## 8 Performance Evaluation
### End to End Delay and Packet Success Ratio  
Figure 16 and 17 describe the end-to-end delay and the packet success ratio of the packets from MNs to the GW when the speed of MNs and the number of hops between them varies. After a certain number of hops, the end-to-end delay increases linearly with the increasing number of hops between the MN and the GW. Also the end-to-end delay increases when the speed of the MN increases. This is because as the speed of the MN increases, the association of the MN with its SN breaks, triggering off the handoff process. Thus when the MN moves with high speed, most of the time is spent to complete the handoff process by the new SN and the old SN. Some spikes in the graph can also be observed for some early hops. There are several factors which cause these spikes. These include: i) the mobility model (the random way point) - because the MN abruptly changes its position according to the mobility model used [28], ii) the speed of MN - that causes handoff and some nodes might not have routing information, iii) The pause time between movements, and [29] iv) AODV - AODV broadcasts packets bring traffic in the network that not only cause collision but also introduce hidden node problem [28]. The issues could be fixed with different network topologies, different speed, and pause time of the MN; and with the use of static routing etc. The packet success ratio, when the MN is far away from the GW, i.e., 16 hops, is just about 0.4 for a MN moving with the speed of 20 m/s. As the number of hops between the GW and the MN decreases packet success ratio increases. As the MN reaches closer the GW the success ratio approaches to 1, and the end-to-end delay to 0.01 seconds. Moreover, it can be seen from Figure 17 that when the speed of the MN is 20 m/s the packet success ratio is better than when the speed is 25 m/s. This is because as speed increases the number of handoff increases, which can lead to a significant packet loss. Also, when the speed increases exponentially, there is a possibility that the MN will be lost in the PAN. This is because, as the new SN wakes up for the handoff process, the MN may have already crossed the new SN. As shown in Figure 17, when the MN is 5 hop away from the GW, the packet success ratio at the speed of 30 m/s is almost double than that of speed of 25 m/s. It should be noted that this type of anomaly in the graph is observed due to i) the speed of the MN, that triggers routing path discovery more frequently, ii) the link congestion, and iii) the duty cycle of SNs. Note that the link congestion is not caused by the SNs which are relaying packets, but the SNs around the MN which are participating in broadcast messages for AODV. Also note that we have used standard MAC Protocol of IEEE 802.15.4, i.e., CSMA/CA, as underlying MAC protocol. The results of the packet success ratio, and the end-to-end delay could be improved significantly for MAC Protocols, like X-MAC [30], C-MAC [31] or RI-MAC [32]. Figure 16: Delay vs. number of hops with variable MN’s speed (LoWMob). Figure 17: Packet success rate vs. number of hops with variable MN’s speed (LoWMob). The performance of our LoWMob scheme in terms of end to end delay and packet success ratio is good when the MN is closer to the GW. But usually it is not the case, because the MN can roam anywhere within the network. Moreover, if the network size increases the performance of our LoWMob scheme decreases dramatically. Also as the speed increases the number of handoff increases, thus degrading the network lifetime. In order to simulate DLoWMob in Qualnet v. 4.5, we have deployed MSPs (In our simulation, PAN coordinator is represented as MSP) in such a fashion that they could find the shortest path towards the GW. The results shown below depict the scenarios when MN's current MSP sends a MNs packet to the GW or to another MSP. As shown in Figure 18 and Figure 19, at any speed of the MN, the data packets are always bridged over five hops.