Introduction:

Small cells are increasingly used to boost network densification and expand coverage for both private and public networks. They will be increasingly important in the deployment of 5G mmWave networks because of the very short propagation distances which require many small cells for adequate coverage in a given geographical area.

5G small cell market is gaining momentum due to the higher bands like mmWave limitation, in-depth in-building coverage requirement and strategic area densification. However, despite the hype surrounding 5G, 3G/4G deployments are expected to remain the dominant technology in terms of volume shipments until 2022 when 5G small cell deployment will overtake 3G/4G. Therefore, because small cell densification is moving forward, integrated small cell platforms supporting both 5G and 4G radio are essential for the next five years.

Small cells deployed in strategic areas have also accelerated the new virtualized and disaggregated architecture adoption, aiming for greater cost-efficiency and flexibility. Together with edge computing, they are enablers for enterprise digital services such as manufacturing applications, smart harbor/terminal, local contextual applications and IoT services.

Definition of Small Cells:

• Femtocells
• Picocells
• Carrier-grade Wi-Fi

Gartner’s Key Findings:

• The small cell solution is shifting from delivering in-build coverage to enable large-scale network densification. Increasing 5G and private network deployments further accelerate the trend.
• In the small cell market, variety and diversity are replacing uniformity. Introduction of new spectrums, types of cells and architectures, vertical industries use cases, and business models like neutral host act as accelerators in this respect.
• In addition, diversity increases the cost and complexity of small cell deployment and management, not just access points but also potentially edge computing, localized core and distributed radio units.
• Traditional proprietary small cell systems are challenged by disaggregated, virtualized architecture. Communications service providers (CSPs) are looking for a more flexible, multivendor, cost-effective solution through breaking apart basebands and radio heads, and virtualizing some or all of the baseband functions in software.

Gartner’s Recommendations for Small Cell Deployment:

• Build your small cell deployment strategy beyond coverage through prioritized investment in network densification and related digital services. Include 5G small cell and private networking requirements in your product plans.
• Address diversity challenges through a multivendor approach. There is no one size fits all in the future small cell market, and a scenario-oriented product evaluations process needs to be implemented.
• Reduce complexity and improve cost-efficiency through prioritizing the deployment feasibility as well as operation intelligence and automation.
• Work closely with emerging suppliers and establish an objective and structured process to thoroughly evaluate and develop quick prototypes using disaggregated and virtualized architectures.

Small Cells Will Be at the Forefront of Virtualization and Open RAN:

The economic success of 5G is reliant on interoperable multi-vendor networks, which require open interfaces at both the silicon and network levels. Therefore, many CSPs are continually exploring the possibility of moving away from the proprietary hardware to more modern open and interoperable systems.

To support these, CSPs will need to adopt new network topologies such as cloud-RAN, virtualized RAN (vRAN) or open RAN (ORAN), together with integrated edge compute.The key to the open network lies in disaggregation — separating the key elements such as centralized units (CUs) and distributed units (DUs) — and the open reconfiguration — combining components from any suppliers because they are all interconnected in the same way.

For 5G, those central processes will usually be virtualized (run as software on off-the-shelf servers).The move to open network has been more advanced in small cell layer than macro network, and several suppliers already offer architectures in which a number of small cells are clustered around a centralized, virtualized controller. But there are two potential barriers to achieving a real multivendor environment: the need to be in agreement on where the network should be split between the central and the local elements and the need to be a single common interface between the elements in each preferred split.

Split RAN/SC architectures have multiple options, as identified by 3GPP. Of these, 3GPP has focused on Option-2 (RLC-PDCP), ORAN on Option-7.2 (PHY-PHY) and Small Cell Forum (SCF) on Option-6 (PHY-MAC). SCF will develop a 5G version of its networked FAPI spec, which will enable a split MAC and PHY in a disaggregated small cell network, supporting the 3GPP Option-6 split over Ethernet fronthaul and targeting, in particular, cost-effective indoor scenarios. SCF’s work on open interfaces such as nFAPI will play an important role in the market, alongside the work of partners such as O-RAN Alliance and Telecom Infra Project.

Many CSPs expect to take their first steps in their small cell layer, providing valuable experience of how to manage and orchestrate a network in which multiple radio units share common baseband functions, some of them deployed on cloud infrastructure. While there are still challenges in this domain, the disaggregation and virtualized architecture reduce the technology barrier to market and introduce new players into the market including software players as well as OEMs and ODMs.