SDCCH CDR
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SDCCH Drop Rate
BENAIAD Abdellah
Overview
Used Tools
Technical Procedure
Flow Chart
Exemples
08/04/2023 SDCCH Drop Rate
SDCCH
SDCCH Drop Rate
Assignment on SDCCH
Overview
This chapter is designed to provide an overview of root cause analysis for SDCCH drop rate KPI. It addresses the SDCCH drop rate analysis, investigation procedures and troubleshooting techniques to degrade the effect of this issue.
Introduction
Used ToolOverview Flow Chart ExamplesTechnical procedure
08/04/2023 SDCCH Drop Rate
Overview
SDCCH is a bidirectional logical channel used in different ways:
-Registration: periodic location update, IMSI attach/detach.-Call setup: immediate assignment.-SMS to/from MS in dedicated mode.
Introduction
SDCCH Drop Rate
Assignment on SDCCH
SDCCH
Used ToolOverview Flow Chart ExamplesTechnical procedure
08/04/2023 SDCCH Drop Rate
Overview Request and allocation of SDCCH: IntroductionSDCCH
SDCCH Drop Rate
Assignment on SDCCH
Used ToolOverview Flow Chart ExamplesTechnical procedure
08/04/2023 SDCCH Drop Rate
Ch Activation Acknowledge
Immediate assignment command Immediate
assignment
Channel requiredRACH
PCH
Channel request
Paging request
Paging command
BSC BTS MSMSCPaging
Channel Activation
Used ToolOverview Flow Chart ExamplesTechnical procedure
08/04/2023 SDCCH Drop Rate
Overview
SDCCH Drop Rate is a KPI which largely decides the subscriber service quality , the existing KPI formula is listed below:
(C10602+C10604+C10605+C10646+C10653+C10601+C10603+C106
06)*100 (C11644+C11646)
IntroductionSDCCHAssignment on SDCCHSDCCH Drop Rate
Used ToolOverview Flow Chart ExamplesTechnical procedure
08/04/2023 SDCCH Drop Rate
Overview
It represents the number of call drops due to contact loss between RMM and Service Management Module (SMM) on SDCCH.
C10602
IntroductionSDCCHAssignment on SDCCHSDCCH Drop Rate
C10603C10604C10605
C10603C10604C10605C10605C10606C10646C10653C11644C11646
Used ToolOverview Flow Chart ExamplesTechnical procedure
C10601
08/04/2023 SDCCH Drop Rate
Overview
It represents the number of call drops due to radio link failure on SDCCH.
C10603C10604C10605
IntroductionSDCCHAssignment on SDCCH
C10601
C10603C10604C10605
SDCCHAssignment on SDCCH
C10602
SDCCH Drop Rate
C10605C10606C10646C10653C11644C11646
Used ToolOverview Flow Chart ExamplesTechnical procedure
08/04/2023 SDCCH Drop Rate
Overview
It represents the number of call drops due to LAPD link failure on SDCCH.
C10601
C10604C10605C10606C10646C10653C11644C11646
C10602
IntroductionSDCCHAssignment on SDCCH
C10603
SDCCH Drop Rate
Used ToolOverview Flow Chart ExamplesTechnical procedure
08/04/2023 SDCCH Drop Rate
Overview
It represents the number of call drops due to SDCCH forcedrelease.
C10601
C10603
C10605C10606C10646C10653C11644C11646
C10602
IntroductionSDCCHAssignment on SDCCH
C10604
SDCCH Drop Rate
Used ToolOverview Flow Chart ExamplesTechnical procedure
08/04/2023 SDCCH Drop Rate
Overview
It represents the number of call drops due to force release from high priority calls on SDCCH. BSC receives force release message from BTS for high priority calls and counter increments.
C10601
C10603C10604
C10606C10646C10653C11644C11646
C10602
IntroductionSDCCHAssignment on SDCCH
C10605
SDCCH Drop Rate
Used ToolOverview Flow Chart ExamplesTechnical procedure
08/04/2023 SDCCH Drop Rate
Overview
It represents the number of call drops on SDCCH due to other causes.
