CS Call Flow v3

1 © Nokia Siemens Networks Presentation / Author / Date Soc Classification level

Call Flow


Content:

• Message Flow

• System Information Block Type

• Common Call Failure Analysis


CS Call Flow (1/3)

UE RNCBTS CNRRC: RRC Connection Request

NBAP: Radio Link Setup Request

NBAP: Radio Link Setup Response

ALCAP: ERQ (Establish Request)

ALCAP: ECF (Establish Confirm)

RRC: RRC Connection Setup

L1 Synchronization

NBAP: Synchronization Indicator

RRC: RRC Connection Setup Complete

RRC: Initial Direct Transfer (MM: CM Service Request)

RANAP: Initial UE Message (MM: CM Service Request)

RANAP: Common ID

RRC: Downlink Direct Transfer (MM: Identity Request)

RRC: Uplink Direct Transfer (MM: Identity Response)RANAP: Direct Transfer (MM: Identity Response)

RANAP: Direct Transfer (Identity Request)

RANAP: Security Mode Command

RRC: Security Mode Command

RRC: Security Mode Complete

RANAP: Security Mode Complete

RRC: Uplink Direct Transfer (CC: Setup)

RANAP: Direct Transfer (CC: Setup)

RANAP: Direct Transfer (CC: Call Proceeding)

RRC: Downlink Direct Transfer (CC: Call Proceeding)


CS Call Flow (2/3)

UE RNCBTS CNRANAP: RAB Assignment Request

NBAP: Radio Link Reconfiguration Prepare

NBAP: Radio Link Reconfiguration Ready



NBAP: Radio Link Reconfiguration Commit)

RRC: Radio Bearer Setup

RRC: Radio Bearer Setup Complete

RANAP: RAB Assignment Response

RANAP: Direct Transfer (CC: Alerting)

RANAP: Direct Transfer (CC: Connect)

RRC: Downlink Direct Transfer (CC: Connect)

RRC: Uplink Direct Transfer (CC: Connect Acknowledge)

RANAP: Direct Transfer (CC: Connect Acknowledge)

Conversation In Progress

RRC: Uplink Direct Transfer (CC: Release Complete)

RANAP: Direct Transfer (CC: Release Complete)

RANAP: Iu Release Command



RRC: Downlink Direct Transfer (CC: Alerting)

RRC: Uplink Direct Transfer (CC: Disconnect)

RANAP: Direct Transfer (CC: Disconnect)

RANAP: Direct Transfer (CC: Release)

RRC: Downlink Direct Transfer (CC: Release)

RANAP: Iu Release Complete


CS Call Flow (3/3)

UE RNCBTS CNALCAP: REL (Release Request)

NBAP: Radio Link Deletion Request

NBAP: Radio Link Deletion Response

RRC: RRC Connection Release Complete

SCCP: RLSD (Released)

ALCAP: RLC (Release Confirm)

RRC: RRC Connection Release

ALCAP: REL (Release Request)

ALCAP: RCL (Release Confirm)

SCCP: RLC (Release Complete)


RRC Setup Phase (1/5)


• Common cause on RRC Connection Request:

• Originating Conversational Call – CS calls.

• Originating High Priority Signaling – PS calls.

• Originating Low Priority Signaling – SMS.

• Registration – LAC/RAC update or GPRS Attach.

• InterRAT Reselection – InterRAT reselection from 2G.

• Others….



Contains “initial UE identity” and “established cause” to indicate the reason for the connection establishment.




NBAP: Radio Link Setup Request

NBAP: Radio Link Setup Response



RRC: RRC Connection Setup

L1 Synchronization

NBAP: Synchronization Indicator

RRC: RRC Connection Setup Complete

• RRC connection:

• N300 – the number of repetition on RRC Connection Request.

• T300 – the interval between each repetition on RRC Connection Request.

• When a physical dedicated channel established is initiated by the UE, the UE starts timer T312 and wait for L1 to indicate N312 “in sync” indications.

• On receiving N312 “in sync” indications, the physical channel is considered established and the timer T312 stopped and reset.

• When synchronization indication is received, the outer loop and closed loop power control will start.



• How to identify whether the UE is in dual mode or force mode?

• Check on GSM Classmark 2 & 3 info in RRC Connection Setup Complete.



• In Force Mode. There isn’t any InterRAT-UE-RadioAccessCapability info.


