## 6 Results and Evaluation
### IoT-LAB Realistic Scenario
Network Latency (End-to-End Delay)  
Figure 11 shows the comparison between the latency of ETX and OF0 with IoT-LAB uniform and random scenarios. It shows that OF0 has higher network latency than ETX because ETX considers the link details in computing the best path to destination while OF0 depends on hop count. The comparison shows that latency using ETX in uniform and random scenarios outperforms OF0 as random scenarios suffer from higher network latency while the network size increase. The average latency is calculated here after extracting the actual time of sending at client's nodes and the receiving time at root node using Foren6 diagnostic tool and command line tools of the serial lines of the testbed. Figure 10: Comparison between packet delivery ratio in IoT-LAB testbed using OF0 and ETX with random and uniform network topology. Figure 9: Comparison between total control traffic overhead in IoT-LAB testbed using OF0 and ETX with random and uniform network topology. Energy Consumption  
Power consumption is considered as the most critical constraint of any wireless sensors network. In this study, we measure the power consumption while the RPL routing protocol is running. In this study, we develop a power trace application with the help of the energyst power profile in the Contiki operating system to measure the power consumption of transmitter, receiver, idle-lessening mode, and CPU power. It's recommended measuring only the radio transceiver power as its considered as the major power consumption source in any node. Nearly the majority of power is consumed on retransmission and idle listening. In this study, we suggest the radio time to indicate and reflect the power consumption instead of considering the absolute power consumption in joules. Radio on time is the percentage of the radio during the total time of the experiment while the nodes are on for sending or receiving. We change the network density from 20 nodes to 140 nodes to measure the consumed power, as the network becomes denser as more consumed energy. This increase of power consumption due to the more transmissions sent by the node. As shown in Figure 12, the total absolute power consumption is measured over time and the total power consumption is mainly the transceiver power while the other sources of power are very small. So, in our study we neglect the low power mode and CPU consumption. We focus on computing the % radio on time which represents the energy consumption. The more network traffic, the more consumption of the energy and vice-versa. If we send more application messages, the more energy is consumed. In Figure 13, the average power consumption is indicated for OF0 and ETX with uniform and random topologies. ETX consume less power than OF0 while random topologies need more power for both OF0 and ETX to retransmit packets. In Figure 14, the power consumption is expressed using the on radio time percentage which decreased as the packet reception ratio increased. ETX on radio time is less than OF0 in both uniform and random scenarios. Figure 11: Latency comparison using OF0 and ETX with uniform and random IoT-LAB testbed. Figure 12: The total absolute power consumption for one testbed node measured over time.