procedures in basic call

8/12/2019 Procedures in Basic Call

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Procedures in Basic Call

The procedures of the Basic Call are described in the following sections :

Paging procedure

Channel required procedure

Channel reservation procedure

Channel activation procedure

Immediate assignment procedure

SCCP connection establishment procedure

Transmission of transparent L3 messages procedure

Ciphering procedure

ssignment procedure

Channel release procedure

S!stem information broadcasting procedure
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Paging procedure

The paging procedure offers the networ" the means to start the establishment of a mobileterminating call with a given #S$

The BSC is able to handle all cell identifier t!pes within the PAGINGmessage$

The BSC requires parameters for calculating the paging group$

The paging procedure is presented in the following figures$

Figure: Paging procedure when paging comes from MSC

Figure: Paging procedure when paging comes from SGSN

In networ"s with %P&Scapabilit!' the PAGINGmessage can also be routed through theS%S($%P&S)related paging is used when paging an #S for a Circuit Switched or aPac"et Switched call on a paging subchannel$ The paging subgroup is calculated b! the

BTS$ *hen the BSC receives paging from the S%S(' the BSC sends a CS-PAGINGCOMMANDor a PS-PAGING COMMAND+for pac"et data, to the BTS$ -or moreinformation' see +.,%P&S in BSC$

If the BTS does not support %P&S' the BSC sends a PAGING COMMANDto the BTS$The BTS builds paging request messages and sends them on the radio path$

If the #S does not answer within a given time limit' the #SC repeats the PAGING

COMMANDmessage$

PAGINGmessage

If the BSC receives the PAGINGmessage from the #SC +a,' the PAGINGmessageincludes the following data:

message t!pe

#S identit! I. +I#SI,
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The CCC4has two alternative configurations that are described below$ The CCC4configuration affects the value of the paging groupinformation element that is included in

the PAGING COMMANDmessage$ The ma5imum value of the paging groupelement is6/$

i BCC47 CCC4 in a 8/)frame multiframe 9 CCC4 bloc"

iiBCC4 7 CCC4 7 S2CC4 +stand)alone dedicated control channel, in a 8/)frame multiframe 3 CCC4 bloc"

Paging %p; ++I#SI mod /


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CS-PAGING COMMANDmessage

The CS-PAGING COMMANDmessage includes the following data:

message header

#S identit!

2& parameter +optional,

temporar! #S identit! +optional,

channel needed +optional,$

#S identit! I. +I#SI, is a mandator! element$ The 2& parameter and the temporar! #Sidentit! +T#SI, elements are optional$ The channel neededelement is also optional: itsinclusion depends on the #SC$ If the channel neededelement is not present' its value isassumed to be


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Figure: CHANNEL REQUESTmessage& onl' one octet long

The establisment causeinformation field indicates the reason for requesting theestablishment of a connection$ This field has a variable length +from 3 bits up to bits,$ Therandom referenceis an unformatted field with variable length +from 8 bits down to 0 bits,$The establisment causeinformation field length is 3 when the #S is %S# phase / level orwhen the #S is %S# phase 0 level and the (.CI +(ew establishment causes support,parameter is set to A--$

The following establishment causes are supported +the random referencefield is mar"edwith (s,:

Figure: N)C* parameter is set to #FF


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Figure: N)C* parameter is set to #N

The networ" uses the random reference and the #S access slot number to identif! and toaddress the #S$

The #S starts the %S# timer T3/0< and waits for its access acceptance' which is anIMMEDIATE ASSIGNMENTmessage on the%C4$

If the #S access is not granted within the time limit defined b! T3/0


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message t!pe: channel required

channel number: uplin" CCC4+&C4,

request reference: establishment cause' random reference received in the access

request and the frame number on which it was received

access dela!: dela! of the access burst as measured b! the BTS$

Channel reservation procedure

fter receiving the CHANNEL REQUIREDmessage from the BTS or the ASSIGNMENTREQUESTmessage from the #SC' the BSC starts searching for a relevant channel:

fter receiving theCHANNEL REQUIRED

message' the BSC starts to search

for a dedicated channel$ If a channel is available in the cell where the originalaccess came from' the BSC reserves it and starts the immediate assignmentprocedure$ In a normal instance of a Basic Call the target channel is the S2CC4$

fter receiving the ASSIGNMENT REQUESTmessage from the #SC' the BSCstarts to search for a TC4 channel$ If one is available in the cell comprising theS2CC4 connection' the BSC reserves it and starts the assignment procedure$ Ifno TC4 channels are available' the TC4 channel request is queued and whenan! one of the TC4 channels in this cell is released' the BSC reserves it for theassignment procedure$

