## 5 Simulation Results
### Effects on Collision Avoidance for Control Packets  
At this stage, we introduce a method for SREQ collision avoidance (as described in Section 4.1 and 4.2) to IRDT and show the strong effects of this method. For the evaluation of this method for SREQ collision avoidance, we assume that exchanges of routing tables are not considered and all nodes have correct routing tables. The reactive setting of the intermittent interval is shown in Figure 7, and its parameters are shown in Table 2. \(T_{max}\) is set by assuming continuous operation of about several years, and a short \(T_{min}\) is set in order to reduce SREQ collisions. After the interval becomes \(T_{min}\), it is increased in steps of \(T_{i}\) at every transmission of an ID packet. On the other hand, the proactive method uses \(T^{*}\). Here, as previously discussed in Section 4.2, each node can obtain the approximate value of \(T^{*}\) by calculating the minimum value of Equation (7).  
By avoiding control packet collisions, a higher collection ratio and lower energy consumption are achieved. In particular, the collection ratio in the proactive method is over 99.5% even when the packet generation rate is 0.030 (Figure 14(a)). This result indicates that IRDT can perform efficiently even at comparatively high packet generation rates.  
Regarding the maximum energy consumption, its increase can be suppressed by using the proactive method with an interval of \(T^{*}\), as shown in Figure 14(b), due to the prevention of control packet collisions. Although the reactive method can also reduce energy consumption, except in the case of a packet generation rate of 0.002, it consumes larger amounts of energy than the original IRDT with the 0.1 s interval since the reactive mechanism attempts to avoid collisions after at least one collision has occurred. If SREQ collisions tend to occur in the neighboring nodes of the sink, for example, if there is a large number of such nodes, the improved IRDT is more effective even than the original at nodes adjacent to the sink. Additionally, preventing recurring SREQ collisions and shortening the ID waiting time can decrease energy consumption.  
An intermittent interval of \(T^{*}\) results in a 50% reduction of the maximum energy consumption as compared with the reactive setting of the intermittent interval at a packet generation rate of 0.002. Although a 40% reduction in energy consumption is also achieved at a packet generation rate of 0.030, with the proactive method the consumption of energy is as high as with the original IRDT with an interval of 0.1 s.  
Since the shorter intermittent interval derived from \(T^{*}\) yields greater chances of receiving data packets, this leads to implosion of the traffic. Therefore, a load balancing mechanism is necessary in  
\begin{table}
\begin{tabular}{l l} \hline Parameter & Value \\ \hline \(T_{max}\) & 1.5 s \\ \(T_{min}\) & 0.1 s \\ \(T_{i}\) & 10 ms \\ \(P_{f}\) & 50\% \\ \hline \end{tabular}
\end{table}
Table 2: Parameter settings.  
order to reduce the maximum energy consumption, and this issue will be investigated in our future research.  
Figure 14: Improved performance of IRDT.  
Regarding the average energy consumption, when packets are generated infrequently, both the proactive and the reactive method suppress the increase in energy consumption, while at intermittent intervals of higher frequency, the reactive method consumes more energy than the original IRDT with an interval of 0.1 s. In addition, a reduction of 15% and 48% in average energy consumption is attained when the packet generation rate is 0.002 and 0.030, respectively.