WiMAX Standards

During this section a detailed explanation about the WiMAX technology standards will be presented.

The IEEE 802.16 defines the wireless metropolitan area network (MAN) technology which is branded as WiMAX. The 802.16 includes two sets of standards, 802.16-2004 (802.16d) for fixed WiMAX and 802.16-2005(802.16e) for mobile WiMAX. The WiMAX wireless broadband access standard provides the missing link for the "last mile" connection in metropolitan area networks where DSL, Cable and other broadband access methods are not available or too expensive. WiMAX also offers an alternative to satellite Internet services for rural areas and allows mobility of the customer equipment.
IEEE 802.16 standards are concerned with the air interface between a subscriber's transceiver station and a base transceiver station. The fixed WiMax standard IEEE 802.16-2004 (also known as 802.16d) is approved by the IEEE in June 2004, which provides fixed, point-to-multi point broadband wireless access service and its product profile utilizes the OFDM 256-FFT (Fast Fourier Transform) system profile. 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. In Dec. 2005, IEEE approved the mobile WiMax standard, the 802.16-2005 (also known as 802.16e). IEEE 802.16e, based on the early WiMax standard 802.16a, adds mobility features to WiMAX in the 2 to 11 GHz licensed bands. 802.16e allows for fixed wireless and mobile Non Line of Sight (NLOS) applications primarily by enhancing the OFDMA (Orthogonal Frequency Division Multiple Access).
IEEE 802.16 and WiMAX are designed as a complimentary technology to Wi-Fi and Bluetooth. The following table provides a quick comparison of 802.16 with to 802.11(WLAN) and 802.15.1 (Bluetooth):

IEEE 802.16 Protocol Architecture has 4 layers: Convergence, MAC, Transmission and physical, which can be map to two OSI lowest layers: phusical and data link.

The WiMAX umbrella currently includes 802.16-2004 and 802.16e. 802.16-2004 utilizes OFDM to serve multiple users in a time division fashion in a sort of a round-robin technique, but done extremely quickly so that users have the perception that they are always transmitting/receiving. 802.16e utilizes OFDMA and can serve multiple users simultaneously by allocating sets of tones to each user.
Following is the chart of various IEEE 802.16 Standards related to WiMAX.

WiMAX OFDM basics

OFDM belongs to a family of transmission schemes called multicarrier modulation, which is based on the idea of dividing a given high-bit-rate data stream into several parallel lower bit-rate streams and modulating each stream on separate carriers.often called subcarriers, or tones.
Multicarrier modulation schemes eliminate or minimize intersymbol interference (ISI) by making the symbol time large enough so that the channel-induced delays.delay spread being a good measure of this in wireless channels . are an insignificant (typically, <>