## 4 IoT Multi-Sensor System for Remote Patient Monitoring
### LoRaWAN Gateway Placement and Field Tests  
The LoRaWAN gateway module (GW) allows for the connection of a very large number of wireless sensors. This is one of the main advantages that determined the selection of LoRa technology as being at the center of the proposed system and used as the communication protocol. The optimal placement of the GW module is very important and has an impact on the global performance of the patient monitoring system. In order to determine the optimal position of the GW, RadioPlanner [42] software was used with the propagation models presented in [43]. The developed model included the urban geographical area that we wanted to monitor, the terrain configuration, building positions, heights, and other interferences including vegetation path losses.  
From the obtained data depicted in Figure 7, the optimal placement of the GW module for the field measurement tests is on the roof top of Suceava County Hospital (GW04 from the Figure 4), at a height of 360 m above sea level. In this configuration, a single GW will cover about 5 km\({}^{2}\) in the urban environment, so with a small number of GWs the surface of an entire city may be covered. RadioPlanner can be used by LoRaWAN integrators to determine the optimal placement of the GW modules, thus will reduce the implementation costs and the performance level of the wireless sensor networks.  
Figure 6: Physical implementation of the wearable device. (**a**) IoT multi sensor configuration. (**b**) IoT wearable device installed on patient.  
The next step was to perform field measurements as to validate the simulated coverage measurements. In this test setup, a RakWireless 7249 gateway [44] was used with an omnidirectional antenna having gain of 12 dBi. Figure 8 presents the obtained results. One can see that the recorded values are very close to the values obtained from our radio propagation model.  
If the IoT multi-sensor system is to be extended to cover Suceava town entirely, we need to place multiple gateways. Thus, we evaluated the scenario to find out the number of LoRaWAN gateways needed to cover the entire area. As seen in Figure 9, the highest level of performance is obtained when using three gateways: GW01, GW02 and GW03. The distance between the gateways is approximately 5 km and can ensure a coverage area of approximately 20 km\({}^{2}\), including the neighboring villages.  
Figure 8: Field coverage measurements of the LoRaWAN gateways installed on the roof top of Suceava Hospital.  
Figure 7: Field coverage measurements—single GW configuration.  
The GW used in the field tests of the system runs ChirpStack Gateway OS [45], which has the capabilities to decode, store and forward the LoRaWAN packets to external applications under JSON application format. Figure 10 presents the monitoring and control application user interface of the application dashboard. The application is developed as an interactive map that can be easily displayed to the medical staff. The information shown includes the GPS location of each individual patient, his/her vital signals in a build-in graph window, the battery level of the device, the isolation period for each patient and specific alarms based on the threshold setup by the medical staff in the configuration settings of the integrated system.  
Figure 10: IoT multi-sensor patient monitoring application dashboard.  
Figure 9: Field coverage measurements—multiple GW configuration.  
Figure 11 presents the information acquired by the wearable IoT device for two different patients under quarantine. The measurements were acquired for the whole 14-day standard quarantine time. For the first patient, Patient A (Figure 11a,b), the measurements were within normal defined boundaries, while the second patient, Patient B (Figure 11c,d), showed an increase in body temperature and a slight drop in SpO\({}_{2}\) level, which is associated with a mild form of COVID-19 illness. Further tests and examinations performed on Patient B showed that he was positive for SARS-CoV2 virus infection.