| Ieee 802.16 |
Article Index for Ieee |
Website Links For Ieee |
Information AboutIeee 802.16 |
| CATEGORIES ABOUT IEEE 802.16 | |
| ieee 802 | |
| wireless networking | |
| metropolitan area networks | |
|
Although the 802.16 family of standards is officially called WirelessMAN , it has been dubbed “ WiMAX ” (from "Worldwide Interoperability for Microwave Access") by an industry group called the WiMAX Forum . The mission of the Forum is to promote and certify compatibility and interoperability of broadband wireless products. 802.16 STANDARDS The first 802.16 standard was approved in December 2001. It delivered a standard for point to multipoint Broadband Wireless transmission in the 10-66 GHz band, with only a Line-of-sight (LOS) capability. It uses a single carrier (SC) physical (PHY) standard. 802.16a was an amendment to 802.16 and delivered a point to multipoint capability in the 2-11 GHz band. For this to be of use, it also required a non line of sight (NLOS) capability, and the PHY standard was therefore extended to include Orthogonal Frequency Division Multiplex ( OFDM ) and Orthogonal Frequency Division Multiple Access ( OFDMA ). 802.16a was ratified in January 2003 and was intended to provide "last mile" fixed broadband access. 802.16c, a further amendment to 802.16, delivered a system profile for the 10-66 GHz 802.16 standard. In September 2003, a revision project called 802.16d commenced aiming to align the standard with aspects of the European Telecommunications Standards Institute (ETSI) HIPERMAN standard as well as lay down conformance and test specifications. This project concluded in 2004 with the release of 802.16-2004 and the withdrawal of the earlier 802.16 documents, including the a/b/c amendments. An amendment to 802.16-2004, IEEE 802.16e-2005 (formerly known as IEEE 802.16e), addressing mobility, was concluded in 2005. This implemented a number of enhancements to 802.16-2004, including better support for Quality Of Service and the use of Scalable OFDMA, and is sometimes called “Mobile WiMAX”, after the WiMAX Forum for interoperability. Amendments in progress Active amendments:
Amendments under development:
Amendments at pre-draft stage:
802.16E-2005 TECHNOLOGY The 802.16 standard essentially standardizes 2 aspects of the air interface - the Physical Layer (PHY) and the Media Access Control layer (MAC). This section provides an overview of the technology employed in these 2 layers in the current version of the 802.16 specification (which is strictly 802.16-2004 as amended by 802.16e-2005, but which will be referred to as 802.16e for brevity). PHY 802.16e uses Scalable OFDMA to carry data, supporting channel bandwidths of between 1.25 MHz and 20 MHz, with up to 2048 sub-carriers. It supports adaptive modulation and coding, so that in conditions of good signal, a highly efficient 64 QAM coding scheme is used, whereas where the signal is poorer, a more robust BPSK coding mechanism is used. In intermediate conditions, 16 QAM and QPSK can also be employed. Other PHY features include support for Multiple-in Multiple-out (MIMO) antennas in order to provide good NLOS characteristics (or higher bandwidth) and Hybrid Automatic Repeat Request (HARQ) for good error correction performance. MAC The 802.16 MAC describes a number of ''Convergence Sublayers'' which describe how wireline technologies such as Ethernet , ATM and IP are encapsulated on the air interface, and how data is classified, etc. It also describes how secure communications are delivered, by using secure key exchange during authentication, and encryption using AES or DES as the encryption mechanism) during data transfer. Further features of the MAC layer include power saving mechanisms (using ''Sleep Mode'' and ''Idle Mode'') and handover mechanisms. A key feature of 802.16 is that it is a Connection Oriented technology. The subscriber station (SS) cannot transmit data until it has been allocated a channel by the Base Station (BS). This allows 802.16e to provide strong support for Quality of Service (QoS). QoS QoS in 802.16e is supported by allocating each connection between the SS and the BS (called a ''service flow'' in 802.16 terminology) to a specific ''QoS class''. In 802.16e, there are 5 QoS classes: The BS and the SS use a service flow with an appropriate QoS class (plus other parameters, such as bandwidth and delay) to ensure that application data receives QoS treatment appropriate to the application. CERTIFICATION Because the IEEE only sets specifications but does not test equipment for compliance with them, the WiMAX Forum runs a certification program wherein members pay for certification. WiMAX certification by this group is intended to guarantee compliance with the standard and interoperability with equipment from other manufacturers. The mission of the Forum is to promote and certify compatibility and interoperability of broadband wireless products. SEE ALSO EXTERNAL LINKS
Standards documents |
|
|