The BSC can allocateS2CC4or TC4channels as follows$ The number of the TC4 andS2CC4 channels depends on the radio configuration$

S2CC4' TC4D-or TC4D4channel in case of a CHANNEL REQUIREDmessage$ -or more information' see 4alf &ate in BSC$

TC4D- or TC4D4 channel in case of an ASSIGNMENT REQUESTmessage$

S2CC4' TC4D- or TC4D4 channel in case of a handover$

Ep to four TC4D- channels in case of a high speed circuit switched data call$ -or

more information' see4SCS2 and /$ "bitDs 2ata Services in BSC$

Channel activation procedure

fter a successful reservation of a new S2CC4 channel' the BSC activates it b! sending the

CHANNEL ACTIVATIONmessage to the BTS$ The %S# timer T9/


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The channel activation procedure is presented in the following figure$

Figure: Channel acti$ation procedure

CHANNEL ACTIVATIONmessage

The BSC sends the CHANNEL ACTIVATIONmessage to the BTS in order to activate thenew S2CC4 channel$

The CHANNEL ACTIVATIONmessage includes the following data:

message discriminator: dedicated channel management

message t!pe: channel activation

channel number

activation t!pe

channel mode: 2T control and channel t!pe

BS power: ma5imum BS power level authorised in the cell +optional,

#S power: ma5imum #S power level authorised in the cell +optional,

timing advance to be used b! #S in subsequent communications +optional,

SCC4 information +optional,$

The SCC4 information is used in dual band cell or when I#SI Based 4andover is enabledin the BSC$ The other optional elements are alwa!s present$ -or more information' see 2ualBand (etwor" Aperationor I#SI)Based 4andover$

CHANNEL ACTIVATION ACKmessage

The BTS ac"nowledges a successful channel activation with the CHANNEL ACTIVATION

ACKmessage$ The BTS starts the transmission and reception on the associated SCC4using the power levels and the timing advance received in the CHANNEL ACTIVATIONmessage$

The BTS ac"nowledges a failure with the CHANNEL ACTIVATION NACKmessage$ Thepossible causes for a failure are listed below:

radio resource not available

radio channel alread! activatedDallocated
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protocol error and subclause' such as mandator! information error

A F # intervention in cases when the channel cannot be used for A F # reasons

ciphering algorithm not supported

equipment failure

service or option not available

not implemented unspecified

mandator! I. error

general I. error$

-or more information' see )+S ,-- ./0 1igital cellular telecommunications s'stem2Phase 345 Base Station Controller 6 Base +ranscei$er Station 2BSC 6 B+S4 interface7a'er , specification8

Immediate assignment procedure

The IMMEDIATE ASSIGNmessage facilitates the assignment of the #S onto an S2CC4channel$ Correspondingl!' the IMMEDIATE ASSIGN REJECTmessage facilitates therefusal of the access: if the S2CC4 channel reservation or activation fails' the BSC sends

the IMMEDIATE ASSIGN REJECTmessage to the #S$ The %S# timer T3/


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message t!pe

channel number

immediate assign information$

The immediate assign information contains the complete IMMEDIATE ASSIGNmessage:

pseudo length

message header

page mode: normal paging

channel description of the allocated S2CC4' the associatedSCC4and hopping

frequenc!

request reference as sent b! the #S in the channel request

initial timing advance

mobile allocation' if frequenc! hopping is used

rest octet$

IMMEDIATE ASSIGNmessage& S"BM& 9" frame

fter receiving the IMMEDIATE ASSIGNmessage' the #S tunes to the assigned S2CC4

and starts to establish the signalling lin" across the networ"$ The #S sends the la!er 0SB#to the BTS on the S2CC4$ The SB# +c, contains a la!er 3 service requestmessage$ The #S specifies the required service t!pe to the networ" with the service requestmessage$

