Wireless data transceivers of useful speed, range and cost are now available,
and others are working on networks
similar in concept to the UPN.
August 2002 update
Software based wireless data transceivers and other technical advances will make self-scaling high-bandwidth mesh networks practical.
The following letter appeared in a Slashdot discussion. It describes the situation and the possibilities.
{start of quote}
After listening to the 2 HOUR stream... (Score:2)
by Alsee on
Sunday June 02, @02:03PM (#3626980)
(User #515537
Info | http://slashdot.org/)
It seems clear many posts are off the mark.
There were two
main subjects. Software radio and how networking affects spectrum capacity.
Note that this has
little or nothing
to do with UWB (ultrawideband).
(1) Software
radio: This technology is still expensive, but costs are dropping rapidly.
Normal radios are hardware
designed for
specific tasks, work at a specific frequency band, use fixed modulation
schemes, and fixed energy
levels. A software
radio does all the work with a CPU. Just load up a new program and all
aspects of the device are
upgradeable.
One device can work as a digital or analog cellphone using US or european
protocall, or any future
protocall. It
can be reprogramed as a CB, TV, Walkie-talkie, HAM radio, beeper, intercom,
802.11, or bluetooth
device. Heck,
you could leave it on your dashboard as a police-radar detector. New protocalls
can be downloaded
on-the-fly.
You can then upgrade the system without replacing $billions of obsolete
hardware. Bandwidth
can also be
dynamically allocated were it is needed. Much radio capacity currently
goes to waste - it's like
reserving 15%
of your bandwith for browsing, 10% for streaming audio, 20% for video,
20% for games, 5% for
email, 15% for
FTP, etc. Current regulations are an obstacle to software radio.
(2) Second was an analysis of the obsolete paradigm of treating radio
spectrum as "property". This was based on a
fundamental
result that data capacity is equal to bandwidth, and that bandwidth is
limited. The more devices in
the system,
the less data capacity each device can get. Try to use 1000 cellphones
(or wireless laptops) in one
place and the
system dies. This is a result of analyzing a simple point-to-point or broadcast
system. New systems
working as a
network throw the old rules out the window. With the proper protocalls
each device added to the
system can increase
total capacity enough so that with more devices in the system, each device
still gets the
same data capacity.
Data capacity per device is no longer a limited resource. It is also based
on an obsolete
interpertation
of interference. In current radios, when two signals at the same frequency
arrive at the same place
there is interference
and the information is lost. This is merely a flaw of current designs.
Using "smart" antennas
multiple signals
at the same frequence can be received without interference. It turns out
that multi-path
"interference"
can actually increases capacity, as does motion. It also allows lower power
levels to be used. These
results fly
in the face of traditional electrical engineering, but they are solid physics/mathematical
results. (Watch
the presentaion
[fcc.gov] before you argue that I'm wrong.)
In the next serveral
years we may be in for a radical change in the way radio is used and regulated.
These changes
will enable
"always-on" wearable networked computing.
{end of quote}