The original CDPD specifications were based on Central Signaling Channel No. 7. The concept has been modified to use OSI protocols and frame relay for the interface towards wired networks, as well as well-known access methods and link layer protocols for the wireless channels. For network services, CDPD is supported by the IP protocol and the Connectionless Network Protocol( CLNP).
CDPD uses the 30 kHz wide voice channels of cellular voice transmission. Since wireless data transmission is more error-prone, CDPD uses a secure modulation technique to improve the error rate. Therefore, CDPD transmits 1 bit per baud to compensate for the problems in wireless transmission. In addition, the technique uses forward error correction( FEC). The data rate of CDPD is relatively low due to the method used. CDPD is no longer being developed further.