Sprint Nextel Corp.'s decision to spend $2 billion to $4 billion on a national WiMax network, announced last week, is a shot in the arm for 802.16e, positioning the mobile version of WiMax against 3.5G and 4G standards.

It also hints at a coming carrier battle for a national footprint between Sprint and startup Clearwire Inc., an operator founded by Craig McCaw that received $600 million in financing from Intel Corp. last month. In mid-July, Sprint filed suit against Clearwire in Johnson County District Court, near Clearwire's Kirkland, Wash., headquarters, claiming "conspiracy and tortuous influence" in Clearwire's attempt to acquire spectrum in the Seattle area.

Sprint's plan is to migrate its 2.5-GHz broadband access technology, which evolved from multichannel, multipoint distribution system (MMDS) networks acquired from American Telecasting Inc., to a mobile WiMax network that will cover 90 percent of its U.S. market.

Sprint Nextel's vote for mobile WiMax won praise last week from supporters of Internet Protocol-based broadband services, as well as from industry groups like the

WiMax Forum. Not surprisingly, industry groups closer to traditional cellular models questioned the wisdom of the move. And Qualcomm Inc., which earlier failed to convince Sprint to move from EVDO (evolution data optimized) networks to the flash orthogonal frequency-division multiplexing broadband networks developed by Flarion Inc. (now a Qualcomm subsidiary), walked a fine line, avoiding direct attacks on WiMax and touting its continuing relationship with Sprint.

Intel Corp.'s influence peddling on behalf of WiMax is pressuring carriers into making premature decisions on mobile broadband platforms, said Joe Hudson, managing director of the UMTS TDD (Universal Mobile Telecommunications System Time-Division Duplexing) Alliance, which advocates building mobile broadband networks on the established cellular foundation. In Hudson's view, Intel, having failed to crack the cellular market, was forced to take a technology developed for point-to-point communications (802.16) and "morph it into a mobile broadband play."

"We believe it is a monumental challenge to take a P2P technology and have it compete with the mature mobile solutions of vendors and standards bodies which have years of experience in mobile networks, signal propagation, building penetration, cellular topology, interference mitigation, multipath correction, handoff and high-speed terminal connections," Hudson wrote in a public response to the Sprint announcement. "By destroying the public availability of realistic information and influencing customers with short-term financial incentives, Intel may get its long-term payoff. But will Sprint?"

For its part, Sprint Nextel made no apologies for eschewing circuit-switched telephony models in favor of an emerging technology based on TCP/IP protocols and connectionless datagram models.

Barry West, chief technology officer for Sprint Nextel and president of the 4G Mobile Broadband group at Sprint, said the critical criterion for next-generation broadband was that the approach "had to be all-IP. Adopting Internet Protocol universally is really going to set us apart."

Sprint developers assumed that the future would belong to OFDM, which WiMax networks would use, West said. Initially, Sprint Nextel tested a flash OFDM network developed by Flarion (now part of Qualcomm) in the Raleigh-Durham, N.C., area. The technology worked well in the tests, West said, but it is only offered in 1.25-MHz channels, and Sprint wanted to see wider channels in the frequency band.

Ronny Haraldsvik, vice president of broadband marketing at Qualcomm, said the company privately keeps carriers apprised of its timetable for 5- and 10-MHz flash OFDM channels. He said the Raleigh-Durham trials had performed ideally.

"Decisions are often made on the basis of many business issues," Haraldsvik said. "We accept that, and we are continuing to work with Sprint Nextel on existing dual-band programs."