Download - Part 3 optimization 3G
Part 3 :Optimization
Network Deployment Steps
Presentation / Author / Date
Using Reporting Suite 3G RAN Reports or MS Access KPI Queries
Weekly KPI( PLMN) < X %
No action needed
No
Yes
Yes
No
System Program (PLMN)
Weekly KPI (RNC) < X % ?
System Program (RNC)
Daily KPI (WCEL)
< X%
Identify Call failure phases of bad performing KPIs, for example CSSR
Identify failures root-causes and failure distribution of bad KPIs
Identify Top50 Worst Cells based on highest number of root causes failures
System Program (WCEL) Others 3G RAN Reports
Others 3G RAN Reports Yes
Mataching failure distribution into network topology
System Program (WCEL)
Solution Proposal
Mapinfo
High level PM data analysis and assessment
Presentation / Author / Date
PM Data analysis process
Traffic Monitoring
Principles of traffic monitoring - bottlenecks
Both interfaces and internal resources of WCDMA network should be monitored
User P
lane
RNCUE
WBTS
DNBAP
AAL2 or IP SIG
CNBAPPRACHFACH-c&u
DCH
Air Interface Iub Interface
User Plane
Iur Interface
IuCS Interface
User Plane
SS7 (RANAP)
IuPS Interface
User Plane
User Plane
SS7 (RANAP)
PCH
WSPResource
CodeCapacity
Throughput
Connectivity
Unit Load
DSP Usage
D-RNC
Principles of traffic monitoring - reactive / proactive
Reactive monitoring• Consider setup failure (already discussed in chapter 2)
• Daily BH analysis needed
Proactive monitoring• Consider amount of traffic
• Weekly analysis enough
Principles
Transmitted carrier power
Node B reporting
Total DL power
R99 power
HSDPA power
Received total wideband power
Code tree allocation
Channel element allocation
Iub transmission
RNC processing load
Number of users
Traffic Monitoring
Node B informs RNC about air interface load by the following messages
Common NBAP radio resource indication• Transmitted carrier power
• Total power R99 + HSDPA
• R99 power
• Received total wideband power • Total power R99 + HSUPA
• HSUPA power (calculated by Node B, not directly measured)
Dedicated NBAP measurement report• Power of each dedicated radio link
IuB
C - NBAP
D - NBAP
Node B RNC
Node B reporting
High total DL power
High pilot pollution
Otherwise
Total DL power - optimization flow
Check SHO parameter settings
Check adjacent cell interference
Neighbor analysis
High SHO overhead
Add second carrier
R99 power -
Number of radio resource indications falling into specific R99 power interval
The definition of the load target depends on the presence of HSDPA users• No HSDPA user present → static load target PtxTarget
• At least one HSDPA user present → dynamic load target PtxTargetPS
R99 power -
HSPA power
HSPA power includes• HS-PDSCH
• All HS-SCCH
• All HSUPA DL signaling channels (E-AGCH, E-RGCH, E-HICH)
DL power shared dynamically between R99 and HSDPA
Realized by dynamic load target for NRT R99 traffic PtxTargetPS
For RT R99 traffic still static load target PtxTarget
PtxTargetPS is adjusted between • Minimum load target PtxTargetPSMin (default 36 dBm)
• Maximum load target PtxTargetPSMax (default 40 dBm)
RNC checks periodically, whether adjustment of PtxTargetPS needed
Period defined by PtxTargetPSAdjustPeriod (default 5 RRI periods)
PtxTargetPSMin PtxTargetPS PtxTargetPSMax
HSDPA power - dynamic share with R99
HSDPA power - dynamic share with R99PtxTargetPS adjusted under the following conditions
1) HSDPA congestion• Too much total DL power present in cell
• PtxHighHSDPAPwr defines overload threshold for HSDPA cell (default 41 dBm)
2) DCH congestion• Too much R99 power present in cell
• The offset is fixed to 1 dB
PtxTotal ≥ PtxHighHSDPAPwr
PtxNonHSPA ≥ PtxTargetPS - Offset
HSDPA Congestion
HSDPA power - dynamic share with R99
HSDPA power congestion, ifPtxtotal ≥ PtxHighHSDPAPwr
PtxMax 43 dBm
PtxNC
PtxNRTPtxNonHSDPA
PtxTotal
PtxTargetPSMin-10..50; 0.1; 36 dBm
PtxTargetPSMax-10..50; 0.1; 40 dBm
PtxHighHSDPAPwr-10..50; 0.1; 41 dBm
PtxTargetPS
If actual load target PtxTargetPS > optimum load targetDecrease PtxTargetPS by PtxTargetPSStepDown (default 1 dB)
Optimum load target
HSDPA power - dynamic share with R99DCH Congestion
PtxMax 43 dBm
PtxNC
PtxNRTPtxNonHSDPA
PtxTargetPSMin
PtxTargetPSMax
PtxHighHSDPAPwr
DCH power congestion, if
PtxNonHSDPA ≥ PtxTargetPS - 1dBIf actual load target PtxTargetPS < optimum load targetIncrease PtxTargetPS by PtxTargetPSStepUp (default 1 dB)
PtxTotal
PtxTargetPS
Optimum load target
Noise rise due toreal traffic
Own cell load factor (throughput)
i-factor
PrxTargete.g. 4 dB above PrxNoise
RTWP sources
-108 dBmReceiver noise figure (e.g. 2 dB)
Thermal noise -108 dBm
-106 dBmIntermodulation out of band (e.g. 1 dB)
-105 dBmRTWP of empty cellMUST be equal PrxNoise
PrxOffsete.g. 1 dB above PrxTarget
High adjacent cell interference
Low adjacent cell interference
-101 dBm
-100 dBm
Total UL power - role of BTS commissioningRTWP measured by BTS at antenna connector
Then corrected due to• Feeder loss
• MHA gain
RTWPcorrected = RTWPmeasured + feeder loss – MHA gain
Corrected RTWP reported to RNC
With wrong settings wrong RTWP values reported
Previous example for 2 GHz range
Probably feeder loss underestimated → corrected RTWP underestimated
Total UL power
Close to -112 dBm
Often > -100 dBm
Total UL power - optimization flow
Check feeder loss / MHA gain commissioning setting
Check HW
Still below BTS receiver noise
Check
- High traffic density
- HW
- Intermodulation
SF=64
SF=32
SF=16
SF=8
SF=128
R99 code allocation - principlesCode resource required depends on type of radio bearer• Signaling SF 256 for 3.4 Kbit/s, SF 128 for 13.6 Kbit/s
• Voice HR SF 128 or SF 256
• Voice FR, 16K data SF 128
• 32K data SF 64
• 64K data SF 32
• 128K data SF 16
• 256K data, 384K data SF 8
Only 1 code per bearer allocated
Total blocking rate
Blocking rate for SF16
Blocking rate for SF8
R99 code allocation - blockingPractical example – single cell
Blocking per SF per hour
Very high blocking especially for SF8But still also for SF16 and sometimes even for SF32
R99 code allocation - re-arrangementCode tree quickly fragmented, if not re-arranged from time to time
Then few users of high SF (low data rate) block huge amount of resources for users of low SF (high data rate)
Re-arrangement performed• Periodically according CodeTreeOptTimer (default 1h) OR
• If code tree occupation > CodeTreeUsage (default 40%) OR
• If more than MaxCodeReleases consecutive releases of codes (default 40)
Blocking before re-arrangement Blocking after re-arrangement
1514131211109876543210………. ……….
