# Handover Scheme in LEO Satellite Networks Based on QoE for Streaming Media Services
## 1 Introduction  
With the development and popularization of 5G technology, more and more users are enjoying higher quality communication services. Compared with the characteristics of 5G, such as ultra-low latency, high reliability, ultra-high speed and massive terminal access, the future 6G must solve another problem--coverage [1]. However, providing full coverage via fixed terrestrial cellular infrastructure is prohibitively costly in sparsely populated regions. To overcome this limitation, integrating non-terrestrial networks (e.g., satellites) has emerged as a key strategy for 6G evolution [2]. For instance, large-scale LEO constellations (e.g., OneWeb and Starlink) have been deployed and are already operational. In addition, Huawei's Tiantong Satellite (geosynchronous orbit satellite) mobile phone direct call service [3], in cooperation with China Telecom Group and other enterprises, has been put into commercial use, making it possible to use 2G services in some areas without cellular network coverage. Beyond basic calls and SMS, future satellite communications aim to deliver multimedia services and ubiquitous Internet access [4]. Multimedia services will have higher requirements on QoS metrics such as transmission rate and delay [5], and different multimedia services will have different requirements on QoS metrics due to different QoE requirements. Unlike QoS, which measures the performance of communications or the network themselves, QoE captures users' subjective perception of service quality, encompassing factors such as effectiveness, availability, and application-specific comfort levels. As one of the important components of the multimedia service, an on-demand streaming media service has special requirements for QoS metrics such as bandwidth to meet users' QoE needs due to its download-while-playback and buffering mechanisms. However, QoE-centric studies of on-demand streaming media in satellite environments remain scarce. In addition, satellites are resource-constrained platforms with limited power and bandwidth, and the orbital velocity of LEO satellites is very fast, which makes streaming media transmission very different from fixed base stations on the ground. Therefore, it is of great significance to establish a simulation system for streaming media transmission under the satellite platform and to improve the QoE of users by the rational allocation of satellite resources according to the current satellite parameters. Existing simulation studies primarily focus on QoS-level evaluations. For example, both [6; 7] work on performance evaluation of the 3 GPP-compliant 5G conditional handover (CHO) in LEO-based non-terrestrial networks. Ref. [6] verified some QoS performance of CHO as specified in 3 GPP Rel-16 in non-terrestrial network (NTN) systems, such as Signal-to-Interference-and-Noise Ratio (SINR), the number of handover failures, the dwell time, and the ping-pong effect. In contrast, ref. [7] compares the traditional measurement-based handover triggering mechanism with other alternatives (e.g., based on distance, elevation angle, etc.) according to the 3 GPP model for system-level simulation and performance comparison. The performance evaluation criteria are again limited to the QoS level. As for the research on schemes for LEO satellite handover, ref. [8] proposed an algorithm for channel-preserving load-aware handover to enhance the QoS and overall system satisfaction. Based on the three-attribute optimal handover problem, the optimal handover scheme is searched by combining the idea of reserving channels for important users. Ref. [9] leveraged the relatively low velocity of high-speed trains (compared to LEO satellites) to design an integrated terrestrial-satellite network, mitigating channel fluctuation and handover frequency in traditional terrestrial systems. Ref. [10] observed that users exhibit time-varying service preferences and proposed a user dynamic preference-based LEO satellite handover strategy for users on airplanes.