haditech668

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HUAWEI 2G PERFORMANCE MONITORING AND ANALYSIS
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Contents 1. Overview 2. 2G Performance
Monitoring and Analysis
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Document Information

• Document Version 1.0
• Issue Date September 8, 2010
• Author Christos Kyriazopoulos
• Document Owner Ville Salomaa
• SOFTWARE RELEASE GBSS9.0
• SCOPE
• 2G performance monitoring and analysis
• CONVENTION
• Raw counters are marked in BLUE
• Formulas are marked in GRAY
• Parameters are marked in RED
• MML commands are marked in GREEN

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Contents 1. Overview 2. 2G Performance
Monitoring and Analysis
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Overview
The purpose of this document is to describe the
BSS KPI performance monitoring and analysis of
problems that bad KPI values indicate. The
following analysis contains a list of the most
common KPIs used in Huawei networks. These KPIs
are monitored constantly. When the value of a KPI
goes below the defined threshold, then detailed
analysis should be performed in order to identify
the reasons of this deterioration. Once the
reasons are found, proper solutions will be
proposed and implemented. This document focuses
more in the analysis of failure causes rather
than the KPI monitoring itself. The most common
use cases for monitoring and analysis of bad
values are presented for 2G BSS.
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2G Performance Analysis Use Cases

• 2G Performance Analysis Use Cases
• CS
• High SDCCH Blocking
• High SDCCH Drop rate
• CSSR
• High TCH blocking
• High TCH Drop call rate
• High HO fail
• Low Coverage how to identify coverage problems
  (e.g. TA vs. cell radius, Rxlevel measurements,
  HO distribution)
• High Interference how to identify interference
  problem in cell (idle UL interference, Rxlevel
  Quality distributions, TA measurements)
• PS
• High Signaling Failures Before TBF Establishment
• High TBF Establishment Failures
• High TBF Drops
• Low Throughput (Um, Abis, PCU, Gb)

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General Methodology
General Methodology 1. Define BSS KPI class
required (Accessibility, Retainability, Mobility,
Resource Usage). 2. Define KPI per service
(Voice, Packet Service). 3. Define KPI
formulas. 4. Define target or guaranteed KPI
values. 5. Assess weekly average PLMN/BSC KPI
performance in order to identify KPIs below
target. 6. Assess BSC/Area level performance in
order to check if bad performance occurs across
network or only in specific areas. 7. Analyze bad
performing KPIs in cell level in order to
identify failure causes. (this point is the focus
of this document) 8. Use TopN cell approach to
identify the worst performers. Identify top 20
worst cells. 9. Look at failure distribution in
network topology (urban, rural, motorway, RNC
border, etc.). 10. Propose solution to improve
KPI value.
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Contents 1. Overview 2. 2G Performance
Monitoring and Analysis
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1. High SDCCH Blocking (1)

• - KPI formula
• SDCCH Congestion Rate (Overflow) (Failed SDCCH
  Seizures due to Busy SDCCH/SDCCH Seizure
  Requests)100
• Analysis process
• High SDCCH blocking is due to congestion on the
  SDCCH channel. Check what causes the high SDCCH
  usage. Then appropriate actions can be taken
• Check Call Setups
• - CELL_ESTB_IND_MOC_NONSMS_SD Number of Call
  Setup Indications for MOC on SDCCH
• - CELL_ESTB_IND_MTC_SD Number of Call Setup
  Indications for MTC on SDCCH
• Check amount of SMS. Check and verify with Core
  engineers SMS Center parameterization.
• - A3030B CELL_ESTB_IND_MOC_SMS_SD Number of
  Call Setup Indications for SMS on SDCCH
• - CA3340 CELL_Pt_to_Pt_SMS_SD Number of
  Point-to-Point Short Messages on SDCCH (includes
• ULDL)
• Check LAU/RAU requests
• - A300F CELL_CH_REQ_LOC_UPDATE Number of
  Channel Requests for Location Update
• - A3030F CELL_ESTB_IND_LOC_UPDATE_SD Number of
  Call Setup Indications on SDCCH for Location
  Update.

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1. High SDCCH Blocking (2)

• If high SCDDH usage is due to LAU then
• Check if the problem is caused by roamers that
  do not have access to the network, thus causing
  big amount of failed LAUs/RAUs.
• Check if cell is in LA border if yes, then we
  can increase CRH parameter value
• - CRH Cell Reselect Hysteresis Parameters (Cell
  reselection hysteresis. This is one of the
  parameters used for deciding whether to reselect
  cells in different location areas.)
• Check LA border planning. Verify LA borders by
  checking HO statistics between cells in LA
  border
• - H380CELLCELL_INCELL_HO_REQ Incoming
  Inter-Cell Handover Requests between 2 cells
• Check the value of T3212 if too low, increase
• - T3212 T3212 (This parameter specifies the
  length of the timer for periodic location
  update). Recommended value as high as possible,
  usually 4h.
• Check whether moving LA borders (if possible to
  move) could help relieving the congestion.
• Check the pattern of LAU requests. Check hours
  and duration of high number of such requests.
  Check whether the problem is constant throughout
  the day or it occurs only during 1 hour for
  example. If the problem occurs only on specific
  hour of day check if it is worth acting to solve
  it (costs vs. benefits).

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1. High SDCCH Blocking (3)

• Check if TCH Immediate Assignment is allowed
• - IMMASSEN TCH Immediate Assignment (Whether to
  allow immediate TCH assignment. If this parameter
  is set to YES, the BSC can assign a TCH
  immediately when there is no available SDCCH for
  a channel request.) Note It is not recommended
  to activate this in congested LA borders.
• Activate SDCCH dynamic conversion feature
  Dynamic SDCCH conversion can be triggered if the
  SDCCH resource is insufficient or the SDCCH
  allocation fails during the channel assignment
• - SDDYN SDCCH Dynamic Allocation Allowed
  (Whether to allow SDCCH dynamic allocation, that
  is, whether to allow dynamic conversion between
  TCHs and SDCCHs.)
• - IDLESDTHRES Idle SDCCH Threshold N1 (When the
  number of idle SDCCH channels in a cell is
  smaller than this parameter, the system searches
  for available TCHs and transforms them into SDCCH
  channels)
• - CELLMAXSD Cell SDCCH Channel Maximum (Maximum
  number of SDCCHs in the cell. Before converting a
  TCH into an SDCCH, the BSC compares the number of
  SDCCHs after the conversion in the cell with
  "Cell SDCCH Channel Maximum". If the number of
  SDCCHs after the conversion in the cell exceeds
  this parameter, the BSC does not convert the TCH
  into an SDCCH.)
• Add SDCCH/8 channel
• Add TRX
• Note for more details on SDCCH capacity
  optimisation check HUA_2G_Capacity_Optimization_v
  1.0.pptx
• document from Multivendor Team in IMS.

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2. High SDCCH Drop Rate (1)

• - KPI formula
• SDCCH Drop Rate (Call Drops on
  SDCCH/Successful SDCCH Seizures)100
• Analysis process
• Identify the route cause of SDCHH drops by
  checking the following counters. The total number
  of
• SDCCH drops is given by
• Call Drops on SDCCH Call Drops on Radio
  Interface (SDCCH)Call Drops due to No MRs from
  MS for a
• Long Time (SDCCH)Call Drops due to Abis
  Terrestrial Link Failure (SDCCH)Call Drops Due
  to
• Equipment Failure (SDCCH)Call Drops due to
  Forced Handover (SDCCH)
• Call Drops on Radio Interface (SDCCH) the drop
  is due to radio. Check for missing neighbours.
  Check radio environment/signal strength at drop
  points. Adjust antenna parameters appropriately
  to improve coverage if this is the problem. Check
  whether the drops are during handover. Check
  interference.
• Call Drops due to No MRs from MS for a Long Time
  (SDCCH) After seizing an SDCCH, the MS sends a
  measurement report to the BSC every 470 ms. When
  the BSC does not receive a measurement report
  within a certain period of time, the BSC sends a
  CLEAR REQUEST message to the MSC to release the
  call, and this counter is incremented by one.
  Check UL coverage and quality (interference).
  Check for possible MS problem.
• Call Drops due to Abis Terrestrial Link Failure
  (SDCCH) transmission problem on Abis. Check
  relative alarms.
• Call Drops Due to Equipment Failure (SDCCH) BSC
  hardware or software failure. Check alarms to
  discover the exact cause.

