Written by: Stefan Parkvall, Eva Englund, Peter Malm, Tomas Hedberg, Magnus Persson and Janne Peisa

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Compared to second-generation systems, one of the most important aspects of third-generation mobile systems is enhanced packet-data access. WCDMA Release 99 provides data rates of 384 kbit/s for wide area coverage and up to 2 Mbit/s for hot-spot areas, which is sufficient for most existing packet-data applications. However, as the use of packetdata services increases and new services are introduced, greater capacity will be required. WCDMA Release 5 extends the specification with, among other things, a new downlink transport channel that enhances support for interactive, background, and to some extent, streaming services, yielding a considerable increase in capacity compared to Release 99. It also significantly reduces delay and provides peak data rates of up to 14 Mbit/s. This enhancement, which commonly goes under the abbreviation, HSDPA, is the first step of evolving WCDMA to provide even more outstanding performance. The authors describe the basic principles used by this enhancement and how they are incorporated into the specification and products. They also explain the associated system and end-user benefits.

[First published in Ericsson Review no. 02, 2003]