Paolini: The future – and the present – of HetNets

By Monica Paolini, Senza Fili Consulting

Monica Paolini

"We have been talking about small cells for a long time now, but when are operators going to deploy them for real?" is a question I often get. True, I also used to get the same question about Wi-Fi hotspots, and, even though it was a somewhat slow process, today every smartphone has Wi-Fi and can find some way to connect to a Wi-Fi network.

Small cells are likely to follow a similar path. With the exception of a few Asian countries like South Korea and Japan, large small-cell deployments have yet to come, but operators have started to lay the foundations for small cells, by gradually moving to HetNet topologies and to adopting the SON features that add most value in the existing networks. This is one of the key finding discussed in a new, in-depth report, "Making HetNets a reality", free to download here.

Initially, there was an expectation that small cells would be cheap and easy to install--you find a lamppost and install the small cell on it. It turns out it is not going to be that simple. A small cell is easier to install than a macro cell, but there are still many site acquisition, installation and management issues that arise because small cells are located in environment that are inherently more dynamic and outside the operator's control.

Equally important is the need to manage them in the context of a HetNet which include multiple layers and technologies that need to coexist and complement each other to bring the increased capacity density that operators need.

Most operators plan to deploy small cells in the same spectrum channel as their macro cells, and managing interference between the two layers is essential to protect macro performance and to maximize the contribution of small cells. A small cell in the wrong location with respect to the surrounding macro cells and subscriber concentration may lower the overall network capacity rather than increasing it, especially if RF transmission in the macro- and small-layer is not coordinated.

Similarly, most operators view Wi-Fi as an essential component of HetNets and small-cell deployments, but to leverage the contribution of Wi-Fi in transporting mobile traffic, the Wi-Fi infrastructure has to be integrated with the cellular network so that operators can offer seamless connectivity to Wi-Fi and a consistent service offering across interfaces.

This is where HetNets come in--in the present, rather than in the future of small-cell mass deployments. HetNets are often seen as coextensive with small cell deployments, but that's only one component. HetNets represent a new way to plan and manage mobile networks--a way that is rooted in a densification of the RAN, but that is not limited to 3G or 4G small cells. It includes also technologies such as Wi-Fi, network elements such as DAS, and solutions such as cloud RAN.

HetNet topologies require operators to take a new approach to run networks that is more complex, that requires a higher level of automation and more sophisticated traffic management and network optimization tools. The goal is to increase spectrum efficiency and network resource optimization. Operators have started to work on it already and small-cell deployments are part of this process, but not necessarily the first step. The transition to HetNets--and the attending introduction of SON functionality--has started already and it is preparing the ground for small cells. Central to HetNets is the ability to manage the growing complexity with SON tools like automatic neighbor relationships (ANR), which many operators have started to use already.

Drivers to the evolution to HetNets:

Source: Senza Fili

As mobile operators trial HetNet topologies and network management tools, their approach to HetNet strategies--and specifically cellular and Wi-Fi small cells--is evolving as they learn how to address the new challenges they are facing, and to take advantage of the new opportunities for service creation and revenue generation that a more flexible and more efficient network afford. We discuss this evolution in detail in our report here, but a few key trends stand out:

-        Adoption of HetNet functionality and small cells will be gradual, and follow an organic demand-driven path, requiring a high level of flexibility in the planning and deployment process. As operators plan for larger commercial small-cell deployment, SON functionality and hence LTE-Advanced capabilities have become a prerequisite for deployment.

-        Small cells and, more generally, the RAN infrastructure is moving indoors, where most of the traffic is directed. Huawei has seen levels of over 90 percent of data traffic from subscribers in indoor locations in some of their customers' networks.

-        Mobile operators started their small-cell deployments with residential femtocells. Now they have started to show a higher level of interest in the enterprise, to provide not only indoor coverage, but also to provide new services and to foster closer ties with enterprise customers.

-        The role of Wi-Fi is shifting from an offload technology to a fully-fledged RAN interface that is integrated with the RAN and core of mobile networks. Carrier Wi-Fi starts with seamless SIM-based authentication, but covers much more ground, to reach cellular and Wi-Fi integrated policy and traffic management.

These trends indicate a high level of activity, but also underline the fact that both operators and vendors are still exploring different ways to transition to HetNets. We do not yet have all the answers--and in fact we do not expect to see the emergence of dominating path to HetNets, but rather the coexistence of multiple approaches tailored to the specific characteristic of markets and the preferences of operators. The heterogeneity in HetNets is not limited to the technologies and network elements, but extends to the tools and topologies that each operator will select for their networks--or for parts of their networks.

Monica Paolini, PhD, is the founder and president of Senza Fili Consultingand can be contacted at [email protected]. Senza Fili Consulting is an analyst and consulting firm that provides advisory services on wireless data technologies and services.