Logical Channels:
Broadcast Control Channel (BCCH), (downlink). This
channel broadcasts information to UEs relevant to the cell, such as radio
channels of neighbouring cells, etc.
Paging Control Channel (PCCH), (downlink). This
channel is associated with the PICH and is used for paging messages and
notification information.
Dedicated Control Channel (DCCH), (up and downlinks)
This channel is used to carry dedicated control information in both directions.
Common Control Channel (CCCH), (up and downlinks).
This bi-directional channel is used to transfer control information.
Shared Channel Control Channel (SHCCH),
(bi-directional). This channel is bi-directional and only found in the TDD form
of WCDMA / UMTS, where it is used to transport shared channel control
information.
Dedicated Traffic Channel (DTCH), (up and downlinks).
This is a bidirectional channel used to carry user data or traffic.
Common Traffic Channel (CTCH), (downlink) A
unidirectional channel used to transfer dedicated user information to a group of
UEs.
Transport Channels:
Dedicated Transport Channel (DCH), (up and downlink).
This is used to transfer data to a particular UE. Each UE has its own DCH in
each direction.
Broadcast Channel (BCH), (downlink). This channel
broadcasts information to the UEs in the cell to enable them to identify the
network and the cell.
Forward Access Channel (FACH),(down link). This is
channel carries data or information to the UEs that are registered on the
system. There may be more than one FACH per cell as they may carry packet data.
Paging Channel (PCH) (downlink). This channel carries
messages that alert the UE to incoming calls, SMS messages, data sessions or
required maintenance such as re-registration.
Random Access Channel (RACH), (uplink). This channel
carries requests for service from UEs trying to access the system
Uplink Common Packet Channel (CPCH), (uplink). This
channel provides additional capability beyond that of the RACH and for fast
power control.
Downlink Shared Channel (DSCH) (downlink).This channel
can be shared by several users and is used for data that is "bursty" in nature
such as that obtained from web browsing etc.
Physical Channels:
Primary Common Control Physical Channel (PCCPCH)
(downlink). This channel continuously broadcasts system identification and
access control information.
Secondary Common Control Physical Channel (SCCPCH)
(downlink) This channel carries the Forward Access Channel (FACH) providing
control information, and the Paging Channel (PACH) with messages for UEs that
are registered on the network.
Physical Random Access Channel (PRACH) (uplink). This
channel enables the UE to transmit random access bursts in an attempt to access
a network.
Dedicated Physical Data Channel (DPDCH) (up and
downlink). This channel is used to transfer user data.
Dedicated Physical Control Channel (DPCCH) (up and
downlink). This channel carries control information to and from the UE. In both
directions the channel carries pilot bits and the Transport Format Combination
Identifier (TFCI). The downlink channel also includes the Transmit Power Control
and FeedBack Information (FBI) bits.
Physical Downlink Shared Channel (PDSCH) (downlink).
This channel shares control information to UEs within the coverage area of the
node B.
Physical Common Packet Channel (PCPCH). This channel
is specifically intended to carry packet data. In operation the UE monitors the
system to check if it is busy, and if not it then transmits a brief access
burst. This is retransmitted if no acknowledgement is gained with a slight
increase in power each time. Once the node B acknowledges the request, the data
is transmitted on the channel.
Synchronisation Channel (SCH) The synchronisation
channel is used in allowing UEs to synchronise with the network.
Common Pilot Channel (CPICH) This channel is
transmitted by every node B so that the UEs are able estimate the timing for
signal demodulation. Additionally they can be used as a beacon for the UE to
determine the best cell with which to communicate.
Acquisition Indicator Channel (AICH) The AICH is used
to inform a UE about the Data Channel (DCH) it can use to communicate with the
node B. This channel assignment occurs as a result of a successful random access
service request from the UE.
Paging Indication Channel (PICH) This channel provides
the information to the UE to be able to operate its sleep mode to conserve its
battery when listening on the Paging Channel (PCH). As the UE needs to know when
to monitor the PCH, data is provided on the PICH to assign a UE a paging
repetition ratio to enable it to determine how often it needs to 'wake up' and
listen to the PCH.
CPCH Status Indication Channel (CSICH) This channel,
which only appears in the downlink carries the status of the CPCH and may also
be used to carry some intermittent, or "bursty" data. It works in a similar
fashion to PICH.
Collision Detection/Channel Assignment Indication Channel
(CD/CA-ICH) This channel, present in the downlink is used to indicate
whether the channel assignment is active or inactive to the UE.
