Initially the IEEE 802.16, ETSI HiperMAN and WiBro/Mobile WiMAX standards collectively defined technologies from 2 GHz to 60 GHz.  That has since been extended to support even lower frequencies.  However, broadband wireless service is not delivered in every single spectrum range in that very wide band of frequencies.  The IEEE 802.16 for example supports multiple PHY layers as well as several different radio polling technologies that vendors could use.  Additionally, the technical rules as defined by the various controlling governmental entities throughout the US and international communities for various spectrum bands do differ, necessitating variations in the PHY layers of radios. 

Ultimately, this means that the Forum chose to define profiles that will support the PHY layers that member radio vendors will need, based on their planned equipment offerings.  Additional profiles will come online as needed.  Initially this means the Forum chose to address the 256 Fast Fourier Transform (FFT) orthogonal frequency division multiplex (OFDM) PHY with a single MAC to create an initial interoperability specification set for Fixed WiMAX.  The Mobile WiMAX standard, as ratified supports the orthogonal frequency division multiple access (OFDMA®) at 2K FFT, 1K FFT, 512 FFT or 128 FFT.  The Korean WiBro/Mobile WiMAX version uses OFDMA 1K FFT.  Frequency ranges that currently have product profiles include the licensed 2.3 GHz, 2.5 GHz, 3.5 GHz, 3.65 GHz bands and the 5.8 GHz unlicensed band.  There are plans afoot to extend WiMAX to support the newer 700 MHz spectrum range and even potentially the UHF.