CDPD stands for Cellular Digital Packet Data. It offers mobile users access to a low cost, wireless data network. CDPD can be overlaid on AMPS and IS-136 systems and share its infrastructure equipment on a noninterfering basis. Although it can be assigned to a dedicated RF-channel, it transmits packet data over idle cellular voice channels and automatically switches to another channel when the current channel is about to be assigned for voice usage.

It does not communicate with underlying cellular network.

It takes advantage of its knowledge of channel assignment algorithms for cellular system and predicts the channels available for CDPD use.

CDPD supports connectionless network services (CLNS) where every packet called a protocol data unit (NPDU) and it is routed individually based on the destination

Address of the packet and also the current network topology.

CDPD provides two network services:

1. The Standard OSI connectionless network protocol
2. Internet protocol.