C10601
C10603C10604C10605
C10646C10653C11644C11646
C10602
IntroductionSDCCHAssignment on SDCCH
C10606
SDCCH Drop Rate
Used ToolOverview Flow Chart ExamplesTechnical procedure
08/04/2023 SDCCH Drop Rate
Overview
It represents the total number of call drops due to handoverfailure on SDCCH, this counter is not allowed.
C10601
C10603C10604C10605C10606
C10653C11644C11646
C10602
IntroductionSDCCHAssignment on SDCCH
C10646
SDCCH Drop Rate
Used ToolOverview Flow Chart ExamplesTechnical procedure
08/04/2023 SDCCH Drop Rate
Overview
It represents the total number of SDCCH call drops (shortmessage).
C10601
C10603C10604C10605C10606C10646
C11644C11646
C10602
IntroductionSDCCHAssignment on SDCCH
C10653
SDCCH Drop Rate
Used ToolOverview Flow Chart ExamplesTechnical procedure
08/04/2023 SDCCH Drop Rate
C10601
C10603C10604C10605C10606C10646C10653
C11646
C10602
IntroductionSDCCHAssignment on SDCCH
Overview
C11644
SDCCH Drop Rate
Number of successful SDCCH assignments.
Used ToolOverview Flow Chart ExamplesTechnical procedure
08/04/2023 SDCCH Drop Rate
Overview
Number of successful SDCCH handovers.
C10601
C10603C10604C10605C10606C10646C10653C11644
C10602
IntroductionSDCCHAssignment on SDCCH
Used ToolOverview Flow Chart Examples
C11646
Technical procedure
SDCCH Drop Rate
08/04/2023 SDCCH Drop Rate
Used ToolOverview Flow Chart ExamplesTechnical procedure
08/04/2023 SDCCH Drop Rate
Used Tools
which can be used for accessing different performance statistics, creating queries, setting up reports, creating variables and using the Business Objects functions to analyze the data in the reports.
MCOM 4.2 ZXG10 OMCR TEMS Investigation
Business Objects 6.5
Used ToolOverview Flow Chart ExamplesTechnical procedure
08/04/2023 SDCCH Drop Rate
Used Tools
This tool is used to know the type of interference (Co-channel interference or adjacent interference) between cells; and the value of tilt, azimuth and height of the cell.
Business Objects 6.5
ZXG10 OMCR TEMS Investigation
MCOM 4.2
Used ToolOverview Flow Chart ExamplesTechnical procedure
08/04/2023 SDCCH Drop Rate
Used Tools
which can be used to provide access to all the available support activities for Operations and Maintenance in the radio and core networks, besides, the accessibility to Configuration Management, Fault management and Performance management
Business Objects 6.5 MCOM 4.2
TEMS Investigation ZXG10 OMCR
Used ToolOverview Flow Chart ExamplesTechnical procedure
08/04/2023 SDCCH Drop Rate
Used Tools
Ericsson’s tool which is used to analyze drive tests on the downlink level.
Business Objects 6.5 MCOM 4.2 ZXG10 OMCR TEMS Investigation
Used ToolOverview Flow Chart ExamplesTechnical procedure
08/04/2023 SDCCH Drop Rate
Technical Procedure
The following are main causes for SDCCH drop rate:
SDCCH Drops Due connection loss RMM SMM.SDCCH Drops Due Radio Failure.SDCCH Drops Due LAPD Failure. SDCCH Drops Due OMC Forced release SDCCH Drops Due Preemption. SDCCH Drops Due Others .SDCCH Drops Due Handover Failure. SDCCH Drops SMS (according to the formula of SDCCH Drop Rate).
SDCCH Drop Reasons troubleshooting
SDCCH Drop causes
Used ToolOverview Flow Chart ExamplesTechnical Procedure
08/04/2023 SDCCH Drop Rate
Technical Procedure
The following are main causes for SDCCH drop rate:
SDCCH Drops Due connection loss RMM SMM.SDCCH Drops Due Radio Failure. SDCCH Drops Due LAPD Failure. SDCCH Drops Due OMC Forced release .SDCCH Drops Due Preemption .SDCCH Drops Due Others .SDCCH Drops Due Handover Failure. SDCCH Drops SMS.
