# Building Realistic Mobility Models for Mobile Ad Hoc Networks
## 6 Real Shipping Movement Model
### Results and Discussion
#### 6.8.4 Normalized Routing Load on Random Waypoint Shipping Model  
As previously discussed, only AODV and DSR are considered in this section because of DSDV implementation-related issues in ns-2. The results of the NRL graphs for the RWP model with mobile sinks are shown in Figure 16, while fixed sinks are depicted in Figure 17. Network routing loads for the RWP model are considerably larger than for the realistic model. In the model where the base stations are also moving (Figure 16), the NRLs are up to two orders of magnitude higher, while they are up to three orders of magnitude greater for fixed base stations (Figure 17). Random placement and movement of the nodes means that no shipping lane is strictly followed; therefore, the nodes are not constrained in any way. With relatively few nodes spread over such a large area, the protocols have to work much harder to establish any routes. With random movement of the nodes, these routes are likely to be less durable than those formed within the shipping lanes on the realistic model. In tests where the radio range is high enough to establish a reasonable data delivery, the routing overheads are generally two orders of magnitude higher in the random model. The random placement of the nodes undeniably implies that there will be occasions when they will be placed in original positions and thus, have movements that are advantageous compared with the normal random positions and movements. Such cases will produce lower NRLs than expected. In the test runs, the NRL results reveal that they are at least ten times greater than those in the realistic model. For base stations, which act as destination nodes and are randomly distributed, as well as moving, the NRL for both protocols is governed by radio range. A longer radio range affords a higher chance of reaching neighboring nodes and hence, less likelihood of network partitioning. It will also result in a reduced hop count because more nodes and, in particular, nodes that are further away will be in range at any point. This behaviour is entirely aligned with typical expectations. Concerning PDR, the moving base stations behave similarly to each other, and hence, the NRL results reveal no significant difference among the  
Figure 15: Realistic Shipping Model with Normalized Routing Load. sink nodes. It would make no difference which nodes are chosen as sinks in this particular setup. Given the random placement of all nodes, including the sinks, it is possible that a sink may be placed or may move to an edge or corner of the operating area, placing it further from many nodes, reducing its reachability and increasing the required hop count in order for it to be reachable. It is equally possible that a particular sink node will be placed or will move to the centre of the operating area, yielding a much better chance of connectivity, reduced hop counts, and many more possible routes by which it can be reached. This would show up as a reduced NRL, as well as an increased PDR. Figure 16: Moving Base Station Random Waypoint Shipping Model with Normalized Routing Load. For the RWP model where base stations are fixed at their real geographical locations (rather than being randomly distributed and moving), the results show that across all the target base stations, routing loads decrease with an increase in radio range, with the exception of DSR on a 10-km radio range. This decrease is mirrored by an improved packet delivery ratio, indicating that the protocols are able to establish the required routes more easily. Again, this is what would be expected. As with the packet delivery ratio, having fixed base stations results in improved routing load performance when the radio range is shorter, but worse performance when the radio range is higher.