# A LoRaWAN Architecture for Communications in Areas without Coverage: Design and Pilot Trials
## 4 Design of the TeamUp Network Based on LoRaWAN  
The TeamUp network has been specifically designed to provide a solution to the problem of connection of an emergency team in areas without cellular coverage. Therefore, the idea was to develop a private network with its own low-cost and mobile infrastructure that was capable of transmitting information (messages and location) from any mobile device to the central node, even if the end nodes were located in areas out of the cellular coverage. As a summary, the main objectives in the design of the TeamUp network are presented:  
* End-to-end transmission over long distances (minimum 300 m);
* Bit rate to support plain text emergency messages, location messages and location images. (minimum 1 Kbps);
* Mobility of users in a controlled, known and uncovered area.  
The TeamUp network is designed around the architecture of a standard LoRaWAN network. This LoRaWAN architecture was implemented using the Chirpstack platform at  
Figure 4: LoRaWAN architecture and security.  
the core of our design. ChirpStack [31] is an implementation for LoRaWAN networks that can be installed in a private deployment. The architecture is similar to the LoRaWAN architecture and consists of ChirpStack Network Server, ChirpStack Application Server, Redis and PostgreSQL databases and Mosquito MQTT Broker [32; 33]. A series of improvements is added to the core through external elements and software such as a mobile application, a server designed exclusively for this work and a web interface for complete management of the network.  
Figure 5 shows the two alternatives proposed for the deployment of the TeamUp network:  
* Set-up A provides freedom of movement at both ends of the net. Although the architecture is centralized, the central node can move around the work area. This configuration facilitates the modification of the coverage area dynamically. It is a design intended for activities where the execution area is unknown.
* Set-up B presents a centralized structure, but in this case, the central node is static due to the need for a light point, while the end nodes can move freely as long as they are in the coverage range of the central node. This configuration is intended for small and well-known areas.  
In the implementation, both configurations are similar with respect to the nodes. The main difference is the use of the node called \"Gateway Hardware\" and the ability to use LoRa by the central node:  
* Set-up A: all nodes are small, with low computational cost and battery-powered devices. This configuration uses the hardware gateway that acts as a LoRa bridge and sends the information to the central node.
* Set-up B: the end devices are small battery-powered devices to provide mobility, but the central node is a larger device and has a built-in LoRaWAN gateway.  
The following subsections discuss the nodes used and their functionalities. After that, Section 4.6 explains the exchange of messages through the entire network.  
The designed network offers a number of advantages. The network employs wireless links using different technologies, such as Bluetooth Low Energy, LoRaWAN, Wi-Fi or 4G. The LoRaWAN links provide the network with a wide range of coverage for sending emergency and location messages. The network maintains a star architecture using small devices. This allows the position of the nodes to be constantly modified and provides mobility to the users. The network is easy to deploy in cases of emergencies. In addition, the network consists of three types of servers that mainly allow the storage of information and the monitoring of users. However, the use of LoRaWAN technology poses challenges. The main challenges of the network are latency and the data transmission rate. Section 5  
Figure 5: TeamUp network designs. (**a**) Mobility design using a hardware gateway and central node without LoRa. (**b**) Static design using a central node with LoRa.  
discusses both aspects and concludes that the network is valid for emergency systems in areas without coverage.