The unlicensed portion of the U.S. radio frequency spectrum represents just one-tenth of 1 percent of the total bandwidth allocated for communications, but this thin slice has made the current boom in wireless LANs possible. Because WLANs use the free spectrum, companies can set them up without the hassle or expense of going through the U.S. Federal Communications Commission's licensing process. But WLANs aren't the only networking technologies leveraging the free spectrum. Corporations are also using fixed wireless systems and services from wireless service providers to extend connectivity beyond the LAN.
Fixed wireless systems use the same 2.4- and 5-GHz bands used by WLAN products. But highly focused directional antennas support wide-area connections over distances measured in miles, rather than the hundreds of feet WLAN devices cover. Fixed wireless devices let enterprises tie together regional or metro-area office buildings using a privately owned and operated broadband network. The systems can support point-to-point Ethernet bridging or IP-based multipoint packet routing. And some products also offer a separate T1 channel, eliminating the need to lease physical T1 circuits for digital voice traffic.
Companies that don't want to set up their own systems may find similar wireless offerings from service providers. A new breed of wireless Internet service providers (ISP) uses the unlicensed frequency band to offer last-mile broadband services at rates lower than those that telephone companies charge for comparable leased-line services. Service providers offer data rates ranging from a few hundred kilobits per second to 54M bit/sec. or more. And in some remote locations, as well as in parts of some metropolitan areas, wireless ISPs are the only broadband alternative.
Building a Network
York, Pa.-based Kinsley Inc. opted for a fixed wireless WAN that serves 1,500 workers in multiple locations. Patrick Kinsley, a project co-coordinator at the construction and commercial property management firm, says the company had to accommodate large data files generated by computer-aided design (CAD) workstations, as well as growing voice traffic. It also needed a way to connect telephone and computer systems in office trailers at construction sites into back-end systems more quickly than the several weeks it took to provision lines from the local telephone company.
Business Information Group (BIG), the York-based systems integrator that hosts Kinsley's data center, designed the fixed wireless network, which serves 1,500 workers in eight locations. Some 22 other companies housed in buildings Kinsley manages also pay to use the system. This helped shave Kinsley's cost in building the network, says John Dolmetsch, BIG's president and CIO. The wireless network consists of a high-speed backbone, with secondary spurs fanning out to other offices at speeds ranging from 284K to 24M bit/sec.
Kinsley routes all voice traffic from IP and digital phones over its wireless IP backbone. Digital phone signals are converted to IP at remote switches. All voice traffic terminates in IP trunk cards in a private branch exchange from Nortel Networks Ltd. The switch can handle up to 336 concurrent voice-over-IP sessions, Dolmetsch says.
Kinsley's wireless network uses Tsunami point-to-point and point-to-multipoint wireless networking equipment from Proxim Inc. in Sunnyvale, Calif. Tsunami operates in the 5.8-GHz unlicensed frequency band and interconnects backbone locations at speeds up to 24M bit/sec. The network also uses BreezeAccess II 2.4-GHz wireless equipment from Alvarion Inc. in Carlsbad, Calif., to provide connectivity with smaller locations and remote job sites.
The equipment is installed on five towers within a 30-mile radius around York, each no farther than 10 or 12 miles from an office location, Dolmetsch says. Kinsley completed the fixed wireless backbone in 2001 and has continued to add office locations.
Dolmetsch estimates the system's five-year return on investment at 70 percent when calculated against the cost of the voice and data circuits it replaced. Savings on phone charges alone have been US$3,500 per month, he says. The wireless equipment cost about $200,000.
Todd Carothers, an analyst at The Telnecity Group LLC in San Jose, says the size and scope of the Kinsley wireless WAN is unusual. "I've never heard of [a wireless WAN] by one company as extensive as this," he says.
The Hotel Wireless
Rather than install a private fixed wireless system, Kevin Lanigan, vice president and general manager of the Stanford Park Hotel in Menlo Park, Calif., contracted with a service provider. The service delivers the high data rates Lanigan needs to support guest Internet access and provides variable bandwidth -- something he couldn't easily obtain from his local phone company.
The hotel, located in the heart of Silicon Valley, hosts large meetings for local high-tech companies. Those guests require bandwidth for meetings that it would typically take multiple T1 lines to support. Lanigan initially contacted the local exchange carrier, a unit of SBC Communications Inc. in San Antonio, and was told that it would take 60 to 90 days to install such circuits. In contrast, NextWeb Inc., a wireless ISP in Fremont, Calif., provides a basic 1.44M bit/sec. T1 circuit from a small dish on the hotel's roof, and it can ramp up the bandwidth to the equivalent of multiple T1 lines in one day.
David Williams, vice president of business development at NextWeb, says his 5-GHz service supports speeds from 1M to 10M bit/sec. Lanigan's T1 service supports WLAN access throughout the 163-room hotel -- a service for which it doesn't charge guests extra. Nonetheless, Lanigan says the broadband wireless installation has paid off: The hotel has landed "not fewer than 12 group bookings" in the past year because of its ability to offer such connectivity.
While broadband wireless was once viewed as ideal for rural areas with little telecommunications infrastructure, Trent Anderson, CEO of wireless ISP SkyRiver Communications Inc. in San Diego, says that even in densely populated areas, there are pockets not served by telephone companies' Digital Subscriber Lines or fiber. And if fiber connections are available, they are often prohibitively expensive, he says.
Linda Tucker, co-founder of Aerial Access LLC, a digital aerial photography firm in San Diego, fell on the other side of that digital divide. Aerial Access has a half terabyte of stored aerial photos and often needs to send 10MB or larger image files to prospective customers. SBC could offer only fractional T1, at a cost of $350 per month. SkyRiver charges $149 per month for a 512K bit/sec. connection, which Tucker says is adequate for her requirements. "An average file between 3 and 10MB transmits in between 30 and 60 seconds," she says.
Although vendors such as Proxim and wireless ISPs such as NextWeb and SkyRiver have established a fixed wireless beachhead, the wireless WAN market is still in its infancy, according to Wai Sing Lee, an analyst at Frost & Sullivan Inc. in San Antonio.
Between 1,500 and 1,800 wireless ISPs operate in the unlicensed spectrum band today, according to Daryl Schoolar, an analyst at In-Stat/MDR in Scottsdale, Ariz. He predicts significant growth over the next several years. Free spectrum and low-cost equipment, at about $8,000 for a complete base station, will serve as the drivers for this growth, he says.
But analysts and wireless ISPs alike say growth could be inhibited by interference. The 2.4-GHz band is already crowded, and the same may happen in the 5-GHz band. NextWeb's Williams says interference could be mitigated by using a technique called dual polarization, whereas Carothers at Telnecity envisions the wireless ISP industry developing a self-policing interference body.
Security is also a concern, but not as much with fixed wireless as with broadband, since fixed wireless uses a narrow, hard-to-intercept transmission beam. The Proxim gear used by Kinsley adds a proprietary encryption scheme. Wireless ISPs like SkyRiver build in additional layers of security as well, including a Media Access Control layer. They also offer individual addresses for customer equipment.
But even though the industry is still evolving, the technology is stable. Craig Mathias, an analyst at Farpoint Group in Ashland, Mass., calls fixed wireless relatively easy to install and operate.
And to users, it seems like magic. Jeff Leaf, a project co-coordinator at Kinsley-owned LSC Design Inc., notes that "when you tell people in York that you're doing business over a wireless network, they don't have a clue." When the network was first turned on, Leaf says, he marveled at the speed at which his CAD files were transmitted. Now he doesn't think about the network or its speed at all -- a sure sign that the technology has gained acceptance.-- Computerworld (US)