# Handover Scheme in LEO Satellite Networks Based on QoE for Streaming Media Services
## 2 System Model
### Streaming Media Transport Model  
Streaming media technology refers to a series of media data compression in order to achieve progressive download (PD) transmission to the user terminal and realize the real-time transmission of audio and video on the network of a technology. Streaming media services can be further classified as on-demand streaming and live streaming. Common web video/music playback all belong to on-demand streaming media services, while web live or client live is live streaming media services. In this paper, we consider the handover of on-demand streaming services in satellite communications, as shown in Figure 2.  
In Figure 2, \(H_{v}\) is the size of the streaming media file, whose unit is bit; \(R_{d}\) is the transmission rate from the satellite to the terminal and its unit is bps; \(R_{v}\) is the bit rate of the media file, which is related to the resolution of the video or the sound quality of the audio as well as the compression scheme, and the unit is bps; \(H_{b}\) is the playback threshold of the media file, whose unit is the same as \(H_{v}\); \(H_{b}\) is the amount of data occupied by the specified streaming media duration \(T_{b}\) (in seconds); \(H_{buff}\) is the buffer capacity, and its unit is the same as \(H_{v}\). Streaming media files, such as video or audio, are compressed by streaming media-specific encoding and then transmitted from the server in the form of streaming media packets through the NTN to satellites and finally directly to user terminals through the satellite-terrestrial network. When a streaming media file is transmitted to a terminal, it is first stored in a preloaded area (called buffering) for a period of time. When the duration of the video in its buffer exceeds the playback threshold \(H_{b}\), the file begins  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Symbol** & **Loss Factors** & **Symbol** & **Loss Factors** \\ \hline \(L_{f}\) & free space loss & \(A_{c}\) & cloud attenuation \\ \hline \(A_{o}\) & oxygen attenuation & \(A_{r}\) & rainfall attenuation \\ \hline \(A_{w}\) & water vapor attenuation & \(A_{s}\) & tropospheric scintillation \\ \hline \hline \end{tabular}
\end{table}
Table 1: Link loss factors and their symbols.  
Figure 2: Streaming media transmission in satellite communication.  
to play. During media playback, streaming data packets are sequentially extracted from the buffer, decoded, and rendered for user viewing. The buffer depletion rate precisely matches the media bitrate, while concurrent satellite downlink transmission continuously replenishes the buffer, enabling real-time streaming functionality through simultaneous download and playback. Because the streaming data generated by compression coding are in blocks, the buffer must have at least one complete block of data to play. If the average transmission speed is less than the bit rate of the video, the buffer will be depleted after a period of time, and the application will pause the media playback and rebuffer it until the amount of data in the buffer reaches the playback threshold again. If the remaining playback time of a video or audio file is less than the playback threshold, then the remaining video or audio content will be loaded before reaching the threshold and played directly.