"The CDMA2000 1xEV-DO cell phone system is defined under IS-856 rather than IS-2000 that defines the other CDMA2000 standards, and as the name indicates it only carries data. In Release 0 of the standard the maximum data rate was 2400 Mbps in the forward (downlink) with 153 kbps in the reverse (uplink) direction, the same as CDMA2000 1X. However in the later release of the standard, Release A, the forward data rate rises to 3.1 Mbps, and 1.2 Mbps in the reverse direction."