Application of Visible Light Communications in Intensive Care Medical Environments

Name: Klaas Minne Van Der Zwaag
Type: MSc dissertation
Publication date: 28/08/2020

Namesort descending Role
Jair Adriano Lima Silva Advisor *
Teodiano Freire Bastos Filho Co-advisor *

Examining board:

Namesort descending Role
Jair Adriano Lima Silva Advisor *
João Crisóstomo Weyl Albuquerque Costa External Examiner *
Marcelo Eduardo Vieira Segatto Internal Examiner *
Moisés Renato Nunes Ribeiro Internal Examiner *
Teodiano Freire Bastos Filho Co advisor *

Summary: The increasing demand for wireless mobile links with high data rates, high-reliable and low latency requires modern wireless technologies such as 5G and beyond. However, the gradually exhausting radio frequency resources has encouraged scientific investigations on alternative wireless technologies to avoid a future spectrum crunch. Visible light communication (VLC) arose as a promising optical wireless communication technology, exploiting the unlicensed spectrum. Despite the broad free spectrum, VLC offers advantages such as green technology, lack of electromagnetic interference, high security and low power consumption. Existing infrastructure can be utilized employing light emitting diode (LED) for lighting and data transmission simultaneously. In intensive care (IC) medical environments, this technology is an interesting solution to, among others, prevent the spread of emerging diseases. This work present a design, numerical simulations, practical characterizations, as well as experimental performance evaluations of a low-cost, stable and robust VLC system for application in IC medical environments. Preliminary studies with VLC systems based on orthogonal frequency division multiplexing (OFDM) and constant envelope OFDM signals were addressed considering flicker and light power maximization, respectively. Nevertheless, to accomplish the system complexity requirement, this work focuses on the transmission of on-off keying modulated signals. A proof-of-concept experimental setup is presented and, the results based on the eye opening penalty metric show a comprehensive picture of the proposed VLC system potential. Parameters such as the LED bias current, the modulation frequency, the line-of-sight link distance, the signal pattern and the illuminance sensitivity were extensively evaluated. The results show a susceptibility with correct reception of Manchester coding signals at dimmed illumination levels below 20 and 5 lux, defining the observation/night light standards of IC and ward environments. Error-free performance is demonstrated considering an LED bias current of 400 mA, a signal frequency of 1 MHz and a VLC transmission link length of 2.5 m. Last but not least, captured vital parameters such as heart rate, oxygen saturation, pulse rate, respiration rate, temperature and non-intrusive blood pressure were sent considering an LED polarization current of 400 mA, at VLC links of 1.5, 5 and 15 m. The results obtained with the multi-parametric monitor provide eye-opening-penalty (EOP) values of 0.89, 0.96 and 2.67 dB at the equivalent link distances, proving the feasibility of the proposed VLC system as a promising technology in classified intensive care medical environments.
Keywords: Visible Light Communication, Intensive Care Medical Environments, On-Off Keying, Manchester Codification, Light-Emitting Diode Nonlinearity

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