Читать книгу Autonomous Airborne Wireless Networks - Группа авторов - Страница 14

The need for an appropriate type of UAV depends on the specific mission, environmental conditions, and civil aviation regulations to attain certain altitude. In addition, for any particular UAV‐enabled wireless networking application, several factors, such as the number of UAVs, their optimal deployment, and QoS requirement, must be taken in to account. The operational altitude of the UAV from the ground level can be categorized as LAP and HAP. UAVs in LAP can fly between the altitude ranges from tens of meters to a few kilometers [4]. However, civil aviation authorities of some countries have set the operational altitude of UAVs up to a few hundred meters to avoid airborne collision with commercial flights. For example, Table 2.1 lists the regulations of maximum allowable LAP deployment of UAVs in various countries without any specific permit [5]. HAPs, on the other hand, have altitudes above 17 km where UAVs are typically quasi‐stationary [1,4].

Table 2.1 Regulation for LAP deployment of UAVs in different countries.

Country	Maximum altitude (m)	Minimum distance to humans (m)	Minimum distance to airport (km)
US	122	—	8
UK	122	50	—
Chile	130	36	—
Australia	120	30	5.5
South Africa	46	50	10

For time‐sensitive applications such as emergency services, LAPs are more appropriate then HAPs due to their rapid deployment, quick mobility, and cost‐effectiveness. Furthermore, LAPs can be used for collecting sensor data from the ground. In this case, LAPs can be readily replaced or recharged as needed. In contrast, HAPs are preferred due to their long endurance (days or months) operations and wider ground coverage [1]. However, operational cost of HAPs is high and their deployment time is significantly longer.

UAV can also be categorized based on their structure into rotary‐wing and fixed‐wing UAVs. Rotary‐wing UAVs are powered by rotating blades, and based on the number of blades they are termed as either quadcopter with four blades, hexacopter with six blades, or octocopter with eight blades. On the other hand, fixed‐wing UAVs include those that are driven by propellers with small size engine and have wings that are fixed. However, the flight time of UAVs relies on several key factors, such as type, weight, speed, energy sources (battery or engine), and trajectory of the UAV.

Figure 2.1 Aerial user equipment and aerial base station.