high speed downlink packet access (HSPA) (HSDPA)
High Speed Downlink Packet Access (HSDPA) and High Speed Uplink Packet Access(HSUPA) are extensions of the UMTS standard towards higher transmission speeds. HSDPA for the downlink, HSUPA for the uplink.
HSDPA technology, defined by the Third Generation Partnership Project( 3GPP), uses packet-based data service in Wideband Code Division Multiple Access(WCDMA), the broadband access method standardized by the European Telecommunications Standards Institute( ETSI) for 3.5 generation( 3.5G) mobile networks. The data rate for downlink transmission is between 8 Mbit/s and 10 Mbit/s; for Multiple Input Multiple Output( MIMO) even 20 Mbit/s with a 5 MHz wide transmission channel.
The HSDPA architecture has a parallel structure that enables high data throughput at low clock rates. HSDPA uses an improved modulation technique, a combination of quadrature phase shift keying( QPSK) and quadrature amplitude modulation (16QAM), which in combination with a special compression, the Turbo Codec, achieves data transmission speeds ofup to 21.6 Mbps. Diversity methods are also used to increase the data rate, such as antenna or receiver diversity. In addition, HSDPA is characterized by extremely short response times, which can be as short as 2 ms.
The advantage of HSDPA over the faster WiMAX lies in the infrastructure. HSDPA is designed for mobile applications and only requires a software download for cell phones, and additional HSDPA cards for notebooks in order to work in the existing UMTS networks. WiMAX, on the other hand, requires a completely new communications infrastructure.
HSDPA, which has been incorporated into the 3GPP standards, defines the 3.5 generation (3.5G) of mobile networks.