Basic data on IEEE 802.16 Standards

Attributes	802.16	802.16d-2004	802.16e-2005
Status	Completed December 2001	Completed June 2004	Completed December 2005
Frequency band	10GHz–66GHz	2GHz–11GHz	2GHz–11GHz for fixed; 2GHz–6GHz for mobile applications
Application	Fixed LOS	Fixed NLOS	Fixed and mobile NLOS
MAC architecture	Point-to-multipoint, mesh	Point-to-multipoint, mesh	Point-to-multipoint, mesh
Transmission scheme	Single carrier only	Single carrier, 256 OFDM or 2048 OFDM	Single carrier, 256 OFDM or scalable OFDM with 128, 512, 1024, or 2048 subcarriers
Modulation	QPSK, 16 QAM, 64 QAM	QPSK, 16 QAM, 64 QAM	QPSK, 16 QAM, 64 QAM
Gross data rate	32 Mbps – 134.4 Mbps	1 Mbps–75 Mbps	1 Mbps–75 Mbps
Multiplexing	Burst TDM/TDMA	Burst TDM/TDMA/ OFDMA	Burst TDM/TDMA/ OFDMA
Duplexing	TDD and FDD	TDD and FDD	TDD and FDD
Channel bandwidth	20MHz, 25MHz, 28MHz	1.75MHz, 3.5MHz, 7MHz, 14MHz, 1.25MHz, 5MHz, 10MHz, 15MHz, 8.75MHz	1.75MHz, 3.5MHz, 7MHz,14MHz, 1.25MHz, 5MHz, 10MHz,15MHz, 8.75MHz
WiMAX implementation	None	256 - OFDM as Fixed WiMAX	Scalable OFDMA as Mobile WiMAX

SALIENT FEATURES OF WiMAX

WiMAX is a wireless broadband solution that offers a rich set of features with a lot of flexibility in terms of deployment options and potential service offerings. Some of the salient features that deserve highlighting are:

1. OFDM-based physical layer
2. Very high peak data rates
3. Scalable bandwidth and data rate support
4. Adaptive Modulation and Coding (AMC)
5. Link-layer retransmissions
6. Support for Time Division Duplex (TDD) and Frequency Division Duplex (FDD)
7. Orthogonal Frequency Division Multiple Access (OFDMA)
8. Flexible and dynamic per user resource allocation
9. Support for advanced antenna techniques
10. Quality of Service (QoS) support
11. Robust security
12. Support for mobility
13. IP-based architecture

IEEE 802.16 and WiMAX

The IEEE 802.16 group was formed in 1998 to develop an air-interface standard for wireless broadband. The group’s initial focus was the development of a Line-Of-Sight (LOS)-based point-to-multipoint wireless broadband system for operation in the 10GHz–66GHz millimeter wave band. The resulting standard—the original 802.16 standard, completed in December 2001—was based on a single-carrier PHY layer with a burst Time Division Multiplexed (TDM) Media Access Control (MAC) layer. The IEEE 802.16 group subsequently produced 802.16a, an amendment to the standard, to include NLOS applications in the 2GHz–11GHz band, using an Orthogonal Frequency Division Multiplexing (OFDM)-based PHY layer. Further revisions resulted in a new standard in 2004, called IEEE 802.16d-2004, which replaced all prior versions and formed the basis for the first WiMAX solution. In December 2005, the IEEE group completed and approved IEEE 802.16e-2005, an amendment to the IEEE 802.16d-2004 standard that added mobility support. Currently, the WiMAX Forum has two different system profiles:

one based on IEEE 802.16d-2004, OFDM PHY, called the fixed system profile; the other one based on IEEE 802.16e-2005 scalable OFDMA PHY, called the mobility system profile