TABLE OF CONTENTS High-Speed Downlink Packet Access (HSDPA) is a radio technology included in UMTS 3GPP Release 5 specifications intended to increase the user peak data rates and quality of service in the downlink. In fact, the maximum data rate to a user in present UTRA networks achieved in ideal conditions is limited to 2 Mbps. The introduction of HSDPA to the UMTS specifications will potentially offer up to 10 Mbps downlink data rates in the same 5 MHz bandwidth, while remaining backward compatible with the UEs of Release 99. Quality of service is improved with dynamic adaptive modulation and coding, multi-code operation, fast scheduling and physical layer retransmissions.
HSDPA is well suited for providing interactive (e.g. Internet browsing), streaming (e.g. video on demand) and background end-user services. The doors of the "3.5G" are opened by this radio technology. However, HSDPA is just a first step in the evolution of UTRA: the second step will be to enhance uplink data rates, improve uplink capacity and reduce uplink delay [TS 25.309, R6]. Although HSDPA applies to both UTRA/FDD and UTRA/TDD variants, this chapter will explore exclusively the key technical aspects behind the HSDPA concept in the context of UTRA/FDD. Finally, note that the principles of HSDPA are also part of the evolution of cdma2000 networks.
In Release 5, the UTRA physical layer was enhanced with the introduction of a new transport channel called High-Speed Downlink Shared Channel (HS-DSCH). Consequently, four possible transport channels can...
