WiMAX, an acronym that stands for
Worldwide Interoperability for Microwave Access, is a certification
mark for products that pass conformity and interoperability tests
for the IEEE 802.16 standards. IEEE 802.16 is working group number
16 of IEEE 802, specialising in point-to- multipoint broadband
wireless access.
Early products are likely to be aimed at network service providers
and businesses, not consumers. It has the potential to enable
millions more to have wireless Internet connectivity, cheaply and
easily. Proponents say that WiMAX wireless coverage will be
measured in square kilometers while that of Wi-Fi is measured in
square meters. According to WiMAX promoters, each WiMAX node or
"base station" would enable high-speed Internet connectivity for
homes and businesses in a radius of up to 50 km (31 miles). (It
should be noted that these claims, especially that such distances
can be achieved without line of sight, represent, at best, a
theoretical maximum under ideal circumstances. The technical merit
of these claims has yet to be tested in the real world.) These base
stations will eventually cover an entire metropolitan area, making
that area into a WMAN and allowing true wireless mobility within
it, as opposed to hot-spot hopping required by Wi-Fi. Its
proponents are hoping that the technology will eventually be used
in notebook computers and PDAs. True roaming cell-like wireless
broadband, however, will require 802.16e.
The original WiMAX standard, IEEE 802.16, specifies WiMAX in the 10
to 66 GHz range. 802.16a added support for the 2 to 11 GHz range,
of which many parts are already unlicensed internationally and only
few still require domestic licenses. Most business interest will
probably be in the 802.16a standard, as opposed to the higher
frequencies. The WiMAX specification improves upon many of the
limitations of the Wi-Fi standard by providing increased bandwidth
and stronger encryption. It also aims to provide connectivity to
network endpoints without direct line of sight in some
circumstances. The details of performance under near-line of sight
(NLOS) circumstances, are unclear, as they have yet to be
demonstrated. It is commonly considered that spectrum under 5-6 GHz
is needed to provide reasonable NLOS performance and cost
effectiveness for PtM (point to multi-point) deployments. WiMAX
makes clever use of multi-path signals but does not defy the laws
of physics.
