Users had a clear focus at last month's WiMax World conference: They wanted to know more about cost-effective, reliable, licensed wireless broadband for applications such as backhaul, access to wireline network services and data backup/recovery.

The conference is one of the main events for the WiMax community, a constellation of chip vendors, radio and equipment builders, billing and management software vendors, systems integrators, carriers and service providers all trying to exploit the IEEE 802.16 standards for wireless broadband. This year's show signed up about 3,000 attendees, compared with just 750 last year, and 150 sponsors and exhibitors.

Fixed comes before mobile
There was a clear divide between corporate users focused on practical concerns and some vendors, such as Motorola, which sketched visionary scenarios of mobile, "personal broadband" services and devices. Those vendors are focusing on one branch of WiMAX - 802.16e, the developing IEEE standard for mobile wireless broadband, some of it delivered over unlicensed frequencies.

But the most likely corporate services to exploit WiMax first will be based on licensed spectrum and the fixed WiMax standard: 802.16-2004, formerly known as 16d. Each base station can deliver up to 75 Mbit/s, over a typical range of up to 5 miles.

"The two standards are not the same, and they address very different markets," says Craig Mathias, principal at Farpoint Group, a consultancy specialising in wireless networking. "We see WiMax dominating for residential and business [wireless] access to the Internet, in fixed, metroscale nets."

It's precisely that scenario of fixed, metro-area access that is drawing the serious attention of users and service providers.

Minneapolis goes for public safety
The city of Minneapolis is working toward creating a pervasive wireless mesh network for public safety workers and city employees, and for providing a low-cost, broadband wireless Internet access for residents and businesses.

The all-IP network will likely combine an 802.11-based mesh for client access, with WiMax providing backhaul, in addition to fibre, says William Beck, the city's deputy CIO.

"Direct connect and backhaul are the plays for WiMax," Beck says. "We have 350 facilities around the city that we want to connect. We can use WiMax for that." Such a network would let the city shift mobile computing from expensive Sprint cellular data services and support such bandwidth-hungry applications as its growing web of wireless surveillance cameras.

Ninety-seven vendors responded to the city's request for proposals. Officials last week narrowed the field to two from nine comprehensive proposals, EarthLink and US Wireless.

Shifting big files on the farm
WiMax also is being considered by the US Department of Agriculture as a way to move big data files from image processing computers to farm equipment, says James McKinion, research electronics engineer with the department's Genetics and Precision Agriculture Research Unit.

One such application works like this: Aircraft fly over farm crops and take multispectral images (in effect, photos taken in several kinds of electromagnetic "lights") early in the growing cycle.

The images are processed, coordinated with on-site data via handhelds used by field consultants, and then further processed to give time and location data to controllers and GPS monitors mounted in sprayers and tractors.

Using this data, farmers can target and limit insecticide spraying. That would cut costs, improve efficacy of spraying and use fewer chemicals.

Speed is vital, McKinion says as the farms have a little more than 24 hours to translate the imaging data into a spraying pattern to be most effective.

Today, two plantation pilot systems in Mississippi rely on proprietary fixed wireless broadband gear in the 900MHz and 2.4GHz bands to transport the data files from the processing centre to what is in effect the farm's data centre, and to the equipment in the fields.

"Instead of manually plugging PC cards into the controllers, we can use wireless to deliver megabytes of data in a few seconds, and to make sure we get the right data to the right equipment," he says. "WiMax will make this data more available to farmers in rural areas."

"We could use a few WiMax base stations to cover an entire county. And pricing for WiMax equipment promises to greatly lower the costs" compared to proprietary radios, he says.

Carriers go for backhaul
Meanwhile, backhaul is drawing the attention of companies such as AT&T.

"Our focus is on fixed WiMax services," says Behzad Nadji, AT&T chief architect. One reason is that AT&T pays local incumbent local exchange carriers about US$8.5 billion every year to provide last-mile access between AT&T's network core and AT&T customers' networks.

"We're paying high-octane profits to those guys," Nadji says. AT&T is weighing the technical and business feasibility of creating a WiMax service that would eliminate those middlemen.

AT&T enterprise users in a recent survey said they want services that provide data backup, primary network access and load-sharing, in that order, according to Nadji. Users see the main benefits of WiMax as improved reach - being able to get network access where they need it, lower access costs, alternative network access and disaster-recovery options.

As part of its WiMax evaluation, AT&T is preparing to launch its third and most ambitious WiMax trial later this year, building a wireless broadband network in part of Atlanta to link business customers with AT&T's core network. The company already has pilot networks with a trio of businesses in suburban Middletown, New Jersey, and a handful of tiny villages in rural Alaska.