## 5 Experimental Results  
In this section, we present the result of experiments evaluating the performance of our proposed global IP-WSN scheme, and compare the performance of our proposed scheme to MIPv6 and PMIPv6. In the figures our proposed global IP-WSN scheme is represented as SPMIPv6. 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 equipped with an AMD Athlon(tm) 2.5 GHz CPU and 2 GB primary memory. We use the network simulator tool NS2 [24] on VMware based Linux Fedora 4. Now let us discuss the result with the figures. The Figure 15 depicts the signaling cost with respect to the number of IP-WSN nodes in term of the MIPv6, PMIPv6 and SPMIPv6. Signaling cost increases as the number of IP-WSN nodes increases. However, proposed IP-WSN scheme based on SPMIPv6 incurs much less signaling cost compared to MIPv6 and PMIPv6 as the number of IP-WSN nodes increases. The IP-WSN based SPMIPv6 scheme reduces signaling cost by 60% and 56% with respect to MIPv6 and PMIPv6 in terms of the number of IP-WSN nodes. The unit of signaling cost is the number of control messages exchanged for communication. Figure 16 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 IP-WSN scheme based on SPMIPv6 shows better performance with respect to both PMIPv6 and MIPv6. In all cases signaling cost increases in a linear pattern. IP-WSN scheme based on SPMIPv6 reduces signaling cost by 56% and 53% with respect to MIPv6 and PMIPv6 in terms of the number of hops. The unit of signaling cost is the number of control messages exchanged for communication. Figure 17 shows the mobility cost with respect to the number of mobile sensor nodes in MIPv6, PMIPv6 and IP-WSN based on SPMIPv6. Mobility cost increases as the number of mobile sensor nodes increases. IP-WSN based on SPMIPv6 enjoys less mobility cost with respect to MIPv6 and PMIPv6. Difference of mobility cost becomes more reasonable when number of mobile sensor nodes 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. The unit of mobility cost is the number of control messages exchanged due to mobility. Figure 15: Number of IP-WSN nodes Signaling Cost. Figure 18 shows the mobility cost with respect to number of hops used by the mobile sensor nodes in MIPv6, PMIPv6 and IP-WSN based on SPMIPv6. Mobility cost increases exponentially as the number of hops increases. In this scenario also, our proposed IP-WSN scheme based on SPMIPv6 enjoys less mobility cost with respect to MIPv6 and PMIPv6. The proposed IP-WSN scheme based on SPMIPv6 scheme reduces 67% and 60% mobility cost with respect to MIPv6 and PMIPv6 in terms of the number of hops. Figure 16: Number of Hops _vs._ Signaling Cost. Figure 17: Number of IP-WSN nodes _vs._ Mobility Cost. Figure 19 shows the energy consumption with respect to payload. Energy consumption is linear in MIPv6, PMIPv6 and IP-WSN based on SPMIPv6. However, due to fragmentation overhead, energy consumption increased rapidly and then it represents the linear characteristics again. In this scenario, proposed IP-WSN scheme based on SPMIPv6 is energy efficient compared to other two approaches. Figure 20 depicts the energy consumption with respect to the IP-WSN node density in term of the MIPv6, PMIPv6 and the proposed IP-WSN based on SPMIPv6.