1514131211109876543210 1514131211109876543210………. ……….
1514131211109876543210
HSDPA code allocation - principlesFor HSDPA fixed SF16
But several codes per bearer available• Minimum guarantee of 5 codes
• Maximum number set usually to 15 codes
• Code resource has to be shared with R99
SF=8
SF=4
SF=2
SF=1
SF=16
R99 + HSPA signaling CH Guarantee for HSDPA
Dynamically shared between R99 and HSDPA
Number of codes reserved for HSDPA can be adjusted dynamically in dependence on R99 traffic
Possible levels configured with parameter HSPDSCHCodeSet
16 bit parameter to enable / disable each possible level individually
HSDPA code allocation - dynamic share with R99
Examples
00000 00000 100000 = always 5 codes reserved (default)
11010 10100 100000 = number of reserved codes adjustable (5, 8, 10, 12, 14 or 15 codes, recommended)
0-4 codes always disabled11-15 codes
6-10 codes
Upgrade
RNC checks periodically, whether more codes can be reserved for HSDPA
Requirements for upgrade• Free adjacent codes to go to next higher level defined by HSPDSCHCodeSet
• After upgrade still enough codes with SF128 available for R99 (at least HSPDSCHMarginSF128, default = 8)
• Upgrade to 15 codes possible only with HSPDSCHMarginSF128 = 0
HSDPA code allocation - dynamic share with R99
HSDPA code allocation - dynamic share with R99Downgrade due to NRT R99 traffic
If a NRT R99 request cannot be served due to code blocking, HSDPA is downgraded only, if the actual number of codes exceeds
Maximum code set – DPCHOverHSPDSCHThreshold• Default = 0 → HSDPA always has higher priority than incoming NRT R99 request
• Threshold = 5 → HSDPA downgraded due to incoming NRT R99 request, if actually more than 15 - 5 = 10 codes reserved for HSDPA
Nu
mb
er
of
all
oc
ate
d S
F1
6 c
od
es
DPCHOverHSPDSCHThreshold
6789101112131415 Maximum code set
5
HSDPA code allocation - impact of HSUPA
SF=1
SF=2
SF=4
SF=8
SF=16
SF=32
SF=64
SF=128
SF=256
14 HS-PDSCH codes14 HS-PDSCH codes
Up to three HS-SCCH codes
Up to three HS-SCCH codes
Codes for common channels in the cellCodes for common channels in the cell Codes for associated DCHs
and non-HSDPA usersCodes for associated DCHs
and non-HSDPA users
E-AGCH (256) E-AGCH (256)
E-RGCH/E-HICH (128)E-RGCH/E-HICH (128)
New DL signaling channels occupying at least the following codes• 1 x SF256 by E-AGCH
• 1 x SF128 by E-RGCH / E-HICH (these two channels share one code)
Loss of a second code with SF16 → maximum of 14 codes for HSDPA
High code congestion
Many DCH of low activity
High code congestion - optimization flow
Enable throughput based optimization (R99 DCH)
Check SHO parameter settings
Check adjacent cell interference
High SHO overhead
Enable code tree optimization
Still high congestion
Enable F-DPCH (associated DCH)
Many associated
DCH
•Principles
•Transmitted carrier power
•Received total wideband power
•Code tree allocation
•Channel element allocation
•Monitoring
•BTS channel cards
•R99 dimensioning (optional)
•HSDPA dimensioning (optional)
•HSUPA dimensioning (optional)
•Iub transmission
•RNC processing load
•Number of users
Traffic Monitoring
For daily work often more convenient to know the percentage of occupied CE instead the absolute number
Both for DL and UL six to indicate, how often total utilization falls into certain interval• 0-49 %
• 50-69 %
• 70-79 %
• 80-89 %
• 90-99 %
• 100 %
Monitoring - total utilization
80-89%90-99%
70-79%
100%
Monitoring - total utilizationPractical example – UL on single BTS
In most cases very high utilizationTypically 80-89 % or 90-99 %
Both for DL and UL five additional to indicate, how often utilization by HSPA falls into certain interval• 0-19 %
• 20-39 %
• 40-59 %
• 60-79 %
• 80-100 %
Monitoring - utilization by HSPA
Monitoring - utilization by HSPAPractical example – UL on single BTS
In most cases very high utilization due to HSUPATypically 80-89 %
In general, each DCH occupies a certain number of CE in dependence on the type of service
The CE occupation is the same for• FSMC/D/E and WSPF cards
• R99 DCH and associated DCH
R99 dimensioning
Service CE
SRB / voice / 16 K data 1
32 K data 2
64 K data 4
128 K data 4
256 K data 9
384 K data 12
Less CE needed for DCH of 256 K and 384 K
All other rules remain unchanged
R99 dimensioning
Service CE
SRB / voice / 16 K data 1
32 K data 2
64 K data 4
128 K data 4
256 K data 6
384 K data 8
High CE occupation - optimization flow
High CE occupation
Many DCH of low activity
Enable throughput based optimization (R99 DCH)
Check SHO parameter settings
Check adjacent cell interference
High SHO overhead
Enable F-DPCH (associated DCH)
Many associated
DCH
Principles
Transmitted carrier power
Received total wideband power
Code tree allocation
Channel element allocation
Iub transmission
Implementation principles
Monitoring options
Examples
RNC processing load
Number of users
Traffic Monitoring
M550 – CAC AAL2 Path Measurements 2 VCs with 8250 (ATM) cells per second per VC on 1 IMA group
Examples - physical ATM trafficTwo VC multiplexed by IMA
Cell rate reserved by CAC per VC
Configured bandwidth
Maximum reserved bandwidth
Minimum reserved bandwidth
Free bandwidthEven maximum reserved bandwidth far below configured bandwidthNo risk of physical congestion
Examples - logical ATM trafficTwo VC multiplexed by IMA
Number of AAL connections established by CAC per VC
Even in busy hour number of AAL connections clearly below maximum of 248No risk of logical congestion
Principles
Transmitted carrier power
Received total wideband power
Code tree allocation
Channel element allocation
Iub transmission
RNC processing load
RNC block diagram
Monitoring options
Number of users
Traffic Monitoring
After the patch is installed for the RNC, almost all the call drops with the cause being “Other” have disappeared
and the PS call drop rate is obviously lower, as shown in the following table. The problem is thus solved.
Solution
Note: You can get the table on the right via custom report or “Performance Query” of Nastar.
