## 4 Main Tools of the WSN-DPCM Platform
### Tool for WSN Application Planning and RF Simulation
#### 4.1.2 RF Simulation and Connectivity Matrix  
This component has two main functions within the WSN-DPCM platform: to allow the developer to check node connectivity for a given placement in the application field and to generate the input  
Figure 4: Work flow of the 3D outdoor environment reconstruction. data for the topology reduction and network simulation components of the WSN-DPCM platform. Its main features have been recently presented at a conference [36] and are here better detailed. The component calculates the received signal strength for each node when each of the other nodes in the network is transmitting (one at a time) using an electromagnetic solver, or RF tool. It receives as input a digital description of the application scene and the technical specifications of the transmitting antenna. The former is provided using a file in Keyhole Markup Language (KML) format that describes the buildings, and a raster file that describes the topography of the terrain, _i.e._, the Digital Terrain Model (DTM), if available. The format employed for building description simplifies data import from various sources, such as local authorities, Google Earth or Google Maps, or reconstructions from aerial photography using the component described in Section 4.1.1. Relative permittivity and conductivity of building walls and terrain can be added to improve simulation accuracy, otherwise the simulator uses sensible defaults based on area type (historical, residential, business district). The transmitting antenna is described by its position, radiated power, pointing direction, radiation diagram and polarization. The solver is based on a 3D space analysis similar to that described in [22; 23] using a ray tracing algorithm that considers direct, reflected and diffracted rays. In particular, reflections are computed using Geometrical Optics (GO) and diffractions are evaluated using the Uniform Theory of Diffraction (UTD). The user may also select a \"fast mode\" that only accounts for the direct and reflected rays, to avoid most computational load which is due to diffracted rays. The resulting electromagnetic field is provided on regular 2D grids (\"layers\") located on surfaces at well-defined heights above the ground (or above the roof, if the grid point is on top of a building). Accordingly, a 3D map is obtained, which shows the field levels produced by the transmitting antenna in the considered scene. The map is stored in geotiff format; it can be displayed by the WebTop user interface (GUI) and optionally superimposed on a Google Earth image (as shown in Figure 5), and/or it can be passed to the connectivity matrix module. The latter, based on the field maps produced by the electromagnetic solver, computes and stores the field values radiated by each antenna (node) at the locations of all other antennas (nodes) in a \"connectivity matrix\". This matrix can be easily converted in a binary matrix if receiver field threshold levels are defined. Non-zero elements of the matrix can be displayed by the GUI as arcs connecting the corresponding nodes, as shown in Figure 6.  
Figure 5: 2D graphical display of the computed field radiated by one of the nodes (**a**) that can be superimposed to Google Earth image of the area (**b**). A typical use of this tool within the WSN-DPCM toolset starts from a 3D description of the scene in which the developer places the motes based on the sensing requirements of the application. Then, the developer selects a propagation model (fast, for quick but less accurate simulation, or standard, for slower but more accurate simulation). The RF tool calls the solver and connectivity matrix modules to compute the field levels generated by the transmitter of each node in the whole scene and uses them to generate the connectivity matrix, as explained before. Based on these results, the developer may iteratively refine node positions, optionally using the topology reduction tool (see Section 4.1.3).