Basically most of the UMTS networks in operation are Frequency Division Duplex (FDD) based. There is also another variant called the Time Division Duplex or TDD.
Notice, we have two kinds of TDD.
One is WTDD (Wideband TDD) that uses normal 5MHz bandwidth. There is also another name for WTDD is High Chip Rate TDD (HCR-TDD).
The other is NTDD (Narrowband TDD). NTDD has another name as Low Chip Rate TDD(LCR-TDD). This is call as TD-SCDMA or Time division synchronous CDMA.
"Synchronous" implies that uplink signals are synchronized at the base station receiver, achieved by continuous timing adjustments. This reduces the interference between users of the same timeslot using different codes by improving the orthogonality between the codes, therefore increasing system capacity, at the cost of some hardware complexity in achieving uplink synchronization.
The normal bandwidth of FDD or TDD mode of operation is 5 MHz. This gives a chip rate of 3.84 Mcps (Mega chips per second). The corresponding figure for TD-SCDMA is 1.66 Mhz and 1.28 Mcps.
参考：3G and 4G Wireless Blog
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