Experimental Demonstration of a 6.56-Gbps Energy-Efficient VLC System With LACO-OFDM and 4-bit DACs for Scalable Access in Future Optical Communication Networks

The growing demand for low-cost, high-speed indoor wireless communication has driven increasing interest in visible light communication (VLC) systems with simplified transmitter hardware. While layered asymmetrically clipped optical orthogonal frequency division multiplexing (LACO-OFDM) and digital resolution enhancers (DRE) have been separately explored to improve spectral efficiency and noise resilience, their collaborative performance in practical low-resolution scenarios remains an open question. This work experimentally demonstrates a cost-efficient, scalable low-resolution VLC system architecture capable of achieving 6.5625-Gbps over a 1-m free-space link using only 4-bit digital-to-analog converters (DACs). Compared with our previous work based on single-layer ACO-OFDM, the proposed paradigm improves theoretical SE by a factor of 1.75 and real data rate by a factor of 1.458, while maintaining reliable transmission at 32-QAM with only 4-bit DAC resolution at 0.75 GBd. Further, compared to DC-biased optical OFDM (DCO-OFDM), which theoretically offers twice of the SE of ACO-OFDM, DCO-OFDM suffers from severe BER degradation under low-resolution DAC conditions, preventing support for higher-order modulation formats. As a result, the proposed LACO-OFDM achieves significantly higher effective data rates than DCO-OFDM in practical low-resolution scenarios, enabling improved network integration potential. This work provides a practical, low-cost solution for future smart lighting and 6G optical wireless networks, where balancing hardware simplicity with high-speed reliable transmission is essential for effective indoor wireless access.