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Signaling Analysis of Typical UTRAN Procedures

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l Revision update record:

p Add the pictures of signaling procedures in the remarks(Page38&43-45&50-

52&59-65).

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l UMTS network is composed of CN,UTRAN and UE.

l For UTRAN network includes RNC and NodeB .

l RNS means Radio Network Subsystem ,which is composed of one RNC and the the

NodeBs under its control.

l The interface between RNC and NodeB is IUB interface. IUR interface may be

configured between two RNC, it is optional, used for inter-RNC cooperation.

l RNC is connected to CS domain through IU-CS interface and connected to PS domain

through IU-PS interface.




l By RRC signaling, RNC controls UE. So the RRC is the most important signaling in

UTRAN. The access success rate , handover success rate are all calculated based on the

RRC signaling statistic. RRC signaling is very useful to analyze the fault.

l IUB interface signaling is called NBAP signaling, which can be used for locating NodeBs

faults.

l By analyze RANAP signaling between RNC and CN, we can locate a fault in CN or in

UTRAN, especially for RAB assignment ,call drop, inter-RAT relocation and paging

procedure, RANAP signaling is very useful.

l By analysis of RNSAP signaling between two RNC, we can trace inter-RNC handover

procedure.

l Most of the procedures are realized by cooperation of several interfaces.




l In idle mode, UE reads system information , so as to control it self. The behaviors in Idle

mode include PLMN selection, cell selection and reselection, paging monitoring;

l When UE needs to perform location update, attach, detach procedures, it will

trigger request for RRC setup , enter connected mode, then finish the signaling

procedure with CN. After that, RNC releases the RRC connection, to let UE go back to

idle mode.

l After UE receives a paging or when user initiates a service, UE will trigger RRC

setup ,in connected mode, UE will then send and receive NAS signaling with CN.

After that , CN may start RAB assignment procedure to set up a bearer for the service.

l During the service ,UTRAN may handover the CELL-DCH UE to neighbor cell based on

the mobility of the UE or based on the load of the cell. CELL-FACH\CELLPCH UE may

trigger cell update procedure after it move to a area covered by a neighbor cell.

l During the PS service period, UTRAN may reconfigure the radio bear of the service

based on the network load or users activity.

l In case of service changing (such as to change a VP service to a AMR service ), RAB

modification procedure is needed.




l The logical structure of system information is like a tree.

l By the index in MIB and SB, UE can read the detail contents in SIB




l By the drive test tool, we can trace the system information, so as to know some basic

information of a cell.

l In default condition, Huawei network adopts following types of system information:

p MIB: master information block

p SB: scheduling block

p SIB: system information block, includes SIB1, SIB2, SIB3, SIB5, SIB7, SIB11.




l MIB: master information block

l PLMN is broadcasted in MIB, that is MCC and MNC of the network, which is used for

UE PLMN selection

l Besides that, MIB includes scheduling information of SB and SIB, that is the index, by

which UE can acquire the location of SB and SIB, so as to read the detail information in

SIB.

PLMN ID

Scheduling information for SB and SIB




l SB: Scheduling block

l SB only tells the scheduling information of SIB, such as the scheduling information of

SIB1/SIB2/SIB3 in this example.

l The scheduling information of other SIB(SIB5, SIB7, SIB11) is in the MIB.

Scheduling information of SIB1






l SIB1:System Information Block1

l DRX means discontinuous reception, used to save the battery of the UE when

monitoring the paging.

l Counters and constants are used to control the procedures of access , cell update ,

DCH setup of the UE, and so on, the meanings of the counters refer to 3GPP 25.331

DRX Coefficient of CS domain

Counters and constants used for UE in connected mode

Counters and constants used for UE in Idle mode




l SIB2 indicates the URA ID of a cell, URA ID is used for mobility management of a UE in

URA-PCH state.




l SIB3:System Information Block 3

l In SIB3,UE can get related parameters for cell selection/reselection

l Try to answer the following questions:

p What is the use of Max allowed UE transmitting power here?

p In the example of this page, what is the RNC ID and cell ID?

p In the example of this page ,check the cell selection parameters and compare it with the default setting, which parameter is changed , and what is the

Intra/inter frequency cell reselection threshold

Available AC of this cell

Inter-RAT cell reselection threshold

Cell selection threshold

Cell reselection time to triggerMax allowed UE transmitting power

RNCID + cell ID




l SIB5:System information Block5

l Question:

PICH/AICH power

PRACH configration

RACH transmission format

Available access resource

Mapping between AC and ASC




l SIB5:System information 5 (Cont.)

l Question:

p What is the use of PCPICH power here?

