Wireless Central Coordinated Protocol

[Darryl Smith]

Hi There....

This is an interesting solution to the issue of a hidden transmitter in
an 802.11b environment. My comment would be that I do not believe that
this is the correct solution to this issue. The 802.11b RTS/CTS concept
is as far as I can determine based on a 1990 paper by Phil Karn
(http://www.ka9q.net/papers/maca.html). Phil commented that you might as
well get rid of the CS or Carrier Sense since it is of not much use
because of the hidden transmitter problem. [Interestingly he also
commented that this setup is ideal for adding on power control]

The people who did 802.11b realised this and made the carrier sense part
almost optional. They created a virtual carrier sense called the Network
Allocation Vector which is really a Collision Advoidance problem rather
than a Carrier Sense.

In the access point situation, the ideal is that every user of the
access point should transmit exactly the correct ammount of power such
that every sigal from users arrive at the access point within 1 dB of
the required level. In this case, if you had a number of receieves in
your access point, each on average would detect a different user. Such
is the power of spread spectrum. And alas, no such access points exist.
This is how Qualcomms CDMA telephones work. 

Such power control would cause the users who are close in to not use so
much power as to block out those a long way out. This would also
minimise interference to other users - a requirement of using the
unlicensed bandwidth. The paper I am working on concerning power control
can be found on
http://www.radio-active.net.au/web/80211/powercontrol.pdf

Darryl

P.S. 


	"WCCP is a protocol booster for 802.11b DCF based wireless
networks, that provides cyclic token-passing medium access, 
	and scheduled allocation of the available network resources." 

You do realise that WCCP is the Web Cache Coordination Protocol don't
you?

---------
Darryl Smith, VK2TDS   POBox 169 Ingleburn NSW 2565 Australia
Mobile Number 0412 929 634 [+61 4 12 929 634 International] 
Darryl at radio-active.net.au | www.radio-active.net.au