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GSM is the cellular network used by US vendors Cingular and T-Mobile for voice and data communications. The data services are known as GPRS (General Packet Radio Service) (19.2kbit/s), EDGE (Enhanced Data rates for GSM Evolution) (200kbit/s) and UMTS (Universal Mobile Telecommunications System) (2mbit/s). The data services are an additional charge based on kilobytes sent or received or unlimited for a month depending on the plan chosen. Currently only Cingular offers UMTS in the US.
[http://www.pocketpcfaq.com/faqs/cellularprimer.htm|Cellular Data Primer]
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