Case — High Call Drop Rate due to RNC Traffic Measurement Defect (Continued)
•Principles
•Transmitted carrier power
•Received total wideband power
•Code tree allocation
•Channel element allocation
•Iub transmission
•RNC processing load
•Number of users
Traffic Monitoring
Number of users - licensesR99• No license for specific number of users per cell required
• New user allocated, as long all types of RAN resources available
HSPA• License for specific number of users per cell required
• The following levels are available• 16 users
• 48 users
• 64 users
• 72 users
• If maximum number of users present, new user rejected, even if all types of RAN resources still available
RRC connection setupRAN resources reserved for signaling connection between UE and RNC
RRC accessConnection between UE and RRC
RRC activeUE has RRC connection
If dropped, also active RAB dropped
RAB setupAttempts to start call
RAB setup access
Connection between UE and core
RAB active phaseUE has RAB connection
CSSR affected if any of the following
events takes place
• RRC Connection Setup Fail
• RRC Connection Access Fail
• RAB Setup Fail
• RAB Setup Access Fail
SetupComplete
SetupComplete
AccessCompleteAccess
Complete
ActiveComplete
ActiveComplete
SetupSetup AccessAccess ActiveActive
Att
em
pts
Setup failures(blocking)
Access failures
Acc
ess Active
ReleaseActive
Release
ActiveFailuresActive
FailuresRRCDrop
Succ
ess
Phase:
RRC and RABCall setup - phases
[RACH] RRC Connection RequestRACH] RRC Connection Request
UEUE Node BNode B RNCRNC
ALCAP ERQ
NBAP RL Setup Request
[DCH] RRC Connection Setup Complete[DCH] RRC Connection Setup Complete
L1 Synchronisation
Start TX/RXStart TX/RX
Start TX/RXStart TX/RX
[FACH] RRC: RRC Connection Setup
NBAP RL Setup Response
AC to check to accept or reject RRC
Connection Request
AC to check to accept or reject RRC
Connection Request
ALCAP ECF
NBAP Synchronization Indication
RRC Connection Setup phase
RRC Connection Access phase
RRC Connection Active phase
Allocation of UTRAN
resources
Waiting for UE reply
Three phase for RRC
Call setup – successful RRC establishmentSignalling and trigger
=
RRC Connection – SETUP and ACCESS PHASE
[RACH] RRC Connection RequestRACH] RRC Connection Request
UEUE Node BNode B RNCRNC
ALCAP ERQ
NBAP RL Setup Request
[DCH] RRC Connection Setup Complete[DCH] RRC Connection Setup Complete
L1 Synchronisation
Start TX/RXStart TX/RX
Start TX/RXStart TX/RX
[FACH] RRC: RRC Connection Setup
NBAP RL Setup Response
AC to check to accept or reject RRC Connection
Request
AC to check to accept or reject RRC Connection
Request
ALCAP ECF
NBAP Synchronization Indication
RRC Connection Setup phase
RRC Connection Access phase
Allocation of UTRAN
resources
Waiting for UE reply
Three phase for RRC
Signalling and trigger
=
1. RRC setup attempts.
2. RRC setup attempts per setup cause. (SEE NEXT SLIDE)
3. RRC setup failures due to
• handover control , • admission control
• transport (Transmission)• RNC internal
• frozen BTS • BTS • ICSU overload
4. RRC setup failure per cause.
5. RRC setup complete.
6. RRC access failures due to• radio interface • UE• RNC internal
7. RRC access complete.
8. Special reason: RRC active release due to • SRNC Relocation • Pre-emption
• User inactivity • RNC HW resources
• ISHO to GAN • Inter-system handover to GSM • IF inter-RNC hard handover • Inter-frequency inter-RNC hard handover
9. RRC active failures due to• Iu interface (transport) • radio interface (synchronisation) • BTS • Iur interface (DRNC) • RNC internal • UE • Transmission
10. RRC active complete
1. RAB setup attempts. Separate counter per each RAB type.
2. RAB setup failures due to • admission control • transport (transmission) • RNC
internal • frozen BTS • BTS (RT only) • anchoring (NRT only) • capacity license (for CS voice RAB only)
3. RAB setup complete. Separate counter per each RAB type.
4. RAB access failures due to • UE • RNC internal
5. RAB access complete. Separate counters per each RAB type.
6. Special reason: RAB active release due to • SRNC relocation • pre-emption • capacity license pre-
emption (only for CS voice RAB)
7. RAB active failures due to• Iu interface (transport) • radio interface (synchronisation) •
BTS • Iur interface (DRNC) • RNC internal • UE • Transmission
8. RAB reconfiguration attempts. 9. RAB reconfiguration failures. 10. RAB active complete. Separate
counters per each RAB type.
Drop Call Analysis
Presentation / Author / Date
Case 1: Drop due to missing neighbor
Problem: Detected Nighbor (DN)
UE sends a Measurement Report that contains an event1a means adding a new RL (cell) to Active Set
If the reported cell is not in the current neighbor cell list and the reported Ec/No is better than the best serving cell Ec/No in AS by some dBs (set by a RNC parameter)
If for any reason the new cell can not be added to AS, call will be released
Case 1: Drop due to missing neighbor
“DN” cell better than the serving cell
DL BLER gets worse
“DN” cell better than the serving cell
DL BLER gets worse
Case 2: Drop due to Poor Coverage (low RSCP)
Problem: Poor DL coverage
When UE gets to an area with low RSCP ( < -105 dBm)
regardless Ec/No values there is high risk for drop.
UE will likely ramp up the transmitted power and reach its
max power. The DL BLER will probably increase and SIR
target cannot maintain anymore, finally the call drops.
Case 2: Drop due to DL Poor Coverage
Very bad RSCP
UE max Tx powerandhigh DL BLER
Very bad RSCP
UE max Tx powerandhigh DL BLER
Case 3:PS: Session Error due to Poor DL Coverage
UE enters a very low coverage area (RSCP < – 105 dBm).
The packet connection is carried on a 64/64 DCH Channel
as consequence of the low coverage conditions.
The UE will likely ramp up its power to the maximum, goes
to Idle Mode and the Application and RLC throughputs go
to zero.
At this point the RAS application will start the Session
Timeout timer, if the throughput is not resumed the Session
Error event is triggered with cause “session timeout”.
PS: Session Error due to Poor DL Coverage
App throughput ~64kbps
Very low RSCP
App throughput ~64kbps
Very low RSCP
FINAL WORDSFor network tuning, we need to rely on field measurements which require extensive
drive tests
Finding the best possible configuration for antenna heights, tilts, azimuths and parameter setting for all the present cells/sectors in the network and also for any new sites that might be needed to improve coverage
Power adjustment can also be used for network tuning but can become complicated and result in poor network performance
Use of Remote Electrical Tilt (RET) Antenna is preferred over mechanical tilt antenna
Neighbour definition is of prime importance in UMTS network (Soft handover gain and interference reduction). Keep neighbour list upto 20.
