# Efficient Cluster Tree Topology Operation and Routing for IEEE 802.15.4-Based Smart Grid Networks
## 5 Performance Evaluations  
The NS-2 simulator (version 2.34) was used to evaluate the performance of the proposed schemes. The common simulation parameters are summarized in Table 2. In the simulations, the nodes in the network operated in the beacon-enabled mode and were distributed randomly. In the simulation, the \(BO\) was set to six, and the \(SO\) was set to three. The cluster created by the gateway contained 30 nodes. The energy model in [60] defines four radio modes: transmitting, receiving, idle, and sleeping. The energy consumption was calculated by multiplying the time spent on the radio in each state by the energy consumption in that mode. To evaluate the consumed energy, the energy model of CC2630 (which is a single chip, 2.4 GHz, IEEE 802.15.4-compliant RF transceiver [60]) was used. In the simulation, clusters from other gateways were operated sequentially to determine the effect of interference from nearby devices. Gateway 1 began operation at 0.0 s. On the other side, gateway 2 started its operation at 253.19 s, and gateway 3 started its operation at 749.13 s. The simulations were run for 1000 s.  
Table 3 lists the types of traffic generated by the nodes in the simulation. \begin{table}
\begin{tabular}{c c} \hline \hline
**Parameters** & **Value** \\ \hline Transmission power (dBm) & 3.5 \\ Noise factor (dB) & 10.0 \\ Synchronization mode & Beacon-enabled \\ Carrier sense sensitivity & \(-\)85 dBm \\ Data rate & 250 kbps \\ IEEE 802.15.4 header length & 22 bytes \\ RX current consumption & 5.9 mA \\ TX current consumption & 9.1 mA \\ IDLE current consumption & 0.550 mA \\ Sleep current consumption & 0.001 mA \\ \(BO\) & 6 \\ \(SO\) & 3 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Simulation parameters. Figure 19: SD allocation algorithm to prevent collision during channel movement. In this simulation, an arbitrary pair of nodes was selected to transmit data. The remaining nodes, except for the cluster head, generated data and transmitted these to the gateway. In Figure 20, the IEEE 802.15.4 Mesh protocol [53] shows a shorter latency than that of the IEEE 802.15.4 standard. This is because there are multiple paths for transmission to the destination node. In the proposed technique, data can be delivered through short paths because these do not pass through unnecessary gateways or cluster heads. In addition, the proposed method uses multiple channels. Hence, the number of competing nodes in the proposed technique is smaller than that in the other techniques. Therefore, the proposed technique has fewer collisions or backoffs and the shortest delay time. Figure 21 shows the sum of the received data frames with respect to time. In the IEEE 802.15.4 standard and IEEE 802.15.4 Mesh protocol, the sum of the received data frames did not increase because the device no longer received data after the data frames began to collide. However, the sum of the received data frames increased after a delay when the proposed scheme was used. In the proposed scheme, the gateway circumvents the use of resources because it can identify the channel and SD slot in use through the beacon frame received from a neighboring gateway. In addition, if a data frame conflict occurs between cluster members belonging to different gateways, the cluster head moves to the clean channel, selects the neighboring cluster head as the parent node, and notifies the gateway of the modification. This prevents data collisions. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Traffic Type** & **Packet Interval** & **Packet Size** \\ \hline AMI data & 18 s & 5 bytes \\ SCADA (Supervisory Control and Data Acquisition) & 1 s & 64 bytes \\ Power Quality Monitoring & 1 s & 35 bytes \\ Office Substation & 10 s & 64 bytes \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Smart grid application. Figure 20: End-to-end delay vs. node number. In Figure 22, the values of the delivery success rate are determined according to the probability of packet loss. To evaluate the performance of the proposed scheme, the delivery success rate was used.