On Sun, 06 Apr 2008 20:36:28 GMT, "~~Alan~~"
Post by ~~Alan~~Cross posted in 0.verizon.wifi........
In a couple of weeks, I'm going to have about 21 users connecting wirelessly
for some non-intensive work. I have an older Linksys WAP54G wireless access
point, 802.11g. Will this device be able to handle 21 users/connections
without any problems. Everybody is going to be in one large social hall
type room.
~alan
Experimentation in the 70's at University of Hawaii (called Aloha)
with one server and several nodes in contention for service yielded
about 18% efficiency. What you have is analogous to that. Slotted
Aloha improved it somewhat by reducing contention by giving each node
a time slot but in any event the bandwidth will not be split evenly
nor will it be effectively anywhere near the bandwidth capability of
the WAN connection. Aloha was a narrowband system on FM so modern
performance is better, but only in the magnitude of the numbers, the
averages are the same and the contention principles are identical.
802.11g gets 19Mbps throughput on a 54Mbps channel data rate. Assuming
nearly equal signal strength across the location and equal
opportunities for each node (ignoring the likely "capture effect" due
to proximity of any node to the WAP), look for an average throughput
of about 0.2 * (19Mbps / 21) or about 180kbps for any node if they are
all trying to do similar things on the net (like accessing some web
page in a class). This is optimal sharing, capture effect or one node
at a time will have full BW for a short interval until one unit
supercedes another. UPnP frames, MS's server browsing service and
other noisy protocols can also degrade the channel performance. As
long as the usage is "low intensity", casual use should not be a
problem.
If performance needs improvement put multiple nodes in the area on
different channels and disperse the traffic. Use alternate channels,
not adjacent ones. (1, 6, 11 should be the channels used to avoid
adjacent channel interference if you have that many WAPs)
If all the computers are .11g and not .11b you will be better off. If
you mix b's with g's the performance of the g-nodes will suffer.