fast Fourier transform; transfer matrix H-H for frequency domain equalizationChannel/HPostFilter，HChannelFor the estimated frequency channel matrix, HPostFilterIs the frequency domain transfer matrix of the frequency domain postfilter;
and the inverse fast Fourier transform module is used for performing inverse fast Fourier transform on the signal after frequency domain equalization to recover the equalized time domain PAM4 signal.
Further, the FTN-PAM4 signal conversion unit includes:
the analog-to-digital conversion subunit is used for performing analog-to-digital conversion on the analog electric signal to generate a digital signal;
the serial-parallel conversion subunit is used for performing serial-parallel conversion on the digital signals to generate parallel digital signals;
a prefix and suffix removal subunit for removing prefix and suffix output digital FTN-PAM4 signals of the parallel digital signal.
Further, the decoding unit includes:
a PAM4 decoding subunit for decoding the digital PAM4 signal;
and the parallel-serial conversion subunit is used for performing parallel-serial conversion on the decoded data to generate the received data in the form of a bit sequence.
Further, the maximum likelihood sequence detection subunit performs maximum likelihood sequence detection on the equalized signal by using a Viterbi algorithm.
Compared with the prior art, the invention has the following beneficial effects:
the invention provides a data receiving method and a receiving device based on an improved frequency domain equalizer and a maximum likelihood sequence detection combined algorithm, wherein the combined algorithm can simultaneously process intersymbol interference and enhanced in-band noise of an FTN-PAM4 system, and achieves similar or even more superior performance based on a feedforward equalizer, a post filter and the maximum likelihood detection combined algorithm, but the complexity of the adopted frequency domain equalizer algorithm is far lower than that of the feedforward equalizer and the post filter, so the data receiving method and the receiving device can also greatly reduce the complexity of the algorithm; in summary, compared with a combined algorithm based on a feedforward equalizer, a post filter and maximum likelihood detection, the data receiving method and the data receiving device can greatly reduce the complexity of the algorithm, and compared with the traditional frequency domain equalizer algorithm, the performance of the algorithm can be greatly improved.
Drawings
Fig. 1 is a block diagram of a data receiving apparatus according to a first embodiment of the present invention;
fig. 2 is a flowchart of a data receiving method according to a second embodiment of the present invention;
FIG. 3 (a) is a block diagram of a joint algorithm based on a feed-forward equalizer, a post-filter, and maximum likelihood sequence detection;
FIG. 3 (b) is a structural diagram of the improved frequency domain equalizer and maximum likelihood sequence detection combined algorithm based on the present invention;
FIG. 4 (a) is an eye diagram of an FTN-PAM4 signal received by an optical FTN-PAM4 system (without DSP algorithm processing);
fig. 4 (b) is an eye diagram of the FTN-PAM4 signal output via a conventional frequency domain equalizer;
fig. 4 (c) is an eye diagram of the FTN-PAM4 signal output by the improved frequency domain equalizer of the present invention;
FIG. 5 is a performance comparison graph of bit error rates exhibited by a data receiving method based on the improved frequency domain equalizer and the maximum likelihood sequence detection combined algorithm of the present invention and a conventional frequency domain equalizer applied to a 56-Gbit/s FTN-PAM4 system, respectively;
FIG. 6 is a performance comparison graph of bit error rates exhibited by a conventional data receiving method based on a feedforward equalizer, a post filter and a maximum likelihood sequence detection combined algorithm, which is applied to a 56-Gbit/s FTN-PAM4 system, and which is based on an improved frequency domain equalizer and a maximum likelihood sequence detection combined algorithm according to the present invention.
Detailed Description
The invention is explained in further detail with reference to the figures and the corresponding examples. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not limit the scope of the invention.
Example one
A data receiving apparatus according to a first embodiment has a structure as shown in fig. 1, and includes a direct detection unit 11, an FTN-PAM4 signal conversion unit 12, an inter-symbol interference cancellation unit 13, and a decoding unit 14. Wherein, the direct detection unit 11, the FTN-PAM4 signal conversion unit 12, the inter-symbol interference cancellation unit 13, and the decoding unit 14 are connected in sequence.
