Inaugural event for the newly formed CW Mobile Networks SIG - Shared RAN – why not?

This new SIG has been formed from the Enhanced Mobile Broadband, Small Cell and Virtual Networks SIGs. It recognises the changing role of small cells and virtualisation in the design and development of enhanced mobile network infrastructure, with these technologies now increasingly underpinning innovations in mobile infrastructure.

In their inaugural event, the Mobile Networks SIG lived up to their remit of considering tradeoffs between spectrum, technology and topology for sustainable mobile infrastructure by asking:  “Shared RAN – why not?” The event explored why, despite the long-promoted cost, aesthetic and environmental benefits, shared RAN is not more widely deployed. This first event in a two-part series focused on shared RAN in locations with capacity-limited, high demand density (HDD) locations, with a second event examining sharing in rural, coverage-limited locations planned for November.

Mike Ferris of Dense Air shared his experience and observations of the different technical and commercial approaches to shared RAN being taken between the UK and US. He described in-building Distributed Antenna Systems (DAS) as the historical start point for many neutral hosts, and how this in-building market has changed from passive to more active sharing solutions, expanded into being applicable to outdoor environments. The pioneering role of the UK in developing of the Joint Operator Technical Specification (JOTS) was highlighted, noting its evolution to include Neutral Host In-building (NHIB), JOTS Rail and JOTS Neutral Host Outdoor (NHOD). Started in 1999, the JOTS family of specifications was presented as an impressive example of addressing the challenges and complexities of Mobile Network Operator (MNO) concerns around connecting to neutral host networks, particularly with a focus on security. Mike also highlighted the elegance of the JOTS-based specifications in terms of their scalability and ability to readily cope with more radio sites being added over time.

However, despite its benefits, JOTS has not been widely adopted and applied beyond the UK. Instead, countries like the US have used availability of shared spectrum – in the form of Citizens Broadband Radio Service (CBRS) – to provide Multi-Operator Core Network (MOCN) style neutral host solutions, as promoted by the OnGo Alliance. In the US model, MNOs may (and frequently do) specify different technical solutions to neutral hosts that don’t align across all participating MNOs. It also requires each MNO to pre-validate any solutions and upgrades proposed by neutral hosts – whereas under JOTS, this validation sits with the neutral host.

John Bretherick of Fujitsu then presented the network equipment vendor perspective of shared RAN and made the case of Open RAN as a key enabler for equipment portfolios supporting network sharing. He highlighted how the virtualised service-based architecture of 5G, combined with open interfaces from Open RAN, allows for more flexible and sharable equipment sets that can support migration from distributed RAN (D-RAN) to centralised RAN (C-RAN) as MNOs transition their deployment approaches. Opportunities for energy savings were also highlighted – via via equipment pooling and more intelligent network configuration and control enabled by open interfaces. John also highlighted Fujitsu’s new feature of extended fronthaul support in their equipment sets, which allows pooling of Distributed Unit (DU) equipment over a 50km, compared to the previous 30km maximum fronthaul distance.

Next, Alex Smith of Antevia Networks introduced shared cells and private networks as extra dimensions to the shared RAN conversation. He described Antevia’s O-RAN shared cell solution, which uses groups of low-cost small cells to create targeted zones of coverage and capacity in environments such as sports venues, without the complexity of detailed radio planning and targeted placement of radio sites associated with more traditional mobile installations.

Alex walked the audience through a deployment at Bath Rugby Club, which provided an enterprise grade private mobile network to support various match day operations – from medical teams and concession kiosks to security teams and press areas. He highlighted how such O-RAN based private networks could readily be expanded to include MNO public mobile layers, with coverage zones tailored to specific user groups on each network layer.

After the break, Elisabeth Rumsey of Vodafone continued the private networks theme by presenting the MNO perspective on the benefits of shared RAN. She began with statistics on Vodafone’s private mobile network (PMN) business, which includes 134 MPN deployments across 87 unique customers worldwide. Crucially, the success of Vodafone’s PMN offering has been creating a suite of PMN solution architectures that recognises the range of user requirements, as well as the mix of spectrum and regulation restricting deployment options in different locations. Being able to share equipment and infrastructure between private and public mobile network layers is key to creating this suite of options.

Finally, Simon Fletcher of Real Wireless reminded attendees why it takes time for new innovations in network infrastructure to be seen in reality, showing images of 3G equipment cabinets deployed 20 years ago – still in use today. He revisited the original 5G vision virtualised, service-based architecture that should have simplified infrastructure sharing across multiple Radio Access Technologies (RATs) and services, but described how this vision has become obscured once 5G has been rolled out in practice.

Looking ahead, shared RAN was reconfirmed as a worthwhile target, with total cost of ownership savings of 40-47% generally recognised as achievable versus building independently. Other benefits of reduced environmental impact and faster, more affordable service rollout were also cited. Government and regulatory interventions were discussed, including:

• The UK’s Electronic Communications Code 2017 update mandating infrastructure sharing rights
• Passive sharing requirements in the EU Broadband Cost Reduction Directive
• Ofcom’s 2023 mandate on indoor coverage improvements
• Saudi Arabia’s enforcement of shared RAN MOCN architecture and dedicated in-building spectrum

The traditional strength of the UK in shared infrastructure (linking back to Mike Ferris’ talk), but with a warning that other parts of the world are getting more active in this area, and the UK risks falling behind in areas such as access to shared spectrum.

Simon also highlighted the increase in overlapping interests between energy and telecoms networks and potential for sharing of infrastructure sets not just within mobile services, but across the mobile and energy sectors.

In conclusion, the panel session to close the event fielded many questions, but most seemed to converge on, if the benefits of shared RAN are generally accepted and technically possible, why have we not seen faster roll out of neutral host shared infrastructure in HDD locations? Remaining challenges discussed included:

Timing transitions to fit with legacy equipment

Lack of a harmonized view on how to do sharing (with JOTS potentially having a role to play here)

Access to shared spectrum to enable more MOCN deployments.

Gaining alignment of commercial interests amongst all participating parties, determining who should make the initial investment and deciding how to create the right shared risk and reward environment around neutral host deployments as we move from more obvious ‘venues pay’ indoor environments, to outdoor shared domains

Many thanks to all speakers and attendees for a lively discussion, to Fujitsu for sponsoring the event, and to the CW team for organising this engaging event. Looking forward to continuing this Shared RAN discussion in a rural, coverage focused context at the next Mobile Networks SIG event in November.