Adaptive Energy Saving Technique with Saturation Avoidance for Outdoor VLC

Saturation of optical receivers, caused by sunlight, represents a major issue in outdoor VLC system design for vehicular applications. This effect reduces maximum communication range, causing performance degradation when transmitter and receiver are in strict proximity. In addition, when saturation phenomena occur, only a fraction of total transmitted power is really exploited by the receiver, resulting in a significant waste of energy. The aim of this work, is to provide a novel analytical perspective, properly validated by experimental tests, in which the effects of saturation are related to the performance of outdoor VLC systems, in terms of signal to noise ratio (SNR). This analysis is further exploited for proposing an adaptive energy saving approach, which decreases the amplitude of transmitting power when saturation phenomena are detected by the receiver. A use case evaluation shows a reduction of 30% on average energy per bit transmitted, without any significant degradation of signal to noise ratio. Conversely, the adaptive control significantly improves SNR when transmitter and receiver are in close proximity and the system is fully approaching saturation.