WiMax vendors fear that traditional 3G standards will get all the best spectrum - despite an endorsement for WiMax from the telecoms operators' standard body, the International Communications Union (ITU).

Approval by the ITU, granted at a meeting in Kyoto last month, should represent a breakthrough for WiMax, which emerged from the data-networking standards group, the IEEE, and has faced hostility from many telcos that see it as a competitor to their own mobile broadband services. Within the ITU's IMT-2000 family of 3G standards, WiMax would have a better chance of getting international spectrum when frequency bands are allocated.

However, opposition to WiMax is expected to continue, and the terms of ITU's approval may leave it squeezed into a smaller band of spectrum than its rivals, according to reports.

The ITU's radio-communications standard working party 8F, (ITU-R WP 8F) has recommended a subset of the IEEE's WiMax standard to be approved as a new option in the umbrella of 3G standards known as IMT-2000. The WiMax standard, "OFDMA TDD WMAN" was endorsed by ITU-R at its meeting in Kyoto.

"This new terrestrial radio interface complements the existing family of IMT-2000 radio interfaces and is in direct response to the demands of ITU Members to address the continuously growing wireless marketplace," said an ITU-R statement.

If the proposal is accepted by ITU Study Group 8 (SG8) later this month in Geneva, and then WiMax would be in the running at ITU's spectrum conference, the World Radio Communications Conference (WRC-07) in October.

The WP 8F meeting set out a roadmap, which calls for other extensions to IMT-2000, and additional spectrum. Beyond 3G, the group has set out principles for what it calls "IMT-Advanced," due to be delivered as early as 2011- for which WiMax is now a candidate.

"Spectrum allocation is crucial for WiMax around the world," said WiMax Day, the news site of the WiMax Spectrum Owners' Alliance. "Inclusion in the IMT-2000 interface will enable WiMax technologies to be eligible for radio spectrum otherwise reserved for IMT-2000 under previous classifications. In particular, the spectrum 2.5 to 2.69 GHz is reserved for use with IMT-2000 in many countries around the world, and is also a primary spectrum band for mobile WiMax."

This so-called "3G expansion band" is the best hope for a global band of good quality spectrum and has proved controversial. ITU backing will help prevent hostile operators squeezing WiMax out of it.

With ITU backing, WiMax will be a much stronger contender against other technologies such as Qualcomm's Flash-OFDM, which has backing from the 3G Partnership Project (3GPP).

However, the ITU is expected to eventually carve up the expansion band in a way which would hamper WiMax, giving two full international 70MHz bands for Frequency Division Duplex (FDD) technologies, which use two separate frequencies to send and receive, leaving only 50MHz, for Time Division Duplex (TDD) technology which sends and receives alternately in the same band, according to Gabriel Brown of Unstrung.

"Such an outcome would still heavily favor the 3G roadmap, which is focused on FDD systems," said Brown. "WiMax companies have the option of developing FDD systems, but at this point it's not clear many would want to go down that route." WiMax systems, such as Sprint Nextel's mobile WiMax network, are based on TDD.