The direct detection unit 11 is configured to directly detect the received optical FTN-PAM4 signal, and convert the optical FTN-PAM4 signal into an analog electrical signal.
The FTN-PAM4 signal conversion unit 12 is configured to convert the analog electrical signal into a digital FTN-PAM4 signal. In this embodiment, the FTN-PAM4 signal conversion unit 12 includes an analog-to-digital conversion subunit 121, a serial-to-parallel conversion subunit 122, and a prefix and suffix removal subunit 123. Wherein, the serial-to-parallel converting subunit 122 is connected with the analog-to-digital converting subunit 121 and the prefix and suffix removing subunit 123, respectively. The analog-to-digital conversion subunit 121 is configured to perform analog-to-digital conversion on the analog electrical signal to generate a digital signal; the serial-parallel conversion subunit 122 is configured to perform serial-parallel conversion on the digital signal to generate a parallel digital signal; the prefix and suffix removal subunit 123 is configured to remove prefixes and suffixes of the digital signal, and generate a digital FTN-PAM4 signal.
The intersymbol interference elimination unit 13 is configured to perform intersymbol interference elimination on the FTN-PAM4 signal to output a digital PAM4 signal. In this embodiment, the inter-symbol interference cancellation unit 13 includes a frequency domain equalization subunit 131 and a maximum likelihood sequence detection subunit 132. Wherein the frequency domain equalizing sub-unit 131 is connected to the maximum likelihood sequence detecting sub-unit 132. The frequency domain equalization subunit 131 is configured to perform improved frequency domain equalization on the digital FTN-PAM4 signal to eliminate inter-symbol interference introduced by the optical FTN-PAM4 system, reduce enhanced in-band noise, and introduce known inter-symbol interference; the maximum likelihood sequence detection subunit 132 is configured to perform maximum likelihood sequence detection on the equalized signal to output a digital PAM4 signal, so as to eliminate the introduced known intersymbol interference and recover a digital PAM4 signal. In this embodiment, the maximum likelihood sequence detection subunit 132 performs maximum likelihood sequence detection on the equalized signal by using the Viterbi algorithm.
In this embodiment, the frequency domain equalizing subunit 131 includes a fast fourier transform module 131a, a frequency domain equalizing module 131b, and an inverse fast fourier transform module 131c, which are connected in sequence. Wherein the fast Fourier transform module 131a is used for comparing the number FPerforming fast Fourier transform on the TN-PAM4 signal to transform the TN-PAM4 signal into a frequency domain signal; the frequency domain equalization module 131b is configured to perform frequency domain equalization on the frequency domain signal after the fast fourier transform; transfer matrix H-H for frequency domain equalizationChannel/HPostFilter，HChannelFor the estimated frequency channel matrix, HPostFilterIs the frequency domain transfer matrix of the frequency domain postfilter; the inverse fast fourier transform module 131c is configured to perform inverse fast fourier transform on the frequency-domain equalized signal, and recover the equalized time-domain PAM4 signal.
The decoding unit 14 is configured to decode the PAM4 signal data after the inter-symbol interference is removed, and obtain received data in the form of a bit sequence. The decoding unit 14 includes a PAM4 decoding subunit 141 and a parallel-to-serial conversion subunit 142. Among them, PAM4 decoding subunit 141 is connected to parallel-to-serial converting subunit 142. A PAM4 decoding subunit 141 is used to decode the digital PAM4 signal; the parallel-to-serial conversion subunit 142 is configured to perform parallel-to-serial conversion on the decoded data, and generate received data in the form of a bit sequence.
Example two
A flow chart of a data receiving method according to the second embodiment is shown in fig. 2, and includes the following steps:
and step s201, directly detecting the received optical FTN-PAM4 signal, and converting the optical FTN-PAM4 signal into an analog electrical signal.