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2. High SDCCH Drop Rate (2)

• Call Drops due to Forced Handover (SDCCH) After
  an MS seizes a channel, if the system initiates a
  forced handover and the handover fails, the BSC
  may initiate a call release procedure. Check why
  the handover failed Timer expired? Check whether
  the emergency handover is due to preemption, or
  blocking of cell/TRX/channel.

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3. CSSR (1)

• - KPI formula
• BSS Call Setup Success Rate ((Immediate
  Assignment Success RateTCH Assignment Success
  Rate)(1-SDCCH Drop Rate))100
• The CSSR combines 3 other KPIs
• - Immediate Assignment Success Rate (Call
  Setup Indications (Circuit Service)/Channel
  Requests (Circuit Service))100
• - TCH Assignment Success Rate (Successful
  Assignments/Assignment Requests)100
• - SDCCH Drop Rate (Call Drops on
  SDCCH/Successful SDCCH Seizures)100
• Analysis process
• Each of the 3 component-KPIs will affect CSSR
• - Low Immediate Assignment Success Rate will
  decrease CSSR
• - Low TCH Assignment Success Rate will decrease
  CSSR
• - High SDCCH Drop Rate will decrease CSSR
• Examine at which point most of the failures
  appear by checking thoroughly the 3
  component-KPIs.
• Find out the corresponding failure causes for
  Immediate Assignment, Assignment and SDCCH Drops.

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3. CSSR (2)

• Low Immediate Assignment Success Rate
• Basic Immediate Assignment signalling procedure
• Fig.1 Successful Immediate Assignment Fig.2
  Failed Immediate Assignment
• A The BSC sends an IMM ASS REJ message due
  to no available channel

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3. CSSR (3)

• If Immediate Assignment failures are due to no
  channel available (point A in Figure 2), this
  means that there is SDCCH congestion. Refer to
  Case 1 of present document for handling.
• If Immediate Assignment failures are due to
  channel activation failure or channel activation
  timeout (points B, C in Figure 2) check
  hardware/software alarms.
• Low TCH Assignment Success Rate
• Basic Assignment signalling procedure

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3. CSSR (4)

• Check following counters to identify the reason
  for Assignment failure
• (1) Failures due to mismatch between the state
  machine of the BSC and the ASS REQ message or due
  to the abnormality of the ASS REQ message
• - A3129I CELL_ASS_FAIL_INVALID_STATE This
  counter provides the number of ASS FAIL messages
  sent by the BSC to the MSC when the BSC receives
  an ASS REQ message that is not expected by the
  internal state machine of the BSC (for example,
  the state machine is in release status).
• - A3129J CELL_ASS_FAIL_INVALID_MSG_CONTENTS
  This counter provides the number of ASS FAIL
  messages sent by the BSC to the MSC when the BSC
  receives an ASS REQ message but the ASS REQ
  message fails to be decoded (for example, an
  error occurs during the decoding of an IE, such
  as CHANNEL TYPE, CIC, or Layer 3 header
  information).
• - A3129E CELL_ASS_FAIL_NO_CIC This counter
  provides the number of ASS FAIL messages sent by
  the BSC to the MSC when the BSC receives an ASS
  REQ message that carries an unavailable A
  interface CIC.
• - A3129F CELL_ASS_FAIL_CIC_ALLOC This counter
  provides the number of ASS FAIL messages sent by
  the BSC to the MSC when the BSC receives an ASS
  REQ message that carries an A interface CIC that
  is already occupied by another call.

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3. CSSR (5)
(2) Failures due to abnormal radio resource
allocation - A312A CELL_ASS_FAIL_Frst_ASS_NO_CH
This counter provides the number of ASS FAIL
messages sent by the BSC to the MSC when the cell
does not have available channels and the directed
retry procedure fails to be initiated or the
directed retry is prohibited by the data
configuration in the first air interface
assignment procedure. - A312L
CELL_ASS_FAIL_RECONN_SUCC_ASS_NO_CH This counter
provides the number of ASS FAIL messages sent by
the BSC to the MSC when the cell does not have
available channels and the directed retry
procedure fails to be initiated or the directed
retry is prohibited by the data configuration in
the air interface assignment procedure except for
the first air interface assignment procedure. -
A312K CELL_ASS_FAIL_Frst_DR_NO_CH This counter
provides the number of ASS FAIL messages sent by
the BSC to the MSC when the cell does not have
available channels and the directed retry
procedure is successfully initiated but failed
due to no available channel in the first air
interface assignment procedure. - A312M
CELL_ASS_FAIL_RECONN_SUCC_DR_NO_CH This counter
provides the number of ASS FAIL messages sent by
the BSC to the MSC when the BSC attempts to make
a directed retry but the directed retry failed
because the target cell does not have available
channels in the air interface assignment
procedure except for the first air interface
assignment procedure.
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3. CSSR (6)
- A312F CELL_ASS_FAIL_NO_IDLE_ABIS This counter
provides the number of ASS FAIL messages sent by
the BSC to the MSC when the dynamic allocation of
Abis resources is enabled on the BSC but the
assignment fails due to no available Abis
resources. - A3129S CELL_ASS_FAIL_NO_SPEECH_VER
This counter provides the number of ASS FAIL
messages sent by the BSC to the MSC when the
assignment fails because the intersection between
the speech version set carried in the ASS REQ
message from the MSC and the speech version set
supported by the current cell of the MS does not
have available speech versions. (3) Failures
due to abnormal air interface access - A3129C
CELL_ASS_FAIL_Frst_ASS_EXP This counter provides
the number of ASS FAIL messages sent by the BSC
to the MSC when the timer for the BSC to wait for
an ASS CMP message expires after the BSC sends an
ASS CMD message to the MS in the first air
interface assignment procedure. - A3129P
CELL_ASS_FAIL_RECONN_SUCC_ASS_EXP This counter
provides the number of ASS FAIL messages sent by
the BSC to the MSC when the timer for the BSC to
wait for an ASS CMP message expires after the BSC
sends an ASS CMD message to the MS in the air
interface assignment procedure except for the
first air interface assignment procedure.
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3. CSSR (7)
- A3129O CELL_ASS_FAIL_Frst_DR_EXP This counter
provides the number of ASS FAIL messages sent by
the BSC to the MSC when the cell does not have
available channels and the directed retry
procedure is successfully initiated but failed
due to the expiry of the timer for waiting for an
HO CMP message in the first air interface
assignment procedure. - A3129Q
CELL_ASS_FAIL_RECONN_SUCC_DR_EXP This counter
provides the number of ASS FAIL messages sent by
the BSC to the MSC when the timer for waiting for
an ASS CMP message expires after the BSC sends an
HO CMD message to the MS in the air interface
assignment procedure except for the first air
interface assignment procedure. - A3129D
CELL_ASS_FAIL_RECONN_SUCC_ASS_RECONN_SUCC This
counter provides the number of ASS FAIL or RR
STATUS messages reported by the MS to the BSC
when the MS attempts but fails to access the new
channel and then successfully reconnects to the
old channel after receiving an ASS CMD
message. - A3129R CELL_ASS_FAIL_RECONN_SUCC_DR_R
ECONN_SUCC This counter provides the number of
HO FAIL or RR STATUS messages reported by the MS
to the BSC when the MS attempts but fails to
access the new channel and then successfully
reconnects to the old channel after receiving an
HO CMD message.
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3. CSSR (8)
(4) Failures due to the abnormality of
terrestrial resources or the call clearing
performed by the MSC. - A3129B
CELL_ASS_FAIL_Frst_APPLY_TRSL_FAIL This counter
provides the number of ASS FAIL messages sent by
the BSC to the MSC when the MS drops from the
connection to the air interface, or a circuit
fails to be obtained for the call, or the
obtained circuit is faulty during the circuit
connection of the BSC in the first air interface
assignment procedure. - A3129N
CELL_ASS_FAIL_RECONN_SUCC_APPLY_TRSL_FAIL This
counter provides the number of ASS FAIL messages
sent by the BSC to the MSC when the MS drops from
the connection to the air interface, or a circuit
fails to be obtained for the call, or the
obtained circuit is faulty during the circuit
connection of the BSC in the air interface
assignment procedure except for the first air
interface assignment procedure. - A3129G
CELL_ASS_FAIL_A_INTERF_FAIL This counter
provides the number of times that the BSC locally
releases the call when the BSC receives an SS7
link abnormality indication in the assignment
procedure. - A3129H CELL_ASS_FAIL_MSC_CLR_CMD
This counter provides the number of times that
the BSC releases the call after receiving a CLEAR
CMD message from the MSC in the assignment
procedure.
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3. CSSR (9)

