## 4 Simulation and Performance Analysis
### Simulation Metrics  
The performance of EGR and the related exiting routing approaches are compared using the following routing metrics.  
* _End-to-End delay_: End-to-end delay is the amount of time for moving a packet from the source to the destination across a network. It is the sum of the delays experienced during transmission, propagation, and processing via each link from the source to the destination. Equation (14) represents the statistical formula that can be used to determine end-to-end delay (\(t_{ee}\)) in terms of milliseconds and is given by  
\begin{table}
\begin{tabular}{l l l l} \hline \hline
**Parameters** & **Values** & **Parameters** & **Values** \\ \hline Total time & 500 s & Iqlen & 50 packets \\ Simulation area & 2000 \(\times\) 2000 m\({}^{2}\) & Channel type & Wireless \\ Vehicle speed & 10–60 Km/h & Antenna model & Omni directional \\ Number of vehicles & 500 vehicles & Propagation model & Shadowing \\ Source vehicles & 20 & MAC data rate & 5 Mbps \\ Transmission range & 300 m & MAC protocol & IEEE 802.11p \\ Junction & 8 & CBR rate & 6 Packets/s \\ Hello timeout & 0.5 s & Packet type & UDP \\ Query period & 2.5 s & Packet size & 512 bytes \\ Traffic type & CBR & Geocast region size & 500 \(\times\) 500 m\({}^{2}\) \\ \hline \hline \end{tabular}
\end{table}
Table 1: Simulation Parameters.  
\[t_{ee}(\text{ms})\ =\ \frac{\sum_{i=1}^{10}\sum_{j=1}^{n_{PB}}(t_{ST}^{ij}-t_{RT}^{ij})}{n _{PR}\times 10} \tag{14}\]  
where \(n_{PR}\) represents the number of packets delivered at the destination, \(t_{ST}^{ij}\) denotes the simulation time in the \(i\)th round during which the \(j\)th packet is sent, and \(t_{RT}^{ij}\) denotes the simulation time in the \(i\)th round during which the \(j\)th packet is delivered at the destination.  
* _Throughput_: The throughput is the quantity of packets effectively sent to the destination in a unit simulation time. Bits per second are used to measure it. The limited number of forwarding possibilities available on the highway is due to the fact that there are alternative forms of transportation accessible, and intercity traffic is not extremely heavy. Equation (15), a statistical expression representing throughput (\(\tau\)), is given by  
\[\tau\ (\text{kbps})=\frac{\sum_{i=1}^{10}(n_{PR}\times n_{b})}{10} \tag{15}\]  
where \(n_{b}\) represents the number of bits per packets.  
* _One-hop Link Disconnection_: One-hop link disconnection is the number of unsuccessful attempts at packet transmission. The reliability of a link is demonstrated by this measure. It affirms the effectiveness of the forwarding vehicle selection process. Equation (16) represents the arithmetical formula that used to quantify one-hop link disconnection (\(l_{d}\)). \[l_{d}(\%)=\left\{\frac{\left(\sum_{i=1}^{10}\frac{n_{BD}}{n_{PS}}\right)}{10 }\right\}\times 100\] (16) where \(n_{BD}\) denotes the number of unsuccessful attempts to deliver a message from a sending vehicle to destination vehicles in the \(i\)th simulation run and \(n_{PS}\) denotes the number of packets delivered to the destination in the \(i\)th simulation run.  
As presented in the four cases in Section 3.4, a single best forwarder recipient vehicle is selected considering the current traffic scenario, which might fall into any of the four case studies. We do agree that duplicate messages have been received by some recipient vehicles due to communication reestablishment. However, the duplicate messages are easily discardable considering the packet information, such as sequence number, hop count, and time-to-live timestamp.