# Artificial Intelligence-Based Autonomous UAV Networks: A Survey
## 3 Autonomous Features in UAV Networks
### Multiple Access and Routing Protocols  
Multiple access and routing protocols are another challenging domain for UAV networks. As UAVs are supposed to be co-located with other networks, the natural choice for multiple access for UAVs was initially space division multiple access techniques [58; 59; 60]. However, as time passes, many researchers have started exploring other techniques that prove to be more efficient in the case of UAV networks. Most of these include orthogonal, non-orthogonal, or rate-splitting techniques. Table 3 provides a summary of related surveys on UAV multiple access and routing protocols. \begin{table}
\begin{tabular}{|c c c c c c c|} \hline
**Scope** & **Autonomous** & **Computational** & **Channel** & **Interference** & **Security and** & **Reference** \\
**Reg.** & **Features** & **Intelligence** & **Modeling** & **Management** & **Safety** & **Reference** \\ \hline \multicolumn{2}{|c|}{Mobility challenges} & - & - & - & \(\surd\) & [45] \\ \hline \multicolumn{2}{|c|}{Resource management} & \multirow{2}{*}{User association} & \multirow{2}{*}{\(\surd\)} & Free-space & \multirow{2}{*}{\(\surd\)} & \multirow{2}{*}{-} & [46] \\ \hline \multicolumn{2}{|c|}{Delay-aware} & \multirow{2}{*}{Trajectory planning} & \multirow{2}{*}{\(\surd\)} & Free-space & \multirow{2}{*}{-} & \multirow{2}{*}{-} & [47] \\ \multicolumn{2}{|c|}{throughput maximization} & & & path loss & & & \\ \hline \multicolumn{2}{|c|}{UAV placement} & \multirow{2}{*}{Energy efficiency and optimization} & \multirow{2}{*}{\(\surd\)} & Path loss out- & \multirow{2}{*}{-} & \multirow{2}{*}{-} & [48] \\ \multicolumn{2}{|c|}{} & & & & & \\ \multicolumn{2}{|c|}{} & & & & & \\ \multicolumn{2}{|c|}{Collision free navigation} & \multirow{2}{*}{Trajectory planning} & \multirow{2}{*}{\(\surd\)} & - & \(\surd\) & - & [49] \\ \hline \multicolumn{2}{|c|}{Swarm-based UAV} & \multirow{2}{*}{Path planning} & \(\surd\) & - & - & - & [50] \\ \hline \multicolumn{2}{|c|}{Physical layer security} & security and cooperation & \(\surd\) & Free-space & \multirow{2}{*}{\(\surd\)} & \multirow{2}{*}{\(\surd\)} & [51] \\ \multicolumn{2}{|c|}{} & & & path loss & & & \\ \hline \multicolumn{2}{|c|}{Secure UAV} & Cooperative & \multirow{2}{*}{\(\surd\)} & Free-space & \multirow{2}{*}{-} & \multirow{2}{*}{\(\surd\)} & [52] \\ \multicolumn{2}{|c|}{} & & & path loss & & & \\ \hline \multicolumn{2}{|c|}{Physical layer security} & Cooperative & \multirow{2}{*}{\(\surd\)} & Free-space & \multirow{2}{*}{\(\surd\)} & \multirow{2}{*}{\(\surd\)} & [53] \\ \multicolumn{2}{|c|}{} & & optimization & & path loss & & \\ \hline \multicolumn{2}{|c|}{Physical layer security} & Cooperative resource & \multirow{2}{*}{\(\surd\)} & Free-space & \multirow{2}{*}{-} & \multirow{2}{*}{\(\surd\)} & [54] \\ \multicolumn{2}{|c|}{} & & allocation & & path loss & & \\ \multicolumn{2}{|c|}{Quality of Experience (QoE)} & \multirow{2}{*}{Cooperative resource allocation} & \multirow{2}{*}{\(\surd\)} & LOS and & \multirow{2}{*}{-} & \multirow{2}{*}{-} & [55] \\ \multicolumn{2}{|c|}{} & & & Non-LOS & & & \\ \hline \multicolumn{2}{|c|}{Secure UAV} & \multirow{2}{*}{UAV defense} & \multirow{2}{*}{\(\surd\)} & - & - & \(\surd\) & [56] \\ \multicolumn{2}{|c|}{} & & & & & \\ \multicolumn{2}{|c|}{} & & & & & \\ \multicolumn{2}{|c|}{} & & & & & \\ \multicolumn{2}{|c|}{} & & & & & \\ \multicolumn{2}{|c|}{} & & & & & \\ \hline \multicolumn{2}{|c|}{Software-defined radio (SRD)} & \multicolumn{2}{c|}{Localization of unwelcomed UAVs} & \multirow{2}{*}{\(\surd\)} & - & \(\surd\) & \(\surd\) & [57] \\ \multicolumn{2}{|c|}{} & & & & & \\ \hline \end{tabular}
\end{table} 
Table 2: _Cont._In orthogonal multiple access techniques, the interference is reduced by ensuring that the simultaneous communications are orthogonal to one another. Multiple research studies [46; 61] have been conducted to achieve this goal. Some propose to use time division multiple access (TDMA) and frequency division multiple access (FDMA) in their system models.