• High SDCCH Drop Rate
• In case high SDCHH Drop Rate causes deterioration
  of CSSR, refer to Case 2 of present document for
  handling.
• Parameters that affect CSSR
• - RACHACCLEV RACH Min. Access Level
• This parameter affects the coverage area. If this
  parameter is set to a higher value, the actual
  coverage area of the network becomes small if
  this parameter is set to a lower value, call
  drops are likely to occur because of invalid
  access or too weak access signals, thus
  decreasing the success rate of BSS call setup.
• - RACHBUSYTHRED RACH Busy Threshold
• This parameter affects the coverage area. If this
  parameter is set to a higher value, the actual
  coverage area of the network becomes small if
  this parameter is set to a lower value, call
  drops are likely to occur because of invalid
  access or too weak access signals, thus
  decreasing the success rate of BSS call setup.
• - RANERRTHRED Random Access Error Threshold
• This parameter affects the coverage area. If this
  parameter is set to a higher value, the actual
  coverage area of the network becomes small if
  this parameter is set to a lower value, call
  drops are likely to occur because of invalid
  access or too weak access signals, thus
  decreasing the success rate of BSS call setup.
• - CIC No.
• The values of CICs must be consistent with that
  on the MSC side.

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3. CSSR (10)

• Network functions that affect CSSR
• - Directed retry
• When TCHs in a cell are insufficient, TCHs in
  other cells can be assigned through directed
  retry, thus increasing the BSS CSSR. By default,
  this function is enabled.
• - SDCCH dynamic adjustment
• When SDCCHs are insufficient, this function can
  be enabled to convert some TCHs into SDCCHs to
  increase the success rate of immediate
  assignment, thus increasing the BSS CSSR. By
  default, this function is enabled.
• - TCH reassignment
• When this function is enabled, the BSC initiates
  a re-assignment procedure after receiving the
  failure indication of the TCH assignment on the
  Um interface. This function can be used to
  increase the success
• rate of TCH assignment, thus increasing the BSS
  CSSR. By default, this function is enabled.
• - Flex Abis
• This function is implemented in the
  BSC6000V900R003 and later versions. This function
  enables dynamic assignment of Abis timeslots to
  more efficiently utilize the Abis link resources
  however, assignment may fail because of
  congestion on the Abis links. This function may
  decrease the BSS CSSR.

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4. High TCH Blocking (1)

• - KPI formula
• TCH Congestion Rate (Overflow) ((Failed TCH
  Seizures due to Busy TCH (Signaling
  Channel)Failed TCH Seizures due to Busy TCH
  (Traffic Channel)Failed TCH Seizures in TCH
  Handovers due to Busy TCH (Traffic
  Channel))/(TCH Seizure Requests (Signaling
  Channel)TCH Seizure Requests (Traffic
  Channel)TCH Seizure Requests in TCH Handovers
  (Traffic Channel)))100
• Analysis process
• High TCH blocking means congestion on the Traffic
  Channel there are not enough free TCHs to accept
  new service requests.
• Check cell traffic channel availability in order
  to verify that congestion is not due to
  availability issue. Check cell alarms.
• Check availability of neighboring sites. If
  neighboring cells are unavailable this will cause
  big amount of HOs directed to our current cell
  thus leading to congestion.
• Check cell traffic channel configuration. Check
  if all HR resources are in use before TCH
  congestion occurs. Verify that HR is enabled. In
  case AMR is supported by the operator, verify
  that is enabled.
• Load balancing between cells certain features
  can be activated to manage the traffic sharing
  between cells
• - Enable LO handover algorithm LoadHoEn Load
  Handover Support
• - Enable Directed Retry due to load DIRECTRYEN
  Directed Retry

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4. High TCH Blocking (2)

• Load balancing between cells
• - Concentric Cells check relative parameters so
  as to implement optimal traffic sharing between
  underlaid-overlaid cells.
• - Enhanced Dual Band Network check relative
  parameters so as to implement optimal traffic
  sharing between underlaid-overlaid cells.
• Check if additional capacity related features can
  be activated in the network in order to improve
  the utilisation of TCH resources
• - BCCH Dense Frequency Multiplexing enables the
  BCCHs to reuse frequencies more tightly to free
  more frequencies for non-BCCH TRXs, thus
  increasing the system capacity.
• TIGHTBCCHSWITCH TIGHT BCCH Switch (Whether to
  enable the BCCH aggressive frequency reuse
  algorithm)
• - Interference Based Channel Allocation (IBCA)
  The IBCA algorithm requires the BSC to estimate
  the C/I ratio of the new call in every channel
  assignment procedure it also requires the BSC to
  estimate the interference caused to the
  established calls on the network when an idle
  channel is assigned to a new call. In this way,
  the optimal channel, that is, the one that meets
  the C/I ratio requirement of the new call and
  causes the least interference to the established
  calls after being occupied, is assigned to the
  new call to alleviate the interference and ensure
  the full use of the frequency resources.
• IBCAALLOWED IBCA Allowed (Whether to enable
  the IBCA algorithm)
• - Flex MAIO BSC dynamically adjusts the MAIO
  according to the current interference level of a
  channel when assigning an MAIO to the channel .
• FLEXMAIO Start Flex MAIO Switch (Whether to
  enable the function of Flex Mobile Allocation
  Index Offset)

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4. High TCH Blocking (3)

• If congestion is still present although the
  previous described fine tuning and features
  activation, then
• - Check Interference in the network (C/I) check
  frequency plan
• - Check coverage maybe network layout should be
  changed in traffic hot spots
• - We can use TA distribution in order to
  identify traffic distribution among cells. In
  some cases overshooting can be detected, so we
  can check the possibility to reduce service area
  of the overshooting cell. Before doing so, we
  need, of course, to make sure that there is clear
  dominance in the area that we are going to shrink
  serving cells coverage.
• - Implement physical network changes where
  necessary and feasible tilt, azimuth, antenna
  type, etc.
• - Add TRX
• - Long term monitoring (e.g. one month) can be
  used to identify whether we have constant growth
  in traffic in a site and area close by. If
  traffic increases in area level and we have
  already high HR/AMR HR utilization then there are
  not too many other options than implement a new
  site.
• - Add Site
• Note for more details on TCH capacity
  optimisation check HUA_2G_Capacity_Optimization_v
  1.0.pptx
• document from Multivendor Team in IMS.

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5. High TCH Drop Call Rate (1)

• - KPI formula
• TCH Call Drop Rate (including handovers) (Call
  Drops on TCH/(Successful TCH Seizures
  (Signaling Channel)Successful TCH Seizures
  (Traffic Channel)Successful TCH Seizures in
  TCH handovers (Traffic Channel)))100
• Analysis process
• Identify the route cause of the call drops by
  checking the Call Drops on TCH counter
• Call Drops on Traffic Channel
• Call Drops on Radio Interface in Stable State
  (Traffic Channel)
• Call Drops on Radio Interface in Handover State
  (Traffic Channel)
• Call Drops due to No MRs from MS for a Long Time
  (Traffic Channel)
• Call Drops due to Abis Terrestrial Link Failure
  (Traffic Channel)
• Call Drops due to Equipment Failure (Traffic
  Channel)
• Call Drops due to Forced Handover (Traffic
  Channel)
• Call Drops Due to Loopback Start Failure
• Call Drops Due to Failures to Return to Normal
  Call from Loopback
• Call Drops on Radio Interface in Stable State
  (Traffic Channel) indicates RF issue. Check
  coverage at drop points check interference in
  the cell check for missing neighbours.
• Call Drops on Radio Interface in Handover State
  (Traffic Channel) drops during handover
  procedure check the handover failure counters to
  get more details for the handover failure cause.

