# 3D Path Planning Algorithms in UAV-Enabled Communications Systems: A Mapping Study
## 4 Results
### RQ3--Are There Approximate Methods for Path Planning in 3D UAVs?
\begin{table}
\begin{tabular}{l c c c c} \hline \hline \multirow{2}{*}{**Algorithm Name**} & \multicolumn{4}{c}{**AC**} \\ \cline{2-5}  & **1** & **2** & **3** & **4** \\ \hline Incremental Gray Wolf Optimizer (I-GWO) & & & x & \\ \hline Algorithm A* & & x & & \\ \hline Lazy theta adaptive algorithm* & x & & & \\ \hline Boundary star fast scan random tree algorithm (boundary-RRT*) & x & & & \\ \hline Rapid Scan Random Trees algorithm (ERRT) & x & & & \\ \hline Model Predictive Control algorithm (MPC) & x & & & \\ \hline Bresenham algorithm & & & x & \\ \hline Modified A* search algorithm & & x & & \\ \hline Artificial Potential Field Algorithm (APF) & x & & & \\ \hline Ant colony algorithm & & & x & \\ \hline Improved ant colony algorithm & & & x & \\ \hline Collision node configuration algorithm & & x & & \\ \hline Speed control algorithm & x & & & \\ \hline Convex Model Predictive Control algorithm (MPC) & & & x & \\ \hline [PERSON]’s algorithm & x & & & \\ \hline Circular Arc Trajectory Geometric Avoidance Algorithm (CTGA) & & x & & \\ \hline Path planning algorithm with an adaptive disturbance operator & & x & & \\ \hline Multiple Limited Energy Heterogeneous UAV Trajectory Planning Algorithm & & x & & \\ \hline Path planning algorithm based on the biogeography algorithm (BBO) & & x & & \\ \hline Improved RRT algorithm & x & & & \\ \hline Cluster head selection algorithm and trajectory planning & & & x & \\ \hline Dynamic training transformation algorithm & & x & & \\ \hline Hierarchical recursive multiagent genetic algorithm HR-MAGA & & x & & \\ \hline \hline \hline \end{tabular}
\end{table} 
Table 11: Heuristic algorithms used by researchers in 3D path planning. AC = Algorithm classification, 1 = Based on Sampling, 2 = Based on Node, 3 = Bioinspired and 4 = Others. \begin{table}
\begin{tabular}{l c c c c} \hline \hline \multirow{2}{*}{**Algorithm Name**} & \multicolumn{4}{c}{**AC**} \\ \cline{2-5}  & **1** & **2** & **3** & **4** \\ \hline Layered Essential Visibility Graphical Algorithm (LEVG) & \multicolumn{4}{c}{x} \\ \hline Ordered Fleet Iterative Algorithm (OFIA) & \multicolumn{4}{c}{x} \\ \hline Step Forward Iterative Algorithm (SFIA) & \multicolumn{4}{c}{x} \\ \hline Linear Quadratic Governor Algorithm (LQR) & \multicolumn{4}{c}{x} \\ \hline Enhanced Sparse Hierarchical Lazy Theta Algorithm (SHLT*) & \multicolumn{4}{c}{x} \\ \hline Algorithms based on radio maps & \multicolumn{4}{c}{x} \\ \hline Fine-grained blocking algorithms & \multicolumn{4}{c}{x} \\ \hline Alignment coefficient on the CAN bus & \multicolumn{4}{c}{x} \\ \hline Creation of part flight corridors (PFC) & \multicolumn{4}{c}{x} \\ \hline Gaussian Distribution and Q-Learning Technique & \multicolumn{4}{c}{x} \\ \hline Energy Efficiency A* (EEA*) & \multicolumn{4}{c}{x} \\ \hline The pseudospectral method (GPM) & \multicolumn{4}{c}{x} \\ \hline grid method & \multicolumn{4}{c}{x} \\ \hline golden eagle optimizer & \multicolumn{4}{c}{x} \\ \hline Energy Efficiency Optimizer & \multicolumn{4}{c}{x} \\ \hline Particle Swarm Optimizer (PSO) & \multicolumn{4}{c}{x} \\ \hline Particle Swarm Optimizer (PSO) with Harmony Search Algorithm (HSA) PSO-HSA & \multicolumn{4}{c}{x} \\ \hline Particle Swarm Optimizer (PSO) with PSO-GA Genetic Algorithm (GA) & \multicolumn{4}{c}{x} \\ \hline Improved particle swarm optimizer called HACLDMS & \multicolumn{4}{c}{x} \\ \hline Multi-target particle swarm optimize & \multicolumn{4}{c}{x} \\ \hline ray Wolf Optimizer (GWO) & \multicolumn{4}{c}{x} \\ \hline Improved Gray Wolf Optimizer (GWO) & \multicolumn{4}{c}{x} \\ \hline Global Brainstorming Optimizer Based on Cross Recombination (GBSO-CR) & \multicolumn{4}{c}{x} \\ \hline Expanded Gray Wolf Optimizer (Ex-GWO) & \multicolumn{4}{c}{x} \\ \hline Multi-Objective Optimization Problem (MOP) & \multicolumn{4}{c}{x} \\ \hline Partially Observable Markov Decision Process (POMDP) & \multicolumn{4}{c}{x} \\ \hline \hline \end{tabular}
\end{table} 
Table 11: _Cont._  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline