1. Optimization: Introduction
Optimization: Introduction

2. Contents
 Global indicators
 Typical Radio Network Problem
 Coverage Problem
 Interference problem
 Unbalanced power budget problem
 Congestion problem
 Problems and responsible
parties
Optimization: Introduction

3. Global Indicators
4 stages of a call establishment, 2
stages (1&2) for location update :
1. Radio link establishment Phase
2. SDCCH Phase
then only “Circuit Switch call”
3. TCH assignment Phase
4. Alerting/Connect Phase
Optimization: Introduction

4. Mobile Originated Call (MOC)
MS BTS BSC MSC
Global CHANNEL REQUEST
(RACH)
CHANNEL REQUIRED
CHANNEL ACTIVATION (SDCCH)
CHANNEL ACTIVATION ACK
1. Radio Link
Indicators
IMMEDIATE ASSIGN COMMEND Establishment
IMMEDIATE ASSIGN
(AGCH)
Phase
SABM (L3 info)
(SDCCH) ESTABLISH IND (L3 info)
CR (Connection Request: L3
INFO)
UA (L3 info)
CC (Connection Complete)
(SDCCH)
LOCATION UPDATE REQUEST (IN CASE OF LU)
AUTHENTICATION REQUEST
AUTHENTICATION RESPONSE
2. SDCCH Phase CIPHERING MODE COMMAND
CIPHERING MODE COMPLETE
LOCATION UPDATE ACCEPT (IN CASE OF LU)
TMSI REALLOCATION COMPLETE (IN CASE OF LU)
SETUP
CALL PROCEEDING
ASSIGNMENT REQUEST
PHYSICAL CONTEXT REQUEST
PHYSICAL CONTEXT CONFIRM
CHANNEL ACTIVATION (TCH) TCH allocation
CHANNEL ALLOCATION ACK.
ASSIGNMENT COMMEND
(SDCCH)
SABM
ESTABLISH INDICATION
TCH UA (L3 info)
3. TCH Assignment Phase
ASSIGNMENT COMPLETE
ASSIGNMENT COMPLETE
ALERTING
CONNECT
4. Alert and Connect Phase CONNECT ACK.
CONVERSATION
Optimization: Introduction

5. Global Indicators
 Handover : Intracell HO
MS BTS BSC MSC
Measurement Report
MEASUREMENT RESULT
PHYSICAL CONTEXT REQUEST (old channel)
PHYSICAL CONTEXT CONFIRM (old channel)
CHANNEL ACTIVATION (new channel)
CHANNEL ACTIVATION ACK (new channel)
ASSIGNMENT CMD ASSIGNMENT COMMEND (old channel)
SABM (L3 info)
(SDCCH) ESTABLISH IND (new channel)
UA (L3 info)
(SDCCH)
ASSIGNMENT CMP ESTABLISH COMPLETE (new channel)
HANDOVER PERFORMED
RF CHANNEL RELEASE (old channel)
RF CHANNEL RELEASE ACK (old channel)
Optimization: Introduction

6. Global Indicators
 Handover : Internal HO
Serving Target
MS BSC MSC
Cell Cell
Meas. Report
MEASUREMENT RESULT
CHANNEL ACTIVATION
CHANNEL ACTIVATION ACK.
HO CMD HANDOVER COMMAND
HANDOVER ACCESS
HANDOVER DETECTION
PHYSICAL INFORMATION
SABM (L3 info)
UA (L3 info)
ESTABLISH INDICATION
HANDOVER COMPLETE HO CMP
HANDOVER PERFORMED
Optimization: Introduction

7. Global Indicators
 Handover : External HO
MS Serving Cell BSC MSC BSC Target Cell MS
MEAS_REPORT
MEAS_RESULT
HO_REQUIRED
CR (HO_REQUEST)
CC CHANNEL_ACTIVATION
CHANNEL_ACT_ACK
HO_REQUEST_ACK
HO_COMMAND (HO_COMMAND)
HO_ACCESS
HO_ACCESS
HO_DETECTION
HO_DETECTION
PHYSICAL_INFO
SABM (L3 info)
ESTABLISH_INDICATION UA (L3 info)
HO_COMPLETE
HO_COMPLETE
CLEAR_COMMAND
Cause: HO_SUCCESSFUL
Release of TCH
Optimization: Introduction

