I. Introduction
With the development of Unmanned Aerial Vehicle (UAV) technology and the prosperity of UAV market, UAVs have appeared more and more frequently in our daily life. According to the report of Businessinsider [1], UAV services market size is expected to grow to 63.6 billion by 2025. UAV can be applied in a variety of scenarios, such as intelligent agriculture [2], [3], smart city [4], and emergency relief [5].