Page 199 - From GMS to LTE

Universal Mobile Telecommunications System (UMTS) and High-Speed Packet Access (HSPA) 185

UE Node-B S-RNC

Radio link reconfiguration prepare

Radio link reconfiguration ready
Radio link reconfiguration commit

Transport bearer setup

DCCH, RRC message: radio bearer reconfiguration
Incoming data
DCCH, RRC message: radio bearer reconfiguration complete for user

Flow control: capacity request

Flow control: capacity allocation
User data
Bandwidth allocation via HS-SCCH
User data

Figure 3.41 Establishment of an HSDPA connection.

and to inform the user’s mobile device via the shared control channels whenever it
sends data on one or more HS‐PDSCHs.
While the mobile device is in HSDPA reception mode, it has to constantly monitor all
assigned HS‐SCCH channels and also maintain the necessary DCHs. This of course
results in higher power consumption, which is acceptable while data is transferred. If no
data is transferred for some time, this state is quite unfavorable as the power consump-
tion remains high and thus the runtime of the mobile device decreases. This state is also
not ideal for the network as bandwidth on the air interface is wasted for the dedicated
channel of the HSDPA connection. Thus, the network can decide to release the HSDPA
connection after a period of time and put the subscriber into the Cell‐FACH state (see
Section 3.5.4). In this state, the mobile device can still send and receive data, but the
bandwidth is very small. Nevertheless, this is quite acceptable as an HSDPA connection
can be reestablished again very quickly, when required.

3.10.6 HSDPA Mobility Management
HSDPA has been designed for both stationary and mobile users. Therefore, it is necessary
to maintain the connection while the user is moving from cell to cell. For this reason,
the mobile device keeps a so‐called Active Set for the DCH of the HSDPA connection,
which is required for the soft handover mechanism, as described in Section 3.7.1. In
contrast to a pure dedicated connection, the mobile device only receives its data over