# Emergency Communication System Based on Wireless LPWAN and SD-WAN Technologies: A Hybrid Approach
###### Abstract  
Emergency Communication Systems (ECS) are network-based systems that may enable people to exchange information during crises and physical disasters when basic communication options have collapsed. They may be used to restore communication in off-grid areas or even when normal telecommunication networks have failed. These systems may use technologies such as Low-Power Wide-Area(LPWAN) and Software-Defined Wide Area Networks (SD-WAN), which can be specialized as software applications and Internet of Things (IoT) platforms. In this article, we present a comprehensive discussion of the existing ECS use cases and current research directions regarding the use of unconventional and hybrid methods for establishing communication between a specific site and the outside world. The ECS system proposed and simulated in this article consists of an autonomous wireless 4G/LTE base station and a LoRa network utilizing a hybrid IoT communication platform combining LPWAN and SD-WAN technologies. The LoRa-based wireless network was simulated using Network Simulator 3 (NS3), referring basically to firm and sufficient data transfer between an appropriate gateway and LP-WAN sensor nodes to provide trustworthy communications. The proposed scheme provided efficient data transfer posing low data losses by optimizing the installation of the gateway within the premises, while the SD-WAN scheme that was simulated using the MATLAB simulator and LTE Toolbox in conjunction with an ADALM PLUTO SDR device proved to be an outstanding alternative communication solution as well. Its performance was measured after recombining all received data blocks, leading to a beneficial proposal to researchers and practitioners regarding the benefits of using an on-premises IoT communication platform. emergency communication systems; off-grid areas; critical infrastructures; LPWAN; SD-WAN; IoT platform; MATLAB; NS3 20232  
when a signal is relayed by the satellite through a transmission, we should also consider other timing group delays [3, 4]. On the other hand, LPWANs are a promising technology for wireless communication networks. Widespread technologies such as LoRaWAN, Sigfox, NB-Fi, and mioty have developed rapidly, and many LPWAN networks have been deployed in various countries. Although LoRaWAN, Sigfox NB-Fi, and mioty were designed for similar applications, they use different approaches. A typical LPWAN network has a star-of-stars topology consisting of end devices (nodes), gateways, and a server. In the considered LPWANs, gateways communicate with the server through a broadband link. The end devices communicate with the server via wirelessly connected gateways, while the gateways act in a similar way to transparent retransmitters between the sensors and the server. LPWAN networks impose limitations on the emitted power as they operate on unlicensed ISM radio bands [5]. They can enable low-cost applications over large areas, while LPWAN devices can cover distances of more than 10 km with typical transmission powers of 10 mW. This feature is achieved by transmitting very low payload bit-rates of a few kBit/s between the nodes and the highly exposed gateway antennas placed on top of high buildings or broadcast towers [6]. Moreover, LPWAN technology is suitable for dense or thick locations for long-term monitoring applications and is the best technology that can send small packets of data over long distances for a long time as it supports long battery life [7]. One of the most promising LPWAN technologies for sensor networks is Long-Range (LoRa) technology. It provides a novel wireless communication protocol that compromises data rate and time-on-air to achieve low power consumption and long-distance transmissions. LoRa is appropriate for spare transfer applications with relatively small payloads because of its limited transmission bandwidth.