The service request message includes one of the following:

/$ CM SERVICE REQUEST) for mobile originated calls and mobile originatedS#Ss) contains:

o header

o C# service t!pe: #A callDS#SDSSD emergenc! call

o ciphering "e! sequence number

o #S classmar" 0

o mobile identit!$

0$ LOCATION UPDATING REQUEST

3$ IMSI DETACH

$ PAGING RESPONSE) for mobile terminated calls and mobile terminated S#Ss

) contains:
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If the BTS is for some reason unable to send the IMMEDIATE ASSIGNMENTmessage tothe #S' the BTS sends the DELETE INDICATIONmessage to the BSC$ The DELETE

INDICATIONmessage includes the following fields:

message t!pe

channel number

full immediate assign information$

fter receiving the DELETE INDICATIONmessage' the BSC releases the dedicatedradio channel b! sending the RF CHANNEL RELEASEmessage to the BTS$

If the ESTABLISH INDICATIONmessage received during call setup is either empt! orcorrupted' the call attempt will be cleared and all resources released$

SCCP connection establishment procedure

The BSC starts to initiate theSCCPconnection for the #S after receiving the ESTABLISH

INDICATIONmessage for the S2CC4 establishment from the BTS$ The %S# timerT9/


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Figure: +ransmission of transparent 7, messages

+ransmission of transparent 7, messages from MSC to MS

The #SC sends the DATA FORM 1 (DT1)message +a, to the BSC$ This messagecontains the complete la!er 3 information message to be sent to the #S$ If the transparentbit equals one' the BSC forwards the complete la!er 3 information message to the BTSinside the DATA REQUESTmessage +b,$ -or more information' see )+S ,-- .;/)uropean digital cellular telecommunications s'stem 2Phase 345 Signalling transportmechanism specification for the Base Station S'stem 6 Mobile6ser$ices SwitchingCentre 2BSS 6 MSC4 interface8The BTS forwards the L3 information to the #S in a relevantmessage +c,$

+ransmission of transparent 7, messages from MS to MSC

The #S sends the L3 information message +d, to the BTS$ The BTS forwards the L3

information inside the DATA INDICATION+e, message to the BSC$ If the transparent bitequals one' the BSC forwards the L3message to the #SC inside the DT1message +f,$ -ormore information' see )+S ,-- .;/ )uropean digital cellular telecommunicationss'stem 2Phase 345 Signalling transport mechanism specification for the Base StationS'stem 6 Mobile6ser$ices Switching Centre 2BSS 6 MSC4 interface8

Ciphering procedure

Ciphering is one of the securit! procedures designed to protect the subscriber identit! anddata$ It is an optional procedure in %S#$ *hen ciphering is active' all information e5changed

between the mobile and the networ" on the dedicated radio channels is encr!pted$ The "e!previousl! set between the networ" and the #S is used to encipher and to decipher theencr!pted information$

The authentication procedure chec"s the #S identit! in order to prevent unauthorised use$2uring the procedure the ciphering "e! >cis set between the networ" and the #S$ Cipheringis initiated after the ciphering "e! is set on the dedicated signalling channel +S2CC4or-CC4,$

