Page 147 - From GMS to LTE

Universal Mobile Telecommunications System (UMTS) and High-Speed Packet Access (HSPA) 133

Figure 3.10 User and control Control plane User plane
planes.
Core network
CC, MM Voice or
GMM/SM IP packets

RRC messages End-to-end bearer

Radio network
(UTRAN)

Terminal

Dedicated channels: These channels transfer data for a single user. A dedicated
channel is used, for example, for a voice connection, for IP packets between the user and
the network or a Location Update message.
Common channels: The counterpart to a dedicated channel is a common channel.
Data transferred in common channels is destined for all users of a cell. An example for
this type of channel is the broadcast channel, which transmits general information
about the network to all users of a cell in order to inform them of, for example, the
network the cell belongs to, the current state of the network, and so on. Common chan-
nels can also be used by several devices for the transfer of user data. In such a case, each
device filters out its packets from the stream broadcast over the common channel and
only forwards these to higher layers of the protocol stack.
Shared channels: Very similar to common channels are shared channels. These
channels are not monitored by all devices but only by those that have been instructed
by the network to do so. An example of such a channel is the High‐Speed Downlink
Shared Channel (HS‐DSCH) of HSDPA (see Section 3.10).

3.4.3 Logical, Transport and Physical Channels
To separate the physical properties of the air interface from the logical data transmission,
the UMTS design introduces three different channel layers. Figure 3.11 shows the channels
on different layers in downlink direction while Figure 3.12 does the same for uplink channels.

BCCH PCCH CTCH CCCH DCCH DTCH

BCH PCH FACH DCH DSCH

P-CCPCH S-CCPCH DPDCH DPCCH PDSCH

Figure 3.11 Logical, transport and physical channels in downlink direction (without HSPA).