# An Effective and Efficient Adaptive Probability Data Dissemination Protocol in VANET
## 4 Performance Assessment
### Impact of Vehicle Density in Reliability of Data Dissemination  
In this section, the effects of vehicle density with protocol performance metrics were evaluated when configuring the EEAPD protocol in a real-time network environment that can be adopted for data safety applications. As depicted from Figure 13, when the number of vehicles becomes higher the forwarding ratios devalue in both protocols. The result shows that EEAPD forwarding ratio degrades better than other protocols on forwarding vehicle selection or reducing unnecessary broadcast within the transmission range (area of interest). As expected, in the EEAPD protocol the number of forwarder vehicles decreased around 65% in dense network compared to AddP, reduced by 45%, SEAD reduced by 50%, delay-based reduced by 40%, and S1 PD reduced by 25% which is performed poor compare to all protocols because of receiving a large amount of redundant messages (refer to Figure 2). The better selection of relaying vehicles the more the probability of broadcast performance is better in EEAPD. As portrayed in Figure 14 both S1 PD, SEAD, AddP, and delay-based obtained an approximately equal amount of packet delivery ratio at increasing vehicle density from 50 to 100 while the packet delivery ratio of EEAPD is approximately 1 (100%), (refer to Table 4). This show that EEAPD outperforms all protocols by delivering the messages while optimizing the network bandwidth. One requirement for a better data dissemination protocol is to archive the packet delivery ratio close to 100%. But increasing the forwarder nodes may lead to overload link bandwidth, hence network contention and collision may occur as in Figure 15 which illustrates the amount of packet data carried per time (\"link-load\" (bits/s)) by EEAPD and those carried by other protocol. Here EEAPD protocol performs better than SEAD, S1 PD, AddP and delay-based protocols for all vehicles' density. EEAPDhas lower the link load to 60% compare to other protocols (delay-based = 68%, AddP = 74%, SEAD = 80% and S1 PD is more than 100%) at 100 Veh/km. This demonstrates that EEAPD protocol able to adapt particularly in a high-density network with respect to redundant transmission obtained. Figure 2 presents the redundancy ratio doesn't exceed 3 at vehicles' density is 63 vehicles/km when increasing in vehicles' density. This happens via efficient and effective use of bandwidth that enables different applications to be performed simultaneously by increase network capacity. Figure 14: Packet Delivery Ratio Vs Vehicles’ Density. Figure 13: Forwarding ratio vs vehicle density. Furthermore, as depicted in Figure 16, EEAPD shows a better result by archiving a better packet drop ratio of about 27% compared with other protocols (AddP = 34%, Delay-Based = 36, SEAD = 38 and S1 PD = 55%); this observation shows that how EEAPD protocol handles broadcast storm problem in VANET by reducing message collision, message redundancy, erroneous messages and network contention when comparing with SEAD, AddP, S1 PD, and Delay-based protocols while archiving low end-to-end delay as portrayed in Figure 17.  
Figure 18 show the percentage of relaying vehicles with different vehicles densities. When the vehicle density decreases, the percentage of relaying vehicle increase in a dense network. EEAPD archive 80% better-relaying vehicles at vehicle density are 10 and perform poorly when vehicle density increase to 100 compare to SEAD, S1 PD, AddP, and Delay-Based protocols. This shows that not only when the vehicle density is small it helps to reduce the broadcast storm problem but also increases the forwarding ratio (refer to Figure 13).