# Optimal Path Routing Protocol for Warning Messages Dissemination for Highway VANET
## 3 Proposed Protocol
### System Model  
Figure 2 depicts a detailed outline of the proposed protocol, which achieves direction-based priority assignments among numerous routes to a destination. Collisions among nodes on a wide scale could be caused by an ineffective routing strategy for vehicle collision prevention. As a result, routing performance becomes equally essential in addition to the importance of node collision detection. Delivering timely and reliable WMs is crucial for implementing collision-prevention procedures. Once a source node is willing to send a WM, and there is only one path to the destination, following that path becomes unavoidable. When there are numerous paths to the target, choosing the optimum path with the least latency, the fewest packet losses, and the highest throughput becomes critical. Greedy protocols use distance as a parameter to find the optimum path, whereas direction-based Greedy protocols look for available relay nodes in the direction of the destination node. All paths to the target are examined for a specified time step, such as \(\tau 0\). However, the \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Technique**} & \multirow{2}{*}{**Year**} & **Consider** & **Network** & **WM Dissemination** & **Clustering-Based** & **PDR** & **Delay** \\  & & **Bi-Directional Traffic** & **Scenario** & **Mechanism** & **Clustering-Based** & **PDR** & **Delay** \\ \hline DVCAST [15] & 2010 & \(\times\) & Highway & Broadcast, SCF & / & Medium & High \\ [PERSON] et al. [16] & 2011 & \(\times\) & Highway & Broadcast, SCF & / & High & Medium \\ [PERSON] et al. [7] & 2014 & \(\times\) & Highway & Broadcast, SCF & / & Medium & Medium \\ [PERSON] et al. [18] & 2017 & \(\times\) & Highway & SCF & / & Medium & Medium \\ [PERSON] et al. [9] & 2018 & \(\times\) & Urban & Fog server-based & / & Medium & Medium \\ DABPS [8] & 2019 & \(\checkmark\) & Highway & Direction-based & / & High & Low \\ [PERSON] et al. [19] & 2019 & \(\times\) & Highway & Broadcast & / & Medium & Medium \\ TBEMD [14] & 2019 & \(\times\) & Urban & Broadcast & / & Medium & Medium \\ RBO-Call [32] & 2020 & \(\times\) & Highway & Broadcast, uni-cast & / & High & Medium \\ P-DACCA [22] & 2020 & \(\checkmark\) & Highway & Broadcast & / & Medium & Low \\ EEMDS [31] & 2021 & \(\times\) & Urban & Broadcast, uni-cast & / & High & Low \\ BURP [33] & 2022 & \(\checkmark\) & Urban & Broadcast & / & High & Low \\ OPRP & \(\checkmark\) & Highway & Direction-based & / & High & Low \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Comparison of VANET WM dissemination techniques. node's mobility is very high; they regularly enter and exit each other's communication ranges, resulting in continual topological changes in bi-direction circumstances. Due to this dynamic nature, two scenarios may arise during message delivery. Firstly, paths to the target may encounter outages, causing all communications transmitted on these paths to be lost. Second, because the path specified at \(\tau_{0}\) does not always stay intact, it may go through a path reconstruction phase at \(\tau_{1}\), \(\tau_{2}\),..., \(\tau_{n}\) until a message is successfully delivered. This might be increasing or decreasing the length of a path. As a result, the rate of packet drops and delays increase, reducing the throughput of the Greedy and direction-based Greedy protocols. Therefore, in complement to a distance parameter, we recommend using the following parameters for the optimum path selection:  
* The direction of node movement: here, we apply Equation (1) to find the direction of a node's movement. * The source and destination nodes' relative positions. * The list of notations used in this research can also be found in Table 2. In this regard, the proposed protocol includes two phases: the cluster formation phase and the optimal path discovery phase. The subsections below go over all of these phases in detail.