Overview

The first step in the evolution of WCDMA radio access is the introduction of High Speed Downlink Packet Access(HSDPA) in Release 5 of the 3GPP/WCDMA specifications. Although packet-data communication is supported already in the first release of the WCDMA standard, HSDPA brings further enhancements to the provisioning of packet-data services in WCDMA, both in terms of system and end-user performance. The downlink packet-data enhancements of HSDPA are complemented by Enhanced Uplink, introduced in Release 6 of the 3GPP/ WCDMA specifications. HSDPA and Enhanced Uplink are often jointly referred to as High-Speed Packet Access(HSPA).

As discussed in Chapter 2, important requirements for cellular systems providing packet-data services are high data rates and low delays while, as at the same time, maintaining good coverage and providing high capacity. To achieve this, HSPA introduces several of the basic techniques described in Part II into WCDMA, such as higher order modulation, fast (channel-dependent) scheduling and rate control, and fast hybrid ARQ with soft combining. Altogether, HSPA provides downlink and uplink data rates up toapproximately 14 and 5.7 Mbit/s, respectively, and significantly reduced round trip times and improved capacity, compared to Release 99.

3GPP Release 6 also brings efficient support for broadcast services into WCDMA through the introduction of Multimedia Broadcast Multicast Services (MBMS), suitable for applications like mobile TV. With MBMS, multiple terminals may receive the same broadcast transmission instead of the network transmitting the same information individually to each of the users. Naturally, this will lead to an...