AT&T selects LGCell for increased coverage at SAFECO Field

SAFECO Field, the new home of the Seattle Mariners baseball team, is built to resemble the great ballparks of yesteryear with its open-air atmosphere and real grass. A number of high-tech innovations have been added to further enhance the fan's experience. Perhaps the most visible of these is its retractable roof (weighing 22 million pounds), which allows fans to enjoy games during foul weather while still experiencing the atmosphere of an outdoor stadium. A number of other high-tech touches have been added, including a comprehensive scoreboard and video system (including the first LED technology in major league baseball) and amenities for disabled fans, such as an FM assisted listening system. However, there is one capability unique to SAFECO Field that fans cannot see, but can certainly experience firsthand-that is high-quality, highly reliable wireless communications from anywhere in the facility.

Every venue presents its own challenges to wireless communications, but public spaces have some unique characteristics that make them particularly difficult to service. SAFECO Field is a good example. The stadium is built primarily of brick, concrete, and steel—all materials that effectively block the transmission of wireless signals. The stadium consists of five different seating areas, ranging from the wide-open spaces of the upper level to the almost belowground confines of the field level. This architectural variety is aesthetically pleasing and ensures that each spectator has a great view of the game, but the varied spaces present a challenge to wireless system designers, who must adjust system attributes differently for open or closed spaces and for varying construction materials.

Fans and staff can make wireless calls from anywhere in SAFECO Field.

While propagating a wireless signal in a space like the main seating area is relatively easy, getting that same signal to penetrate hard-to-reach areas like the luxury suites or player locker rooms is a much more difficult task. Another factor that must be addressed is the need for a wireless system to be flexible enough to economically accommodate a varying population of users. At SAFECO Field, the number of people in the facility varies greatly, with a few dozen stadium personnel before and after games to as many as 47,000 fans during games.

AT&T Wireless Services was asked to design the wireless service for SAFECO Field. Although some areas of the stadium could easily be served by standard macrocellular base stations, portions of the facility required a different approach to ensure quality reception and consistently clear communications throughout the park. AT&T selected the LGCell™, designed and manufactured by LGC Wireless, to provide services on the field level, including locker rooms and VIP lounge. The LGCell system enables fans, players, and staff to make and receive wireless calls throughout SAFECO Field from the seating areas, VIP lounge, and the concession stands.

For AT&T Wireless, SAFECO Field represents a large concentration of both current and potential customers for its wireless services. AT&T also recognizes the potential value of SAFECO Field as an opportunity to showcase its services. "We're confident enough in the technology that we have an AT&T store in SAFECO Field where we sell our phones and service," says Vicky Oxley, vice president and general manager for AT&T Wireless Services. "We need to be able to demonstrate our products, and the LGCell helps provide the coverage [we needed in order] to do so."

The System
The LGCell system at SAFECO field consists of two Main Hubs, eight Expansion Hubs, 32 Remote Antenna Units (RAUs), and associated cabling. Because industry-standard cabling is used, the LGCell was simple to install. The system uses two types of cabling: multi-mode fiber-optic cable (between the Main Hub and the Expansion Hub) and Category 5 (CAT 5) twisted pair wiring (unshielded or shielded, between the Expansion Hub and the RAU). Multi-mode fiber is the same type of cabling used for Local Area Networks (LANs). Thus, it is commonly found in many buildings and, if there is already dark fiber installed in a building, it can be used for the LGCell. If multi-mode fiber installation is required, it is extremely inexpensive and easy to pull. In addition, cable runs as long as 1 km can be supported, which gives the LGCell system tremendous reach. CAT 5 twisted pair wiring is typically used for telephone sets. It is a very common cable type, very inexpensive, and also easy to pull.

LGCell Main Hub, LGCell Expansion Hub, and Remote Antenna Unit.

Other systems use either coaxial cable or a combination of single-mode fiber optic cable and coaxial cable. Because the loss is great when transporting RF via coax, the cable must be 1/2 inches to 7/8 inches in diameter (thus it is often referred to as garden hose coax"). As such, it is extremely difficult to work with, and if the cable is kinked at any point, the signal will be negatively affected. And again, because of the "lossy" nature of coax, the maximum cable run lengths are approximately 300 feet, inherently limiting the area a system using this type of cable can cover.

Single-mode fiber optic cable is generally used for outside-plant applications (ie, central office to central office) and is far less prevalent than multi-mode fiber in most buildings. Keeping this in mind, it is highly likely that systems using this type of cable might require cable installation. In addition, single-mode fiber is somewhat more expensive and has been known to be more difficult to install, due to the connectors.

The LGCell's remote alarming capabilities, provided by a rack-mounted unit that is placed in the same rack as the LGCell Main Hub, ensure that the system is easy to maintain. This unit, the Alarm Report Monitor (ARM), is connected to a remote PC via a dial-up connection. The PC is equipped with software that monitors the system, and a single ARM unit can support multiple LGCell systems. The ARM software on the PC displays the status of the LGCell components, enabling an operator to see the status of the entire system-even from remote locations. The ARM bypasses the need to wait for a trouble call; an operator can know where the problem lies prior to arriving on site. The system provides reports, alarm histories, and password protection.

