PROBABILISTICALLY SHAPED ORTHOGONAL FREQUENCY DIVISION MULTIPLEXING

• US 20180262274A1
• Filed: 03/02/2018
• Published: 09/13/2018
• Est. Priority Date: 03/10/2017
• Status: Active Grant

• Current Assignee: ZTE Corporation
• Original Assignee: ZTE Corporation
• Inventors: Yu, Jianjun, Shi, Jianyang
• Granted Patent: US 10,236,991 B2
• Time in Patent Office: Days
• CPC Class Codes: H04B 10/541 Digital intensity or amplitude modulation
• CPC Class Codes: H04B 10/548 Phase or frequency modulation
• CPC Class Codes: H04L 27/2636 with FFT or DFT modulators, e.g. standard single-carrier frequency-division multiple access [SC-FDMA] transmitter or DFT spread orthogonal frequency division multiplexing [DFT-SOFDM]
• CPC Class Codes: H04L 27/26526 with inverse FFT [IFFT] or inverse DFT [IDFT] demodulators, e.g. standard single-carrier frequency-division multiple access [SC-FDMA] receiver or DFT spread orthogonal frequency division multiplexing [DFT-SOFDM]
• CPC Class Codes: H04L 27/2697 in combination with other modulation techniques
• CPC Class Codes: H04L 27/36 Modulator circuits; Transmitter circuits

Abstract

An optical signal transmission can use probabilistically shaped technique to improve performance and increase the transmission capacity. For instance, a 30-Gbit/s/λ, probabilistically shaped (PS) 1024-QAM DFT-S OFDM was experimentally demonstrated over 40-km SSMF in an intensity modulation-direct detection system. The Achievable Information Rate (AIR) 9.5344-bits/QAM symbol of PS-1024-QAM modulation is first achieved in the experiment and shows feasibility for OFDM.

Claims

1. A method of optical communication, implemented at a transmitter in an optical communication network, comprising:

mapping input data to complex symbols using a probabilistic shaped quadrature amplitude modulation (PS-QAM) scheme;

converting the complex symbols from serial data to parallel data to obtain parallel complex symbols;

generating an OFDM signal from the parallel complex symbols;

adding a cyclic prefix to the OFDM signal;

converting the OFDM signal with the cyclic prefix from parallel data to serial data to obtain a serial OFDM signal;

generating a real-value OFDM signal from the serial OFDM signal; and

transmitting the real-value OFDM signal.

2. The method of claim 1, wherein the PS-QAM scheme is based on a pre-determined pulse-amplitude modulation (PAM) level distribution.

3. The method of claim 1, wherein the PS-QAM scheme comprises a PS-1024-QAM scheme.

4. The method of claim 1, wherein the generating of the OFDM signal from the parallel complex symbols includes:

performing an N-point Inverse Fast Fourier Transform (IFFT) on the parallel complex symbols, wherein N is an integer.

5. The method of claim 1, wherein the OFDM signal is a Discrete Fourier Transform-Spread (DFT-S) OFDM signal, and wherein the generating of the OFDM signal from the parallel complex symbols includes:

performing an L-point Fast Fourier Transform (FFT) on the parallel complex symbols to obtain an L-point DFT-S signal; and

performing an N-point Inverse Fast Fourier Transform (IFFT) on the L-point DFT-S signal to obtain the DFT-S OFDM signal, wherein N is equals to a number of subcarriers of the DFT-S OFDM signal and wherein N and L are integers.

6. The method of claim 1, wherein the real-value OFDM signal is generated by performing subcarrier modulation on the serial OFDM signal.

7. A method of optical communication, implemented at a receiver in an optical communication network, comprising:

receiving and converting a real-value OFDM signal to a complex-value OFDM signal;

removing cyclic prefix from the complex-value OFDM signal;

converting, after removing the cyclic prefix, the complex-value OFDM signal from serial data to parallel data to obtain a parallel OFDM signal;

generating, from the parallel OFDM signal, complex symbols based on a probabilistic shaped quadrature amplitude modulation (PS-QAM) scheme; and

de-mapping the complex symbols using a probabilistic shaped quadrature amplitude demodulation scheme to obtain an output signal.

8. The method of claim 7, wherein the generating of the complex symbols comprises:

performing an N-point Fast Fourier Transform (FFT) on the parallel OFDM signal to obtain intermediate complex symbols, wherein N is equal to a number of subcarriers of the OFDM signal;

performing post-equalization on the intermediate complex symbols to obtain parallel equalized complex symbols;

converting the parallel equalized complex symbols to serial complex symbols; and

performing decision directed least mean square (DD-LMS) equalization on the serial complex symbols to obtain the complex symbols.