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5. High TCH Drop Call Rate (2)

• Call Drops due to No MRs from MS for a Long Time
  (Traffic Channel) After seizing a TCH, the MS
  sends a measurement report to the BSC every 480
  ms. If the BSC does not receive any measurement
  report within a certain period, call drop occurs
  on the Um interface. Check UL coverage/UL
  interference at drop points. Check for possible
  MS problem.
• Call Drops due to Abis Terrestrial Link Failure
  (Traffic Channel) indicates Abis transmission
  problem. Check relative alarms.
• Call Drops due to Equipment Failure (Traffic
  Channel) indicates BSS hardware or software
  problem. Check relative alarms.
• Call Drops due to Forced Handover (Traffic
  Channel) After the MS seizes a traffic channel,
  the BSC initiates forced handover in the case of
  channel preemption, channel failure, or channel
  blocking. If the handover of the MS fails, the
  BSC releases the call.
• Call Drops Due to Loopback Start Failure After
  seizing a channel, the MS starts the local
  switching. This measurement provides the number
  of call drops due to the failure in starting the
  local switching caused by different reasons. The
  cause value can be Terrestrial Resource Request
  Failure, Failures on the BTS Side, or Timer
  Expired.
• Call Drops Due to Failures to Return to Normal
  Call from Loopback After a call is in the
  BSC/BTS local switch state, it incurs a handover.
  The local switch, however, cannot be continued
  because the target cell of the handover may not
  support local switch, the outgoing BSC handover
  fails, the TRX that carries the target channel of
  the handover may not support local switch, or the
  specified handover fails. The BSC attempts to
  restore the call to a normal one. The restoration
  may fail due to various reasons. If the
  restoration fails, the MS incurs call drop.

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5. High TCH Drop Call Rate (3)

• Parameters that affect TCH Drop Call Rate
• Check and tune appropriately, if needed, the
  values of the following parameters
• - RLT Radio Link Timeout recommended value 52
• - SAMULFRM SACCH Multi-Frames recommended
  value 32

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6. High HO fail (1)

• - KPI formula
• Handover Success Rate ((Successful Outgoing
  Internal Inter-Cell HandoverSuccessful
  Outgoing External Inter-Cell Handovers)/(Outgoin
  g Internal Inter-Cell Handover RequestsOutgoing
  External Inter-Cell Handover Requests))100
• Analysis process
• Identify the possible cause of the handover
  failures by checking the following counters
• A. Internal HO (intra-BSC)
• Basic intra-BSC inter-cell handover signalling
  procedure

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6. High HO fail (2)
The main causes for a failed outgoing internal
inter-cell handover include 1) Causes related
to resource allocation - No traffic channel is
available. - No speech version is available. -
No Abis resource is available. - The BSC fails
to obtain the terrestrial resources. 2) Causes
related to access on the Um interface - The MS
fails to access the new channel and then
reconnects to the old channel. - The timer for
the BSC to wait for an HO CMP message expires.
3) Abnormal causes - The BSC fails to activate
the allocated channel. - A fault occurs on the A
interface.
32
6. High HO fail (3)
(1) The following counters are measured when the
outgoing internal inter-cell handover fails
because of failed allocation of relevant
resources. - H312ACELL_INTRABSC_OUTCELL_HO_FAIL_
CONG no channel is available in the target cell
(congestion) - H312L CELL_INTRABSC_OUTCELL_HO_FA
IL_NO_IDLE_ABIS no circuit resource is available
on the Abis interface in the target cell when
the Abis dynamic allocation is enabled
(congestion on Abis) - H312HCELL_INTRABSC_OUTCELL
_HO_FAIL_NO_SPEECH_VER no proper speech version
is available in the target cell check speech
version configuration - H312BCELL_INTRABSC_OUTCEL
L_HO_FAIL_APPLY_TRSL_FAIL BSC fails to obtain
circuit resource when establishing the
terrestrial connection check A interface circuit
status check A interface alarms
33
6. High HO fail (4)
(2) The following counters provide the numbers of
failed internal intra-cell handovers when the MS
fails to access the new channel on the Um
interface. In the outgoing internal inter-cell
handover procedure, the BSC sends an HO CMD
message to the MS through the originating cell
and initiates a timer (T3103) to wait for a HO
CMP message. If the MS reconnects to the old
channel and sends a HO FAIL message on the old
channel before the timer expires, the following
counters are measured in the originating cell
based on the failure cause value -
H312DaCELL_INTRABSC_OUTCELL_HO_FAIL_RECONN_SUCC_M
S_RPT_ABNORM_REL_UNS Abnormal Release,
Unspecified - H312DbCELL_INTRABSC_OUTCELL_HO_FAIL
_RECONN_SUCC_MS_RPT_ABNORM_REL_CHN Abnormal
Release, Channel Unacceptable -
H312DcCELL_INTRABSC_OUTCELL_HO_FAIL_RECONN_SUCC_M
S_RPT_ABNORM_REL_EXP Abnormal Release, Timer
Expired - H312DdCELL_INTRABSC_OUTCELL_HO_FAIL_REC
ONN_SUCC_MS_RPT_ABNORM_REL_NO_ACT Abnormal
Release, No Activity on the Radio Path -
H312DeCELL_INTRABSC_OUTCELL_HO_FAIL_RECONN_SUCC_M
S_RPT_PREEMPT Preemptive Release -
H312DfCELL_INTRABSC_OUTCELL_HO_FAIL_RECONN_SUCC_M
S_RPT_HO_TA Timing Advance out of Range -
H312DgCELL_INTRABSC_OUTCELL_HO_FAIL_RECONN_SUCC_M
S_RPT_CH_MODE Channel Mode Unavailable -
H312DhCELL_INTRABSC_OUTCELL_HO_FAIL_RECONN_SUCC_M
S_RPT_FREQ Frequency Unavailable
34
6. High HO fail (5)
- H312DiCELL_INTRABSC_OUTCELL_HO_FAIL_RECONN_SUCC
_MS_RPT_C_CLR Call Already Cleared -
H312DjCELL_INTRABSC_OUTCELL_HO_FAIL_RECONN_SUCC_M
S_RPT_SEMANT Semantically Incorrect Message -
H312DkCELL_INTRABSC_OUTCELL_HO_FAIL_RECONN_SUCC_M
S_RPT_INV_MAN Invalid Mandatory Information -
H312DlCELL_INTRABSC_OUTCELL_HO_FAIL_RECONN_SUCC_M
S_RPT_M_T_NE Message Type Non-existent or Not
Implemented - H312DmCELL_INTRABSC_OUTCELL_HO_FAIL
_RECONN_SUCC_MS_RPT_M_T_NC Message Type Not
Compatible with Protocol State -
H312DnCELL_INTRABSC_OUTCELL_HO_FAIL_RECONN_SUCC_M
S_RPT_CONDIT Conditional IE Error -
H312DoCELL_INTRABSC_OUTCELL_HO_FAIL_RECONN_SUCC_M
S_RPT_NO_CA No Cell Allocation Available -
H312DpCELL_INTRABSC_OUTCELL_HO_FAIL_RECONN_SUCC_M
S_RPT_PROTOCL Protocol Error Unspecified -
H312DqCELL_INTRABSC_OUTCELL_HO_FAIL_RECONN_SUCC_M
S_RPT_OTHER Other Causes
35
6. High HO fail (6)
During the handover procedure excluding directed
retry, after the BSC successfully allocates and
activates the channel in the target cell, it
sends an HO CMD message to the MS and starts the
timer T3103 to wait for the HO CMP message. If
no HO CMP is received by the BSC before T3103
expires, the BSC releases the call. Then, the
specific one of the following counters is
measured in the target cell based on the type of
the target channel, that is, signalling channel
(SDCCH/TCHF/TCCH) or traffic channel
(TCHF/TCHH) - H3120CCELL_INTRABSC_OUTCELL_HO_FAI
L_EXP_SD_NOT_INCLUDE_DR - H3127CbCELL_INTRABSC_OU
TCELL_HO_FAIL_EXP_TCHF_SIG_NOT_INCLUDE_DR -
H3128CbCELL_INTRABSC_OUTCELL_HO_FAIL_EXP_TCHH_SIG
_NOT_INCLUDE_DR - H3127CaCELL_INTRABSC_OUTCELL_HO
_FAIL_EXP_TCHF_TRAF_NOT_INCLUDE_DR -
H3128CaCELL_INTRABSC_OUTCELL_HO_FAIL_EXP_TCHH_TRA
F_NOT_INCLUDE_DR In directed retry procedure,
the BSC sends an HO CMD message to the MS through
the originating cell and starts timer T3103 to
wait for an HO CMP message. If no HO CMP is
received by the BSC before T8 expires, the
following counter is measured -
H3121CCELL_INTRABSC_OUTCELL_HO_FAIL_EXP_DR Note
The counter CH312CCELL_INTRABSC_OUTCELL_HO_FAIL
_EXP is the sum of all the above counters, i.e.
the six counters above are sub-items of this
counter.
36
6. High HO fail (7)
(3) The following counters are measured when the
outgoing internal inter-cell handover fails
because of equipment faults. After the BSC
successfully performs channel allocation and
speech version confirmation in the target cell,
it sends a CH ACT message to the BTS for
activating the channel, and starts the
corresponding timer to wait for the response. If
the BSC receives a CH ACT NACK or no response
from the BTS before the timer expires, the
following counter is measured -
H312ICELL_INTRABSC_OUTCELL_HO_FAIL_CHACT_FAIL If
an outgoing internal intra-cell handover fails
because the BSC locally releases the call after
receiving an SS7 link abnormality indication,
the following counter is measured -
H312GCELL_INTRABSC_OUTCELL_HO_FAIL_A_INTERF_FAIL

