Cellular Digital Packet Data (CDPD) was an early technology that allowed 1G and 2G mobile networks in the U.S. to offer packet data services. It utilized the 800 MHz band’s full 30 kHz AMPS channels without interfering with voice channels. CDPD dynamically assigned packet channels to voice channels when available. The network overlaid the existing infrastructure, leveraging base stations, making it cost-effective to implement. CDPD operated as an IP network with a speed of 19.2 kbps, providing around 10 kbps throughput. With the advent of 2.5G and 3G systems, CDPD was phased out.