CDPD is a packet radio-like overlay on top of the traditional AMPS network. Of all wireless networks, CDPD dominates the position as the fastest widely deployed network in the United States. CDPD provides a raw radio data rate of 19.2kbps (near 14.4kbps after overhead), and covers over 95% of all metropolitan areas. CDPD uses unused analog cellular channels in a frequency-hop fashion, however, AT&T has recently allocated a dedicated channel in each sector at each site to appeal more to public safety customers.
CDPD is realitively easy to impliment, allowing the use of traditional AMPS radio hardware. Special CDPD-based modems and telephones access this network.
CDPD primary is used in telemetry, tracking of vehicles, dispatching, traffic lights, kiosks, POS terminals, credit card authorization, and police and fire vehicles. It recently has taken off even more with the use of PCMCIA laptop cards, palm pilot modems (promoted recently by Omnisky), and some cellular phones
CDPD rates are realitively cheap. As of this date, unlimited access for handhelds is $29.99/mo, and for laptops $54.99/mo. A CDPD modem provides you a real static IP connection, employs multiple layers of encryption between the user end equipment and the gateway in Bothel, WA, and has typically low ping times around 300-400ms. Several T1 "backbones" span the country, backhauling all data to the Bothel, WA location, where it is either sent directly to the Internet, or passed long FrameRelay links between corperate intranets and the CDPD network.
For more information, check under business/wireless ip on http://www.attws.com/
