While many RAN organisations are loosely interconnected, some are formally structured and set distinct RAN standards. Tremendous progress in RAN development and innovation has been witnessed recently. This page explains a number of commonly used terms in the RAN domain, such as Open RAN, O-RAN, V-RAN, etc.
vRAN:
Numerous terms and acronyms, including as vRAN, open RAN, O-RAN, and others, are associated with the development of RAN. It is important to make clear that RAN evolution includes both the introduction of cloud technology to facilitate automated deployment and scaling as well as the optimization of workload placement. The disaggregation of mobile network base stations into more standardized entities is commonly referred to as functional split.
Virtualization of RAN technology does not make sure that it follow the O-RAN framework but it simply mean that the vendor has virtualized its RAN components, such as the baseband unit, gNB, eNodeB, distributed unit (DU), and central unit (CU). Virtualization of RAN also does not make sure the compatibility with other vendor RAN technology and cannot mix and match these components from other vendors. The term virtual does not refer to term open and also not guarantee about its openness in term of code, interface, API etc.
O-RAN Alliance:
3GPP initially proposed split RAN architecture to satisfy URLLC (Ultra Reliable Low Latency Communication) and eMBB (Enhanced Mobile Broadband) needs. The O-Ran Alliance, which was founded by telecom carriers and CSPs, is the key organization responsible for creating open interfaces for split RAN architecture. It has a large number of members from the CSP and vendor communities. O-RAN is defining or clarifying the use of interfaces between networks:
A logical Architecture of O-RAN:
A1 interface: A1 is the interface between the Non-RT RIC in Service Management and Orchestration and the Near-RT RIC function O-RAN Network function. A1 interface supports three types of services:
• Policy Management Service
• Enrichment Information Service
• ML Model Management Service
E2 Interface: E2 is a logical interface connecting the Near-RT RIC with an E2 Node:
• An E2 Node is connected to only one Near-RT RIC.
• A Near-RT RIC can be connected to multiple E2 Nodes.
E1 Interface: The E1 interface, as defined by 3GPP, is between the gNB-CU-CP and gNB-CU-UP logical nodes. In O-RAN, it reuses the principles and protocol stack defined by 3GPP but is adopted between the O-CU-CP and the O-CU-UP logical nodes.
F1 interface:
F1-c Interface: The F1-c interface, as defined by 3GPP, is between the gNB-CU-CP and gNB-DU logical nodes. In O-RAN, it reuses the principles and protocol stack defined by 3GPP but is adopted between the O-CU-CP and the O-DU logical nodes, as well as for the definition of interoperability profile specifications.
F1-u Interface: The F1-u interface, as defined by 3GPP, is between the gNB-CU-UP and gNB-DU logical nodes. In O-RAN, it reuses the principles and protocol stack defined by 3GPP but is adopted between the O-CU-UP and the O-DU logical nodes, as well as for the definition of interoperability profile specifications.
Open FrontHaul: The Open FH (Fronthaul) Interface is between O-DU and O-RU logical nodes [14] [18]. The Open FH Interface includes the CUS (Control User Synchronization) Plane and M (Management) Plane. In hybrid mode, the Open FH M-Plane interface connects the O-RU to the SMO for FCAPS functionality.
O2 Interface: The O2 interface is between the SMO and O-Cloud
O-RAN alliance Workgroups:
WG1: Use Cases and Overall Architecture Work Group
It has overall responsibility for the O-RAN Architecture and Use Cases. WG 1 identifies tasks to be completed within the scope of the Architecture and Use Cases and assigns Task Group leads to drive these tasks to completion while working across other O-RAN Work Groups.
WG2: The Non-Real-Time RAN Intelligent
Controller and A1 Interface Work Group
The primary goal of Non-RT RIC is to support Non-Real-Time intelligent radio resource management, higher layer procedure optimization, policy optimization in RAN, and providing AI/ML models to Near-RT RIC.