37
6. High HO fail (8)
The main causes for a failed outgoing external
inter-cell handover include 1. The timer T7 for
the BSC to wait for a HO CMD message, after
having sent a HO RQD message, expires. 2. The
BSC receives a HO RQD REJ message from the
MSC. 3. The MS fails to access the new channel
and then reconnects to the old channel, sending
a HO FAIL message. 4. The timer T8 for the BSC
to wait for a CLEAR CMD message , after having
sent a HO CMD message, expires. 5. The BSC
receives a CLEAR CMD message from the MSC which
contains a failure handover cause. 6. An SS7
link failure occurs on the A interface
B. External HO (inter-BSC) Basic inter-BSC
inter-cell handover signalling procedure
38
6. High HO fail (9)
(1) During the outgoing external inter-cell
handover procedure, timer T7 is started after the
BSC sends the HO RQD to the MSC and waits for
the HO CMD command from the MSC. If no HO CMD is
received by the BSC before T7 expires, the BSC
re-sends the HO RQD message. The specific counter
provides the number of failed outgoing external
inter-cell handovers when the number of resending
times has exceeded the maximum
configuration. In the outgoing external
inter-cell handover (excluding directed retry)
procedure, the following counters are measured
when T7 expires based on the channel type -
H3320LCELL_INTERBSC_OUTCELL_HO_FAIL_T7_EXP_SD_NOT
_INCLUDE_DR - H3327LbCELL_INTERBSC_OUTCELL_HO_FAI
L_T7_EXP_TCHF_SIG - H3328LbCELL_INTERBSC_OUTCELL_
HO_FAIL_T7_EXP_TCHH_SIG - H3327LaCELL_INTERBSC_OU
TCELL_HO_FAIL_T7_EXP_TCHF_TRAF_CH -
H3328LaCELL_INTERBSC_OUTCELL_HO_FAIL_T7_EXP_TCHH_
TRAF_CH In the outgoing external inter-cell
handover (directed retry) procedure, the
following counter is measured -
H3321LCELL_INTERBSC_OUTCELL_HO_FAIL_T7_EXP_DR
39
6. High HO fail (10)
(2) The following counters provide the number of
times that the BSC terminates the outgoing
external inter- cell handover because it receives
an HO RQD REJ message from the MSC after sending
the HO RQD message to the MSC. -
H332KaCELL_INTERBSC_OUTCELL_HO_REQ_REJ_OM_INTERVE
NTION OM Intervention - H332KbCELL_INTERBSC_OUTC
ELL_HO_REQ_REJ_EQUIP_FAIL Equipment Failure -
H332KcCELL_INTERBSC_OUTCELL_HO_REQ_REJ_NO_RADIO_R
ES No Radio Resource Available -
H332KdCELL_INTERBSC_OUTCELL_HO_REQ_REJ_REQ_NO_TER
_RES Requested Terrestrial Resource
Unavailable - H332KeCELL_INTERBSC_OUTCELL_HO_REQ_
REJ_BSS_NOT_EQUIP BSS not Equipped -
H332KfCELL_INTERBSC_OUTCELL_HO_REQ_REJ_INVALID_CE
LL Invalid Cell - H332KgCELL_INTERBSC_OUTCELL_HO
_REQ_REJ_REQ_TRANS_NO_ADAPT Requested
Transcoding/Rate Adaption Unavailable -
H332KhCELL_INTERBSC_OUTCELL_HO_REQ_REJ_CIRCUIT_PO
OL_MISMATCH Circuit Pool Mismatch -
H332KiCELL_INTERBSC_OUTCELL_HO_REQ_REJ_REQ_NO_SV
Requested Speech Version Unavailable -
H332KjCELL_INTERBSC_OUTCELL_HO_REQ_REJ_CIPH_ALG_N
OT_SUPPORT Ciphering Algorithm not Supported -
H332KkCELL_INTERBSC_OUTCELL_HO_REQ_REJ_TER_CIR_AL
LOC Terrestrial Circuit Already Allocated -
H332KlCELL_INTERBSC_OUTCELL_HO_REQ_REJ_INVALID_MS
G Invalid Message - H332KmCELL_INTERBSC_OUTCELL_
HO_REQ_REJ_PROTOCOL_ERR Protocol Error between
BSS and MSC - H332KnCELL_INTERBSC_OUTCELL_HO_REQ
_REJ_OTHER Other Causes
40
6. High HO fail (11)
(3) In the outgoing external inter-cell handover
procedure, the BSC sends a HO CMD message to the
MS through the originating cell and initiates
timer T8 to wait for a CLEAR CMD message from the
MSC which will indicate Successful Handover. If
the MS reconnects to the old channel and sends an
HO FAIL message on the old channel before T8
expires, the specific one of the following
counters is measured in the target cell based on
the cause value in the HO FAIL message. -
H332DaCELL_INTERBSC_OUTCELL_HO_FAIL_RECONN_SUCC_M
S_RPT_ABNORM_REL_UNS Abnormal Release,
Unspecified - H332DbCELL_INTERBSC_OUTCELL_HO_FAIL
_RECONN_SUCC_MS_RPT_ABNORM_REL_CHN Abnormal
Release, Channel Unacceptable -
H332DcCELL_INTERBSC_OUTCELL_HO_FAIL_RECONN_SUCC_M
S_RPT_ABNORM_REL_EXP Abnormal Release, Timer
Expired - H332DdCELL_INTERBSC_OUTCELL_HO_FAIL_REC
ONN_SUCC_MS_RPT_ABNORM_REL_NO_ACT No Activity
on the Radio Path - H332DeCELL_INTERBSC_OUTCELL_H
O_FAIL_RECONN_SUCC_MS_RPT_PREEMPT Preemptive
Release - H332DfCELL_INTERBSC_OUTCELL_HO_FAIL_RE
CONN_SUCC_MS_RPT_HO_TA Timing Advance out of
Range - H332DgCELL_INTERBSC_OUTCELL_HO_FAIL_RECON
N_SUCC_MS_RPT_CH_MODE Channel Mode
Unavailable - H332DhCELL_INTERBSC_OUTCELL_HO_FAIL
_RECONN_SUCC_MS_RPT_FREQ Frequency
Unavailable - H332DiCELL_INTERBSC_OUTCELL_HO_FAI
L_RECONN_SUCC_MS_RPT_CALL_CLR Call Already
Cleared
41
6. High HO fail (12)
- H332DjCELL_INTERBSC_OUTCELL_HO_FAIL_RECONN_SUCC
_MS_RPT_SEMANT Semantically Incorrect Message -
H332DkCELL_INTERBSC_OUTCELL_HO_FAIL_RECONN_SUCC_M
S_RPT_INVALID_MAN Invalid Mandatory
Information - H332DlCELL_INTERBSC_OUTCELL_HO_FAIL
_RECONN_SUCC_MS_RPT_MSG_TYPE_NEXISTENT Message
Type Non-existent or Not Implemented -
H332DmCELL_INTERBSC_OUTCELL_HO_FAIL_RECONN_SUCC_M
S_RPT_MSG_TYPE_NOT_CO MPATIBLE Message Type Not
Compatible with Protocol State -
H332DnCELL_INTERBSC_OUTCELL_HO_FAIL_RECONN_SUCC_M
S_RPT_CONDIT Conditional IE Error -
H332DoCELL_INTERBSC_OUTCELL_HO_FAIL_RECONN_SUCC_M
S_RPT_NO_CA No Cell Allocation Available -
H332DpCELL_INTERBSC_OUTCELL_HO_FAIL_RECONN_SUCC_M
S_RPT_PROTOCL Protocol Error Unspecified -
H332DqCELL_INTERBSC_OUTCELL_HO_FAIL_RECONN_SUCC_M
S_RPT_OTHER Other Causes
42
6. High HO fail (13)
(4) In the outgoing external inter-cell handover
procedure, after sending the HO CMD message to
the MS, the BSC starts the timer T8 to wait for
the CLEAR CMD message from the MSC. The specific
counter provides the number of times that the
BSC terminates the handover due to the expiration
of T8. In the outgoing external inter-cell
handover (excluding directed retry) procedure,
the following counters are measured when T8
expires based on the channel type -
H3320CCELL_INTERBSC_OUTCELL_HO_FAIL_T8_EXP_SD_NOT
_INCLUDE_DR - H3327CbCELL_INTERBSC_OUTCELL_HO_FAI
L_T8_EXP_TCHF_SIG - H3328CbCELL_INTERBSC_OUTCELL_
HO_FAIL_T8_EXP_TCHH_SIG - H3327CaCELL_INTERBSC_OU
TCELL_HO_FAIL_T8_EXP_TCHF_TRAF_CH -
H3328CaCELL_INTERBSC_OUTCELL_HO_FAIL_T8_EXP_TCHH_
TRAF_CH In the outgoing external inter-cell
handover (directed retry) procedure, the
following counter is measured -
H3321CCELL_INTERBSC_OUTCELL_HO_FAIL_T8_EXP_DR N
ote The counter CH332CCELL_INTERBSC_OUTCELL_HO_F
AIL_T8_EXP is the sum of all the above counters,
i.e. the six counters above are sub-items of this
counter.
43
6. High HO fail (14)
(5) The following counters provides the number of
times that the BSC terminates the outgoing
external inter- cell handover because the BSC
receives a CLEAR CMD message from the MSC and the
cause value carried in the message is not
Handover successful. - H332HaCELL_INTERBSC_OUTCE
LL_HO_FAIL_MSC_CLR_RADIO_INTF_MSG_FAIL Radio
Interface Message Failure - H332HbCELL_INTERBSC_
OUTCELL_HO_FAIL_MSC_CLR_RADIO_INTF_FAIL Radio
Interface Failure - H332HcCELL_INTERBSC_OUTCELL_H
O_FAIL_MSC_CLR_OM_INTERVENTION OM Intervention -
H332HdCELL_INTERBSC_OUTCELL_HO_FAIL_MSC_CLR_EQUIP
_FAIL Equipment Failure - H332HeCELL_INTERBSC_OU
TCELL_HO_FAIL_MSC_CLR_PREEMPTION Preemption -
H332HfCELL_INTERBSC_OUTCELL_HO_FAIL_MSC_CLR_INVAL
ID_MSG Invalid Message - H332HgCELL_INTERBSC_OUT
CELL_HO_FAIL_MSC_CLR_PROTOCOL_ERR Protocol Error
between BSS and MSC - H332HhCELL_INTERBSC_OUTCEL
L_HO_FAIL_MSC_CLR_OTHER Other Causes (6) The
following counter provides the number of failed
outgoing external inter-cell handovers when the
BSC detects an SS7 link failure on the A
interface and releases the call -
H332GCELL_INTERBSC_OUTCELL_HO_FAIL_MSC_CLR_A_INTF
_FAIL
44
6. High HO fail (15)

