[IEEE] [802.11b] ([WiFi]) uses [DSSS], using 22MHz of bandwidth (passband) to transmit data with speeds of up to 11Mb/sec. A WiFi system can use any of 13 22MHz-wide sub-channels across the allocated 83.5MHz of the 2.4GHz frequency band, however most equipment commonly available in Australia is designed for the 11 channel American market.

22MHz wide Direct Sequence Spread Spectrum, 5MHz channel spacing.
||'''Channel'''||'''MHz'''||
||1||2412||
||2||2417||
||3||2422||
||4||2427||
||5||2432||
||6||2437||
||7||2442||
||8||2447||
||9||2452||
||10||2457||
||11||2462||
||12||2467||
||13||2472||

As such, there are only three non-overlapping channels: 1, 7 & 11.

(Source: Queensland Digital Group)