docs/architecture/architecture.rst

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.. SPDX-License-Identifier: CC-BY-4.0
.. Copyright (C) 2019 CMCC 


O-RAN Architecture Overview
===========================
O-RAN SC architecture follows O-RAN Alliance defined architecture.


.. image:: media/o-ran-architecture.png
    :scale: 40 %

Figure 1: O-RAN architecture overview

In the O-RAN architecture, the radio side includes Near-RT RIC, O-CU-CP, O-CU-UP, O-DU, and O-RU. The management side includes Service Management and Orchestration Framework that contains a Non-RT-RIC function. 


Components Definition
---------------------
For the purposes of the present document, the terms and definitions given in 3GPP TR 21.905 [1] and the following apply. A term defined in the present document takes precedence over the definition of the same term, if any, in 3GPP TR 21.905 [1].


near-RT RIC: 
O-RAN near-real-time RAN Intelligent Controller: a logical function that enables near-real-time control and optimization of O-RAN elements and resources via fine-grained data collection and actions over E2 interface.


non-RT RIC:
O-RAN non-real-time RAN Intelligent Controller: a logical function that enables non-real-time control and optimization of RAN elements and resources, AI/ML workflow including model training and updates, and policy-based guidance of applications/features in near-RT RIC.

NMS:
A Network Management System 


O-CU:
O-RAN Central Unit: a logical node hosting RRC, SDAP and PDCP protocols


O-CU-CP:
O-RAN Central Unit – Control Plane: a logical node hosting the RRC and the control plane part of the PDCP protocol


O-CU-UP: 
O-RAN Central Unit – User Plane: a logical node hosting the user plane part of the PDCP protocol and the SDAP protocol


O-DU: 
O-RAN Distributed Unit: a logical node hosting RLC/MAC/High-PHY layers based on a lower layer functional split.


O-RU: 
O-RAN Radio Unit: a logical node hosting Low-PHY layer and RF processing based on a lower layer functional split.  This is similar to 3GPP’s “TRP” or “RRH” but more specific in including the Low-PHY layer (FFT/iFFT, PRACH extraction).  


O1: 
Interface between management entities in Service Management and Orchestration Framework and O-RAN managed elements, for operation and management, by which FCAPS management, Software management, File management shall be achieved. 


O1*: 
Interface between Service Management and Orchestration Framework and Infrastructure Management Framework supporting O-RAN virtual network functions.


xAPP: 
Independent software plug-in to the Near-RT RIC platform to provide functional extensibility to the RAN by third parties.