## 7 Evaluation
The noise corresponds to the signal strength of all the contributing interference networks received at the gateway position, and the signal of interest corresponds to the signal strength received at the gateway coming only from the first node. For the considered transmission powers, if signal and noise overlap in time and frequency, the communication will fail as the strength of the signal of interest is lower than the noise at the gateway. The frequency pattern of Figure 20 will be the same for all the nodes in the network, but the amplitude of the different signals will depend on the distance between the nodes and between the nodes and the interfering networks. \begin{table}
\begin{tabular}{c c c} \hline \hline \multicolumn{3}{c}{**QUALITY METRIC PARAMETERS**} \\ \hline \multicolumn{2}{c}{QUANTILE} & \multicolumn{2}{c}{SOTH} \\ \multicolumn{2}{c}{95\%} & \multicolumn{2}{c}{\(th=-60\) dBm} \\ \hline \multicolumn{3}{c}{**HOPPING TECHNIQUE PARAMETERS**} \\ \hline CMFH & AFH & UBAFH & SAFH \\  & & \(\xi=0.85\) \\ \(\xi=0.1\) & \(\alpha=0.5\) & \(\alpha=2\) & \(\alpha=1\) \\  & & \(c=10\) \\  & & \(s=1\) \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Configuration parameters for quality metrics and hopping techniques. Figure 19: Channel selection. HGFH technique directly uses the channel gain (red) to select the 10 best channels. WRFH, AFH and SAFH techniques use the cumulative metric (blue) derived from the power metric (green) to select the best channels. In all the case, the selected channels are represented as vertical black lines. Figure 20: Frequency pattern of signal and noise for different hopping techniques and quality metrics. The interfering noise is represented in red and the signal of interest in green. The same noise pattern is considered for all the hopping techniques and all the quality metrics. Different hopping techniques and different quality metrics result in different frequency patterns for the signal of interest. The overlapping of the noise and signal of interest is represented in black. Figure 21: Strength of signal and noise for different hopping techniques and quality metrics. The interfering noise is represented in red and the signal of interest in green. The noise is the sum of all the interfering networks as received at the gateway. The signal of interest is the signal strength received at the gateway coming from the first node. For each possible bidirectional connection between nodes of the network under study, the PER is calculated from the number of interferences during the operation time. The result will be a matrix for each quality metric and hopping technique as represented in Figure 22.  
From the PER of each connection, the topology of the network can be determined in terms of overall packet error rate and transmission distances. Figures 23-25 show the resulting topologies when assigning different weights to the transmission distances and the resulting PER. Only attending to the overall PER results in direct connections between the nodes and the gateway (Figure 23), while minimizing the transmission distances results in multi hop transmissions (Figure 24). In both cases, the same topologies result for all the quality metrics and hopping techniques. When assigning equal weights to the transmission distances and the overall PER, different topologies result for different quality metrics and hopping techniques (Figure 25). With the HGFH, for instance, hopping from node to node in order to minimize the transmission distances does not penalize the overall PER at all, while with the other hopping techniques, the overall PER is considerably increased as the transmission distances are reduced. Table 5 summarizes the overall PER results for all the quality metrics in Section 4 and all the hopping techniques in Section 5 for equal weights of overall PER and transmission distances. For most of the considered metrics, the RFH results to be the worst hopping technique as we could expect.