The %S# uses stream ciphering' which means that the data flow transmitted on theS2CC4DTC4is the binar! bit b! bit addition of the user data flow to a ciphering bit stream$-or more information' see )+S ,-- .,< 1igital cellular telecommunications s'stem2Phase 345 Securit' related networ= functions8
http://172.17.40.81:43231/NED/NED?action=retrieve&library=s11_5_140205&identifier=general_glossary&edition=12&language=en&coverage=global&encoding=xhtml_1_0&component=data&item=data&pointer=id011282#id011282http://172.17.40.81:43231/NED/NED?action=retrieve&library=s11_5_140205&identifier=general_glossary&edition=12&language=en&coverage=global&encoding=xhtml_1_0&component=data&item=data&pointer=id011282#id011282http://172.17.40.81:43231/NED/NED?action=retrieve&library=s11_5_140205&identifier=general_glossary&edition=12&language=en&coverage=global&encoding=xhtml_1_0&component=data&item=data&pointer=id011274#id011274http://172.17.40.81:43231/NED/NED?action=retrieve&library=s11_5_140205&identifier=general_glossary&edition=12&language=en&coverage=global&encoding=xhtml_1_0&component=data&item=data&pointer=id011221#id011221http://172.17.40.81:43231/NED/NED?action=retrieve&library=s11_5_140205&identifier=general_glossary&edition=12&language=en&coverage=global&encoding=xhtml_1_0&component=data&item=data&pointer=id04070#id04070http://172.17.40.81:43231/NED/NED?action=retrieve&library=s11_5_140205&identifier=general_glossary&edition=12&language=en&coverage=global&encoding=xhtml_1_0&component=data&item=data&pointer=id04070#id04070http://172.17.40.81:43231/NED/NED?action=retrieve&library=s11_5_140205&identifier=general_glossary&edition=12&language=en&coverage=global&encoding=xhtml_1_0&component=data&item=data&pointer=id011282#id011282http://172.17.40.81:43231/NED/NED?action=retrieve&library=s11_5_140205&identifier=general_glossary&edition=12&language=en&coverage=global&encoding=xhtml_1_0&component=data&item=data&pointer=id011274#id011274http://172.17.40.81:43231/NED/NED?action=retrieve&library=s11_5_140205&identifier=general_glossary&edition=12&language=en&coverage=global&encoding=xhtml_1_0&component=data&item=data&pointer=id011221#id011221http://172.17.40.81:43231/NED/NED?action=retrieve&library=s11_5_140205&identifier=general_glossary&edition=12&language=en&coverage=global&encoding=xhtml_1_0&component=data&item=data&pointer=id04070#id04070


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In an #SC)controlled handover' the #SC tells the new BSS whether encr!ption is required in

the HANDOVER REQUEST.

In a BSC)controlled handover' the BSC passes the encr!ption information to the target BTSon the activation of the channels if the encr!ption information was received from the #SC$

The ciphering procedure is presented in the following figure:

Figure: Ciphering procedure

CIPHER MODE COMMANDmessage

The #SC sends the CIPHER MODE COMMANDmessage +a, to the BSC to indicatewhether ciphering is required and if so' to indicate the ciphering "e!$

The CIPHER MODE COMMANDmessage +from the #SC to the BSC, contains thefollowing data:

message t!pe

la!er 3 header information

encr!ption information: permitted algorithms and ciphering "e!

cipher response mode$

The message contains the encr!ption instruction and the L3 header information for the #S$

*hen ciphering is required' the encr!ption information element contains information for theBTS to load the encr!ption device with the appropriate "e!$

ENCRYPTION COMMANDmessage

An receiving the CIPHER MODE COMMANDmessage' the BSC selects the algorithm tobe used according to the list of permitted algorithms included in the message and thealgorithms that are supported b! that particular BSS$ See Support for different cipheringalgorithmsfor details$
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&egardless of whether ciphering is to be activated' the BSC stores the encr!ptioninformation' including the selected algorithm for possible subsequent handovers' and passes

the encr!ption information to the BTS in the ENCRPTION COMMANDmessage +b,$

The ENCRPTION COMMANDmessage contains the following data:

message header

encr!ption information: selected algorithm and ciphering "e!

lin" identifier

L3 ciphering mode command to #S

message header

cipher mode setting: no cipheringDstart ciphering

cipher response: the cipher response element is used if received from the #SC

+optional,$

The BTS anal!ses the ENCRPTION COMMAND$ If encr!ption is required' the BTSactivates the demodulator to decipher$ &egardless of whether ciphering is required' the BTSsends the CIPHER MODE COMMANDmessage +c, to the #S$

CIPHER MODE COMPLETEmessage

The #S starts to decipher and to encipher using its available ciphering "e!$ It then returns tothe BTS' in encr!pted form' the CIPHER MODE COMPLETEmessage +d, or the ne5t

message it is due to send$ The message includes theI#.I'if required b! the #SC$

An receiving the CIPHER MODE COMPLETEmessage +or an! correctl! enciphered la!er0 frame,' the BTS starts enciphering and forwards the message via the BSC to the #SC +f,$-or more information' see *6)+S ,-- -336 )uropean digital cellular telecommunicationss'stem 2Phase 45 Mobile radio interface la'er , specification8