8. Global Indicators
Important indicators :
 SDCCH Congestion
 SDCCH Assignment Failure
 SDCCH Drop
 TCH Assignment Failure
 Call Drop
 Call Setup Success
 Call Success
 Outgoing Handover
 Incoming Handover
 Handover Causes Distribution (Better/
Level/Quality/MCHO/...)
Optimization: Introduction

9. Global Indicators
 SDCCH Congestion :
MS BTS BSC
CHANNEL REQUEST
CHANNEL REQUIRED
(RACH)
NO FREE SDCCH !!!
IMMEDIATE ASSIGN COMMEND
IMM. ASS. REJECT (OPTION)
(AGCH)
 MS will try to request again for a certain of times
 If still failures, it will
 Wait for a certain of time without reception of
immediate_assign message
 Try an automatic cell_reselection in case of
LU (no impact for subscriber)
 Notify a network error for call establishment
(call setup failure for subscriber)
Optimization: Introduction

10. Global Indicators
 SDCCH Congestion : Main causes
 Too much SDCCH “normal” traffic for cell
SDCCH design
 Logical cell design, extra TRX, new site
 “Common Transport Effect”
 Difficult to avoid for small cells
 LA border at crowded area
 Abnormal SDCCH traffic
 “phantom” channel requests
 Inadequate LAC design, causing too much
LU
 Redesign LAC
 Problem with neighbor cells belong to other
LAC
Optimization: Introduction

11. Global Indicators
 SDCCH RF Failure : main causes
MS BTS BSC MSC
CHANNEL REQUEST
CHANNEL REQUIRED
(RACH)
CHANNEL ACTIVATION (SDCCH)
CHANNEL ACTIVATION ACK
IMMEDIATE ASSIGN COMMEND
IMMEDIATE ASSIGN
(AGCH)
??? no message from MS
 Real radio problems
 Unbalanced power budget
 Bad coverage
 Interference
In case of radio failure, MS will retry as in case of
SDCCH congestion
Optimization: Introduction

12. Global Indicators
 SDCCH RF Failure : main causes
 “Phantom/Ghost/Spurious/Dummy...RACH”
 Channel request received but not sent : 3
causes
1. Noise decoding
2. Reception of channel request sent to a
neighbor cell
3. Reception of HO_ACCESS sent to a
neighbor cell
Optimization: Introduction

13. Global Indicators
 SDCCH RF Failure : main causes : Phantom RACH
1. Noise decoding
 GSM 05.05: “0.02% of RACH Frame can be
decoded without error without real input signal”
(this extra-load has no impact for the system)
 BCCH not combined: 156 phantom
RACCH/hour (or about 0.08 Erlang SDCCH)
 BCCH combined: 83 phantom RACH/hour
 During period with low real traffic (night), high
rate of phantom RACH
 No impact for subscriber
 But impact on indicator SDCCH RF access
failure
Optimization: Introduction

14. Global Indicators
 SDCCH RF Failure : main causes : Phantom RACH
1. Channel request sent to neighbor cell
 Subscriber is not impacted ( the real transaction
is performed elsewhere)
 But SDCCH RF access failure is impacted
 Usual radio planning rules are sufficient to avoid
the trouble (BSIC and BCCH frequency plan)
Optimization: Introduction

15. Global Indicators
 SDCCH RF Failure : main causes : Phantom RACH
 Channel request due to handover
 During HO, first message sent to target cell is
HO access which is an access burst like
channel_request
 If received on BCCH, can be understood as a
channel-request
This case is the most dangerous
 MS is sending usually a sequence of HO
Access message, every frame !!
 In some cases, this can create phantom RACH
if the frequency of TCH is co- or adjacent to one
of the interfered BCCH
 Can block very easily SDCCH
Optimization: Introduction

16. Global Indicators
 SDCCH Drop :
MS BTS BSC MSC
Radio connection loss
CONNECTION FAILURE INDICATION
(cause : radio link failure)
CLEAR REQUEST
(cause : radio interface failure)
 Loss of connection during SDCCH phase =
SDCCH Drop
 3 causes of SDCCH drop
 Radio problems when connected on SDCCH
 BSS problems (Transcoder and Internal BSS
problems)
 Call lost during an SDCCH HO (handover
failure without reversion to old channel)
Optimization: Introduction

