Real-time OFDM or Nyquist pulse generation--which performs better with limited resources?

Area of Science:

• Optical communications
• Digital signal processing
• Integrated circuit design

Background:

• Orthogonal Frequency Division Multiplexing (OFDM) and Nyquist pulse shaping are key for high spectral efficiency in optical communications.
• Field-Programmable Gate Arrays (FPGAs) have limited digital signal processing (DSP) capacities, posing challenges for complex signal generation techniques.
• Ultra-dense wavelength division multiplexing (UD-WDM) requires efficient multiplexing techniques to maximize data transmission over limited optical bandwidth.

Purpose of the Study:

• To compare the performance and DSP resource requirements of digitally generated OFDM and sinc-shaped Nyquist pulses.
• To determine which multiplexing technology is more suitable for FPGAs with limited processing capabilities.
• To evaluate a novel Nyquist pulse shaping technique for its efficiency in UD-WDM systems.

Main Methods:

• Comparative analysis of digital signal processing (DSP) implementations for OFDM and Nyquist pulse shaping.
• Resource assessment of selected DSP techniques through simulations and experimental validation.
• Real-time software-defined transmitters utilizing single or multiple optical carriers for testing.

Main Results:

• The novel Nyquist pulse shaping technique, utilizing look-up tables, demonstrated lower resource requirements than IFFT-based OFDM signal generation.
• Similar performance was achieved by the Nyquist pulse shaping technique compared to OFDM, even with narrow inter-channel guard bands.
• The findings were validated through both simulations and experimental tests on real-time software-defined transmitters.

Conclusions:

• The novel look-up table-based Nyquist pulse shaping technique is a more resource-efficient solution for FPGAs in UD-WDM systems compared to OFDM.
• This technique offers a viable path for achieving high spectral efficiency in optical communication systems with constrained processing power.
• The study provides valuable insights for the design of next-generation optical transceivers prioritizing performance and resource efficiency.