If the ciphering procedure fails' the #SC ta"es the appropriate action$

Support for different ciphering algorithms

The #SC ma! send a list of permitted ciphering algorithms to the BSC in the CIPHER

MODE COMMANDmessage$ The BSC selects the algorithm to be used from this listaccording to those algorithms that are supported b! the BSS$ If the BSS can support severalalgorithms' the BSC ma"es the selection according to the following preference:

/$ 8D/0$ 8D0

3$ 8D< +no ciphering,$

lgorithms other than those mentioned above cannot be used$

If the BSS cannot support an! of the permitted algorithms' the BSC sends the CIPHER

MODE REJECTmessage to the #SC$ The #SC then decides on further action$
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Assignment procedure

The assignment procedure is used to assign the #S to the correct TC4channel$ Theselection of the TC4 channel is based on the information received from the #SC$

The assignment procedure is presented in the following figure:

Figure: "ssignment procedure

ASSIGNMENT REQUESTmessage

The #SC sends an ASSIGNMENT REQUEST+a, message to the BSC for the assignmentof channels on the interface and the radio interface$ The #SC also runs a supervisor!timer for the assignment procedure$

The BSS responds b! sending the #SC the ASSIGNMENT COMPLETE' ASSIGNMENT

FAILUREor the QUEUEING INDICATIONmessage$ If the #SC fails to receive an! ofthe messages within the time limit defined b! the timer' it clears the call with a CLEAR
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COMMANDmessage$ The BSS releases the #S connection with the channel releaseprocedure$

The BSC e5pects to receive the following fields in the ASSIGNMENT REQUESTmessage:

channel t!pe: radio channel required for the call t!pe

L3 header info

priorit! +optional,

circuit identification code +CIC, indicating the channel to be used on the

interface

downlin" 2T flag +optional,

radio channel identit! +optional,

interference band to be used +optional,$

The #SC uses the priorit! element to define whether the request is allowed to be queuedand' if so' to define the queueing priorit! level$ If the priorit! element is not present' it isassumed that the request can be queued if it cannot be served immediatel!$ -urthermore' ifthe priorit! is not indicated' the message is queued according to the priorit! associated withthe request t!pe' which is defined internall! within the BSS$ If the request is queued' aQUEUEING INDICATIONmessage is returned to the #SC$

The downlin" 2T flag is also optional: it is present onl! when the #SC controls the downlin"2T in a speech call$

If the BSC identifies an! of the following situations on anal!sing the ASSIGNMENTREQUESTmessage' it reects the request b! sending the ASSIGNMENT FAILUREmessage to the #SC' without ta"ing an! action towards the BTS:

/$ If the BSC is not able to use the channel indicated in the CIC' due to its beingin use for another call' the BSC reects the request with the cause re%uestedterrestrial circuit alread' allocated8

0$ If the BSC is not able to use the channel indicated in the CIC' due to its beingmar"ed as undefined' the BSC reects the request with the cause re%uestedterrestrial resource una$ailable8

3$ If the CIC is bloc"ed' the BSC reects the request with the cause re%uested

terrestrial resource una$ailableand sends a BLOCKmessage to the #SC$ -or

reasons when a circuit is bloc"ed b! the BSC' see )+S ,-- ./- 1igital cellulartelecommunications s'stem 2Phase 345 Mobile6ser$ices Switching Centre 6Base Station S'stem 2MSC 6 BSS4 interface 7a'er , specification8

$ If there is no circuit pool on the interface that is able to support the requestedTC4 t!pe' the BSC reects the request with the cause re%uestedtranscoding>rate adaption not a$ailable8

8$ If there is a circuit pool on the interface that is able to support the requestedTC4 t!pe' but the pool implied b! the CIC is totall! contradictor! with the requiredTC4 t!pe' the BSC reects the request with the cause circuit pool mismatch8

