Understanding Open Radio Access Network (O-RAN) From The Basics

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Cellular networks have evolved and transformed in the last two decades to accommodate various technological innovations whether it be for 2G to 3G to 4G. The global telecom networks are now gradually heading towards 5G. For this, the networks will have to evolve accordingly. From closed traditional networks they will now transcend towards open radio networks, better known as open radio access networks (O-RAN). The concept of O-RAN (Open RAN) is used for more open radio access network architecture than provided today by telcos.

To understand Open RAN, let us first have a high-level understanding of how networks work and how they have transformed in these years.

In this article, we look at various discussion points related to O-RAN:

  • What is Open RAN (O-RAN)?
  • O-RAN Terminologies
  • How is O-RAN Beneficial?
  • The O-RAN Architecture
  • Key components of O-RAN (Open RAN)
  • O-RAN Implementation
  • FAQs

What is Open RAN (O-RAN)?

O-RAN (Open RAN) is a term used for industry-wide standards for RAN (Radio Access Network) interfaces that support interoperation between vendors’ equipment and offer network flexibility at a lower cost.  The main purpose of open RAN is to have an interoperability standard for RAN elements including non-proprietary white box hardware and software from different vendors. Network operators that opt for RAN elements with standard interfaces can avoid being stuck with one vendor’s proprietary hardware and software.

The Open RAN standards aim to change the siloed nature of the RAN market, where a bunch of RAN vendors only offer equipment and software that is totally proprietary. This reduces flexibility and interoperability

The open RAN standards are being developed using virtual RAN (vRAN) principles and technologies. The reason is simple; vRAN comes equipped with features such as network malleability, improved security, and reduced capex and opex costs.

O-RAN Terminologies

As the equipment manufacturers enhanced the capabilities, so the industry consolidated around those with the strongest offer and often proprietary functionality. But operators today want a more diverse ecosystem of vendors and are redefining their requirements for the network architecture, especially in the RAN. 

Let us see some of the wisely used O-RAN terminologies:

O-RAN (with the hyphen) refers to the O-RAN Alliance, which publishes new RAN specifications, releases open software for the RAN, and supports its members in the integration and testing of their implementations. 

“ORAN” can also be used to refer to the Open RAN movement; however, O-RAN with the hyphen always refers to the O-RAN Alliance. #oRAN or #ORAN are also used as hashtags on social networks to refer to either the O-RAN Alliance or to the Open RAN movement.

Cloud RAN is a virtualised RAN designed to be cloud-native. It is built in a future-proof architecture and incorporates key elements such as microservices and containerization.

An Open RAN is disaggregated into three main building blocks:

  • Radio Unit (RU)
  • Distributed Unit (DU)
  • Centralised Unit (CU)

The RU is where the radio frequency signals are transmitted, received, amplified, and digitized. The RU is located near or integrated into, the antenna. The DU and CU are the computation parts of the base station, sending the digitalized radio signal into the network. The DU is physically located at or near the RU whereas the CU can be located nearer the Core.

How is O-RAN Beneficial?

The advantages of O-RAN (Open RAN) are manifold. An open environment means an expanded ecosystem, with more vendors providing the building blocks. In O-RAN, there is more innovation and more options for the operators. They can also add new services.

Some of the other benefits include more market competition and customer choice, lower equipment costs, and improved network performance.

Radio Access Network vendors only offer proprietary equipment and network functions. This is the main reason organizations began developing open RAN standards to break out of that legacy.

Proprietary products are typically more expensive than generic counterparts. Because there aren’t third-party RAN elements that can integrate into a RAN vendors’ infrastructure, a network operator is stuck with one RAN vendor’s products.

In an Open interface, third-party products can communicate with the main RAN vendor’s infrastructure. Network operators can also opt for the less-expensive third-party product that operates on generic hardware. As network operators look to transition to vRAN architecture for 5G, using open RAN interfaces can reduce the cost of deploying this new technology. When 5G technology advances and changes, network administrators working with open standard-based vRANs can easily send updates to the network infrastructure to accommodate for the changes.

The O-RAN Architecture

The O-RAN architecture is well documented in the O-RAN alliance. The key elements of O-RAN architecture are:

  • Service Management and Orchestration Framework (SMO) – includes an integration fabric and data services for the functions it manages. It allows managed functions to interoperate and communicate within the O-RAN. The 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 the E2 interface. The E2 interface connects the near-real-time RIC with the O-CU and O-DU
  • O-Cloud – a cloud computing platform made up of the physical infrastructure nodes using 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) – 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).
  • 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.

Key components of O-RAN (Open RAN)

The key components of O-RAN are:

Cloudification – It involves hardware and software disaggregation.  Use RAN applications as cloud-native functions.

Intelligence and automation – It uses open management and orchestration with external AI/ML capabilities.

Open internal RAN interfaces – It includes interfaces defined by 3GPP.

O-RAN Implementation

This is true that ORAN is enabling exciting new opportunities in radio access networks. But operators need to think about network security before implementing O-RAN.  A secure, modern cloud-native implementation of ORAN would rely on securing the underlying microservices-based architecture.

The O-RAN Alliance only provides functional compliance to the specifications of components. For implementation, the prime requirement of stakeholders is verification, integration, interoperability, and testing of the commoditized RAN components. This all is required to support a plug-n-play model. Therefore, commoditization of services is not enough; efficient orchestration of the different components is necessary to guarantee stable networks.


  • What does O-RAN mean?

Open radio access network (RAN) is a term for industry-wide standards for RAN interfaces that support interoperation between vendors’ equipment. The main purpose for using open RAN is to have an interoperability standard for RAN elements like non-proprietary white box hardware and software from different vendors.

  • What is open RAN architecture?

OpenRAN Is an Alternative Way of Building Networks that Promises Greater Interoperability and More Competition. … In a traditional RAN, hardware components and software code are tightly coupled, and interfaces do not support interoperability between different vendors.

  • What is 5G RAN?

5G RAN is a set of virtualized networking technologies with advanced capabilities. The radio spectrum used by 5G networks covers more radio frequencies than 4G LTE networks.

  • What is RAN intelligence controller?

RIC is a cloud-native architecture and is at the heart of an open and virtualized RAN network. It specifies near real-time control functionalities and enables RAN (Radio Access Network) slicing, QoS control, enhanced/novel RRM, etc.

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