Tuesday, 1 September 2020

5G Small Cells Definition

In our basic introduction on Small Cells and Macrocells, we discussed that the small cells definition can sometimes be fuzzy. Having said that, it was still easy to define the small cell based on the topology. With 5G, as there are quite a few different splits, you can have Integrated as well as disaggregated small cell. To simplify the confusion around this, Small Cell Forum (SCF) unveiled 5G Small Cell Architecture and Product Definitions.


Document 238.10.01 available here provides the necessary details. The contents of the report include:

  • Definition of 5G Small Cells and Small Cell Networks
  • 5G Small Cell Deployment Scenarios
  • Small Cell Network Architecture and Product Types
  • Small Cell Power Considerations
  • 5G-Small Cell Product Definitions
    • Integrated Small Cell Configurations (Survey Results)
    • Radio Unit (RU) for Disaggregated Networks (Survey Results)
    • Distributed Unit (DU) for Disaggregated Networks (Survey Results)
    • Analysis and Discussion of Configuration Results
  • Conclusions 

The article here states:

Why do we need definitions to inform the design of 5G small cells?  Well, in the 5G era, small cells will be deployed in a far wider range of scenarios than in the past, and the form factors and architectures will be extremely varied.

The introduction of virtualized, disaggregated networks means that some small cells will consist of two or three elements, while others will still be all-in-one. Some form factors will be classed as ‘mini-macros’, which can be deployed unobtrusively on street furniture but have performance and power levels close to those of larger base stations. Others will be so tiny they can be embedded into pavements or consumer electronics.

And we shouldn’t be focused on form before function. Are we talking about outdoor or indoor small cells? Are they to service airports or factories?

It is clear, then, that old definitions are now inadequate, and there are real and present dangers of the industry fragmenting between hundreds of different designs that had insufficient common features to achieve any scale.

This is a major piece of work to provide a consensus view and concise definition of the types of 5G small cells and the key characteristics of the different types of commercially viable 5G small cell RAN products over the next five years. It is supported by a major survey of operators, other small cell deployers, and supply chain members.



The official press release says:

As small cell use cases diversify, 5G Small cell architecture and product definitions highlights the need for clear understanding of the requirements for each of the range of options that will be needed. The risk of diversity is fragmentation, so deployers and vendors will benefit from having clear baseline definitions of the technical specifications, power and spectrum choices, and key interfaces, for any given architecture in any given environment. That will enable the industry to innovate within common, agreed design frameworks, supporting diversity while also maintaining scalability and interoperability.

The first such study of its kind, the report provides an informed view of the most important configurations and specifications for companies deploying small cells between now and 2025. It aims to provide a consensus view and concise definition of the types of 5G small cells being rolled out now and in the near future. It also includes definitions of the key characteristics of the different types of commercially viable 5G small cell RAN products that will be available over the next five years, including 3GPP and O-RAN Alliance 5G disaggregated open RAN specifications – work that covers macrocells, but also includes microcells and picocells.

This study also provides a uniquely detailed analysis of the capabilities that small cells will need to support in any combination of architecture and deployment environment. It makes it clear that in the 5G era, no single design or specification can meet every requirement across all the scenarios. Instead, it will be important to optimize small cell designs and specifications for each environment, to encourage adoption and drive new usage, especially in the enterprise, industrial and campus settings where many new use cases for dense cellular connectivity are emerging.

Some key conclusions are:

  • Split 6 and 7.x are the most popular among those currently planning disaggregated small cell deployments, as well as dual-split architectures including Split 2. Split 8 is also known to be popular in China for indoor enterprise deployments.
  • Split 7.2 O-RU based solutions are predominantly planned for outdoor campus, urban and private networks, whereas split 6 S-RU based solutions are for indoor enterprise.
  • Remote integrated and RU small cell products are limited by power consumption, environmental conditions, maximum output power and volume. gNodeB and RUs generally are passive-cooled, and powered by Ethernet (PoE), fiber (PoF) or powerline.
  • 2 and 4-layer MIMO is most popular in smaller deployments although 8-layer MIMO may be required in some larger enterprise campus, urban and private deployments, and potentially longer term.

“In the early days, small cells looked fairly similar, regardless of the environment in which they would be deployed, and were easily distinguishable in size, weight and power output from other mobile equipment. In the 5G era, small cells will be deployed in a far wider range of scenarios, and form factors and architectures will be extremely varied,” said Prabhakar Chitrapu, Chair of Small Cell Forum. “The form factor, power, size, interfaces and specification will vary according to the use case and deployment scenario, and with the introduction of virtualized, disaggregated networks, some small cells will consist of two or three elements, while others will still be all-in-one. It is clear that old definitions are now inadequate, and there are clear and present dangers of the industry fragmenting between hundreds of different designs with insufficient common features to achieve any scale.”

Many of the challenges in the deployment of small cell networks to date have been rooted in regulators and legislators having to certify individual items in an increasingly fragmented market. This report will be valuable for the whole ecosystem: for vendors and components makers looking to prioritize their development efforts on areas of highest demand; for operators and neutral hosts, to help as they make their architecture choices; and for external stakeholders such as regulators and legislators, to expedite site selection, certification and deployment.

"Small cells, or femtocells as they were previously known, have played an increasingly important role in wireless networks since their introduction more than a decade ago. One would have thought that a small cell is well defined; however, it has taken significant effort to work out what a 5G small cell is,” remarked Vicky Messer, Director, Product Management at Picocom. “It has been a great pleasure working with industry colleagues over the past few months on this SCF 5G small cell architecture and product definitions paper. As a result, we now feel we have a definitive answer.”

The baseline small cell product configurations detailed in the report are essential to inform hardware component design and reference architectures, and crucially, are based on an SCF consensus which, in turn, represents inputs from a wide range of operators, vendors, component makers and other stakeholders.

This set of configurations is not prescriptive, and it takes account of work done by other organizations. In this way, the report will help drive the increased ecosystem diversity and lower-cost small cell solutions demanded by the industry and, most importantly, its customers.

Small Cell Forum’s work on common interfaces, at system-on-chip level (FAPI and 5G FAPI) and system level (nFAPI) is the best-established effort to define a common framework within which many designs and many suppliers can innovate and interwork. The survey of operators and other stakeholders, conducted for this report to understand key design requirements, highlighted strong support for these interfaces and SCF’s Split 6 architecture.


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