From GSM to LTE: An Introduction to Mobile Networks and Mobile Broadband

3.10 High-Speed Downlink Packet Access (HSDPA) and HSPA+

UMTS networks today no longer use DCHs for high-speed packet transfer. With 3GPP Release 5, HSDPA was introduced to be more flexible for bursty data transmissions and to deliver much higher datarates per cell and per user than before. As described in more detail in Section 3.13, speeds of several megabits per second or even higher can be reached when the user is close to the base station and has very good signal conditions.

Important standards documents that were newly created or enhanced for HSDPA are the overall system description Stage 2 in 3GPP TS 25.308 [13], the physical layer description TR 25.858 [14], physical layer procedures in TS 25.214 [15], Iub and Iur interface enhancements in TR 25.877 [16], RRC extensions in TS 25.331 [5] and signaling procedure examples in TS 25.931 [7].

3.10.1 HSDPA Channels

Figures 3.40 and 3.41 show how HSDPA combines the concepts of dedicated and shared channels. For user data in the downlink direction one or more High-Speed Physical Downlink Shared Channels (HS-PDSCH) are used. These can be shared between several users. Hence, it is possible to send data to several subscribers simultaneously or to increase the transmission speed for a single subscriber by bundling several HS-PDSCH where each uses a different code.

Figure 3.40 Simplified HSDPA channel overview in downlink direction.

Figure 3.41 Simplified HSDPA channel overview in uplink direction.

Each HS-PDSCH uses a spreading ...