## 3 An Opportunistic Routing for Data Forwarding Based on Vehicle Mobility Association
### The Algorithm Design of OVMA
In the simulation, \(\mu\) and \(\tau\) are set to be greater than 0.5 in order to ensure the association between nodes and information forwarding probability, which can significantly improve the performance of experimental results. This simulation uses MATLAB as the simulation environment and the Manhattan Mobility Model for the vehicle's movement. For the Manhattan Mobility Model [31], the probability of forwarding movement is set to 0.5, and the probability of turning left or right is set to 0.25, respectively. It is remarkable that in IEEE 802.11P standards, the communication range of vehicles is confirmed according to the required data rate in the VANETs. Table 2 summarizes the relevant parameters used for the simulation experiment of the proposed OVMA opportunistic routing protocol. Figure 4 describes the impact of changing the \(\alpha\) and \(\beta\) values of the network lifetime. This simulation assumed that the network dies when half of the nodes within the network are depleted of energy. It can be observed that when the node heuristic factor \(\alpha\) is increased, the energy consumption is considered more when selecting forwarding nodes, so the network lifetime can be extended. When the value of \(\alpha\) is near 0.88, the network has the longest lifetime. When the \(\alpha\) value is 0.88, OVMA ensures the connectivity and coverage on the network and balances the energy consumption of nodes, reducing the data traffic, saving the energy of the nodes, and prolonging the network lifetime. However, when the expected heuristic factor \(\beta\) takes up a small proportion of calculated transmission rate, there is a degradation of the perceived performance of data forwarding, resulting in the existence of data across the network for a longer period of time, increasing the energy consumption of nodes and thus affecting the network lifetime. The simulation results in Figure 5 depict the impact of changing the settings of \(\alpha\) and \(\beta\) on the data forwarding success ratio following consideration of the energy, delay, and routing overhead. When the \(\alpha\) value is about 0.74, the network has the highest data forwarding success ratio. When the \(\alpha\) value is 0.74, the greater the information heuristic performance, the better the perception between vehicles (which makes the association between vehicles increase), the data cannot pass too many redundant nodes during forwarding, and the network has the highest data forwarding success ratio. \begin{table}
\begin{tabular}{c c} \hline \hline
**Parameters** & **Value** \\ \hline Mobility model & Manhattan Mobility Model \\ MAC and PHY Layers & IEEE 802.11P \\ Simulation time (s) & 1000 \\ Number of vehicles & 50, 150, 250, 350, 450 \\ Vehicle velocity (km/h) & 40–80 \\ Transmission range (m) & 300 \\ CBR (data per second) & 20–180 \\ EM size (bits) & 320 \\ HM size (bits) & 30 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Simulation Parameters. Figure 4: Network lifetimes vs. value of \(\alpha\). Figure 6 illustrates the impact of changes in \(\alpha\) and \(\beta\) on network routing overhead. The setting of replica information life (Ert) is to eliminate the impact of expired routes. It can be seen that with the change of \(\alpha\) value, the routing overhead varies slowly when the \(\alpha\) value is less than 0.78. The OVMA protocol can effectively reduce route establishing time, route recovery time, and route overload, and the packet delivery ratio remains high. Figure 7 shows the impact of changing the setting of \(\alpha\) and \(\beta\) on data forwarding delay. Often, the paths can be congested and there may be accidents, natural disasters, or business disputes that can cause transmission delays. Responding to requests by a vehicle with a larger association improves responsiveness by reducing network hops and network latency. When the value of \(\beta\) is greater than 0.22, the data forwarding delay varies steadily. Figure 5: Data forwarding ratio vs. value of \(\alpha\). Figure 6: Routing overhead vs. value of \(\alpha\).