tion of the WCDMA radio access continues standard, HSDPA brings further enhancements to the and will continue also in the future. For example, 3GPP provisioning of packet-data services in WCDMA, both in Release 7 introduces several new features. MIMO is terms of system and end-user performance. The down- a tool to further improve capacity and especially the link packet-data enhancements of HSDPA are comple- HSPA peak data rates. Continuous Packet Connectivity mented by Enhanced Uplink, introduced in Release 6 of aims at providing an 'always-on' service perception the 3GPP/WCDMA specifications. HSDPA and En- terminals. hanced Uplink are often jointly referred to as High-Speed In parallel to enhancements of the radio-access spec- Packet Access (HSPA). ifications, there is an ongoing effort in advanced receiver As discussed in Chapter 4.2, important requirements structures. These improvements, which can provide for cellular systems providing packet-data services are a significant gain in both system and end-user perfor- high data rates and low delays while, as at the same time, mance, are to a large extent implementation specific, maintaining good coverage and providing high capacity. although the receiver-performance requirements as such To achieve this, HSPA introduces several of the basic are subject to standardization. techniques into WCDMA, such as higher order modu- As a summary, the evolution of WCDMA is illustrated lation, fast (channel-dependent) scheduling and rate in Figure 4.6-1. control, and fast hybrid ARQ with soft combining. The remainder of this chapter contains an overview of Altogether, HSPA provides downlink and uplink data the first release of WCDMA. The intention is to provide rates up to approximately 14 and 5.7 Mbit/s, re- the reader with an understanding of the foundation upon spectively, and significantly reduced round trip times and which HSPA and MBMS are built. The reader already improved capacity, compared to Release 99. familiar with WCDMA may want to skip the remainder 3GPP Release 6 