RAB Setup Phase CS Calls

UE RNCBTS CN











RANAP: RAB Assignment Request

AC to check whether to accept or reject RAB Assignment Request

• If successful reservation of resources at BTS, NBAP: Radio link Reconfiguration Ready will be sent to RNC.


RAB Setup Phase PS Calls

UE RNCBTS CN











RANAP: RAB Assignment Request

AC to check whether to accept or reject RAB Assignment Request

• If successful reservation of resources at BTS, NBAP: Radio link Reconfiguration Ready will be sent to RNC.

RRC: Activate PDP Context RequestRANAP: Activate PDP Context Request

RANAP: Activate PDP Context AcceptRRC: Activate PDP Context Accept


RRC & L3 Message Flow (1/2)

Measurement_Control contains:

• Defined 3G & 2G neighbours.

• Intra & inter Frequency, irat handover criteria.


RRC & L3 Message Flow (2/2)

MTC’s ISDN number

UE IMEI number


Late Assignment Feature – RAB Setup (1/2)

When “Call_Proceeding” is received in the MOC, CN will send a paging message to the MTC.

Types of paging:

Paging_type I - UE in Idle mode

Paging_type II - UE in connected mode


Late Assignment Feature – RAB Setup (2/2)

As soon as Call_Confirmed is received by the RNC, CN will send RAB assignment request to RNC with requested max bit rate followed by RAB setup to UE in MOC.

Example of MaxBitRate for different services:

• AMR Voice - 12200

• CS64 - 64000

• PS384 - 384000


RRC & L3 Message Flow – RRC Connection Release

When Disconnect message is received from the UE, CN will send a Release message followed by RNC releasing the RRC connection.

The number of RRC Release Complete will depends on N308 and interval is T308.


Soft Handovers

UE RNCBTS

NBAP: Radio Link Setup Request (Soft handover)

NBAP: Radio Link Setup Response (Soft handover)



RRC: Active Set Update

RRC: Measurement Report (e1a/e1c)

Decision to setup new radio link

NBAP: Radio Link Addition Request (Softer handover)

NBAP: Radio Link Addition Response (Softer handover)

RRC: Active Set Update Complete

RRC: Measurement Report (e1b)

RRC: Active Set Update

RRC: Active Set Update Complete

NBAP: Radio Link Deletion Success

NBAP: Radio Link Deletion


Inter RAT Handover (1/5)

UE RNCBTS CN



RRC: Physical Channel Reconfiguration

RRC: Physical Channel Reconfiguration Complete



RANAP: Relocation Command

RRC: Measurement Report (e2d)

RANAP: Relocation Preparation

RRC: Handover From UTRAN Command

NBAP: Radio Link Reconfiguration Commit

RRC: Measurement Control (GSM NB List & iRAT HO parameters)

RRC: Measurement Report (GSM RSSI Measurement)

RRC: Measurement Report (GSM BSIC Verification / e3a)



Current IRAT criteria for Maxis network is set based on RSCP.



Measurement Control sent by RNC contains all inter RAT neighbours that were defined in RNC and event 3a parameters.



Verified BSIC shows the inter RAT cell id that corresponds to the id in the previous measurement control message.



If the relocation is successful, RNC will send Handover_Command to instruct the the UE to perform the handover to the 2G cell that described in the message.

The UE is in 2G once it sends Handover Complete message.


Cell Change Order

UE RNCBTS CN



RRC: Physical Channel Reconfiguration

RRC: Physical Channel Reconfiguration Complete

RANAP: SRNS Context Response

RANAP: SRNS Context Request

RRC: Measurement Report (e2d)

RRC: Cell Change Order From UTRAN

NBAP: Radio Link Reconfiguration Commit

RRC: Measurement Control (GSM NB List & iRAT HO parameters)

RRC: Measurement Report (GSM RSSI Measurement)

RRC: Measurement Report (GSM BSIC Verification / e3a)



25 © Nokia Siemens Networks Presentation / Author / DateI insert classification level

System Information Block Type


SIB 1

LAC=48100

Periodic location update in deci hour, 1 deci hour = 6 min

1 means UE must complete IMSI attach

RAC=180

Network Mode of Operation = 1

1 means Network Mode of Operation II

DRX cycle length = 2^7 = 128ms (unit = 10ms)


SIB 2

URA identity


SIB 3RNCid (12 bits) + CellID (16 bits)

RNCid = 1FB = 507

CellID = D3D8 = 54232

Cell reselection is based on EcNo

Sintrasearch = 14dB (IEx2)

Sintersearch = 8 dB (IEx2)

RAT technology = GSM, SsearchRAT = 4dB (IEx2)

Trereselection=1s, Max UE TxPower = 24 dBm

Qqualmin=-18dB, Qrxlevmin=-115dBm (2xIE+1)

Cellrop and access class barred.


