Power Consumption of LED-Based LiFi Transmitters

Communication via light, particularly light fidelity (LiFi), offers secure wireless connectivity that is free from radio frequency (RF) interference and enables dense spectrum reuse. This paper advances the modeling of the power consumption involved when using light-emitting diodes (LEDs) as emitters. Many earlier publications assume that the electrical power consumption of a LiFi emitter is proportional to the variance of the input signal, thus to the average of the square of the signal. This widely adopted model has proven to be problematic for several reasons. It implies a potential violation of the law of conservation of energy (LoCoE), overlooks the Shockley diode equation, and disregards the fundamental energy required to generate photons. Therefore, it often leads to inappropriate optimization designs as it assumes that electrical power consumption scales with signal variance. LiFi requires more accurate models to estimate its power consumption than those typically used in the literature. This work introduces a more realistic model. The electrical power consumed by an LED is, in reasonable approximation, proportional to the first moment of the non-negative signal or to the root-mean-square (RMS) standard deviation of the modulation signal. Our results align with the LoCoE, wall-plug efficiency, and the Shockley diode equation. These emphasize that photon generation depends on a relatively constant voltage rather than a voltage that scales linearly with the photon f lux. According to Planck's function, this voltage is linked to a wavelength-dependent constant. We explored counterintuitive consequences of this perspective in detail. Importantly, we show that when power for photon creation is modeled more accurately and applied to an intensity-modulated optical link, the optimal design strategies differ substantially from those derived from RF systems.