# From Sensor Networks to Internet of Things. Bluetooth Low Energy, a Standard for This Evolution
## 7 Improving the CSR Mesh
### Individual Mesh Evaluation
#### 7.2.1 CSR Devices Retransmit Each Packet Three Times: Default Mode  
In this evaluation, CSR devices were configured in default mode, while Waspmote devices were using the two different configurations described before: _Low Network Load_ (each packet is transmitted only once by Waspmote devices) and _High Network Load_ (each packet is transmitted three times by Waspmote devices). Tables 7 and 8 show the received and sent packets, respectively, by different devices in this study. Specifically, Table 7 shows the number of received packets by CSR devices and by BLE server. As said before, CSR devices process the received packet, and retransmit it only the first time it is received (the repeated packets are discarded). However, the CSR API is not completely open, and to know the number of retransmitted packets is not possible. Results show an increase of the number of received packets in the _High Network Load_ configuration, due to the high number of original packets from each sensor node (see Table 8) and the number of repetitions for each original packet (three instead of one). In this case, the node with the highest number of received packets is CSR2, due to its placement (see Figure 14). Moreover, Figure 15 shows the PLR for _High Network Load_ configuration: if Waspmote devices transmit each packet 3 times, the network PLR is, on average, only the 0.21%. Another important parameter to be considered is the network traffic, specially in mesh topologies. Table 9 shows the packets received per second in CSR devices. As it can be seen, even though using the _High Network Load_ configuration, the number of packet received by CSR devices was 8.338 on average. In CSR Mesh, we obtained 1.61 packets per second in CSR default mode, but number of sensor devices was only 2. In addition, using the _Low Network Load_, a lower number of packets per second is received by CSR devices (6.564 on average), reducing the traffic network. Figure 15: PLR in our mesh proposal for 8 sensor devices with _Individual Mesh_ configuration and 3 CSR devices with default configuration. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Sensor Nodes**} & \multicolumn{2}{c}{**Low Network Load**} & \multicolumn{2}{c}{**High Network Load**} \\ \cline{2-5}  & **Sent Packets** & **Packets Received by BLE Server** & **Sent Pakects** & **Packets Received by BLE Server** \\ \hline W1 & 644 & 633 & 781 & 780 \\ \hline W2 & 582 & 571 & 811 & 810 \\ \hline W3 & 594 & 576 & 745 & 744 \\ \hline W4 & 588 & 579 & 748 & 746 \\ \hline W5 & 607 & 598 & 763 & 760 \\ \hline W6 & 635 & 623 & 768 & 764 \\ \hline W7 & 627 & 613 & 747 & 747 \\ \hline W8 & 576 & 568 & 782 & 781 \\ \hline \hline \end{tabular}
\end{table} 
Table 8: Number of packets sent by each sensor node and received by BLE server, for each Waspmote device configuration in Individual Mesh with CSR devices retransmit each packet three times. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Number of Packets Transmitted**} & \multicolumn{3}{c}{**Packets Received per Second**} \\ \cline{2-5}  & **CSR1** & **CSR2** & **CSR3** & **Average** \\ \hline
1 (Low Network Load) & 4.833 & 8.157 & 6.703 & 6.564 \\ \hline
3 (High Network Load) & 6.031 & 10.906 & 8.076 & 8.338 \\ \hline \hline \end{tabular}
\end{table} 
Table 9: Packets per second received by CSR devices when they retransmit each packet 3 times (default mode). Waspmote devices configured as _Individual Mesh_. In this study, we can see the advantages of our mesh proposal with regard to CSR Mesh topology: our mesh proposal increases the network scalability, and reduces considerably the costs, because the use of CSR bridge devices is not necessary. Moreover, the network PLR has been reduced, and the network traffic is maintained. Finally, it is possible to reduce further the traffic network, reducing the number of packet retransmitted by CSR devices.