# TARCS: A Topology Change Aware-Based Routing Protocol Choosing Scheme of FANETs
## 4 Evaluations and Results
### Validation of TARCS  
This experiment mainly verified the difference in network performance with or without TARCS. The aware interval is set to 50 s, which means that the topology is perceived 13 times with each rate. Since the \(TCD_{TH}\) are different with different node numbers and node rates, it is necessary to preliminarily set the \(TCD_{TH}\) according to the node rate and the specific mobility model. In this experiment, when node speed is 50 m/s the \(TCD_{TH}\) is set as follows:  
\[\left\{ \begin{array}{c}TCD_{\text{TH}}(RWP,RPGM(g=5))=150\\ TCD_{TH}(RPGM(g=5),\ Pursue)=1000\end{array} \right. \tag{5}\] \begin{table}
\begin{tabular}{c c} \hline \hline
**Parameters** & **Values** \\ \hline Simulation region & 2000 m \(\times\) 2000 m \\ Node number & 50 \\ Mobility Model & Chain: RWP + RPGM (g = 5) + Pursue \\ Simulation Time & 602 s \\ Node speed & 50 m/s, 500 m/s \\ Route protocol & OLSR / AODV / DSDV \\ Propagation model & Free space propagation model \\ Delay model & constant speed propagation delay model \\ Data mode & CBR \\ Packet size & 1024 bytes \\ Data rate & 16 Kbps \\ MAC protocol & IEEE 802.11 bDCF \\ Transmission range & 140 m \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Parameters of simulation experiments. The meaning of \(TCD_{TH}(RWP,RPGM(g=5))\) is the threshold of the network TCD distinguishing from motion with the RWP mode and the RPGM (g = 5) mode. Assuming \(\mathrm{TCD_{htwrk}}\) is the newly acquired TCD value of the whole network, the criteria are:  
\[mobility\ model=\left\{ \begin{array}{ll}RWP&if\ TCD_{ntwrk}<TCD_{TH}(RWP, RPGM(g=5))\\ RPGM(g=5)&if\ TCD_{ntwrk}>TCD_{TH}(RWP,PGM(g=5))\end{array} \right. \tag{6}\]  
Similarly, \(\mathrm{TCD_{TH}(RPGM(g=5),Pursue))}\) represents the TCD threshold value that can distinguish between motion in RPGM (g = 5) mode and in Pursue mode. When node speed is 500m/s the \(TCD_{TH}\) is configured as follows:  
\[\left\{ \begin{array}{ll}TCD_{TH}(RWP,RPGM(g=5))=1000\\ TCD_{TH}(RPGM(g=5),\ Pursue)=2000\end{array} \right. \tag{7}\]  
And the criteria are:  
\[mobility\ model=\left\{ \begin{array}{ll}RPGM(g=5)&if\ TCD_{ntwrk}<TCD_{TH}(RPGM (g=5),Pursue)\\ Pursue&if\ TCD_{ntwrk}>TCD_{TH}(RPGM(g=5),Pursue)\end{array} \right. \tag{8}\]  
The calculation method for the threshold value will be introduced in Section 4.3. According to the conclusion of [5], this experiment uses the following routing protocol selection scheme: the AOPV protocol is used in the RWP scenario, the AODV protocol is used in the RPGM scenario, and the DSDV protocol is used in the Pursue scenario. The TCD perception result at time \(t\) is represented by \(TCD(t)\). The perceptual moment, the actual movement model, the topological change perception result \(TCD(t)\), the judged mobility model, and the selected routing protocol are listed in Table 3.  
The perceptual results show that among the 26 perceptual moments, the perceived result \(TCD(t)\) is less than the threshold value and the determined mobility model does not match the actual model only for the speed of 50 m/s at 450 s and the speed of 500 m/s at 250 s, 300 s and 350 s. The rest of the perceived results and judgment results are correct. The rest of the perception results are correct, within the threshold range, and the judgment results are consistent with the actual movement model. The perceived efficiency is 84.6%. The above results show that TCD is effective for network topology change perception, and that the granularity setting and the \(TCD_{TH}\) setting are very important for the judgment.