# From Sensor Networks to Internet of Things. Bluetooth Low Energy, a Standard for This Evolution
## 7 Improving the CSR Mesh
### Collaborative Mesh Evaluation
#### 7.3.2 CSR Retransmit Each Packet Once  
In this experiment, CSR devices were configured to retransmit each received packet once, while Waspmote devices used two different configurations described before: _Low Network Load_ and _High Network Load_.  
Table 16 shows the number of packets received by CSR devices (the core of our mesh network) and by the BLE server. As results shows, for _Low Network Load_, the number of packets received is lower than the number of packets received when CSR devices were configured in default mode. It is expected since, with the current configuration, CSR devices repeat each packet less times. In addition, for _High Network Load_, the number of packets received by CSR devices is greatly increased, although the number of packets (sent and retransmitted by sensor nodes) does not increase (see Table 17). This is due to the used configuration, which triples the number of repetitions of this packets. However, these numbers are very high compared with the collaborative mesh with CSR devices configured in default mode (see Table 13. In future work, a study will be conducted to understand this fact.  
Table 16 shows the number of packets sent by sensor nodes, the number of original packets from each sensor node received by BLE server and also the number of packets retransmitted by each sensor node. The highest number of original packets is obtained for the _High Network Load_ configuration.  
Figure 18 shows the PLR for both Waspmote configurations. As shown, the PLR for _Low Network Load_ is around 15% on average, too high for our _Zero fails_. It is the highest of all configurations for our  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Number of Packets Transmitted**} & \multicolumn{5}{c}{**Packets Received by**} \\ \cline{2-6}  & **Sen Packet** & **CSR1** & **CSR2** & **CSR3** & **Server** \\ \hline
1 (Low Network Load) & 10,384 & 14,700 & 12,589 & 4617 \\ \hline
3 (High Network Load) & 95,138 & 116,130 & 100,465 & 5218 \\ \hline \hline \end{tabular}
\end{table}
Table 16: Number of packets received by CSR devices and BLE server for each Waspmote configuration in Collaborative Mesh with CSR devices retransmit each packet once.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{3}{*}{**Sensor Nodes**} & \multicolumn{5}{c}{**Low Network Load**} & \multicolumn{5}{c}{**High Network Load**} \\ \cline{2-6}  & \multicolumn{2}{c}{**Packets Received by BLE Server**} & \multicolumn{2}{c}{**Retransmitted Packets**} & \multicolumn{2}{c}{**Sen Packet**} & \multicolumn{2}{c}{**Packets Received by BLE Server**} \\ \cline{2-6}  & **Sen Packet Packet** & **Sen Packet** & **Sen Packet** & **Sen Packet** & **Sen Packet** & **Sen Packet** \\ \hline W1 & 695 & 591 & 3006 & 652 & 652 & 2081 \\ \hline W2 & 680 & 537 & 2997 & 638 & 638 & 2058 \\ \hline W3 & 690 & 650 & 3089 & 660 & 660 & 2161 \\ \hline W4 & 666 & 592 & 2976 &mesh proposal, and similar to the PLR obtained for 2 sensor devices by CSR Mesh topology, using the saving mode configuration in CSR devices. However, the PLR for _High Network Load_ is 0.03%, the lowest of all configuration, including CSR Mesh.  
Table 18 shows the network traffic. For _Low Network Load_, the traffic network is low for 8 sensor devices. However, its PLR is too high for real network requirement. For _High Network Load_, the traffic network is very high. This high traffic network explains the low PLR.  
As can be seen, _Low Network Load_ for Waspmote devices with CSR devices in saving mode is not a good option for Industry 4.0 due to its _Zero fails_ requirement. However, _High Network Load_ achieved an incredible PLR, but a higher traffic network. As always in networks, we have to evaluate the importance and priority of these parameters. For our aim, the most important parameters are: to get a PLR as close to zero as possible and to provide a wide network coverage, both with an acceptable network traffic which is not increased in a huge way compared with the traffic on CSR Mesh network.