Developing Radio Access Network (RAN) infrastructure for mobile networks has always been a challenge for smaller players, due to the amount of upfront investment required. Most solutions deployed today use proprietary hardware and interfaces, meaning it is not possible to develop a small subset of the RAN.  As a result, it is extremely difficult for an operator to use multiple vendors within the same geography for any single generation of mobile technology.  In practical terms this means that one vendor can be used for 3G and another for 4G but when it comes to 5G networks – most of which today are non standalone – the vendor providing 4G in a particular geography will need to be used for 5G also.  This can of course change when operators move to standalone 5G networks. 

Open RAN is a movement that looks to address this, encouraging open interfaces to overcome vendor ‘lock-in’. The ultimate aim is to allow operators to mix and match vendor solutions, giving them the freedom to choose the most appropriate vendor for any deployment scenario.

Open RAN is being championed by many different organisations but the two most prominent are the Telecom Infra Project (TIP) and the O-RAN Alliance.

The O-RAN Alliance is involved in creating specifications, open source RAN software based on O-RAN specifications and the integration and testing of O-RAN based software implementation. All O-RAN based network components are labelled with ‘O-’ to highlight their compliance with O-RAN specifications. O-RAN Alliance identifies its mission as "to re-shape the RAN industry towards more intelligent, open, virtualized and fully interoperable mobile networks. O-RAN specifications enable a more competitive and vibrant RAN supplier ecosystem with faster innovation to improve user experience. O-RAN based mobile networks improve the efficiency of RAN deployments as well as operations by the mobile operators".

TIP has various groups, one of which is dedicated to Open RAN and is called OpenRAN (without the space between ‘Open’ and ‘RAN’). TIP OpenRAN's stated mission is to: "accelerate innovation and commercialization in RAN domain with multi-vendor interoperable products and solutions that are easy to integrate in the operator’s network and are verified for different deployment scenarios. TIP’s OpenRAN program supports the development of disaggregated and interoperable 2G/3G/4G/5G NR Radio Access Network (RAN) solutions based on service provider requirements".

It should be highlighted here that all organisations involved in championing Open RAN, including TIP, work closely with the O-RAN alliance, which is the de facto organisation for the final say in 4G/5G Open RAN standards.

O-RAN Alliance Work Groups (WGs) focus on creating O-RAN specific architecture, use cases and specification documents as well as providing fully operable multi-vendor profile specifications compliant with 3GPP interface specifications. The Standard Development Focus Group (SDFG) within the O-RAN Alliance plays the leading role in defining standardisation strategies and is the main interface to 3GPP and other Standard Development Organizations (SDOs) that are relevant for O-RAN work.

Another technology often used along with Open RAN is Network Functions Virtualisation (NFV), which allows custom-built hardware to be replaced by software running on commercial off-the-shelf (COTS) hardware. The end result is a Virtualized RAN (vRAN).

Custom built hardware typically uses a single purpose processor (SPP), optimised to handle specific functions and/or algorithms. In contrast, COTS hardware uses a general purpose processor (GPP).

Traditionally, SPPs were far superior to using GPPs but we are reaching an inflection point in processor technology where GPPs are now fast enough to handle the same amount of compute in software. Making virtualized RANs a viable option.

There are therefore various types of RAN now available:

1. Open but not Virtualized - referred to as Open RAN
2. Virtualized but not Open - referred to as vRAN
3. Both Open and Virtualized - referred to as Open vRAN

Open RAN is expected to be a catalyst for supply chain diversification in the mobile networks. Virtualization on the other hand enables disaggregation of hardware and software and is expected to allow new vendors to bring their specialist expertise into the mobile network ecosystem. In addition, softwarisation provides a far lower barrier for new entrants into the development of specific functions or algorithms in the mobile network.

The UK has an active ecosystem for products and services supporting mobile network diversification and open networks.  This ecosystem is active throughout the three key phases of taking new technology from concept to commercial deployment. 

In this part of our site we highlight UK activities in open networks across the technology readiness levels (TRLs):

• Open RAN research and development: early technology readiness levels
• Testing and interoperability: mid technology readiness levels - pre commercial products and deployments
• Open RAN products, services and deployments: high technology readiness levels - commercial products and deployments