Automated tools are needed that could suggest the best possible neighbour relations, antenna heights and tilts by using both the field measurements and the propagation models & simulations
Skilled people, right methods and advanced tools are needed to perform 3G tuning and optimisation
Presentation / Author / Date
Call Drop analysis Top (N) drops
Cell and its Neighbour Cells availabilityAlarms/Tickets
Configuration & Parameter audit
SHO Success Rate < 90%?
Conf OK ?
Site OK ?
ISHO Failures
Iur
performance Investigation Iur
Audit adjacent sites for alarms, Availability, configuration and
capacity
TrafficNeighbours’ Performance
(use SHO success per adjs counters to identify badly
performing neighbours) & Map
3G Cell at RNC border?
NO
YES
New site ?
Analyse last detailed radio measurements
RF and IFHO neighbour optimisation
No cell found ratio
>40 %
ISHO Success
Rate < 90%
RF and ISHO neighbour optimisation
3G cell covers over a
coverage hole ?
3G cell at inter-RNC border ?
Wrong reference clock (10MHz tuning)
No cell found ratio > 90 % and enough
ADJG
2G Cell Doctor
2G Investigation : TCH blocking or
TCH seizure failure
(interference)
NO
YES
YES
YES
NO
YES
NO
YES
YES
SHO
ISHO
Top issues
SHO based on DSR, CPICH EcNo difference, SHO branch setup fail BTS/Iub
HHO RSSI & BSIC time,
ISHO cancellation
Max HSPA users in cell/RNC,RNC licensed capacity:Max AMR/Iups
throughput
Relocation success in target RNC
HSDPA IFHO failures, reject CM for IFHO
Presentation / Author / Date
Call Drop analysis 1. Check high call drop cells and its neighbouring cells of any faulty alarms
2. Identify call drop root cause failure distribution and main failure contributor (radio, Iu, BTS, Iur, MS, RNC)
3. Check SHO KPI if performance < 90% ( leads to radio failure)
• Check if cells are at RNC border (check Iur capacity and SRNC relocation problem)
• Detect badly performing neighbours using HO success rate per adjacency counters (M1013)
• High incoming HO failure rate in all adjs – check sync alarms
• Assessing neighbor list plan and visualization check with map
• Evaluate HO control parameters and trigger threshold
4. Check ISHO KPI if RT ISHO < 90% or NRT < 80% (leads to radio failure) Check missing neighbour (M1015), GSM frequency plan neighbour RNC and MSC database consistency
audit, check alarm of reference clock in 3G or in 2G, check 2G TCH congestion Check RRC Drop ISHO RT / NRT
Presentation / Author / Date
Call Drop analysis
5. Detecting DL or UL path loss problem if RAB drop due to radio (dominant call
drop cause > 50%) Check UL Lost Active KPI from Iub counters (active L1 synchronization failure) to check UL/DL
path loss problem Check ASU failure rate (UNSUC_ASU) which link to NO RESPONSE FROM RLC Mapping radio failures with Tx power and CPICH related parameters ->
CPICHToRefRABOffset, PTXDPCH MAX Check Call reestablishment timer -> T315 Ecno distribution for bad coverage issue (M1007C38-M1007C47)
6. Check core network parameter setting if RAB_ACT_FAIL_XXX_IU Check SCCP SGSN/RNC IuPS Tias/Tiar if RAB_ACT_FAIL_BACKG_IU
7. If high RAB_ACT_FAIL_XXX_BTS Check if any BTS faulty alarm (7653 cell faulty alarm) If no alarms, COCO detach/attach
8. If high RAB_ACT_FAIL_XXX_MS• Check physical channel reconfiguration failure rate (IFHO, ISHO, code optimisation)
HSDPA Low Throughput
Presentation / Author / Date
HSDPA Throughput Analysis
Presentation / Author / Date
Good CQI but poor HSDPA throughput
Presentation / Author / Date
COMMON CALL PERFORMANCE ISSUES
Presentation / Author / Date
Common Call Performance Issues
Presentation / Author / Date
Common Call Performance Issues
Presentation / Author / Date
Common Call Performance Issues
Presentation / Author / Date
Common Call Performance Issues
Presentation / Author / Date
Common Call Performance Issues
Presentation / Author / Date
Presentation / Author / Date
Common Call Performance Issues
Presentation / Author / Date
Video Call Performance Issues
Presentation / Author / Date
Video Call Performance Issues
Presentation / Author / Date
ISHO Performance Issues
Soft Handover Neighbour Tuning
Presentation / Author / Date
Active Set UsageM1013 (These counters are referred to cell addition and cell replacement – no target for deletion)
Absolute Value must be considered not Failure Rate!
Active Set Usage
High # out-going attempts?
In – out pairs?
Zero attempts?
Ping-Pong
No Adjs
Low used Adjs
Yes
Yes
Yes
Unbalanced WCEL
High # attempts for a source?
Unbalanced ADJS
Yes
Minor
Filtering over attempts must be taken into count that:
- statistical data must stabilized over time.
- traffic distribution is not considered and a double-check to localize the event and DT feedback is required to understand if fenomena is traffic driven or cell dependent
High # out-going fails for a defined ADJS?
Major
Failure ADJS
Yes
High # fails for a source?
Failure WCEL
Yes
Minor
Filtering over failure in absolute terms it is possible to find the major critical events
Active Set Usage
Filtering criteria:
Major - High number of failures for a defined out-going adjs (failure ADJS)
- high number of fail for a defined source (failure WCEL)
Minor- high number of attempts in-comig and out-going for a defined pair with occasional failure (ping-pong)
Filtering action are required to find bi-lateral corrispondence - very low number of attempt with failure (low used adjs)
- zero number of attempt for declared adjs– stabilized value (no adjs)
- high number of attempts with occsional failure for an out-going adjs (unbalanced ADJS)
Either in-coming or out-going condition is sufficient
- high number of attempts with occsional failure for a defined source (unbalanced WCEL)
Failure ADJS
Once anlyzed the RSCP, the coverage plot taking care to the evaluation of intersite-distance, it is easy to understand if target can be used.
If not only down tilt is possible or DERR (ADJS object Paremeter) cell to avoid the failure during SHO.
Down tilt must be carefully anlyzed.
If from Ec/No the cell can be recovered an individual offset or filtering (ADJS object Parameter) can be introduced to fovourite it
Failure ADJS
Analyze RSCP from DT & NWP coverage plot considering inter-site distance
Target act as polluter?
Down tilt
Yes
Analyze Ec/No from DT
Down tilt possibile?
