# DMRVR: Dynamic Milk-Run Vehicle Routing Solution Using Fog-Based Vehicular Ad Hoc Networks
## 4 Evaluation of the DMRVR Solution
### Impacts on the Vehicular Network  
Three metrics were adopted to evaluate the DMRVR impacts on the vehicular network:  
* **Success rate**: represented by the frequency the messages arrive at the destinations. Such metric checks whether the vehicular network has been able to supply the required communication, thus evaluating if the system is able to perform the pickup operation. For this metric, _NotifyPickup_ messages were considered;
* **Average end-to-end delay**: which measures the expected time a message takes to get to the destination node from the origin. Such a delay represents the difference between the moment the message has been received, less the time it has been effectively sent. _NotifyPickup_ messages were part of this metric;
* **Maximum transmission distance**: it refers to the longest distance covered by the broadcasted messages up to the destination node.  
Figure 8 shows the message delivery success rate for the _NotifyPickup_ messages considering the four vehicle densities, given different quantities of RSUs. With nine RSUs, from which eight are suppliers, and 1 is located within the logistics operator premises, the message delivery success rate raised from 45.83% (sparse scenario) to 83.33% (dense scenario). In areas with low vehicle network coverage, two more RSUs have been inserted, and the delivery success rate enlarged from 62.5% to 91.33%. Such feature has shown that the vehicle density influences positively the success rate, due to the more advantageous utilization of the multi-hop effect. On the other hand, when one adds RSUs in the communication area, the success rate raises, especially in sparse scenarios.  
Although DMRVR did not send any critical messages, it was observed that low message delivery rate may generate communication failures between the logistics operator and the collecting vehicles, leading to management problems and milk-run efficiency reduction. Accordingly, one concludes that the number of RSUs in addition to vehicle densities along the route, must be considered when planning milk-run operations of this kind.  
It is important to note that the message delivery success rate may be also influenced by a faulty selection of a relay node. When a GBC packet is received, the node checks out which neighbor is closest to the destination area, and takes it as a forwarder, or relay node.  
A wrong node selection can be made when the selected node is no longer available in range because it has moved away in the meantime. In our simulations, this situation occurred in some cases, affecting the success rate. According to [50], the neighbor's table showing the nodes is only updated whenever a beacon packet has been received. Such a table presents a 20 s timeout. Thus, the dissemination protocol will remove a node (outside coverage area) only after 20 s.  
To improve the success rate, one has to use acknowledgment messages (ACK) in all messages DMRVR, and not only in _NotifyWithdrawal_ communication. We were not able to evaluate this form of use in all messages due to the fact that the simulations showed too long times. We intend to analyze the advantages and disadvantages of employing acknowledgment ACK messages in a future work.  
The vehicular network impacts detected with the model are summarized in Table 9. With nine RSUs, the end-to-end delay time has shown to be lower than one second for all vehicle densities. However, with 11 RSUs, the time increased to the range from 8.35 up to 22.14 s, depending on different densities. The maximum transmission distance slightly increased as a function of vehicle density: it increased from 9385 m to 9777 m with nine RSUs, and in the range from 9719 up to 9725 with 11 RSUs. This behavior difference occurred because the nine RSUs were positioned at the edge of the LuST map, whereas the other two RSUs were set at the city central part. The findings were as expected and are suitable for the study case's features.