PCPICH power

AICH SF

Cell HSDPA capability

Cell HSUPA capability

Random access parameters

Configuration of SCCPCH

Configuration of PICH




l SIB7:System information 7

l SIB7 broadcasts UL RTWP to UE .

UL interference

Dynamic persistence level




l SIB11:System information block 11

l SIB11 broadcasts neighbor list of the cell, includes intra-freq/inter-freq/inter-RAT neighbors.

l For WCDMA FDD neighbors , PSC is the most important information.

Intra-freq neighbor list

Scambling code




l SIB11:system information block 11cont.

l For GSM neighbors, it includes BSIC, BCCH information

GSM neighbor list

BCCH

Qoffset for cell reselection

Rx level min

BSIC




l Paging message may be initiated by CN or RNC. Based on UEs state , RNC may send

paging type1 or type2 on Uu interface.

l Page type1 is for the UE in IDLE, CELL-PCH ,URA-PCH state. Paging type1 is sent on

PCCH and DRX is used.

l Page type2 is for the UE in CELL-DCH , CELL-FACH. Paging type2 is sent on DCCH.




l IU Interface paging signaling

l Paging signaling on IU interface include:

p Type of the domain (CS or PS)

p UE IDIMSI is mandatory, but TMSI/PTMSI is optional

p LAC/RAC

p Paging cause

Source of the paging

UE IMSI

UE TMSI

LAC

Paging cause




l After RNC receives a paging from CN, RNC will check the state of the UE. If UE is in idle

mode, CELL-PCH or URA-PCH state, RNC will page the UE with type1 on PCCH.

l If the paging signaling from CN includes IMSI and TMSI (or P-TMSI) both, RNC will page

the UE by TMSI (or P-TMSI).

l If the paging from CN includes IMSI only, RNC will page the UE by IMSI.




l By setting up RRC connection with UTRAN, UE enters connected mode. This procedure

is triggered by UE sending RRC CONNECTION REQUEST on RACH.

l Based on the cause value in RRC CONNECTION REQUEST signaling, RNC decides the

channel type for RRC connection, the channel for RRC connection could be DCH

(DCH3.4k ,DCH6.8k ,DCH13.6k ,DCH27.2k), CCH (RACH/FACH), and even HSPA

channel.

l For RRC Setup on DCH or HSPA, RNC shall configure NodeB to prepare RL , after that,

by RRC CONNECTION SETUP signaling, RNC configures UE

l UE sends RRC CONNECTION SETUP COMPLETE as the response, in this signaling, UE

reports the capability of itself.

An example of RRC setup procedure




l For RRC CONNECTION REQUEST signaling, we should pay attention to the following

elements:

p UE ID

p CauseBased on this cause ,RNC decides the channel for RRC connection.

p Service cell CPICH Ec/Noused for downlink DCH initial power calculation.

p Note: For some new version mobile phones, the UE HSPA capability is include in

this signaling, so as to support RRC setup on HSPA.

UE ID

Cause

Service cell Ec/No




l In RRC CONNECTION SETUP signaling, it includes:

URNTI

State of UE

DRX Cycle

RB information




Transport channel

TTI 10ms

TB size

TB number

Channel coding

l RRC CONNECTION SETUP (Con.)

l The data rate of the channel is

configured in transport

channel: TB Size * TB Number

/ TTI

l The configurations for UL and

DL transport channels are

separate.




Transport channel

TTI 10ms

TB size

TB Number

Channel coding

Target BLER

l RRC CONNECTION SETUP(Con.)

l Configuration of downlink transport channel is similar with uplink,

l Question:

p Why the BLER is configured in downlink only?




Power offset

Uplink code


l Question:

p How the RNC allocates uplink scrambling code ?

p In this case, the uplink SF is 64, can you tell what is the rate of the channel?

Uplink powerControl algorithm




DL OVSF code


l Question: The SF in uplink and downlink are different, are the channel rates different

also?

Downlink powercontrol Mode




Downling DCH OVSF code


l In downlink ,physical RLs are configured separately

l Question

p Why downlink physical RLs are configured separately? How about uplink

configuration?

p Which OVSF code is allocated in this case?

p From the code allocation, can you judge if the HSDPA is active in this cell?

