## 2 Materials and Methods
### How Cognitive Radio Engage with the Industrial IoT?
#### 2.1.1 LPWAN for IIoT
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Year** & **Approaches** & **Features** & **Advantage** & **Challenges** & **Refs.** \\ \hline \multirow{4}{*}{2019} & Network functionalities are implemented via software instances in cloud & \multirow{4}{*}{Proposed an architectural specification} & \multirow{4}{*}{Improved performance} & \multicolumn{2}{c}{Strategizing regarding the implementation of the classical network functionalities, associated with the challenges in their respective implementations} & [6, 26, 31] \\  & Development of a UNIX-based network interface for LPWAN & & & Remote track vehicle status in energy consumption & Light vehicles with real-time in emerging power barriers & [7] \\ \hline \multirow{4}{*}{2018} & Traffic-pattern data set in the data-cognitive engine & Cognitive- LPWAN selects appropriate communication technologies to achieve a better interaction experience. & intelligent applications and services for the choice of different wireless-communication technologies. & Cognitive-LPWAN and test the proposed AI-enabled LPWA hybrid method & [27, 41] \\ \hline \multirow{4}{*}{2017} & Interference distribution conditioning on sensor measurement & Improves area spectral efficiency (ASE) compared to a conventional ALOHA and an adaptive transmission & Access the medium only when a sensor values is measured & Spectral efficiency need to be enhanced & [12] \\ \hline \multirow{2}{*}{2019} & Notable state-of-the-art approaches & Enhancement of different IIoT-based applications. & CR-LPWAN systems for IIoT-based applications & Lower efficiency and higher latency & [42] \\ \hline \multirow{4}{*}{2018} & The AI algorithm provides the smart control of wireless-communication technology & Cellular-communication technologies (4G, 5G) & AI-enabled LPWA hybrid method & Higher delays in communication delay and higher energy consumptions & [24] \\ \hline \multirow{4}{*}{2019} & C-LPWAN based on generic network architecture and a PHY layer front-end model & Develop CR-LPWAN systems towards enhancing IoT-based applications, including Industrial IoT (IIoT) applications & \multirow{4}{*}{Interference issue} & [36] \\ \hline \multirow{4}{*}{2020} & For integrating CR in LPWAN effectively, deciding on and physical layer & To enhance the performance of IIoT-based on applications & CRLPWAN are required for adaptive threshold techniques to improve sensing performance & Low throughput & [17] \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Summary of the different Cognitive Industrial IoT technologies and applications. setting [42]. That is very important for CR to increase the frequency utilization for scare radio resources. Lately, research has been projected using multiple access technologies for unlicensed frequency allocation [43]. IIoT system can control the frequency dynamically using cognitive radio power that maximizes radio utilization and system performance. In CR LPWANs, the radio channel between the licensed networks and the unlicensed BS only can take place within the cellular radio coverage area [24; 25; 26; 27; 28; 29; 30; 31; 32; 33; 34; 35; 36; 37; 38; 39; 40; 41; 42; 43; 44]. For convenient resource allocation by following QoS rules, the channel bandwidth allocation in LPWAN is made well-defined in wireless applications [45; 46; 47]. Hence, LPWANs face no difficulties during serving the traffic for wireless applications, even though QoS has strict requirements [48]. Moreover, CR-LPWAN is seen to be efficient whenever the primary radio network (PRN) system's radio spectrum remains underutilized, even though it has various resources. Therefore, the dynamic spectrum access is essential for efficiently managing the spectrum in CR-LPWANs for IIoT sensor nodes densely deployed [44]. Spectrum sensing functionality is the factor that distinguishes CR-LPWAN from conventional WSN. CR can adjust the operating parameters of its spectrum sensing capability dynamically; utilizing this can determine the vacant bands [45].