# A Survey on Open Radio Access Networks: Challenges, Research Directions, and Open Source Approaches
## 6 Challenges and Future Research Directions
### Open RAN Field Issues
As detailed in a study by [100], this application of DT technology is used to explore possible scenarios and train AI/ML models that can address all potential corner cases in a real-world setting. It will play a crucial role in achieving the predefined 6G KPIs. The other method proposed by [101] to improve RAN's performance and cost is PlaceRAN. PlaceRAN focuses on minimizing computing resources and maximizing the aggregation of radio functions to optimize the placement of radio functions in virtual NG-RAN planning. PlaceRAN uses a disaggregated RAN combination (DRC) concept and multi-stage problem formulation, thus enabling the management of units and protocols as a set of radio functions. The result achieved by [101] showed that PlaceRAN can reduce the number of DRCs in the network, by taking functional split options, one-way tolerated latency, cross-haul bandwidth, and a bandwidth derived from an analysis conducted in a project mentioned in the study. Secure Open RAN is the next popular challenge that is widely discussed. Every network connectivity should be deployed as securely as possible, and so does the Open RAN and the 5G network. As users of network connectivity, we surely do not want to experience any fraud or data stealing that will threaten our safety. Therefore, a secure Open RAN should be seen as a big challenge, which should be discussed in further research. Open RAN promotes the advantages of its disaggregation and interoperable pillars. On the other hand, these pillars also introduce new challenges regarding security. Disaggregation and virtualization are the themes of Open RAN. However, decoupling the software from the hardware expanded the security threat surface [102]. Major virtualizationtechnologies are vulnerable to security attacks, including MEC, SDN, NFV, network slicing, and cloud [103]. O-RAN Alliance's SFG has noticed that decoupling, containerization, and virtualization vulnerabilities can be exploited by threat actors [104]. Other works have also mentioned some of the vulnerabilities relating to disaggregation, such as insufficient identity, credential, and access management; insecure interfaces and APIs; system vulnerability; and shared technologies vulnerabilities [4; 103]. The interoperable pillar of Open RAN also introduces new security challenges. One of them is that different vendors might use different degrees of security in their products [7]. Although vendors should practice best security practices, not all will implement adequate secure management interfaces. The same case happens with the standards developed by the O-RAN Alliance. The O-RAN Alliance has two fundamental pillars: openness and intelligence. Each pillar introduces new security challenges. Additional interfaces and functions in O-RAN architecture add the area of threat surface [6; 7; 104]. Incorporating AI/ML in O-RAN architecture, known as the intelligence pillar, also adds a new surface threat targeting AI/ML-related functions in O-RAN. Other works have also discussed the new security challenges of using AI/ML in mobile networks [105; 106]. Another additional threat surface comes from using open-source code. Open-source software gives both advantages and disadvantages regarding security [4; 107]. However, extra security measures should still be taken because adversaries could easily access the same open-source code used in the O-RAN system and exploit its vulnerabilities [7; 107]. As explained in Section 3, O-RAN Alliance is working carefully to address the security challenges with its SFG. SFG specifies the security requirements in the O-RAN system in [108; 109]. Hopefully, the O-RAN Alliance can develop a secure architecture, framework, and guidelines for its Open RAN standards.