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8.23 Direct Transfer8.23.1 GeneralThe purpose of the Direct Transfer procedure is to carry UE CN signalling messages over the Iu Interface. TheUE - CN signalling messages are not interpreted by the UT!N" and their content #e.g. $$ or CC message% is

outside

the scope of this specification #see &'(%. The UE CN signalling messages are transported as a parameter in the

DIECT T!N)*E messages. The procedure uses connection oriented signalling.3GPP

Release 1999 48 3GPP TS 25.413 V3.14.0 (2003-09)

8.23.2 Successful Operation8.23.2.1 CN Originated Direct TransferRNC CNDIRECT TRNS!ERFigure 25: Direc Tra!s"er# $% &rigi!ae'. Success"ul &erai&!.If a UE CN signalling message has to be sent from the CN to the UE" the CN shall send a DIECT T!N)*Emessage to the NC including the UE CN signalling message as aNAS-PDU IE.

If the DIECT T!N)*E message is sent in the do+nlin, direction it shall include the SAPI IE and shall not

include

theLAI RAC IE and the SAI IE. The use of the SAPI IE included in the DIECT T!N)*E message enables theUT!N to provide specific service for the transport of the messages.

8.23.2.2 "TRN Originated Direct TransferRNC CNDIRECT TRNS!ERFigure 2: Direc Tra!s"er# R%$ &rigi!ae'. Success"ul &erai&!.If a UE CN signalling message has to be sent from the NC to the CN +ithout interpretation" the NC shall send

aDIECT T!N)*E message to the CN including the UE CN signalling message as a NAS-PDU IE.

If the DIECT T!N)*E message shall be sent to the ) domain" NC shall also add the LAI and theRAC IEs"

+hich +ere the last /!I !C indicated to the UE by UT!N via the current C connection" or if UT!N had

notyet indicated any /!I !C to the UE via the current C connection" then the /!I !C of the cell via +hich

thecurrent C connection +as established. If the DIECT T!N)*E message is sent to the ) domain" the NC

shallalso add )ervice !rea corresponding to at least one of the cells from +hich the UE is consuming radio resources. If

the

DIECT T!N)*E message is sent in uplin, direction the NC shall not include the SAPI IE.

8.23.3 #nor$al ConditionsIf the DIECT T!N)*E message is sent by the NC to the ) domain" and is missing any of theLAI IE"RAC

IE"

SAI IE" the CN shall continue +ith the Direct Transfer procedure" ignoring the missing IE.If the DIECT T!N)*E message is sent by the CN to the NC +ithout the SAPI IE" the NC shall continue

+ith

the Direct Transfer procedure.

8.2% O&erload Control8.2%.1 GeneralThis procedure is defined to give some degree of signalling flo+ control. !t the UT!N 0rocessor 1verload0 and

01verload in the Capability to )end )ignalling $essages to the UE0 are catered for" and at the CN 0rocessor1verload0 is catered for. The procedure uses connectionless signalling.

The philosophy used is to stem the traffic at source +ith ,no+n effect on the service. The algorithm used is2

!t the CN side2

- If Tig1C is not running and an 13E/1!D message or 0)ignalling oint Congested0 information is received" the

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traffic should be reduced by one step. It is also possible" optionally" to indicate the number of steps to reduce the

traffic +ithin theNumber of Steps IE. !t the same time" timers Tig1C and TinTC should be started.

- During Tig1C all received 13E/1!D messages or 0)ignalling oint Congested0 information should be

ignored.- This step by step reduction of traffic should be continued until ma4imum reduction is obtained by arriving at the

last step.

- If TinTC e4pires #i.e. no 13E/1!D message or 0)ignalling oint Congested0 information is received during

TinTC% the traffic should be increased by one step and TinTC should be started unless normal load has beenresumed.

!t the UT!N side2

- If Tig1 is not running and an 13E/1!D message or 0)ignalling oint Congested0 information is received" the

traffic should be reduced by one step. It is also possible" optionally" to indicate the number of steps to reduce thetraffic +ithin theNumber of Steps IE. !t the same time" timers Tig1 and TinT should be started.

- During Tig1 all received 13E/1!D messages or 0)ignalling oint Congested0 information should be

ignored.

- This step-by-step reduction of traffic should be continued until ma4imum reduction is obtained by arriving at thelast step.

- If TinT e4pires #i.e. no 13E/1!D message or 0)ignalling oint Congested0 information is received during

TinT% the traffic should be increased by one step and TinT should be started unless normal load has been

resumed.

The number of steps and the method of reducing the load are considered to be an implementation specific function.There may be other traffic control mechanisms from 15$ activities occurring simultaneously.

8.2%.3 Successful Operation8.2%.3.1 O&erload at t'e CNRNC CNO(ER)ODFigure 2*: +,erl&a' a e $%. Success"ul &erai&!.The CN should indicate to the NC that it is in a congested state by sending an 13E/1!D message. The CN

Domain

Indicator IE may be included" if the CN can determine the domain suffering the signalling traffic overload.

The UT!N receipt of this message should cause the reduction of signalling traffic to+ards the CN. If CN DomainIndicator IE is indicated +ithin the 13E/1!D message" the NC should apply signalling traffic reduction

mechanisms to the indicated domain.8.2%.3.2 O&erload at t'e "TRNRNC CNO(ER)ODFigure 28: +,erl&a' a e TR/%. Success"ul &erai&!.If the UT!N is not capable to send signalling messages to the UE due to overloaded resources then the UT!N

should send an 13E/1!D message to the CN. The NC shall include the Global RNC-ID IE in this message.