Archived from groups: alt.internet.wireless (
More info?)
On 13 Oct 2004 07:05:38 -0700, nedhart@hotmail.com (Ned Hart) wrote:
>My experience with wireless networking has been less than encouraging.
> At home or at the office, the connection is not 100% reliable. I do
>freelance tech work and I am now being asked to install a wireless
>network for a medical office. The best product I've ever uses came
>from Orinico (proxim now?), Cisco Aironet has also been good. Can
>anyone make recommendations for a reliable industrial strength
>wireless network that will not suffer from lost connections? Is there
>any such thing?
We'll have 100% reliable wireless when we have 100% reliable medicine.
Cisco and Proxim (Orinoco/Avaya/Agere/Lucent/Wavelan/Whatever) are
good products. If all you had to do is buy the "right" product, you
would have close to 100% reliability. However, you're not alone in
the wireless world and the 2.4GHz band is not your exclusive domain.
There are other users, microwave ovens, frequency hoppers, Bluetooth,
cordless phones, X10 TV links, plastic pre-heaters, RF excited lights,
ham radio, and other sources of interference. If this medical office
is in a high office building and exposed to such RF interference
because of its view of the surrounding metropolis, you're not going to
get anywhere near 100% reliability. Given sufficiently adverse
circumstances, you may not even be able to maintain a connection.
There's not much one can do to insure reliability other than massive
redundancy. That means 1 access point per room and a central router
to deal with soft roaming handoffs. My favorite of the week is:
http://www.symbol.com/products/wireless/ws5000_wireless_switch.html
However, this will do nothing if the client radio is the one picking
up the interference. A smart access point (wireless switch) isn't
going to work at all if the client radio is deaf.
Another form of redundancy is to use both 802.11g (2.4Ghz) and 802.11a
(5.6Ghz). There are cards that will do both and select the "best"
connection. If one band is trashed, the other takes over. I've never
actually done this but have heard of others doing this to improve
reliability. Most commodity grade manufactories have dual band
(802.11a/b/g) radios and access points. Cisco and Proxim apparently
do not.
Another method is to control the antenna pattern. This is tricky
indoors but the idea is to prevent any inside antennas from hearing
outside interference. Again, the problem of interference to the
client radio makes this method less than useful.
--
Jeff Liebermann jeffl@comix.santa-cruz.ca.us
150 Felker St #D
http://www.LearnByDestroying.com
Santa Cruz CA 95060 AE6KS 831-336-2558