OpenRAN and O-RAN ,Simplified!

As on today, Mobile devices have outnumbered laptops and desktops and their number continues to grow, currently while 5G being rollout in the country the trend continues to witness large scale adoption and convergence of voice, video and data on mobile devices in the current decade, adding to it will be the penetration of Private 5G networks broadening the horizon while connecting the IoT for M2M communication well within the remote corners of the country.

According to a?recent report ?from IDC, the Private LTE/5G infrastructure market is forecast to grow from $945 million in 2019 to over $5.7 billion by 2024.

Next generation of cellular technology like 6G networks is expected to be even more diverse, faster ( Over 100Gbps peak data rate) ?and are likely to support applications beyond current use scenarios enabling emerging technologies like AR/VR, IoT, context awareness , pervasive / ambient intelligence etc possible.

What is OpenRAN, O-RAN and why it is important?

Typically today’s cellular network is divided into two parts, Core Network and Radio Access Network (RAN) wherein the core network is responsible for access control, billing, routing and interconnect with external networks, wherein RAN is the responsible to connect the users with core, and often acts as a base station. The Radio Access Network, i.e RAN is a technology that connects individual devices to other parts of a network through radio as wireless connections. It is a major part of modern telecommunications and cellular networks, with LTE and 5G being examples of such radio access networks.

As the complexity and technologies emerge so are the number of players contributing to the innovation at different parts of the cellular technology value chain. Typically RAN comprises of antennas, radios called RU’s and other key modules called Centralized Unit and Distribution unit i.e. CU and DU respectively. These modules often work in a closed loop and well-integrated by the OEM known as Functional splits and was outlined in 3GPP Release 14 and defined in 3GPP release 15 where new terminology, interfaces and functional modules were introduced, this split architecture between CU and DU allows for coordination for performance optimization, load management to enable adaptation to various use cases and the QoS ( Read, Quality of Service) that needs to be supported (i.e. gaming, voice, video on the end device.

There are two dominant Open RAN standardization bodies,?The Telecom Infra Project (TIP) and the O-RAN Alliance . However, they are not the entirety of the open RAN standards movement since the general goals of creating open RAN standards are to bring new vendors into the RAN market and to give other options to single-vendor solutions. It further opens up the working protocols and API interfaces and help the telecom operator deploy a fully compliant functional split architecture and seamlessly interconnect the interfaces between RU, DU and CU from various OEMs to expand the ecosystem and add, modify and deliver new features as they evolve.

The idea of an OpenRAN driven by TIP , is an open ecosystem of GPP-based RAN solutions focusing on implementation of RAN solutions that can be deployed on General Purpose Processing Platforms. Fundamentally in Open RAN, the Radio units i.e. RU’s connectivity to Distribution units, DU’s and is called front-haul, many DU’s are further connected to Centralized units, CU’s and is called Mid-haul. The function of CU’s is to connect with core and help establish seamless connections (called back-haul) by an between the user and the network. i.e. core thus enabling a sustainable development stream define a reference framework/software architecture that decomposes LTE eNB into individual blocks and components.

Whereas O-RAN Alliance , a worldwide community of around 200+ mobile operators, vendors, and research & academic institutions operating in the Radio Access Network (RAN) industry collectively defining next-generation O-RAN infrastructures, empowered by principles of intelligence and openness to re-shape the industry eco-system towards more intelligent, virtualized network elements, white-box hardware, and standardized and open interfaces. There are eleven working groups focusing on different objective under the unified O-RAN development vision. Operators get benefited leveraging their network assets and harness the “cloud” to modernize and future-proof their networks making them interoperable, automated, and thus easy to maintain and support network growth, technology refreshes etc with flexibility.

From infrastructure deployment architecture perspective of RAN, there are four key approaches, they are D-RAN, C-RAN, vRAN and O-RAN. The D-RAN and C-RAN being erstwhile approaches of distributed vs centralized placement. D-RAN as a classical setup in which RRU (Remote?Radio ?Unit) and?BBU ?(Baseband Unit) are co-located at every cell site. Whereas, In C-RAN the BBUs from several sites are grouped into a pool?and located in one location. They both run proprietary applications on specialized hardware at each radio site with all of its functions are in a single location as a pre-integrated proprietary setup.

There is a close yet definitive progression between V-RAN and O-RAN as the above figure illustrates. vRAN, i.e. Virtualized Radio Access Network is not the same as Open RAN or O-RAN, it can be deployed in conjunction and makes the RAN much more flexible leveraging virtualization. What was done in hardware can now be done in software which reduces entry barriers into the market. The DU and CU are effectively run as software than the devices, called NFV’s i.e. Network Function Virtualization. Instead of using custom hardware, they can now be virtualized and run on any Cloud, as long as it is near the base station to reduce latency and runs on bespoke hardware to ensure feature parity and facilitates maintenance of the releases.?

