Light fidelity for interference-free communication of critical medical devices

Critical-care devices exchange waveform and alarm data continuously, yet the radio spectrum around a bed is both congested and, from the standpoint of device immunity, hostile: the same transmitters that carry the traffic are the disturbance the equipment must survive. This paper states the coupling mechanism quantitatively against IEC 60601-1-2, then develops and evaluates a light fidelity (LiFi) replacement for the last hop. A closed-form chain covering the Lambertian channel, shot- and thermal-noise-limited signal-to-noise ratio, error probability for on-off keying and M-ary quadrature amplitude modulation on a direct-current-biased optical multicarrier waveform, delay spread, deterministic access latency and diversity outage is applied to a 7 m square intensive-care bay served by four ceiling luminaires. The link yields 53.4 to 313.4 µW of received power, 40.2 to 55.4 dB of signal-to-noise ratio, a worst-case margin of 24.6 dB over the 15.6 dB needed for a bit error ratio of 10⁻⁹, complete coverage at that error ratio and a uniform 100 Mbit/s payload rate while sustaining 233 lux. Delay spread stays below 4.4 ns so no equaliser is required at 20 MHz. Worst-case delivery latency is bounded at 0.595 ms against 13.08 ms for a contended radio baseline, and four-fold access-point diversity gives 6.3 × 10⁻⁶ outage. A 200 mW radio client is shown to exceed the 3 V/m general immunity level within 0.82 m and to induce about 318 mV on an unshielded lead at 0.3 m, roughly 50 dB above the biopotential of interest, whereas the optical front end contains no intentional radiator.