SDCCH CDR

Knowledge sharing sessions

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


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



Overview Request and allocation of SDCCH: IntroductionSDCCH

SDCCH Drop Rate

Assignment on SDCCH



Ch Activation Acknowledge

Immediate assignment command Immediate

assignment

Channel requiredRACH

PCH

Channel request

Paging request

Paging command

BSC BTS MSMSCPaging

Channel Activation



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



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


C10601


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



Overview

It represents the number of call drops due to LAPD link failure on SDCCH.

C10601

C10604C10605C10606C10646C10653C11644C11646

C10602


C10603

SDCCH Drop Rate



Overview

It represents the number of call drops due to SDCCH forcedrelease.

C10601

C10603

C10605C10606C10646C10653C11644C11646

C10602


C10604

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


C10605

SDCCH Drop Rate



Overview

It represents the number of call drops on SDCCH due to other causes.

C10601

C10603C10604C10605

C10646C10653C11644C11646

C10602


C10606

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


C10646

SDCCH Drop Rate



Overview

It represents the total number of SDCCH call drops (shortmessage).

C10601

C10603C10604C10605C10606C10646

C11644C11646

C10602


C10653

SDCCH Drop Rate



C10601

C10603C10604C10605C10606C10646C10653

C11646

C10602


Overview

C11644

SDCCH Drop Rate

Number of successful SDCCH assignments.



Overview

Number of successful SDCCH handovers.

C10601

C10603C10604C10605C10606C10646C10653C11644

C10602


Used ToolOverview Flow Chart Examples

C11646

Technical procedure

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 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 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 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



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


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


SDCCH Drop Reasons

Technical Procedure


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


RADIO link loss

Technical Procedure

SDCCH Drop Reasons


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


RADIO link loss

SDCCH Drop Reasons

Technical Procedure


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



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



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:


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


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


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


Radio Problem


Exemples 03663A:Problem Description: Transmission disconnection problem on the A-bis interfaceAction Taken: Fixing the TXM problem

Radio ProblemLAPD Problem

Hardwar Problem



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



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


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

SDCCH CDR

Documents

sdcch sdcch

rate sdcch

allocation of sdcch

rate overview

rate request

rate kpi

rate analysis

rate benaiad abdellah