By Chad A. Safran
Published in the November 2008 issue of Today’s Facility Manager
When Alexander Graham Bell created the telephone, he made a simple statement to his assistant, Thomas Watson: “Come here, I want to see you.” Watson heard the request and followed the instructions. It’s a good thing the pair was not trying to speak to each other using mobile phones from the opposite sides of a large office building. Otherwise, Bell would have been the first to utter one of modern society’s most frequently spoken quotes, “Can you hear me now?” and Watson would have heard some words and static and then pressed the end button on his phone.
It is a situation to which many facility managers (fms) and their employees can relate—poor indoor cellular phone reception. It is a situation that can be frustrating and infuriating since quality communication service could be the difference between solving a problem in seconds or having it get out of control in that same amount of time.
Is This Really Necessary?
In smaller facilities (buildings less than 20,000 square feet), reception is likely not an issue since signals from the macro network usually are able to move from outside to the inside. However, the mere size of larger buildings blocks or weakens cellular signals as users move away from the outer windows to the middle of the building. A facility with an underground area or one with many cellular users may also suffer from reception issues.
Technology interference may cause signal disruption because of too much electronic equipment in a tight space, such as in a server room or an enclosed office. Older buildings with large amounts of stone and concrete were never designed to have to deal with wireless issues.
A solution to this issue is for fms to have a distributed antenna system (DAS) installed to assist not only weak cellular phone signals, but help improve wi-fi connections to smartphones and laptop computers. DAS can also assist with paging, maintenance, and public safety communications infrastructure, which is useful on a larger campus setting.
A DAS provides a bridge between the interior and exterior environments by connecting to several wireless services and then redistributing them through the locations in which the DAS is installed. In the building, small powered antennas receive signals routed through fiber cable and are connected to a DAS control unit, which then redistributes the signal to several interior locations.
Outside, an external antenna is also hooked up to the DAS unit. The DAS facilitates communications from the inside and outside.
“DAS eliminates ‘dead spots’ for cellular service inside a building,” says John Spindler, vice president of product management for ADC’s in-building systems and a 20-year veteran of the telecommunications industry. “It makes it possible for occupants to rely on their phones and laptop broadband cards for stable connectivity. They are also very flexible and can be easily expanded to accommodate new construction or building changes.”
Costs And Concerns
While installation of a DAS can help reduce complaints about poor or non-existent cellular service, improve productivity, increase the value of the property, or potentially increase rent/lease revenues, it may not work for every fm. Costs run about 20¢ to 50¢ per square foot and installations can take anywhere from several days to many weeks.
Each project is a custom one, so fms need to work out agreements with carriers and vendors on how the DAS is created. A variety of factors, other than building size, need to be taken into consideration when installing the system.
- Building coverage: Should the DAS service take into account the whole building or just a certain section?
- Time constraints: When can the work be done? Certain venues require work only be done at night.
- Security: Some facilities, such as airports, require security guards to accompany contractors.
- Building material: Older structures may need asbestos abatement.
- Building topography: A wide open facility, such as a warehouse or manufacturing plant, needs relatively few antennas to cover it, while a dense environment, such as a hospital, requires more antennas.
- Frequencies/carriers: Fms need to decide which ones must be supported.
There are other expenses that must be considered, according to 40-year wireless industry veteran Dave Kaun, chief technology officer for Elert & Associates, a Stillwater, MN-based technology consulting firm. “There is the equipment to get the exterior signal into the distribution system,” Kaun says. “There are also two hidden costs: hiding the antennas and managing the system.”
As with most communications systems these days, an fm must take into account security issues when installing a DAS. While each carrier frequency is licensed and transmissions are usually all digital, (meaning the cellular signals are protected), the wi-fi factor presents an issue.
“Anytime you use a wireless system, there are security risks if it is connected to your facility’s network,” says Tom Condon, RPA, FMA, of Chicago, IL-based System Development Integration. “If your DAS is connected to the facility network (in the case of a hybrid wi-fi/cellular DAS), you must use network security techniques like VLAN (virtual local area network) to ensure that hackers can’t get into your network.”
Something Old Is Something New
Basic DAS technology has been around for some time, but it has evolved. Older set ups necessitated a separate network or set of electronics for each carrier supported; now, the better systems support more than one carrier frequency in a single system.
Fiber optics is now used more often in the distribution system, and the presence of more electronic filtering capability allows for dynamic changes in bandwidth and frequency. Additionally, newer systems use thinner cabling, which is cheaper and easier to deploy.
With the proliferation of new digital services, such as 3G and 4G cellular broadband, DAS may be an increasing requirement for more fms. This is because these wireless services generally use higher frequencies that weaken quicker than lower frequency services such as GSM or CDMA as they are being transmitted.
“These new wireless technologies are all about delivering wireless data,” says Spindler, whose Eden Prairie, MN-based company has deployed more than 11,000 DAS systems worldwide. “Most wireless data use will be indoors so it is becoming increasingly imperative that in-building coverage is a key element of the wireless network.”
One such DAS solution was installed at the Hartsfield-Jackson Atlanta International Airport (HAIA), the world’s busiest passenger airport (serving more than 83 million passengers per year). The DAS was used to help evenly distribute wireless coverage throughout the facility, without signal loss, no matter how far from the carrier base station. The installation was the third part of a three phase, four year, $11 million telecommunications infrastructure upgrade.
The set up used eight InterReach Unison systems from LGC wireless (now part of ADC) that included 36 main hubs, 96 expansion hubs, more than 500 remote access units, and over 700 ceiling mounted antennas. The system can handle a capacity of nearly 70,000 calls per hour.
Most fms don’t need to worry about handling that level of call volume within their facilities. However, clear cellular signals are important to fms who need to get in touch quickly with a vendor, staff member, or department manager from anywhere in their buildings. So how can they ensure the call goes through? A DAS is one way to help anyone hear them now.
This article was based on interviews with Condon, Kaun, and Spindler.
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Topic Tags: Digital Antenna Systems