## 6 Results and Discussion  
To evaluate the navigation algorithm that combines CPN and SPF (CPN&SPF) as well as the AHCPN-based energy-efficient protocol, we design an experiment that involves four scenarios with 30, 60, 90, 120 evacuees, respectively. [PERSON]'s shortest path algorithm and CPN-based algorithm with a time metric (CPNST) [45] are performed for comparison purpose. Evacuees can communicate with the cloud through UMTS directly or use Bluetooth to relay data to other smart phones with a higher percentage of remaining energy and then transmitting to cloud severs through 3G. The percentage of survivors of five randomised experiments is shown in Figure 3. Owing to the benefit of wide paths in the shopping small, all civilians are able to evacuate at a low occupancy rate (30 evacuees). However, in relatively high population densities, both CPNST and CPN&SPF result in more survivors than [PERSON]'s shortest path algorithm. This is due to the congestion-ease mechanism in CPNST. Meanwhile, SPF can also ease congestion, because it can generate large repulsive forces for the evacuees in proximity. In comparison with CPNST, CPN&SPF performs slightly better in densely-populated scenarios (90 and 120 evacuees). This is because CPN&SPF organises evacuees as loose clusters and, therefore, increases the likelihood for an evacuee to upload data through other smart phones with more remaining battery power. As a result, the probability of being trapped due to the depletion of the smart phone is decreased. Furthermore, the coordinated behaviour increases the probability of an evacuee with a depleted smart phone to follow other evacuees rather than wandering in the building. This can be confirmed by the fact that the outcome of experiments using the AHCPN \begin{table}
\begin{tabular}{|c|c|c|c|} \hline
**Communication Mode** & **Download** & **Upload** & **Signal Rate** \\ \hline
3G & \(0.001224x\) & \(0.0003375x\) & 2 Mb/s \\ \hline Bluetooth & \(0.0001377x\) & \(0.00012012x\) & 1 Mb/s \\ \hline Wi-Fi & \(0.0003057x\) & \(0.0001586x\) & 54 Mb/s \\ \hline ZigBee & \(0.0002861x\) & \(0.0003164x\) & 250 Kb/s \\ \hline \end{tabular}
\end{table} 
Table 4: The energy consumption of smart phones in joules with regard to the transferred data \(x\) in byte and the related signal rate. \begin{table}
\begin{tabular}{|c|c|} \hline
**States** & **Energy Model** \\ \hline Suspended & \(0.3394x\) \\ \hline Idle & \(0.1049x\) \\ \hline High power & \(0.1049x+y\) \\ \hline \end{tabular}
\end{table} 
Table 3: The energy consumption of different states in joules with respect to the elapsed time in seconds. Term \(x\) represents the elapsed time, and \(y\) depicts the energy utilization on the smart phone side when performing the emergency navigation system. energy-efficient protocol is better than for the counterparts that use UMTS directly. The AHCPN protocol can reduce the likelihood of depleting a smart phone and, therefore, decreases the possibility of an evacuee being trapped in the built environment. The results we present are numerical in nature, while it would be interesting also to discuss detailed simulations in a virtual reality environment [58]. Figure 4 presents the average number of drained smart phones in the experiments. When using 3G mode to communicate with the cloud, [PERSON]'s algorithm achieves the least number of drained smart phones, especially at a high occupancy rate. This is because both the CPNST and CPN&SPF and do not follow the shortest path. Hence, evacuees will traverse more landmarks and upload more photos to the cloud. However, by employing the AHCPN protocol, the number of depleted smart phones decreases significantly for all three algorithms. Moreover, there is no drained smart phone when combining the CPN&SPF algorithm with the AHCPN protocol. This confirms that routing evacuees in loose groups can contribute to the power-balancing of smart phones. Figure 5 shows the standard deviation of the remaining percentage of battery power for smart handsets.