# Emergency Communication System Based on Wireless LPWAN and SD-WAN Technologies: A Hybrid Approach
## 3 An Overview of LoRaWAN and SD-WAN Technologies
### LoRaWAN Technology
Cycleo created the LoRa modulation technology, which Semtech eventually purchased. According to Semtech, the main characteristics of this technology are the suppressed cost of end devices, operating expenses, and infrastructure investments. Furthermore, standardization, low power consumption that allows a usable battery life of up to 20 years, and long-range penetration even in dense urban or even indoor applications and rural areas are eminently outstanding characteristics while providing low power GNSS-free geolocation, security (end-to-end AES Advanced Encryption Standard,) and high capacity (support of many devices per LoRaWAN gateway according to the RF emission restrictions applied from legislation). LoRaWAN employs a star topology [25, 27] in which devices are linked directly to gateways which are then linked to a network server via a backhaul (e.g., Ethernet). LoRaWAN, unlike other IoT technologies, does not employ a mesh network architecture, although mesh networking may be useful for increasing communication range due to an impact on device battery life owing to message forwarding. LoRaWAN enables bidirectional communications between end devices, though they are asymmetric because uplink transmissions (from end devices to gateways) are strongly favored. LoRa technology transmits in ISM free-use frequency bands shared with other wireless technologies. Therefore, it must comply with defined usage rules, particularly concerning the duty cycle, transmission power, and bandwidth. The most common use cases of LPWAN networks are isolated data measurements, industry applications, and Smart Cities [8, 28]. Security Options  
Regarding terms of security in LoRa Wide Area Networks, LoRaWAN employs a cryptographic mechanism based on AES-128 [29] that operates in counter mode (CTR) while based on a pre-shared key from which two additional keys for session security are \begin{table}
\begin{tabular}{l l l l} \hline \hline
**Feature** & **SIGFOX** & **LoRa** & **NBIoT** \\ \hline Coverage Area & \textless{}12 km (160 dB) & \textless{}10 km (157 dB) & \textless{}15 km (164 dB) \\ \hline Frequency & Unlicensed & Unlicensed & Licensed \\  & 900 MHz & 433, 868, 915 MHz & 7–900 MHz \\ \hline Bandwidth & 100 kHz & \textless{}500 kHz & 200 kHz shared \\ \hline Data Rate & \textless{}100 kbps & \textless{}10 kbps & \textless{}50 kbps \\ \hline Network Reforming & Large & Large & Small to moderate \\ \hline \hline \end{tabular}
\end{table} 
Table 2: LPWAN Comparison Performance. derived. End devices must be activated before the initialization of the derivation process to connect to a specific LoRaWAN network otherwise; the network server silently discards the transmitted frames. To be considered activated, an end device must have a valid copy of the following data:  
* application session key--AppSKey,
* end-device address--DevAddr, and
* network session key--NwkSKey. The LoRaWAN specification 1.0 provides two methods for establishing keys [30] leading to two types of joining schemes used, depending on data being either stored manually in the device or acquired via the radio link, i.e.,:  
* Personalization Activation (PA)
* Activation Over-the-Air strategy  
In the case of Personalization Activation (PA), the device includes hard-coded authentication data before initializing communication with the network so requiring no join procedure, while binding the end device to a specific LoRaWAN network because they include the device's LoRaWAN network identifier (NwkId), network address (NwkAddr), and cryptographic session keys. As a result, the end device is permitted to communicate with specific LoRaWAN networks while keeping these values constant. The preshared AppKey within the end device is used to generate the AppSKey and NwkSKey keys. While utilizing the activation strategy referred to as ABP, all parameters such as the network session key (NwkSKey), the device address (DevAddr), and the application session key (AppSKey) are configured at production time.