Wireless is now the area of networking receiving the greatest
investment in new technology development. There is a great
deal known about the propagation of conventional narrowband
and spread-spectrum wireless in the frequencies up
through about 5 GHz. Many promising wireless technologies
have also failed in the marketplace for which they were
intended. All of this is typical for an embryonic market such as
wireless networking. The following technologies are not yet
ready for full commercialization, much less for the industrial
market, which demands field-proven technologies. We often
refer to these not-yet-fully-developed technologies as the
bleeding edge. However, we must always be aware that market
development times have dramatically shrunk over the past
few years, with new technologies suddenly becoming "mainstream"
more rapidly than ever before.

5.1 WiMAX (Worldwide Interoperability for
Microwave Access)

WiMAX is based on some of the technology from two failed
markets: LMDS (local multipoint distribution service) and
MMDS (multichannel multipoint distribution service.) LMDS
was intended to be a digital wireless transmission system in
the 28 GHz range in North America and 24-40 GHz elsewhere.
The purpose of LMDS was to replace wired CATV (community
access television), otherwise known as cable TV. For this purpose,
LMDS acquired the oxymoronic title of wireless cable.
LMDS requires a clear line of sight between transmitter and
receiving antenna, which is from one to four miles apart,
depending on weather conditions. LMDS provides bandwidth
in the 51- 622 MHz range. This is considerably greater than
other wireless services, but is necessary for LMDS to accomplish
its original task of replacing wired analog cable TV systems. A few
operating LMDS systems remain to satisfy some rural customers,
but satellite TV eventually has satisfied the demands for the original
wireless cable market.