# Spectrum Based Power Management for Congested IoT Networks
## 4 Test Set Up  
The base setup of our test bed considers the behavior of congested IoT communications. We focus on three communication states of IoT device power consumption: (1) connected state, (2) sleep/listing state, and (3) re-transmission state. Beside these three main focuses we also analyze the power consumption at synchronization and paging state of a device. Our power measurement device is used for both power supply to the IoT device and as a current and voltage measurement. It provides up to 5 V with a high resolution current measurement with a sampling rate up to 4000 samples per second in the range from 1 \(\mu\)A to 5 A.  
Furthermore, the measurements were performed soon after the IoT device was turned on, so interference from neighboring IoT device is high. Thus, the main component of the denominator is noise, so we simulated the noise to any regular congested IoT environment. We use a laptop to track both the communication and the power measurement device. Besides measuring power consumption, we also track communication time, retransmission, packet loss and throughput. Overall, we have sent about 2000 packets, 50% of these experiments were run using the conventional network and 50% using the FREDEVPLA, our scheme.  
The experiment consists of 20 IoT sensor nodes uniformly deployed in an area of 10-60 M and connected with three collector nodes (MC1321 x EVKRM20). Every sensor can communicate with a full data rate of 50 kbps to the collectors in all available licensed channels. Collectors are placed at the center of the experiment area with only one destination FREDEVPLA. Packet arrival rate is random for every sensor in the network. To perform power consumption measurements and estimate the battery life of the IoT nodes, our power analyzer is next to FREDEVPLA, the voltage level is set constant and the current consumption is measured. FREDEVPLA is placed in the laboratory together with the power analyzer. The power analyzer supplies voltage to all IoT devices and senses the current drawn during the test phase at a sampling rate of 100 Hz. Some of important network setup futures are listed below in Table 1.  
The tests have been carried out using CodeWarrior embedded software development studio in a C++ programming environment. Application implemented are built on NXP (Freescale) standard which has IEEE 802.15.4 as a base standard.  
Figure 4 represents our experimentation setup. The experiment integrates 3 collectors (CN) connected to the channel coordinator (FREDEVPLA), which is shown to the left of the computer in Figure 4. At the bottom of the same figure, the freescale launchpads that simulate IoT devices are shown. Furthermore, the setup includes a power analyzer that measures the power consumption of each device and provides power to IoT devices. After all the IoT devices were powered, they connected wirelessly with the collectors and send/receive data. Collectors are connected directly to the FREDEVPLA via usb port. FREDEVPLA hooked-up to the computer to see the data transaction for analysis purpose.  
First we created a conventional network using three constant channels for three different coordinators. This allowed us to see the power consumption of the conventional network and the result helped us to compare our results. It is clearly seen in our result comparison part that the conventional way of communication channel usage is doing noting to reduce power consumption in a congestion IoT network.  
\begin{table}
\begin{tabular}{c c} \hline \hline Number of channels used & 16 \\ Data rate of the channel & 250 kbps \\ Execution duration & 6 h \\ Frequency & 2.4 GHZ \\ \hline \hline \end{tabular}
\end{table}
Table 1: Major network setup parameters.  
Figure 4: Physical test setup.