And step s202, performing analog-to-digital conversion on the analog electric signal to generate a digital signal.
And step s203, performing serial-to-parallel conversion on the digital signal to generate a parallel signal.
And step s204, removing prefixes and suffixes of the parallel signals to generate parallel FTN-PAM4 signals.
And step s205, performing fast fourier transform on the parallel FTN-PAM4 signal to transform the parallel FTN-PAM4 signal into a frequency domain signal.
Step s206, performing frequency domain equalization on the data after the fast fourier transform; transfer matrix H-H for frequency domain equalizationChannel/HPostFilter，HChannelFor the estimated frequency channel matrix, HPostFilterIs the frequency domainThe frequency domain transfer matrix of the post-filter.
And step s207, performing inverse fast fourier transform on the frequency domain equalized data, and recovering an equalized time domain PAM4 signal.
In step s208, maximum likelihood sequence detection is performed on the signal output in step s 207.
In step s209, decision decoding is performed on the signal output by the maximum likelihood sequence detection.
Step s210, performing parallel-to-serial conversion on the data output by the decision decoding to generate received data formed by a bit sequence.
Fig. 3 is a comparison of the structure diagram of the combined algorithm based on the feed forward equalizer, the time domain post filter and the maximum likelihood sequence detection with the improved frequency domain equalizer and maximum likelihood sequence detection based on the present invention. The improved frequency domain equalizer of the invention combines the traditional frequency domain equalizer and the frequency domain post filter, and the specific combination mode is as follows: improved frequency domain equalizer using a transfer matrix H ═ HChannel/HPostFilter，HChannelFor the estimated frequency channel matrix, HPostFilterThis combination also simplifies the structure of a conventional frequency domain equalizer in combination with a frequency domain post-filter, which is the frequency domain transfer matrix of the frequency domain post-filter. The frequency domain equalizer and maximum likelihood sequence detection combined algorithm based on the improvement not only can replace the traditional combined algorithm based on the feedforward equalizer, the post filter and the maximum likelihood sequence detection, but also has great advantages in algorithm complexity, and the comparison data is shown in figure 6 (the description of figure 6 is shown below).
Fig. 4 is a diagram for comparing a difference in data processing performance between the conventional frequency domain equalizer and the improved frequency domain equalizer of the present invention. As reflected in fig. 4 (a), the received FTN-PAM4 signal exhibits a 7-layer blurred eye pattern due to severe intersymbol interference and noise. As reflected in fig. 4 (b), the recovered PAM4 signal exhibits a 4-layer blurred eye pattern due to enhanced in-band noise, with the conventional frequency domain equalizer compensating for inter-symbol interference. As reflected in fig. 4 (c), the recovered FTN-PAM4 signal has a clear 7-layer eye diagram by the improved frequency domain equalizer of the present invention dealing with both intersymbol interference caused by channel impairments and enhanced inband noise. Although known intersymbol interference is introduced, maximum likelihood detection can easily eliminate the introduced interference. Fig. 4 shows that, as a whole, the data receiving method and apparatus of the present invention have better performance than the conventional frequency domain equalizer.
Fig. 5 is a performance comparison graph of bit error rates exhibited by the data receiving method based on the improved frequency domain equalizer and the maximum likelihood sequence detection combined algorithm of the present invention and the conventional frequency domain equalizer applied to the 56-Gbit/s FTN-PAM4 system, respectively, wherein the corresponding frequency domain post-filter coefficient is set to 0.8.
The two lower broken lines in fig. 5 respectively show the bit error rate performance of the 56-Gbit/s optical FTN-PAM4 system based on the improved frequency domain equalizer and the maximum likelihood sequence detection joint algorithm after the 10-km standard single mode fiber is transmitted with or without (BTB), and as can be seen from the variation trend of the two broken lines, the difference between the two broken lines is small, which indicates that the system is really feasible.
