Good bandwidth makes the difference between VoIP that sounds terrible and jerky (and is not worth it) and VoIP that sounds every bit as good as your regular telephone.
When you are looking at bandwidth for VoIP on your mobile computer, you need to think about two network segments (see Part IV, “Your Own Wireless Network,” for more information about how these different parts of the network interoperate):
The pipeline from the Internet to your access point or router
The connection between your computer and the access point or router (At a public hotspot, this connection is provided by the hotspot's access point.)
There's not a whole lot you can do about the first of these, the Internet connection, other than try it and see. ...