$ If the circuit pool implied b! the CIC is at least partiall! compliant with therequested TC4 t!pe' change of the circuit pool ma! be required$ &easons for thechange include the actual traffic channel resource situation of the cell and the
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attempt to allocate the resources in the most optimal wa!$ In this case the BSCreects the request with the cause switch circuit pool8

?$ If the requested speech coder versions are not supported' the BSC reects therequest with the cause re%uested speech $ersion una$ailable8

6$ If the radio interface data rate requirement is totall! contradictor! with therequested TC4 channel rate' the BSC reects the request with the cause in$alidmessage contents8

An receiving the ASSIGNMENT FAILUREmessage' the #SC can either issue a CLEARCOMMANDor retr!$

If the #SC receives the ASSIGNMENT FAILUREmessage with a cause indicating a CICproblem' the #SC ma! send another ASSIGNMENT REQUESTfor the same call using adifferent circuit$

+C! assignment procedure in the BSS

fter the ASSIGNMENT REQUEST' the BSC proceeds to perform the TC4assignmentprocedure$

The BSC sends the PHSICAL CONTE!T REQUESTmessage +b, to the BTS$ In thismessage it requests for the timing advanceof mobile transmission$ The S2CC4 sends thetiming advance via the TC4 and the BTS to the #S' which requires it when moving onto anew radio channel$

If the BSC fails to receive the PHSICAL CONTE!T CONFIRMmessage +c, within thetime limit defined b! the %S# timer T9/


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channel mode: 2T indication and channel t!pe$ The channel t!pe is either a

speech or data channel$ If it is a speech channel' the speech encoding algorithmis includedG if it is a data channel' the transparent or the non)transparent mode isincluded$ The data rate is also given$

channel identification +optional,

encr!ption information if received from the #SC +optional,

BS power as received in the PHSICAL CONTE!T CONFIRM+optional,

#S power as received in the PHSICAL CONTE!T CONFIRM+optional,

timing advance as received in the PHSICAL CONTE!T CONFIRM+optional,

SCC4 information +optional,

multirate configuration +optional,$

Channel identification information is included onl! when activating TC4 channel under 2-CT&$ -or more information' see 2!namic -requenc! and Channel llocation in BSC$

The SCC4 information is used in dual band cell or when I#SI Based 4andover is enabledin the BSC$ -or more information' see 2ual Band (etwor" Aperation'I#SI)Based 4andoverand2!namic -requenc! and Channel llocation in BSC$The multirate configuration elementis present in calls using multirate speech codec$ -or more information' see .nhancedSpeech Codecs: #& and .-&$Ather optional elements are alwa!s present$

The BTS returns the CHANNEL ACTIVATION NACKmessage in the followingsituations$ The BSC indicates the failure to the #SC b! sending the ASSIGNMENTFAILUREmessage with the relevant assignment failure cause value' which can be one ofthe following:

