Problem
Research questions and friction points this paper is trying to address.
Laser-Diode LiFi
system-level modeling
diffused-beam optics
performance gap
optical wireless access
Laser-Diode LiFi With Diffused-Beam Optics: System-Level Modeling and a Cross-Validated ns-3 Simulation Framework
🤖 AI Summary
This study addresses critical gaps in laser diode–based LiFi prototype research, including throughput mismeasurement, absent noise modeling, and unclear coverage–performance trade-offs, by presenting the first reproducible, closed-loop validation framework spanning hardware to full protocol stack simulation. The system integrates a 500-mW laser source, a holographic diffuser, an IM/DD receiver, and adaptive M-QAM modulation, coupled with the ns-3 network simulator and a Monte Carlo link-level error model to enable joint PHY/MAC/network-layer evaluation. Experimental results demonstrate 930 Mb/s at 14 m (16-QAM), 1.86 Gb/s at 5 m (256-QAM), and a maximum OOK range of 23.3 m; a 20° diffuser covers a 4.2-m radius area. ns-3 simulations confirm a saturated throughput reaching 93% of the physical-layer rate and a 99th-percentile latency below 0.11 ms under 70% load, quantifying for the first time the trade-off between beam width and coverage.
📝 Abstract
Laser diodes (LDs) promise an order-of-magnitude bandwidth advantage over light-emitting diodes for indoor optical wireless access, but reported prototype studies frequently leave the gap between hardware demonstrations and system-level performance unquantified. This paper develops a complete, reproducible system model of a diffused-beam LD LiFi transceiver - a 500-mW laser source beam-shaped by a holographic diffuser, an intensity-modulation/ direct-detection (IM/DD) receiver, and adaptive M-QAM signaling - and embeds it in two cross validated simulators: an open ns-3 module providing full-stack network simulation (channel, PHY, ARQ MAC, Net Device, IP/UDP/TCP) and a Python link-level engine used for Monte Carlo validation of all analytical error models. Starting from a hardware prototype that transferred data, real-time voice, and images over a 14-m line-of-sight link, we identify and close the technical gaps typical of prototype-class reports: serial-interface throughput ceilings misread as optical-link capacity, absent noise modeling, unmeasurable error floors, and unexamined beamwidth/coverage trade-offs. The framework shows that the same optical front end, freed of its 2-Mbaud UART bottleneck and driven at its 250-MHz electrical bandwidth, supports 930 Mb/s net at 14 m under a $3.8 \times 10^{-3}$ HD-FEC threshold with 16-QAM, scales to 1.86 Gb/s at 5 m with 256-QAM, and sustains on-off keying to 23.3 m; a $20^\circ$ diffuser covers a 4.2-m-radius cell of a standard room at desk height. Network simulations over the ns-3 stack yield saturation goodput within 7% of the PHY line rate and sub-0.11-ms 99th-percentile latency at 70% load. All models, code, and figures are released for reproduction.
Innovation
Methods, ideas, or system contributions that make the work stand out.
Laser-Diode LiFi
Diffused-Beam Optics
System-Level Modeling
Cross-Validated Simulation
Adaptive M-QAM
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