HSDPA in W-CDMA
High Speed Downlink Packet Access (HSDPA) is a packet-based data service in W-CDMA downlink with data transmission up to 8-10 Mbps (and 20 Mbps for MIMO systems) over a 5MHz bandwidth in WCDMA downlink. HSDPA implementations includes Adaptive Modulation and Coding (AMC), Multiple-Input Multiple-Output (MIMO), Hybrid Automatic Request (HARQ), fast cell search, and advanced receiver design.
In 3rd generation partnership project (3GPP) standards, Release 4 specifications provide efficient IP support enabling provision of services through an all-IP core network and Release 5 specifications focus on HSDPA to provide data rates up to approximately 10 Mbps to support packet-based multimedia services. MIMO systems are the work item in Release 6 specifications, which will support even higher data transmission rates up to 20 Mbps. HSDPA is evolved from and backward compatible with Release 99 WCDMA systems.
Currently (2002) 3GPP is undertaking a feasibility study on high-speed downlink packet access.
HSPDA and CDMA2000 1xEV-DV Comparison
Further reading:
3GPP TS 25.855 High Speed Downlink Packet Access (HSDPA); Overall UTRAN description
3GPP TS 25.856 High Speed Downlink Packet Access (HSDPA); Layer 2 and 3 aspects
3GPP TS 25.876 Multiple-Input Multiple-Output Antenna Processing for HSDPA
3GPP TS 25.877 High Speed Downlink Packet Access (HSDPA) - Iub/Iur Protocol Aspects
3GPP TS 25.890 High Speed Downlink Packet Access (HSDPA); User Equipment (UE) radio transmission and reception (FDD | 
