Code division Multiple access 2000 is the neutral evolution of IS-95. (cdmaOne). It includes additional functionality that increase its spectral efficiency and data rate capability.
CDMA is a method in which multiple users occupy the same time and frequency allocations and are channelized by unique assigned codes. The signals are separated at the receiver by using a correlator that accepts only signal energy from the assigned Code Channel. The channels are defined with codes (PN sequences). All other signals in that frequency band contribute only to the noise.
Three main CDMA2000 standards are:
CDMA2000 1Xrtt support both voice and data services over the standard 1.25MHz CDMA channel. The 1x in the name signifies that it uses one 1.25MHz channel. Due to improved modulation, power control, and overall design, it can achieve theoretical data transfer rates of 144Kbps
There are two members of CDMA2000 1Xev Family:
CDMA2000 1x Evolution Data Optimized
CDMA2000 1x Evolution Data and Voice
The CDMA2000 1x EVDO supports greater than 2 Mbps of instantaneous high speed packet throughput per user on a CDMA channel, although the data rates are much lower and highly dependent on other factors
The CDMA2000 1x EVDV can offer data rates up to 144 kbps with about twice as many voice channels as IS-95B
Base station timing synchronization in CDMA2000 can provide decreased latency and a reduced chance of dropping calls during soft handoff
Since both WCDMA and CDMA2000 have been simultaneously adapted for the 3G standard, harmonization of these two systems becomes necessary to make IMT-2000 deployment successful.
To create a single integrated 3G CDMA specification and process the separate W-CDMA and CDMA proposals being developed by 3GPP and 3GPP2