Improving performance of differential pulse coding modulation based digital mobile fronthaul employing noise shaping

Area of Science:

• Optical Communications
• Signal Processing
• Wireless Networks

Background:

• Digital mobile fronthaul systems require efficient data transmission with high fidelity.
• Existing differential pulse coding modulation (DPCM) methods face limitations in error vector magnitude (EVM) performance.
• Orthogonal frequency-division multiplexing (OFDM) signals often have unused subcarriers, presenting an opportunity for optimization.

Purpose of the Study:

• To propose and evaluate a novel noise shaping differential pulse coding modulation (NS-DPCM) technique for digital mobile fronthaul.
• To enhance the error vector magnitude (EVM) performance of mobile fronthaul systems.
• To leverage unused OFDM subcarriers for improved signal-to-quantization noise ratio (SQNR).

Main Methods:

• Implemented a feedback loop with a finite-impulse-response (FIR) filter within the DPCM encoder's quantizer.
• Developed a quantization noise shaping technique to reshape the noise spectrum.
• Demonstrated the NS-DPCM in a 25-Gb/s PAM-4 intensity modulation-direct detection optical link.

Main Results:

• Achieved significant EVM performance improvement compared to existing DPCM-based mobile fronthaul.
• Successfully reshaped quantization noise, placing lower noise power in data-modulated subcarriers and higher power in unused subcarriers.
• Demonstrated effective noise shaping without requiring transmitter oversampling or receiver low-pass filtering.

Conclusions:

• The proposed NS-DPCM technique offers a superior solution for digital mobile fronthaul, significantly improving EVM.
• This method efficiently utilizes OFDM signal characteristics to enhance SQNR.
• NS-DPCM provides a practical and effective approach for high-performance optical fronthaul transmission.