## 2 Energy-Aware Multi-UAV Dispatch Algorithm (EAMUD)
### The Energy Model of UAV Battery
#### 2.2.2.  
Energy Consumption of the UAV Battery  
There are two kinds of energy consumption on UAV communication. One is the transmission power of the U2U link between adjacent UAVs and the other is that of the U2V link for connecting the edge UAV in FANET and the edge vehicle in VANET. In the following, we will discuss how to convert the transmission power into corresponding energy consumption for the U2U and U2V links, respectively.  
\(\blacksquare\)_Energy consumption for the U2U communication_  
Assume there are no obstacles between UAVs, hence the U2U link belongs to the LoS type. For two adjacent UAVs to maintain an U2U link, the required transmission power, i.e., \(P_{tU2U}\), in unit of dBm at the U2U sender must be larger than the SNR threshold, i.e., \(SNR_{t\text{U2U}}\), at the receiver, which is formulated as follows [25]:  
\[P_{tU2U}\geq SNR_{t\text{U2U}}+PL+N_{tU2U} \tag{2}\]  
where \(PL\) is the free space loss between UAVs and \(N_{tU2U}\) is the noise power at the U2U receiver. The value of \(PL\) is equal to \(10\log\left[\left(\frac{4\pi\times f_{1}}{C}\right)^{2}\times d_{u2u}{}^{2}\right]\), where \(f_{1}\) is the carrier frequency, \(C\) is the light speed and \(d^{u2u}\) denotes the Euclidean distance between UAVs.  
Figure 1: The two-layer Flying Ad hoc Network-Vehicular Ad hoc Network (FANET-VANET) network in disaster.  
Finally, the required transmission power \(P_{tU2U}\) in unit of dBm is converted to \(E_{tU2U}\) in unit of watt for the U2U sender as follows:  
\[E_{tU2U}(\text{W})=(1 mw)^{10^{\frac{P_{tU2U}}{10}}}\times 10^{-3} \tag{3}\]  
\(\blacksquare\)_Energy consumption for the U2V communication_  
Because the U2V connection between the edge UAV and vehicle is a combination of LoS and NLoS communication, the required transmission power, i.e., \(P_{tLU2V}\), in LoS and that, i.e., \(P_{tNUL2V}\), in NLoS consumed by the U2V sender can be formulated as follows, respectively [25].  
\[P_{tLU2V}\geq SNR_{t\text{thU2V}}+PL+\xi_{LoS}+N_{U2V} \tag{4}\]  
\[P_{tNUL2V}\geq SNR_{t\text{thU2V}}+PL+\xi_{NLoS}+N_{U2V} \tag{5}\]  
For connecting the edge UAV and vehicle through LoS communication, Equation (4) means that \(P_{tLU2V}\) in dBm must be no less than the sum of the SNR threshold, i.e., \(SNR_{t\text{thU2V}}\), at the U2V receiver, the free space loss \(PL\), the shadow fading with normal distribution \(\xi_{LoS}\sim N\big{(}\mu_{LoS},\delta_{LoS}^{2}\big{)}\) and the noise power \(N_{U2V}\) over the LoS U2V connection. Please note that \(\mu_{LoS}\) and \(\delta_{LoS}^{2}\) are the mean and the standard deviation of the shadow fading for the LoS link. Similarly, Equation (5) formulates the relationship among \(P_{tNUL2V}\), \(SNR_{t\text{thU2V}}\), \(PL\), \(\xi_{NLoS}\) and \(N_{U2V}\), where \(\xi_{NLoS}\sim N\big{(}\mu_{NLoS},\delta_{NLoS}^{2}\big{)}\) is the shadow fading with normal distribution over the NLoS U2V connection. According to [25], the probability of the LoS U2V connection, i.e., \(P_{LoS}\), is computed as follows:  
\[P_{LoS}=\frac{1}{1+B\cdot\exp[-C\cdot(\theta-B)]} \tag{6}\]  
where \(B\) and \(C\) are constant values for different propagation environment. \(\theta\) is the elevation angle between the ground and the U2V link. Hence, the probability of the NLoS U2V connection, i.e., \(P_{NLoS}\), is equal to \(1-P_{LoS}\). Then the average required U2V transmission power \(P_{tU2V}\) in dBm is modelled as follows:  
\[P_{tU2V}=P_{tLU2V}\times P_{LoS}+P_{tNUL2V}\times(1-P_{LoS}) \tag{7}\]  
where \(P_{tU2V}\) is the weighted sum of \(P_{tLU2V}\) and \(P_{tNUL2V}\), depending on \(P_{LoS}\) and \(1-P_{LoS}\), respectively. Finally, the transmission power \(P_{tU2V}\) in unit of dBm is converted to \(E_{tU2V}\) in unit of watt for the U2V sender using Equation (3).