HSDPA (High Speed Downlink Packet Access) marks a similar boost for WCDMA that EDGE does for GSM. It provides a two-fold increase in air interface capacity and a five-fold increase in data speeds in the downlink direction. HSDPA also shortens the round-trip time between the network and terminals and reduces variance in downlink transmission delay.
Nokia Research Center Dallas completed the HSDPA demonstration in January 2003 as a first demo at Nokia on this topic.
See the video clip (WMV file, 10.5 MB) The improvements in performance are achieved by:
- bringing some key functions, such as scheduling of data packet transmission and processing of retransmissions (in case of transmission errors) into the base station - that is, closer to the air interface
- using a short frame length to further accelerate packet scheduling for transmission
- employing incremental redundancy for minimizing the air-interface load caused by retransmissions
- adopting a new transport channel type, known as High Speed Downlink Shared Channel (HS-DSCH) to facilitate air interface channel sharing between several users
- adapting the modulation scheme and coding according to the quality of the radio link.
Demonstration
The demonstration video clip highlights the main features of HSDPA by showing the following:
- A DVD-quality streaming video application running over a complete HSDPA radio system. In this demonstration, the layer 1 supports of data-rate of up to 10Mbps.
- The link adaptation feature by showing how the signal constellation changes from 16-QAM (Quadrature Amplitude Modulation) to QPSK (Quadrature Phase Shift Keying) by introducing interference in the wireless link.
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