17. Global Indicators
 TCH assign failure : Congestion
MS BTS BSC MSC
ASSIGNMNET REQUEST
no RTCH available on request cell
ASSIGNMENT FAILURE
cause No Radio Resources Available
 4 sub causes of congestion
 A: Queuing is not allowed
 B: Queue is full
 C: T11 expired
 D: RTCH requests is de-queued due to a
high priority (i.e. emergency call) request to
be queued
Optimization: Introduction

18. Global Indicators
 TCH assign failure : Radio
MS BTS BSC MSC
ASSIGNMENT REQUEST
PHYSICAL CONTEXT REQUEST
PHYSICAL CONTEXT CONFIRM
CHANNEL ACTIVATION (TCH) TCH allocation
CHANNEL ALLOCATION ACK.
ASSIGNMENT COMMEND
(SDCCH)
TCH
Radio Problem
ASSIGNMENT FAILURE
Radio interface failure
Optimization: Introduction

19. Global Indicators
 TCH assign failure : BSS
MS BTS BSC MSC
ASSIGNMENT REQUEST
PHYSICAL CONTEXT REQUEST
PHYSICAL CONTEXT CONFIRM
CHANNEL ACTIVATION (TCH) TCH allocation
CHANNEL ALLOCATION ACK.
ASSIGNMENT COMMEND
(SDCCH)
BSS Problem
Optimization: Introduction

20. Global Indicators
 TCH Drop : Radio
MS BTS BSC MSC
Alerting Connection Phase or Communication : at any time
Radio Problem CONNECTION FAILURE INDICATION
(cause : radio link failure)
CLEAR REQUEST
(cause : radio interface failure)
Optimization: Introduction

21. Global Indicators
 TCH Drop : BSS
MS BTS BSC MSC
Alerting Connection Phase or Communication : at any time
Radio Problem CONNECTION FAILURE INDICATION
(Remote transcoder failure)
CLEAR REQUEST
(Equipment failure)
 Transcoder reported problem
 Abis transmission Problem: Microwave,
Microwave antenna, fixed line problems.
 Problem on TC boards (hardware problem)
Optimization: Introduction

22. Global Indicators
 TCH Drop : BSS
MS BTS BSC MSC
Alerting Connection Phase or Communication : at any time
CLEAR REQUEST
BSS problem O&M intervention
Radio interface failure
 Other BSS problem (excluding TC)
 Hardware or software failures of BSC/BTS
Optimization: Introduction

23. Global Indicators
 TCH Drop : Handover
MS BTS BSC MSC
Alerting Connection Phase or Communication : at any time
HO failure without reversion CLEAR REQUEST
Radio interface message failure
 Call drop during handover
Optimization: Introduction

24. Global Indicators
 Intracell HO Failures
 Congestion
 Reversion to Old Channel (ROC)
 Drop Radio
 BSS problem
Optimization: Introduction

25. Global Indicators
 Intracell HO Failures : Congestion
Serving
MS BSC MSC
BTS
Measurement Report
MEASUREMENT RESULT
No Free TCH/SDCCH
 Intracell HO Failures : Drop
MS BTS BSC MSC
ASSIGNMENT CMD
ASSIGNMENT COMMAND (old channel)
Release of old and new channels
Optimization: Introduction

26. Global Indicators
 Intracell HO Failures : Reversion to Old Channel
Serving Serving
MS MSC
BTS BSC
ASSIGNMENT CMD ASSIGNMENT COMMEND (old channel)
SABM (new channel)
ESTABLISH IND (new channel)
UA (new channel)
X
SABM (new channel)
UA (new channel)
X
SABM (old channel)
ESTABLISH INDICATION (old channel)
UA (old channel)
ASSIGNMENT FAIL ASSIGNMNENT FAILURE
RF CHANNEL RELEASE (old channel)
RF CHANNEL RELEASE ACK (old channel)
Optimization: Introduction

