On the air: distributed antenna systems (DAS)

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The Royal Institute of British Architects has stated that we spend an average of 20 hours each day inside commercial or residential buildings. Given there is at least one billion buildings across the world, whichever way we look at it, or slice and dice the data, it’s clear buildings are a vital part of our lives.

Bringing cellular signals indoor with in-building wireless (IBW) systems is a challenging feat, but something building owners and IT departments are increasingly grappling with today. According to a survey by CommScope, almost 75 percent of building professional respondents cited IBW connectivity as ‘important’ or ‘very important’ to them.

That’s not surprising considering the numerous advantages of IBW connectivity referenced in the survey: increased property values and workforce productivity, plus an easier time attracting top talent and visitors. Two-thirds of respondents also rated indoor wireless connectivity as ‘essential’ for employees. In fact, Australians spend 10 hours and 24 minutes engaging with their internet-connected devices daily on average, according to the EY report entitled ‘Digital Australia’.

In many ways, cellular IBW solutions are complementary to Wi-Fi. For permanent and regular building inhabitants who need data and internet access, Wi-Fi provides secure access to the corporate network with no service charges, and no network operator is required to install or run the system. But, in the majority of circumstances, Wi-Fi is not enough by itself.

As IBW systems operate as an extension of a mobile operator’s network, they inherently provide reliable wireless voice connectivity. They also support the wireless data needs of visitors and customers, without requiring clumsy manual log-ins.

Cellular technology evolved in the telecom market, but enterprises increasingly need to master the craft. IBW solutions require enterprise owners and IT managers to carefully weigh the benefits and costs to determine the most efficient option. It’s imperative that the ideal solutions not only meet the needs of today’s tenants and users, but also offer the flexibility and agility to serve future needs as well.

IBW solutions fall into two main categories: distributed antenna systems (DAS) and small cells. While these share some physical and configuration similarities, they operate differently. And each offers unique advantages.

DAS: POWERFUL AND SCALABLE COVERAGE FOR LARGE VENUES

Built from a networked series of remote antennas, or nodes, DAS is an established wireless coverage and capacity technology. DAS is an effective means of delivering uniformly high-quality wireless coverage and robust capacity across:

  • a large indoor area (such as a high-rise office building)
  • a contiguous outdoor area (such as a stadium, open courtyard or entry space), and
  • a combination of indoor and outdoor environments (such as a college campus).

Indoor areas are typically covered by low-power DAS and outdoor spaces are covered by high-power DAS. The latest generation of DAS solutions can integrate both low- and high-power networks into a single, unified platform for mixed environments. DAS is an inherently scalable solution, which means it can be expanded to cover larger spaces and awkwardly-shaped areas.

DAS is well-suited for high-profile, multi-band, multi-operator environments and therefore has been used extensively in large stadiums, airports and other public buildings, such as convention centres and shopping malls. All of these environments are characterised by large numbers of users who bring their own devices (the ‘Bring Your Own Device’ or BYOD principle) and their own mobile network operators.

DAS has developed a reputation for complexity and being high-cost, but recent advances have helped the technology scale economically to serve larger office buildings and enterprises. For example, ‘Enterprise DAS’ products use standard Ethernet cabling, rather than expensive and heavy coaxial cables. They also eliminate the need for laborious tuning of power levels at each antenna through the use of digital signal transport and automated configuration tools.

SMALL CELLS: AFFORDABLE AND ADAPTIVE

For smaller indoor locations, small cells offer an economical alternative that’s flexible and self-contained. Small cells are able to support deployments spanning the size and population of a small- to medium-size office building. Small cells are relatively easy to install, which makes them an attractive option for an enterprise environment. Unlike DAS, which connects to an outside base station owned by a wireless operator, small cells include their own baseband unit.

A given model of small cell typically only supports one operator’s network. Conventional small cells cannot dynamically share capacity between access points, so large gatherings in small spaces may create bottlenecks – a phenomenon sometimes called the ‘cafeteria problem’.

Traditional small cells also create areas of overlap where their cell boundaries meet. In these areas, cellular connections suffer significant drops in service quality: reduced data rates, choppy voice and dropped connections. This problem can be mitigated, but never completely eliminated, through careful optimisation of small cell placement and power.

New Cloud RAN (C-RAN) small cells address these issues and are beginning to bridge the gap between DAS and small cells. Unlike traditional small cells, C-RAN small cells create a single physical cell across
a large number of access points. Radio frequency planning is simplified relative to stand-alone small cells in which each access point risks interfering with all of its neighbours. C-RAN enables cell virtualisation, which is like server virtualisation, but applied to the airways, to increase capacity.

DAS OR SMALL CELL?

Choosing the right solution for an IBW deployment involves answering several questions:

  • How much space must be covered?
  • How many people must be supported?
  • How much will the cover age and capacity demand change from one day to the next?
  • And, perhaps most importantly, how much will it all cost?

By carefully identifying expectation – and thoughtfully considering the future of your business – the ideal IBW solution will become clear. Keep in mind, however, that both DAS and small cell solutions continue to evolve and improve over time, with several key innovations hitting the market right now.

Small cells are improving their scalability, and DAS is becoming more economical. This means that you – the owner, manager or architect – will have access to an ever- improving array of options as time goes on.

Gavin Milton-White is vice president Enterprise, Asia Pacific, CommScope.

This article also appears in the August/September issue of Facility Management magazine.

Image: alphaspirit © 123RF.com

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