3G call setup.doc

8/11/2019 3G call setup.doc

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3G/UMTS Complete Mobile Originated

Circuit Switched Call SetupZahid Ghadialy

A Complete Mobile Originated Circuit Switched Call Setup is shown in the MSC below


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1. Sytem !n"ormation #$CC%&

The UE reads the System Information that is broadcast on BCC! The information is not read

continuously! It is only read if the information changes

'. ((C) ((C Connection (e*uet #CCC%&The Mobile user decides to initiate a "oice call! The first message the UE will send on CCC is

##C Connection #e$uest! This will contain among other things% Initial UE Identity andEstablishment Cause

3. +$,-) (adio in Setup (e*uet

The S#&C sends this message to &ode B! It will pass the Cell Id% T'S% T'CS% fre$uency% U(Scrambling code% etc to &ode B!

0. +$,-) (adio in Setup (epone

&ode B allocates the resources and starts )* #eception! +hile transmitting the response it

includes the Transport layer addressing information that includes the Binding Identity of the

AA(, for Iub data transport bearer

. ,C,-) 2tablih (2

The AA(, binding identity -Iub .ata Transport Bearer Id/ is passed to A(CA) protocol in &ode

B! The Iub .ata Transport bearer is now bounf to .C!

4. ,C,-) 2tablih C+5

Establish confirm from A(CA) in &ode B

6) 7C%85-) 7ownlin Synchroniation

The &ode B and S#&C establishes synchronisation for the Iub .ata Transport bearer by means

of e0change of the appropriate .C 'rame )rotocol frames!9) 7C%85-) Uplin Synchroniation

Once the U( synchronisation is achei"ed% &ode B starts .( transmission!

:) ((C) ((C Connection Setup #CCC%&

##C Connection Setup message is sent on CCC with the parameters re$uired to establish.C! Also the state indicator will be set to .C for the "oice -or CS/ call!

1;) +$,-) (adio in (etore !ndication

Once the UE establishes #adio (in1% &ode B will send #( #estore indication to the S#&C!

11) ((C) ((C Connection Setup Complete #7CC%&

##C Connection Setup complete will be sent on .CC! Integrity and Ciphering related

paarmeters and UE capability information will be sent bac1 to S#&C

1') ((C) !nitial 7irect Tran"er

'irst &AS message is now sent by the UE! It indicates that a UE orginated 2oice call is re$uired!

The UE identity -TMSI/ will also be passed in this message

13) (,+,-) !nitial U2 Meage


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The &AS message will be forwarded to appropriate C& .omain -CS .omain in this case/!

Along with the CM ser"ice re$uest% it will also include (AI and SAI!

10) (,+,-) 7irect Tran"er

MSC32(# needs to perform authentication to ma1e sure that the UE is genuine! 'or this reason

it will challenge the UE with a Authentication to1en and #A&. -random number/1) ((C) 7ownlin 7irect Tran"er

S#&C transfers the &AS message to the UE

14) ((C) Uplin 7irect Tran"er

UE computes the response -#ES/ and sends it bac1 in the &AS message


S#&C relays the response to the MSC32(#! The MSC32(# will compare the response #ESwith the e0pected response 4#ES! If they are the same then the procedure will continue!

19) (,+,-) Security Mode Command

MSC32(# sends the Security Mode Command to start Ciphering and Integrity )rotection!Ciphering is optional while Integrity )rotection is mandatory! The Algorithms% etc are 1nown to

the MSC32(# and the UE and only the ones that are common between them are used!

1:) ((C) Security Mode Command

##C 'orwards the Security Mode command recei"ed from MSC32(# to the UE!

';) ((C) Security Mode Complete

The UE configures the Ciphering and Integity )rotection and responds bac1 to the networ1! The

response message is Integrity )rotected for further safety! Ciphering is started at Ciphering

acti"ation time! Since this is a Circuit switched call% the Ciphering will be started in MAC! In

case of AM and UM bearers it is started in #(C!

'1) (,+,-) Security Mode COmplete

The networ1 forwards the Security Mode Complete message to MSC32(#!

'') (,+,-) 7irect Tran"er

The networ1 may decide to re5allocate the TMSI to the UE! It sends a .T message which

includes the &AS TMSI #eallocation Command!

