## 5 Practical Issues
### LoRa  
Semtech, the developer and creator of LoRa technology, suggested LoRa, which is a wireless platform designed for the Internet of Things (IoT). LoRa, which stands for long range, is a spread spectrum modulation technique based on chirp spread spectrum (CSS) technology. It is known for its long-range capabilities and low power consumption, making it the preferred choice for IoT applications ([33]). Our comparison is made considering three main viewpoints: range as the most important factor, power consumption, data rate and availability. LoRa is a versatile technology that can be used with any computing unit that has a free SPI (serial peripheral interface) interface. This makes it simple to integrate the network interface with different MCUs. Additionally, the affordability of LoRa makes it a practical physical layer for IoD applications. **Bluetooth:** Although Bluetooth has low power consumption and is readily available, its range of 100 m makes it unsuitable for integrating into an IoD network because UAVs typically fly farther apart from each other than 100 m. As a result, the excellent properties of Bluetooth, such as bandwidth and connection reliability, are rarely used ([34]). **Bluetooth low energy:** BLE has a longer-range mode that can cover up to 1000 m, making it suitable for a wider range of scenarios than regular Bluetooth. While it may not be ideal for large groups, BLE can transfer large amounts of data, such as images and videos, for a group of UAVs within a 1 km radius and part of the same network ([34]). **WiFi:** It is a wireless technology based on radio data transmission. However, it is unsuitable for IoD since it has an even shorter maximum effective range than Bluetooth on 2.4 GHz (approximately 45 m indoors and 70 m outdoors using the 802.11 n protocol), making it an even less capable technology for IoD purposes. [35]. **Cellular:** The first viable technology for implementing an IoD network is 4G LTE. It has a significantly longer range that varies depending on the band it uses and terrain conditions, with low band having a range of approximately 40 km, mid-band ranging from 1.6 km to 12 km, and high band ranging from 15 to 600 m. Fourth-generation LTE also offers high data rates, particularly at lower frequencies, which, combined with its excellent range, makes it an excellent physical layer for the Internet of Drones applications. Fourth-generation LTE outperforms the overall capabilities of LoRa in various use cases and environments. Its most significant advantage is its range and flexibility, as well as its direct access to the internet ([36]). However, 4G LTE also has several drawbacks, including high power consumption, which can be significantly higher than that of LoRa when transmitting. At maximum transmit power, tested with an sx1278 LoRa module, the power consumption of LoRa is around 370-400 mW at 20 dBm transmit power, while that of SIMCOM SIM7600E-H is around 3 W at 22.5 dBm transmit power. Additionally, 4G LTE comes with high costs due to service provider fees and the cost of modules. It is also heavily reliant on tower coverage and service providers, meaning that if UAVs venture into areas which are not covered by cellular towers, the devices lose connection to the network, leading to device and data loss. Furthermore, it may become unable to complete the mission without crucial data provided by other devices. As a result, the use of cellular networks has been deemed unsuitable for IoD applications that require precision agriculture and military service, eliminating two of the most significant use cases. While cellular networks may be a viable solution for IoD networks placed in or near populated areas in developed countries, where 4G cellular coverage extends to 99% of these areas, this cannot be guaranteed in developing countries. Even if placed near populated areas, coverage may be limited, with 3G cellular coverage in developing regions such as Sub-Saharan Africa barely reaching 75%, despite rapid infrastructure expansion ([37]).