AI 中文总结
本文开展可实现约束下的扩散光束激光二极管LiFi设计空间分析，提出含完整噪声预算的耦合模型，评估不同FEC层级的M-PAM性能，量化理想假设对LiFi预测的夸大，发布开放仿真框架。
AI 中文摘要
室内光无线系统的链路预算研究常假设接收机参数集（大光电探测器面积、大互阻抗与宽带宽同时存在）违反基本电路约束，且噪声预算忽略占主导的放大器和激光噪声。本文基于硬件原型开展了扩散光束激光二极管（LD）LiFi链路的可实现性约束设计空间分析，该分析将全息漫射源的广义朗伯信道与接收机模型耦合，接收机模型强制满足互阻抗放大器增益-带宽/电容约束，并包含完整噪声预算：散粒噪声、反馈电阻热噪声、输入电流噪声、电容驱动电压噪声增益及激光相对强度噪声（RIN）。针对该预算，评估了两种FEC层级下的单极性M-PAM：7%开销的硬判决（阈值为3.8×10⁻³）、20%开销的软判决（阈值为2×10⁻²），还评估了第一反射漫射多径及定量扩展源人眼安全评估。全模型预测：原型在14m实测距离下，开关键控（OOK）硬判决层级有6.7dB余量时净速率为140Mb/s；4-PAM软判决的零余量可达边界为14.0m，速率为240Mb/s；5m处速率为480-558Mb/s，较相同链路在理想教科书预算下的结果低3.9-6.6倍，量化了理想化假设对LiFi预测的夸大程度。第一反射分析显示，朝下源/朝上接收机的几何结构将多径限制在最坏情况下视距-漫射比为4.2dB，延迟扩展低于0.13ns，500mW源仍比1类人眼安全限值低至少7.8倍。所有模型以ns-3模块和Python引擎形式发布，并附带自动化测试。
英文摘要
Link-budget studies of indoor optical wireless systems frequently assume receiver parameter sets--large photodetector area, large transimpedance, and wide bandwidth simultaneously--that violate basic circuit constraints, and noise budgets that omit dominant amplifier and laser noise. This paper develops a realizability-constrained design-space analysis of a diffused-beam laser-diode (LD) LiFi link anchored to a hardware prototype. The analysis couples the generalized Lambertian channel of a holographic-diffuser source to a receiver model that enforces the transimpedance-amplifier gain-bandwidth/capacitance constraint and carries a complete noise budget: shot, feedback-resistor thermal, input current noise, capacitance-driven voltage-noise gain, and laser relative intensity noise (RIN). Against this budget we evaluate unipolar M-PAM under two FEC tiers (7%-overhead hard-decision at $3.8 \times 10^{-3}$, 20%-overhead soft-decision at $2 \times 10^{-2}$), first-bounce diffuse multipath, and a quantitative extended-source eye-safety assessment. The full model predicts 140 Mb/s net at the prototype's demonstrated 14-m range with 6.7 dB margin (OOK, HD tier), 240 Mb/s at the zero-margin 4-PAM/SD reach boundary of 14.0 m, and 480-558 Mb/s at 5 m--a factor 3.9-6.6 below what the same link yields under a naive textbook budget, quantifying how strongly idealized assumptions inflate LiFi projections. First-bounce analysis shows the downfacing-source/up-facing-receiver geometry confines multipath to a worst-case LOS-to-diffuse ratio of 4.2 dB and delay spreads below 0.13 ns, and the 500-mW source remains a factor $\ge 7.8$ under the Class-1 eye-safety limit. All models are released as an ns-3 module and Python engine backed by automated testing.
Comments15 pages, 16 figures, Journal