DERR cell
Yes
Ec/No offset
Very low value of RSCP that not allow the adjs to be used
…Attempt Fail Attempt Fail Attempt Fail Attempt Fail
Source_cell_A 2 1 23 1 442 34 4 0Source_cell_B 1 0 11 0 53 25 345 0
…Source_cell_Z 322 54 15 0 2 0 12 0
Target_cell_A Target_cell_ZTarget_cell_CTarget_cell_B
Failure ADJS – Individual Ncell Offset
time
P CPICH 1
P CPICH 2
P CPICH 3
Reporting Range
Reporting Event 1B
Reporting Event 1A
AdjsEcNoOffsetto modify measurement reporting behaviour. Effectively 'moves' cell border (shrinks or enlarges cell)
Enlarging Cell 3 by x dB
Ec/Io
Failure ADJS – Forbidding Neighbour Cell
Time
P CPICH 1
P CPICH 2
P CPICH 3
PCPICH3 is forbidden to affect the reporting range as its quality is quite unstable.
Reporting
Range
AdjsDERRto forbid a cell from reporting range calculation in some instances
Ec/Io
Failure WCEL
KPI(1) ?
Failure WCEL
Tune 1A
Yes
KPI(2) ? Tune 1C
Yes
Analyze Ec/No &BLER from DT & NWP coverage plot considering inter-site distance
WCEL polluted/interfered?
Yes
Analyze Ec/No from DT
Pollution/Interference
Most of the Target failure during the 1A or 1C event.
Once anlyzed the Ec/No, BLER, the coverage plot taking care to the evaluation of intersite-distance, it is easy to understand if the WCEL is interferered/Polluted
If not, two KPIs allow to separate the dominant contribute among the 1A and 1C.
Relaxing the parameters an improvement should be achieved
The following gives the number of attempts per event
RT Services
KPI(1) = M1007C10 CELL ADD_REQUEST ON SHO FOR RT TRAFFIC
KPI(2) = M1007C12 CELL REPL_ REQUEST ON SHO FOR RT TRAFFIC NRT Services
KPI(1) = M1007C27 CELL ADD_ REQUEST ON SHO FOR NRT TRAFFIC
KPI(2) = M1007C29 CELL REPL_REQUEST ON SHO FOR NRT TRAFFIC
The failure rate for all the procedure can be estimated as well
ADD(REPL)_ FAIL_ONSHO _FOR_x / ADD(REPL)_REQ_ON_SHO_FOR_x + ADD(REPL)_ FAIL_ONSHO _FOR_x
M1007C14 / M1007C12 + M1007C14
M1007C36 /M1007C11 + M1007C36
M1007C30 / M1007C27 + M1007C30
M1007C37 / M1007C28 + M1007C37
M1007C31 / M1007C29 + M1007C31
…Attempt Fail Attempt Fail Attempt Fail Attempt Fail
Source_cell_A 2 1 23 15 442 34 124 23Source_cell_B 1 0 11 0 53 0 345 0
…Source_cell_Z 322 1 15 0 2 0 12 0
Target_cell_A Target_cell_ZTarget_cell_CTarget_cell_B
Failure WCEL - 1A
RNC
Strongest CPICH in AS:
time
Ec/Io
P CPICH 3
P CPICH 1
P CPICH 2
1A
AdditionWindowdetermines the relative threshold used by the UE to calculate the reporting range of event 1A. The threshold is either relative to the CPICH Ec/No measurement result of the best active set cell (0), or to the sum of active set measurement results (<>0)
AdditionTimedefines the 'time-to-trigger' interval between the cell entering the reporting range and the UE sending the measurement report to the RNC with the 1A event
AdditionReportingIntervaldefines the period of time that the UE wait, if the RNC is unable to add Ncell to AS, before sending further reports periodically, with interval AdditionReportingInterval, until the Ncell moves out of reporting range, or RNC adds Ncell to AS.
MeasurementReport
Add tothe AS?
no
ActiveSetWeightingCoefficientis used to weight either the measurement result of the best active set cell (0) or the sum of measurement results of all active set cells (<>0)
Failure WCEL - 1C
time
weakest CPICH in AS
Ec/Io
P CPICH 3
P CPICH 1
P CPICH 2
P CPICH 4
AS has 3 cells
ReplacementReportingInterval
If the RNC is not able to replace the active cell with the monitored cell, the UE continues reporting after the initial report by reverting to periodical measurement reporting. The parameter Replacement Reporting Interval determines the interval of periodical measurement reports when such reporting is triggered by the event 1C.
ReplacementWindow
determines the margin by which the CPICH Ec/No measurement result of the monitored cell (MNew) must exceed the CPICH Ec/No measurement result of the an active set cell (MInAS) before the UE can send the event 1C triggered Measurement Report to the RNC: MNew >= MInAs + ReplacementWindow / 2
ReplacementTimeDefines the period of time the monitored cell must continuously stay within the reporting range before the UE can send a Measurement Report to the RNC in order to replace an active set cell with the monitored cell (event 1C).
MeasurementReport
RNC
ASupdate?
no
1C
NO ADJS
No Adjs
Remove ADJS
Zero attempts?
Statistic Stable?
Yes
Repeat Analysis
Yes
DT analysis for the Adjs
Comparing the ADJS plan provisioned into the network with the M1013 matrix, it is easy to find if one declared ADJS is not used (not present in the list)
Statistic data must be stabilized before decide to remove it and DT analysis can help n estimating the amount of residual noise if down tilt is not possible
…Attempt Fail Attempt Fail Attempt Fail Attempt Fail
Source_cell_A 2 1 0 - 442 34 124 23Source_cell_B 0 - 11 0 53 0 345 0
…Source_cell_Z 322 1 15 0 2 0 12 0
Target_cell_A Target_cell_ZTarget_cell_CTarget_cell_B
Low used ADJS
Low used Adjs
Remove ADJS
Analyze DT result and NWP data
Monitored Qual from DT acceptable?
Alter. ADJS present?
Yes
Interference evaluation
Yes
ADJ Offset
It is not difficult in live network to find some pair working with very low
For low used ADJS has to be intended and ADJS that has few number of attemps in one day (e.g <3)
with occasional failure.
The ADJS removal has to be considered as the last option, after the quality has been monitored by drive test result, considering the overall capability of the target to be recovered (e.g. inter-site distance, power budget) and other options are available for that area.
Statistic data must be stabilized before decide to remove it and DT analysis can help in estimating the amount of residual noise if down tilt is not possible
…Attempt Fail Attempt Fail Attempt Fail Attempt Fail
Source_cell_A 2 1 25 4 442 34 124 23Source_cell_B 245 23 11 0 53 0 345 0
…Source_cell_Z 322 1 3 1 2 1 123 20
Target_cell_A Target_cell_ZTarget_cell_CTarget_cell_B
Unbalanced ADJS
Unbalance ADJS
Ec/No offset
Analyze RSCP from DT & NWP coverage plot considering inter-site distance e traffic distribution
Target act as polluter?
Down tilt
Yes
Analyze Ec/No from DT & evaluate unbalance
Down tilt possibile?
DERR cell
Yes
Attempt over the same UE?
Yes
An high number of attempt could be an indication of a problem and even in case of the failure is not associated an evaluation is required.
