## 5 Performance Evaluation
### Results and Discussion  
The proposed and comparison mechanisms are evaluated based on position falsification attacks discussed in the above section, and the accuracy of each anomaly detection mechanism is compared.  
The metrics used to evaluate the detection algorithm are described in the following nomenclature.  
* **True positive (TP):** The BSM that contains fake or manipulated information regarding the respective vehicle and is correctly identified as an anomaly.
* **True negative (TN):** The BSM that contains legitimate information regarding the respective vehicle and is classified as genuine information.
* **False positive (FP):** The BSM that contains legitimate information regarding the respective vehicle and is incorrectly classified as an anomaly.
* **False negative (FN):** The BSM that contains fake or manipulated information regarding the respective vehicle and is incorrectly identified as genuine information.  
The accuracy rate (ACR) is calculated based on the above-given variables as follows:  
\[\text{ACR}=\frac{\text{TP}+\text{TN}}{\text{TP}+\text{TN}+\text{FP}+\text{ FN}} \tag{8}\]  
Table 3 shows a brief overview of the dataset used for anomaly detection. The parameters **loc_1x**, **loc_1y**, **loc_2x**, **loc_2y**, **loc_3x**, and **loc_3y** are the location coordinates of three consecutive BSMs of each vehicle, whereas **speed_1**, **speed_2**, and **speed_3** are the values of speed in m/sec for the concerned BSMs. The **dir_1**, **dir_2**, and **dir_3** represent the direction of the vehicle in radians for the consecutive BSMs. The **flag** parameters show the status of vehicles, where 0 represents a legitimate vehicle and 1 represents a malicious vehicle.  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Parameters** & **Values** \\ \hline Simulation area & 3 km \(\times\) 3 km \\ Simulation time & 500 s \\ Simulation runs & 40 \\ Transmission range & 250 m \\ Transmission power & 20 mW \\ Road type & Two-way traffic \\ Data transmission rate & 6 Mbps \\ MAC protocol & IEEE 802.11p WAVE \\ Vehicle density & 30–125/km \\ Vehicle velocity & 12–20 m/s \\ Maximum acceleration & 2.6 m/s\({}^{2}\) \\ Distribution model & Nakagami \\ EM packet size & 170 bytes \\ Beacon packet size & 194 bytes \\ Road side units & Yes \\ \hline \hline \end{tabular}
\end{table}
Table 2: Simulation Parameters.  
\begin{table}
\begin{tabular}{c c c c c c c c c c c c c} \hline \hline
**Veh** & **loc\_1x** & **loc\_1y** & **speed\_1** & **dir\_1** & **loc\_2x** & **loc\_2y** & **speed\_2** & **dir\_2** & **loc\_3x** & **loc\_3y** & **speed\_3** & **dir\_3** & **Flag** \\ \hline
1 & 1253.61 & 2271.19 & 12.12 & 1.5707 & 1254.83 & 2273.54 & 12.14 & 1.5713 & 1255.11 & 2275.11 & 12.13 & 1.5710 & 0 \\
2 & 3719.27 & 6241.43 & 14.07 & 0.7142 & 3721.01 & 6243.50 & 14.08 & 0.7148 & 3723.89 & 6244.77 & 14.08 & 0.7146 & 0 \\
3 & 2593.32 & 3374.28 & 15.10 & 2.7981 & 2815.32 & 3624.28 & 15.11 & 2.7990 & 2947.27 & 3871.82 & 15.11 & 2.7985 & 1 \\
4 & 1129.07 & 2316.19 & 13.76 & 2.4639 & 1130.87 & 2317.38 & 13.77 & 2.4677 & 1132.02 & 2318.05 & 13.77 & 2.4613 & 0 \\ \hline \hline \end{tabular}
\end{table}
Table 3: Brief overview of the dataset used for anomaly detection.