The true Mobile WiMAX standard of 802.16e is divergent from Fixed WiMAX. It attracted a significant number of Forum members towards an opportunity to substantively challenge existing 3G technology purveyors. While clearly based on the same OFDM base technology adopted in 802.16-2004, the 802.16e version is designed to deliver service across many more sub-channels than the OFDM 256-FFT. It is important to note that both standards support single carrier, OFDM 256-FFT and at least OFDMA 1K-FFT.
The 802.16e standard adds OFDMA 2K-FFT, 512-FFT and 128-FFT capability. Sub-channelization facilitates access at varying distance by providing operators the capability to dynamically reduce the number of channels while increasing the gain of signal to each channel in order to reach customers farther away. The reverse is also possible. For example, when a user gets closer to a cell site, the number of channels will increase and the modulation can also change to increase bandwidth. At longer ranges, modulations like QPSK (which offer robust links but lower bandwidth) can give way at shorter ranges to 64 QAM (which are more sensitive links, but offer much higher bandwidth) for example. Each subscriber is linked to a number of subchannels that obviate multi-path interference. The upshot is that cells should be much less sensitive to overload and cell size shrinkage during the load than before. Ideally, customers at any range should receive solid QOS without drops that 3G technology may experience. Here is an in-depth Q&A on OFDMA®.
The 802.16e version of WiMAX also incorporates support for multiple-input-multiple-output (MIMO) antenna technology as well as Beamforming and Advanced Antenna Systems (AAS), which are all "smart" antenna technologies that significantly improve gain of WiMAX systems as well as throughput.
The 802.16e standard is being utilized primarily in licensed spectrum for pure mobile applications. Many firms have elected to develop the 802.16e standard exclusively for both fixed and mobile versions. The 802.16e version of WiMAX is the closest comparable technology to the emerging LTE mobile wireless standard. Or rather, it is more proper to say that LTE is the most comparable to Mobile WiMAX in terms of capabilities as well as technology. The two competing technologies are really very much alike technically.