Down PSC




l RRC CONNECTION SETUP COMPLETE:

l By RRC CONNECTION SETUP COMPLETUE gives RNC a response to confirm the setup of RRC connection. In addition, UE reports its capabilities, include

p UE RF capability

p Inter-RAT capability

p Compressed mode and measurement capabilities

p HSPA capabilities.

UEs radio capability




l RRC CONNECTION SETUP COMPLETE(Con.)

l UEs GSM capabilities affect the RNCs decision in Inter-RAT handover.

UEs GSM setting

UEs GSM Class




l RRC CONNECTION SETUP COMPLETE(Con.)

l The measurement capabilites affect the RNCs measurement control.

UEs power level

The 2100M measurement capability

The GSM measurement capability

The extension band measurement capability




l RRC CONNECTION SETUP COMPLETE (Con.)

l The HSPA capability of UE affects the channel type of the traffic, rate negotiation and HSPA scheduling.

l NACC function can shorten the time gap of PS service handover.

L2 capabilities

HSPA capability

NACC capability of UE




l We can check the type of channel from this signaling:

l If we want to setup RRC on HSPA, beside the configuration of the RNC , the UEs HSPA

capability is required also, because UE should report HSPA capability to RNC in

the RRC CONNECTION REQUEST signaling.




l NAS means non access stratum.

l After RRC connection setup, UE transmits Initial UE message to CN to trigger NAS

signaling procedure.

l Via NAS signaling, UE can realize location registration (IMSI ATTACH), GPRS ATTACH,

PDP activation, authentication, security mode, and so on.

l RAB Assignment is after the NAS procedure.

l Most of the NAS signalings are transparent messages in UTRAN, so they are called

directed transfer signalings.




l Initial UE message is transferred to CN by RNC.




l An example of Initial UE Message (RNC to IU)

l In this signaling, UE wants to attach IMSI in CN.

l Question:

p In which scenario, UE triggers this procedure.

Message type

Message content

LAC




l An example of CS imsi detach Message (RNC to IU)




l An example of PS service request Message (RNC to IU)




l An example of CS service request Message (RNC to IU)




l CN sends Common ID to RNC, which is used for paging transmission during the

connection

l Question:

p Why the Common ID is IMSI but not TMSI?




l This signalings are called direct transfer message, because UTRAN does not process

these messages, just repeats to CN in uplink or to UE in downlink.




l An Example of Direct Transfer Message

l Since RNC does not process the DT message , so ,we can analyse the DT message on the IU

interface.

l In this example, CN requests UEs authentication.

Authentication Request




l An Example of Direct Transfer Message (Con.)

Authentication Response




l An example of call setup Message (RNC to IU)




l An example of PDP Context Activation (RNC to IU)




l An example of IMSI Request Message (IU to RNC)




l By RAB Assignment procedure, the service bearer is setup. CS RAB Assignment

procedure is after the call proceeding DT message, while PS RAB Assignment

procedure is after the PDP Context Activation DT message.

l In this example, after UEs PDP Context Activation DT message, CN sends RAB

ASSIGNMENT REQUEST to RNC ,informs the QoS of the service and priority of the UE

to RNC.

l RNC will make a decision based on the required QoS and start the bearer setup

procedure.

l By NBAP , RNC requests NodeB reconfigure RL (Question: Why it is Reconfigure, not

setup), and send the relative configuration to UE by RB Setup signaling.

l UE sends a RB SETUP COMPLETE signaling to RNC as a response.




l CN sends the service and UE related configurations to RNC via RAB ASSIGNMENT REQUEST

signaling.

l In this example, PS CN assigned an interactive RAB, which is symmetric in uplink and downlink, the Maximum bit

rate is 8.64M with out guaranteed bit rate

Service class

Service bandwidth

Data format




l RB SETUP Signaling

l By RB SETUP signaling, RNC send the configuration to UE , this signaling structure is similar with RRC SETUP.

l Questions

p In this example, the PS service is carried on DCH or HSPA?

p If the UE support 5.76M ,is that possible to achieve this rate?

