0.5-bit/s/Hz fine-grained adaptive OFDM modulation for bandlimited underwater VLC.

Area of Science:

• Optical Communications
• Signal Processing
• Underwater Technology

Background:

• Bandlimited underwater visible light communication (UVLC) systems face challenges in achieving high spectral efficiency.
• Conventional orthogonal frequency division multiplexing (OFDM) with Quadrature Amplitude Modulation (QAM) offers integer spectral efficiencies, limiting fine-grained adaptation.
• The need for more granular spectral efficiency is critical for optimizing UVLC performance.

Purpose of the Study:

• To propose and demonstrate a 0.5-bit/s/Hz fine-grained adaptive OFDM modulation scheme for bandlimited UVLC systems.
• To introduce novel dual-frame OFDM designs for achieving fractional spectral efficiencies.
• To verify the feasibility and superiority of the proposed scheme through simulations and experiments.

Main Methods:

• Development of OFDM with dual-frame binary phase-shift keying (DF-BPSK) for 0.5 bit/s/Hz spectral efficiency.
• Design of OFDM with dual-frame dual-mode index modulation (DF-DMIM) for 0.5+n bits/s/Hz spectral efficiencies.
• Validation using simulations and proof-of-concept experiments in UVLC environments.

Main Results:

• The proposed 0.5-bit/s/Hz fine-grained adaptive OFDM scheme was successfully demonstrated.
• Experimental results showed a significant achievable rate gain of 18.6 Mbps.
• A rate improvement of 22.1% was achieved compared to traditional 1-bit/s/Hz granularity adaptive OFDM.

Conclusions:

• The proposed 0.5-bit/s/Hz fine-grained adaptive OFDM modulation is effective for bandlimited UVLC systems.
• The novel dual-frame OFDM designs enable precise spectral efficiency control.
• This advancement offers a substantial performance enhancement for underwater optical communication.