27. Global Indicators
 Internal HO Failures : Reversion to Old Channel
Serving Target
MS BSC MSC
Cell Cell
HO CMD HANDOVER COMMAND
HANDOVER ACCESS
HANDOVER DETECTION
PHYSICAL INFORMATION
SABM (L3 info)
UA (L3 info)
ESTABLISH INDICATION
HANDOVER COMPLETE
X
SABM
ESTABLISH INDICATION
UM
HO FAILURE HO FAILURE
Release of new channel
Optimization: Introduction

28. Global Indicators
 Internal HO Failures : Drop
Serving Target
MS BSC MSC
Cell Cell
Meas. Report
MEASUREMENT RESULT
CHANNEL ACTIVATION
CHANNEL ACTIVATION ACK.
HO CMD HANDOVER COMMAND
Clear_request
Clear_command
Release of old and new TCH
Optimization: Introduction

29. Global Indicators
 External HO Failures : Congestion
MS Serving Cell BSC MSC BSC Target Cell MS
MEAS_REPORT
MEAS_RESULT
HO_REQUIRED
CR (HO_REQUEST)
HO_FAILURE
Cause: no radio resource available
HO_REQUIRED_REJECT
 External HO Failures : A int. Congestion
MS Serving Cell BSC MSC BSC Target Cell MS
MEAS_REPORT
MEAS_RESULT
HO_REQUIRED
CR (HO_REQUEST)
HO_FAILURE
Cause: terrestrial circuit already allocated
HO_REQUIRED_REJECT
Requested trerestrial resource unavailable
BSS not equipped
Optimization: Introduction

30. Global Indicators
 External HO Failures : Reversion to Old Channel
MS Serving Cell BSC MSC BSC Target Cell MS
MEAS_REPORT
MEAS_RESULT
HO_REQUIRED
CR (HO_REQUEST)
CC CHANNEL_ACTIVATION
CHANNEL_ACT_ACK
HO_REQUEST_ACK
HO_COMMAND (HO_COMMAND)
HO_ACCESS
X
HO_ACCESS
X
SABM
ESTABLISH_INDICATION
UA
HO_FAILURE(reversion to pld channel)
CLEAR_COMMAND
Radio interface fail:
Reversion to old channel Release connection
Optimization: Introduction

31. Global Indicators
 External HO Failures : Drop
MS Serving Cell BSC MSC BSC Target Cell MS
MEAS_REPORT
MEAS_RESULT
HO_REQUIRED
CR (HO_REQUEST)
CC CHANNEL_ACTIVATION
CHANNEL_ACT_ACK
HO_REQUEST_ACK
HO_COMMAND (HO_COMMAND)
HO_ACCESS
X
HO_ACCESS
X
SABM
X
SABM
X
SABM
X
CLEAR_COMMAND
Radio interface fail Release connection
Optimization: Introduction

32. Global Indicators
Important indicators : SDCCH Congestion Rate
 Definition: Rate of SDCCH not allocated during
radio link establishment procedure due to
congestion on Air interface
 Comment: Check SDCCH Erlang : if not critical,
SDCCH availability/allocation problem, or HO
access on a nearby cell side effect or
interference on the carrier handling SDCCH (the
last 2 can lead to high rate if Phantom RACH
Optimization: Introduction

33. Global Indicators
Important indicators : SDCCH Assign Failure Rate
 Definition: Rate of SDCCH seizure failed (BSS
problem, radio access problem) during radio link
establishment procedure over the total amount
of SDCCH seizure requests during radio link
establishment procedure
Optimization: Introduction

34. Global Indicators
Important indicators : SDCCH Drop Rate
 Definition: Rate of dropped SDCCH (SDCCH
is established for any transaction OC, TC,
LU, ...)
 Comment: Drop radio + Drop HO + Drop
BSS
Optimization: Introduction

35. Global Indicators
Important indicators : TCH Assign Failure/Congestion Rate
 Definition:
 TCH Assign Failure Rate: Rate of RTCH
seizure failed (BSS problem, radio access
problem) during normal assignment procedure
over the total amount or RTCH request for
normal assignment procedure
 TCH Assign Congestion Rate: Rate of RTCH
not allocated during normal assignment due to
congestion on Air interface
Optimization: Introduction

36. Global Indicators
Important indicators : Call Drop Rate
 Definition: Rate of dropped calls over the total
amount of calls with a successful end
 Comment:
 Drop BSS + Drop radio + Drop HO
 TCH drop occurring after successful
assignment but before speech connection are
considered as call drop even if from customer’s
point of view it is a call setup failure
Optimization: Introduction

