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01/25/2013

How to Boost Cell Phone Coverage in Buildings

Assess the nature of your signal problem to develop a solution

By Christopher Curtland
 

It's a signal problem.  In-building wireless systems can boost cell phone coverage and prevent dropped calls and spotty coverage.

Occupant complaints about poor cell phone signal can be as nagging as cell phone ringtones. But dropped calls and spotty coverage don’t happen on a whim. They are signs that you should pump up the signal within your facility.

In-building wireless systems will help answer the call. The type of solution depends on the nature of the situation. Take these steps to find the right one.

Pinpoint the Problem
Poor coverage can be the result of several factors.

“When you get into densely packed buildings, very large facilities, or those that house a large number of people, then you should consider an in-building solution,” explains Chad Townes, VP of AT&T’s antenna solutions group.

Older types of construction using concrete, brick, and steel are notorious signal killers, which was part of the problem at Chicago’s Merchandise Mart.

“We have a 4.2 million-square-foot building that was built in the 1930s,” says Will Wong, the Merchandise Mart’s IT director. “Cell phone towers simply cannot penetrate into our building.”

The Merchandise Mart is the cocktail of coverage conundrums, because in addition to its size and old construction, it accommodates over 30,000 people every day, with occupancy reaching over 50,000 during tradeshows.

“People do business on cell phones. They make transactions, do research, and send and receive email,” Wong explains. “About two years ago, I started hearing rumblings about demand for better cell phone signals within the building.”

Is cell phone coverage in your building spotty? Finding a solution requires reaching out to manufacturers, wireless solution providers, and the major carriers. “There are a couple routes you can take,” Wong says. PageBreak

Select a Solution
There are two types of in-building wireless solutions that boost signal: passive and active systems. The former achieves stronger coverage by strengthening the existing signal from the nearest cell site (tower). The latter allows for increased capacity because it essentially constructs a miniature cell tower specifically for the site.

A passive system is also referred to as repeater-based. It entails an outdoor antenna pointed toward the nearest cell site. The antenna catches the off-air signal from a tower and sends it via coaxial cable to a bi-directional amplifier (repeater) that strengthens the signal and sends it along to antennas throughout the building.

An active system is also commonly referred to as a distributed antenna system (DAS). A DAS starts with a front-end, central distribution unit.

“This is literally the same equipment that would be at the base of a cell tower,” Townes explains. “The difference is instead of going up cable to the top of the tower and hitting an antenna, the DAS equipment breaks that signal down and sends it through fiber to multiple zones.”

Passive systems are best for areas where the network has available capacity, such as suburban or rural areas, but likely aren’t ideal for densely packed, urban environments.

“They have been very common practice, but we’ve started getting away from those, because they don’t add any capacity to the network. It just strengthens the existing signal from the tower inside the building,” Townes says. “If the network is already overloaded, a passive system puts more stress on it. It robs Peter to pay Paul.”

A DAS solution, on the other hand, is like your own personal tower inside the facility. For this reason, DAS networks are ideal for large airports, convention centers, and even NFL stadiums, says Kelley Carr, president of the custom solutions group at Cellular Specialties, Inc, a national systems integrator for DAS, Wi-Fi, and public safety solutions.

“In large, public venues, there are so many people to accommodate,” he says. “A DAS gives dedicated capacity to the building.”

The Merchandise Mart’s system is a DAS. Its front-end equipment is a neutral host, meaning that other competing carriers like Verizon and Sprint can hook their radios onto it and send out their signal. It requires a 2,000-square-foot space, located on the 18th floor’s northwest turret.

The space needed for the DAS’s location must account for the central distribution unit and allow for multiple carriers to hook their radios to it, and thus the required area can range from 100 to over 4,000 square feet, depending on facility size, Townes says. PageBreak

Pricing and Payback
The Merchandise Mart situation is unique because AT&T funded the installation, although other carriers are in the process of coming onto it. AT&T builds neutral host solutions so building owners can avoid the burden of needing space for each carrier to have its own network.

“It’s a landmark building so all carriers want to be here,” explains Wong. “Their revenue comes from voice and data usage, so they want to provide signal to their customers in our building.”

Other property owners may want to ensure signal strength because it increases productivity or helps retain and attract occupants (see case studies). “Our leasing folks use the DAS as a sales point,” says Wong.

Those benefits can help you rationalize a sizable investment like this.

“It’s a pretty common practice for building owners to fund the construction of the DAS front-end equipment, and then the carriers will come in after the fact and connect their radios to it to distribute the signal inside,” explains Townes. “It becomes a shared cost model where both parties benefit. There’s an opportunity to share in the cost recovery for the system.”

Conservative estimates of cost for installation range from $0.50-1.50 per square foot depending on the number of carriers on the system, if Wi-Fi is also included, and whether emergency or security frequencies must be sidestepped, according to CSI.

“We take a very consultative approach,” explains Carr. “We perform an analysis, give some budgetary numbers, and look at things from a cost perspective. There are options.”

Upgrades and Upkeep
Once you have a system up and running, it’s important to keep an eye on it to make sure it’s operating at peak performance. “Sometimes a person may be blocking an antenna and not realize it, so we work with tenants and the designers and might have to move an antenna 10 feet this way or the other to accommodate what’s going on in the building,” Wong says.

If a systems integrator implements your solution, a service level agreement dictates what will happen in the event of a hiccup. “Some may just want our technical support number and we can respond to an issue in a couple days,” Carr says. “Other customers, like hospitals or stadiums where communication is critical to the day-to-day operations, may want the problem fixed within hours.”

If a service provider created the solution, it monitors the solution itself. “We’ve got an operations center and problems show up as elements in our network just like any cell tower would,” explains Townes.

The cell phone network very recently shifted from 3G to 4G, which impacted networks such as these. “People want to keep up with the latest technology, and an upgrade like that would require some new equipment on the front-end,” says Carr.

Regardless of the route you take, service providers and systems integrators will help you along the way.

“You definitely want to partner with the carriers in your area to find solutions,” says Townes. “Everyone can collaborate to see what works.”

 

Chris Curtland christopher.curtland@buildings.com is assistant editor of BUILDINGS.