Both V-RAN and O-RAN have established mainstream usecases but with a major difference that v-RAN uses proprietary interfaces whereas O-RAN uses open interfaces making the O-RAN stack open and multi-vendor, i.e. allows the software in cellular radios to be run anywhere on common off-the-shelf (COTS) hardware such as those based on Intel x86 and ARM architectures. O-RAN further enable a multi-vendor approach with definitive standards for interoperability between different NFVs bringing in flexibility of deployment and uses the?radio interface controller (RIC) providing more dynamic control of the elements like the scheduler, which is probably the most important part of the RAN in terms of slicing and scheduling all the traffic onto the various data channels. O-RAN Networks can deploy one scheduler per user and deliver QoS that will never be possible in the hardware-based solutions.

O-RAN Architecture

The O-RAN architecture and interface specifications are to be consistent with 3GPP architecture and interface specifications to the extent possible, and comprises of SMO, RIC, O-Cloud, O-CU, O-DU and O-RU as the key elements..

• Service Management and Orchestration Framework (SMO)—that includes the integration fabric & the data services for the NFV functions to interoperate and communicate within the O-RAN. Overall SMO connects to and manages the RICs, O-Cloud, the O-CU, and O-DU.
• RAN Intelligent Controller (RIC) – There are two types of RICs – non-real-time and near-real-time. Both are logical functions for controlling and optimizing the elements and resources of an O-RAN. A near-real-time RIC controls and optimizes elements and resources with granular data collection and communication over identified E2 interface that further connects the near-real-time RIC with the O-CU and O-DU.
• O-Cloud is a cloud computing platform made up of the physical infrastructure nodes using the O-RAN architecture. It also creates and hosts the various virtual network functions (VNFs) used by the RICs and other infrastructure elements.
• O-RAN central unit (O-CU) – Logical node that hosts a handful of protocols, which are the radio resource control (RRC), service data adaptation protocol (SDAP), and packet data convergence protocol (PDCP).
• O-RAN distributed unit (O-DU) is a logical node that hosts another set of protocols, which are the radio link control (RLC) protocol, medium access control (MAC) protocol, and the physical interface (PHY). The RAN DU sits between the O-RU and O-CU and performs real-time L2 functions, baseband processing.
• O-RAN Radio unit (O-RU) – It processes radio frequencies received by the physical layer of the network. The processed radio frequencies are sent to the O-DU through a front haul interface.

This split architecture helps operators scaling dimensions to support 4G/5G use cases and traffic structures in a cost-efficient way due to Its flexibility and decoupling of hardware from software it enables a software-defined elastic resilient and future-proof RAN in line with business needs fostering the open ecosystem to overcome vendor lock-in, enabling increased speed, scalability and lays the firm foundation of automation and virtualized network elements for futureproofing the investment.

Although successful design, implementation and operation of disaggregated RAN network will depend on the ability of operator to integrate system components and meet the target network key performance indicators (KPIs) within the multi-vendor environment and instil the confidence that all components in the O-RAN network have been pre-validated, well-integrated and verified as a trusted and controlled environment with all open interfaces and components working in tandem, so that network performance is at par to that of a single-vendor network.

The Future of RAN

The future evolution of RAN will leverage dynamic functional splits. While the OpenRAN Controller (aggregator) acts as a mediator between the RAN and core network, the functionality of the RAN will be distributed between DUs and CUs as it is defined in 5G, and this software can be co-located with the aggregator. In different scenarios, these elements can collapse together and create a single physical entity with different virtual functionalities by leveraging virtualization coupled with open/standard interfaces to have a much more flexible, multi-vendor network with a broader array of features. TIP OpenRAN seems aligning with O-RAN since O-RAN Alliance will continue to drive the next generation RAN to new levels of openness, efficiency, flexibility, and intelligence using reference designs, open interfaces, virtualization, open source and white box elements with more software driven components.

O-RAN is much focused on 4G/5G there are streams of thoughts around sustainability of the Alliances as compared with 3GPP In particular, citing a report of the European Commission could not determine whether the O-RAN Alliance was complying with various WTO criteria, including cybersecurity , etc. Thus the future of O-RAN will be in the discipline of design, deployment and execution of the standards by O-RAN Alliance to overcome Integrating and ongoing management of the complexities of validating the interoperability, Orchestration and Accountability for issue resolution of the multi-vendor RAN components without compromising on network performance comparable to an optimized single vendor solution, having said that it is good to see that U.S. House of Representatives?recently passed ?a bill to dedicate $750 million funding over the next decade to support the development of Open RAN solutions. What say?

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Nov 2022. Compilation from various publicly available internet sources, authors views are personal.

#openran #5G #3gpp #telecom #nfv #vran #VNFs #lte #oran #edgecomputing