37. Global Indicators
Important indicators : Call Setup Success Rate
 Definition: Rate of calls going until TCH successful
assignment, that is not interrupted by SDCCH drop
neither by assignment failures
 Comment:
 Subscriber : call not established at the first
attempt
Optimization: Introduction

38. Global Indicators
Important indicators : Call Success Rate (BSS view)
 Definition: Rate of calls going until normal release,
that is not interrupted by SDCCH drop neither by
assignment failures and neither by CALL DROP
 Comment:
 1 call success =
 1 call successfully established
 Without any call drop
Optimization: Introduction

39. Global Indicators
Important indicators : Outgoing Handover Success Rate
 Definition: Rate of outgoing external and internal
intercell TCH and SDCCH handover successes
over the total amount of outgoing external and
internal intercell TCH and SDCCH handover
required
Optimization: Introduction

40. Global Indicators
Important indicators : Incoming Handover Success Rate
 Definition: Rate of incoming external and internal
intercell TCH and SDCCH handover successes
over the total amount of outgoing external and
internal intercell TCH and SDCCH handover
requests
Optimization: Introduction

41. Global Indicators
Important indicators : Handover Cause Distribution
 Definition: Distribution of Handover requests by cause:
UL Qual, UL Lev, DL Qual, DL Lev, Better Cell, UL
Interference, DL Interference, Interband, Micro cells
HO, Concentric cell causes
Optimization: Introduction

42. Typical Radio Problems
i. Coverage Problem
ii. Interference problem
iii.Unbalanced power budget
problem
iv. Congestion problem
Optimization: Introduction

43. Typical Radio Problems
Several sources of information for
optimization
 QoS indicators
 Coverage predictions
 Customer complaints
 Drive tests
 Abis/A traces
 Other teams information (NSS statistics)
Optimization: Introduction

44. i. Coverage Problem
Bad coverage :
A network facing coverage problems has
bad RxLev. RxQual can be bad at the
same time.
Sometimes the RxLev can look OK on the
street (i.e. from drivetest) but coverage
inside the buildings can be poor due to
building losses. Building losses can
range from 10 to 30 dB or more.
Optimization: Introduction

45. i. Coverage Problem
 Indications :
 Customers complain about dropped calls
and/or “No Network”
 OMC QoS indicators
– TCH failure rate
– Call drop rate
– Low proportion of better cell HO
– High rate of DL & UL Level HO (possibly
also DL/UL quality HO)
 A interface indicators
– High rate of Clear Request message, cause
radio interface failure
 Drive Test
– Poor RxLev ( < -95 dBm)
Optimization: Introduction

46. i. Coverage Problem
 Investigation and Optimization :
 If actual coverage is not the one
predicted by planning tool
– Check antenna system (azimuth, crossed
sector?)
– Check prediction in the tool (EIRP, Clutter
Type, Obstructing building?). Most of the
time the prediction will be incorrect, as it is
only a computer simulation
– Increase or decrease antenna down-tilt
– Check BTS output power set in the OMC-R
(BS_TXPWR_MAX: should always be set
at 0)
Optimization: Introduction

47. i. Coverage Problem
 Investigation and Optimization :
 If actual coverage OK compared to
predicted ones
– Improve coverage by adding Macro site,
Microcell site (Border or Shadow areas), or
IBC site (In-building coverage).
– Use parameter setting ex. Bi-layer
Handover.
Optimization: Introduction

48. i. Coverage Problem
Example on thresholds :
 From Drive test or Abis Interface
 RxLev < -95 dBm
and
 RxQual > 4
Optimization: Introduction

49. ii. Interference Problem
Interference :
A network facing interferences
problems presents good RxLev
and bad RxQual in the same
time on some areas.
Optimization: Introduction

50. ii. Interference Problem
 Indications :
 Customers complain about bad speech
quality (noisy calls) and/or call drops
 OMC QoS indicators
– SDCCH/TCH Drop
– Low proportion of better cell HO
– High rate of DL/UL quality HO and
interference HO
– Low HO success rate
 A interface indicators
– High rate of Clear Request message, cause
radio interface failure
 Drive Test
– RxQual > 4 with RxLev > -85 dBm
Optimization: Introduction

