Notes on UMTS channels

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The channels


The 9 Logical channels

They are divided in control channels (for the control plane) and traffic channels (for the user traffic).

The 6 control channels

This is were exchanges in the control plane take place

Acronym Channel name Broadcast / Unicast Direction RLC mode


BCCH Broadcast Control Channel Broadcast DL transparent
PCCH Paging Control Channel unicast DL
CCCH Common Control Channel unicast both
DCCH Dedicated Control Channel unicast both AM or UM
DTCH Dedicated Traffic Channel unicast both All modes

Channels can be broadcast (traffic is sent to every terminal listening), or unicast (trafic is targeted at some particular device, either the UE or the node B.
Directions are: DL = download (from network to terminal), UL = upload (from terminal to network), or both.

The 5 transport channels

Acronym Channel name Direction
BCH Broadcast Channel DL Used to broadcast some technical, service informations.
PCH Paging Channel DL Use by the network to communicate with the UE before the UE request communications.
RACH Random Access Channel UL Used for bidirectionnal communications (control and small data) when the UE doesn't have a dedicated channel.
FACH Forward Access Channel DL
DCH Dedicated Channel both Used when "heavy" communications take place, notably CS and PS in the user plane.

What about HS-DSCH and E-DCH ?

Physical channels

Mapping of the channels



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