WG3: The Near-Real-Time RIC
and E2 Interface Work Group
The focus of this WG is to define an architecture based on Near-Real-Time Radio Intelligent Controller (Near-RT RIC), which enables near-real-time control and optimization of RAN elements and resources via fine-grained data collection and actions over E2 interface.
WG4: The Open Fronthaul Interfaces Work Group
The objective of this WG is to deliver truly open fronthaul interfaces, in which multi-vendor DU-RRU interoperability can be realized.
WG5: The Open F1/W1/E1/X2/Xn Interface Work Group
The objective of this WG is to provide fully operable multi-vendor profile specifications (which shall be compliant with 3GPP specification) for F1/W1/E1/X2/Xn interfaces and in some cases will propose 3GPP specification enhancements.
WG6: The Cloudification and Orchestration Work Group
The cloudification and orchestration WG seeks to drive the decoupling of RAN software from the underlying hardware platforms and to produce technology and reference designs that would allow commodity hardware platforms to be leveraged for all parts of a RAN deployment including the CU and the DU.
WG7: The White-box Hardware Work Group
The promotion of open reference design hardware is a potential way to reduce the cost of 5G deployment that will benefit both the operators and vendors. The objective of this Work Group is to specify and release a complete reference design to foster a decoupled software and hardware platform.
WG8: Stack Reference Design Work Group
The aim of this WG is to develop the software architecture, design, and release plan for the O-RAN Central Unit (O-CU) and O-RAN Distributed Unit (O-DU) based on O-RAN and 3GPP specifications for the NR protocol stack.
WG9: Open X-haul Transport Work Group
This WG focuses on the transport domain, consisting of transport equipment, physical media and control/management protocols associated with the transport network.
WG10: OAM Work Group
This WG is responsible for the OAM requirements, OAM architecture and the O1 interface.
WG11: Security Work Group
This WG focuses on security aspects of the open RAN ecosystem.
Telecom Infra Project (TIP)
TIP The Telecom Infra Project, led by Facebook, established OpenRAN with an objective similar to O-RAN. However, since its inception, O-RAN’s goals have evolved to the development of RAN systems based on general purpose vendor-neutral hardware and software-defined technologies.
The Telecom Infra Project (TIP) is a global community of companies and organizations working together to accelerate the development and deployment of open, disaggregated, and standards-based technology solutions that deliver the high quality connectivity that the world needs – now and in the decades to come.
The use of open computing hardware has recently received attention. TIP has been contributing to the O-RAN Alliance’s WG8. Furthermore, the O-RAN Alliance and TIP have organized plugfests throughout the world in August and September of 2020 to evaluate interfaces and open hardware components.
TIP also features Crowdcell, Open Fronthaul, Transport, and RAN Backhaul initiatives. Its purpose is to create an open solution/reference architecture. TIP OpenRAN does not establish new open RAN interfaces or specifications; rather, it accelerates adoption and deployments.
The Open RAN Policy Coalition:
The Open RAN Policy Coalition represents a group of companies formed to promote policies that will advance the adoption of open and interoperable solutions in the Radio Access Network (RAN) as a means to create innovation, spur competition and expand the supply chain for advanced wireless technologies including 5G.
Coalition members works for the standardizing or “opening” the protocols and interfaces between the various subcomponents (radios, hardware and software) in the RAN, and adaptation of environment where networks can be deployed with a more modular design without being dependent upon a single vendor.
Standardizing and developing open interfaces will allow service providers to ensure interoperability across different players and potentially lower the barrier to entry for new innovators.
The Open RAN policy coaliation works on the foundation that there are a variety of steps that policymakers can take to facilitate a vibrant marketplace of suppliers based upon open interfaces. To that end, the coalition will promote policies that:
- Support global development of open and interoperable wireless technologies.
- Signal government support for open and interoperable solutions.
- Use government procurement to support vendor diversity.
- Fund research and development.
- Remove barriers to 5G deployment.
- Avoid heavy-handed or prescriptive solutions.
