# Energy-Saving Routing Protocols for Smart Cities
## 3 Results
### Simulation Results and Discussion  
As mentioned before, the simulation results refer to the average values obtained from five simulation trials. Figure 4 shows the PDR metric for DVR, AODV, DSR, and modified DSR (that is, DSR with the proposed RPA routing protocol). From these results, it can be seen that the reactive protocols present better overall performance in sending data; the AODV protocol has the highest rate of data packet delivery, followed by the DSR and modified DSR protocols. The result for AODV corresponds to a route verification mechanism that works periodically and during the movement of the source node, anticipating the discovery of new routes in case of unavailability. For speeds below 20 km/h, all protocols maintained high data delivery rates. However, above this speed value the performance decay of the DVR protocol was quite high, with more than 50% of transmitted packets being lost when the source node moved at speeds greater than 60 km/h. The other protocols were able to maintain delivery rates above 80%  
Figure 3: Power adjustment safety margin versus energy savings. for the same speed range. Consequently, the impact of the source node speed variation on the proactive DVR protocol was much greater. This characteristic was expected, as new routes could be discovered only within the fixed routing interval of 5 min. In Figure 5, the performance results of the routing protocols in relation to the average end-to-end delay are shown. From these results, it can be observed that the DVR protocol had the lowest latency, followed by the AODV protocol. The DSR and modified DSR protocols had higher average latency compared to the others. Figure 4: Packet delivery rate (PDR) as a function of the source node’s speed for the DVR, AODV, DSR, and Modified DSR protocols. Figure 5: End-to-end delay (E2 ED) as a function of the source node’s speed for the DVR, AODV, DSR, and Modified DSR protocols. It is important to mention that the performance of the DVR protocol in terms of latency shows expected behavior. As a proactive protocol, it is independent of unavailable routes, as the discovery of new paths to destinations takes place during fixed routing periods and is accessible in the routing tables prior to each transmission demand. The average performance of the protocols according to the jitter metric is shown in Figure 6. Based on the curves in Figure 6, it can be seen that the DSR protocol was the only one that does not have a variation for latency higher than 4 ms. For speeds below 100 km/h, the DVR protocol presented similar behavior. However, at higher speeds, it is the protocol with the highest jitter. Regarding the throughput performance, shown in Figure 7, a high correlation was observed with the packet delivery rate. The performance of the AODV protocol in terms of the packet delivery rate is reflected in the transfer rate metric, indicating that this protocol is capable of transmitting more data per unit of time than the others. Both the DSR protocol and the modified DSR had slightly lower performance than AODV. As the DVR protocol obtains data regarding routes at a fixed interval of 5 min, this protocol has a higher packet loss rate when subjected to high speeds, causing a considerable reduction in its transfer rate, as can be seen in Figure 7.  
Figure 8 shows the results of the average total battery charge consumption according to the routing protocol. From these results, the impact of the large number of re-transmissions on the total consumption of the DVR protocol can be observed, leading it to consume around 460 J for the whole simulation. Although the AODV protocol presents the best performance in the delivery of data packets, it consumed the second-highest energy, at almost 300 J, while the modified DSR protocol (DSR with RPA routing protocol) consumed the least energy over the total simulation time.