Probabilistically shaped orthogonal frequency division multiplexing
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.
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, 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;
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 real-value OFDM signal is generated by performing subcarrier modulation on the serial OFDM signal.
5. 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, 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; and
de-mapping the complex symbols using a probabilistic shaped quadrature amplitude demodulation scheme to obtain an output signal.
6. 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, 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; and
performing decision directed least mean square (DD-LMS) equalization on the serial complex symbols to obtain the complex symbols; and
de-mapping the complex symbols using a probabilistic shaped quadrature amplitude demodulation scheme to obtain an output signal.
7. The method of claim 5 , wherein the PS-QAM scheme is based on a pre-determined pulse-amplitude modulation (PAM) level distribution.
8. The method of claim 5 , wherein the PS-QAM scheme comprises a PS-1024-QAM scheme.
9. The method of claim 6 , wherein the PS-QAM scheme is based on a pre-determined pulse-amplitude modulation (PAM) level distribution.
10. The method of claim 6 , wherein the PS-QAM scheme comprises a PS-1024-QAM scheme.
11. 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, 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;
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.
12. The wireless communication device of claim 11 , wherein the PS-QAM scheme is based on a pre-determined pulse-amplitude modulation (PAM) level distribution.
13. The wireless communication device of claim 11 , wherein the PS-QAM scheme comprises a PS-1024-QAM scheme.
14. The wireless communication device of claim 11 , wherein the instructions to generate real-value OFDM signal includes instructions to perform subcarrier modulation on the serial OFDM signal.
15. 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, 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; and
de-map the complex symbols using a probabilistic shaped quadrature amplitude demodulation scheme to obtain an output signal.
16. The wireless communication device of claim 15 , wherein the PS-QAM scheme is based on a pre-determined pulse-amplitude modulation (PAM) level distribution.
17. The wireless communication device of claim 15 , wherein the PS-QAM scheme comprises a PS-1024-QAM scheme.
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, 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; and
perform decision directed least mean square (DD-LMS) equalization on the serial complex symbols to obtain the complex symbols; 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 PS-QAM scheme is based on a pre-determined pulse-amplitude modulation (PAM) level distribution.
20. The wireless communication device of claim 18 , wherein the PS-QAM scheme comprises a PS-1024-QAM scheme.