## 5 Analysis of the Results
### Mean System Loss Component  
The MSL component represents the decrease in the received signal power with distance due to absorption and dissipation of energy in the propagation medium, which is represented as follows:  
\[\overline{L_{\text{S(dB)}}}=\overline{L_{\text{S}}(d_{0})_{\text{(dB)}}}+10 \cdot n\cdot\log_{10}\left(\frac{d_{[\text{m}]}}{d_{[\text{m}]}}\right), \tag{2}\]  
where:  
* \(\overline{L_{\text{S}}(d_{0})}\) is MSL value at the reference distance \(d_{0}\) (\(d_{0}\) = 2 m for LOS and \(d_{0}\) = 8 m for NLOS),
* \(n\) is system loss exponent (SLE), and
* \(d\) is the distance between Tx and Rx.  
The MSL component was obtained by fitting the logarithmic distance function to the empirical data. Linear regression with the least squares method was used.  
To analyze the accuracy of linear model, two well know measures were used, namely standard error of estimate (SEE), representing the standard deviation of empirical data around the regression line, and mean error (ME) [32].  
The obtained values of the SLE (\(n\)) and the MSL (\(\overline{L_{S}(d_{0})}\)) at reference distance \(d_{0}\), both for 868 MHz and 6489 MHz bands, are presented in Table 1.  
There are visible differences between the MSL parameters for various scenarios, placements of MN, and for different radio interfaces (NB and UWB). For each scenario, a significant differences in both parameters for the LOS and NLOS conditions were observed. The ME error was 0 dB, which means that the MSL model parameters are correctly estimated from the measurements.  
In the 868 MHz NB channel the multipath propagation phenomenon and the waveguide effect in the corridor are clearly visible. The values of \(n\) for LOS conditions are in the range of [0.16; 0.34], beingbelow the free-space value of 2 [33]. For NLOS, excluding the \(\text{HE}_{\text{R}}\) scenario, the parameter \(n\) is in the range of [1.40; 3.80]. These differences are related to the high power level of the multipath components reaching the antenna compared to the power of the direct component [34]. The noticeably low value for the \(\text{HE}_{\text{R}}\) scenario (0.16) can be explained by the unique environmental conditions, in which there is a strong reflected component from the opposite side of the corridor wall. Moreover, the polarizations of both antennas were matched and their mutual orientation changed to a small extent. As expected, the MSL at the reference distance is greater under NLOS conditions for most cases, but these differences are not significant. The SEE does not exceed the value of 3 dB for all the scenarios.  
Similar to the NB channel, there are also differences between the MSL model parameters for the UWB channel. The results show a significant difference in between the values of \(n\) for the LOS and NLOS conditions. Similar conclusions based on empirical data are presented in the available literature [14; 35; 36]. For the LOS conditions, the \(n\) values are in the range of [0.13; 0.85]. As expected, these values are below the free-space value, which is caused by the waveguide effect. It was also noticed that, similar to the NB interface, the highest value of \(n\) (0.85) was obtained for the DEP scenario and the \(\text{TO}_{\text{F}}\) placement. However, the obtained values of \(n\) for the NLOS conditions are in the range of [1.25; 3.46]. The two highest values of \(n\) were obtained for the MN mounted on the head (\(\text{HE}_{\text{R}}\)). Almost all scenarios are characterized by a higher MSL at the reference distance for the NLOS conditions relative to the LOS ones; the difference never exceeds 5.1 dB. The obtained SEE does not exceed the value of 3.1 dB.