High-speed downlink packet access (HSDPA) is a mobile communications protocol that belongs to the high speed packet access (HSPA) family. HSDP allows networks based on (UMTS) to have higher data transfer speeds.
Current HSDPA deployments support down-link speeds of 1.8MBPS, 3.6MBPS, 7.2MBPS and 14.4 MBPS. In the near future these speeds should increase greatly. The networks are then to be upgraded to Evolved HSPA, which provides speeds of 42MBPS downlink in its first release.
Being part of HSPA, HSDPA is a result of enhancements made on UMTS (Universal Mobile Telecommunications System). It is being standardized by the 3rd Generation Partnership Project (3GPP). Also, as it is a result of 3GPP initiatives, HSDPA is geared towards evolved GSM core networks.
HSDPA is just one half of the HSPA family. The other half being HSUPA. While HSDPA focuses more on high downlink speeds, HSUPA is designed for high uplink speeds. However, since HSPA network end users perform more downloads than uploads, HSDPA speeds are naturally much higher than HSUPA. This is also the reason why HSDPA systems are being deployed way ahead of their HSUPA counterparts.
Top-notch smartphones like the Apple iPhone 4, Nokia N8, BlackBerry Storm 2, HTC Desire S, and LG Optimus 2X support HSDPA. However, it is worth noting that not all devices that support HSDPA feature the same downlink speeds.
The downlink speed of an HSDPA device will depend on its category number. For example, a device with category 6 can have a 3.6 Mbps downlink rate, while a category 8 device can achieve a 7.2 Mbps downlink.
As of this writing, HSDPA deployments are still part of the first phase. In the second phase, HSDPA systems will be able to achieve up to 42 Mbps data rates. This is faster than some of today’s land-based broadband connections.
The latest experiments on HSPA downlink speeds carried out by Ericsson in laboratory conditions have been able to reach up to 168 Mbps.