Cellular digital packet data network

Cellular digital packet data (CDPD) is a data network designed to meet growing mobile data transmission needs. CDPD networks can stand alone or overlay on the cellular voice system by drawing radio resources from the pool of unused or free cellular analog voice channels. Detection as to whether a channel is free or occupied is mechanized through channel sniffers. Once the CDPD network seizes a channel, it continues to use the channel as long as it is free and leaves the channel within 40 ms of initiation of any voice activity on the channel-the CDPD network then hops to another free channel, if available. CDPD follows slotted nonpersistent digital-sense multiple access with collision detection (DSMA/CD). In addition, it performs channel-error detection and channel-error recovery. We investigate several aspects of the CDPD network, namely, the: (1) effect of CDPD on cellular voice and (2) the delay-throughput performance due to DSMA/CD with error detection.