51. ii. Interference Problem
Typical causes :
 GSM interferences
 Co-channel
 adjacent
 Non GSM Interference
 Other Mobile Network
 Other RF sources
Optimization: Introduction

52. ii. Interference Problem
Level
Co-channel interference :
 C/I = Carrier-to-interference ratio
 +12 dB is taken into account for +12 dB
Alcatel ( +9 dB according to GSM
standard) (i.e. interference can be
9  12 dB weaker than serving
cell to cause poor RxQual).
f(cell1)=f(cell2) Frequency
Optimization: Introduction

53. ii. Interference Problem
Co-channel interference :
 Indications
 Downlink and/or Uplink Interference
 High rate of quality handover, call drop, and
call setup failure
 Investigation
 Drive test analysis
 Lumpini: Co-channel checking
 Check prediction to verify which cell could be
causing the interference
 Frequency plan C/I < 12 dB
Optimization: Introduction

54. ii. Interference Problem
Co-channel interference :
 Optimization
 Antenna optimization
 Change frequency
 Reduce BTS power (not an option in TA
Orange network)
 Concentric cell
Optimization: Introduction

55. ii. Interference Problem
Co-channel interference: Optimization: Concentric cell
 Concept  Conclusion from Alcatel trial on
Orange’s network (Suburban
area)
 Concentric cell is difficult to
optimize, and hence is rarely
used in the network today.
Optimization: Introduction

56. ii. Interference Problem
Adjacent channel interference :
 C/A = Carrier-to-adjacent ratio
 -6 dB is taken into account for Alcatel ( -9 dB
according to GSM standard).
Level
f(cell1) f(cell2)
-6 dB
E.g.
f(cell1)= Ch.573
f(cell2)= Ch.574
f(cell2)=f(cell1)+1 Frequency
Optimization: Introduction

57. ii. Interference Problem
Adjacent channel interference :
 Indications
 Downlink and/or Uplink Interference
 High rate of quality handover, call drop, and call
failure
 Investigation
 Adjacent HO statistics (if they are defined as
neighbors). If they often handover, then adjacent
channel interference could be a problem.
 Drive test analysis
 Lumpini: Adjacent channel checking
 Cell coverage prediction
 Frequency plan C/I < -6 dB
Optimization: Introduction

58. ii. Interference Problem
Adjacent channel interference :
 Optimization
 Antenna optimization
 Change frequency
 Reduce BTS power (not an option in TA
Orange network)
 Concentric cell
Optimization: Introduction

59. ii. Interference Problem
Interference : Forced Directed Retry
 MS should connect to Cell_A, but no
TCH available.
 MS connects to Cell_B with forced
directed retry
 MS is emitting at high level (due to long
distance from Cell_B) Cell_B: Ch.573
 UL interference for Cell_C
 Cell_B is emitting at high level (if DL PC
is being used)
 DL interference at Cell_C
 MS is serving on the 2nd or 3rd best Cell_A: Ch.569
server: increases chances of Cell_C: Ch.572
interference problem (poor C/I & C/A as
“C” is lower)
Optimization: Introduction

60. ii. Interference Problem
Non GSM interference :
 Other mobile network
 Inter-modulation with GSM BTS/MS receiver
 Other RF interferers
 Radar
 Shop anti-theft mechanism
 Medical devices
 Other man-made radio transmission
 Illegal usage of GSM frequencies (e.g. illegal
imported devices, illegal usage of other
organization, ...)
 ...
Optimization: Introduction

61. iii. Unbalance power budget Problem
 A cell facing unbalanced power budget problems
presents a too high path-loss difference between
UL and DL (often DL>UL)
 Lower Rx diversity gain of cross polarized
antenna in rural area compared to dense area
 Crossed feeders
 Traffic not directly in boresight of antenna, where
cross-polar discrimination is lower
 Loose connectors
 Faulty antenna, feeder, TMA
 Rule : try to have delta as small as possible to
avoid access network possible only in 1 direction
(usually BTS->MS : OK and MS->BTS : NOK),
i.e. uplink limited
Optimization: Introduction

