This is a common problem today for the 2.4-Ghz wifi band. Total BW [bandwidth] is only 80-Mhz,
which can accomodate only 3 wifi channels without severe overlap. And obviously, if you look
in your PC's "View Wireless Networks" window, you'll typically see a dozen of so wifi routers
within close proximity. Plus, XBee works in the same band, plus microwave ovens work at
the top of the same band.
Why does this even work at all? Mainly through something called spread-spectrum DSSS [not
the same as frequency-hopping, BTW],http://en.wikipedia.org/wiki/Direct-sequence_spread_spectrumhttp://en.wikipedia.org/wiki/Frequency-hopping_spread_spectrum
They also use multiple-access techniques to prevent conflicts.http://en.wikipedia.org/wiki/Multiple_access