9. The method of claim 7, wherein the OFDM signal is a Discrete Fourier Transform-Spread (DFT-S) OFDM signal, and wherein the generating of the complex symbols comprises:

performing an N-point Fast Fourier Transform (FFT) on the parallel OFDM signal to obtain DFT-S complex symbols, wherein N is equal to a number of subcarriers of the DFT-S OFDM signal;

performing post-equalization on the DFT-S complex symbols to obtain equalized DFT-S complex symbols;

performing an L-point Inverse Fourier Transform (IFFT) on the equalized DFT-S complex symbols to obtain parallel equalized complex symbols;

converting the parallel equalized complex symbols to serial complex symbols;

performing decision directed least mean square (DD-LMS) equalization on the serial complex symbols to obtain the complex symbols.

10. The method of claim 7, wherein the PS-QAM scheme is based on a pre-determined pulse-amplitude modulation (PAM) level distribution.

11. The method of claim 7, wherein the PS-QAM scheme comprises a PS-1024-QAM scheme.

12. A wireless communication device comprising a processor and a memory, wherein the memory stores instructions that, when executed, cause the processor to:

map input data to complex symbols using a probabilistic shaped quadrature amplitude modulation (PS-QAM) scheme;

convert the complex symbols from serial data to parallel data to obtain parallel complex symbols;

generate an OFDM signal from the parallel complex symbols;

add a cyclic prefix to the OFDM signal;

convert the OFDM signal with the cyclic prefix from parallel data to serial data to obtain a serial OFDM signal;

generate a real-value OFDM signal from the serial OFDM signal; and

transmit the real-value OFDM signal.

13. The wireless communication device of claim 12, wherein the PS-QAM scheme is based on a pre-determined pulse-amplitude modulation (PAM) level distribution.

14. The wireless communication device of claim 12, wherein the PS-QAM scheme comprises a PS-1024-QAM scheme.

15. The wireless communication device of claim 12, wherein the instructions to generate the OFDM signal from the parallel complex symbols includes instructions to:

perform an N-point Inverse Fast Fourier Transform (IFFT) on the parallel complex symbols, wherein N is an integer.

16. The wireless communication device of claim 12, wherein the OFDM signal is a Discrete Fourier Transform-Spread (DFT-S) OFDM signal, and wherein the instructions to generate the OFDM signal from the parallel complex symbols includes instructions to:

perform an L-point Fast Fourier Transform (FFT) on the parallel complex symbols to obtain an L-point DFT-S signal; and

perform an N-point Inverse Fast Fourier Transform (IFFT) on the L-point DFT-S signal to obtain the DFT-S OFDM signal, wherein N is equals to a number of subcarriers of the DFT-S OFDM signal and wherein N and L are integers.

17. The wireless communication device of claim 12, wherein the instructions to generate real-value OFDM signal includes instructions to perform subcarrier modulation on the serial OFDM signal.

18. A wireless communication device comprising a processor and a memory, wherein the memory stores instructions that, when executed, cause the processor to:

receive and converting a real-value OFDM signal to a complex-value OFDM signal;

remove cyclic prefix from the complex-value OFDM signal;

convert, after removing the cyclic prefix, the complex-value OFDM signal from serial data to parallel data to obtain a parallel OFDM signal;

generate, from the parallel OFDM signal, complex symbols based on a probabilistic shaped quadrature amplitude modulation (PS-QAM) scheme; and

de-map the complex symbols using a probabilistic shaped quadrature amplitude demodulation scheme to obtain an output signal.

19. The wireless communication device of claim 18, wherein the instructions to generate the complex symbols comprises instructions to:

perform an N-point Fast Fourier Transform (FFT) on the parallel OFDM signal to obtain intermediate complex symbols, wherein N is equal to a number of subcarriers of the OFDM signal;

perform post-equalization on the intermediate complex symbols to obtain parallel equalized complex symbols;

convert the parallel equalized complex symbols to serial complex symbols; and

perform decision directed least mean square (DD-LMS) equalization on the serial complex symbols to obtain the complex symbols.

20. The wireless communication device of claim 18, wherein the OFDM signal is a Discrete Fourier Transform-Spread (DFT-S) OFDM signal, and wherein the instructions to generate the complex symbols comprises instructions to:

perform an N-point Fast Fourier Transform (FFT) on the parallel OFDM signal to obtain DFT-S complex symbols, wherein N is equal to a number of subcarriers of the DFT-S OFDM signal;

perform post-equalization on the DFT-S complex symbols to obtain equalized DFT-S complex symbols;

perform an L-point Inverse Fourier Transform (IFFT) on the equalized DFT-S complex symbols to obtain parallel equalized complex symbols;

convert the parallel equalized complex symbols to serial complex symbols;

perform decision directed least mean square (DD-LMS) equalization on the serial complex symbols to obtain the complex symbols.

21. The wireless communication device of claim 18, wherein the PS-QAM scheme is based on a pre-determined pulse-amplitude modulation (PAM) level distribution.

22. The wireless communication device of claim 18, wherein the PS-QAM scheme comprises a PS-1024-QAM scheme.