Improving Wireless Coverage
- By Janet Wiens
- August 1st, 2009
We are accustomed to wireless coverage, particularly for cell phones, that works well almost anywhere at anytime. However, there are still many areas where coverage is spotty, and college and university campuses are not immune. Students and faculty want full wireless access whether they are outside or inside a building. Administrators want coverage for convenience but also as part of an institution’s emergency warning system. One solution is to install a digital antenna system (DAS). DAS is integrated with existing wireless systems to provide coverage that will keep everyone happy.
How It Works
In simplest terms, a DAS is a series of distributed antennas that radiate a cellular signal from a central source, which can either be an on-site station deployed by wireless carriers or an external antenna that grabs the signal from an outdoor network. The equipment of some manufacturers involves the installation of a hub, remote antenna units (RAU), standard cabling, and antennas, while others involve a main hub with coaxial cabling and no intervening hubs. In either case, the hub grabs the wireless signal from either an external antenna that obtains it from an existing cell tower or from a small base station deployed on the premises, and converts the signal from RF to an IF signal and then back to RF at the RAUs. (Some systems using coaxial cable without intervening hubs do not convert the signal from RF to IF.) The signal flows through the system, out to the antennas, and on to the user. The selected system should ideally support both 800 and 1900 MHz frequencies.
John Spindler, vice president of product management for ADC, said that wireless needs to continue to evolve. “Wireless is replacing wired lines and used to be voice only,” he said. “We are experiencing and will continue to experience an explosion regarding this technology and its associated capabilities.”
Students, faculty, and staff rely on tools that require wireless. It provides a lifeline to families, serves as a mechanism for accessing class assignments, and relays emergency notifications. Wireless coverage and access must be available throughout a campus, which can be challenging when a campus is very large, cell towers are not close, or when buildings have thick walls or lots of structural steel.
“DAS allows officials to target areas where they need to boost coverage,” said Spindler. “It’s an efficient and cost-effective approach that can be installed using fiber-optic or single- or multi-mode cabling that is already in place.”
Selecting a multi-carrier solution is critical, and Spindler said there are six key elements to consider regarding the use of DAS:
- Phasing. Evaluate current and future needs and develop a three- to five-year plan that will allow DAS to be installed and expanded over time.
- Cabling. Determine if the system being considered can work with standard cabling, or if coaxial cabling must be installed; a step that will increase costs.
- Costs. Determine the turnkey cost — equipment, cabling, installation, and maintenance for the proposed system(s).
- Expansion. Look for a system that can be easily and economically expanded as needs change.
- Building evaluation. Work with the DAS providers being considered to determine a basic cost for building installation based on an analysis of floor plans. A site visit may also be preferred/required.
- Vendor relationships. Ask the potential DAS provider(s) about their relationships with wireless operators. Determine if they can help broker a deal with carriers as required.
Spindler noted that wireless carriers historically want to improve service to gain or retain customers. For this reason, they are usually very open to partnering with college and university officials to help boost coverage.
Adding More Bars
Ave Maria University in southwest Florida opened its new campus in 2007, and its initial wireless coverage was very poor. The nearest cell towers are two-and-a-half and six miles away, and campus buildings are constructed to withstand a Category 5 hurricane, which means that walls are two-ft. thick in some cases.
Wally Hedman worked for the company that handled the initial build-out for the campus’ cabling, and was later hired by the University as the operations manager. “When I joined the staff, wireless users could get two bars outside and no bars inside our buildings,” he said.
Hedman was familiar with DAS, and initially installed a system in the library as a test case. The results produced two bars within buildings; an improvement, but Hedman knew that he could achieve better results.
The next step involved the installation of a different system based in the library, which included a main hub, RAUs on each floor, and a roof-mounted antenna to relay the wireless signal to the cell towers. The solution achieved the desired results, and the University has continued to expand the system over the existing single-mode fiber to meet their changing needs as new buildings come on line and enrollment increases.
“The first installation cost us $15,000, and provided us with five bars of service in all target areas,” Hedman said. “Each new building costs approximately $8,000, and we’ve invested approximately $75,000 to date as we’ve added hubs and associated equipment. The DAS solution has worked very well for us.”
Wireless Coverage at Duke
Bob Johnson, senior director of communications infrastructure at Duke University, faced challenges similar to those at Ave Maria University. He needed to increase wireless penetration into the two hospitals on the campus while also increasing overall wireless coverage.
“We have multiple carriers serving our campus, and needed a carrier-neutral solution,” Johnson said. “The results that we achieved with our first installation were good, and we will continue to expand the system as needed.”
Duke has a hybrid system that involves outdoor and in-building equipment, which Johnson said is more economical. Outdoor components currently use seven towers that are also part of the University’s outdoor alert system. This approach helped control the budget while also addressing aesthetic requirements, since the antennas are small enough to be located on the towers and are difficult to see unless an individual is really looking for them.
The First Step
Cricket Communications wanted to expand its coverage on San Diego State University’s campus, and DAS was again the answer. “Cricket came to us three years ago and expressed a desire to increase wireless coverage,” said Riny Ledgerwood, director of communications and computing services at SDSU.
The carrier was able to use the existing DAS base in the library and the fiber-optic cable owned by the University. Cricket covered all expenses associated with the installation and continues to pay SDSU for leasing use of the fiber-optic cable. “Any solution for increasing wireless coverage must obviously be a good business decision for the carrier, which this was,” Ledgerwood said.
She also notes that DAS antennas work well when aesthetics are a concern. “We have strict aesthetic requirements, which is true on many campuses. The exterior antennas, in our experience, are unobtrusive, which was important to us. Our experience with DAS has been very positive in every aspect.”