"We want people to be able to roam among WiMax networks, not just in Taiwan but also foreign visitors and when Taiwanese go overseas," said Charlie C.Y. Wu, Fitel's president.

Client devices aren't the only products where interoperability is critical. Transmission equipment from different vendors must also work together.

"Operators don't want to buy equipment from a single vendor for many reasons," said Mike Ropicky, a senior director of product, operations and marketing at Motorola. One of the most important is to hedge against the possibility that an equipment vendor's technology will fall behind its competitors, leaving the operator without the ability to roll out future upgrades to its service, he said.

To fill this gap in certification and reassure both users and operators, equipment makers like Motorola and LG-Nortel have embarked on their own certification programs, testing the interoperability of their products with those from other vendors, including client devices. This helped clear the way for initial trials and deployments of WiMax, and should help smooth the way forward for the rollout of more WiMax networks.

Besides the promise of broadband Internet access over large areas, WiMax promises to shake up the competitive landscape and could unseat large mobile operators from the commanding positions they now hold.

Most major mobile operators have said they won't deploy WiMax, choosing to wait for LTE to become available before they overhaul their networks and offer faster data speeds. They have little choice due to the high investments they've already made in 3G and related technologies -- investments that in many cases have yet to be fully recovered.

"Operators that have spent a significant amount of money on 3G will have a hard time justifying it to their shareholders now they're going to put more money in a completely new construction," Intel's Viswanathan said.

Designed as an upgrade for 3G and HSPA networks, LTE will offer greater bandwidth than current mobile technologies. For example, NTT DoCoMo, Japan's largest mobile operator, announced last month that its LTE trials had achieved a 250Mbps download speed. The high-speed technology could start appearing in its networks by 2010, the operator said.

Vodafone, one of the world's biggest operators, is also backing LTE. Trevor Gill, head of networks at Vodafone Group R&D, reportedly told attendees at a U.K. conference the technology was likely to be selected as a future upgrade for the operator's HSPA networks, even as it continues to watch WiMax closely.

Not all cellular operators plan to skip WiMax; smaller players see the technology as a way to gain ground on larger rivals. For example, Sprint in the U.S. and KDDI in Japan both have plans to offer WiMax. These companies and others like them, called "attackers" by industry watchers, see the earlier availability of WiMax as an opportunity to gain a competitive advantage by being the first to roll out a wireless broadband service.

"With WiMax, what you're going to see is a lot of attackers go out there and deliver a service," said Peter MacKinnon, chairman of LG-Nortel. "That's what will define the WiMax market."

WiMax will also find a foothold in emerging markets, where broadband Internet penetration remains low. In these markets, the technology will be used as a fixed-wireless service, providing wireless Internet access to a fixed location, such as a home or office, rather than a service designed for mobile users.

However, operators in these markets will likely use the same version of WiMax, called 802.16e, that was developed for mobile users, because economies of scale will mean these products end up being cheaper than the fixed-wireless version of WiMax, known as 802.16d, said Margaret Rice-Jones, CEO of Aircom International, a company that helps operators plan WiMax networks.

"It also gives them the option in the future of moving to a mobile network," Rice-Jones said.

(Dan Nystedt, in Taipei, contributed to this story.)