Companie in Tempe, Arizona, face a choice that the rest of us will also be facing. Should you spend money on metro-area Wi-Fi services or cellular 3G data services?

As with most things wireless, the answer is not simple. You might pay for both, depending on your end users' requirements and applications.

Yet Wi-Fi providers have been touting lower monthly fees and higher bandwidth compared with cellular providers for services such as Internet access, VPN connections to corporate networks and VOIP calls. Those services are being marketed both to businesses and individual mobile users.

To deliver these services, mesh networks based on the IEEE 802.11 standards are being set up to blanket large areas, such as the Wireless Access Zone Tempe (WAZTempe) network, which was completed just last week by the network operator NeoReach Wireless, a division of MobilePro (read our description of the project) . Like nearly all such networks, WAZTempe operates in the unlicensed 2.4-GHz and 5-GHz radio bands.

Tempe - a mesh with QoS
The network consists of 550 outdoor, multi-radio access points from Strix Systems. Each access point has two 802.11b/g radios to connect to client devices, and two 802.11a radios to route the traffic with neighboring access points. At 12 locations, these devices are wired into a newly built fiber Gigabit Ethernet ring, from Cox Communications.

NeoReach authenticates users via 802.1X over an encrypted connection, assigns them to different virtual LANs (VLAN), and can enforce different QoS levels depending on what plan a customer has chosen, says Ryan McCaigue, director of engineering for NeoReach and the man who designed and deployed the Tempe network.

So far, NeoReach and the retail network providers who offer service over the wireless infrastructure have signed up 1,500 subscribers. A key target is businesses, which are offered higher bandwidth, more stringent QoS guarantees, and specialised equipment like high-gain or directional antennas.

Subscriptions start at US$29 a month, with bandwidth of up to 384 kbit/s upstream and up to 1 Mbit/s downstream. By contrast, McCaigue says his own cell phone package costs about $60 a month for voice only, with the option of spending another $40 a month for data services at about 200 kbit/s to 400 kbit/s.

Sounds like a no-brainer for network executives, right?

No-brainer no how
Well, no, according to critics.

Market research firm The Yankee Group just issued a report called "Myths and Realities of Wi-Fi Mesh Networking. The basic conclusion was summed up by co-author Phil Redman. "There is a limit to how far you can push an unlicensed radio technology," he says. That's true even as the rapid pace of Wi-Fi innovation, including 802.11n which promises bandwidth of 300 Mbit/s to 400 Mbit/s in 2007, enables providers to push that limit.

But providers such as NeoReach and vendors like Strix, Tropos, BelAir and others point to scores of metro-area deployments around the United States as evidence that Wi-Fi mesh networks are viable.

"If we're talking about just the technology, then these types of networks designed to cover what I call 'localised regions,' with the intention of having a modest level of usage, make sense," Redman acknowledges.

But whether Wi-Fi networks can succeed as sustainable businesses is unclear, he says. "It's very difficult for a [Wi-Fi] business model to work in isolation from another service that has a reasonable level of market scale" such as wide-area cellular services, he says.

Mobile worker needs
Bob Egan, director of emergent technologies at consultancy Tower Group, is also skeptical about Wi-Fi mesh being able to deliver for mobile enterprises.

"802.11 was never intended and will never be a metro architecture," says Egan, an author of the original 802.11 standard. "Metro [Wi-Fi] nets are just a venture capitalist wish, and not an architectural reality."

He suggests imagining yourself as a business person worker in a Starbucks coffee shop working on your wireless laptop to finalise a customer deal and at the next table, three teenagers are playing on a bandwidth-hungry wireless gaming console. "You're trying to make money. And they're not," Egan says. "How does this make sense from a business standpoint?"

A sometimes hidden cost of Wi-Fi service is having to pay vendors in separate locations for access during the course of a work day or work week. However, that's less a problem when the enterprise has contracts with Wi-Fi aggregators.

Where 3G is available, speeds can realistically reach 300 kbit/s. Using the same wireless access card, customers can still access the Internet using slower data services such as GPRS on 2G networks.

Uniform, consistent, simple
Those speeds, along with uniform, consistent, simple and secure access no matter where you are in the service area, seem to be driving enterprise adoption of cellular data services.

Sierra Wireless builds cellular cards for several carriers including in the US Sprint and Verizon. For the newest EV-DO and High Speed Downlink Packet Access (HSDPA) wireless cards, "our growth has been dramatic" says Greg Speakman, director of marketing for mobile products for Sierra. The company, which doesn't release unit shipments, has its EV-DO modems built in to laptops from Lenovo and HP (and Fujitsu-Siemens offerings are in the way in Europe).

For his part, NeoReach's McCaigue isn't anticipating network problems in Tempe. Interference issues can be sidestepped and two client radios in each access point provide more than enough connections and capacity for the expected density of simultaneous users, he says.

Senior Editor Denise Pappalardo contributed to this story.