Focus on C-Band spectrum means 5G will be dense from day one

As some operators start to put flesh on their plans for early-stage 5G deployments, midband spectrum is emerging as a key enabler, and one which will place small cell technologies deep in the heart of 5G. And, in this context, the distinction between macro and small cells is becoming somewhat blurred: cells are smaller, on average, in 5G than 4G – as they were in 4G compared to 3G – and so the economics are difficult without low opex, automation, and many of the techniques and technologies SCF has helped drive in recent years.

At least half of the 5G roll-outs which will kick off between 2019 and 2022 will be in C-Band spectrum (a series of bands between 3.4 GHz and 4.2 GHz), which supports high capacity for enhanced mobile broadband, without the technical challenges of the emerging millimeter wave options. China is a significant force behind the use of C-Band for 5G and its market weight will help to drive a broad device ecosystem.

This is exciting news for the small cell community. Many of the developments which SCF members have helped to drive in recent years will be directly applicable to this first wave of 5G, because while the C-Band spectrum offers plentiful capacity, the propagation characteristics and the topography of most jurisdictions makes its range rather limited. That means larger numbers of cells are required to cover a given area, and so to make the business case work for operators, those cells will need to be affordable, interoperable and highly automated, to maximize efficiency and minimize total cost of ownership.

These issues, which will be critical to the 5G business case, have been central to SCF’s work for years, as we have focused on the complex issues of densifying a network to support smart cities, high mobile broadband capacity and emerging Internet of Things use cases.

All this will be very important to the first wave of 5G deployers – those starting commercial roll-out before 2023. Many of these early adopters will be using C-Band spectrum; and far from harnessing it just for a few dense hotspots, many are looking at broad zonal coverage, involving very large numbers of cells.

Some will use sub-1 GHz spectrum to achieve macro-based wide area coverage, but these bands will not provide the capacity required for the promised data rates for high quality video and new mixed-reality user experiences promised by 5G. And the majority of MNOs say they will first use 5G to enhance their existing core mobile broadband services, before moving on to new revenue streams enabled by 5G support for massive IoT and ultra-reliable low latency networks – so that capacity will be essential to their competitive advantage.

This is why there is high interest in millimeter wave bands, but there are still many challenges caused by their propagation characteristics. For the first phase, at least, C-Band – especially when combined with the enhanced carrier aggregation and higher order MIMO techniques supported in 5G standards – will be a strong capacity band, especially below 3.8 GHz (above that, there are issues with incumbent satellite users). It has the potential to support 200 MHz of capacity per operator, which will, in turn, make many ‘5G’ use cases, such as advanced virtual reality gaming, practical.

That potential will drive worldwide operator interest in C-band spectrum, and therefore in small cells – to be deployed as a layer covering many markets, not just as hotspots. In a survey of about 60 mobile operators conducted for SCF, respondents were asked what their primary deployment strategy would be in the first 2-3 years of their 5G roll-out. 58% said they would adopt a small cell-first approach, either to enhance existing mobile broadband or enable new revenue streams.

Figure: What will be your primary approach to deploying a 5G New Radio network in the first 2-3 years? Source: SCF MNO survey, 61 respondents 

The World Radio Conference in 2015 allocated 3.4 GHz to 3.6 GHz as a global mobile band. Where it is already available, it has typically been used for fixed wireless access and satellite, while in the US, the CBRS multi-tiered band plan has been introduced to allow shared usage. However, its real impact will be as the first major new 5G band. For instance, the 3.3 GHz to 3.6 GHz band is the main focus of Chinese 5G trials; South Korea will auction 3.5 GHz licenses this year; and Japan, which already uses 120 MHz of 3.5 GHz spectrum for TD-LTE, plans to refarm some of that for 5G and to extend the band to 4.2 GHz.

All this bodes well for the deployment of large numbers of 5G cells, often providing a dense overlay for a 4G macro network in lower frequencies. But the core requirements for planning and managing a very dense, cost-effective 5G network will be the same as in 4G, and all of these have been addressed in-depth by ongoing SCF work programs. For instance:

  • open frameworks (HetNet framework)
  • repeatable site approval and installation processes
  • automated management (SON API)
  • network APIs (nFAPI)
  • flexible backhaul options
  • future-proofing and migration to new architectures (functional splits for virtualized small cell networks)

SCF has made significant progress in all these areas to help members achieve their current densification goals, and the lessons learned will greatly ease the path to 5G density. In addition, the Forum is already studying many of the new developments which will be introduced to the dense HetNet at the 5G stage, such as new MIMO technologies, duplex schemes and orchestration platforms.

This work has laid the groundwork for the deployment of 5G in the C-Band, which will drive unprecedented levels of implementation of small cells round the world.