Using cabling systems to support in-building personal wireless

The wires behind wireless connectivity are enabling dead-zone-free facilities.

The wires behind wireless connectivity are enabling dead-zone-free facilities.

by PATRICK McLAUGHLIN

It used to be that consumers readily accepted cellular voice service would be far less reliable than wired voice. How commonly would you be on one end or the other of the following type of conversation in which at least one party was on a wireless phone? “I’m going into a tunnel; I’m going to lose you. I’ll call you back.” Even today, it is common to see wireless users inside a building receive a call and head to the nearest exit not out of courtesy to those around them, but to get to either a window or outside where the signal will be strong and the transmission clear.

That is changing as wireless users raise their expectations of connectivity anywhere and service providers work to oblige. At the same time, “mobile devices are becoming the preferred means of communications in the world,” says John Spindler, vice president of product management with ADC (www.adc.com). For many users the mobile phone rings far more often than the desk phone. Spindler further explains, “Think about the initial rollout of cellular. It was all about covering major highways—mobility, people being able to stay connected when they were in an automobile or on the move.” That prompted the deployment of wireless antennas in tunnels and other places where mobile calls frequently would be dropped.

Changing landscape

Today the landscape has shifted even beyond that. With wireless being the preferred medium for personal communications, access within a building is just as important as access while mobile. “The shift is to portability,” Spindler says, as today’s wireless users are often sitting in a conference room or in an office reception area waiting for a meeting to begin. A majority of mobile traffic comes from inside, not outside buildings, yet cellular networks were originally designed to accommodate outdoor rather than indoor users.

Add to this the shift from voice to data traversing wireless networks and it is evident that cellular networks were by and large built to accommodate a certain type of user (outdoor) communicating in a certain way (voice), and today are being required to accommodate different users (indoor) communicating differently (data). As a result, buildings can be significant dead zones for wireless users unless those buildings contain wireless communications systems—entirely separate systems from 802.11-based wireless local area networks.

The changing characteristics of wireless use has forced service providers to change how they build their systems. “There has been a shift in operators’ building out their networks as they go from 2G to 3G and 4G,” says Spindler. “These shifts are making for smaller cells, with more emphasis on covering areas of high user density such as airports, convention centers, and college campuses. That all places demands on in-building coverage. Large buildings can have a significant impact on overall network performance.”

Wiring for wireless

Many enterprise users have seen the benefits of installing in-building solutions in their facilities and have done just that. ADC offers the InterReach suite of distributed antenna systems (DAS) for in-building wireless coverage. InterReach Unison is often deployed in dense, high-traffic environments such as convention centers, sporting venues, and airports. InterReach Fusion is a multi-band system often used for in-building wireless connectivity in campus environments and for areas greater than 250,000 square feet.

In March CommScope (www.commscope.com) introduced its Wired for Wireless Solution, aimed at owners and developers of new buildings and campuses. The system allows them to provide, in advance, the infrastructure necessary to eliminate weak or blocked signal areas from the outset and prepare them for better wireless coverage over the structure’s lifetime, CommScope says.

“Our Wired for Wireless Solution provides a necessary foundation to ensure exceptional wireless coverage throughout the building’s lifecycle,” says Morgan Kurk, senior vice president of intelligent buildings with CommScope Enterprise Solutions. “The employees, suppliers, customers, and general visitors that occupy these buildings and campuses rely on dependable connectivity in all aspects of their business and personal lives,” he continues. “A smartphone is becoming just as indispensable for business operations as electricity and plumbing are for the building. We believe the Wired for Wireless Solution is the most sensible way to better prepare a building or campus for its wireless needs, today and tomorrow.”

When introducing the system, CommScope pointed out that energy-saving features such as heavily insulated walls and windows that reduce energy costs in new buildings can also make it difficult to receive outside wireless signals.

“The Wired for Wireless Solution is a much-needed evolution to the way wireless infrastructure is implemented in enterprise buildings,” Kurk continues. “Instead of waiting to find coverage trouble areas, CommScope’s cost-effective platform for uniform coverage provides building owners with a low-cost solution before the high-cost problem presents itself. This capability not only allows people to stay connected and achieve more in their day-to-day lives, but long-term it can help enterprises reduce infrastructure costs by embracing in-building wireless systems for their communications needs.”

Multiple technologies

There are differences between CommScope’s Wired for Wireless and ADC’s InterReach systems. One significant difference is the cabling types used to support the systems’ wireless antennas. Wired for Wireless includes two, half-inch 50-ohm coaxial cables from the Andrew Heliax cable family as well as N-type male coaxial connectors. The cables are part of a complete system that also includes two antenna types—directional and omnidirectional—as well as coaxial connectors and cable-management apparatus.

ADC’s InterReach systems can use twisted-pair, multimode fiber-optic, and/or RG-6, RG-59, and RG-11 coaxial cables. ADC emphasizes that these cable types are frequently found inside buildings and that its InterReach systems can leverage existing cabling runs when they are available.

Each company has made positioning statements pointing out the benefits of their respective systems and the cabling infrastructures within them. The differences exist because InterReach systems are active DAS technologies while Wired for Wireless is a passive DAS technology. Active and passive DAS can be compared to “fat” and “thin” wireless access points, in that antennas in active DAS include active electronics while antennas in passive DAS do not.

The decision to implement an active or a passive DAS, like many networking decisions, will be influenced by a multitude of factors specific to the user site.

Who pays?

Both ADC and CommScope mentioned a recent business-model trend that has the enterprise, rather than the wireless carrier(s), bearing the cost of an in-building wireless system installation. In a frequently-asked-questions document CommScope issued when it announced Wired for Wireless, the company said, “Faced with rising infrastructure costs throughout their network, carriers may be unwilling or slow to deploy active equipment for in-building wireless coverage if they also need to deploy cables and antennas. Additionally, the Wired for Wireless provides the enterprise with options to support carrier-owned and/or enterprise-owned equipment as applicable.”

ADC’s Spindler explains that over the last few years enterprise users have been more willing to pay for the system, at least in part because in that situation the enterprise does not have to make a long-term commitment to any particular carrier.

CommScope also produced a white paper that makes the case for its Wired for Wireless Solution and also discusses some practical measures for installing the system. It reads in part, “To ensure uniform coverage, the indoor antennas must be evenly spaced throughout the building, with no perimeter antenna further than 20 feet from an outer wall. The outer ring of antennas can be directional, although omnidirectional antennas will also work, pointing back into the building, almost as if the building is being covered by a blanket of invisible signals. In this way, the signals from the indoor antennas will swamp out the signals from the outside environment, forcing all devices in the building to gain network access through the building’s system, thus making their experience uniform and controllable.”

CommScope also recommends spreading antennas evenly throughout the building in a grid pattern that is much the same as that used for 802.11-based systems. The company says the ideal is to place antennas at 100-foot intervals. The paper goes into further detail with recommendations for antenna placement in specific areas of buildings including elevator cores and stairwells.

Regardless of the differences between ADC’s InterReach and CommScope’s Wired for Wireless systems, they both aim to fulfill the emerging and growing needs of enterprise end-user organizations to support wireless personal communications as a business necessity.

Editor’s note: Quotes and information from John Spindler used in this article came from our webcast seminar entitled “Enterprise wireless – LANs, voice, and cabling.”

Patrick McLaughlin is chief editor of Cabling Installation & Maintenance.

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