The broken line on fig. 5 shows that after a 56-Gbit/s optical FTN-PAM4 system using a conventional frequency domain equalizer transmits a 10-km standard single mode fiber, when the received optical power is lower than-9 dBm, the error rate does not reach a 7% forward error correction threshold; when the receiving optical power of the 56-Gbit/s optical FTN-PAM4 system adopting the method is larger than-12 dBm, the error rate is lower than 7 percent of forward error correction threshold. The method of the present invention is shown to have a great advantage over conventional frequency domain equalizers in dealing with severe impairments in FTN-PAM4 systems.
FIG. 6 is a performance comparison graph of bit error rates exhibited by a conventional data receiving method based on a feedforward equalizer, a post filter and a maximum likelihood sequence detection combined algorithm, which is applied to a 56-Gbit/s FTN-PAM4 system, and which is based on an improved frequency domain equalizer and a maximum likelihood sequence detection combined algorithm according to the present invention. In the conventional method, the feedforward equalizer can adopt a recursive least square adaptive algorithm or a least mean square adaptive algorithm to train the tap coefficient. The broken line in fig. 6 shows that the performance of the method of the present invention is superior to that of the conventional method using the least mean square adaptive algorithm, and is similar to that of the conventional method using the recursive least square adaptive algorithm. Meanwhile, the algorithm (frequency domain equalizer) of the method of the present invention has a complexity of multiplying each bit by 12 times, while the conventional method using the recursive least square adaptation algorithm (feedforward equalizer, post filter) has a complexity of multiplying each bit by 1428 times and the conventional method using the least mean square adaptation algorithm (feedforward equalizer, post filter) has a complexity of multiplying each bit by 93 times. Therefore, the algorithm complexity of the method is far lower than that of the traditional method.
The results shown in fig. 5 and fig. 6 can prove that the signal receiving method and apparatus based on the improved frequency domain equalizer and the maximum likelihood sequence detection joint algorithm of the present invention can simultaneously process the intersymbol interference and the enhanced inband noise of the FTN-PAM4 system. Compared with the traditional frequency domain equalizer, the invention has better performance; compared with the combined algorithm based on the feedforward equalizer, the post-filtering and the maximum likelihood detection, the invention has similar or even more excellent performance, but the complexity of the frequency domain equalizer is far lower than that of the feedforward equalizer and the post-filtering, so the complexity of the algorithm of the invention is greatly reduced.
Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, and the scope of the invention should not be limited to the embodiments described above.
Claims (6)
1. A data receiving method, said method comprising the steps of:
1) directly detecting a received optical FTN-PAM4 signal, and converting the optical FTN-PAM4 signal into an analog electrical signal;
2) converting the analog electrical signal to a digital FTN-PAM4 signal;
3) performing intersymbol interference elimination on the digital FTN-PAM4 signal to output a digital PAM4 signal;
4) decoding the digital PAM4 signal to obtain received data in a bit sequence form;
it is characterized in that the preparation method is characterized in that,
the process of performing intersymbol interference cancellation on the digital FTN-PAM4 signal to output a digital PAM4 signal specifically includes:
3-1) performing improved frequency domain equalizer processing on the digital FTN-PAM4 signal;
3-2) carrying out maximum likelihood sequence detection on the equalized signal to output a digital PAM4 signal;
step 3-1) carrying out improved frequency domain equalizer processing on the digital FTN-PAM4 signal, adopting a traditional frequency domain equalizer and a frequency domain post filter, and combining the traditional frequency domain equalizer and the frequency domain post filter, wherein the processing process specifically comprises the following steps:
3-11) carrying out fast Fourier transform on the digital FTN-PAM4 signal to transform the signal into a frequency domain signal;
3-12) carrying out frequency domain equalization on the frequency domain signal subjected to the fast Fourier transform; transfer matrix H-H for frequency domain equalizationChannel/HPostFilter，HChannelFor the estimated frequency channel matrix, HPostFilterIs the frequency domain transfer matrix of the frequency domain postfilter;
3-13) performing inverse fast Fourier transform on the signal after frequency domain equalization to recover an equalized time domain PAM4 signal;
the process of converting the analog electrical signal into the digital FTN-PAM4 signal in step 2) specifically includes:
2-1) carrying out analog-to-digital conversion on the analog electric signal to generate a digital signal;
2-2) performing serial-to-parallel conversion on the digital signals to generate parallel digital signals;
2-3) removing the prefix and suffix output digital FTN-PAM4 signals of the parallel digital signal.