radio interface message failure&due to a message format error

re%uested transcoding>rate adaption not a$ailable&due to the requested

service not being supported

radio resource not a$ailable&due to radio channel problems

radio channel alread' acti$ated5the radio channel is alread! in use

e%uipment failure

ser$ice or option not a$ailable

not implemented unspecified

mandator' *) error

general *) error8
http://172.17.40.81:43231/NED/NED?action=retrieve&library=s11_5_140205&identifier=dfaebxxsxx_ns11&edition=4&language=en&coverage=global&encoding=xhtml_1_0&component=data&item=data&pointer=edfaebxxsxx.ns11-mar2531272820#edfaebxxsxx.ns11-mar2531272820http://172.17.40.81:43231/NED/NED?action=retrieve&library=s11_5_140205&identifier=duaebxxsxx_ns1a&edition=9&language=en&coverage=global&encoding=xhtml_1_0&component=data&item=data&pointer=eduaebxxsxx.ns1a-jan14292931#eduaebxxsxx.ns1a-jan14292931http://172.17.40.81:43231/NED/NED?action=retrieve&library=s11_5_140205&identifier=ibhebxxsxx_ns1a&edition=1&language=en&coverage=global&encoding=xhtml_1_0&component=data&item=data&pointer=eibhebxxsxx.ns1a-oct2241053102#eibhebxxsxx.ns1a-oct2241053102http://172.17.40.81:43231/NED/NED?action=retrieve&library=s11_5_140205&identifier=ibhebxxsxx_ns1a&edition=1&language=en&coverage=global&encoding=xhtml_1_0&component=data&item=data&pointer=eibhebxxsxx.ns1a-oct2241053102#eibhebxxsxx.ns1a-oct2241053102http://172.17.40.81:43231/NED/NED?action=retrieve&library=s11_5_140205&identifier=dfaebxxsxx_ns11&edition=4&language=en&coverage=global&encoding=xhtml_1_0&component=data&item=data&pointer=edfaebxxsxx.ns11-mar2531272820#edfaebxxsxx.ns11-mar2531272820http://172.17.40.81:43231/NED/NED?action=retrieve&library=s11_5_140205&identifier=dfaebxxsxx_ns11&edition=4&language=en&coverage=global&encoding=xhtml_1_0&component=data&item=data&pointer=edfaebxxsxx.ns11-mar2531272820#edfaebxxsxx.ns11-mar2531272820http://172.17.40.81:43231/NED/NED?action=retrieve&library=s11_5_140205&identifier=efrebxxsxx_ns11&edition=10&language=en&coverage=global&encoding=xhtml_1_0&component=data&item=data&pointer=eefrebxxsxx.ns11-sep1311212299#eefrebxxsxx.ns11-sep1311212299http://172.17.40.81:43231/NED/NED?action=retrieve&library=s11_5_140205&identifier=efrebxxsxx_ns11&edition=10&language=en&coverage=global&encoding=xhtml_1_0&component=data&item=data&pointer=eefrebxxsxx.ns11-sep1311212299#eefrebxxsxx.ns11-sep1311212299http://172.17.40.81:43231/NED/NED?action=retrieve&library=s11_5_140205&identifier=efrebxxsxx_ns11&edition=10&language=en&coverage=global&encoding=xhtml_1_0&component=data&item=data&pointer=eefrebxxsxx.ns11-sep1311212299#eefrebxxsxx.ns11-sep1311212299http://172.17.40.81:43231/NED/NED?action=retrieve&library=s11_5_140205&identifier=dfaebxxsxx_ns11&edition=4&language=en&coverage=global&encoding=xhtml_1_0&component=data&item=data&pointer=edfaebxxsxx.ns11-mar2531272820#edfaebxxsxx.ns11-mar2531272820http://172.17.40.81:43231/NED/NED?action=retrieve&library=s11_5_140205&identifier=duaebxxsxx_ns1a&edition=9&language=en&coverage=global&encoding=xhtml_1_0&component=data&item=data&pointer=eduaebxxsxx.ns1a-jan14292931#eduaebxxsxx.ns1a-jan14292931http://172.17.40.81:43231/NED/NED?action=retrieve&library=s11_5_140205&identifier=ibhebxxsxx_ns1a&edition=1&language=en&coverage=global&encoding=xhtml_1_0&component=data&item=data&pointer=eibhebxxsxx.ns1a-oct2241053102#eibhebxxsxx.ns1a-oct2241053102http://172.17.40.81:43231/NED/NED?action=retrieve&library=s11_5_140205&identifier=dfaebxxsxx_ns11&edition=4&language=en&coverage=global&encoding=xhtml_1_0&component=data&item=data&pointer=edfaebxxsxx.ns11-mar2531272820#edfaebxxsxx.ns11-mar2531272820http://172.17.40.81:43231/NED/NED?action=retrieve&library=s11_5_140205&identifier=efrebxxsxx_ns11&edition=10&language=en&coverage=global&encoding=xhtml_1_0&component=data&item=data&pointer=eefrebxxsxx.ns11-sep1311212299#eefrebxxsxx.ns11-sep1311212299http://172.17.40.81:43231/NED/NED?action=retrieve&library=s11_5_140205&identifier=efrebxxsxx_ns11&edition=10&language=en&coverage=global&encoding=xhtml_1_0&component=data&item=data&pointer=eefrebxxsxx.ns11-sep1311212299#eefrebxxsxx.ns11-sep1311212299


