The IEEE developed the 802.16 in its first version to address line of sight (LOS) access at spectrum ranges from 10 GHz to 66 GHz.  The technology has evolved through several updates to the standard such as 802.16a, 802.16c, the Fixed WiMAX 802.16d (802.16-2004) specification and lastly the mobile 802.16e set that are currently commercially available.  The upcoming 802.16m is still a ways away from ratification.  The first update added support for 2 GHz through 11 GHz spectrum with NLOS capability.  Each update added additional functionality or expanded the reach of the standard.
 
For example, the 802.16c revision added support for spectrum ranges both licensed and unlicensed from 2 GHz to 10 GHz.  It also improved quality of service (QOS) and certain improvements in the media access control (MAC) layer along with adding support for the HiperMAN European standard.  The number of supported physical (PHY) layers was increased.  Transport mediums such as IP, Ethernet and asynchronous transfer mode (ATM) were added.

At its core, the technology is intended to take a number of best of breed proprietary enhancements that had been made by vendors using the 802.11 standard and combine them together in a very marketable and standardized WiMAX product. 

For example, older broadband wireless technology such as the Wi-Fi or 802.11b system utilized carrier sense multiple access with collision detection (CSMA/CD) crosstalk methods for base stations and customer premise equipment (CPE) to talk to one another.  Basically, this meant that each radio was constantly talking and creating inefficient overhead.  It also resulted, especially at times of high traffic, in increased packet collisions and retransmissions, further exacerbating the problem.  Some of the proprietary MAC systems built later utilized the base station to define when the CPE would be polled in order to eliminate this problem.  In the way of a permanent cure the 802.16 protocol supports multiple methods of polling that a vendor can choose to use.  Some of these include piggybacking polling requests within overhead traffic, group polling or dynamic co-opting of bandwidth from another unit by the CPE.  The key is that the radios will be interchangeable based on the Forum's initial product profile as well as more efficient.