# Deep dive into architecture of OAI gNB. Introduction in L2 Simulator Framework. OAI UE used for the test. ###### tags: `Internship 2nd level` :::success **Goals:** - Understanding of the Architecture of OAI gNB. - Introduction in L2 Simulator Framework. - Overvew OAI UE used for the test. **Resources:** - [The main principles of the Architecture of OAI gNB](https://www.openairinterface.org/docs/workshop/1stOAINorthAmericaWorkshop/Training/KALTENBERGER-OAI_basics_June_2019.pdf) - [Description of the L2 Simulator Framework](https://openairinterface.org/oai-5g-ran-project/) - [OAI UE for the test](https://github.com/EpiSci/oai-lte-5g-multi-ue-proxy) ::: ## Architecture of open-source software-based implementation (OAI) of 3GPP. - ![](https://imgur.com/a5IEGaw.png) Technologies – Starting at LTE (Rel 8), including features from LTE-Advanced (Rel 10/11/12), LTE-Advanced-Pro (Rel 13/14), going on to 5G Rel (15/16/…) – Spanning the full protocol stack of 3GPP standard E-UTRAN (eNB, gNB, UE) EPC (MME, S+P-GW, HSS) – Realtime RF and scalable emulation platforms – Works with many SDR platforms (ExpressMIMO2, USRP, LimeSDR, …) Makes it is feasible to put a fully-compliant 4G eNodeB, 5G gNB and EPC in a commodity x86-based computer (or data center) Objectives – Building a community of individual developers, academics and major industrials embracing open-source for 5G – Become a strong voice and maybe a game-changer in the 3GPP world Real impact from “the little guys” on 3GPP systems ## L2 Simulator Framework. L2-simulation framework: Using actual radios or even RFsimulator does not allow testing a large number of UEs. Therefore, the L2simulator offers the possibility of connecting the OAI UE with the OAI xNB (eNB in LTE and gNB in 5G) through the nFAPI interface defined by the Small Cells Forum (SCF). nFAPI splits the xNB into a MAC entity and a PHY entity. In OAI, the xNB MAC connects through the nFAPI interface to a channel proxy that simulates the channel and allows to connect many UEs to the MAC stub. Each UE is the simulated OAI UE that connects to the proxy. The OAI L2-simulator is a flexible tool that can serve many purposes. As an example, some partners of OAI are interfacing it with the ETSI TTCN-3 testing language framework. This would allow for building a conformance testing tool for third-party UEs. - ![](https://imgur.com/JbboPmv.png) - [OAI UE used for the test](https://github.com/EpiSci/oai-lte-5g-multi-ue-proxy)