High speed packet access ( HSDPA )

HSDPA is a downlink only air interface defined in the Third generation Partnership Project (3GPP) UMTS Release 5 specifications. HSDPA is capable of providing a peak user data rate (layer 2 throughput) of 14.4Mbps, using a 5MHz channel. Realizing this data rate, however, requires the use of all 15 codes, which is unlikely to be implemented in mobile terminals. Using 5 and 10 codes, HSDPA supports peak data rates of 3.6Mbps and 7.2Mbps, respectively. Typical average rates that users obtain are in the range of 250kbps to 750kbps. Enhancements, such as spatial processing, diversity reception in mobiles, and multiuser detection, can provide significantly higher performance over basic HSDPA systems.

It should be noted that HSDPA is a downlink only interface; hence until an uplink complement of this is implemented, the peak data rates achievable on the uplink will be less than 384kbps, in most cases averaging 40kbps to 100kbps. An uplink version, HSUPA (high speed uplink packet access), supports peak data rates up to 5.8Mbps and is standardized as part of the 3GPP Release 6 specifications; deployments are expected in 2007. HSDPA and HSUPA together are referred to as HSPA (high speed packet access).