Small cells at scale
Written by: Sam Fenwick | Published:

Dr. Prabhakar Chitrapu, the new chair of the Small Cell Forum (SCF), speaks to Sam Fenwick about his priorities for the organisation and its work to address many of the challenges associated with large-scale small cell rollouts.

One of the most impressive things about the telecoms industry is the dedication of its members, and a visible sign of this is the way many of the senior roles in the organisations that play a vital role in the advancement of technology are held by volunteers who already have high-pressured and demanding jobs of their own. It requires a tremendous balancing act – after all, as the old saying goes ‘no-one can serve two masters’ – and one made even more demanding by the strains of international travel and the inevitable time away from kith and kin.

Take the Small Cell Forum (SCF), where such concerns prompted David Orloff, who had been its chair since 2016, to step down. Fortunately, his successor, Dr. Prabhakar Chitrapu, is no stranger to SCF, as he has been involved with it since 2010 and previously served as chair of the forum’s TECH & 5G Working Group. He has also led SCF’s collaborations with other industry bodies and is understandably keen to continue to drive this in his new role and extend this approach to other stakeholders.

Many hands make light work

“First and foremost, [my priority is] to increase our engagement with operators, vendors and enterprises, and I also want to get participation from all regions around the world” Chitrapu says. He adds that SCF created a body within itself, the Enterprise Advisory Council, which allows enterprises from a number of sectors including hospitality, healthcare and property management to increase their knowledge of small cells and encourages their use. In this process, SCF learns about the specific requirements from these enterprise verticals and publishes them for the benefit of its members and the industry in general. Chitrapu adds: “We were really pioneers in this regard; as 5G comes on, it’s important to have the enterprises engaged explicitly in our conversations.”

The shift to split architectures

Chitrapu explains that SCF has revised its 2020 workplan, which has seven key areas. One of these is developing 5G Open Small Cell RAN architectures. “We’re moving away from an all-in-one gNodeB/Small Cell [a 5G base station] with a distributed network architecture to split gNodeB/Small Cell with a centralised network architectures. In the former, the gNodeB/Small Cell is a single ‘box’ with the network being made up of multiple instances of them. In contrast, in the latter, the gNodeB/Small Cell is split into two (or three) parts, with the network being made up of a single central unit supporting multiple remote units. There are a lot of reasons for doing this including cost, efficiency and latency.” Chitrapu adds there are several options for splitting the gNodeB/Small Cell, and three organisations driving three options: 3GPP (based on option 2), the O-RAN Alliance (option 7) and SCF (option 6). These options essentially trade off between the extent of co-ordination and efficiency within the network and fronthaul transport bandwidths/costs. SCF is collaborating with OAI (Open Air Interface) and will be collaborating with the O-RAN Alliance. The underlying rationale is the way the very dense 5G networks of the future are expected to have very large numbers of small cells in areas such as busy city centres (requiring their deployment inside or on street furniture), which will require greater co-ordination between them, and centralised architectures are a way to achieve this. In addition, some of the split architecture options require less transport bandwidth, and Chitrapu says that is one of the drivers of this approach.

Chitrapu adds: “There’s an increasing opportunity for neutral host players to jump in. Traditionally, MNOs built and operated the networks, but in the context of dense small cell networks, it is sometimes more economical for third parties to build the networks, which one or more MNOs can operate and provide services on. Many neutral host players are now trying to exploit such opportunities.”

Unleash the robots

As was emphasised at this year’s Small Cells World Summit (see our June issue), one of the most formidable barriers to this vision is the logistics of deploying so many small cells in an urban environment, given the need to acquire sites, carry out the civil works and have enough trained engineers. Chitrapu adds that there is also the need to address the requirements of local municipalities and regulators, and that SCF is working in this area to educate them and provide them with information on dense networks’ characteristics, such as aesthetics, density and power levels. In addition, Chitrapu says SCF is developing a document that neutral host companies can use as a starting point for discussions with these stakeholders.

One other potential stumbling block is the complexity of designing dense networks and working out where best to deploy small cells in environments with lots of street clutter, and constraints around backhaul and which sites are available, as well as a considerable number of restrictions. Given there are so many variables and data sources to consider, Chitrapu says this is an area where artificial intelligence (AI) and machine learning (ML) can come into play, and adds that SCF and 5G Americas have collaborated on a white paper that looks at how these technologies can be used to address this problem.

He says automation, coupled with AI and ML, will also be required to manage dense small cell networks given their size and complexity, together with the increased flexibility that will come from the use of virtualised network functions running on standard computing platforms; SCF has already completed some work items in this area.

Meeting at the network edge

Our conversation turns to edge computing, which SCF feels is “almost as important as 5G and is highlighting a fundamental [difference in the way that] our networks are being built. Until recently there was a clear separation between the RAN and core network. Of course they were interconnected, but to a great extent, these networks are built and operated somewhat independently. However, the RAN is getting more centralised and is pushing towards the core, while the core network is getting distributed and parts of it are being pushed further towards the end-users. So the RAN and core are coming together at the so-called ‘edge’.” Chitrapu also highlights the way edge computing is going to enable local services, such as the use of virtual and augmented reality in a stadium to enhance the visitor experience, and in factories to enable greater automation.

He adds that edge computing is “still in its early stages of deployment, with a lot of ongoing proof of concepts and trials. SCF has a plenary meeting coming up in Pittsburgh, USA, which will [be co-located] with an open edge computing (OEC) organisation’s event, when we will be exploring potential areas of collaboration. Similarly, SCF and ETSI-MEC (an organisation that pioneered Multi-Access Edge Computing concepts) met earlier this year in London during their co-located events and continued their ongoing collaboration discussions.”

Finally, SCF is looking into the use of shared spectrum for private networks – “we have a work item there,” says Chitrapu – and it is collaborating with the CBRS (Citizens Broadband Radio Service) Alliance in the US, in the general area of developing the use-cases. Naturally as SCF’s remit is a global one, Chitrapu says it is excited about working with similar organisations and spectrum regulators in other countries. He highlights the importance of spectrum sharing to enterprises looking to have their own private networks, given the difficulties and cost of obtaining it for their exclusive use. Chitrapu also notes the way in which the combination of neutral hosting, private networks, shared spectrum and applying network slicing techniques to public networks will allow a wide range of business cases to be satisfied.

It’s clear that with 5G rollouts now in full swing, Chitrapu’s appointment comes at a pivotal time for the small cell industry. Given the sheer complexities of the challenges ahead and the way that doubts persist in some quarters about the viability of 5G business cases, it’s great to hear that Chitrapu and SCF are taking a collaborative approach, particularly with verticals and civic authorities.

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