OWO300110_Signaling Analysis of Typical UTRAN Procedures_Optimization_ISSUE1.pdf

Signaling Analysis of Typical UTRAN Procedures

Confidential Information of Huawei. No Spreading Without Permission

Revision update record:

Add the pictures of signaling procedures in the remarks(Page38&43-45&50-52&59-65).



UMTS network is composed of CN,UTRAN and UE.

For UTRAN network includes RNC and NodeB .

RNS means Radio Network Subsystem ,which is composed of one RNC and the the NodeBs under its control.

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.

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



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.

IUB interface signaling is called NBAP signaling, which can be used for locating NodeB’s faults.

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.

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

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



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;

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.

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.

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.

During the PS service period, UTRAN may reconfigure the radio bear of the service based on the network load or user’s activity.

In case of service changing (such as to change a VP service to a AMR service ), RAB modification procedure is needed.



The logical structure of system information is like a tree.

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



By the drive test tool, we can trace the system information, so as to know some basic information of a cell.

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

MIB: master information block

SB: scheduling block

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



MIB: master information block

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

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



SB: Scheduling block

SB only tells the scheduling information of SIB, such as the scheduling information of SIB1/SIB2/SIB3 in this example.

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

Scheduling information of SIB1





SIB1:System Information Block1

DRX means discontinuous reception, used to save the battery of the UE when monitoring the paging.

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



SIB2 indicates the URA ID of a cell, URA ID is used for mobility management of a UE in URA-PCH state.



SIB3:System Information Block 3

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

Try to answer the following questions: What is the use of “Max allowed UE transmitting power” here?

To calculate Pcompensation in Selection Criteria calculation In the example of this page, what is the RNC ID and cell ID?

HEX2DEC(006F) = 111 = RNC ID HEX2DEC(1BDB) = 7131 = Cell ID

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 purpose of this optimization? what is the disadvantage?

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



SIB5:System information Block5

Question:

For random access procedure, what is the required resource for a UE?

PICH/AICH power

PRACH configration

RACH transmission format

Available access resource

Mapping between AC and ASC



SIB5:System information 5 (Cont.)

Question:

What is the use of PCPICH power here?

What is the use of cell HSPA capability?

PCPICH power

AICH SF

Cell HSDPA capability

Cell HSUPA capability

Random access parameters

Configuration of SCCPCH

Configuration of PICH



SIB7:System information 7

SIB7 broadcasts UL RTWP to UE .

UL interference

Dynamic persistence level



SIB11:System information block 11

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

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

Intra-freq neighbor list

Scambling code



SIB11:system information block 11（cont.）

For GSM neighbors, it includes BSIC, BCCH information

GSM neighbor list

BCCH

Qoffset for cell reselection

Rx level min

BSIC



Paging message may be initiated by CN or RNC. Based on UE’s state , RNC may send paging type1 or type2 on Uu interface.

Page type1 is for the UE in IDLE, CELL-PCH ,URA-PCH state. Paging type1 is sent on PCCH and DRX is used.

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



IU Interface paging signaling

Paging signaling on IU interface include:

Type of the domain (CS or PS)

UE ID（IMSI is mandatory, but TMSI/PTMSI is optional）

LAC/RAC

Paging cause

Source of the paging

UE IMSI

UE TMSI

LAC

Paging cause



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.

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

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



By setting up RRC connection with UTRAN, UE enters connected mode. This procedure is triggered by UE sending “RRC CONNECTION REQUEST” on RACH.

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.

For RRC Setup on DCH or HSPA, RNC shall configure NodeB to prepare RL , after that, by “RRC CONNECTION SETUP” signaling, RNC configures UE；

UE sends “RRC CONNECTION SETUP COMPLETE” as the response, in this signaling, UE reports the capability of itself.

An example of RRC setup procedure



For “RRC CONNECTION REQUEST” signaling, we should pay attention to the following elements:

UE ID

Cause：Based on this cause ,RNC decides the channel for RRC connection.

Service cell CPICH Ec/No：used for downlink DCH initial power calculation.

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



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

RRC CONNECTION SETUP (Con.)

