## 1 Introduction
When it comes to emergency communications, the most prevalent type of solution described in the literature are Mobile Ad-hoc Networks (MANETs) [4; 5; 6; 7; 8], due to their ability to bridge long distances through retransmission by intermediate nodes, their self-healing capability (selecting new routes when a node goes offline), and their compatibility with low-cost hardware. However, the presented systems in the literature remain rather abstract. There is no explanation or guidelines for equipment selection, how to power it, the offered data rate, or what is the actual achieved communication range. In addition, while in theory, they are able to provide communication over large areas and are self-healing, the real-world realization of those traits requires a large number of deployed nodes with adequate spatial dispersion, which is not realistic. Moreover, the proposed MANET networks are accessed by the end devices through a single technology, usually WiFi, a practice that is not compatible with the diverse characteristics and requirements of the equipment used by First Responders, as described previously. Another type of communication system gaining popularity for use in emergency and disaster scenarios is LoRaWAN due to its capability to form private networks with standalone concentrators, offering long-range and low power operation. The primary-use case of this kind of system for disaster response is message exchange either between civilians and the authorities to request assistance or civilians themselves to inform their families about their status [9; 10; 11]. LoraWAN is a promising solution, but due to its limited bandwidth, it can not provide a solution on its own, but can rather function as a complementary one. With this article, we present a different approach to providing a communication solution for volunteer USAR teams in cases of emergencies. We propose a system that combines the latest WiFi standard, 802.11 ax, with a LoRaWAN network for local wireless access and a multitude of backhaul interfaces for internet access and communication with the UCC. The combination of 802.11 ax and LoRaWAN addresses the need for medium and long-range wireless connectivity, offering a solution that covers both devices that require considerable bandwidth or low power operation and long-range. For the access to the internet and the UCC, an approach that provides resilience through redundancy has been followed. Since, after a disaster, the civilian communication infrastructure may be unavailable either because it has been damaged or overloaded, our system exploits 4G, xDSL, a Satellite Module, and a Point to Point link for remote access. The Point to Point link can either be used to establish connection to the UCC or a remote location with internet access and the xDSL interface to connect the system with wired infrastructure or some other system deployed in the area, for example, a MANET backbone. The aforementioned interfaces are transparently handled by our system, with traffic being routed based on a predefined interface priority scheme with an automatic switch to a different interface in case of failure. This functionality is provided by a system with the necessary Technology Readiness Level (TRL) to be deployed in the field and meet requirements for ruggedization, fast deployment, and easy transfer. The system has been evaluated within the small and large-scale field tests of the INGENIOUS project [12], and the results are presented here. **Contributions. ** The design and implementation of a novel communication system for volunteer USAR teams, combining 802.11 ax WiFi and LoRaWAN, routes the traffic through multiple backhaul interfaces to achieve resilience through redundancy. The wireless coverage of the system is experimentally evaluated and the real-world performance improvement offered by the new 802.11 ax Wifi standard is determined in practice through a measurement campaign. The rest of the paper is organized as follows. In Section 2, the hardware components of the proposed system are presented.