Mobile wireless broadband is not to be confused with WiFi.

To quote the iBurst homepage:

[quote] Mobile broadband is different from portable wireless broadband, just as a mobile phone is different to a cordless phone. Your cordless phone works in close proximity to your phone line, but if you move too far away, you'll lose your connection. Your mobile phone however, can move from cell to cell without dropping calls. Similarly, portable wireless broadband service only works if you stay within the cell coverage area. If you want to move beyond that cell, you need a true mobile broadband service. [/quote]

Examples (in Australia) are iBurst and Unwired.

[:iBurstDrivers] - get your iBurst connection up and running.