CS Call Flow v3
Transcript of CS Call Flow v3
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1 © Nokia Siemens Networks Presentation / Author / Date Soc Classification level
Call Flow
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Content:
• Message Flow
• System Information Block Type
• Common Call Failure Analysis
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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)
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CS Call Flow (2/3)
UE RNCBTS CNRANAP: RAB Assignment Request
NBAP: Radio Link Reconfiguration Prepare
NBAP: Radio Link Reconfiguration Ready
ALCAP: ERQ (Establish Request)
ALCAP: ECF (Establish Confirm)
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
ALCAP: ERQ (Establish Request)
ALCAP: ECF (Establish Confirm)
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
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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)
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RRC Setup Phase (1/5)
UE RNCBTS CNRRC: RRC Connection Request
• 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….
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RRC Setup Phase (2/5)
Contains “initial UE identity” and “established cause” to indicate the reason for the connection establishment.
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RRC Setup Phase (3/5)
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 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.
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RRC Setup Phase (4/5)
• 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.
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RRC Setup Phase (5/5)
• In Force Mode. There isn’t any InterRAT-UE-RadioAccessCapability info.
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RAB Setup Phase CS Calls
UE RNCBTS CN
NBAP: Radio Link Reconfiguration Prepare
NBAP: Radio Link Reconfiguration Ready
ALCAP: ERQ (Establish Request)
ALCAP: ECF (Establish Confirm)
NBAP: Radio Link Reconfiguration Commit)
RRC: Radio Bearer Setup
RRC: Radio Bearer Setup Complete
RANAP: RAB Assignment Response
ALCAP: ERQ (Establish Request)
ALCAP: ECF (Establish Confirm)
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.
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RAB Setup Phase PS Calls
UE RNCBTS CN
NBAP: Radio Link Reconfiguration Prepare
NBAP: Radio Link Reconfiguration Ready
ALCAP: ERQ (Establish Request)
ALCAP: ECF (Establish Confirm)
NBAP: Radio Link Reconfiguration Commit)
RRC: Radio Bearer Setup
RRC: Radio Bearer Setup Complete
RANAP: RAB Assignment Response
ALCAP: ERQ (Establish Request)
ALCAP: ECF (Establish Confirm)
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
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RRC & L3 Message Flow (1/2)
Measurement_Control contains:
• Defined 3G & 2G neighbours.
• Intra & inter Frequency, irat handover criteria.
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RRC & L3 Message Flow (2/2)
MTC’s ISDN number
UE IMEI number
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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
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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
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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.
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Soft Handovers
UE RNCBTS
NBAP: Radio Link Setup Request (Soft handover)
NBAP: Radio Link Setup Response (Soft handover)
ALCAP: ERQ (Establish Request)
ALCAP: ECF (Establish Confirm)
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
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Inter RAT Handover (1/5)
UE RNCBTS CN
NBAP: Radio Link Reconfiguration Prepare
NBAP: Radio Link Reconfiguration Ready
RRC: Physical Channel Reconfiguration
RRC: Physical Channel Reconfiguration Complete
RANAP: Iu Release Complete
RANAP: Iu Release Command
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)
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Inter RAT Handover (2/5)
Current IRAT criteria for Maxis network is set based on RSCP.
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Inter RAT Handover (3/5)
Measurement Control sent by RNC contains all inter RAT neighbours that were defined in RNC and event 3a parameters.
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Inter RAT Handover (4/5)
Verified BSIC shows the inter RAT cell id that corresponds to the id in the previous measurement control message.
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Inter RAT Handover (5/5)
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.
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Cell Change Order
UE RNCBTS CN
NBAP: Radio Link Reconfiguration Prepare
NBAP: Radio Link Reconfiguration Ready
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)
RANAP: Iu Release Complete
RANAP: Iu Release Command
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System Information Block Type
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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)
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SIB 2
URA identity
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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.
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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
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SIB 7
Uplink interference, affect the open loop power control.
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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)
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SIB 11 (2/2)
Cell individual offset
Intra frequency neighbour measurement is based on EcNo.
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Common Call Failure Analysis
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Actix WorkbookActix KPI Report – An efficient way to process log files and
identify call failures.
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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.
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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.
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Call Blocked
– Any abnormal call released without “Alerting” message.
Call Dropped
– Any abnormal call released without “Disconnect” message.
Call Blocked and Call Dropped Classification
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Blocked #1: Call Setup Without RRC Connection Request (1/2).
CM_Service_Request without RRC connection request
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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
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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
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Blocked #2: Soft Handover Failure (UE Failed To Received Active Set Update).
Sample of IMSI trace
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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.
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Dropped #1: Radio Link Failure. Hardware Failure Detected.
Both UE sent uplink disconnection simultaneously after T313 timer expired.
Sample of IMSI trace
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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.
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Dropped #2: Unnecessary High UE Tx Power
Good radio condition but the UE always requested to transmit its maximum transmission power.
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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.
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Event Tracker
A tracker for all failure events of all WP and clusters.