Cdma2000 and UMTS were developed separately and are 2 separate ITU approved 3G standards. Cdma2000 1xRTT, cdma2000 1xEV-DO (EVolution, Data Only) and future cdma2000 3x were developed to be backward compatible with cdmaOne. Both 1x types have the same bandwidth, chip rate and it can be used in any existing cdmaOne frequency band and network. Backward compatibility was a requirement for successful deployment for USA market. It is easy to implement because operators do not need new frequencies. [more about cdma2000]
UMTS was developed mainly for countries with GSM networks, because these countries have agreed to free new frequency ranges for UMTS networks. Because it is a new technology and in a new frequency band, whole new radio access network has to be build. The advantage is that new frequency range gives plenty of new capacity for operators. 3GPP is overseeing the standard development and has wisely kept the core network as close to GSM core network as possible. UMTS phones are not meant to be backward compatible with GSM systems. (but subscriptions (=SIM card) can be, and dual mode phone will solve the compatibility problems, hopefully). UMTS also has 2 flavors FDD (will be implemented first) and TDD.
Some harmonisation has been done between systems (like chip rate and pilot issues)
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