By Chih-Lin I and Sachin Katti.
O-RAN ALLIANCE’s specification effort, open software development, as well as testing and integration, focus on priorities set by its operator members needs. This approach allows the O-RAN ecosystem players to prioritize the delivery of a minimum viable set of end-to-end O-RAN solutions applicable in commercial networks.
O-RAN technical specification effort grows with healthy momentum. We keep expanding Radio Access Networks (RAN) standards with open interfaces and intelligent RAN functions. All published specifications are available to the general public upon agreement to the O-RAN ALLIANCE Adopter License.
O-RAN specifications published since March 2021 introduce the initial version of 11 new technical specifications or reports, comprising:
Another 22 newly released specifications bring updates to existing O-RAN standards, enriching them with new functions or updated features according to the O-RAN Architecture.
Below is a brief overview of all recently published specifications:
The O-RAN Architecture Description document specifies the overall architecture of O-RAN. It describes all the O-RAN functions and relevant interfaces that connect these functions. This version enhances the O-RAN control loops by making their execution times and interactions dependent on the use cases. It further elucidates that the execution times of the Non-Real-Time (Non-RT) and Near-Real-Time (Near-RT) control loops may overlap as dictated by the use cases. Designating the O1 interface between the Service Management and Orchestration (SMO) and the O-RU as an For Future Study (FFS) topic is another notable modification of this version. Other improvements include designating color coding to all logical interfaces shown in the architecture figures.
This document describes potential O-RAN use cases at a very high level, emphasizing how each use case is enabled by the O-RAN Architecture along with basic input data expectations and resulting actions. This version includes 1 new use case (BBU Pooling to achieve RAN Elasticity) and updated use cases (Massive MIMO Optimization).
This document describes selected O-RAN use cases in further detail to facilitate relevant O-RAN Work Groups to define requirements for associated O-RAN functions and interfaces. This version includes 1 new use case (Signaling Storm Protection) and updated use cases (Massive MIMO Optimization).
This document describes O-RAN slicing related use cases, requirements and architecture. Along with requirements and a reference slicing architecture, slicing related impact to O-RAN functions and interfaces is also captured. This version includes addition of transport network slicing sub-section and two detailed procedures: O-RAN Network Slice Subnet Instance (O-NSSI) Allocation and O-NSSI Deallocation.
This document describes the set of use cases that have been approved within O-RAN Work Group 2. It helps identify requirements for Non-Real-Time Radio Intelligent Controller (Non-RT RIC) and A1 interface and will lead to formal drafting of interface specifications. The motivation, resources, steps involved and data requirements for each use case are described, followed by the respective functional and non-functional requirements derived therein.
Non-RT RIC functional architecture technical report offers the rApp definition, the Non-Real Time (RT) Radio Intelligent controller (RIC) Framework functions and the R1 interface. The external interfaces are also described. The requirements on the Non-RT RIC framework and rApp are collected for the future specification of the Non-RT RIC functional architecture. Version 1.01 adds service-based view of non-RT RIC architecture and functionalities and enhances the AI/ML functionalities.
This document provides details on AI/ML lifecycle management including model design, composition, and model runtime access to data and the model deployment solutions. Criteria for determining various ML training host and ML inference host deployment options is highlighted. It also elaborates on AI/ML models used in O-RAN use cases aligned with the WG1-Use Case Task Group work effort.
Version 03.01 separates the OpenAPI aspects of the A1 interface from the Policy and Enrichment Information data models. The OpenAPI specification remains in the A1AP, and the data models are moved to a new specification, A1 interface Type Definitions.
This document specifies the transport protocol of the A1 interface. Version 01.01 clarifies the default port number to be used for the A1 interface and adds some editorial improvements.
Version 02.02 adds a lot of editorial improvements and a definition of the life cycle of A1 policies.
This new specification defines the data types for A1 Policies and A1 Enrichment Information in a reusable and extensible way. It allows new policy types to be created independently of the generic application protocol parts. The policy types that were previously defined in A1 interface Application Protocol specification are now included in this specification.
The document describes the internal architecture of O-RAN Near-Real-Time RAN Intelligent Controller (Near-RT RIC) from a functional perspective, including the general principles, requirements, basic functions and Near-RT RIC API. This version introduces API procedures stage-2 definition, including A1 related API, E2 related API, management API, SDL API and enablement API.
This document describes O-RAN Open Fronthaul M-Plane Specification, which defines the Management Plane of the Open Fronthaul Interface as well as the associated YANG models. This specific version is v06.00 in which there are several clarifications and a few new capabilities, most significantly support for Netconf/TLS and IPv6-only O-RUs.
This document describes O-RAN Open Fronthaul CTI TC-Plane Specification, which defines an interface between the O-DU and a PON or DOCSIS Transport Node (TN) to enable fronthaul traffic to transit what would otherwise be a too-high-latency network. This version adds several clarifications and a few new capabilities, including the handling of UL C-Plane traffic (used for LAA) and support for pattern normalization.
This document describes O-RAN Open Fronthaul Conformance Test Specification, which defines conformance tests of the Open Fronthaul Interface. This version adds a few new test capabilities including O-DU Synchronization tests.
This document describes O-RAN Open Fronthaul CUS-Plane Specification, which defines the Control Plane, User Plane and Synchronization Plane of the Open Fronthaul Interface. This version adds several clarifications and a few new capabilities, most significantly special provisions for sending SRS from O-RU to O-DU in an efficient manner.