The key point is the inviduation of the attempt distribution, that in case are not justified but partcualar populated area, coluld generate lot of signalling.
The attempts could be genarated by 1B event ever the same UE not counted in the M1013.
The possibility to recover the ADJS is the favourite option and the down tilt carefully analyzed considering the failure associated.
No action required
…Attempt Fail Attempt Fail Attempt Fail Attempt Fail
Source_cell_A 54 3 345 10 23 1 124 5Source_cell_B 25 1 11 0 137 3
…Source_cell_Z 32 2 45 2
Target_cell_A Target_cell_ZTarget_cell_CTarget_cell_B
Unbalanced WCEL
KPI(1) ?
Unbalanced WCEL
Tune 1A
Yes
KPI(2) ? Tune 1C
Yes
Analyze RSCP from DT & NWP coverage plot considering inter-site distance and traffic distribution
WCEL interfered
polluted?
Yes
Analyze Ec/No from DT
Interference / pollution
Attempt over the same UE?
Yes
No action required
An high number of attempt could be an indication of a problem and even in case of the failure is not associated an evaluation is required.
The key point is the inviduation of the attempt distribution, that in case are not justified but partcular populated area, coluld generate lot of signalling.
The attempts could be genarated by 1B event ever the same UE not counted in the M1013.
The possibility to have an interference/pollution increase respect to the unbalanced ADJS.
The optimization should be performed at WCEL level
The KPI reported are the same of Failure WCEL
…Attempt Fail Attempt Fail Attempt Fail Attempt Fail
Source_cell_A 543 13 345 10 876 7 124 5Source_cell_B 25 1 11 0 137 3
…Source_cell_Z 32 2 45 2
Target_cell_A Target_cell_ZTarget_cell_CTarget_cell_B
Ping Pong
Ping-pong
Analyze RSCP from DT & NWP coverage plot considering inter-site distance
One of them act as polluter?
Analyze Ec/No from DT
Comparable value?
Histeresys using
Ec/NoOffset on the pair
Not stable, Fading?
Filtering
Yes
Yes
Down tilt
Down tilt possibile?
DERR cell Yes
Yes
Attempt from the same UE?
No action required
pollution
In this particular case the high number of attempt is concentrated in a pair
From A >> B and from B >>A as in the picture
As in the previous case could be an indication of a problem and even in case of the failure is not associated an evaluation is required to avoid to use a lot signalling.
The optimization should be performed at ADJS level considering that the filtering option could get to smoother measured value
…Attempt Fail Attempt Fail Attempt Fail Attempt Fail
Source_cell_A 54 3 345 10 23 1 124 5Source_cell_B 987 13 11 0 137 3
…Source_cell_Z 32 2 45 2
Target_cell_A Target_cell_ZTarget_cell_CTarget_cell_B
Ping Pong - Filtering
Node B
UTRAN
RNCUE
Measurement Control [ ]
I am in the CELL_DCH sub-
state
Measurement Type: Intra-frequency measurements Reporting events:1A: Event 1A triggered when CPCIH Ec/Io of the measured cell
enters UEreporting range for a defined period of time1B: Event 1B triggered when CPICH EC/I0 of the measured cell
drops outof the UE reporting range for a defined period of time1C: Event 1C triggered when CPICH EC/IO of the measured cell
enter inAS by a defined margin for a defined period of time
System Information [ ]
EcNoFilterCoefficient EcNoAveragingWindow
Applied for averaging of periodical meas. reports
Ec/NoFilterCoeffcontrols the higher layer filtering of physical layer measurements before the event evaluation and measurement reporting is performed by the UE.
Pollution
Polluter Detection
The best way to individuate a Polluter is the Drive Test
A feedback can come from coverage plot, RNP feedback and Counters
A polluter can be of different type:
1. PSC Pollution
Too high reuse factor for the PSC. New PSC plan is required
2. DL Noise raise
ADJS signal strength out of usage window (will be never utilized by the UE)
A down tilt or power reduction is the solution evaluating all the side effects
3. Dominant site
A dominant site over-shooting the ADJ becoming congested
A down tilt or power reduction is the solution evaluating all the side effects
PSC Pollution
A confirm for the polluter of the first type can come from the counter
M1007C38-47 CELL SPECIFIC CPICH EC/NO - CLASS x
Pollution Criteria:
The M1007C38-47 gives an indication of Ec/No distribution value measured during event 1A . Having the distribution highly unbalanced (normally centered on class 2, 3, 4) we have an indication of a probable problem. For example unbalancing towards the scarce value of Ec/No but continuing to add cells to AS could give an indication of pollution
Polluted WCEL
Yes
High number of class0-3?
High number of class>6?
Not Polluted WCEL Yes
Isolated/unavailable WCEL
DL Noise Raise
The NO ADJS and low used ADJS criteria before presented can give a confirm for a pollution of this type.
After the statistical data are stabilized, making across-check with the provisioned ADJS Plan the probable polluters are individuated.
This is obviously a cautelative estimation to be integrated and confirmed by drive test results
…Attempt Fail Attempt Fail Attempt Fail Attempt Fail
Source_cell_A 2 1 25 4 0 - 124 23Source_cell_B 245 23 11 0 53 0 345 0
…Source_cell_Z 322 1 3 1 0 - 123 20
Target_cell_A Target_cell_ZTarget_cell_CTarget_cell_B
Dominant site
Filtering the M1013 pairs for the recurrent target cell with associated occasional failure we have an estimation of the probable polluters
For the polluters, originating failures a down tilt is required
Polluted Cell Criteria:
SHO over head can give a soft help in individuating cell where polluter/overshooting site can be present or where unbalanced cell criteria could apply
%1001
T_NRT_IN_ACT_SETHREE_CELL M1007C21T_RT_IN_ACT_SETHREE_CELL M1007C2
NRTN_ACT_SET_TWO_CELL_I M1007C20RTN_ACT_SET_TWO_CELL_I M1007C1
NRTN_ACT_SET_ONE_CELL_I M1007C19RTN_ACT_SET_ONE_CELL_I M1007C0
3T_NRT_IN_ACT_SETHREE_CELL M1007C21T_RT_IN_ACT_SETHREE_CELL M1007C2
2NRTN_ACT_SET_TWO_CELL_I M1007C20RTN_ACT_SET_TWO_CELL_I M1007C1
NRTN_ACT_SET_ONE_CELL_I M1007C19RTN_ACT_SET_ONE_CELL_I M1007C0
RNC_79B OverheadHandover Soft
%1001
T_NRT_IN_ACT_SETHREE_CELL M1007C21T_RT_IN_ACT_SETHREE_CELL M1007C2
NRTN_ACT_SET_TWO_CELL_I M1007C20RTN_ACT_SET_TWO_CELL_I M1007C1
NRTN_ACT_SET_ONE_CELL_I M1007C19RTN_ACT_SET_ONE_CELL_I M1007C0
3T_NRT_IN_ACT_SETHREE_CELL M1007C21T_RT_IN_ACT_SETHREE_CELL M1007C2
2NRTN_ACT_SET_TWO_CELL_I M1007C20RTN_ACT_SET_TWO_CELL_I M1007C1
NRTN_ACT_SET_ONE_CELL_I M1007C19RTN_ACT_SET_ONE_CELL_I M1007C0
RNC_79B OverheadHandover Soft
…Attempt Fail Attempt Fail Attempt Fail Attempt Fail
Source_cell_A 2 1 25 4 26 3 124 23Source_cell_B 245 23 11 0 53 0
… … …Source_cell_Z 245 45
Target_cell_A Target_cell_ZTarget_cell_CTarget_cell_B
Cell Reselection
Cell Reselection List
GSM MS starts WCDMA measurements if :RLA_C< F(Qsearch_I) for 0<Qsearch_I<=7
orRLA_C> F(Qsearch_I) for 7<Qsearch_I<=15
If, for suitable UMTS cell & for a period of 5 s:
CPICH RSCP > RLA_C + FDD_Qoffset
CPICH Ec/No FDD_Qmin
and
WCDMA cellreselection
BCCH: FDD_Qmin, FDD_Qoffset
Cell Reselection 2G -> 3G
Startmeasurement
Depending on operator´s 2G – 3G interworking strategy parameter Q_search_I should planned accordingly.