2. The data receiving method according to claim 1, wherein the process of decoding the digital PAM4 signal after removing the inter-symbol interference in step 4) to obtain the received data in the form of a bit sequence specifically comprises:
4-1) decoding the digital PAM4 signal;
4-2) performing parallel-to-serial conversion on the decoded data to generate received data in the form of a bit sequence.
3. The data receiving method as claimed in claim 1, wherein the step 3-2) performs maximum likelihood sequence detection on the equalized signal using a Viterbi algorithm.
4. A data receiving apparatus, the apparatus comprising:
the direct detection unit is used for directly detecting the received optical FTN-PAM4 signal and converting the optical FTN-PAM4 signal into an analog electrical signal;
an FTN-PAM4 signal conversion unit for converting the analog electrical signal into a digital FTN-PAM4 signal;
an inter-symbol interference cancellation unit, configured to perform inter-symbol interference cancellation on the digital FTN-PAM4 signal to output a digital PAM4 signal;
a decoding unit, configured to decode the digital PAM4 signal after intersymbol interference cancellation, to obtain received data in a bit sequence form;
it is characterized in that the preparation method is characterized in that,
the intersymbol interference cancellation unit includes:
a frequency domain equalization subunit, configured to perform improved frequency domain equalization on the digital FTN-PAM4 signal to eliminate inter-symbol interference introduced by the optical FTN-PAM4 system, reduce enhanced in-band noise, and introduce known inter-symbol interference;
a maximum likelihood sequence detection subunit, configured to perform maximum likelihood sequence detection on the equalized signal to output a digital PAM4 signal, so as to eliminate introduced known inter-symbol interference and recover a digital PAM4 signal;
the frequency domain equalizing subunit includes:
the fast Fourier transform module is used for carrying out fast Fourier transform on the digital FTN-PAM4 signal and transforming the signal into a frequency domain signal;
the frequency domain equalization module is used for carrying out frequency domain equalization on the frequency domain signal subjected to the fast Fourier transform; transfer matrix H-H for frequency domain equalizationChannel/HPostFilter，HChannelFor the estimated frequency channel matrix, HPostFilterIs the frequency domain transfer matrix of the frequency domain postfilter;
the inverse fast Fourier transform module is used for performing inverse fast Fourier transform on the signal after frequency domain equalization to recover the equalized time domain PAM4 signal;
the FTN-PAM4 signal conversion unit includes:
the analog-to-digital conversion subunit is used for performing analog-to-digital conversion on the analog electric signal to generate a digital signal;
the serial-parallel conversion subunit is used for performing serial-parallel conversion on the digital signals to generate parallel digital signals;
a prefix and suffix removal subunit for removing prefix and suffix output digital FTN-PAM4 signals of the parallel digital signal.
5. The data receiving apparatus of claim 4, wherein the decoding unit comprises:
a PAM4 decoding subunit for decoding the digital PAM4 signal;
and the parallel-serial conversion subunit is used for performing parallel-serial conversion on the decoded data to generate the received data in the form of a bit sequence.
6. The data receiving apparatus as claimed in claim 4, wherein the maximum likelihood sequence detecting sub-unit performs maximum likelihood sequence detection on the equalized signal using a Viterbi algorithm.
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| CN101277142A (en) * | 2007-02-27 | 2008-10-01 | 法国原子能委员会 | Maximum likelihood decoder for pulse and amplitude position modulation multi-source system |
| CN103814539A (en) * | 2011-09-08 | 2014-05-21 | 松下电器产业株式会社 | Signal generating method and signal generating apparatus |
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