High-Speed Packet Access
High-Speed Packet Access (HSPA) is a collection of mobile telephony protocols that extend and improve the performance of existing UMTS protocols. Two standards, HSDPA and HSUPA, have been established and a further standard, HSOPA, is being proposed.
The two existing standards (HSDPA and HSUPA) in the family provide increased performance by using improved modulation schemes and by refining the protocols by which handsets and base stations communicate. These improvements lead to a better utilization of the existing radio bandwidth provided by UMTS.
The number of commercial 3.5G networks–also known as High-Speed Downlink Packet Access, or HSDPA, networks–launched worldwide grew by 69 percent in 2007. There are now 174 commercial HSDPA networks in 76 countries. An additional 38 networks are committed to rollouts, which will bump the total to 211 HSDPA networks in 90 countries. Commercial HSDPA networks are widely available in Western Europe (61 networks), Southeast Asia (35), Eastern Europe (34), the Middle East and Africa (20), and the Americas and the Caribbean (16). Almost two-thirds (62 percent) of existing commercial HSDPA networks support downlink speeds of 3.6Mbps or more, while more than a fifth (21 percent) support the peak downlink speed of 7.2Mbps.
Many HSPA rollouts can be achieved by a software upgrade to existing 3G networks, giving 3.5G a headstart over WiMax, which requires dedicated network infrastructure. Rising sales of HSPA-enabled mobiles–aided by more-generous-than-expected operator subsidies of the hardware–are helping to drive the 3.5G market.
via [Wikipedia]