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An Introduction To OpenRAN (ORAN)

April 07, 2021


Operator-defined Open and Intelligent Radio Access Networks, abbreviated as OpenRAN/ORAN, is the movement in mobile networks and telecommunications to improve the efficiency of RAN deployments and operations. According to Nokia, OpenRAN has been touted as the ‘next big thing in wireless’, after Massive MIMO, beamforming, 5GNR (New Radio), Dynamic Spectrum Sharing (DSS), and the use of Artificial Intelligence (AI) and Machine Learning (ML) in RAN.

According to the O-RAN Alliance, the OpenRAN architecture, empowered by intelligence and openness principles, is the foundation for building the virtualized RAN on open hardware and cloud, with embedded AI-powered radio control. The architecture is based on standards defined by O-RAN Alliance, which completely support and are complementary to standards promoted by 3GPP and other industry standards organizations.

OpenRAN introduces many advantages to the enterprise telecom market, including infrastructure reconfigurability & flexibility, scalability, frequent and early deployments, higher network sustainability, and CAPEX/OPEX efficiency. 

OpenRAN-ORAN-Overview

The O-RAN Alliance:

The O-RAN Alliance is a group of organizations facilitating specifications for radio access networks. The foundation of the alliance was laid in the year 2018 with close to 30 operators and more than 200 vendor companies. The goals of the global alliance are to provide strategies to build the RAN solution enabling different COTS parts from different vendors with enabling artificial intelligence and machine learning for more efficient network management and orchestration.

O-RAN ALLIANCE is transforming the Radio Access Networks industry towards open, intelligent, virtualized, and fully interoperable RAN. The O-RAN ALLIANCE membership is open to mobile operators, vendors, or research and academic institutions that want to contribute in a meaningful way to the O-RAN ALLIANCE’s effort.

OpenRAN Market Size:

According to a report by ABI Research, the capital expenditure on OpenRAN radio units is expected to reach $47.4 billion by 2026. ABI Research expects greenfield installations and private enterprise networks, and public consumer networks in rural/uncovered areas to drive OpenRAN deployment throughout the entire forecast period.

Omdia, another research firm, reports ORAN likely to generate about $3.2 billion in annual revenues by 2024, giving it about 9.4% of the total 4G and 5G market.

OpenRAN-ORAN-Market-Size

OpenRAN Components & Functional Splits:

In a 5G cloud RAN architecture, the Baseband unit (BBU) is split into two functional units, namely:

  1. Distributed unit (DU): It is responsible for real-time L1 and L2 scheduling functions.
  2. Centralized unit (CU): This unit is responsible for non-real-time, higher L2, and L3.

OpenRAN-ORAN- Architecture

The OpenRAN concept utilizes vendor-agnostic COTS-based servers for DU and CU software to Radio Unit (RU). Let us understand the components of OpenRAN architecture:

  • Service Management and Orchestration Framework (SMO): The SMO includes integrating fabric and data services for the managed functions. It connects to and manages the RICs, O-Cloud, the O-CU, and O-DU.
  • Non-Real Time RIC (RAN Intelligence controller): This function supports intelligent RAN optimization in non-real-time (i.e., greater than one second) by providing policy-based guidance using data analytics and Artificial Intelligence /Machine Learning training/inference. Non-RT RIC can use SMO services such as data collection and provisioning services of the O-RAN nodes.
  • Near-Real-Time RIC: This function enables near real-time control and optimization of the O-RAN (O-CU and O-DU) nodes and resources over the E2 interface with near real-time control loops (i.e., 10ms to 1s). The Near-RT RIC uses commands such as monitor, suspend/stop, override, and/or control primitives to control the behavior of the O-RAN nodes.
  • O-RAN Centralized Unit (O-CU): Centralized unit that runs the Radio Resource Control (RRC), Packet Data Convergence Protocol (PDCP), and Service Data Adaption Protocol (SDAP) layers. The CU controls the operation of several DUs over the mid-haul interface.
  • O-RAN Distributed Unit (O-DU): A distributed unit that sits close to the Radio Unit (RU) and runs the Radio Link Control (RLC), Medium Access Control (MAC), and parts of the PHY layer (High PHY). The Centralized Unit controls its operation (CU).
  • O-RAN Radio Unit (O-RU): Radio unit which handles the digital front end (DFE) and the parts of the Physical (PHY) layer (Low PHY), as well as the digital beamforming functionality.
  • O-Cloud: The O-Cloud works like a cloud computing platform with physical infrastructure nodes using Open RAN architecture. It creates & hosts various virtual network functions (VNFs) used by the RICs and other elements.