Configuration 1RLA_C<
F(Qsearch_I) ( 0<Qsearch_I<=6 )
GSM 3G
Configuration 2RLA_C> F(Qsearch_I) ( 7<Qsearch_I<=15 )
In the best case, 3G cell measurements are restricted to the condition: RLA_C level > –78 dBm
GSM
3G
In the best case, 3G cell measurements are possible when RLA_C level < –74 dBm
GSM
3G
Configuration 3RLA_C< (always).
(Qsearch_I=7)
2G -> 3G Measurement
2G -> 3G Cell Re-selection Parameters
Qsearch_I and Qsearch_P define the threshold for non-GPRS/GPRS (respectively) capable UEs to measure 3G
neighbour cells when a running average of the received downlink signal level (RLA_C) of the serving cell
below (0-7) or above (8-15) the threshold
Value 0 1 … 6 7 8 9 10 … 14 15
dBm -98 -94 … -74 Always -78 -74 -70 … -54 Never
FDD_Qoffset and FDD_GPRS_Offset the non-GPRS/GPRS (respectively) capable UEs add this offset to the
RLA_C of the GSM cells. After that the UE compares the measured RSCP values of 3G cells with signal levels
of the GSM cells
Value 0 1 2 3 … 8 … 14 15
dBm Always -28 -24 -20 … 0 … 24 28
Always select irrespective of RSCP value Reselect in case RSCP >
GSM RXLev (RLA_C) +28dB
If RLA_C < -94 UE starts 3G measurements
UE always measures 3G cells
If RLA_C > -70 UE starts 3G measurements
FDD_Qmin, defines minimum Ec/No threshold that a 3G cell must exceed, in order the UE makes a cell reselection from 2G to 3G.
Cell Re-selection Example-Weaker WCDMANon GPRS case
t
Serving GSM Cell
Neighbour WCDMA Cell
Ec/NoRSCP/RLA_C
5 sec.
Cell re-selection to WCDMA
FDD_Qmin=0(-20 dB)
FDD_Qoffset =6 (-8 dB)
Qsearch_I=0 (-98 dBm)
RLA_C
Measurements starts (serving cell)
Minimum Quality Requirement for WCDMA
Ec/N0
RSCP
Cell Re-selection Example-Weaker WCDMAGPRS case
t
Serving GSM Cell (Best)
Neighbour WCDMA Cell
Ec/NoRSCP/RLA_C
5 sec.
Cell re-selection to WCDMA
FDD_Qmin=-20 dB
FDD_GPRS_Qoffset =10 (8 dB)
Qsearch_P=0(-98 dBm)
RLA_P
Measurements starts (serving cell)
Minimum Quality Requirement for WCDMA
Ec/N0
RSCP
Cell Reselection 3G -> 2G
Whilst camping in a 3G cell the UE performs intra-frequency, inter-frequency, and inter-system
measurements based on the measured CPICH EcNo.
Serving cell parameters Sintrasearch, Sintersearch and SsearchRAT are compared with Squal (CPICH Ec/No – Qqualmin) in S-criteria for cell re-selection
1 - None (Squal > Sintrasearch )
2 - WCDMA intra-frequency (Sintersearch < Squal Sintrasearch)
3 - WCDMA intra- and inter- frequency, no inter-RAT cells (SsearchRAT < Squal Sintersearch)
4 - WCDMA intra- and inter-frequency and inter-RAT cells (Squal SsearchRAT )
Sintrasearch Sintersearch SsearchRAT
WCDMA
CELL
1234
Cell Reselection 3G -> 2G
First ranking of all the cells based on CPICH RSCP (WCDMA) and RSSI (GSM)
Rs = CPICH RSCP + Qhyst1Rn= Rxlev(n) - Qoffset1
First ranking of all the cells based on CPICH RSCP (WCDMA) and RSSI (GSM)
Rs = CPICH RSCP + Qhyst1Rn= Rxlev(n) - Qoffset1
Rn (GSM) > Rs (WCDMA)And
Rxlev (GSM) >QrxlevMin
Rn (GSM) > Rs (WCDMA)And
Rxlev (GSM) >QrxlevMin
YesNo
Cell re-selection to GSM
Cell re-selection to GSM
Neighbour WCDMA or GSM cell calculation with offset
parameter
Serving WCDMA cell calculation, with
hysteresis parameter
UE starts GSM measurements if CPICH Ec/No =< qQualMin + sSearchRAT
UE starts GSM measurements if CPICH Ec/No =< qQualMin + sSearchRAT
SintraSearch
SinterSearch
SsearchRAT
CPICH EcNo
qQualMin
Second ranking only for WCDMA cells based on CPICH Ec/No
Rs = CPICH Ec/No + Qhyst2Rn=CPICH_Ec/No(n)-Qoffset2
Second ranking only for WCDMA cells based on CPICH Ec/No
Rs = CPICH Ec/No + Qhyst2Rn=CPICH_Ec/No(n)-Qoffset2 Cell re-selection to
WCDMA cell of highest R value
Cell re-selection to WCDMA cell of highest
R value
Cell Reselection 3G -> 2G
UE ranks the serving cell and the measured neighboring cells to find out if reselection should be made• All the measured suitable cells (S-criteria) are included in the ranking. • Criteria for a suitable cell (S-criteria) is defined as
– WCDMA intra-frequency neighbour cell: CPICH Ec/No > AdjsQqualmin and CPICH RSCP > AdjsQrexlevmin
– WCDMA inter-frequency cell: CPICH Ec/No > AdjiQqualmin and CPICH RSCP > AdjiQrexlevmin
– GSM cell:Rxlev > Qrxlevmin
Ranking is done using Criteria R, and the UE reselects to the cell with highest R-criteria. R-criteria is definedas:• For serving cell: Rs = Qmeas,s + Qhysts • For neighboring cell Rn = Qmeas,n – Qoffsetts,n
Qmeas is CPICH Ec/No for WCDMA cell and RxLev for GSM cell
How to avoid ping pong ?