• Check interference in source and target cells.
  High interference can cause handover failure.
• Check whether ping-pong handover occurs due to no
  dominant server in the area. Ping-pong may lead
  to HO failures.
• Parameters that affect HO Success Rate
• - T3103A Timer started after the BSC delivers a
  HANDOVER COMMAND in an intra-BSC inter-cell
• handover. If the BSC receives a HANDOVER COMPLETE
  message before this timer expires, the timer
• stops. If this timer expires, the BSC considers
  the handover as failed. Recommended value 10000
  ms
• - T7 Timer is started after the BSC sends the HO
  RQD to the MSC and waits for the HO CMD command
• from the MSC in an inter-BSC inter-cell handover
  procedure. Recommended value 10000 ms
• - T8 After sending the HO CMD message to the MS,
  the BSC starts this timer to wait for the CLEAR
  CMD
• message from the MSC in an inter-BSC inter-cell
  handover procedure. Recommended value 10000 ms

45
7. Low Coverage (1)

• TA measurements vs. cell radius
• The following counters provide TA distribution
  per TRX in the cell. The measurements can be
  checked
• versus cell radius to identify possible coverage
  problems.
• - S4400ATRX_MR_NUM_BY_TA_0
• - S4401ATRX_MR_NUM_BY_TA_1
• - S4402ATRX_MR_NUM_BY_TA_2
• - S4403ATRX_MR_NUM_BY_TA_3
• - S4404ATRX_MR_NUM_BY_TA_4
• - S4405ATRX_MR_NUM_BY_TA_5
• - S4406ATRX_MR_NUM_BY_TA_6
• - S4407ATRX_MR_NUM_BY_TA_7
• - S4408ATRX_MR_NUM_BY_TA_8
• - S4409ATRX_MR_NUM_BY_TA_9
• - S4410ATRX_MR_NUM_BY_TA_10
• - S4411ATRX_MR_NUM_BY_TA_11
• - S4412ATRX_MR_NUM_BY_TA_12
• - S4413ATRX_MR_NUM_BY_TA_13

- S4420ATRX_MR_NUM_BY_TA_20 - S4421ATRX_MR_NUM_B
Y_TA_21 - S4422ATRX_MR_NUM_BY_TA_22 -
S4423ATRX_MR_NUM_BY_TA_23 - S4424ATRX_MR_NUM_BY_
TA_24 - S4425ATRX_MR_NUM_BY_TA_25 -
S4426ATRX_MR_NUM_BY_TA_26 - S4427ATRX_MR_NUM_BY_
TA_27 - S4428ATRX_MR_NUM_BY_TA_28 -
S4429ATRX_MR_NUM_BY_TA_29 - S4430ATRX_MR_NUM_BY_
TA_30_TO_31 - S4432ATRX_MR_NUM_BY_TA_32_TO_33 -
S4434ATRX_MR_NUM_BY_TA_34_TO_35 -
S4436ATRX_MR_NUM_BY_TA_36_TO_37 -
S4438ATRX_MR_NUM_BY_TA_38_TO_39 -
S4440ATRX_MR_NUM_BY_TA_40_TO_44 -
S4445ATRX_MR_NUM_BY_TA_45_TO_49 -
S4450ATRX_MR_NUM_BY_TA_50_TO_54 -
S4455ATRX_MR_NUM_BY_TA_55_TO_63 -
S4463ATRX_MR_NUM_BY_TA_GT_63
46
7. Low Coverage (2)

• Rxlevel Rxquality measurements
• BSC receives reports that contain the uplink and
  downlink receive level rank and the uplink and
  downlink
• receive quality rank.
• - The receive level ranges from rank 0 to rank 7.
  Each rank corresponds to a receive level range.
• - The receive quality ranges from rank 0 to rank
  7. Each rank corresponds to a bit error rate
  range.

