Bad news for 4G: New Wimax variant works on 3G towers

One very big reason that Wimax has not gained any fans with the wireless cartel is that it does not coexist well with current 3G infrastructure. A new variation in the Mobile Wimax spec will change that, and will likely be ready for prime time before 4G gets off the ground.

Unlike 3G and upcoming 4G technologies (like LTE), WiMAX uses Time Division Duplexing (TDD) for two-way communications. TDD allows both upstream and downstream data use the same frequency, but the data is sent and received during different time slices. It’s useful for applications that are confined to narrow bits of spectrum, but current 3G and upcoming 4G technologies use Frequency Division Duplexing (FDD). FDD uses separate frequencies for sending and receiving data simultaneously, which has the advantage of reducing interference between towers.

Cellular carriers that are more comfortable with FDD are leery of TDD technologies like WiMAX, or so it’s believed by some of WiMAX’s backers. Paul Senior, a founding member of the WiMAX Forum and CTO of Airspan, told the Telecoms Blog Informer earlier this month that the Forum has been working on FDD-flavored Mobile WiMAX for the last year on the hush-hush. “The WiMAX forum will have an FDD profile for Mobile WiMAX inside six months,” Senior said. “We’ve been a bit quiet about it because we wanted to get [WiMAX approved for use in the 2.6GHz spectrum]. And if we had gone to [International Mobile Telecommunications] with an FDD profile, we probably couldn’’t have got it through.” (from ARS Technica)