The IEEE 802.16 WirelessMAN? Standard The
Institute of Electrical and Electronics Engineers Standards Association IEEE-SA
sought to make BWA more widely available
by developing IEEE Standard 802.16, which specifies
the WirelessMAN Air Interface for wireless metropolitan area
networks. The standard, which was published on 8
April 2002, was created in a two-year, open-consensus process
by hundreds of engineers from the world's leading operators
and vendors. IEEE 802.16 addresses the "first-mile/last-mile" connection in
wireless metropolitan area networks. It focuses on the efficient
use of bandwidth between 10 and 66 GHz the
2 to 11 GHz region with PMP
and optional Mesh topologies by the end
of 2002 and defines a medium access control MAC
layer that supports multiple physical layer specifications customized for
the frequency band of use. The 10 to
66 GHz standard supports continuously varying traffic
levels at many licensed frequencies e.g., 10.5,
25, 26, 31, 38 and 39 GHz for
two-way communications. It enables interoperability among devices, so carriers
can use products from multiple vendors and warrants
the availability of lower cost equipment. The
draft amendment for the 2 to 11 GHz
region will support both unlicensed and licensed bands. Telecommunications
Choices Business-based telecommunications encompasses many options. Major businesses
often access large-capacity, high-speed fiber optic networks for broadband,
converged services. Less than five percent of commercial
structures worldwide are served by fiber networks, however,
and extending these networks with cable is costly and
time consuming. Today, small businesses and residential customers
typically use wired networks such as cable modem
networks and DSL. Cable systems are based on residential
cable TV infrastructure, so they are often
not available in serving business subscribers. DSL is
a copper-based method that typically offers 128 kbps
to 1.5 Mbps data services, however service is
not available to every subscriber because of distance
limitations from the central office. DSL, cable and older
wireless systems tend to have low upstream bandwidth.
The same is true of another option, two-way
satellite transmission, which is still early in its
life cycle. While invaluable in some rural areas,
it has limited application in more populous locales due
to limited spectrum availability and high latency. IEEE Standard
802.16 BWA systems offer true differentiated broadband services
at minimal cost. They let thousands of users share
capacity for data, voice and video. They also are
scalable: carriers can expand them as subscriber demand for
bandwidth grows by adding channels or cells. Quality of
Service QoS in Broadband Wireless BWA transmission
is via free space, and is subject to
attenuation and distortion by various matter such
as vegetation, buildings, precipitation and vehicles, which move
and change unpredictably. IEEE Standard 802.16 recognizes
this and includes mechanisms to make robust links for
PMP BWA systems with line-of-sight. Obstructed line-of-sight and non
line-of-sight transmission are considered in the 2-11 GHz draft
amendment. Mechanisms in the WirelessMAN MAC
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