Receive Level Rank Receive Level (dBm)
0 -100
1 (-100,-95
2 (-95,-90
3 (-90,-85
4 (-85,-80
5 (-80,-75
6 (-75,-70
7 gt -70
Receive Quality Rank Bit Error Rate
0 lt 0.2
1 0.2-0.4
2 0.4 -0.8
3 0.8-1.6
4 1.6-3.2
5 3.2-6.4
6 6.4-12.8
7 gt 12.8
47
7. Low Coverage (3)

• TCHF Receive Level Measurement per TRX provides
  the number of measurement reports from the
• TCHF that contain receive level rank and receive
  quality rank. TCHF receive level and quality
  measurements
• for UL and DL are given by following counters
• - S4100ATRX_FR_UP_LEV_0_RX_QLTY_0
• - S4101ATRX_FR_UP_LEV_0_RX_QLTY_1
• - S4102ATRX_FR_UP_LEV_0_RX_QLTY_2
• ...
• SaaaaaTRX_FR_UP_LEV_x_RX_QLTY_y
• where aaaaacounter ID, xreceive level rank
  (07), yreceive quality rank (07)
• TCHH Receive Level Measurement per TRX refers to
  the measurement of the sampled receive level
• ranks and receive quality ranks in the MRs on the
  TCHH. TCHH receive level and quality measurements
  for
• UL and DL are given by following counters
• - S4100CTRX_HR_UP_LEV_0_RX_QLTY_0
• - S4101CTRX_HR_UP_LEV_0_RX_QLTY_1

- S4100BTRX_FR_DOWN_LEV_0_RX_QLTY_0 -
S4101BTRX_FR_DOWN_LEV_0_RX_QLTY_1 -
S4102BTRX_FR_DOWN_LEV_0_RX_QLTY_2
.. SaaaaaTRX_FR_UP_LEV_x_RX_QLTY_y
- S4100DTRX_HR_DOWN_LEV_0_RX_QLTY_0 -
S4101DTRX_HR_DOWN_LEV_0_RX_QLTY_1 -
S4102DTRX_HR_DOWN_LEV_0_RX_QLTY_2
SaaaaaTRX_FR_UP_LEV_x_RX_QLTY_y
48
8. High Interference (1)

• Idle UL Interference
• The interference band is the uplink interference
  level of a channel reported by the BTS to the BSC
  in the RF RESOURCE INDICATION message when the
  channel is idle. There are five levels of
  interference bands. The threshold of each
  interference band can be configured
• Higher rank suggests higher interference level.

Parameter ID Interference Band Recommended Value (dBm)
INTERFTHRES1 1 -105
INTERFTHRES2 2 -98
INTERFTHRES3 3 -92
INTERFTHRES4 4 -87
INTERFTHRES5 5 -85
49
8. High Interference (2)

• The following counters provide the average number
  of idle channels (TCHF, TCHH, or SDCCH) whose
• interference level are in each interference band
  (1-5) per granularity period.
• - AS4200ATRX_CH_IN_INTFR1_AVR_NUM_SD
• - AS4200BTRX_CH_IN_INTFR2_AVR_NUM_SD
• - AS4200CTRX_CH_IN_INTFR3_AVR_NUM_SD
• - AS4200DTRX_CH_IN_INTFR4_AVR_NUM_SD
• - AS4200ETRX_CH_IN_INTFR5_AVR_NUM_SD
• - AS4207ATRX_CH_IN_INTFR1_AVR_NUM_FR
• - AS4207BTRX_CH_IN_INTFR2_AVR_NUM_FR
• - AS4207CTRX_CH_IN_INTFR3_AVR_NUM_FR
• - AS4207DTRX_CH_IN_INTFR4_AVR_NUM_FR
• - AS4207ETRX_CH_IN_INTFR5_AVR_NUM_FR
• - AS4208ATRX_CH_IN_INTFR1_AVR_NUM_HR
• - AS4208BTRX_CH_IN_INTFR2_AVR_NUM_HR
• - AS4208CTRX_CH_IN_INTFR3_AVR_NUM_HR
• - AS4208DTRX_CH_IN_INTFR4_AVR_NUM_HR
• - AS4208ETRX_CH_IN_INTFR5_AVR_NUM_HR

50
9. High Signalling Failures Before TBF
Establishment (1)

• - KPI formula
• Success Rate of Random Access (Packet Service)
  A301HCELL_IMM_ASS_CMD_PS/A300HCELL_CH_REQ_PAC
  KET_CALL
• AGCH Blocking (L3188ACELL_DEL_IND/Channel
  Requests (all reasons))100
• Paging Overload Rate PS (PACKET CCCH LOAD IND
  Messages Sent on Abis Interface)/(Delivered
  Paging Messages for PS Service)100
• Analysis process
• High signalling failures before TBF establishment
  refers to failures on the CCCH. During one-phase
  access or two-phase access on the CCCH, the MS
  fails to proceed to TBF establishment process due
  to failures on the CCCH channel AGCH or PCH. The
  failures most likely will be due to CCCH
  congestion.
• Check the above KPIs to identify congestion on
  the AGCH or PCH.
• Check relative alarms on the BSC/BTS in order to
  locate any hardware/software fault.
• If blocking is the problem, proceed to the
  following steps in order to relieve congestion on
  the CCCH.
• Note For more details on CCCH capacity
  optimisation refer to HUA_2G_Capacity_Optimizatio
  n_v1.0.ppt
• document from Multivendor team in IMS.

51
9. High Signalling Failures Before TBF
Establishment (2)

• Check the values of following parameters
• - BSAGBLKSRES Blocks Reserved for AGCH. Value
  range 0-7. Recommended 2
• - BSPAMFRAMS Multi-Frames in a Cycle on the
  Paging CH. Value range 2-9. Value depends on
  paging load. Increase value when paging load
  increases. Value should be kept as small as
  possible.
• - PAGTIMES Paging Times. Value range 1-8 (For
  the BTS, this parameter is used to determine
  paging
• retransmissions. This parameter and the number
  of paging times configured in the MSC determine
  the number of paging retransmissions.)
• Check if Flow Control feature is enabled.
  Recommendation is that Flow Control is always
  enabled. Flow Control, controls the arrival of
  paging messages on the A interface (MSC-BSC) and
  on the LAPD links (BSC-BTS).
• Check volume of PS pagings (A331CELL_PAGES_PS
  Delivered Paging Messages for PS Service). If too
  high then check if PCCCH is configured. If PCCCH
  is configured then packet pages can be
  transmitted through PPCH, thus reducing PCH load.
• CS pages can also be transmitted through packet
  control channels (PACCH or PPCH). For this to
  work, Gs interface needs to be configured between
  SGSN-MSC. Also Network Mode of Operation should
  be set to 1.
• - NMO Network Operation Mode
• Check Location Area re-size might be required
  (make smaller).
• Consider splitting cells in the paging overload
  area. This will grow CCCH capacity.
• Add CCCH capacity (Extended BCCH).

