# A New Internet of Things Hybrid VLC/RF System for m-Health in an Underground Mining Industry
## 3 State of Art  
Some of the papers that deal with this topic are discussed in the following. In [19], an implementation of mobile VLC technology is presented for the transmission of clinical data in the m-Health system at home is presented; multiple clinical data such as an Photoplethysmogram (PPG), Electrocardiogram (ECG), and breathing signals are transmitted through Light Emitting Diodes (LEDs) and received by the camera of a smartphone. In [20], optical modulation based on the hospital lighting network is used; high-brightness LED (HB-LED) is used in this system as a source of lighting so that gen \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Property** & **VLC** & **IR** & **Bluetooth** & **Wi-Fi** & **Zigbee** \\ \hline Bandwidth & Unlimited, 400-700 nm & Unlimited, 800–1600 nm & Regulated and limited & Regulated and limited & Regulated and limited \\ \hline Line of sight & Yes & Yes & No & No & No \\ \hline Standards & IEEE 802.15.7 [13] & IrDa & IEEE 802.15.1 [6] & IEEE 802.11 [8] & IEEE 802.15.4 [10] \\ \hline Power consumption & Relatively Low & Relatively low & Relatively low & Medium & Relatively low \\ \hline Coverage & Limited & Limited & Good & Good & Good \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Comparison of wireless communication technologies. eral hospital information is modulated in the visible light emitted. In [21], a new VLC technology is proposed to transmit and monitor biomedical data; white-beam LEDs are used as optical information emitters to efficiently transmit biomedical data; On-Off Keying (OOK) modulation is used to modulate data in the visible light beam, and a high-speed photodetector (PD) is used in the receiver. In [22] there is a static design for monitoring patients indoors using VLC as an appropriate uplink for hospital settings; the proposed system is designed to transmit uplink patient data using VLC through OOK modulation. In [23] a non-invasive Electroencephalogram (EEG) monitoring system based on visible light communication is deployed using a generic microcontroller. In [24] a method that uses VLC technology as a transmission platform and provides real-time monitoring of heart rate, and patient information is analyzed; the white LED beam is used as a light source to simultaneously transmit the biomedical signal and the patient's medical record; the OOK modulation technique is used to modulate all data in the visible light beam. At the other end, a receiving circuit consisting of a high-speed photodetector and a demodulation circuit is used to demodulate the visible light beam data; demodulated data are transmitted in series to a personal computer where the biomedical signal, patient information, and heart rate can be monitored in real time. In [25; 26] a new strategy for the transmission of the biomedical signal of the EEG is described using a VLC link; data transmission is performed under the Line of Sight (LOS) condition using OOK modulation and the three LED color components: Red, Green, and Blue (RGB). In [27], the focus is on the optical transmission of EEG signals that use an LED and a PD to display the information in the LabVIEW 2022 software environment. In [22], a new Optical Body Area Network (OBAN) is presented to efficiently transmit multiple human vital signs of patients. The main human vital signs are body temperature, pulse rate, respiratory rate, and blood pressure. These vital signs are captured from four different patients and transmitted by VLC. Multi-patient OBAN uses orthogonal codes to transmit the data of each patient through VLC, and the OOK modulation technique is used to transmit the coded human vital signs of multiple patients. In [28], a Time-Hopping (TH) VLC system is proposed; the TH scheme is adopted to transmit multiple medical data while maintaining a simple system design. In [29], Sparse Code Multiple Access (SCMA) is used to transfer multiple medical data with greater bandwidth efficiency in real-time.