# Radio Wave Propagation and WSN Deployment in Complex Utility Tunnel Environments +
## 4 WSN Deployment
### Scatterers Analysis: Human Presence within the Tunnel  
An important factor that has to be assessed in terms of radio propagation in small cross-section utility tunnels is the presence of human beings. It is a well-known fact that human bodies create a shadowing effect [42], and in such a narrow environment like the underground tunnels presented in this work, this effect was expected to be especially significant. In order to have insight into this phenomenon, different simulations were performed using the calibrated 3D-RL simulation tool. Human body models are included in the 3D-RL software, emulating occupational personnel at the location of interest. This human body model was implemented for the simulation, considering the dimensions of a standard person and all the dispersive material properties of its different body parts (i.e., skin, bones, muscles, blood, different organs, etc.). A further description of the considered human body model, as well as a signal attenuation analysis for different parts of the human body, can be found in reference [43]. By including computational human body models within the considered scenario, the results of the human presence effect were obtained, allowing analysis and comparison. In the context of the utility tunnel, teams of up to three workers are generally sent into the tunnels for performing different security and maintenance tasks, in order to minimize the risks and prevent accidents due to municipal authorities' requirements regarding occupational risk prevention legislation. Figure 10: Bidimensional plane of the RF power level distribution at a height of 3 m for (a) ZigBee 868 MHz and (b) LoRaWAN. Therefore, a complete analysis of the human presence within the tunnel was carried out considering different densities of human body models in different locations. First of all, the received power results of a specific scenario with no humans is presented in Figure 11, considering a transmitter located on the tunnel ceiling at \(x\)-axis = 20 m for reference and comparison purposes. Then, a single human body model was included in the scenario at different \(x\)-axis locations in order to analyze the influence of the surrounding environment and the transmitter distance along the tunnel. The considered locations were the following: 20 m, 27 m, 34 m, 41 m and 48 m. In Figure 12, the corresponding RF power levels distribution results at 1.5-m height are presented. As expected, the major RF distribution changes are mainly in the area behind the location of the human body, due to the shielding effect. Figure 11: Bidimensional plane of the RF power level distribution at a 1.5-m height for the case without human presence. Figure 12: Bidimensional planes of the RF power level distribution at a 1.5-m height for different human being locations along the tunnel. In order to gain more insights into these results, Figure 13 shows the differences between the case without human presence (i.e., Figure 11) and the different case studies considering a single human body model at distinct locations (i.e., Figure 12). As can be clearly observed from Figure 13, the presence of a single worker within the tunnel in different locations leads to RF power level differences up to 18 dB. Although this difference is lower the higher the distance from the transmitter is, it has to be taken into account for an accurate range estimation. Thus, a margin of about 20 extra dBs should be added to the wireless communication range estimated in the previous subsection both for ZigBee and LoRaWAN technologies. Finally, extra simulations were carried out in order to assess if the obtained 20 dBs are enough when work teams of three people are within the utility tunnel. In Figure 14, a rendered view of the inclusion of the three human body models within the created tunnel scenario for the 3D-RL simulation is presented.