## 5 Performance Study
### Simulation Results
#### 5.3.2 Simulation Results using a Realistic Scenario  
In this subsection, we analyze the effects of node mobility, network load, and the number of data flows on the selected performance metrics: the average throughput and end-to-end delay. We also analyze the effect of transmission ranges and the parameter \(\xi\) on the performance of routing protocols. Figure 6: End-to-end PDR gain by using a robotic relay. _(1) Node mobility_  
First, we analyze the effect of node mobility on the network performance. The movements of the group and each node inside the group is simulated according random waypoint model with the same pause time of 30 s. The group speed is randomly chosen in (\(v_{min}\),\(v_{max}\)). The value of \(v_{min}\) is set to 0 m/s (meter/seconds), and the value of \(v_{max}\) varies from 10 to 20, 30, 40 m/s. The relative speed of nodes inside a group is randomly chosen in [0, 20] m/s. Also, RNs are assumed to have the constant speed of 20 m/s. Three data flows from source nodes to the sink are used for the network traffic; the load of each data flow is set to 900 Kbps. As shown in Figure 7, RoCoMAR shows a higher throughput than AODV, OLSR, DSR and GFR. For example, when the maximum speed of the group is 20 m/s, RoCoMAR's throughput is higher than 600 Kbps, while other protocols show less than 400 Kbps. Also, over the variation of the maximum group speed, RoCoMAR consistently shows a higher throughput than other protocols. It is because RoCoMAR not only effectively reinforces the low quality links but also prevents wireless link breakage that causes a high loss rate of data packets and frequent route discovery processes. Also note that RoCoMAR enables RNs to keep the network connectivity between nodes in a group and the sink even when the group of nodes moves far away from the sink. RoCoMAR's throughput improvement tends to decrease as the maximum group speed grows higher than 30 m/s as shown in Figure 7. One reason of this is that the limited speed of RNs. The RN with the speed of 20 m/s could not follow the mobile regular nodes if they are moving with the speed higher than the speed of RN. As also shown in Figure 7, in most cases, DSR shows the lowest throughput due to its stale route cache in high speed node mobility. Figure 8 shows the average end-to-end delay of routing protocols over variation of speed of the group. As shown in Figure 8, RoCoMAR has a lower delay than DSR, GFR, and OLSR, but a slightly higher delay than AODV. Note that the end-to-end delay of RoCoMAR is consistently shorter than 0.05 seconds, which is acceptable for most user applications (even for voice and video transmissions). Recall that RoCoMAR uses the same route discovery mechanism with AODV. Since relays can be added to the  
Figure 7: Effects of node mobility on average throughput. route, RoCoMAR can have a longer route in terms of the number of hops than AODV. This can result in a slightly high end-to-end delay compared with AODV. GFR shows the highest average end-to-end delay compared with others, as shown in Figure 8. This is because neighboring nodes' position information can be stale, especially when nodes are moving at a high speed. The delay of DSR also highly depends on the group speed, as it needs to initiate a new time-consuming route discovery process when route cache becomes stale due to high node mobility. _(2) Network load_  
In order to be effective for a practical deployment, a network should be scalable in terms of network loads. To analyze the effect of the network load on the performance, RoCoMAR is compared with other protocols under various network loads. There are three data flows in the network, and each source transmits data at the rate from 300 Kbps to 1200 Kbps, which results in the total network load from 900 Kbps to 3.6 Mbps. The maximum speed of group and member movements are set to 20 m/s. As we can see in Figure 9, RoCoMAR achieves the highest throughput compared with others over various network loads.