62. iii. Unbalance power budget Problem
 Indicators :
 OMC QoS indicators
– High ratio of Uplink level Handover cause
– Low incoming HO success rate
– DL level looks OK for HO, but UL is too weak
when HO is attempted
– Degradation of TCH failures and OC call drop
indicators
 A interface indicators
– High rate of Clear Request message, cause
radio interface failure
 O&M Alarms
– Voltage Standing Wave Ratio (VSWR)
– TMA
Optimization: Introduction

63. iii. Unbalance power budget Problem
 Investigation :
 Abis monitoring:
– ABS(delta Path loss) > 10
» Check if problem is occurring for 1 TRX or
all.
– ABS(delta path loss) = ABS(UL Path loss – DL
Path loss)
– UL Path loss = MS transmitted power –
measured received UL level
– DL Path loss = BTS transmitted power –
combiner loss – measured received DL level
– Large difference between uplink and downlink
level triggered HO.
 Use PM observation counter (in OMC-R)
– RT11
Optimization: Introduction

64. iii. Unbalance power budget Problem
 Optimization : This equipment
should be checked
 TRX types (MP, HP)
 Antennas or common RF components,
TMA (common to all TRX of the BTS)
 TRX RF cables, LNA
Optimization: Introduction

65. iv. TCH congestion Problem
TCH Congestion :
 TCH Congestion rate (TCH
Assignment Phase) is too high
(more than 2%)
 Rule : try to meet the offered
traffic (asked by users) by
providing the right number of
resources (TRX extension)
Optimization: Introduction

66. iv. TCH congestion Problem
 Indications :
 Customers complain about “Network busy”
 OMC QoS indicators
– High “TCH Congestion rate”, “RTCH
Assignment fail-Congestion”
– Low “incoming Intra/Inter BSC HO success
rate” (no TCH available)
– High “Directed Retry rate or Congestion
Relief (Motorola)” if activated
 A interface indicators: “BSS Congestion
failure in OC”
– High rate of Assignment Failure message,
No radio resource available
 Drive Test
– Handover to better cell is slow, or never
occurs
Optimization: Introduction

67. iv. TCH congestion Problem
 Optimization :
 Special events :
– Foreseeable: football match, important
meeting, Exhibition, etc.
» Add some extra TRXs
» Add special mobile BTSs (Cell on
Wheel)
» Activate HR (may not always be
possible due to BSC capacity
limitations)
– Not foreseeable: car crash on the
highway
Optimization: Introduction

68. iv. TCH congestion Problem
 Optimization :
 Daily periodic problems : At busy hour:
– Hardware solution :
» Add TRX(s)
» Concentric cell
» New site
» Optimize cell boundaries (i.e.
antenna optimization) to share
traffic with surrounding cells
Optimization: Introduction

69. iv. TCH congestion Problem
 Optimization :
 Daily periodic problems : At busy hour:
– Software solution :
» Directed Retry
» Traffic Handover
» Half Rate (Alcatel)
» Congestion Relief (Motorola)
» Flow control (Motorola)
Optimization: Introduction

70. Problems and responsible parties
 Coverage problem :
 If the measured RxLev does not
match the prediction
– Check the prediction, check
panoramic pictures for obstructions
– Field Operation team to check
physical configuration (tilt, azimuth,
antenna height...). Also check for
faults in the antenna system (VSWR,
sweep antennas, DTF test, etc.)
– If Field Operation find no problem,
antenna optimization may be required
(if necessary)
Optimization: Introduction

71. Problems and responsible parties
 Coverage problem :
 Ifthe field reality match the
prediction
– RF team to add new sites (tri-sector,
micro cellular, indoor cells) to improve
poor/no coverage area (Optimizer
requests for some new sites to RF
team regarding to the drive test result)
Optimization: Introduction

72. Problems and responsible parties
 Interference problem :
 Optimization team to identify the
interference source and request Spectrum
Management team to correct it in case of
internal source (new frequency planning...)
 Unbalanced power budget problem :
 Field Operation team to check the
impacted BTS (Antenna, TMA, RF cables,
LNA, diversity system...) according to
request from Optimizer.
Optimization: Introduction

73. Problems and responsible parties
 TCH Congestion problem :
 Regional
RF to request TRX
expansion.
Optimization: Introduction