This document describes O-RAN Open Fronthaul CTI TM-Plane Specification, which defines an interface between the O-DU and a PON or DOCSIS Transport Node (TN) to enable fronthaul traffic to transit what would otherwise be a too-high-latency network. This version adds several clarifications and a few new capabilities, including enhancements for the handling of C-Plane traffic and support for pattern normalization.
This document describes O-RAN Open Fronthaul IOT Specification, which defines tests to validate the ability for O-DU and O-RU equipment to operate together using the the Open Fronthaul Interface. This version adds several clarifications and a few new capabilities, most significantly a new set of IOT Profiles covering the mMIMO use case.
This document specifies Inter-operability tests for RAN Node from different vendors implemented in accordance to the WG5 C-plane and U-plane profiles. This version focuses on:
This version further introduces:
The scope of U-Plane profile specification is to further clarify (i.e. profile) the expected behavior for each RAN node (still within the scope of the 3GPP specifications), e.g. usage of IEs for each use case, general behavior of each node, etc. The document contains profiles of X2/F1/Xn U-Plane procedure for EN-DC use cases, NR-SA use cases and NR-DC use cases. This version mainly introduces updates of the existing use cases to follow the latest 3GPP specs.
The scope of C-Plane profile specification is to further clarify (i.e. profile) the expected behavior for each RAN node (still within the scope of the 3GPP specifications), e.g. usage of IEs for each use case, general behavior of each node, etc. The document contains profiles of X2/F1/Xn C-Plane procedure for EN-DC use cases, NR-SA use cases and NR-DC use cases. This version of the C-Plane profile spec mainly introduces:
This specification describes one white box hardware reference design example for indoor deployments. This version covers:
This version of the specification is compliant to Indoor Picocell Hardware Architecture and Requirement (FR1 Only) v01.00.
This document specifies system requirements and high-level architecture for the Outdoor Micro Cell for FR1 deployment scenario as specified in the Deployment Scenarios and Base Station Classes document and Microcell Hardware Architecture and Requirement (FR1 Only).
This specification describes one white box hardware reference design example for indoor deployments. In this version you will find:
This version of the specification is compliant to Indoor Picocell Hardware Architecture and Requirement (FR1 Only) v01.00.
This document specifies system requirements and high-level architecture for the Outdoor Micro Cell deployment scenario case as specified in the Deployment Scenarios and Base Station Classes document.
This document specifies a hardware reference design for the fronthaul gateway. The fronthaul gateway can be used to terminate O-RAN fronthaul user, control, synchronization, and management planes for option 7-2x and to translate the signals to and from a number of CPRI interfaces (option 8). It can further multiplex or demultiplex option 7-2x fronthaul signals to or from a number of O-RUs. This version of the specification only supports option 7-2x to option 8 conversion and vice versa in addition to the transport of other traffic streams.
This document specifies system requirements and high-level architecture for the Outdoor Macrocell deployment scenario case as specified in the Deployment Scenarios and Base Station Classes document (V2).
This document is intended to describe best practices for O-RAN Architecture and Solution for X-haul timing & synchronization. Beyond the solutions described in this document, other Architectures and Solutions may be adequate for X-haul timing & synchronization and can be considered in future versions of this document.
This specification describes best practices for O-RAN transport Network Element (TNE) management interfaces. Beyond the solutions described in this document, other management solutions may be adequate for transport network element management and can be considered in future versions of this document. In this version, first generic requirements are given for these interfaces with more specific technology-related recommendations.
This document specifies the O-RAN Security Threat Modeling and Remediation Analysis. It identifies assets to be protected, analyzes the O-RAN components for vulnerabilities, examines potential threats associated with those vulnerabilities and provides security principles, which stakeholders should address when building a secure end-to-end O-RAN system.
This document specifies Secure Shell (SSH) and Transport Layer Security (TLS) to be used for O-RAN implementations.
This test specification is focused on validating the end-to-end system functionality, performance, and key features of the O-RAN system as a black box.
This document describes the certification and badging processes and associated detail technical procedures for the Open Testing and Integration Centres (OTIC) and various other testing entities.
Co-chair of the O-RAN ALLIANCE’s Technical Steering Committee,
Member of O-RAN Executive Committee,
Chief Scientist of China Mobile.
Chih-Lin I has been a distinguished expert with nearly 40 years of rich experience in wireless communications. She is a key proponent of ICDT convergence for future wireless networks. She proposed 5G being “Green and Soft” from the first day of 5G design. The philosophy continuously evolved and embraced “Open and Smart” later on, which laid out the foundation for O-RAN.
Co-chair of the O-RAN ALLIANCE’s Technical Steering Committee,
Professor of EE & CS at Stanford University.
Sachin Katti is also Co-Founder and ex-CEO of Uhana (now part of VMware), as well as previously co-founder of Kumu Networks, which is commercializing breakthrough research from his lab on full duplex radios. He received his PhD in EECS from MIT in 2009. His research has won numerous awards, including the 2008 ACM Doctoral Dissertation Award - Honorable Mention, the George Sprowls Award for Best Doctoral Dissertation in EECS at MIT, the IEEE William Bennett Prize, and the Best Student Paper Award at ACM SIGCOMM 2012.