HRNTI and ERNTI of the UE

UL Physical channel

Configuration of UL Transport channel

Configuration of DL Transport channel

DL Physical channel




l As a response to RNC, UE sends RB SETUP COMPLETE signaling to RNC.




l As a response to CN, RNC sends RAB ASSIGNMENT RESPONCE signaling to CN.




l An example of HSDPA+384K Message

p RAB assignment request :




p RB setup :




l An example of VOICE Message





p RB setup request :




l An example of HSDPA+384K Message





p RB setup request :




l Soft handover procedure is triggered by RNC sending MEASUREMENT CONTROL to

UE. By default configuration ,after RRC setup complete , RNC sends MEASUREMENT

CONTROL signaling to UE to trigger intra-frequency measurement . In this

MEASUREMENT CONTROL , RNC configure neighbor list and some thresholds related

to the measurement.

l When the measured signals satisfy some threshold configured in measurement

control, UE triggers a MEASUREMENT REPORT to RNC.

l According to this MEASUREMENT REPORT, RNC may make a decision ,then triggers

the handover.

l In this case, UE triggers a 1A event, then RNC executes a RL addition procedure(soft

handover). After that , UE is in soft handover state.




Measurement ID

PSC of a neighbor

Intra-freq Neighbor list

l A Measurement Control of intra-frequency measurement

l By the Measurement control signalings with the same measurement ID, RNC can

modify the neighbor list of the UE.

l Similar with SIB11, neighbor list in measurement control signaling includes the PSCs

of the neighbors.




filter coefficient for measured results

l A Measurement Control of intra-frequency measurement (Cont.)

l By default configuration, an intra-freq measurement report is triggered

based on Ec/No value. In the triggered report, UE reports both RSCP and

Ec/No of the measured cells.

Measurement Value to trigger event

Reporting value for active set cells

Reporting value for monitored set cells

Reporting value for detected set cells




Parameters for event 1A

l A Measurement Control of intra-frequency measurement (Cont.)

l In 3GPP 25.331, 1a,1b,1c,1d,1e,1f and 1j event are defined for FDD. Huawei

doesnt use event 1e, and by default , 1j is not switched on either.

l UE may trigger the events according to the thresholds configured by RNC.

Reporting mode

Parameters for event 1F

Parameters for event 1B

Parameters for event 1C

Parameters for event 1D




Measurement ID

l Measurement Report

l When some of the measurement targets achieve the configured threshold, UE will then trigger a measurement report.

l For an event triggered report, the event and the PSC who triggers this event are the most important information.

p Based on the event , RNC can then make a handover decision.

p Based on the PSC, RNC can then check the neighbor list, so as to get the cell ID of the PSC.

l In a event triggered report, UE may report the signal of all the measured cells

PSC of the measured cell

Event triggered

Measured Result

Other measurement results

PSC of the cell who triggers the event




MAX UE Tx POWER

l Active set update

l After the admission and preparation, RNC configures the OVSF of the new

RL and PSC of the new cell to UE, based on which, UE can then try to

synchronize with the new RL.

PSC of the new RL cell

OVSF code of the new RL




l As a response, UE sends ACTIVESET UPDATE COMPLETE to RNC to complete this

handover




l In this case, UE takes handover several times, include HSUPA soft handover and HSDPA hard handover.

l HSUPA soft handover is executed by ACTIVESET UPDATE, which does not effect HSDPA service.

l HSDPA handover and HSUPA serving cell change is executed by PHYSICAL CHANNEL RECONFGUREATION , By reading the information elements DL information per RL list", we can know the handover information of HSPA.

l Question : May HSDPA serving cell be different from HSUPA serving cell




l Question : May HSDPA serving cell be different from HSUPA serving cell

p From signaling, we can see the serving cell for HSDPA and HSUPA could be

different. But Huaweis algorithm keeps them identical.




l Compressed mode is the precondition of inter-freq and inter-RAT measurement.

l In compressed mode, RNC send both MEASUREMENT CONTROL for inter-freq and

inter-RAT measurement.

l Based on UEs MEASUREMENT REPORT signaling, RNC makes handover decision

then executes the handover and stop the compressed mode at the same time.




Ec/No Threshold for 2D

Start the compressed mode

l Procedure to start compressed mode

l After RB setup, RNC sends 2D and 2F thresholds to UE.

l When the current carrier meets the threshold, UE reports 2D event.

l RNC reconfigures the RL in NodeB and sends PHYSICAL CHANNEL RECONFIGURATION

signaling to configure the compressed mode.

l Questions

p Is it necessary for the RNC to configure 2D with Ec/No and RSCP separately? What is

the benefit from this?

p How to confirm the 2D report is triggered by Ec/No or RSCP?

p If 2F is trigged during the compressed mode, what will happen then?

