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WCDMA UPLINK AND DOWNLINK CHANNELS

A channel represents the logical connection between the UE andthe Radio Access Network. They are physically represented by a

Chanellisation code used between the RBS and UE. They are

controlled, howeer, by the RNC along with the rest o! the radio

resources. "e hae three di!!erent types o! channels, with each

type being #apped into the ne$t as shown in %igure &'().

What am I transporting?

User  Data or  Control DataLogical

eg DCCH!

D"CH! #CCH

"o $hom am I transporting?

De%icate% or  Common"ransport

eg #CH! PCH!

&ACH! 'ACH!

HS(DSCH

Ph)sical

One ph)sical channel *ses + Channelisation co%e

Figure 4-19: WCDMA Channel Types

LOGICAL CHANNELS 

Logical channel types refer  to the type of  information being transmitted,and

 

are 

classified 

into 

two 

groups:

•   Control channels for  the transfer  of  control information

•   "ra,,ic channels for  the transfer  of  user  information.

A brie! description o! the logical channels !ound in theuplink 

 

• The Broadcast Control Channel +BCC- is a downlink 

channel !or broadcasting syste# in!or#ation.

• Paging Control Channel +CC- is a downlink channel that

trans!ers paging in!or#ation and is used when the UE is in idle#ode.

• The Common Control Channel +CCC- is a bi'directional

channel that trans!ers control in!or#ation between the network 

-

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  (1. WCDMA CHANNEL S"'UC"U'E

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and UE. This channel is used by the UE needs to accessthenetwork.

•

The Dedicated Control Channel +5CC- is a point'to'point bi'directional channel that trans#its dedicated

control in!or#ation between UE and the network. This

channel is established through a RRC connection setup

 procedure.

• The Dedicated Traffic Channel +5TC- is a point'to'poi

TRANSPORT  CHANNELS 

A transport channel is de!ined by how, and with what

characteristics, data is trans!erred oer the air inter!ace. There aretwo types o! transport channels*

( Co##on channels

4 5edicated channels.

Co##on channels are broadcast to eeryone in the cell,whereasdedicated channels are trans#itted and receied !ro# one use

only. A brie! description o! so#e o! the transport channels

 

• There is one dedicated transport channel, the Dedicated

Channel +5C-, which is used in both downlink and

uplink. The 5C is set'up !or a oice call o! data

session, and characteri6ed by the possibility o! !ast rate

change and !ast power control.

• The Broadcast channel +BC- is a downlink transport channel

that is used to broadcast syste# and cell speci!ic in!or#ation,

in Syste# in!or#ation blocks. The BC is always trans#itted

oer the entire cell +to both actie and idle UEs- with alow!i$ed bit rate.

• The Forard !ccess Channel +%AC- is a downlink 

transport channel that carries control in!or#ation to UEs when

a rando# access #essage has been sent by the UE to the base

station. 2t7s counterpart, the "andom !ccess channel

+RAC- is used in the uplink to send in the rando# access

#essage !ro# the UE.

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• The High #$eed Donlin% #hared Channel +S'5SC- is a

co##on transport channel shared by all the S5A users

in the cell. 2t is #apped onto up to (8 physical

channels, depending on the nu#ber o! codes aailable !o

PHYSICAL CHANNELS 

Transport channels are !urther #apped onto physical channels,which are de!ined by channelisation codes, and the Radio

%re9uency at which they are broadcast.

Common Do$nlin- Ph)sical Channels.

2n this section we take a brie! look at the !unction o! the co##on

downlink physical channels, which are trans#itted to all UEs.

• The Primar& Common Control Ph&sical Channel +'

CCC-* Broadcasts syste# in!or#ation. TheBroadcast

channel is the transport channel that #aps onto this physical

channel.

• #&nchroni'ation Channel +SC- carries the pri#ary

and secondary Synchroni6ation Codes, which are used !or 

slot synchroni6ation, !ra#e synchroni6ation and the detectiono! the scra#bling code group +one out o! :&-. 2t is ti#e

#ultiple$ed

+only !irst (0;- with the 'CCC +re#aining )0; o! 

ti#eslot-.

• #econdar& Common Control Ph&sical Channel +S'CCC-*

This channel is #apped to by both the aging Channel +C-and the %orward Access Channel +%AC-. Trans#its idle'#ode signaling and control in!or#ation to UE. Can also

 be used !or sending short in!re9uent data.

• Common Pilot Channel +C2C-* Sends the scra#bling codeo! the cell. roides coherent phase re!erence !or 5< channels

and aids channel esti#ation +handoer and cell selection-. 2t is

 

Common Uplin- Ph)sical Channels.

Ph&sical "andom !ccess Channel +RAC-* This channel isused to carry access re9uests= control in!or#ation and short data

 bursts. 2t uses only >pen'loop power control and contains there!ore

no pilot or TC bits.

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