The current version of 802.16 Fixed WiMAX, which supersedes previous standards is the 802.16d or as it is sometimes called 802.16-2004.  Its product profile utilizes the OFDM 256-FFT (Fast Fourier Transform) system profile, which is just different enough from its sister standard of Mobile WiMAX (802.16e) that the two are incompatible.  Interestingly, both standards support both protocols within the technology protocol as well as the one chosen for Mobile WiMAX and the Korean WiBro/Mobile WiMAX standard.  If the Forum had elected to use an OFDMA version in Fixed WiMAX, it would have been far easier to provide an upgrade path. 

This particular disconnect likely points to the emerging understanding of the marketplace power of WiMAX.  More importantly, it indicates the power of the Korean WiBro/Mobile WiMAX persuasion, which heavily influenced the use of OFDMA® in the Mobile Standard. 

The Fixed WiMAX 802.16-2004 standard supports both time division duplex (TDD) and frequency division duplex (FDD) services---the latter of which is far more popular with mobile wireless providers than the newer TDD approach. 

At this point, Fixed WiMAX 802.16d systems are widely deployed in both Europe and Asia, but it is clear that for many vendors the adoption of the Mobile WiMAX 802.16e is the option of choice. 

Having said this, the opening of the US 3.65 GHz spectrum range has opened up a 802.16d opportunity in the US as vendors adapt existing 3.5 GHz systems (and mostly Fixed WiMAX based built for International use) radio systems to use in this band.