52
9. High Signalling Failures Before TBF
Establishment (3)
Packet access on the CCCH signalling
procedure Fig.1 One-phase
packet access on the uplink CCCH
Fig.2 Two-phase packet access on the uplink CCCH
53
10. High TBF Establishment Failures (1)

• - KPI formula
• Uplink Assignment Success Rate ((Number of
  Successful Uplink GPRS TBF EstablishmentsNumber
  of Successful Uplink EGPRS TBF
  Establishments)/(Number of Uplink GPRS TBF
  Establishment AttemptsNumber of Uplink EGPRS
  TBF Establishment Attempts))100
• Downlink Assignment Success Rate ((Number of
  Successful Downlink GPRS TBF EstablishmentsNumb
  er of Successful Downlink EGPRS TBF
  Establishments)/(Number of Downlink GPRS TBF
  Establishment AttemptsNumber of Downlink EGPRS
  TBF Establishment Attempts))100
• Analysis process
• Identify the possible cause of the TBF
  establishment failures by checking the following
  counters
• A. UL GPRS TBF establishment failures
• - A9003UP_GPRS_TBF_ESTB_FAIL_NO_CHAN_RES number
  of failed uplink GPRS TBF establishments
• due to no channel available. Indicates congestion
  on the TCH refer to Case 4 of present document
  for
• handling suggestions.
• - A9004UP_GPRS_TBF_ESTB_FAIL_MS_NO_RESP number
  of failed uplink GPRS TBF establishments
• due to no response from MS. Indicates bad RF
  conditions in the cell. Check cell coverage and
  interference.
• - A9037UP_GPRS_TBF_ESTB_FAIL_SEND_ASSMSG_FAIL
  In dedicated mode, the BSS sends the
• resource assignment command to the MS over the
  DCCH if both the network and the MS support DTM
• (Dual Transfer Mode simultaneous support of
  CSPS service). If the resource assignment
  command is not
• sent successfully and the establishment of the
  uplink GPRS TBF thus fails, this counter is
  incremented by

54
10. High TBF Establishment Failures (2)
- A9038UP_GPRS_TBF_ESTB_FAIL_MS_RESP_ASS_FAILURE
In dedicated mode, the BSS sends the resource
assignment command to the MS over the DCCH if
both the network and the MS support DTM (Dual
Transfer Mode simultaneous support of CSPS
service). If the MS responds with the resource
assignment failure message and the establishment
of the uplink GPRS TBF thus fails, this counter
is incremented by one. - A9016UP_GPRS_TBF_ESTB_F
AIL_OTHER_CAUSE This measurement provides the
number of failed uplink GPRS TBF establishments
due to other causes in a granularity period. This
may happen because an exception or failure
occurs in the resource assignment or the overload
protection (flow control) is triggered. Check
BSS alarms in order to locate possible faults in
the equipment (h/w or s/w). B. UL EGPRS TBF
establishment failures - A9203UP_EGPRS_TBF_ESTB_
FAIL_NO_CHAN_RES number of failed uplink EGPRS
TBF establishments due to no channel available.
Indicates congestion on the TCH refer to Case 4
of present document for handling suggestions. -
A9204UP_EGPRS_TBF_ESTB_FAIL_MS_NO_RESP number
of failed uplink EGPRS TBF establishments due to
no response from MS. Indicates bad RF conditions
in the cell. Check cell coverage and
interference. - A9235UP_EGPRS_TBF_ESTB_FAIL_SEND_
ASSMSG_FAIL In dedicated mode, the BSS sends the
resource assignment command to the MS over the
DCCH if both the network and the MS support DTM.
If the resource assignment command is not sent
successfully and the establishment of the uplink
EGPRS TBF thus fails, this counter is
incremented by one. - A9236UP_EGPRS_TBF_ESTB_FAIL
_MS_RESP_ASS_FAILURE In dedicated mode, the BSS
sends the resource assignment command to the MS
over the DCCH if both the network and the MS
support DTM. If the MS responds with the
resource assignment failure message and the
establishment of the uplink EGPRS TBF thus
fails, this counter is incremented by one.
55
10. High TBF Establishment Failures (3)
- A9216UP_EGPRS_TBF_ESTB_FAIL_OTHER_CAUSE This
measurement provides the number of failed uplink
EGPRS TBF establishments due to other causes in a
granularity period. This may happen because an
exception or failure occurs in the resource
assignment or the overload protection (flow
control) is triggered. Check BSS alarms in order
to locate possible faults in the equipment (h/w
or s/w). C. DL GPRS TBF establishment
failures - A9103DOWN_GPRS_TBF_ESTB_FAIL_NO_CHAN_
RES number of failed downlink GPRS TBF
establishments due to no channel available.
Indicates congestion on the TCH refer to Case 4
of present document for handling suggestions. -
A9104DOWN_GPRS_TBF_ESTB_FAIL_MS_NO_RESP number
of failed downlink GPRS TBF establishments due
to no response from MS. Indicates bad RF
conditions in the cell. Check cell coverage and
interference. - A9135DOWN_GPRS_TBF_ESTB_FAIL_SEND
_ASSMSG_FAIL In dedicated mode, the BSS sends
the resource assignment command to the MS over
the DCCH if both the network and the MS support
DTM. If the resource assignment command is not
sent successfully and the establishment of the
downlink GPRS TBF thus fails, this counter is
incremented by one. - A9136DOWN_GPRS_TBF_ESTB_FAI
L_MS_RESP_ASS_FAILURE In dedicated mode, the BSS
sends the resource assignment command to the MS
over the DCCH if both the network and the MS
support DTM. If the MS responds with the
resource assignment failure message and the
establishment of the downlink GPRS TBF thus
fails, this counter is incremented by one. -
A9115DOWN_GPRS_TBF_ESTB_FAIL_OTHER_CAUSE This
measurement provides the number of failed
downlink GPRS TBF establishments due to other
causes in a granularity period. This may happen
because an exception or failure occurs in the
resource assignment or the overload protection
(flow control) is triggered. Check BSS alarms in
order to locate possible faults in the equipment
(h/w or s/w).
56
10. High TBF Establishment Failures (4)
D. DL EGPRS TBF establishment failures -
A9303DOWN_EGPRS_TBF_ESTB_FAIL_NO_CHAN_RES
number of failed downlink EGPRS TBF
establishments due to no channel available.
Indicates congestion on the TCH refer to Case 4
of present document for handling suggestions. -
A9304DOWN_EGPRS_TBF_ESTB_FAIL_MS_NO_RESP number
of failed downlink EGPRS TBF establishments due
to no response from MS. Indicates bad RF
conditions in the cell. Check cell coverage and
interference. - A9333DOWN_EGPRS_TBF_ESTB_FAIL_SEN
D_ASSMSG_FAIL In dedicated mode, the BSS sends
the resource assignment command to the MS over
the DCCH if both the network and the MS support
DTM. If the resource assignment command is not
sent successfully and the establishment of the
downlink EGPRS TBF thus fails, this counter is
incremented by one. - A9334DOWN_EGPRS_TBF_ESTB_FA
IL_MS_RESP_ASS_FAILURE In dedicated mode, the
BSS sends the resource assignment command to the
MS over the DCCH if both the network and the MS
support DTM. If the MS responds with the
resource assignment failure message and the
establishment of the downlink EGPRS TBF thus
fails, this counter is incremented by one. -
A9315DOWN_EGPRS_TBF_ESTB_FAIL_OTHER_CAUSE This
measurement provides the number of failed
downlink EGPRS TBF establishments due to other
causes in a granularity period. This may happen
because an exception or failure occurs in the
resource assignment or the overload protection
(flow control) is triggered. Check BSS alarms in
order to locate possible faults in the equipment
(h/w or s/w).
57
10. High TBF Establishment Failures (5)
Summary of corrective actions 1. If TBF
establishment failure is due to congestion in
TCH, refer to Case 4 of present document for
handling suggestions. In brief - Check
availability of current and neighbouring sites in
order to make sure that TCH congestion is not due
to unavailability issues. - Check FR/HR
parameterization (including AMR if enabled in the
network). Check usage of HR resources. - Check
Load balancing configuration between cells. - Add
TRX. 2. If TBF establishment failure is due to
poor RF quality, then - Check cell coverage and
interference. Refer to Cases 7, 8 of present
document for more details on how to check signal
strength and quality in Huawei 2G system. -
Adjust antenna parameters (tilt, azimuth) to
improve coverage and/or suppress interference in
the problematic areas. - Check antenna line
(feeders, jumpers) to identify faulty
connections. - Check BTS hardware (relative
alarms) to identify faulty TRXs. 3. If TBF
establishment failure is due to equipment fault,
check relative BSS alarms (hardware and software
alarms) in order to identify the faulty pa