# Use of Wireless Sensor Networks for Area-Based Speed Control and Traffic Monitoring
## 6 Radio Coverage of the LoRaWAN Area Speed Control System and Traffic Monitoring  
Meeting the requirements set out in Section 5, especially concerning the optimization of LoRa parameters, necessitates the proper arrangement of network equipment. \"Proper\" in this context means ensuring that the equipment maintains the required level of QoS services at a preset value and emission parameters. The placement of end nodes (speedometers) in the proposed solution is determined by the road system subject to monitoring. Therefore, it is crucial to deploy gateways in locations that meet specific requirements, such as the following:  
* placement in elevated positions;
* the absence of terrain obstacles;
* the availability of broadband, hard-wired Internet access, with emergency access via the GSM network;
* permanent and emergency power supply sources. Selecting gateway locations is not straightforward and cannot be based on intuition. It should be guided by specific procedures, and even algorithms, developed for this purpose, particularly when desired redundancy is considered [69; 70]. As the topographic map in Figure 4 demonstrates, the selected area is a relatively flat terrain without significant hills or depressions, which favors good radio wave propagation. At the same time, it is a densely populated and built-up area due to its proximity to the capital city of Warsaw. However, the majority of buildings are single-family homes, typically two or three stories tall at most. For these reasons, and to meet the requirements outlined above, it is preferable to place gateways on or within buildings owned by the commune, such as the Communal Office, kindergartens, schools, health centers, sports centers, and so on. This approach also resolves several issues related to leasing space, connecting equipment, and ensuring access for maintenance and service. Figure 4: Topographic map of the Stare Babice commune. (Source: authors’ own image based on [71]). Of course, the flat terrain and relatively small buildings largely facilitate meeting the previously established conditions and criteria. However, this does not mean that there is a complete absence of terrain obstacles and other risks to network functionality. This necessitates the analysis of several gateway arrangement scenarios, supported by specialist radio coverage planning software. To this end, the authors developed a model of an area-based vehicle speed control system using LoRaWAN technology and subjected it to several radio coverage simulation scenarios. To calculate propagation, the authors selected the Deygout 94 diffraction model, which is further enhanced by the \"Area\" sub-path attenuation model. This model also assumes diffraction-type losses, even below the line of sight (LOS) [72]. To define the losses caused by lower obstacles, the area \"obscured\" by these obstacles, located in the first Fresnel zone, is identified. Sub-path attenuation is then calculated according to Equation (4). \[L_{sp}=6.4+20\text{log}\ \left[v+\sqrt{(1+v^{2})}\right] \tag{4}\]  
where  
\(v=\sqrt{\frac{H}{R}}\);  
\(\frac{H}{R}\) is the ratio between the obscured area and the area equal to half of the Fresnel zone (in Figure 5, H = H1 + H2). Cartographic data, including a digital land map and land coverage classes, as well as specific vector data on the boundary of the area and the road system within it, were used to develop an environmental model that reflects the actual terrain conditions. The simulation was based on a terrain map with a maximum resolution of 1 m, allowing for an analysis of radio coverage relative to the immediate surroundings of the roads. First, the impact of the hGW transmitting station installation height was tested.