# Dynamic Multiple Junction Selection Based Routing Protocol for VANETs in City Environment
## 4 Simulation Setup and Result Analysis
### Simulation Results and Discussion
#### 4.3.1 Packet Delivery Ratio  
Figure 4 depicts that packet delivery ratio for all the considered protocols increases with increase in vehicular density. It can be observed from the figure that packet delivery ratio of DMJSR is higher as compared to GSR, E-GyTAR and TFOR. This is primarily because, in DMJSR, the routing path is established progressively based on multiple junctions ensuring that the junctions with higher vehicular traffic density are selected. Consequently, a packet will travel successively closer towards the destination along the city streets where there are adequate vehicular nodes to ensure high network connectivity. Whereas in case of GSR, the source vehicle computes series of junction statically before transmission of the packet without taking into account the vehicular traffic density. As a result, some data packets  
\begin{table}
\begin{tabular}{c c c c} \hline \hline \multicolumn{2}{c}{**Simulation/Scenario**} & \multicolumn{2}{c}{**MAC/Routing**} \\ \hline Simulation time & 250 min & MAC (Medium Access & 802.11 DCF (Distributed Control) protocol & Coordination Function) \\ \hline Map size & 3000 \(\times\) 2700 m\({}^{2}\) & Channel capacity & 54 Mbps \\ \hline Mobility model & VanetMobiSim & Transmission range & 266 m \\ \hline Number of intersections & 23 & Traffic model & 15 CBR connections \\ \hline Number of double lane roads & 36 & Packet sending rate & (1–10 packet(s)/second) \\ \hline Number of vehicles & 100–350 & Vehicle Speed & 35–60 Km/h \\ \hline Number of simulation runs & 10 & Packet size & 128 bytes \\ \hline \multirow{2}{*}{Weighting factors} & \(\alpha=0.5\), \(\beta=0.5\), & \multirow{2}{*}{Beacon Interval} & \multirow{2}{*}{1 s} \\  & H\({}_{1}=0.5\), H\({}_{2}=0.5\) & & \\ \end{tabular}
\end{table}
Table 2: Simulation setup.  
are unable to find their destination node because of lack of connectivity on some segments of city streets. However, the problem with E-GyTAR and TFOR is that they establish path based on one junction at a time. As a result, sometimes those junctions whose next streets contain no vehicular traffic are selected. Selection of such streets results in local optimum and as a result, packet delivery ratio decreases. The new dynamic multiple junction selection mechanism and one-hop position and direction based forwarding mechanism minimize the occurrence of such cases and this helps DMJSR to bring considerable improvement in terms of packet delivery ratio as compared to GSR, E-GyTAR and TFOR.  
Figure 5 shows a comparison of packet delivery ratio vs. packet sending rates. Increasing packet-sending rate to certain values for all protocols decreases packet delivery ratio. It brings congestion which compels the network to drop some packets. In GSR, certain nodes on the preselected paths instigate more packet transmission which results in more decrease in packet delivery ratio as compared to others routing protocols. The packet-sending rate does not spoil too much the performance of E-GyTAR, TFOR and DMJSR in terms of delivery ratio.