## 5 Results from Experiments Using the Platform
### Results  
The results from the experiments appear in Figures 12-14. All the main trends exhibited therein are in accordance with intuition, as we now discuss. In particular, for all considered routing protocols and platform configurations, the average end-to-end delay decreases as the network density increases. This happens because in denser topologies, a message-carrying node is in contact with more neighbors and thus experiences an increased number of potential message-forwarding opportunities per unit of time, with beneficial impacts on the delay-related performance. The effect and relative importance of the forward and carry actions are also visible in the results. By comparing the end-to-end delays for MFR and MoVe, it is seen that in all configurations, the carry-based MoVe protocol outperforms the forward-based MFR when the network density is low, while the opposite is true for high densities. Again, this phenomenon is intuitively appealing: When the network density is low, a message-carrying node makes contact with just a few neighbors, on average, so the node rarely encounters suitable forwarding opportunities. Thus, in such environments, the carry action is more effective. On the other hand, in dense topologies, there are more neighbors, and it is easier for the node to identify suitable next hops, the forward action prevails, and the MFR protocol performs better. In networks of intermediate densities, both the forward and carry actions have a significant effect, and both should be taken into account for an effective routing. The MAD protocol is inherently capable of exploiting the right combination of the forward and carry actions, behaving more like MoVe in low densities and more like MFR in higher ones. As it can be seen from the delay-related results, both versions of the protocol adjust their operation properly across the entire range of network densities and for all configurations, thus being more flexible and better performing overall than the protocols relying on a single action. Further, the results indicate that the improved version of MAD outperforms the original version of the protocol throughoutbecause the more accurate estimation of  
Figure 11: (**a**) Coordinates of the experimentation terrain; (**b**) snapshot of activity in the terrain. the retaining time in the improved version enables a better adjustment of the forward and carry components in the protocol's next-hop selection metric. With respect to the number of hops required for message delivery, the results demonstrate that, in all configurations, MoVe uses a smaller number of hops than MFR. Again, this is expectedbecause MoVe determines the suitability of next-hop nodes solely on the basis of the direction of motion. Thus, once a node heading towards the destination receives the message, it will be unlikely to encounter neighbors better directed than itself, and the same node will keep carrying the message until delivery. On the contrary, MFR bases its operation on the forward action, which inherently involves a greater number of hops. It is noted that a smaller number of hops is not necessarily accompanied by better delay-related performance: The results clearly show that in dense environments (where the forward action is most impactful), the fewer hops of MoVe prevent this protocol from attaining the better end-to-end delay exhibited by MFR and the two versions of MAD. The aforementioned patterns in the results are not only reasonable, as discussed, but also well aligned with analogous patterns in other results, such as the simulation-based results in [47]. This is remarkable, considering that the simulation results addressed idealized settings (perfect communication channels, perfect knowledge of location and  
Figure 14: Configuration 3 (real mobility, GPS type VK-162): (a) average end-to-end delay and (b) average number of hops vs. network density (\(V=0.54\) m/s). Figure 12: Configuration 1 (emulated mobility): (a) average end-to-end delay and (b) average number of hops vs. network density (\(V=0.54\) m/s).