What to consider when planning a DAS

June 1, 2014
Across North America and Europe, many mobile network operators (MNOs) are currently rolling out long-term evolution (LTE) networks.

From the June, 2014 Issue of Cabling Installation & Maintenance Magazine

Physical challenges, cost questions and coexistence with other wireless systems require careful consideration ahead of deploying an in-building distributed antenna system.

by Matt Melester, CommScope

Across North America and Europe, many mobile network operators (MNOs) are currently rolling out long-term evolution (LTE) networks. Recent research from the Global Mobile Supplier Association (GMSA) revealed that 288 LTE networks were commercially launched by the end of the first quarter of 2014. The GMSA predicts some 465 LTE networks will be in operation in 128 countries worldwide by 2017.

But it is not only the wireless spectrum that is shifting; the entire industry is in a high state of change, with consumers demanding more and more from their network providers for less money from every location they visit or spend time. But without robust network coverage, consumers can't access the services that will drive up revenues for the operator.

There is no denying that wireless coverage is seen as increasingly essential in today's connected world. The volume of worldwide mobile data traffic reached 8.1 exabytes in 2012, according to analyst firm Analysys Mason-a figure only set to grow further. It predicts this volume of traffic will increase from 4.3 percent of the total Internet traffic in 2012 to 5.5 percent in 2018. With demand increasing dramatically across operator networks, consumers increasingly expect and depend on a seamless user experience from their service.

This master unit is part of CommScope's ION-U, a solution that was designed to simplify the design, planning, deployment and optimization of distributed antenna systems. ION-U includes integrated guidance and intelligence that help get a DAS up and running quickly.

The indoor data tsunami

When it is taken into account that upwards of 80 percent of mobile data traffic originates indoors-and most of this is accessed through smartphones-we see a clear objective for MNOs to adopt an indoor wireless strategy that ensures robust coverage in buildings. The ever-increasing phenomenon of bring your own device (BYOD) is also putting pressure on indoor networks as more people bring their own smartphones and tablets into the workplace. It is predicted that one billion employee-owned smartphones and tablets will be in use in the enterprise by 2018.

Yet only two percent of the more than 300 billion square feet of worldwide commercial real estate is covered by an in-building mobile wireless system, according to CommScope calculations.

Today, for operators and those with the responsibility of managing such systems within buildings (for example, IT departments, buildings and facilities managers) there is increasing pressure to consider wireless coverage as being as essential as wired access to the local area network (LAN). This needs to be done at the earliest possible stage of building planning to ensure a seamless level of access to the wireless network from within a building rather than from outside.

So how can MNOs ensure they can obtain the maximum possible revenue from users and provide the best possible experience by providing strong, reliable signals inside a building?

Buildings affect mobile network coverage-getting signal through different kinds of walls is one of the biggest challenges facing MNOs. Old buildings built with dense materials and new buildings using the latest in heavy insulation and reflective glass can prevent radio signals passing through. However, users accustomed to 3G connectivity and, increasingly, those using newer 4G networks, expect access to high-speed data at all times regardless of where they are. Two-thirds of smartphone users expect websites to load in four seconds or less.

In-building wireless solutions began with a focus on extending coverage using an "outside-in" approach regardless of the type of venue. With the increase in data traffic in many markets, operators began to focus on creating additional capacity inside the building, offloading the macro network as part of a new "inside-in" strategy. This approach requires higher infrastructure investments, so the MNOs started in larger venues (e.g. airports, stadiums, rail systems) with high traffic and therefore good return on investments. With the increased level of business requirements from enterprise buildings, this inside-in approach is being extended to a much larger number of venues. Increasingly, operators are looking at smaller-sized buildings to ensure good network performance, protect their reputation and satisfy customers. Indoor solutions are about putting capacity and coverage where the users are.

A variety of solutions likely will be needed by operators to handle the needed capacity for subscribers.

• Distributed antenna systems (DAS)-The original small cell. DAS has been a proven choice for more than 25 years. It is predicted that in the next 10 years we will see explosive growth in DAS, from one million DAS nodes deployed annually in 2018 to more than 100 million in 2023. DAS networks are often multi-operator, multi-technology, high-capacity solutions.

• Pico cells or remote radio heads-These solutions are targeted at adding capacity in small to medium buildings, for one operator only.

• Concealed, integrated micro cells-These are basically mini macro sites, designed to address the common problems of site acquisition and licensing in congested, urban areas. Metro cells are an outdoor solution but must be integrated into the overall network, just like some other small cell solutions. The remote radio unit, antenna and other RF path equipment are concealed in one monopole-type structure.

