# Study on Drone Handover Methods Suitable for Multipath Interference Due to Obstacles
## 1 Introduction
In addition, we evaluated the proposed methods. The reason for developing the cross-layer simulator is that when a drone communicates while flying, unlike cellular communication, etc., on the ground, it is necessary to assume a three-dimensional communication environment. Reflections and diffraction of radio waves due to buildings and other obstacles vary in complexity that depends on the drone's flight altitude and speed. When considering the communication quality in such a communication environment, it is necessary to evaluate performance in a three-dimensional space considering the propagation characteristics. For cellular communications on the ground, the location selection of base stations are performed not only by computer simulation, but also by demonstration experiments to verify the optimal installation of base stations and the quality of communications. On the other hand, when the drones communicate while flying, the selection of base station locations by actually flying is a very labor-intensive and expensive task. Although computer simulations can evaluate propagation characteristics in a three-dimensional space, it is difficult to evaluate the performance and services of a communication system, including its applications. For this background, an evaluation method suitable for the environment of drone communications is required, and because verification through actual experiments is difficult, a virtual reality simulator for evaluation in a virtual space is needed. In this study, to achieve this simulator for evaluation, we developed the cross-layer simulator that integrates propagation characteristics, signal processing, and communication protocols such as an IP layer. The contributions of this paper are summarized as follows. * We propose a handover method based on signal-to-interference-plus-noise ratio (SINR) that includes multipath interference considering obstacles such as buildings in the environment where drones fly, instead of simple received power. Then, the effectiveness of the method was confirmed. * We proposed a method to solve the problem of locally high SINR during the period when drones are flying and the communication speed is reduced due to frequent handovers, confirmed the effectiveness of the method, and determined the optimal flight speed. * Because drone communications are subject to significant changes in reflection and diffraction from buildings and other objects depending on flight speed, the new cross  
Figure 3: Example of service using a drone as a radio station. layer simulator was developed to determine throughput characteristics above the IP layer, including multipath interference due to propagation characteristics and signal processing performance, enabling evaluation in a three-dimensional virtual space close to the actual environment. The remainder of this paper is organized as follows. Section 2 describes the related works and problems associated with conventional relay technology. Section 3 describes the evaluation method and simulator development for the drone relay network for flight. Section 4 describes the two proposed methods and presents evaluation results.