Sdcch drop rate

Knowledge sharing sessions

Overview
Used Tools
Technical Procedure
SDCCH Drop Rate
Flow Chart
Exemples

BENAIAD Abdellah

Overview Used Tool Technical procedure Flow Chart Examples

Overview
Introduction
SDCCH
Assignment on SDCCH
SDCCH Drop Rate

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.

28/12/2010 SDCCH Drop Rate


Overview
Introduction
SDCCH
Assignment on SDCCH
SDCCH Drop Rate
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.



Overview Request and allocation of SDCCH:
Introduction
SDCCH
Assignment on SDCCH
SDCCH Drop Rate



MS
BSC Paging BTS Paging MS
C Paging
command request
PCH

Channel required Channel request
RACH
Channel Activation

Ch Activation
Acknowledge
Immediate
assignment
command Immediate
assignment



Overview
Introduction
SDCCH
Assignment on SDCCH
SDCCH Drop Rate

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+C10606)*100

(C11644+C11646)



Overview
Introduction
SDCCH
Assignment on SDCCH
SDCCH Drop Rate
C10601
C10602
C10603
C10603
It represents the number of call drops due to contact
C10604
C10604 loss between RMM and Service Management Module
C10605
C10605 (SMM) on SDCCH.
C10606
C10646
C10653
C11644
C11646



Overview
Introduction
SDCCH
Assignment on SDCCH
SDCCH Drop Rate
C10601
C10602
C10603
C10603
C10604
C10604 It represents the number of call drops due to radio link
C10605
C10605 failure on SDCCH.
C10606
C10646
C10653
C11644
C11646



Overview
Introduction
SDCCH
Assignment on SDCCH
SDCCH Drop Rate
C10601
C10602
C10603
C10604 It represents the number of call drops due to LAPD link
C10605 failure on SDCCH.
C10606
C10646
C10653
C11644
C11646



Overview
Introduction
SDCCH
Assignment on SDCCH
SDCCH Drop Rate
C10601
C10602
C10603
C10604 It represents the number of call drops due to SDCCH
C10605 forced
C10606
release.
C10646
C10653
C11644
C11646



Overview
Introduction
SDCCH
Assignment on SDCCH
SDCCH Drop Rate
C10601
C10602
C10603 It represents the number of call drops due to force
C10604
C10605
release from high priority calls on SDCCH. BSC
C10606 receives force release message from BTS for high
C10646 priority calls and counter increments.
C10653
C11644
C11646



Overview
Introduction
SDCCH
Assignment on SDCCH
SDCCH Drop Rate
C10601
C10602
C10603
C10604
C10605
It represents the number of call drops on SDCCH due
C10606 to other causes.
C10646
C10653
C11644
C11646



Overview
Introduction
SDCCH
Assignment on SDCCH
SDCCH Drop Rate
C10601
C10602
C10603
C10604 It represents the total number of call drops due to
C10605 handover
C10606
failure on SDCCH, this counter is not allowed.
C10646
C10653
C11644
C11646



Overview
Introduction
SDCCH
Assignment on SDCCH
SDCCH Drop Rate
C10601
C10602
C10603
C10604 It represents the total number of SDCCH call drops
C10605 (short
C10606
message).
C10646
C10653
C11644
C11646



Overview
Introduction
SDCCH
Assignment on SDCCH
SDCCH Drop Rate
C10601
C10602
C10603
C10604
C10605 Number of successful SDCCH assignments.
C10606
C10646
C10653
C11644
C11646



Overview
Introduction
SDCCH
Assignment on SDCCH
SDCCH Drop Rate
C10601
C10602
C10603
C10604
C10605 Number of successful SDCCH handovers.
C10606
C10646
C10653
C11644
C11646



Used Tools
Business Objects 6.5
MCOM 4.2
ZXG10 OMCR
TEMS Investigation

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.



Used Tools
MCOM 4.2
ZXG10 OMCR
TEMS Investigation

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.



Used Tools
MCOM 4.2
ZXG10 OMCR
TEMS Investigation

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



Used Tools
MCOM 4.2
ZXG10 OMCR
TEMS Investigation

Ericsson’s tool which is used to analyze drive tests on
the downlink level.


Overview Used Tool Technical Procedure Flow Chart Examples

Technical Procedure
SDCCH Drop causes
SDCCH Drop Reasons
troubleshooting 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).



Technical Procedure
SDCCH Drop causes
SDCCH Drop Reasons
troubleshooting
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.



Technical Procedure
SDCCH Drop types
SDCCH Drop Reasons The following are reasons of Radio SDCCH drop:
RADIO link loss 1. There exists weak coverage area, and radio signal
LAPD SDDCH Drop is weak too.
troubleshooting
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.



Technical Procedure
SDCCH Drop types
SDCCH Drop Reasons
RADIO link loss
LAPD SDDCH Drop
troubleshooting

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.



Technical Procedure
SDCCH Drop types
SDCCH Drop Reasons
RADIO link loss
LAPD SDDCH Drop
troubleshooting 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.



Technical Procedure
SDCCH Drop types
SDCCH Drop Reasons
troubleshooting 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.



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:


Start

SDCCH
Drop Rate
high certain
cell

yes

No Check yes
SDCCH
availability

yes Is there
Open TT to
BSS team
LAPD
problem?

No

Is there HW
Open TT to
yes problem
BSS team (cell/TRX/TS
)?

No

* Reset cell

* **

Is there yes
Open TT to BSS
LAPD
problem? team

No

RF problems

Whether
radio yes Modify
parameter unreasonable
are set parameters
reasonably

No

Whether yes Trouble
interference shoot
exist interference

No

***
Whether yes
fault exist in
Trouble
coverage shoot coverage

No

Whether yes
fault exist in Troubleshoot
equipment equipment fault
HW

No

Whether
fault exist in yes Trouble
antenna shoot antenna
feeder feeder fault
system

No
Whether the No
yes SDCCH
Drop Rate
persist

restart the
investigation END


Exemples 22685A:
Hardwar Problem
by checking data base stat, we notice a high SDCCH
Radio Problem
LAPD Problem 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.



Exemples 03102A:
Hardwar Problem
Problem Description: Co-channel interference on the
Radio Problem
LAPD Problem BCCH of 03102A
Action 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



Exemples 03663A:
Hardwar Problem
Problem Description: Transmission disconnection
Radio Problem
LAPD Problem problem on the A-bis interface
Action Taken: Fixing the TXM problem


References list

Reference

[10] sjzl20062303-ZXG10-BSS (V2.97) Operation
Manual (Radio Parameters)
GBO_014_E1_0 Special Topic of Radio Network
Optimization-82
GBC_004_E1_0 Radio parameters -50
ZTE Statistics


Appendix

DRT/EDRT
The 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 Principles
The 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

i
t
c
u
i
r
c
n
g
h
i
t
c
i
w
S
DSPn
. . A
.. ..
CPU
DSP4
DSP3 Abis
HPI DSP 2
DSP 1

DRT/EDRT Board Fault
Fault Symptom
DSP is faulty or communication with the corresponding TCPP is disconnected.
Fault Cause Analysis
Communication between TCPP and DRT/EDRT is faulty. Hardware of the TCPP board is faulty. DSP on the DRT/EDRT board is faulty.
Troubleshooting
Perform 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.
Precautions
Be sure to wear an antistatic wrist strap when touching a board or component.


Radio parameters

Radio parameters setting

Cell’s minimum access level: which causes SDCCH drop in
weak coverage area.
Unreasonable BSIC setting
Unreasonable 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 error
Congestion exists in adjacent cell


Sdcch drop rate

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