troubleshooting
SDCCH Drop causes
Used ToolOverview Flow Chart Examples
SDCCH Drop Reasons
Technical Procedure
08/04/2023 SDCCH Drop Rate
Technical Procedure
The following are reasons of Radio SDCCH drop:1. There exists weak coverage area, and radio signal is weak too.2. There exists interference, such as intra-network interference due to unreasonable frequency planning, and other external interference, etc.3. Unreasonable radio parameter setting 4. Equipment hardware fault, such as low output power of the power amplifier, large difference among different carrier transmission power, carrier transmitter fault, combiner fault, etc.
troubleshooting LAPD SDDCH Drop
SDCCH Drop types
Used ToolOverview Flow Chart Examples
RADIO link loss
Technical Procedure
SDCCH Drop Reasons
08/04/2023 SDCCH Drop Rate
Technical Procedure
5. Antenna feeder system fault. For example, VSWR of antenna feeder is big; antenna is too high or lower inclination is unreasonable, which causes too big the coverage range or cross-cell coverage, and forms the remote isolated island effect; etc.
troubleshooting LAPD SDDCH Drop
SDCCH Drop types
Used ToolOverview Flow Chart Examples
RADIO link loss
SDCCH Drop Reasons
Technical Procedure
08/04/2023 SDCCH Drop Rate
Technical Procedure
The following are reasons of LAPD SDCCH drop:
1. Site transmission problems, such as transmission interruption or unstable transmission .2. Site hardware fault, such as unreliable E1 cable, CMM fault, etc.3. BSC hardware fault.
troubleshooting
RADIO link loss LAPD SDDCH Drop
SDCCH Drop types SDCCH Drop Reasons
Used ToolOverview Flow Chart ExamplesTechnical Procedure
08/04/2023 SDCCH Drop Rate
Technical Procedure
SDCCH Drop rate analysis troubleshooting procedure:
1. SDCCH availability.2. SDCCH Drop causes.3. Basic NMS to know which TRX might be
faulty.4. Alarms.5. BTS measurement and cell measurement.6. Data base parameter.7. Drive testing and site audit.
SDCCH Drop Reasons troubleshooting
SDCCH Drop types
Used ToolOverview Flow Chart ExamplesTechnical Procedure
08/04/2023 SDCCH Drop Rate
Flow Chart
It is advised to locate the problem by checking radio parameters together with hardware troubleshooting.The flow of handling SDCCH drop is shown below:
Used ToolOverview Flow Chart ExamplesTechnical procedure
Is there HW problem
(cell/TRX/TS)?
Open TT to BSS team
Check SDCCH
availability
SDCCH Drop Rate
high certain
cell
Start
yes
yes
No
Reset cell
Is there LAPD
problem?
Open TT to BSS team
yes
yes
No
No
* **
RF problems
Whether radio
parameter are set
reasonably
Whether interference exist
Is there LAPD
problem?
*
Open TT to BSS team
yes
No
Modify unreasonable parameters
yes
No
yes
No
Troubleshoot
interference
**
***
Whether fault exist
in coverage
Troubleshoot
coverage
yes
No
Whether fault exist
in equipment
HW
Whether fault exist in antenna
feeder system
Troubleshoot equipment
fault
yes
No
Troubleshoot antenna
feeder fault
yes
No
***
Whether the SDCCH Drop Rate
persist
restart the investigation
yes No
END
08/04/2023 SDCCH Drop Rate
Exemples 22685A: by checking data base stat, we notice a high SDCCH Drop Rate on the site. Problem Description: using ZXG10 OMCR tool, the problem is a PA power alarm (hardware problem).Action Taken: open TT to BSS team to solve the PA power alarm.
