# From Sensor Networks to Internet of Things. Bluetooth Low Energy, a Standard for This Evolution
## 8 Conclusions  
This paper has introduced the need of using a new BLE topology which fulfills the requirements in the new Industry 4.0. Firstly, existing mesh topologies have been documented. Secondly, we have chosen CSR Mesh since it allows us to take advantage of the use of BLE 4.1 radio chips, which are not very common in devices intended for IoT and Industry 4.0 use. In addition, we have proposed a new mesh topology, with different configuration modes, which has been evaluated for different use cases in an emulated Industry 4.0 environment. Our topology allows us to obtain the following benefits with respect to CSR Mesh protocol: \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Number of Packets Transmitted and** **Retransmitted by Waspmote Devices**} & \multicolumn{4}{c}{**Packets Received per Second**} \\ \cline{2-5}  & **CSR1** & **CSR2** & **CSR3** & **Average** \\ \hline
1 (Low Network Load) & 2.833 & 4.010 & 3.434 & 3.425 \\ \hline
3 (High Network Load) & 25.316 & 30.902 & 26.734 & 27.651 \\ \hline \hline \end{tabular}
\end{table} 
Table 18: Packets per second received by CSR devices when they retransmit each packet once. Waspmote devices configured as Collaborative Mesh. Figure 18: PLR in Collaborative Mesh for 8 sensor devices and 3 CSR devices with saving mode configuration. * To reduce the PLR (improving the network performance). Our proposal has obtained a lower PLR for sensor devices. Even in networks with a higher number of sensor devices, several configurations of our proposal maintain this rate close to zero fails required in Industry 4.0. * To increase the coverage area of the network. All devices can retransmit packets received from the mesh ensuring the total coverage (another Industry 4.0 requirement). * To increase the scalability of the network. It is achieved by allowing any device with a BLE chip to be part of the mesh without master-slave connection. * To improve the user experience. The most common user devices that will use this mesh network are mobile devices (for example, smartphones or smartbands), which can communicate with all the devices of the mesh without reconnecting each time when the user leaves the coverage area of his bridge device. * To provide an open packet format for BLE mesh topology. Moreover, results obtained for different network configurations show that each configuration works better in a particular use case:  
* _Collaborative Mesh_ for use cases in which to cover totally an area using the minimum number of devices is needed. * _Individual Mesh_ for use cases where the number of network devices is superior to the number of devices needed to cover totally the area. Both configurations can be combined to create an hybrid network, in which some devices use a configuration while the rest of them use the other one. Regarding the number of packets per second, we can select in a flexible way the best configuration for our network topology, according to the particular use case: _Individual Mesh_ configurations for small spaces with a lot of sensor devices and _Collaborative Mesh_ for large areas due to it increases the network coverage with a low cost. Another possible option is to combine both configuration in the same network. However, this is not possible in the evaluated CSR topology, since it has a fixed configuration, and it also requires a bridge device for each new device in the network. Although the configurations proposed in this paper (_Collaborative Mesh_ and _Individual Mesh_) use broadcast transmissions like CSR Mesh, there are several differences between them. The main differences between CSR Mesh protocol, and the _Individual Mesh_ and the _Collaborative Mesh_ proposed are showed in Table 19.  
Despite the advantages of BLE, due to network requirements and a lack of standard for mesh topology (not yet available in last BLE version [30]), different alternatives are needed. Our proposal provides an open protocol, built over BLE and completely compatible with it (in contrast to CSR Mesh [27]).