# 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  
According to the LoRa Alliance technology group, which is supported by over 500 members being operational since the end of March 2015 [23], a considerable number of devices anticipated for the Internet of Things are expected to be supported by Low-Power, Wide-Area Networks (LPWAN) (IoT) [24]. Among these alliance members, technology leaders such as IBM, Cisco, HP, Fox-conn, Semtech, and Sagemcom, as well as companies such as Schneider, Bosch, Diehl, and Mueller, and many small and medium-sized enterprises (SMEs) and startup companies cooperate to consolidate on the LoRaWAN(r) standard for optimizing LPWANs battery life, capacity, range, and cost. A Low Power Wide Area (LPWA) networking protocol named LoRaWAN is used to wirelessly link battery-powered \"things\" to the internet in local, national, or global networks. The LoRaWAN [25] protocol criteria that focus on the IoT are bi-directional communication, mobility, end-to-end security, and localization services. LoRaWAN is an open and standardized low-power wireless network (LPWAN). Table 2 shows a performance comparison between the most popular LPWAN technologies [26; 3]. \begin{table}
\begin{tabular}{p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt}} \hline \hline
**Survey** & **Communication Technologies** & **Contribution** & **Evaluation** \\ \hline
[3] & LTE/4G, SD-WAN & Emergency System for Cruise Ships & Implementation \\ \hline
[11] & LPWAN, LoRa & Search and Rescue (SAR) Robot & Implementation \\ \hline
[12] & LPWAN, LoRa & Emergency Communication System in IoT & Implementation \\ \hline
[13] & LoRa, Bluetooth & Off-grid Emergency Communications & Simulation Implementation \\ \hline
[14] & LPWAN, Sigfox, GSM & IoT Surveillance System for Outdoor Fire Detection & Implementation \\ \hline
[15] & SD-WAN & Low-Cost Earthquake Early Warning System & Simulation Implementation \\ \hline
[16] & SDN, SD-WAN & Securing the Industrial IoT for Critical Infrastructure & Case study \\ \hline
[17] & SD-WAN, 4G & SD-WAN Technology in Power Communication Scenarios & Case study \\ \hline
[20] & 4G/LTE & Electric Power Emergency Communication Design & Case study \\ \hline
[21] & UAV, 5G and Beyond in Case of Disasters & Emergency Communication Systems in case of Disasters & Simulation Case study \\ \hline
[22] & USN & Communication Technologies in Emergency Situations & Case study \\ \hline Proposed ECS & LTE/4G, SD-WAN & Emergency Communication System in case of Disasters & Simulation Implementation \\ \hline \hline \end{tabular}
\end{table} 
Table 1: ECSs Comparison. The underlying physical layer or the wireless modulation utilized to create the long-range communication link is LoRa [24, 27], or Frequency Shift Keying (FSK), a chirp spread spectrum-based proprietary modulation scheme (CSS). FSK modulation is frequently used in wireless systems because it is a very effective modulation for low-power achievement. Chirp spread spectrum modulation, the foundation of LoRa, keeps the low-power properties of FSK modulation while greatly extending the communication range. Because of the great reached communication distances and robustness to interference, the chirp spread spectrum has been used in military and space communication for decades; nonetheless, LoRa is the first low-cost implementation for commercial use that offers the benefit of long-range capability. Entire cities or even areas covering hundreds of square kilometers may be covered by merely one gateway or base station offering a high link budget, although the range highly depends on the environment or obstructions in a given location. The link budget, typically given in decibels (dB), is the primary factor in determining the range in a given environment. Scalable bandwidth, constant envelope, low power, a quite robust scheme, multipath, fading resistance, Doppler resistance, long-range capability, enhanced network capacity, and geolocation capabilities are some of the key properties of this modulation.