A Google search for Africa and American carriers such as T-Mobile, Verizon, or Sprint leads mostly to notes about their subscriber roaming options.
But this is an imperfect measure because it does not include additional roaming charges paid by subscribers, nor does it include taxes and other fees charged on those calls.
Sprint and Verizon both use CDMA technology, for instance, but that doesn't do their users any good, since both companies block each other's subscribers from roaming onto their digital networks).
Sprint and Verizon use CDMA technology, for instance, but that doesn't do their users any good, since both companies block each other's subscribers from roaming onto their digital networks).
Initially, China Unicom and Vodafone AirTouch will allow their subscribers to roam in each other's territories.
Its tie-up with China Mobile, for example, may give Far EasTone the right to allow its subscribers to roam onto China Mobile's network on the mainland, a potentially lucrative market given all that Taiwanese business travel.
The extra services, available only to AT&T Wireless customers or to outside subscribers who "roam" into AT&T territory, incur no additional charge atop the basic directory assistance fee of 99 cents.
Carriers like T-Mobile, AT&T, Nextel and Cingular also have global service plans for customers using G.S.M. phones, with rates ranging from $1 to several dollars a minute depending on the plan and the country where the subscriber is roaming.
"Through these agreements, iPass can enable its subscribers to roam seamlessly onto any of its partner networks," says Mr Kaplan.
The idea is that special software, installed in the networks of internet-service providers (ISPs), intercepts webpage requests generated by their subscribers as they roam the net.
