In-building coverage is a must-do
Cell phones and mobile devices such as the BlackBerry have become the primary means of communication for many workers worldwide. As a result, reliable in-building wireless coverage now is a necessity for many firms, a requirement driven by both the need to stay constantly connected and the uptake of 3G cellular technology and high-speed/high-bandwidth data applications.
“You won’t see a lot of people on street corners downloading files,” said John Spindler, vice president of marketing for LGC Wireless. “They’ll be sitting in a conference room, [or] in a foyer downloading information.”
Spindler cited statistics generated by Japan wireless carrier NTT DoCoMo that indicate 70% of all mobile calls are received or initiated within a building, with only 30% occurring outside. “Much of that number can be attributed to mobile applications,” he said. “While it may have been adequate to blast into buildings with towers [for voice], that’s not an adequate solution for [data applications].”
LGC Wireless has been in business for more than 10 years and claims more than 5500 deployments worldwide, including numerous airports, sports arenas and Las Vegas properties. It historically has sold its solutions to wireless carriers such as Sprint Nextel, T-Mobile and Verizon Wireless, but that’s starting to change with enterprises now willing to foot the bill for an in-building solution.
“The enterprises are now seeing that mobile devices — both for voice and also for some data apps — are becoming the number one means of communicating within the organization. There are a lot of RFPs for in-building wireless, with business cropping up in vertical segments,” Spindler said. In the past, wireless carriers would purchase in-building wireless systems and install them into buildings to improve cellular coverage as a part of a larger contract with an enterprise, he said.
One facility expanding its use of in-building systems to improve coverage is the Lawrence Berkeley National Laboratories (LBL), the oldest of the Department of Energy’s national laboratories. The “Hill,” as employees call it, is located on a 200-acre site consisting of about 110 buildings above the University of California’s Berkeley campus and overlooking the San Francisco Bay.
“A good chunk of the buildings are built into the hillside,” said Richard Gregory, LBL’s telephone services center group manager. “That’s where most of our cellular coverage problems come in.”
LBL has been working with Cingular and LGC Wireless for nearly four years, and demands for better in-building coverage have evolved over time. “Not all buildings had [in-building] coverage,” Gregory said. “As we reorganize and move people around, that changes.”
As the primary cellular service provider to LBL, Cingular has made some investments at the laboratory in order to expand building coverage. “We spec out what buildings need, depending on what demand is,” Gregory said. “We tell Cingular, and they come out and see the same problem that we do. So far, they have not balked at increasing the [in-building] coverage for us.”
For delivering data, active electronics are the way to go, Spindler said. “[With] coax, there are some issues,” he said. “It’s inherently ‘lossy,’ like your garden hose. The longer the hose, the lower the pressure; [similarly], the longer the run of coax, the lower the signal at the end. From a performance perspective, the performance is not always predictable due to the length of coax on the end of the antenna.” Installing coax cable also is very time-consuming and difficult to install in older venues.
In contrast, LGC’s solutions mirror the topology and functionality of an Ethernet LAN, using standard building cabling to deploy encoded boxes for end-point radio frequency (RF) distribution that are designed to be mounted into the same rack with the IT router. The system can be managed through a Web interface, and it supports the SNMP protocol for network monitoring.
“The [in-building] system we build is a zero-loss system. Whatever you put in the main hub, you get out of each antenna point,” Spindler said.
Distribution runs of up to 6 kilometers can use either multimode or single-mode fiber, which brings signals to a single main hub through either a base station or a repeater. The distribution hubs, typically located in telecom closets, are fed with standard Cat 5 or Cat 6 twisted-pair Ethernet cable. Finally, signals are moved in and out over standard Ethernet cable to multi-band end-point remote access units (RAUs). “Think of [RAUs] as [wireless access points], but they don’t have radios; they have power amps,” Spindler said.
Using both standardized Ethernet cable and active electronics offers several advantages over coax-based systems and hybrid in-building systems in addition to avoiding the aforementioned signal losses associated with such systems, according to Spindler. “[Ethernet is] an inexpensive cable. Even an in-house IT department can pull it.” In contrast, coax cable costs continues to go up as the price of copper rises, he added.
As a result, LGC’s solution delivers a consistent coverage area from each installed antenna and RAU, so a coverage plan can be designed by overlapping circles around each RAU, similar to how a cellular network is designed. Each RAU covers up to 10,000 square feet in highly dense construction, such as hospitals and other buildings with a lot of walls. In open space without walls or other obstructions, such as warehouses, an access unit can cover up to 125,000 square feet.
It should be noted that some believe active electronics systems introduce significant lag time in processing RF into a digital form and then reconverting it for broadcast, a criticism Spindler labeled inaccurate. “I can’t tell you what that number is, but it’s nanoseconds,” he said. “It’s negligible. If it was an issue, we wouldn’t be doing the business we’re doing because the carriers wouldn’t accept it.”
Determining where cellular in-building coverage needs improvement is a job that will likely become much more automated in the future. Schema has developed the Mentor radio access network (RAN) optimization solution to help cellular carriers better determine network coverage and load by using information collected from subscribers’ mobile devices.
“When going into in-building solutions, no prediction and drive test can provide any quality analysis,” said Gur Lavie, Schema’s director of product marketing. “Prediction and drive tests are good for outdoor and moving elements. If you try to analyze any enterprise [in-building] data use, a drive test is worthless. Today’s predictions aren’t accurate enough.”
Mentor analyzes the constant stream of data that is recorded as cellular devices communicate with a carrier’s base stations, allowing service providers to get real-world, real-time data on cell load and footprint coverage, especially in-building coverage. Currently, Mentor accurately reports user location within 200 meters for CDMA systems and 50 meters to 80 meters for UMTS systems, solely through the cellular network and independent of GPS or other position-location technologies.
“With GPS, you can get to one- to two-meter accuracy, but carriers are reluctant to do this without getting subscriber permission due to the privacy issues involved,” Lavie said, adding that carriers use Mentor’s analysis to map out cell site dead zones and hot spots in an automated fashion.
Meanwhile, demand for better 2.4 GHz Wi-Fi coverage also is growing. “We’ve done a lot of wireless LAN installs,” Spindler said, citing the coming arrival of dual-mode cellular/Wi-Fi handsets. Because of its higher-frequency range, 2.4 GHz requires a separate in-building network with more distribution hubs and optimum antenna placement compared with cellular networks.
Wavion has taken a different approach to extending Wi-Fi coverage, combining several technologies to produce more powerful and intelligent metro Wi-Fi equipment. “We’ve designed an access point specifically for the outdoors that has a better link budget, allowing devices to connect at longer ranges,” said Alan Menezes, vice president of business development. “We use six radios and six antennas and do a lot of digital signal processing. We do it in such a way [so that] the signal coherently combines to reach the client location.”
The multi-radio/multi-antenna solution provides better performance by delivering up to 14 dB gain and allows the signal to penetrate through walls. This extends the reach of external metro Wi-Fi to offer some level of indoor coverage. “Certainly, you can sit in a coffee shop and not have direct line-of-sight,” Menezes said. “If you have multiple walls, that’s a different story.”
Wavion’s technology currently is packaged for the 2.4 GHz band, but it can be applied to different frequencies, including 5.8 GHz and 4.9 GHz. “We’re studying the market [for 4.9 GHz] and have done some testing in metropolitan areas,” Menezes said. “We haven’t made a conscious decision for 4.9, but we’ve seen a lot of interest in it.”