Used ToolOverview
Radio ProblemLAPD Problem
Flow Chart Examples
Hardwar Problem
Technical procedure
08/04/2023 SDCCH Drop Rate
Exemples 03102A:Problem Description: Co-channel interference on the BCCH of 03102AAction Taken: Changing the BCCH frequency from:108-->89 22685A:Problem Description: 22685A of BSCSBA2 (BSC04) is having PA Output Power alarm on TRX1 Action Taken: Replacing the faulty TRX
LAPD Problem
Hardwar Problem
Used ToolOverview Flow Chart ExamplesTechnical procedure
Radio Problem
08/04/2023 SDCCH Drop Rate
Exemples 03663A:Problem Description: Transmission disconnection problem on the A-bis interfaceAction Taken: Fixing the TXM problem
Radio ProblemLAPD Problem
Hardwar Problem
Used ToolOverview Flow Chart ExamplesTechnical procedure
08/04/2023 SDCCH Drop Rate
Reference
[10] sjzl20062303-ZXG10-BSS (V2.97) Operation Manual (Radio Parameters)GBO_014_E1_0 Special Topic of Radio Network Optimization-82GBC_004_E1_0 Radio parameters -50ZTE Statistics
References list
08/04/2023 SDCCH Drop Rate
08/04/2023 SDCCH Drop Rate
DRT/EDRTThe DRT/EDRT fulfills conversion between voice codes at the GSM radio interface and the PSTN A-law PCM voice codes in the BSC, and implements rate adaptation (including data services rate adaptation) between them.DRT: Dual-rate transcoder, realizing the transcoding service processing. It can process 126 FRs or 32 EFRs at most.EDRT (C62): Enhanced dual-rate transcoder, an enhanced version of the DRT board. It can process 126 FRs or 126 EFRs at most.EDRT (C64): Enhanced dual-rate transcoder, an enhanced version of the DRT board. It can process 126 FRs, 126 EFRs or 126 HRs at most.Functions and PrinciplesThe board has the following functions. Performs the transcoding and rate adaptation function: It converts the 260-bit vocoder block into one hundred and sixty 8-bit A-law PCM sample signals, and vice versa. Performs framing and vocoder block synchronization, detect voice activation, regulate the block phase in the downlink direction to minimize delay, send alarms to BSC by passing through BTS through in-band signaling, processes data blocks in compliance with the protocol standard rate adaptation and re-assorting them following the A interface requirements. Provide physical-layer functions of the digital trunk interface. Separates signals, SS7 links pass transparently, and the service channels pass through the DSP for processing. Has the HDLC channels communicating directly with the, facilitating O & M Center.Fig 3.18‑1 shows the DRT/EDRT board organizational diagram. DRT uses eight DSPs, EDRT (C62) uses six, and EDRT (C64) uses two. In the given figure, n = 8, 6, 2 respectively.The DRT/EDRT comprises the DSP, CPU, and switching circuits. The DSP is responsible for mass calculations, implementing the conversion between radio service channels and ground service channels. It is the core of the DRT/EDRT board.Fig 3.18‑1 DRT/EDRT Board Organizational Diagram
HDLC
CPU
HPI
DSPn
DSP4DSP3
DSP 2
DSP 1
A
Abis
Switching circuit
DRT/EDRT Board FaultFault SymptomDSP is faulty or communication with the corresponding TCPP is disconnected.Fault Cause AnalysisCommunication between TCPP and DRT/EDRT is faulty. Hardware of the TCPP board is faulty. DSP on the DRT/EDRT board is faulty.TroubleshootingPerform the following steps to troubleshoot the fault:1. Check whether the corresponding TCPP board is faulty. If it is faulty, troubleshoot the TCPP board fault first.2. If the DSP is faulty, then go to step 6.3. Check whether there is any clock loss alarm from this board. If there is, then reset and unplug/plug the relevant board. 4. Check whether the backplane connection cable is loose or modified.5. Check whether the foreground and background data are consistent and whether relevant data are configured.6. Download the DRT and EDRT versions again and reset the board.7. Replace the DRT/EDRT board. If the fault still remains, plug the board to another slot. PrecautionsBe sure to wear an antistatic wrist strap when touching a board or component.
Appendix
08/04/2023 SDCCH Drop Rate
Radio parameters setting Cell’s minimum access level: which causes SDCCH drop in weak coverage area.Unreasonable BSIC settingUnreasonable power control setting, such as unreasonable level, quality power control threshold, which will cause MS to reduce power even in the case of weak signal and poor call quality. ()Unreasonable FH parameter setting: parameter setting Unreasonable MAIO configuration will cause co-channel interference and adjacent-channel interference within one site.Incomplete adjacent-cell data definition or configuration errorCongestion exists in adjacent cell
Radio parameters