WiMAX Forum denies FDD profile is imminent

The WiMAX Forum was swift to debunk the notion that it is set to reveal an FDD profile for mobile WiMAX within six months. We reported [1]on a recent article in telecoms.com [2], in which Paul Senior, chief technology officer of WiMAX vendor Airspan, said the WiMAX Forum was set to introduce an FDD profile and has been hush-hush about the move because it wanted to get IMT-2000 approval first and avoid the firestorm that an FDD profile would have created.

The WiMAX Forum is adamant no decisions have been made on an FDD profile, and therefore it has no official timeline pertaining to releasing one.

"There is discussion but it hasn't gotten to the point where we would be able to create a timeline," Tim Hewitt, regulatory working group chair with the WiMAX Forum, told FierceBroadbandWireless. "It all comes down to what our members want to do."

Why is this discussion significant? FDD mode, or frequency division duplex, sends and receives information using separate channels for the uplink and downlink. Today, mobile WiMAX uses TDD, or time division duplex, signaling, which assigns time slots for both the uplink and downlink signals. The IMT-2000 Extension Band is harmonizing 2 x 70 MHz for FDD spectrum internationally, leaving 50 MHz for TDD technologies like WiMAX. Moreover, much of the 700 MHz band's spectrum, including the coveted C-block, is configured for FDD signaling.

In light of this, I'd argue that the WiMAX community needs a solid story when it comes FDD, especially since the technology's backers have high hopes for mobile WiMAX in the 700 MHz band.

The WiMAX world was smart to focus on TDD for mobility to make use of that under-utilized spectrum around the world. As Hewitt says, TDD spectrum is easier to find than FDD spectrum, which requires paired spectrum. Now, with the blessing of the International Telecommunication Union, the WiMAX community is creating an ecosystem in the TDD band that will enable it to more effectively compete with technologies such as HSDPA and LTE in FDD bands.

Of course, there are some political issues I can dream up as to why the WiMAX Forum needs to be careful about pitting itself aggressively against HSDPA, EV-DO and LTE in the paired bands. One is that the forum's major members are vendors and operators that also have established revenue-generating businesses in these paired-band technologies. Moreover, continuing to emphasize the TDD band creates an opportunity for WiMAX to be the most viable option for unpaired spectrum with little competition.

Read more about the WiMAX Forum's views on this issue here [3].--Lynnette [4]