The International Telecommunication Union, Radiocommunication Sector (ITU-R) has re-ignited the technology tussle between so-called 4G technologies Long-Term Evolution (LTE) and WiMax by approving the technical requirements for next-generation mobile broadband technology, IMT-Advanced.

With the general specifications now set for IMT-Advanced -– which is ITU-speak for 4G -– candidate technologies can, from October, be submitted to the ITU.

And, as Unstrung has reported, the WiMax camp at the Institute of Electrical and Electronics Engineers Inc. (IEEE) and the LTE camp at the 3rd Generation Partnership Project (3GPP) are already prepping their candidates -- 802.16m and LTE-Advanced, respectively -- for the next mobile broadband showdown. (See Wireless Camps Prep Fresh 4G Battle, 3GPP Studies LTE Are Advanced, and Faster WiMax on the Way.)

The technical criteria were approved at a meeting held in Dubai at the end of June. While the ITU-R declined to provide any details of the agreed technical requirements to Unstrung, those details are expected to be published on the IMT-Advanced Website at the end of this week.

Some guidelines are available from industry sources, though. According to Erik Ekudden, vice president and head of standardization and industry initiatives at Ericsson AB, who has been involved in setting the criteria, the requirements include average downlink speeds of 100 Mbit/s in the wide area network, and up to 1 Gbit/s for local access or low mobility scenarios.

Another key criterion for IMT-Advanced is low latency. Specifically, the parameters include less than 10 millisecond roundtrip delay and less than 100 milliseconds to set up a new session.

And IMT-Advanced calls for very wide channel widths. The technology needs 40MHz and preferably up to 100MHz channel allocations, according to Ekudden.

Requirements of that kind are completely new territory for the cellular industry. Never before have such large spectrum allocations been needed. And that means spectrum availability will be a big challenge for IMT-Advanced technologies.

"Regulators have to set aside more continuous spectrum to launch these systems," says Ekudden. "It's up to governments and regulators around the world to allocate this spectrum. The industry challenge is to ensure the new spectrum is made available for IMT-Advanced."

Will WiMax and LTE get together in IMT-Advanced?
IMT-Advanced poses an opportunity for WiMax and LTE to get together. But opinions seem to vary about the likelihood of the two camps burying the hatchet and blending their rival technologies, which actually have much in common. (See WiMax's Long-Term Evolution.)

While Unstrung has reported that the IEEE and 3GPP have considered the prospect of working more closely on IMT-Advanced, others believe the two technologies are set on their own next-generation paths and cannot be combined simply.

"We don't see any trend for putting everything into one bucket, stirring it around and seeing what comes out," says Ekudden. "It's not so easy to technically harmonize. There is strong support for [each] technology as such."

"A lot of good will come out of this big process [for IMT-Advanced]," he adds. "The technical basis for different technology tracks is already established and they are not going to change."

The ITU-R will start accepting proposals for candidate technologies at the next IMT-Advanced meeting in October. At that time, it's understood the ITU-R will also agree on the evaluation criteria for the technologies.

IMT-Advanced technologies will take the cellular systems through the next 10 to 15 years. The ITU-R is expected to complete its recommendation for the IMT-Advanced radio interface technology in early 2011.

— Michelle Donegan, European Editor, Unstrung