LGCell Remote Antenna Unit, installed.

The LGCell is an extension of the public network, as it utilizes public wireless spectrum and is part of the public wireless network plan. There are two methods of LGCell deployment. In applications in which coverage within a facility must be improved, such as in SAFECO Field, a rooftop antenna is connected to an LGCell, and cellular signals from a neighboring macrocell are "re-radiated" throughout the facility the LGCell is installed in. But the predominant application is one in which both coverage and capacity are required. In this type of application, a radio base station is installed and connected to the LGCell, creating a public microcell with a unique set of public wireless radio channels, and delivering both wireless coverage and capacity within the LGCell coverage area. In all applications, because the LGCell uses public wireless spectrum, the coverage between the macrocellular coverage area and the LGCell coverage area is completely seamless and absolutely transparent to the wireless user. As a result, users can access all of the network's services and features, including wireless web capabilities, regardless of their location. And they do not have to learn any new access codes or instructions in order to do so.

What's Inside
The LGCell's double star architecture makes it extremely flexible and economical for both large and small areas, and superior in terms of reliability. With a double star topology, failure of a single component will not cause the entire system to be out of service. The Main Hub is connected to an RF source, such as a rooftop antenna or repeater, or a base station. The Main Hub converts the incoming RF signal into an optical signal, which it sends to the Expansion Hub via multi-mode fiber. The Expansion Hub then converts the optical signal to an electrical signal and transmits it to the RAUs via twisted pair (CAT 5) cable. The RAUs then convert the signal to RF and send it to the antennas, and finally to the wireless phone. For the returning signal, the reverse process occurs.

Each Main Hub can support up to four Expansion Hubs, and each Expansion Hub supports up to four RAUs. If additional coverage is needed, multiple Main Hubs can be joined together to form a larger, single system.

For example, take a system with one Main Hub, four Expansion Hubs, and 16 RAUs that initially required one channel (from a base station) to provide adequate capacity. Simply adding another channel from the base station and one additional Main Hub can double the capacity for this system. Two of the Expansion Hubs and their associated RAUs would then be connected to the second Main Hub. The coverage area has now been "split" into two cells, each containing one Main Hub, two Expansion Hubs and eight RAUs. Each cell now has a single channel serving it, and the entire area now has two channels. None of the original Expansion Hubs or RAUs need to be moved to accommodate this change, and no system redesign is needed.

System Design
The LGCell system's architecture and basic RF design makes it easy to implement. The first step is to perform a preliminary system design based on the floor plans of the facility. Next, an engineer must look at a number of site aspects when implementing a new system. First, the configuration of the facility must be evaluated. Is it multi-story; are portions of the facility underground; is it a campus, where a number of buildings are involved; is the entire facility going to be covered, or only certain areas? These basic characteristics significantly impact both the system design and installation. Second, what are the building materials? Wireless signals can pass through glass with ease, but 12 inches of steel and concrete can stop a signal cold. And other specific characteristics, such as elevator shafts, must be taken into consideration when designing a system. An engineer must also determine the optimal locations for placement of the RAUs and antennas, in order to ensure seamless coverage throughout the specified area, while allowing for the location of wiring closets and optimizing cable runs.

Conclusion
The LGCell has been successfully deployed in many facilities worldwide, including shopping malls, corporate offices, universities, hospitals, hotels, retail stores, parking garages, convention centers, and airports. It has been used to provide capacity and/or coverage in facilities ranging from small retail establishments to the tallest buildings in the world, the Petronas Twin Towers in Malaysia.

For the SAFECO and Mariners staff, the ability to communicate regardless of location is important. Now, staff can respond to routine inquiries or urgent calls from anywhere in the facility.

Bob Aylward, Mariners vice president of business and sales, recognized the need for high-quality communications in the park. "We knew we needed a wireless office system at SAFECO Field, but the stadium severely limited coverage in vital areas," he says. "The LGCell gives us the consistent coverage and clarity we need."

For Mariners fans, the ability to use their wireless phones is a welcome addition to the many other amenities of SAFECO Field. They can contact a business associate to arrange a meeting after the game, or make dinner reservations to celebrate a victory. As an additional service to fans, AT&T also offers an "emergency call" service, enabling fans to have a wireless phone brought to their seats to take or make important calls.

Most carriers originally focused on providing coverage and capacity "outside" (ie, on the freeways and city streets). Now, they are trying to provide service "inside"—in both private spaces (such as offices, hospitals and hotels) and in public spaces (such as airports, convention centers, and sports arenas and stadiums). These areas attract large numbers of mobile phone users, particularly business people who are heavy users of wireless services and for whom reliable, high-quality communication is critical.

It is absolutely in the wireless carrier's best interest to provide network extensions in these "non-traditional" venues, as this will result in a higher level of customer satisfaction (thereby increasing customer retention) and also drive additional usage minutes on their network. For the carrier, the net result is increased revenue. For the user, the result is more reliable, more ubiquitous wireless service, and a better all-around wireless experience.

David Cutrer is co-founder and vice president of marketing at LGC Wireless, San Jose, Calif.

Reprinted with Permission from PCS Systems and Technology Magazine, March 2000.