## 5 Results from Experiments Using the Platform
### Setup and Methodology  
All experiments addressed the same scenario, according to which mobile nodes relayed messages exchanged between a pair of static source and destination nodes. The mobile nodes moved within a square area of size 14 \(\times\) 14 m, and the source and destination nodes were placed at diagonally opposite vertices of the square. Four mobile nodes were employed, all of which moved according to the Random Direction mobility model [55] with zero pause time and a constant speed of magnitude \(V=0.54\) m/s (approx. 2 km/h). The experimentation activities took place in an outdoor area within the campus of the Agricultural University of Athens, Greece. Figure 10(a) provides relevant coordinates (based on the Google Maps information), while Figure 10(b) captures a snapshot of activity on the terrain. Given the moderate size of the experimentation terrain, if the full range of wireless communications had been enabled, it would have been impossible to explore the impact of the network density on the performance, as all MANET nodes would have been in range of one another, and every node would have perceived all others as (topological) neighbors. Even worse, the destination node would have been directly reachable from the source node, negating the need for any intermediate message relays. To mitigate such effects, the experiments leveraged the platform's capability of controlling through software the communication range of the MANET nodes (see Section 3.1.2). Using this mechanism, different experiments were conducted, setting the communication range \(r\) of the MANET nodes to 3, 5, 6, and 7 m in turn. Higher values of the range yield greater network densities. Indeed, the regularity of the Random Direction mobility model implies that, at steady-state, a mobile node may occupy any point in the mobility terrain equally likely. Thus, given a mobility terrain of overall area \(A\), a mobile node with communication range \(r\) has each of the other \(N-1\) mobile nodes in range with probability \(\pi r^{2}/A\), so the node has on average \((N-1)\pi r^{2}/A\) neighbors. In the experiment scenarios, \(A=14^{2}\) m\({}^{2}\) and \(N=4\), so the four aforementioned range values correspond toan average number of 0.43, 1.20, 1.73, and 2.36 neighbors per node, respectively, spanning a range from low to higher network densities. Experiments addressing all four network densities were repeated three times, each time employing a different configuration of the platform. In the first configuration, the motion of the mobile nodes was emulatedby interfacing the localization module of the nodes with software simulating mobility, as explained in Section 3.1.1. Both of the other two configurations involved actual mobility (realized by attaching the hardware for the mobile nodes to mobile robots with characteristics as in Section 4.2), differing in the type of the GPS devices used for localization. Specifically, the MANET nodes in the second configuration were equipped with NEO-M8N GPS receivers, while the third configuration employed the lessprecise VK-162 USB devices instead (see Section 3.2.3). By comparing results across all three configurations, it became possible to explore the impact of varying degrees of localization accuracy on the performance of the routing protocols. For all protocols, network densities, and platform configurations, the performance was quantified through the average delay for message delivery from source to destination and the average number of hops required for this delivery. The platform provides facilities for calculating both of these metrics, as discussed in Section 3.1.4. The values reported here were obtained by averaging samples over 20 message deliveries using each routing protocol. In order to avoid correlations in the sampling process, the time between message generation events was chosen to be sufficiently large to ensure that the arrangement of MANET nodes on the terrain, as \"seen\" by any two consecutively generated messages, were completely different.