 IF2, IF4.5, and IF5 closely adhere to the relevant standards. However, it is expected that over time OAI inter- faces implementations may become more closely aligned to the respective 3GPP, O-RAN, and Small Cell Forum standards. OAI has a number of options primarily designed to help development of new features, such as a simulator and "noS1" mode, in which a [preconfigured] RAN can be deployed without an EPC, which makes it a good platform for academic research. At the time of writing this book, OAI RAN supports LTE only; however, 5G development is underway. It is likely that at least basic functionality of EN-DC (see Section 4.3) will be supported by OAI in 2020. From the hardware perspective, parts of OAI implementation run on a generic CoTS x86 platform, which however also requires an SDR. A number of SDR hardware platforms are supported by OAI, such as: ExpressMIMO2, USRP, and LimeSDR. It is important to mention that OAI source code is distributed under the OAI license, which is free for research; however, it contains clauses allowing intellectual property rights (IPR) holders who contributed to the project to charge royalties on OAI software usage. 6.3.5.5 TIP TIP has a number of projects (e.g. OpenCellular) that may produce software and hardware components, potentially to be released and licensed as open source. However, at the time of writing this book, there are no active open source RAN projects in TIP. It must be noted that TIPs goal is to create a wide ecosystem of RAN solutions and com- ponent vendors, and there is no requirement for the implementation to be open source. Therefore, it is unlikely that a fully open source RAN implementation will emerge in TIP. 6.3.5.6 O-RAN The O-RAN Alliance, jointly with the Linux Foundation, have created the O-RAN Software Community (SC) collaboration project, with the goal of creating an open source 5G RAN implementation, to be released under the OSI-compliant Apache 2 open source license. The project is in the early stages and as of now no source code has been co