The data rate of the channel is configured in transport channel: TB Size * TB Number / TTI

The configurations for UL and DL transport channels are separate.



Transport channel

TTI 10ms

TB size

TB Number

Channel coding

Target BLER

RRC CONNECTION SETUP(Con.)

Configuration of downlink transport channel is similar with uplink,

Question:

Why the BLER is configured in downlink only?

Because this is for UL power control (closed-loop) controlled by RNC to UE



Power offset

Uplink code


DPCCH_Power_Offset = PCPICHPower + UL Interference + DefaultConstantValue

Question:

How the RNC allocates uplink scrambling code ?

UL PSC is assigned by RNC in per call basis. There are 224 long & 224 short codes divided between RNC, each RNC has its own planned range.

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

UL SF = 64, DL SF = 128, bit rate = 12.2kbps

Uplink powerControl algorithm



DL OVSF code


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

No, the channel rate is the same, the SF different is because for DL, the SF code is subjected to a serial-to-parallel conversion before TM, which effectively double up the rate of physical channel, means half of the channel’s data is carried on I while another half on Q, while for UL there is no serial-to-parallel conversion. Hence DL SF = UL SF/2

Downlink powercontrol Mode



Downling DCH OVSF code


In downlink ,physical RLs are configured separately

Question：

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

Which OVSF code is allocated in this case?

SF128 From the code allocation, can you judge if the HSDPA is active in this cell?

Down PSC



RRC CONNECTION SETUP COMPLETE:

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

UE RF capability

Inter-RAT capability

Compressed mode and measurement capabilities

HSPA capabilities.

UE’s radio capability



RRC CONNECTION SETUP COMPLETE(Con.)

UE’s GSM capabilities affect the RNC’s decision in Inter-RAT handover.

UE’s GSM setting

UE’s GSM Class



RRC CONNECTION SETUP COMPLETE(Con.)

The measurement capabilites affect the RNC’s measurement control.

UE’s power level

The 2100M measurement capability

The GSM measurement capability

The extension band measurement capability



RRC CONNECTION SETUP COMPLETE (Con.)

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

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

L2 capabilities

HSPA capability

NACC capability of UE



We can check the type of channel from this signaling:

If we want to setup RRC on HSPA, beside the configuration of the RNC , the UE’s HSPA capability is required also, because UE should report HSPA capability to RNC in the ”RRC CONNECTION REQUEST” signaling.



NAS means “non access stratum”.

After RRC connection setup, UE transmits “Initial UE message” to CN to trigger NAS signaling procedure.

Via NAS signaling, UE can realize location registration (IMSI ATTACH – power on and attached to network), GPRS ATTACH (attach to GPRS network), PDP activation, authentication, security mode, and so on.

“RAB Assignment” is after the NAS procedure.

Most of the NAS signaling are transparent messages in UTRAN, so they are called “directed transfer” signaling.



Initial UE message is transferred to CN by RNC.



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

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

Question:

In which scenario, UE triggers this procedure.

UE power on and request to attach to network

Message type

Message content

LAC



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



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



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



CN sends “Common ID” to RNC, which is used for paging transmission during the connection

Question:

Why the Common ID is IMSI but not TMSI?

The COMMON ID message is used to inform the RNC of the IMSI. The RNC will use this information for paging co-ordination of connections from MSC and SGSNs.

Hence IMSI is mandatory because it is needed for calculation of paging group and also for WCDMA RAN paging co-ordination.



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.



An Example of Direct Transfer Message

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

In this example, CN requests UE’s authentication.

Authentication Request



An Example of Direct Transfer Message (Con.)

Authentication Response



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



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



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



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.

In this example, after UE’s “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.

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

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.

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



CN sends the service and UE related configurations to RNC via “RAB ASSIGNMENT REQUEST ” signaling.

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



RB SETUP Signaling：

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

Questions：

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

HSPA – H-RNTI & E-RNTI 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



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



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



An example of HSDPA+384K Message ：

RAB assignment request :



RB setup :



An example of VOICE Message ：




RB setup request :



An example of HSDPA+64K Message ：




RB setup request :



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.

