# Performance Evaluation of UAV-Enabled LoRa Networks for Disaster Management Applications
### Related Work  
[PERSON] et al. [15] conducted empirical measures to determine the maximum range of LoRa in a small rural city in Finland. The results show that, by using the maximum Spread Factor (SF) and a bandwidth of 125 kHz in the 868 MHz band, the signal can reach the gateway from a 15 km distance on the ground and 30 km on water, with increments of the Packet Drop Rate (PDR) proportional to the distance. The authors of [16] have performed a similar analysis in a medium-density urban area, noting in this case, that the maximum range under the same conditions described in [15] is only 5.8 km, mainly due to the presence of obstacles in the line-of-sight. [PERSON] et al. in [17] proposed the concept of flying gateways for enabling communication between IoT and UAV networks. Though their work used Raspberry Pi boards, they expected to improve the performance of the network using LoRa devices. In [18], the signal reception in presence of indoor end devices is also evaluated. The authors report that at a distance of 1.2 km from the gateway the PDR is already between 60% and 90%. The authors conclude that the presence of line-of-sight is particularly important and that LoRa is not suited for indoor environments if long-range and low PDR is required. The importance of line-of-sight is also outlined by [PERSON] et al. [19]. In this case, the experiments were conducted in a forest environment in the presence of numerous trees between the transmitter and the receiver. In the experiment, the transmitter was moved further and further away from the receiver and at around 90-100 m the signal was completely lost. The authors conclude that vegetation has a huge impact on LoRa signal propagation, in fact dropping the maximum achievable range by an order of magnitude. The use of the chirp spread spectrum, a variation of Direct Sequence Spread Spectrum (DSSS), makes the LoRa modulation very resilient to noise. This assumption is verified by [PERSON] et al. [20]. In the experiment, different levels of white Gaussian noise are applied to the signal starting with a minimum signal-to-noise ratio of \(-\)10 dBm. As expected, the use of a smaller bandwidth and, more significantly, the use of a higher SFimproves the performance of the modulation. The coding rate, on the other hand, has a less significant impact on the performance in noisy environments. [PERSON] et al. in [21] developed a module that models a subset of functionalities of the LoRaWAN physical and MAC layers. Each end device has an associated class that models the behavior of a LoRa chip and tracks its state (standby, sleep, transmission or reception). The only difference is in the fact that their proposed scheme defines 8 parallel reception paths, each one of them able to lock on an incoming packet on a given frequency. Their results show considerable improvement using the developed LoRa module. [PERSON] et al. in [22] proposed a model similar to the one previously described. The main difference resides in the way in which inter-device interference is computed. In this case, instead of using a signal-to-interference matrix, the authors performed a series of complex MATLAB baseband simulations to measure the Bit Error Rate (BER) of a set of LoRa configurations over a white Gaussian noise channel. The BER points are then used to determine the BER curve that is then used to decide if a packet is lost for interference or not. [PERSON] et al. [23] consider a distributed decision approach to maintain a coherent mesh network of UAVs with the objective of exploring a 3D area. The swarm has also the additional requirement of keeping the connectivity to a ground base station. Two scenarios are studied by the authors: one in which the connectivity to the base station is permanent and one in which some disconnections are allowed for the purpose of extending the exploration. [PERSON] et al. [24] propose a distributed approach similar to [23], but based on VSFs. The UAV mesh network described in the paper is used to give coverage to a set of partitioned ground nodes.