## 4 Simulation Results
### Comparison between MMMR and Other Routing Protocols  
In this section, we present the results of the evaluation of MMMR in two different scenarios: a low density scenario with 60 nodes and a medium density scenario with 120 nodes. A medium density scenario in this case is enough to evaluate the protocol routing proposed without causing medium saturation. Each one is analyzed using different routing protocols to see the benefits that MMMR offers. The well-known routing protocols, AODV [19] and GPSR [6], are evaluated as references. We show the results with AODV for comparison purposes, because this protocol is an important reference in mobile _ad hoc_ networks and is the basis for other reactive protocols designed for VANETs. We implemented another proposal, named I-GPSR [11], because it has some similarities with our proposal. Furthermore, we use our previous proposal, called GBSR-B [20], which includes a buffer to temporarily store packets instead of dropping them when there is no proper next hop. GBSR-B is also building-aware to avoid sending packets to nodes in transmission range that are behind a building. Finally, we simulate MMMR configured with a weight of 0.25 in each metric (see Equation (27)). First, we can see in Figure 4 the percentage of packet losses obtained using each one of the evaluated protocols. We can notice that MMMR obtains the best results in both scenarios. This is due to the optimal selection of the next forwarding node based on the four proposed metrics. Besides, GBSR-B achieves a good result, due to the use of the buffer as an alternative to the perimeter mode used in GPSR, which results in lower packet losses. We observe lower packet losses in the medium density scenario. This makes sense, since the presence of a higher number of neighbors allows for a better selection of the next forwarding node. Regarding AODV, it is known that AODV is not an efficient routing protocol for VANETs, because it establishes a full end-to-end path. This is not suitable for VANETs, due to the high mobility of the nodes. When the link is established, however, it can successfully send a high number of packets; see Figure 4a,b. Figure 4: The behavior of the protocols AODV, GPSR, I-GPSR, GBSR-B and MMMR in terms of the percentage of packet losses are presented in (**a**) a low density scenario (60 nodes) and (**b**) a medium density scenario (120 nodes) (CI 95%). Meanwhile, GPSR uses the perimeter mode (as a recovery path process) that is not very efficient and produces a considerable number of packet losses. Finally, we see that the highest number of packet losses is obtained by I-GPSR in both low and medium density scenarios. This behavior of I-GPSR is mainly due to how the selection of the next hop is designed. The forwarding operation of I-GPSR is based on distance, speed, moving direction and density, which are adequate metrics for VANETs. I-GPSR prefers those vehicles that approach the destination faster, which is good in VANETs. Nevertheless, since our urban scenario has a mobility model that includes stops (in crossroads), it may happen that sometimes, vehicles remain static (e.g., in a crossroads, due to a traffic light), affecting the calculation of its score. I-GPSR thinks that such a stopped node is not a good forwarder node. We tackled this issue in MMMR, so that our proposed metric of the trajectory analyses the movement of the vehicle from two consecutive time instants. Figure 5 shows the results of the average packet delay. The delay is calculated based on those packets that successfully arrived at the destination. Since GPSR takes the forwarding decision considering only distance, it frequently uses the perimeter mode (recovery process), which is not much more efficient and increases the probability of packet losses. GPSR obtains the lowest packet delay in both scenarios, as the second columns in Figure 4(a),b shown. This is because with GPSR, a low number of packets considered to compute the average delay, arrived at the destination.