# Dynamic Routings in Satellite Networks: An Overview
## 5 Potential Technologies and Future Directions  
Due to cyclical changes in satellite network topology, designing routing technology has always been challenging. Although, there are a variety of multi-layer satellite network routing protocols and algorithms, as previously described, systematic routing algorithms are still lacking. This section discusses the potential technologies and the future directions of multi-layer satellite networks according to the existing works.  
\begin{table}
\begin{tabular}{p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt}} \hline \hline
**Index** & **Physical Layer** & **Datalink Layer** & **Network Layer** \\ \hline \multirow{2}{*}{Delay} & Signal delay, propagation delay & Handover delay, congestion control, retransmission protocol & Handover delay, IP mobility management, routing algorithm \\ \hline \multirow{2}{*}{Reliability} & Channel conditions, path loss, error rate, interference & Forwarding mechanism error & Topological structure \\ \hline \multirow{2}{*}{Energy efficiency} & Power control, channel conditions, interference & Length control, packet retransmission count & Routing protocol \\ \hline \hline \end{tabular}
\end{table}
Table 11: Performance in different layers.  
\begin{table}
\begin{tabular}{p{113.8 pt} p{113.8 pt} p{113.8 pt}} \hline \hline
**Network Structure** & **Reference** & **Proposed Algorithm/Scheme** & **Main Contributions** \\ \hline \multirow{8}{*}{MEO-LEO} & [97] & A delay-based traffic distribution scheme & Sent congested LEO satellite traffic to MEO satellite \\ \cline{2-4}  & [98] & A traffic distribution scheme & The maximum traffic threshold of the link is calculated, allocated overload traffic to MCS satellites \\ \cline{2-4}  & [100] & A traffic-aware routing scheme & Convert the flow problem into a convex optimization issue, maintain high throughput \\ \cline{2-4}  & [101] & A new traffic-balancing algorithm & Improve link utilization with multi-path routing algorithms, data transmission based on the real-time status of the link \\ \cline{2-4}  & [102] & Load-balanced transmission scheme & MEO satellites managed LEO satellites, calculated routing tables, and collected routing information \\ \hline \multirow{2}{*}{Heterogeneous satellite networks} & [106] & An efficient load-balancing scheme & Static and relatively time-invariant grid topology \\ \hline \multirow{2}{*}{SDN-SAG} & [107] & A congestion-aware routing scheme & SDN controller evaluated the blocking of the link, allocated traffic to idle satellite nodes \\ \hline \multirow{2}{*}{Satellite data relay networks} & [101] & A traffic balanced routing algorithm & Extend traffic to any type, launched upper bound on delay in heterogeneous links \\ \hline \hline \end{tabular}
\end{table}
Table 10: _Cont_.  
\begin{table}
\begin{tabular}{p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt}} \hline \hline
**Index** & **Physical Layer** & **Datalink Layer** & **Network Layer** \\ \hline \multirow{2}{*}{Delay} & Signal delay, propagation delay & Handover delay, congestion control, retransmission protocol & Handover delay, IP mobility management, routing algorithm \\ \hline \multirow{2}{*}{Reliability} & Channel conditions, path loss, error rate, interference & Forwarding mechanism error & Topological structure \\ \hline \multirow{2}{*}{Energy efficiency} & Power control, channel conditions, interference & Length control, packet retransmission count & Routing protocol \\ \hline \hline \end{tabular}
\end{table}
Table 11: Performance in different layers.