## 5 Numerical Results
### Performance Comparison  
To evaluate the effectiveness of the proposed mixed mechanism, a performance comparison experiment is conducted between the proposed mixed mechanism and existing mechanisms using numerical results. We compare non\(-\)emergency packets' average latency, state switching rate, and energy consumption with respect to whether to use the wakeup threshold mechanism [19] or the dynamic access probability mechanism (which can be regarded as a variation of the RED [23] method where the minimum threshold is 0 and maximum threshold is equal to the cache size \(K\)). Due to the adjustability of the proposed mixed mechanism, the existing mechanisms for comparison can be obtained by changing the values of the adjustment factor \(\alpha\) and wakeup threshold \(H\). The differences between contrast mechanisms are shown in Table 4. The parameter settings of different mechanisms are shown in Table 5, and other fixed parameters are shown in Table 6.  
Figures 12-14 show the performance comparison of non\(-\)emergency packets' average latency \(\eta_{2}\), state switching rate \(\epsilon\), and energy consumption \(E\) of the CH under different mechanisms. From Figures 12 and 13, compared with the traditional mechanism, introducing an access probability mechanism can effectively reduce the non\(-\)emergency packets' average latency, but this will also increase the state switching rate of the CH accordingly. On the contrary, introducing a wakeup threshold mechanism can reduce the state switching rate of the CH but also increase non\(-\)emergency packets' average latency. Therefore, introducing a single mechanism cannot effectively balance these two performance indexes. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Fixed Parameters** & **Symbols** & **Values** \\ \hline ine Cache capacity & \(K\) & 10 \\ Emergency packets’ arrival rate & \(p_{1}\) & 0.04 \\ Emergency packets’ service rate at CH & \(s_{1}\) & 0.10 \\ Non\(-\)emergency packets’ service rate at CH & \(s_{2}\) & 0.15 \\ Energy consumption for keeping CH in sleep state & \(E_{1}\) & 0.20 (W) \\ Energy consumption for changing CH from sleep state to & \(E_{2}\) & 2 (W) \\ Energy consumption for changing CH from working state to & \(E_{3}\) & 1.50 (W) \\ sleep state & \(E_{4}\) & 1 (W) \\ \hline \hline \end{tabular}
\end{table} 
Table 6: The fixed parameters of the experiment for performance comparison. \begin{table}
\begin{tabular}{l l l l l} \hline \hline
**Mechanism Names** & **Tail\(-\)Drop** &
\begin{tabular}{l} **Sleep/** \\ **Wakeup Mode** \\ \end{tabular} & **Wakeup Threshold** & **Dynamic Access Probability** \\ \hline Traditional mechanism & Yes & Yes & No & No \\ Dynamic access probability mechanism & Yes & Yes & No & Yes \\ Wakeup threshold mechanism & Yes & Yes & Yes & No \\ Mixed mechanism & Yes & Yes & Yes & Yes \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Differences between contrast mechanisms. \begin{table}
\begin{tabular}{l l l l} \hline \hline
**Mechanism Names** & **Wakeup Threshold \(H\)** & **Adjustment Factor \(\alpha\)** & **Access Probability \(f\)** \\ \hline Traditional mechanism & 0 & \(\infty\) & 1 \\ Dynamic access probability mechanism & 0 & 12 & auto \\ Wakeup threshold mechanism & 5 & \(\infty\) & 1 \\ Mixed mechanism & 5 & 12 & auto \\ \hline \hline \end{tabular}
\end{table} 
Table 5: The values of adjustment factor and wakeup threshold under different mechanisms. Moreover, in Figures 12-14, under the parameter settings of this experiment, the performance of the traditional mechanism of the CH shows a polarized trend when the non\(-\)emergency packets arrival rate is at a low level and high level. With the increase in non\(-\)emergency packets' arrival rate, the state switching rate of the CH shows a drastic change. The mixed mechanism proposed in this paper has relatively smooth trends for these two performance indexes and is more stable under different packet loads. (We use range to express the difference between the maximum value and the minimum value.