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 appear to be 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 delivers full duplex transmission on the same signal if desired. Mobile WiMAX will do the same.