# Design of Wireless Sensor Network for Agricultural Greenhouse Based on Improved Zigbee Protocol
## 3 Experimental Design and Results
### Experimental Results  
#### 3.4.1 Result Analysis under Different Pause Times of Mobile Nodes  
In this research, the CBR sending rate is always three packets/s, and the pause time of the mobile node is changed to 0 s, 50 s, 100 s, 150 s, 200 s, 250 s, 300 s, 350 s, 400 s. The node pause time will affect the network topology changes. The mobility of nodes in the network will weaken with the increase in the pause time, and the topology changes will gradually become stable [29].  
(1) Packet delivery rate  
Figure 4 shows the performance difference of the two routing protocols in the packet delivery rate under different mobile node pause times. Under the same circumstances, the packet delivery rate of the EMP-ZBR routing protocol is always greater than that of the ZigBee routing protocol, which increases the packet delivery rate by 1.1% on average, and improves the network congestion to a certain extent [30].  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Parameters** & **Value** \\ \hline Channel type & Channel/Wireless Channel \\ Network Interface & Phy/WirelessPhy/802\_15\_4 \\ MAC type & Mac/802\_15\_4 \\ Wireless communication model & Antenna/OmniAntenna \\ Transfer model & TwoRayGround \\ Topological size & 30 ft \(\times\) 90 ft \\ Number of nodes & 60 \\ Packet size & 512 bytes \\ Simulation time & 400 s \\ Energy model & EnergyModel \\ Node initial energy & 80 J \\ Transmit power & 0.85 W \\ Received power & 0.49 W \\ Sleep power & 0.15 W \\ \hline \hline \end{tabular}
\end{table}
Table 1: The simulation parameters.  
Figure 4: Result of the packet delivery rate at different pause times.  
Figure 5 shows the difference in route discovery frequency of the two routing protocols under different mobile node pause times. Under the same pause time, the routing discovery frequency of the EMP-ZBR routing protocol is significantly lower than that of the ZigBee routing protocol, which slows down the routing discovery frequency by 15.2% on average, indicating that EMP-ZBR reduces the number of times the source node routing requests are initiated and that the network is more stable.  
(3) Routing control overhead  
Figure 6 shows the relationship between the routing control overhead and mobile node pause time. Under the same pause time, the EMP-ZBR routing protocol selects nodes with sufficient energy and a large remaining queue buffer length to establish paths, and fewer messages are used for routing initiation and routing maintenance. Compared with the traditional ZigBee protocol, the average reduction of 21% of the routing control overhead more effectively alleviates the impact of path congestion and link breaks on the network.  
(14) End-to-end average delay  
Figure 7 shows the relationship between the end-to-end average delay and mobile node pause time. Under the same pause time, the average delay of the EMP-ZBR routing protocol is significantly lower than that of the ZigBee routing protocol, and it will not pass  
Figure 5: Route discovery frequency result with different pause times.  
Figure 6: Routing control overhead results for different pause times.  
through congested nodes during data transmission, which reduces the average delay in the network [31]. Compared with the traditional ZigBee protocol, the EMP-ZBR routing protocol reduces the end-to-end average delay by 8.1 ms on average, which plays a great role in alleviating congestion.