2D Measurement report

RSCP Threshold for 2D




l Answers to the Questions

p Is it necessary for the RNC to configure 2D with Ec/No and RSCP separately?

What is the benefit from this?

n Yes , it is necessary, by doing this, the compressed mode can be triggered by bad quality or poor strength of the CPICH both, it is more reliable.

p How to confirm a 2D report is caused by Ec/No or RSCP?

n The measurement ID of the report signaling can indicate this. p If 2F is trigged during the compressed mode, what will happen then?

n Compressed mode will be stopped by RNC in this case.




Measurement quantity

l MEASUREMENT CONTROL signaling to configure 2D\2F Ec/No threshold

l When the measured signal is lower than 2D threshold, or it is higher than 2F

threshold, UE then triggers Measurement Report 2D or 2F to RNC

l 2F report is used to terminate compressed mode. RNC ignores this report in case of

non-compressed mode.

2D parameters

2F parameters




l UE triggers event 2D after the measured signal of current carrier is lower than the

threshold;




Configuration of compressed slots

l PHYSICAL CHANNEL RECONFIGURATION to start the compressed mode

l In compressed mode, some slots are compressed to measure the inter-freq and Inter-

RAT neighbors. For GSM neighbor, measurement value can be RSSI and BSIC, for

WCDMA neighbors, measurement value can be Ec/No and RSCP.

l Compressed mode can be achieved by SF/2 or high layer scheduling. For low rate DCH,

RNC configures SF/2; For high rate DCH, high layer scheduling is used to achieve the

compressed mode.

Measurement value

Compressed mode isachieved by SF/2




l UE respond PHYSICAL CHANNEL RECONFIGURATION COMPLETE to RNC




Inter-freq and Inter-RATmeasurement configuration

Handover execution

l Inter-freq and Inter-RAT measurement and handover

UE reports

Reconfigure the Measurement in new cell




Inter-freq neighbor list

l Inter-freq MEASUREMENT CONTROL

l By this MEASUREMENT CONTROL signaling, RNC configures the inter-freq neighbors

to UE, and requests UE report the measurement results periodically.

Filtering coefficient

Value to evaluate the cell signal

Reporting value

0.5ms interval

Periodical report




Inter-RAT neighbors

l Inter -RATMEASUREMENT CONTROL signaling

l By the MEASUREMENT CONTROL signaling, RNC configures the inter-RAT neighbors to

UE, and requests UE report the measurement results periodically, such as RSSI and BSIC.

Measurement value

Reporting value

1s interval

Periodical report




FCN of theneighbor

l Inter-freq MEASUREMENT REPORT

l UE reports the MEASUREMENT REPORT to RNC periodically based on the interval.

Measurement result




Neighbor cell Rx_lev

l Inter-RAT MEASUREMENT REPORT

l UE report the MEASUREMENT REPORT to RNC periodically based on the interval,

which is the reference for RNC handover decision.

Neighbor cellBSIC




Frequency of new cell

l PYSICAL CHANNEL RECONFIGURATION for Handover Execution

DL physical channel configuration

UL physical channel configuration

UE max Tx power

Compressed modeConfiguration




Radio link set configuration

l PYSICAL CHANNEL RECONFIGURATION for Handover Execution (Con.)

l By this PYSICAL CHANNEL RECONFIGURATION signaling, RNC handover the UE to

an Inter-freq neighbor.




l UE respond RNC PHYSICAL CHANNEL RECONFIGURATION COMPLETE signaling to

finish the handover procedure.




l Answers for the questions:

p In this case, RNC configures both inter-freq and inter-RAT measurement to UE,

but why UE handover to inter-freq cell at last?

n Because the inter-freq neighbor satisfied the inter-freq handover threshold firstly, so RNC made the decision to handover the UE to inter-freq neighbor.

p What are the functions of the Measurements control singalings after the

handover?

n They are used for:

New intra-freq measurement

Configure the RSCP threshold for 2D, 2F;

Configure the Ec/No threshold for 2D, 2F;

Terminated the inter-freq measurement;

Terminated the inter-RAT measurement.




l The procedure for inter-RAT handover is similar with inter-freq handover:

p 2D triggers compressed mode

p RNC configures measurement in compressed mode

p RNC executes the relocation(inter-RAT handover) after a GSM neighbor signal satisfies the inter-RAT handover

threshold.
