## 5 Experimental Results  
In this section, we present the results of experiments evaluating the performance of our scheme, and compare the performance of our proposed scheme to MIPv6 and PMIPv6. First, we evaluate the performance of our proposed approach by mathematical analysis. Then, we set signaling cost and mobility related cost for the number of IP based sensor nodes and number of hops traverse during the mobility phase in order to evaluate the consequences of our proposed scheme with PMIPv6 and MIPv6. Finally, we summarize the key characteristics of our proposed approach as compared to PMIPv6 & MIPv6 approach.  
We have implemented the model and evaluate the parameter such as the signaling cost and mobility related cost as presented in this paper. The experiments were conducted on a computer with AMD AthlonTM 2.5 GHz CPU and 2 GB primary memory. We use network simulator tool NS2 on VMware based Linux Fedora 4.  
The Figure 9 depicts the signaling cost with respect to the number of IP-WSN node in term of the MIPv6, PMIPv6 and SPMIPv6. Signaling cost increases as the number of IP-WSN nodes increases. However, SPMIPv6 incurs much less signaling cost compared to MIPv6 and PMIPv6 as the number of IP-WSN nodes increases. The SPMIPv6 scheme reduces signaling cost by 60% and 56% with respect to MIPv6 and PMIPv6 in terms of the number of IP-WSN nodes.  
Figure 9: Number of IP-WSN nodes. Signaling Cost.  
Figure 10 depicts the signaling cost with respect to the numbers of hops the data or signal traverses to reach the destination node. In this case we consider a maximum 15 hops. Signaling cost increases linearly as the number of hops increases. The proposed scheme shows better performance with respect to both PMIPv6 and MIPv6. In all cases signaling cost increases in a linear pattern. SPMIPv6 scheme reduces signaling cost by 56% and 53% with respect to MIPv6 and PMIPv6 in terms of the number of hops.  
Figure 11 shows the mobility cost with respect to the number of mobile sensor nodes in both MIPv6 and SPMIPv6. Mobility cost increases as the number of mobile sensor node increases. SPMIPv6 enjoy less mobility cost with respect to MIPv6 and PMIPv6.  
Figure 10: Number of Hops _vs._ Signaling Cost.  
Figure 11: Number of IP-WSN nodes _vs._ Mobility Cost.  
Difference of mobility cost becomes more reasonable when the number of mobile sensor node increases. The SPMIPv6 scheme reduces signaling cost by 62% and 57% with respect to MIPv6 and PMIPv6 in terms of the number of IP-WSN nodes.  
Figure 12 shows the mobility cost with respect to number of hops used by the mobile sensor nodes in MIPv6, PMIPv6 and SPMIPv6. Mobility cost increases exponentially as the number of hops increases. In this scenario also, our proposed scheme (SPMIPv6) enjoys less mobility cost with respect to MIPv6 and PMIPv6. Proposed SPMIPv6 scheme reduces 67% and 60% mobility cost with respect to MIPv6 and PMIPv6 in terms of the number of hops.  
The Figure 13 shows the energy consumption with respect to payload. Energy consumption is linear in MIPv6, PMIPv6 and SPMIPv6. However, due to fragmentation overhead, energy consumption increased rapidly and then it represents the linear characteristics again.  
Figure 12: Number of Hops _vs._ Mobility Cost.  
Figure 13: Data payload _vs._ Energy consumption.  
The Figure 14 depicts the energy consumption with respect to the IP-WSN node density in terms of the MIPv6, PMIPv6 and SPMIPv6. Energy consumption increases as the IP-WSN node density increases. Our proposed scheme increases the performance linearly compared to MIPv6 and PMIPv6. Therefore, the energy consumption increases more rapidly as the density of IP-WSN node increases.