In-building radio and cell-phone communications support public safety, improve a building's maintenance and security services, and boost occupant satisfaction. But commercial buildings are poor antennas. The key is to find cost-effective ways to provide adequate coverage, as these two examples — Atlanta's Georgia Aquarium and Houston's Heritage Plaza, a 53-story, 1 million square-foot office building — illustrate.
Drowning the Radio Signal
Constructed of 2- to 4-foot thick, steel-reinforced concrete walls, the Georgia Aquarium in Atlanta stuffs radio signals. Adding to the challenge, the aquarium houses 76 electric water pumps and 7 million gallons of water behind 24-inch thick acrylic walls.
Recently, Alan Davis, director of safety and security, decided that radio communications would enhance the capabilities of the aquarium's 500 employees and 2,000 volunteers, and he asked engineers at Long Beach, CA-based Kenwood USA Corporation to evaluate options.
Kenwood conducted a radio frequency (RF) analysis to chart coverage needs and identified a spot above the main hall where an antenna could beam signals throughout the building and even reach workers outside.
Connecting the antenna to the base station proved challenging. "It required a long cable from the primary antenna to the trunking system," says Ken Fisher, Kenwood's project manager. "Because of the building's construction, it wasn't possible to use directional antennas for over-the-air links." Also, the cable runs were too long for coaxial cable to handle without amplification. Single-mode fiber optic cable solved the problem. Fiber already connected the building controls and security systems, and there was enough capacity for the radio system.
Aquarium employees and volunteers now communicate with Kenwood TK-3173 portable radios throughout the facility and grounds.
Heritage Plaza Accommodates First Responders and Cell Phones
Like most commercial buildings, Heritage Plaza's concrete, steel, and glass structure saps strength from RF signals, and requires in-building equipment to enable communication for property management teams and first responders. In addition, the owner wanted to accommodate the cell phone needs of the building's 25 tenants and their 3,500 employees.
"Our building staff uses Motorola 2-way radios, with a repeater that amplifies and retransmits signals on the 12th floor," says Jason Williams, senior project coordinator for the owner, Goddard Investment Group. "One radio is always tuned to Houston's emergency frequency."
While the Heritage Plaza systems satisfy local codes, an increasing number of jurisdictions are requiring owners to ensure that first-responder radio signals broadcast by outside antenna towers can be received inside commercial buildings. If the structure blocks or weakens signals, owners must install booster systems.
In addition to 2-way radio signals, Heritage Plaza also facilitates cell-phone communications. In effect, cell phones are full-duplex radios that operate on different frequencies and allow a two-way conversation in which all parties can talk and be heard at the same time. Like a first-responder system, cell networks use antenna towers and base stations to move signals around a city. Similarly, cell phone systems bring signals into a building with an outside antenna cabled to various antenna points inside a building. In-building cell phone antennas are called distributed antenna systems (DAS), which appear on each floor and amplify signals before sending them up and out of the building or down and into the building.
"Inside, amplifiers boost the signals, and multiple antenna points send signals throughout the building," says Dave Tuttle, director of sales with Manchester, NH-based Cellular Specialties Inc. (CSI). CSI installed an in-building system in Heritage Plaza to facilitate cell phones.
Such systems are not inexpensive. Industry observers estimate the cost of an in-building cellular system at $100,000 to $500,000, depending upon the building size and any cost-sharing arrangements. Owners, tenants, and cell phone companies each have an interest in enabling cell phone communications in a building. Sometimes everyone involved shares the cost. Sometimes the owner alone pays.
Why spend for cell service? "We want to provide an optimum, high-end work environment that will attract a high-end professional tenant base," Williams says. "Cell phone communications and Wi-fi have enabled us to secure major tenants with long-term leases."
Michael Fickes is a contributing editor with extensive experience in the security industry.
