WiMAX 802.16a Standars Broadband Wireless Access

WiMAX Broadband wireless access provides more capacity at lower cost than DSL or cable for extending the fibre networks and supporting multimedia and fast internet applications in the enterprise or home. But it has been held back by the lack of a standard, so that solutions have been based on proprietary, single-vendor efforts. Standardization through the IEEE 802.16 specification raises the potential to:
• Stall wired broadband and make wireless the key platform of the future
• Extend the range of Wi-Fi so that the myth of ubiquitous wireless can become a reality
• Provide an alternative or complement to 3G
• Provide an economically viable communications infrastructure for developing countries and mobile blackspot regions in developed nations

WiMAX Background and 802.16

Although the 802.16 project started as far back as 1998, the body of work was done in 2000-2003 in an open consensus process. The aim was to make broadband wireless access more widely and cheaply available through a standard for wireless metropolitan area networks. The overall vision for 802.16 is that carriers would set up base stations connected to a public network. Each base station would support hundreds of fixed subscriber stations, probably mounted on rooftops. The base stations would then use the standard's medium access control layer (MAC) - a common interface that makes the networks interoperable - to nearly instantaneously allocate uplink and downlink bandwidth to subscribers according to their needs.

802.16 MANs could also anchor 802.11 hotspots, which serve as wireless local area networks (LANs), as well as servicing end users directly. With the mobile standard, users will be able to use the WMAN base station to communicate via handsets as they move within the 50 mile range. The first version of the standard, 802.16, was published in April 2002 and addressed fixed, line of sight connections for the ‘first mile/last mile’ link. It focused on efficient use of various licensed frequencies in the 10-66GHz bandwidth.

802.16 standards have never taken a lowest common denominator approach. Unlike Wi-Fi, few proprietary vendors of equivalent equipment can outdo the performance of WiMAX. It offers the highest performance broadband , technology except for broadcast and, on the wired side, MMDS, and is on a level with satellite.
Although, even with the upcoming mobile version of standard, WiMAX cannot be as wide area as 2G/3G, it delivers far higher rates and, with sufficiently widespread deployment, could significantly cut into the usage of cellular networks in many areas.

The next version of the standard, 802.16a, published in April 2003, is the one that has really kick-started WiMAX into being adopted as the dominant wireless broadband technology. This is also for fixed wireless but extends the range of WiMAX from 31 to 50 miles and operates in the low frequency 2-11GHz spectrum and so can be adopted by unlicensed operators. It uses point-to-multipoint or (optionally) mesh topologies and does not require line of sight. Specifically, it uses licensed bands at 3.5GHz and 10.5GHz internationally and 2.5-2.7GHz in the US; and unlicensed 2.4GHz and 5.725-5.825GHz.

An important aspect of 802.16x is that it defines a MAC (media access control) layer that supports multiple physical layer (PHY) specifications. This is critical to allow equipment makers to differentiate their offerings – for instance with novel approaches to smart antenna use without becoming non-interoperable; and to customize the equipment for the frequency band in use.
 
Next on the agenda are:
• 802.16c/d, published in Jan 2003, address interoperability by providing detailed system profiles and specifying combinations of options, as the basis for compliance and interoperability tests. The WiMAX Forum presented the first of these tests at the WCA conference in July 2003 and further work will be done by this body and the IEEE throughout this year. The ‘c’ protocol relates to protocols, test suite structures and test purposes while ‘d’ fixes errata and protocols not covered in ‘c’, and creates the system profiles.

• 802.16e, which adds mobility to the standard and really throws down the gauntlet to cellular. This element of the standard has the particular interest of Nokia, which can see a new revenue stream at both base station and handset level. The draft will be ready in August or September 2003.

• Probably, an important new project to enable handoff between Wi-Fi and WiMAX.