# Open Radio Access Networks For Smart IoT Systems: State of Art and Future Directions
## 2 Background
### Concept of O-RAN Technology  
The new O-RAN paradigm approach is software-based and adaptable, enabling data-informed smart control loops for cellular systems and openness, virtualization, and programmability of RAN functionality and components. As a result, network engineers can support new customized services on common physical infrastructures and vigorously rearrange them in response to user demand and network conditions thanks to the Open RAN. In addition, the network's operating expenses could decrease due to greater efficiency [26]. **Disaggregation:** It entails breaking down the RAN components into smaller chunks of functional modules that different vendors can implement. The following units emerged \begin{table}
\begin{tabular}{l l l l} \hline \hline
**Term** & **Full Meaning** & **Term** & **Full Meaning** \\ \hline NRT-RIC & Near-real-time RIC & RL & Reinforcement learning \\ \hline N-NRT-RIC & Non-real-time RIC & RU & Radio unit \\ \hline SCADA & Supervisory control and data acquisition & SDR & Software-defined-radio \\ \hline SMS & Smart manufacturing system & STS & Smart transportation system \\ \hline SWOT & Strengths weaknesses opportunities and threats & UAV & Unmanned aerial vehicle \\ \hline
3 GPP & Third Generation Partnership Project & UE & User equipment \\ \hline URLLC & Ultra-reliable and low-latency communication & ZTA & Zero-trust architecture \\ \hline \hline \end{tabular}
\end{table} 
Table 1: _Cont._by disaggregating the O-RAN components: the baseband unit (BBU), i.e., the control unit (CU), which is responsible for control plane functions, such as radio resource management and mobility management; the distributed unit (DU), which is responsible for radio frequency (RF) processing and data plane functions, such as user data forwarding; and finally, the radio unit (RU), which is responsible for radio frequency (RF) signal reception and transmission. **Virtualization:** It encompasses separating the RAN software components from the underlying hardware to allow greater flexibility and agility in the RAN and the potential for cost savings. Since software components are tightly coupled to the underlying hardware in a traditional RAN, virtualization decouples the software components from the underlying hardware to optimize the RAN's performance for different application environments or even gives room for creating a responsive cloud-based RAN that scales or shrinks based on the available demand to ease the management of the RAN. **RAN intelligent controller (RIC):** It is a key component of the O-RAN architecture. It carries out controlling and managing the RAN, and it uses software-based intelligence to optimize the performance of the network. The RIC is divided into the near-real-time RIC (NRT-RIC) and the non-real-time RIC (N-NRT-RIC). The N-NRT-RIC operates on a timescale greater than 1 s to handle non-real-time events and their respective control loops, such as configuration changes and performance optimization. The NRT-RIC operates between the 10 ms and 1 s timescale to handle near real-time events and their respective control loops, such as handovers and admission control. [PERSON] et al. [39] proposed the concept of dApps operating in the CU and DU to extend the RIC capabilities towards handling real-time control loops such as scheduling and beamforming working on timescales of less than 10 ms, even though efforts extending the RIC concept to the RU are yet to be recorded at the time of this writing. For instance, [PERSON] et al. [40] proposed edgeRic to confirm that decoupling the RIC from the RAN stack and co-locating it close to the DU can support control loops operating within sub milliseconds and even microseconds. These proposed contributions extended the RIC capabilities toward addressing the latency requirements of the next-generation smart IoT systems. **Open interface:** It involves the collection of standardized interfaces that enable the different components of the RAN to communicate with each other.