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CDMA2000 1xRTT
CDMA2000 1xRTT, the core CDMA2000 wireless air interface standard, is also known as 1x, 1xRTT, and IS-2000. The designation "1x", meaning "1 times Radio Transmission Technology", indicates the same RF bandwidth as IS-95: a duplex pair of 1.25 MHz radio channels. This contrasts with 3xRTT, which uses channels 3 times as wide (3.75 MHz) channels. 1xRTT almost doubles the capacity of IS-95 by adding 64 more traffic channels to the forward link, orthogonal to (in quadrature with) the original set of 64. Although capable of higher data rates, most deployments are limited to a peak of 144 kbit/s. IS-2000 also made changes to the data link layer for the greater use of data services, including medium and link access control protocols and QoS. The IS-95 data link layer only provided "best effort delivery" for both voice and data.
1xRTT officially qualifies as 3G technology, but it is considered by some to be a 2.5G (or sometimes 2.75G) technology. This allows it to be deployed in 2G spectrum in some countries that limit 3G systems to certain bands.
CDMA2000 3x
CDMA2000 3x or EV-DO Rev. B utilizes a pair of 3.75 MHz radio channels (i.e., 3 X 1.25 MHz) to achieve higher data rates. The 3x version of CDMA2000 is sometimes referred to as Multi-Carrier or MC. The 3x version of CDMA2000 has not been deployed and is not under development at present.
CDMA2000 EV-DO
CDMA2000 EV-DV
CDMA2000 EV-DV (Evolution-Data/Voice), supports downlink (forward link) data rates up to 3.1 Mbit/s and uplink (reverse link) data rates of up to 1.8 Mbit/s. EV-DV can also support concurrent operation of legacy 1x voice users, 1x data users, and high speed EV-DV data users within the same radio channel.
In 2005, Qualcomm put the development of EV-DV on an indefinite halt, due to lack of carrier interest, mostly because both Verizon Wireless and Sprint are using EV-DO.
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