Check for Dual-Band Interference

Check for Dual-Band Interference
Despite the industry’s mad rush to wirelessly enable every networkable
device that it makes, a whole lot hasn’t been worked through yet, particularly
interoperability. We’re not talking about whether one vendor’s 802.11b PC
Card will work with another vendor’s 802.11b AP — the Wi-Fi interoperability
tests usually make sure that’s not a problem (unless one of your products isn’t
Wi-Fi certified). Instead, we’re talking about having Bluetooth (see Chapter 15
for more on this technology) working in the same area as 802.11b, or having
802.11a modems and 802.11b modems operating in the same area. In some
instances, like the former example, Bluetooth and 802.11b operate in the
same frequency range, and therefore do have some potential for interference.
Because 802.11a and 802.11b operate in separate frequency bands, they’re
less likely to be exposed to interference.
There are also issues with how the different standards are implemented in
different products. Some APs that support 802.11b and g, for instance, really
support one or the other — not both simultaneously. If you have all g in your
house, great. If you have all b, great. If you have some g and the AP detects
that b is in the house, it will downshift to b rates. You might be all set, but
then your neighbor upstairs buys a b modem (because you’ve said, “Sure, no
problem, you can share my Internet connection.”). Not only is he freeloading,
but he’s probably forcing your whole AP to shift down to the lower speeds.
To be fair, many of these very early implementation issues are rapidly going
away while vendors refine their solutions. Check out how any multi-mode AP
that you buy handles multiple forms of wireless connecting to the AP and
asking for service. Some of the newer APs compartmentalize their signal so
that they can handle two at once, which is very nice and almost necessary.