## 4 Network Performance
### XMesh
Such high network PRR values occur when only nodes from sites closer to the base station are connected, and the performance is reduced as nodes from farther sites connect to the network. The figure also confirms that the XMesh application at ASWP testbed presented congestion problems, especially when operating under heavier traffic generated from a higher number of connected nodes, as seen for period P2 after the deployment of the additional IRIS motes. An additional perspective for the performance of the network, and specifically for the XMesh routing protocol, is presented in Figure 7 with the nodes' PRRs, PSRs, and average path costs. First, with respect to the node PRRs, it is possible to see that most nodes in Site 1, which are closer to the base station, were \begin{table}
\begin{tabular}{c c c} \hline \hline
**Period** & **PRR** & **PSR** \\ \hline P1 & 35.17\% & 49.09\% \\ P1a & 61.04\% & 53.92\% \\ P2 & 36.01\% & 46.08\% \\ P2a & 42.16\% & 45.33\% \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Network-level performance metrics for the two XMesh evaluation periods and their respective sub-periods, including packet reception rate (PRR) and packet success rate (PSR). able to maintain higher percentages, between 50% and 64%, compared to the rest of the nodes in the testbed. The PRRs for most nodes in Site 1 are comparable to the highest network PRR obtained during sub-period P1a. It is observed that there were a few low peaks in the nodes' PSR, indicating that those forwarding nodes across the testbed presented a lower link quality. An unexpected result was that several nodes with relatively low PSR (e.g., nodes 1010, 1040, 1060, 2071, 2141, 3045 and 3113) reported lower path costs for routing. For example, node 1010, regardless of having one of the lowest PSRs, kept reporting the lowest path costs during P2 at its critical location close to the base station. Therefore, it was the most likely node to be selected as a parent after the base station. To further analyze potential causes behind high packet losses, node health statistics were processed at the node level and Figure 8 presents the results for each node in average daily values. Most nodes  
Figure 6: Network PRR _versus_ number of connected nodes in the network when using XMesh. PRRs are computed monthly and the number of connected nodes is computed as the average of daily connected nodes within the network in the same time period. Figure 7: Daily averages of individual node packet reception rate (PRR), packet success rate (PSR), and XMesh path cost during evaluation periods P1 and P2. located in Site 1 have a higher number of received packets and these values decrease for nodes located in Sites 2 and 3. Comparing the node packets received between P1 and P2, it can be seen that nodes located farther away from the base station consistently had a lower number of received packets, as reflected in the figure by nodes with higher node identifiers. Furthermore, when considering forwarded packets, there are a few nodes (_i.e._, 1010, 1100, 2071, 2141, 3005, and 3130) which were highly used by their neighbors. These nodes established a highly used path across the network topology (see Figure 3), which at the same time was accountable for most of the packet retransmissions and drops.