19/08/2015

By John Spindler, director of product management at TE Connectivity

Enterprise network managers know that they need to improve mobile services within their organisations, but they often have a lot of questions about the technology, deployment and support. Indeed, the growing number of millennials within the workplace and growing trends, such as Bring Your Own Device (BYOD), means businesses are under increasing pressure to have a solution in place that will provide sufficient coverage throughout the office.

Distributed antenna system (DAS) technology enables coverage and capacity in places where companies are having difficulty providing licensed wireless mobile voice and data services to customers or users. DAS can be fitted into existing wall cavities and utility areas without affecting infrastructure. Let’s look at the six key questions and answers about enterprise DAS.

1. What is the key problem in enterprise mobile: coverage or capacity?

The problem is coverage. When we define “enterprise mobile,” we mean smaller venues such as hospitals, hotels and multi-unit office buildings, as opposed to stadiums or airports. In these smaller venues, user density is one user for every 100 or 150 square feet, compared with a stadium, where there is one user for every 6 or 10 square feet. The higher the user density, the greater the capacity needs, so capacity isn’t an issue in enterprise deployments.

2. How does DAS stack up against small cells for providing enterprise mobile coverage and capacity?

Small cells typically link coverage and capacity to one unit, and historically, small cells have been more like Wi-Fi access points – bringing coverage and capacity to specific “hot spot” areas within a building. But, if we know that coverage is the primary challenge for mobile services in an enterprise, a DAS is a better solution. This is particularly the case in larger office buildings where a small cell solution would require dozens, or even hundreds of small cells.

It’s also important to consider which services are required in the enterprise. Does effective mobile service require the system to support two frequencies or five frequencies? With today’s technologies, a DAS is more capable of handling multiple frequencies than a small cell and easily supports more than one mobile operator.

But DAS and small cells can be complementary technologies. Since enterprises are looking primarily for voice services out of the mobile network (data is usually handled by Wi-Fi), it’s possible to eliminate expensive, full-sized base stations from the deployment. Instead, it’s possible to use a small cell to provide the capacity and the DAS to distribute its signal throughout the building.

3. What are the cost elements of DAS compared to small cells?

The DAS has a hardware element, a cabling element, and antennas. You also need a radio frequency (RF) source to feed it – and this may be paid for by the mobile operator. With a small cell system, it’s the small cell itself, cabling to feed the small cell, and a backhaul connection to tie the small cell back into the cellular network.

Traditionally, the argument against DAS was that it uses half-inch coax cabling, which is costly and difficult to deploy. But today, DAS uses structured building cabling like Cat5 and Cat6 Ethernet cabling or fibre. If you think about the cost of deployment as the cost per antenna or the cost per frequency supported, the cost scenarios for DAS and small cells even out.

4. How do you bring mobile network signals to an enterprise DAS?

There are multiple ways to bring the carrier’s cellular signal to a DAS. There are off-air repeaters, which use signals from neighbouring cell sites. There are traditional base stations, which introduce a lot of cost into the deployment equation. And then there are small cells, which have the advantages of lower cost, easier deployment, and right-sized capacity for an enterprise. If you need more capacity than one small cell can provide, you can add one or two additional small cells in the DAS head-end. Since these units are small, they can be easily accommodated into the DAS head-end space.

5. How does a DAS adapt to new frequencies?

It depends on the DAS deployed. There are narrowband DAS that support between one and three frequencies, but there are also broadband DAS that support up to eight frequencies. The question to ask is how many frequencies do you need to support, and that’s a matter of capacity. If a new frequency is introduced into a cellular provider’s network, and that frequency isn’t needed in the enterprise, it’s not necessary to support it.

6. What type of maintenance does a DAS require?

A DAS generally requires minimal maintenance. If it’s being actively monitored, the DAS can provide indications that something may be failing so you can proactively manage that rather than responding to an emergency call. A DAS has a lifecycle of up to 10 years, depending on the venue requirements.