Planning a building

No one would plan a building without lighting or plumbing, so why consider a new build without thinking about access to a mobile network? Yet, everything about the way a building is designed is counter to ensuring good wireless coverage. Thick walls are built to provide sound insulation, while air-conditioning systems are designed to keep warm or cool air within a room. As such, a good RF system needs to be invisible and penetrating. The key is in the planning.

The skills useful for deploying RF DAS networks are different from those needed in IT. There are challenges in the design (e.g. which technologies, frequency bands and carriers are supported), deployment, aesthetics and costs of such a solution. Having an understanding of who will be using the network and for what purpose is integral to the successful rollout of a wireless indoor solution. As such, defining the user experience is an essential first step. The questions that should be asked include the following.

1) Who is the building to serve; which technologies and carriers must be supported? Is it for the general public, whereby all visitors must be able to access a multi-operator solution? Perhaps it is for a small business that only requires access to WiFi, or a single enterprise that need only be served by one wireless operator?

2) What level of security is required for access to the network? Obviously, businesses in the financial-services, healthcare and government sectors may have very high security requirements, and this poses another challenge for those planning a robust solution that can deliver a good QoS.

3) How will it be installed?

4) What will it look like and how can it comply with planning regulation and aesthetic requirements?

5) How much will it cost and who will pay for it?

If the wireless service is being delivered by a third-party provider, any failure of that service will impact the reputation of the operator. If such a solution is deployed within the building of a major enterprise, the effect could be highly damaging for the operator in question. It is incredibly important that high standards of quality are agreed to and maintained prior to the installation of any indoor technology. A good example of this was during the London Olympics, whereby all operators and vendors involved in the multi-operator systems deployed in various stadiums agreed to particular parameters, which saw a successful service being delivered.


Some challenges in deploying in-building wireless networks are physical in nature. Providing wireless access on the third floor is all well and good, but it becomes a challenge at the very top of a 100-story building. And while it may not seem difficult to provide wireless coverage for 50 people, it certainly is if you have 100,000 in one building.

Although DAS is a well-proven solution for adding network capacity, innovation for simplifying the practical implementation of that solution has been stubbornly slow. This lack of simplification has meant longer time-to-market, prohibitively expensive engineering skill requirements and notoriously difficult optimization, testing and maintenance. Every stage of traditional DAS deployment can be an exercise in extra expense and delayed ROI. Operators continue to use DAS, however, because of the pressing need to offload traffic from the macro network in order to free up capacity for ever-increasing mobile-data use.

There is also the question of cost and who is going to pay for the solution to access the wireless network. The debate over whose responsibility it is to provide wireless coverage has been raging for many years. With MNOs looking to increase revenue and reduce costs at every turn, it is they who ultimately benefit from users within buildings having access to their services. This is particularly true of data-hungry LTE networks.

In a single building, there is often a strong desire from the building manager to install a multi-carrier solution. This is ultimately because the user doesn't care where their coverage comes from, but they expect a seamless user experience with maximum capacity and access without any complexity or sign-in issues, regardless of their network provider.

Small cell and WiFi coexistence

The role of WiFi in a mobile network has long been debated. The fact is MNOs do not build a WiFi network to generate revenue but to "offload" traffic from networks overburdened by data use carried over their networks. For example, O2 UK created a WiFi network to offload traffic from their very expensive cellular network. The launch of LTE networks, however, has led many industry experts to query whether WiFi can coexist with this new technology.

CommScope believes unlicensed WiFi and licensed cellular networks may coexist and both play a role in the network of the future. WiFi can alleviate the stress on a 4G network in high-density areas, thereby not discrediting its utility. The coexistence of WiFi and carrier-grade LTE allows enterprises to separate applications based on different access requirements, but overall covering all their business needs.

In dense urban areas, where demand for WiFi has traditionally been strongest, small cells will be critical for the shift to LTE. Small cells are defined as everything that is not the macro cell. This definition can be further broken down into the metro (or micro) and indoor layers of the network. These layers are designed to significantly increase capacity by moving closer to the mobile device, working in conjunction, not competition, with sector splitting on the macro layer.

One of the challenges related to these different network layers is maintaining good coordination (i.e. avoiding interferences between the layers) and assuring smooth handover processes in order to keep uninterrupted services for users while they move between these different layers.

The increasing demand for LTE, and the heightening expectation for a quality service, will mean that more focus than ever must be placed on efficient small cell deployment and integration.

This will be particularly relevant in urban centers where increased data use is dramatically impacting the network at present. With the proliferation of data-intensive devices like smartphones and tablets only set to rise, focusing on how to offload traffic from the macro site and ensuring that demand for top-rate coverage is met indoors and out will become increasingly important.

Matt Melester is senior vice president and general manager of CommScope's (www.commscope.com) distributed coverage and capacity solutions.