cdma2000 is a third-generation (3G) wireless technology that is evolved from existing CDMA 2G technology. Its main features are faster data rates, always-on data service, and improved voice network capacity (more people can use each tower at the same time).
cdma2000 was deployed in several phases.
The first, 1xRTT, supports up to 144 Kbps packet data speeds. It also doubled voice capacity over previous CDMA networks (IS-95).
The next release of 1x, 1xEV-DO Release 0, supports peak data rates up to 2.4 Mbps.
1xEV-DO can only be deployed separately from voice networks - in its own spectrum - although devices can be made to access both networks. Therefore 1xRTT networks must continue to exist side-by-side 1xEV-DO networks, with the former handling voice and the latter handling high-speed data.
An upgrade called 1xEV-DO Revision A increases the maximum download data rate to 3.1 Mbps, among other performance improvements.
Another version called 1xEV-DV was originally proposed. It would have fully integrated data and voice, replacing 1xRTT completely. It was abandoned before it was ever deployed.