OpenRAN promises horizontal openness – with open interfaces enabling functions of the RAN to connect with other functions: Radio unit (RU), Baseband (DU-CU), CU & the NMS/orchestrator.

How will OpenRAN Transform 5G:

5G is more than RF, RAN, and Core. Machine Learning (ML) & Artificial intelligence (AI), Virtualization, Software-defined networks (SDN), Edge Computing, Management & Orchestration, etc., all contribute as the critical components in 5G.

Machine Learning & Artificial Intelligence powers the policies & rules, making them more adaptive than ever. Virtualization & SDN powers the flexibility of using COTS hardware. Edge computing gives the flexibility of deploying RAN components & network functions close to last-mile connectivity. With the introduction of microservices-based architecture and network functions distributed over different cloud/private infrastructures, the management & orchestration of the 5G networks is quite different than its previous generations.

OpenRAN is about openness and intelligence. It is about opening RAN from a closed vendor environment to a standardized multi-vendor, AI-powered hierarchical controller structure giving third-party vendor access to what used to be closed RAN data.

Traditionally ISPs were dependent on a single vendor to provide the complete RAN system. OpenRAN is bringing in the flexibility for operators to choose different components of RAN from different vendors. For example, a combination of O-CU from Vendor A, O-DU from Vendor B & O-RU from Vendor C would work seamlessly in OpenRAN architecture.

OpenRAN is revolutionizing & paving the way for transforming 5G deployment. While there will be no significant change with regards to core protocol or standard, OpenRAN would help in the adoption of innovative use cases with the architecture and openness that it provides.

Benefits of OpenRAN:

OpenRAN brings in a lot of horizontal and vertical flexibility within the network, which is advantageous for the ISPs and telecom vendors. Some of the benefits of OpenRAN are:

  • No dependency on closely coupled hardware & software, which was a significant constraint for telecom vendors in deployment.
  • Simplified operation & maintenance of OpenRAN, as the hardware under-use is standardized, and the software can run on general-purpose hardware.
  • Helps in reducing CAPEX & OPEX requirements, thanks to competition across vendors providing hardware & software.
  • With the enablement of edge-centric architecture, 5G will move towards achieving low latency and provide better connectivity in high population/dense areas.
  • With microservices-based & loosely coupled architectures, deployment of new features can be fast-tracked.
  • OpenRAN provides an opportunity for early adoption and easy roll-out of 5G services.
  • OpenRAN will also enable easy scalability, thanks to the rapid advancements in computing.
  • OpenRAN will also help early adoption of various industry use case which were difficult (due to higher CAPEX/OPEX) in the closely coupled architecture of 4G or 5G networks.

Challenges with OpenRAN:

  • The main challenge in OpenRAN standardization is that the major RAN vendors are not open to adopting interfaces, leaving little to no room for competitors to break into the space
  • The multi-vendor approach proposed in OpenRAN will create increased complexity and difficulties in maintaining system integration.
  • A number of organizations are working towards OpenRAN standards, and the adoption of one particular standard creates competition between organizations. 
  • Ownership of System integration & binding modules from multiple vendors in one integrated system creates a tussle between parties on the ownership front.

Conclusion:

OpenRAN is about bringing openness and intelligence into the system. It is about lowering CAPEX/OPEX for vendors, bringing in greater innovation through competition, and allowing MNOs to avoid restricted vendors. Enthusiasm around OpenRAN has been mixed as the industry is skeptical about its broader adoption, challenges with system integration, and benefits provided by OpenRAN architecture. With new players entering the telecom market and MNOs looking to develop homegrown sub-systems, there are discussions around possible use cases that can be implemented with technological evolution within 5G. OpenRAN is expected to pave the path for greater innovation and early deployment of 5G.






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