# An Intelligent Cluster-Based Routing Scheme in 5G Flying Ad Hoc Networks
## 2 Related Work
The performance of the random approach reduces as network density increases as shown in Section 5.7 when the possibility of selecting the best possible action reduces when more options are available with increased network density. Second, in the _optimal approach_, an agent \(i\) selects and takes the optimal action, which is the UAV with lower mobility (or higher stability) and higher residual energy, at all times. This establishes an optimal path from the source UAV to its destination UAV. The optimal path is selected by considering the node conditions, whereby nodes with higher residual energy and lower mobility are selected as next-hop nodes, contributing to improved network lifetime and stability performances. ### Simulation Parameters

Table 6 shows the simulation parameters and values. The units for performance measures are (a) energy consumption is measured in joule, (b) rate of link breakage is measured in percentage, (c) network lifetime is measured in mini-seconds, (d) node mobility is measured in meter per second, and (e) network density is measured in number of nodes. The values are chosen as they provide the best possible results based on our analysis in Section 5.6. Network planes are characterized by node density, node mobility, and transmission range. UAVs with different mobile characteristics are associated with different network plane: (a) low-altitude (i.e., \(\leq\)400 m) and slow-speed (i.e., 0-33.3 m/s) UAVs are associated with the femto plane; (b) medium-altitude (i.e., 401-1100 m) and medium-speed (i.e., 33.4-67.3 m/s) are associated with the pico-plane; and (c) high-altitude (i.e., 1100-2000 m) and high-speed (i.e., 67.4-100 m/s) are associated with the macro-plane. The transmission ranges of UAVs are 10-100 m in femto-plane, 10-300 m in pico-plane, and 10-500 m in macro-plane. The size of a batch is 32 and the replay memory is 2000. Only 32 experiences are taken from the replay memory to train DNN in each episode. When the number of entries in the replay memory reaches its capacity of 2000, the de-queue operation is used to remove the earliest experience from the replay memory, and recent experiences are added. The reason for choosing small values of the batch size and the replay memory is to (a) handle a highly dynamic environment because earlier experiences may not be useful as compared to recent experiences, (b) use recent experiences in the replay memory for learning, and (c) use recent experiences to expedite the learning process in run-time training for DNN in a highly dynamic environment. Each simulation run is performed for 100 iterations, and each iteration has 1000 episodes. After each iteration, the position of UAVs is updated based on mobility. The range of values for network density, node mobility, transmission range, and their distributions in different network planes are shown in Table 5. However, the transmission range is from 10 m to 500 m because some UAVs can transmit data to the entire simulation area, particularly the UAVs in the macro-plane. Our research focuses on vertical clustering and routing. A UAV may send data from a macro-plane to a femto-plane and vice-versa, and intermediate UAVs forward data towards a destination UAV. Similarly, the size of the simulation area is 2 km\({}^{3}\). In this research, the \(\tau\) is set to a single episode \(z\), and so the long-lifetime data does not change within an episode \(z\). ### Energy Model

In UAVs, energy consumption is caused by three mechanisms: (a) the actuating of motor control of a UAV when flying in the air, \(E_{motor}\), (b) communication between sensors \(E_{sensor}\), (c) communication among UAVs, and between UAVs and BS, \(E_{com}\), which is the major cause of energy consumption in UAVs. The equations for the various kinds of energy consumption are as follows [52; 53; 54; 55]. \[E=E_{com}+E_{motor}+E_{sensor} \tag{3}\]

Figure 2:0

Figure 2:1

Figure 2:2

where \(E_{TX}\) and \(E_{Rx}\) are energy consumption during the transmission and reception of data packets, respectively.