## 4 LoRaWAN Issues and Recent Solutions
### Coverage Range and QoS  
LoRa coverage is based on the deployment scenario of LoRa nodes and the LoRaWAN gateway in addition to the parameters of transmission, particularly the SFs, transmit power, channel bandwidth, and environmental conditions. Many empirical studies were conducted to assess LoRa coverage for both outdoor and indoor connectivity. Although LoRaWAN has a long range, especially in rural areas, and can perform well in dense deployment with obstacles, it may suffer from coverage problems. Furthermore, there is an inverse relationship between the data rates and connectivity range, which results in unacceptable performance for many industrial applications. In [53], a measurement campaign conducted in a flat city in Finland is presented. The authors placed the gateway on an antenna tower 24 m above sea level. The study results compared the loss ratio of the transmitted packets and the RSSI based on the distance between the gateway and end nodes. Coverage up to 10 km was achieved with 33% packet loss. For the open sea area, the packet loss was 31% for ranges up to 15 km and 38% for ranges up to 30 km. This proves that LoRa can perform well up to 5 km, and then the network performance is degraded. In the study, the authors did not consider the ADR. In [54], the authors proposed a test methodology for experimentally evaluating the coverage of LoRaWAN coverage in a smart campus. The proposed scheme focused on the device definition, methods, and procedures. The method depends on a mapping phase to highlight the coverage of LoRaWAN in the tested environment. The method validation was carried out through a use case, and the obtained results demonstrated the effectiveness of the proposed methodology. An empirical study was conducted in [55] to investigate the radio channel of LoRaWAN radio in the 868-MHz frequency band via comprehensive measurement campaigns in urban and rural areas for indoor and outdoor environments. The authors proposed a path loss model based on the results for LoRaWAN communications and compared it with the conventional models. Furthermore, the study evaluated the performance of LoRaWAN deployment based on real measurements in terms of coverage. The authors claimed that the proposed models were simple and accurate, and the achieved coverage ranges in urban areas were 8 km, while in rural areas, they reached 45 km. The overall conclusion reached is that larger spreading factors (SF12) may easily achieve coverage ranges of 5 km or greater in urban contexts, whereas lower spreading factors can achieve coverage ranges of under 5 km or greater in urban situations (SF7). In [56], the authors suggested that LoRa+ should be a new method to address LoRaWAN's QoS constraints. The research changed the LoRaWAN MAC layer for Class A and Class B such that the time space assigned to receive the channel parameters was moved instead of waiting for the packet transmission to conclude, as in the LoRaWAN standard. Those parameters are supplied before the transmission slot. Based on the simulation results, the authors claimed that the modified LoRa+ approach significantly decreased the required number of gateways and decreased the rate of error and rejected packets in comparison with LoRaWAN in small- and medium-sized networks [57]. By fine-tuning chosen radio characteristics, researchers have presented a simple and practical technique for improving the quality of service (QoS) of LoRaWAN. When optimizing the SF and CF parameters of LoRa, it is necessary to consider the LoRaWAN network traffic to improve the DER while simultaneously reducing the packet collision rate and the amount of energy spent. LoRaSim simulations demonstrate that the suggested optimization technique is successful in terms of boosting the DER, reducing the number of collisions, and conserving energy, as demonstrated by the results. The research in [58] might be used to profile IoT devices, classify them based on their features, and detect network irregularities, among other uses.