IS-2000 is the second generation of CDMA digital cellular, an extension of IS-95. It is also known as CDMA-2000.
The main differences between IS-95 and IS-2000 signalling are: the use of a pilot on the IS-2000 reverse link to permit the use of coherent modulation, and 64 more traffic channels on the forward link that are orthogonal to the original set. Some changes were also made to the link layer to accomodate the greater use of data services - IS-2000 has media and link access control protocols and QoS control. In IS-95, none of these were present, and the link layer basically consisted of a "Best effort delivery" RLP - this arrangement is still used for voice.