One of the most important issues in the analysis and design of wireless communication systems is investigate of its coverage and efficiency. Coverage efficiency means providing maximum communication coverage and establishing quality communication with users, which maximizing it is one of the main goals in designing new and advanced fifth generation communication systems. In this thesis, we intend to provide communication coverage in the urban environment by using UAVs as aerial BS. First, the factors affecting the efficiency of the coverage by UAVs and the challenges and advantages of these systems are examined. In order to improve the interference situation, we equip drone systems with directional antennas and examine the height of UAVs relative to cells with different congestion using symmetric and asymmetric methods, and finally, control the intercellular interference according to the composition of the directional antenna, symmetric and asymmetric height and frequency reuse. Then we examine the problem of maximum coverage with the minimum number of UAVs and provide a mathematical model to examine all the coverage limitations in the urban environment. Then, we introduce an innovative solution algorithm to improve the coverage situation in the urban environment and examine the system functions for different congestion conditions.
