## 4 IoT Multi-Sensor System for Remote Patient Monitoring
### Wearable IoT Multi-Sensor Device for Patient Monitoring  
Figure 5 presents the block diagram of the wearable device that includes an OLED display, the GPS sensor of Neo-6M type, the MAX30102 vital signs measurement sensor and the SX1276 LoRaWAN transceiver that allows for the collected data to be transmitted  
Figure 4: COVID-19 IoT multi-sensor patient monitoring architecture. at the monitoring center. The wearable IoT device can monitor health conditions related parameters like pulse, blood oxygen saturation and body temperature as well as the patient's current location. At the center of our wearable IoT multi-sensor device we have the ATmega328p microcontroller unit that processes the information collected from different sensors linked with I2C, SPI or UART busses. For the health-related measurements, the MAX30102 [40] sensor was used as it offers an integrated solution for all three body parameters: pulse, blood oxygen saturation and body temperature, respectively. The sensor is based on the principle of spectrophotometry, which means that it detects the pulse and the blood oxygen saturation by measuring the amount of red and infrared light absorbed by the deoxygenated and oxygenated blood using photodiodes. The body temperature is measured using the temperature sensor integrated into the MAX30102. The signal provided by the MAX30102 is sent to the MCU via the I2C (Inter-Integrated Circuit) communication bus to be processed. The acquisition rate may be adjusted from the monitoring center based on the patient's health status. Different patient classes can be implemented as presented in Table 2.  
Monitoring the patient's GPS position is also mandatory since maintaining a quarantine period involves isolation. Thus, a GPS module, named NEO-6M, is integrated into the sensor's architecture, being connected to the MCU via the UART (universal asynchronous receiver-transmitter) communication interface. The location data are sampled at random time intervals as to obtain energy efficiency. By monitoring the patient's current position, the authorities can be alerted in the eventuality that the patient does not comply with the quarantine conditions. If the current GPS position changes, the authorities are notified by a standard alert message transmitted to the monitoring center. The wireless transceiver used for long-range communication and LoRa modulation is SX1276 from Semtech [41]. The SF is adjustable using the ADR mechanism provided by LoRaWAN specifications, thus, a high-level of performance and power consumption optimization is obtained. Another feature of the wearable device is an OLED display used only for local parameter checks or a debug option in the testing scenarios. The monitoring platform is implemented in a compact wearable form factor case that can be attached to the patient's wrist and is easily worn. Using a Li-Po power cell of 400 mA, the designed wearable device can operate for up to 20 days without recharging the battery, so the patient can wear the device during the 14-day quarantine period without power loss issues. This is possible by using a power management algorithm integrated into the MCU. The following rule can be used; for COVID-19 confirmed patients the time between measurements can be lower and offer more in-depth information about the evolution of the case. The physical implementation of the IoT multi-sensor wearable is presented in Figure 6.  
Figure 5: Wearable device block diagram of the multi-sensor approach. Depending on the monitored case, by using the application from the monitoring center the local authorities can set a minimum predefined period per day for the wearable device to be worn. Thus, the proposed wearable multi-sensor device can be removed by the patient for short intervals. The developed system triggers alerts when the health of the person in quarantine deteriorates. Thus, the onset of symptoms should be closely monitored so that treatment is administered as soon as possible.