-Advanced-Pro as well as 3GPP releases 15, 16-onward for the 5G RAN and core [216]. Furthermore, it is compatible with several software-defined radios (SDRs) and commercial-of-the- shelf (COTS) cellular phones. OAI is licensed under OAI public license 1.1 for the RAN software and Apache V2.0 for the core software. Since 2018, OAI has been developing the Openair5G software for 5G RAN to operate on the EPC considering NSA deployment. Currently, OAI started the development of the 5G SA option to be accomplished in 2022 onward. The deployment of the 5G RAN software on OAI considers the split option 7.2 [216]. In Openair5G software, the DU processes L1 and L2 that communicates via the functional application platform interface (FAPI)10 protocol. Moreover, the CU processes L3 and communicates with the DU via F1 interface standardized by 3GPP. On the other hand, OAI is developing the 5G core functionalities for the 5G SA architecture within the software openairCN to be completed in 2022 onward. The 5GC is decoupled into UP and CP. In the first phase of the 5GC deployment, OAI considers the mandatory 5G core functions such as user-plane function (UPF), access and mobility management function (AMF), and session management function (SMF) [218]. Operating a real-time E2E network by using OAI demands a powerful PC for the gNB that can be interfaced to several types of SDR such as universal software radio peripheral (USRP) X310 and N310. Meanwhile, OAI supports the deployment of LTE and 5G software without actual SDRs by providing four simulators as follows [216]: 1. L1 simulator: It analyzes E-UTRAN stack protocol for multiple UE considering IF4.5 interface between the UE and the eNB/gNB. 2. Basic simulator or RFsimulator: It evaluates the E-UTRAN stack protocol for one or multiple UEs with emulation of the RU. 3. Uplink and downlink simulators (ulsim/dlsim): They analyze the physical layer of the UE and the eNB/gNB. 4. L2 simulator that simulates the upper layers for the UE and the eNB/gNB where the MAC and PHY layers commun