SIB 5

Power level is -6 and -4 dB below CPICH

16 signatures are available

SF64 and Preamble scrambling code 0

Preamble Power setting

CPICH power


SIB 7

Uplink interference, affect the open loop power control.


SIB 11 (1/2)

HCS not used

Cell reselection is based on EcNo

Intra frequency cell id 0 corresponds to serving cell.

Scrambling code.

UE is instructed to read SFN.

No Tx diversity.

Max UE tx power in neighbouring cell is 24 dBm.

Neighbour cell qqualmin=-20dB, qrxlevmin=-101 (IEx2+1)


SIB 11 (2/2)

Cell individual offset

Intra frequency neighbour measurement is based on EcNo.

33 © Nokia Siemens Networks Presentation / Author / DateI insert classification level

Common Call Failure Analysis


Actix WorkbookActix KPI Report – An efficient way to process log files and

identify call failures.


IMSI decoderctr_ftp.exe

To decode the binary IMSI file.

CTRdeMessage_ver007.xls

To arrange and create symbolic link for both text and html into a Excel workbook.


Sample Of IMSI ResultTime Stamp IMSI Trace Id Messages

Synchronize the time with RC can be very time-saving when comes to analyze the log files with IMSI trace.


Call Blocked

– Any abnormal call released without “Alerting” message.

Call Dropped

– Any abnormal call released without “Disconnect” message.

Call Blocked and Call Dropped Classification


Blocked #1: Call Setup Without RRC Connection Request (1/2).

CM_Service_Request without RRC connection request


Blocked #1: Call Setup Without RRC Connection Request (2/2).

RRC Connection Release message sent by RNC but not received by UE.

RRC Connection Release message not received by UE in the previous call.

Sample of IMSI trace


Problem Description• The problem happens during the short-call drive (usually cluster drive). The UE triggers “CM

Service Request” without setting up a new RRC signaling and result in blocked call.

Possible Solution• This is due to the “RRC Connection Release” message not received by UE in the previous

call (as shown in the imsi trace) and the UE “assumes” the RRC signaling still exists. Therefore, when the predefined idle time expired, the UE starts the next call without setting up a new RRC connection. This problem happens only in Nemo Outdoor with Nokia 6680 and it’s been classified as “compatibility problem” by Nemo support team.

Blocked #1: Analysis Summary


Blocked #2: Soft Handover Failure (UE Failed To Received Active Set Update).



Blocked #2: Analysis Summary

Problem Description• During call setup stage, the UE sent a Measurement Report on the cell in the monitored set

and recommended a handover. However, the request was not responded by the network. After multiple attempts, the call released abnormally when the radio environment cannot sustain the connection. The problem can occur at any stage of the call regardless of the condition of the radio environment.

Possible Solution• It has been escalated to TAC 2 for further investigation.


Dropped #1: Radio Link Failure. Hardware Failure Detected.

Both UE sent uplink disconnection simultaneously after T313 timer expired.



Dropped #1: Analysis Summary

Problem Description• Soon after the deletion of the scrambling code 172 from the active set, both MOC & MTC

send an UL “Disconnect” message simultaneously to the network with failure cause “Radio Link Failure”.

Possible Solution• The problem may caused by site intermittent or the hardware failure in the Node B. It is

recommended to check the site status with Radio Commander (RC) and verify statistics measurement counters for RTWP, TCP, AC Rejection, and CC Trigger to get a hint of the site condition.


Dropped #2: Unnecessary High UE Tx Power

Good radio condition but the UE always requested to transmit its maximum transmission power.


Dropped #2: Analysis Summary

Problem Description• In soft handover, the UE connects to a distant cell and the distant cell is the best serving cell

in active set. The UL performance (RSCP & EcNo) of the best serving cell is good, however, the UE is always requested to transmit its maximum transmission power. When all other cells have been released and only that distant cell is kept in the active set, the call dropped.

Possible Solution• This problem is caused by the cell overshooting. The solution is to remove the coverage of

the overshooting cell that caused interference and handover sequence problem.


Event Tracker

A tracker for all failure events of all WP and clusters.

Documents

CS Call Flow v3