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-or more details' see )+S ,-- ./0 1igital cellular telecommunications s'stem 2Phase345 Base Station Controller 6 Base +ranscei$er Station 2BSC 6 B+S4 interface 7a'er ,specification8

If no response is received from the BTS within the time limit defined b! the %S# timer

T9/


22/26

Failure CasesNote

If the BSC receives a HANDOVER COMMANDmessage from the #SC between the ASSIGNMENT

REQUESTand theASSIGNMENT COMPLETEmessage' it ignores the HANDOVERCOMMANDmessage$

The #S returns to its S2CC4 and sends the ASSIGNMENT FAILUREmessage to theBSC if it fails to:

receive the TC4 ASSIGNMENT COMMAND

move to the TC4

receive the E frame from the BTS when it is on the TC4$

The BSC sets the cause radio interface failure& re$ersion to old channel8An receivingthis failure cause' the BSC sends the #SC the ASSIGNMENT FAILUREmessage overthe interface with the same cause$ The #SC clears the connection or retries$

If the time limit defined b! the %S# timer T3/


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Figure: Channel release procedure

The #SC initiates the channel release procedure b! sending the CLEAR COMMAND

message +a, to the BSC$ An receiving the CLEAR COMMANDmessage the BSC releasesthe interface speech circuit and sends the CLEAR COMPLETEmessage +b, to the #SC$The #SC releases the SCCPconnection$

fter the release' the BSC sends a CHANNEL RELEASEmessage +c' d, with an && causevalue Normal Releaseto the #S and a DEACTIVATE SACCHmessage +e, to the BTS$The BSC also starts the %S# timer T3/


24/26

Channel release started b' the BSC

The channel release procedure started b! the BSC is presented in the following figure$

Figure: Channel release started b' the BSC

If there is a BSS failure' for e5ample' the BSC has received the CONNECTION FAILURE

message +a, from the BTS' the BSC sends the CLEAR REQUESTmessage +b, to the #SCand starts the %S# timer T9/


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System information broadcasting procedure

The networ" broadcasts regularl! the messages SSTEM INFORMATION TPE 1to #

and optionall! TPE $%&'on theBCC4$

Figure: Sending of BCC! information

The #S uses this information to decide whether and how it ma! gain access to the s!stemvia the current cell$ The SSTEM INFORMATION TPE $%&'message is sent if thee5tended neighbour cell description is in use$ The TPE $and TPE $%&'messagesindicate that each I. carries onl! a part of the B+BCC4 llocation,$

The networ" sends similar information in messages SSTEM INFORMATION TPE and ' and optionall! in %&'' on the SCC4$The messages are sent directl! after a

handover' and whenever there is no other use of the channel$ The SSTEMINFORMATION TPE %&'message is sent if e5tended neighbour cell description is inuse and the TPE %&'message indicates that each I. carries onl! a part of the B$

Figure: Sending of S"CC! Filling

The information broadcast can be grouped in the following classes:

information giving unique identification of the current networ"' location area and

cell

information used for cell selection and candidate cell measurements for handover

procedures
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information describing the current control channel structure

information controlling the random access channel utilisation

information defining different options supported within the cell$

Purpose of C3 cell reselection

The purpose of C0 cell reselection is to control the cell reselection of #Ss in idle status$ TheC0 cell reselection allows the operator to define other criteria for reselection in addition to thepower level$ The operator can define different reselection criteria for different "inds of cells'such as macro and micro cells$

The C0 reselection criteria also includes the so called penalt! time' which allows the cellreselection to happen more slowl! than the pure C/ criteria evaluated b! the #S$ Thisenables avoiding undesirable reselection of a micro cell in an environment where there iscoverage b! a micro cell and a macro cell$

Broadcasting C3 reselection parameters

The C0 reselection information is broadcasted to the #Ss in S!stem Information 3 and frames$ The parameters are included in SI rest octets information element when the C0reselection function is used$ The BSC sends the S!stem Information frames to the BTS onthe bis interfaces and the BTS sends them on the air$ The #S evaluates the C0 reselectioncriteria according to the given parameters$ -or more information' see .TS 3

procedures in basic call

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