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CDPD (Cellular Digital Packet Data) is a two-way voice and data standard based on AMPs infrastructure, begun in 1993. It is a packet-switched (vs. circuit switched) data service. It competes with other packet-switched wide area networks (WANs) such as ARDIS and RAM.
The CDPD "value proposition" is to augment the existing AMPs infrastructure to provide ubiquitous coverage for sending brief messages during cellular "dead spaces" using proven technology. The present estimate is that 30% of cellular air-time is available "deadspace" (from study of speech) for CDPD use. The expected cost of handsets is in the $500 to $2000 range; messaging service costs approximately $35 / month.
"Pros" of CDPD:
- Can be deployed at practically every cellular site in the nation.
- Is unobtrusive to analog cellular (TDMA, CDMA data are not)
- Uses the standard OSI model and familiar suites of protocols, such as Transmission Control Protocol / Internet Protocol for data transmission
- Is supported and subsidized by the "Baby Bells" and cellular providers
- Allows service providers to maximize infrastructure investment
"Cons" of CDPD:
- Requires additional equipment be added to cellular infrastructure: Digital transceivers in base stations (@ ~ $50k/base station), Mobile Data Management Systems in Switching Offices
- Won't work with existing analog phone - requires a digital handset
- Requires a "vertical" sell to customers
- Cost effective data transmission estimated to be 2 kbits or less (equivalent to a full terminal screen of data); for larger capacities, circuit-switched networks may be more cost effective
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