WiMAX, which stands for "Worldwide Interoperability for Microwave Access," is a subset of standard, interoperable implementations within the IEEE 802.16 family of standards developed by the Institute of Electrical and Electronics Engineers (IEEE) 802.16 Working Group on Broadband Wireless Access Standards.
The workgroup, a unit of the IEEE 802 LAN/MAN Standards Committee, was established by the IEEE Standards Board in 1999. In keeping with its objective of preparing formal specifications for the global deployment of broadband Wireless Metropolitan Area Networks (WirelessMAN), the workgroup created the IEEE 802.16, family of standards.
The term "WiMAX" encompasses the following: 802.16d, also known as Fixed WiMAX; and 802.16e, also known as Mobile WiMAX.
802.16d or Fixed WiMAX was an amendment created with the objective of being aligned with the European Telecommunications Standards Institute (ETSI) HIPERMAN standard, and laying down conformance and test specifications. Development began in September 2003 and concluded in 2004. With its release, the earlier documents, 802.11a-c, were withdrawn. It uses orthogonal frequency-division multiplexing (OFDM) as its air interface technology.
802.16e or Mobile WiMAX comes with a number of enhancements, including better support for Quality of Service (QoS) and the use of Scalable OFDMA. Concluded in 2005, 802.16e is the latest amendment of the 802.16 family to have been released so far. It uses Scalable OFDMA for data transmission, supporting channel bandwidths from 1.25 MHz up to 20 MHz, with up to 2048 sub-carriers.
Under good conditions, a highly efficient 64 quadrature amplitude modulation (64 QAM) coding scheme is used; in intermediate conditions, 16 QAM and quadrature phase-shift keying (QPSK) is used; while under less favorable conditions, binary phase-shift keying (BPSK) is used. This is because the physical layer (PHY) of an 802.16 system supports adaptive modulation and coding. It also supports Multiple-in Multiple-out (MIMO) antennas for good NLOS characteristics (or higher bandwidth) and hybrid automatic repeat request (HARQ) for ample performance in error-correction.
Features in the media access control (MAC) layer include Convergence Sub-layers, power-saving mechanisms such as "idle" and "sleep mode," and handover mechanisms. 802.16e provides strong support for QoS because it is a connection-oriented technology, and the subscriber station (SS) needs to be allocated a channel by the base station (BS) before it can begin to transmit data.
Due to its bandwidth and reach, WiMAX is suitable for the following uses: creating a network among Wi-Fi hotspots; allowing high-speed data and telecommunications services; enabling nomadic connectivity; and serving as a wireless alternative for last mile broadband access in place of cable or DSL.