# Spectrum Based Power Management for Congested IoT Networks
## 3 System Model
### Energy Scan Algorithm  
Algorithm 1 shows how we manage the energy scan between FREDEVPLA and CN. If CN spend >5 s without any activity then the FREDEVPLA will send energy scan instruction to that specific CN. Within the instruction the energy scan time is also mentioned, which various depending on the traffic history. When received scan request from FREDEVPLA the CN will broadcast a notification for all its IoT devices and start energy scan. Once the CN receives the energy scan result it will select a channel with lowest energy and forward it to the FREDEVPLA. After selected channel has been transmitted, the CN returns to conventional communication processing. Here we like to remind our readers that all the commanding and programming is taking place from the FREDEVPLA side. This will allow CN and IoT device to concentrate on communication only.  
Below we have the general instructions inside FREDEVPLA if we consider a conventional network, once the channel is selected during initial start-up it will remain constant. This adjustment allowed data to be processed rapidly and faster transmission. It is mentioned in reference [11] that, among main factors of power consumption in IoT communication, retransmission and queue delay are the highest, which is caused because of busy channel. So, solving the busy channel will improve the use of power and overall network performance. It is seen in our result that the busy channel power consumption is significant in the congested IoT network. We solved this problem by avoiding use of busy channel in the IoT environment of the connected devices. As a result we minimized the power consumption significantly and increased the network performance.  
Figure 3: Instruction followed by FREDEVPLA.  
```
Data: CN has no activity for \(>\)5 s Result: A channel with lowest interference.
1 CN sends notification to all its child's;
2 CN execute energy scan for specified time;
3 CN select a channels with lowest energy and forward to FREDEVPLA;
4 if it is time to switch a channel for one of its CN;
5 then
6 Instruction to the corresponding CN to send its child nods next channel information;
7 CN send next communication channel to its IoT devices;
8 CN switch to selected channel;
9 Notify the FREDEVPLA;
10 Execute a normal transaction;
11 else
12 Execute a normal transaction;
13
14 end
```  
**Algorithm 1**Energy Scan Communication between FREDEVPLA and CN  
Deciding when to do energy scan, who can do it and when to use the scanned results are among the major novelty of this algorithm. It is known that these three questions have significant impact on almost any channel management algorithm for IoT network. So, the way how we solve these questions will determine the final output of our resources management algorithm. In our algorithm we focused on answering these three questions by executing at an IoT CN level even if the final result is for the IoT devices. The reason why we decided to execute from CN level is to avoid major IoT device limitations such as memory, power, processing speed, etc.  
To avoid frequent switching of the channel we implemented minimum throughput level as a requirement which is link quality value, RSSI \(\geq-85\) dBm. Hence, it is suggested from experimental measurements that a link with RSSI equal or above \(-85\) dBm could be used as a threshold for reliable link estimate [22; 25].  
As mentioned previously, the focus of this work was to minimize the network power consumption by solving spectrum management, which is one of the main problems facing an IoT network of today's world. What we did is minimize power consumption from the perspective of busy channel problem solving which is the main reason for power consumption in congested IoT environment.