# Experiencing LoRa Network Establishment on a Smart Energy Campus Testbed
## 4 Experiments for LoRa PHY
### Combined Indoor and Outdoor Environment  
The next experiment evaluates LoRa PHY performance in the combined indoor and outdoor environment. Figure 9 depicts the campus map for this experiment. The gateway stays at the same location, and the nodes ( marks) are placed on both the inside and outside of the buildings. The red marks represent nodes inside two buildings--a library and a cafeteria. The library is next to Building #7, and we select two positions on the first floor of the library for the experiments. Nodes protected \begin{table}
\begin{tabular}{c c} \hline \hline  & **Maximum Distance for 90\% Reliability** \\ \hline SK Telecom [15] & 3.03 km \\ [PERSON] et al. [16] & 2.8 km \\ [PERSON] et al. [17] & 2 km \\ Our result & 3.83 km \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Comparison of communication ranges in the outdoor environment. Figure 8: RSSI (received signal power) values in the outdoor-only environment. The blue x marks represent the measurement data, and the red line draws the estimation of the RSSI with increasing communication distances [m] based on the measurement. with plastic enclosures are thus positioned: one is on the floor, and the other is in the drawer, as shown in Figure 9b. There are few students in the area during the experiments. The cafeteria is around 220 m away from the gateway, where several nodes are deployed. Experiments are conducted during lunchtime so that the cafeteria would be crowded with students. The black marks in the figure represent outside nodes on the campus. One node is just next to the gateway, and thus, the LOS communication between them is secured. The other node is on the roadway past the library building. In this setting, the radio signals travel through the library building located in the middle to reach the gateway. As described, the experiments include many variables, such as inside vs. outside, level of crowding, communication distance, and line of sight. However, the intention of this experiment is to find the simplified path loss model. Thus, this section illustrates the experimental results in a simple, combined manner. Figure 10 shows the received power of data signals measured and estimated with increasing distance from the gateway. The blue x marks representing the measurement data indicate that the RSSI value decreases with distance more rapidly than in the previous experiment. This is mainly attributed to the influence of buildings and obstacles around and in the middle. The path loss exponent, \(\gamma\), is computed as 3.956, from which we complete Equation (3) for the combined indoor and outdoor environment (see the red line in the figure). The maximum communication ranges can then be estimated; with SF = 12 and SF = 7, the communication distances become around 2.03 km (\(-\)137 dBm) and 0.95 km (\(-\)124 dBm), respectively. To estimate the maximum communication ranges more accurately, we investigate the details of the experimental results (the RSSI values). Figure 11 plots the numbers of data signals with increasing strength of the received power at the four measurement locations. A histogram shows how much the received power instantaneously varies for each measurement. The results in Histogram (a), collected from the library, are in the distinct shape of a Gaussian distribution. There are few students in the library, and thus, it seems likely that stationary obstacles primarily affect signal propagation. Histogram (b), from the cafeteria with few students, shows a similar pattern. In Histograms (c) and (d), however, the signal power is measured broadly over a wide range. In the cafeteria, there are many students, and some are moving around, which may meaningfully distort wireless signals. This implies that the communication distance can decrease to less than 2.03 km and 0.95 km in the real-world, combined environment. Figure 9: Experimental setup for combined environment: a gateway and a node with an enclosure.