'3) ((C) 7 7irect Tran"er

The #&C relays the .T message to the UE!

'0) ((C) U 7irect T(an"er

The UE ta1es the new TMSI and responds with the Complete message

') (,+,-) 7irect Tran"er

The #&C relays the message to the C& domain

'4) ((C) U 7irect T(an"er

The UE now sends the 6Setup6 message in U( .irect Transfer message! This will include all the

re$uired parameters for setting up the "oice call! It will include the number that UE wishes to be


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contacted and the bearer capability

'6) (,+,-) 7irect T(an"er

The networ1 relays the message to the MSC32(#

'9) (,+,-) 7irect T(an"er

The MSC32(# sends Call )roceeding to the UE indicating that it is now starting with the #AB

establishment procedure!

':) ((C) 7 7irect T(an"er

The networ1 relays it to the UE!

3;) (,+,-) (,$ ,ignment (e*uet

The C& initiates establishment of the #adio Access Bearer using the #AB Assignment #e$uest

message! This message includes the 7oS of the call being established% the Transport Address% IuTransport association% etc!

31) ,C,-) 2tablih (2

S#&C initiates the set5up of Iu .ata Transport bearer using A(CA) protocol! The re$uestcontains the AA(, Binding Identity to Bind the Iu .ata Transport Bearer to the #AB! -&ote that

this is not done in case of )S #AB/

3') ,C,-) 2tablih C+5

The C& responds with the A(CA) Establish C&'

33) +$,-) (adio in (econ"iguration -repare

S#&C re$uests &ode B to prepare establishment of .C to carry the #AB! It passes the T'S%

T'CS and )ower Control Informnation in the message!

30) +$,-) (adio in (econ"iguration (eady

&ode B allocates the resources and responds with the #eady message! It sends bac1 the AA(,

address and the AA(, binding Id for the Iub data transport bearer!

3) ,C,-) 2tablih (2

S#&C initiates setup of Iub .ata Transport Bearer using A(CA) protocol! The re$uest containsthe AA(, Binding Identity to bind the Iub .ata Transport Bearer to .C!

34) ,C,-) 2tablih C+5

The &ode B responds with the Establish Confirm!

36) 7C%85-) 7ownlin Synchroniation

The &ode B and S#&C establish synchronism for the Iub .ata Transport Bearer by means ofe0change of the appropriate .C frame protocol frames! S#&C sends the .( Synchronisation

frames!

39) 7C%85-) Uplin Synchroniation

The &ode B responds with the UE Synchronisation frames!

3:) +$,-) (adio in (econ"iguration Complete

'inally the S#&C instructs the &ode B of the C'& at which the new configuration will come


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into effect!

0;) ((C) (adio $earer Setup

S#&C sends the #B Setup message to add the new .C6s! The message will be recei"ed using

the old configuration!

01) ((C) (adio $earer Setup (epone

After the acti"ation time the UE will respond with complete message using the new

configuration!

0') (,+,-) (,$ ,ignment (epone

The S#&C responds with the response to the MSC32(#!

03) !SU-) !nitial ,ddre Meage

MSC32(# sends the Initial Address Message to the )ST&! The message tells the )ST& toreser"e an idle trun1 circuit from originating switch to the destination switch!

00) !SU-) ,ddre Complete Meage

The ACM message is sent to indicate that the remote end of the trun1 circuit has been reser"ed!


The Alert message is sent to the S#&C! This message contains the ACM recei"ed from the)ST&!

04) ((C) 7irect Tran"er

The Alert message is forwarded to the UE! The Alert message will inditiate the ringing tone on

the handset!

06) !SU-) ,nwer Meage

+hen the person that is being called pic1s up his phone% an Answer message is sent to theMSC32(#!


The MSC32(# sends the Connect message to the S#&C "ia .irect Transfer message! The

Connect message indictaes that the End User has answered the call!

0:) ((C) 7 7irect Tran"er

The S#&C forwards the Connect message to the UE!

;) ((C) U 7irect Tran"er

The UE confirms the reception of the Connect message using the Connect Ac1nowledge and

sending it "ia .irect Transfer1) (,+,-) 7irect Tran"er

The &etwor1 forwards the Connect Ac1nowledge to the MSC32(#! The call has now beensuccessfully established!


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'urther #eading8

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3G call setup.doc