CDPD:

CDPD (Cellular Digital Packet Data) is a digital wireless transmission system that supports packet-switching over a cellular phone without a persistent connection. For example, e-mail is forwarded without a link being established.

CDPD transmits data at 19.2 Kbps (actual throughput is approximately 9.6 Kbps). This service is available from AT&T, GTE Wireless, and other cellular services.