When the measured signals satisfy some threshold configured in “measurement control”, UE triggers a “MEASUREMENT REPORT” to RNC.

According to this “MEASUREMENT REPORT”, RNC may make a decision ,then triggers the handover.

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

A “Measurement Control” of intra-frequency measurement

By the “Measurement control” signalings with the same measurement ID, RNC can modify the neighbor list of the UE.

Similar with SIB11, neighbor list in “measurement control” signaling includes the PSCs of the neighbors.



filter coefficient for measured results

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

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

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

In 3GPP 25.331, 1a,1b,1c,1d,1e,1f and 1j event are defined for FDD. Huawei doesn’t use event 1e, and by default , 1j is not switched on either.

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

Measurement Report

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

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

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

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

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

Active set update

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



As a response, UE sends “ACTIVESET UPDATE COMPLETE” to RNC to complete this handover



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

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

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

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

Although not necessary, but it is typical that HSDPA and HSUPA serving cells are the same.



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

From signaling, we can see the serving cell for HSDPA and HSUPA could be different. But Huawei’s algorithm keeps them identical.



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

In compressed mode, RNC send both “MEASUREMENT CONTROL” for inter-freq and inter-RAT measurement.

Based on UE’s “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

Procedure to start compressed mode

After RB setup, RNC sends 2D and 2F thresholds to UE. When the current carrier meets the threshold, UE reports 2D event. RNC reconfigures the RL in NodeB and sends “PHYSICAL CHANNEL

RECONFIGURATION” signaling to configure the compressed mode. Questions：

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

How to confirm the 2D report is triggered by Ec/No or RSCP? If 2F is trigged during the compressed mode, what will happen then?

2D Measurement report

RSCP Threshold for 2D



Answers to the Questions： Is it necessary for the RNC to configure 2D with Ec/No and RSCP

separately? What is the benefit from this? 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.

How to confirm a 2D report is caused by Ec/No or RSCP? The measurement ID of the report signaling can indicate this.

If 2F is trigged during the compressed mode, what will happen then? Compressed mode will be stopped by RNC in this case.



Measurement quantity

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

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

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

2D parameters

2F parameters



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



Configuration of compressed slots

“PHYSICAL CHANNEL RECONFIGURATION” to start the compressed mode

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.

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



UE respond “PHYSICAL CHANNEL RECONFIGURATION COMPLETE” to RNC



Inter-freq and Inter-RATmeasurement configuration

Handover execution

Inter-freq and Inter-RAT measurement and handover

UE reports

Reconfigure the Measurement in new cell



Inter-freq neighbor list

Inter-freq “MEASUREMENT CONTROL”

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

Inter -RAT“MEASUREMENT CONTROL” signaling

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

Inter-freq “MEASUREMENT REPORT”

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

Measurement result



Neighbor cell Rx_lev

Inter-RAT “MEASUREMENT REPORT”

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

“PYSICAL CHANNEL RECONFIGURATION” for Handover Execution

DL physical channel configuration

UL physical channel configuration

UE max Tx power

Compressed modeConfiguration



Radio link set configuration

“PYSICAL CHANNEL RECONFIGURATION” for Handover Execution (Con.)

By this “PYSICAL CHANNEL RECONFIGURATION” signaling, RNC handover the UE to an Inter-freq neighbor.



UE respond RNC “PHYSICAL CHANNEL RECONFIGURATION COMPLETE” signaling to finish the handover procedure.



Answers for the questions:

In this case, RNC configures both inter-freq and inter-RAT measurement to UE, but why UE handover to inter-freq cell at last?

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.

What are the functions of the “Measurements control” singalings after the handover?

They are used for:New intra-freq measurementConfigure the RSCP threshold for 2D, 2F;Configure the Ec/No threshold for 2D, 2F;Terminated the inter-freq measurement;Terminated the inter-RAT measurement.



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

2D triggers compressed mode

RNC configures measurement in compressed mode

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

OWO300110_Signaling Analysis of Typical UTRAN Procedures_Optimization_ISSUE1.pdf

Documents

Transcript of OWO300110_Signaling Analysis of Typical UTRAN Procedures_Optimization_ISSUE1.pdf