QNC is a 2G data technology for circuit-switched 2G wireless networks such as CDMA (IS-95, not 1xRTT). It allows a data-enabled mobile device to quickly establish a direct, time-based data session to the Internet at up to 14.4 Kbps, via an IP router on the carrier's network.
QNC has mostly been superseded by newer, faster, all-IP data technologies such as 1xRTT and EV-DO.
At the time it was introduced, QNC was an improvement over previous CSD (circuit-switched data) systems that operated over slower wireless voice circuits. It was also an improvement over asynchronous data connections that took longer to initiate and required configuration for a specific modem at the other end.