When phone is camped on 3G, GSM measurements can start when CPICH Ec/Io of serving cell is below Ssearch_RAT + QqualMin.
When phone is camped on GSM, cell reselection to 3G is possible if CPICH Ec/Io of the candidate is above FDD_Qmin.
Therefore, to avoid ping pongs between 3G and GSM the following condition should be met:
FDD_Qmin >= QqualMin + Ssearch_RAT
QqualMin=-18 dB
Ssearch_RAT=4 dB
CPICH Ec/Io
FDD_Qmin >= -12 dB
QqualMin +Ssearch_RAT
t
Camping on 3G Measure GSM Camping on 3G
How to avoid ping pong ?
Parameters for cell reselections
• Qqualmin = -18dB Ssearch_RAT =2dB -> the 3G->2G cell reselection starts when Ec/No hits -16dB
• FDDQmin(GPRSFDDQmin) = -14dB (6) and QsearchP/QsearchI = always
The cell reselection paramters 3G -> 2G and 2G -> 3G provide only 2dB hysteresis which is not enough and should be noticed from the RNC statistics as high amount of INTR_RAT_CELL_RE_SEL_ATTS from all the RRC Connection Setup Attempts
• Recommendation is to adjust the FDDQmin from -14dB to -10dB (or even up to -8dB) to provide 6 to 8 dB hysteresis between 3G to 2G cell reselection and 2G to 3G cell reselection
• Another parameter to tune is Qrxlevmin
On top of Treselection the above parameters will slow down further the 2G to 3G and 3G to 2G cell reselections
Treselection
How long the reselection conditions must be fulfilled before reselection is triggered?Treselection
Impacts all cell reselections : Inter RAT, intra frequency and inter frequencyThe UE reselects the new cell, if the cell reselection criteria (R-criteria, see next slide) are fulfilled during a time
intervalTreselectionAs this parameter impacts on all the cell reselections too long Treselection timer might cause problems in high mobility areas but too short timer causes too fast cell reselections and eventually causes also cell reselection ping pongRecommended value 1s should work in every conditions i.e. enough averaging to make sure that correct cell is selectedHowever careful testing is needed to check the performance of different areas• (Dense) Urban area, slow moving UEs with occasional need for fast and accurate (to correct cell) reselections e.g.
outdoor to indoor scenarios or city highways – in some cases cell by cell parameter tuning is performed to find most optimal value between 0s and 2s but typically 1s is optimal value when workload is considered as well
• Highways, fast moving UEs must reselect correct cell – typically 1s works the best (however occasionally also 0s might be needed in fast speed outdoor to indoor cell reselections e.g. tunnels)
• Rural areas, slow or fast moving UEs need very often reselect between different RATs and make proper cell reselections even when the coverage is poor – typically 1s works the best
• Location Area Borders, usually the coverage is fairly poor – typically 1s works the best but sometimes to reduce location area reselection ping pong 1s is used when going from LA1 to LA2 and 2s from LA2 to LA1
IRATHO
IRATHO
As M1013 described in PartI, M1015 return statistic for intesystem HO. The filtering criteria can be replicated with the exception of ping-pong
Filtering criteria:
Major
- High number of failures for a defined out-going adjg (failure ADJG)
- high number of fail for a defined source (failure WCEL)
Minor
- very low number of attempt with failure (low used adjg)
- zero number of attempt for declared adjs– stabilized value (no adjg)
- high number of attempts for an out-going adjs (unbalanced ADJG)
out-going condition is sufficient
- high number of attempts for a defined source (unbalanced WCEL)
Same procedures can be applied to the case considering that the event related are 1E and 1F
1E/1F Events for CPICH Ec/No and RSCP
time
Cell 1Cell 2
Cell 3e.g
. P-C
PIC
H E
c/N
oHHoEcNo(RSCP)Cancel Defines the threshold of Ec/No(RSCP) that must be exceeded by a measurement of an active set cell to be canceled the event 1F related
HHoEcNo(RSCP)CancelTime determines the time period during which the CPICH RSCP of the active set cell must stay better than the threshold HHoRscpCancel before the UE can trigger the reporting event 1E.
HHoEcNo(RSCP)Thresholddetermines the absolute CPICH Ec/No threshold which is used by the UE to trigger the reporting event 1F. When the measured CPICH Ec/No of all active set cells has become worse than or equal to the threshold in question, the RNC starts inter-frequency or inter-RAT (GSM) measurements in compressed mode for the purpose of hard handover.
HHoEcNo(RSCP)TimeHysteresisdetermines the time period during which the CPICH Ec/No of the active set cell must stay worse than the threshold HHoEcNoThreshold before the UE can trigger the reporting event 1F.
1E
1F
IRATHO – Triggering reason
4. DL DPCH approaches itsmaximum allowed power
FMCG: GSMcauseTxPwrDL
5. Quality deterioration report from UL outer loop PC
FMCG: GSMcauseUplinkQuality
3. UE Tx power approaches its maximum allowed power, event 6A/6D
FMCG: GSMcauseTxPwrUL
2 . Low measured absoluteCPICH RSCP, events 1E/1F
FMCG: GSMcauseCPICHrscp
1. Low measured absolute CPICH Ec/No, event 1E/1F
FMCG: GSMcauseCPICHEcNo
GSMcauseX These parameters indicates whether a handover to GSM caused by low measured absolute CPICH Ec/No of the serving cell is enabled (1)
6 . Others- Load and Service based HO- IMSI based HO- Emergency ISHO
Triggering reason gives
an indication
IRATHO – Triggering reason
Allcauses
RTNxxxCMODWHHOIS
RTNxxxCMODWHHOISpercCausexxx
)_(____
)_(______
Allcauses
RTNxxxCMODWHHOIS
RTNxxxCMODWHHOISpercCausexxx
)_(____
)_(______
It’s important to know which is the most frequent triggering reason:
It’s possible to diffentiate between quality and coverage reasons and understand the
network limiting factors:
1. CPICH coverage
2. Pilot pollution
3. UL/DL Service coverage
In actual case is possible to dsciminate between low CPICH coverage triggered by high# RSCP
attempts or probable pilot pollution triggered by high # Ec/No attempts
A KPI that gives reason for that is
IRATHO – Triggering reason
High # Ec/No?
Start
UL level limiting
Yes
High # RSCP?
High # UE
Tx pwr?
High # UL Qual?
New site required or new
Parametrization for IRATHO
UL qual limiting
YesLoad analisys and UL interference evaluation
DL Qual limiting
YesDL interference/ Pollution should be evaluated
DL level limiting
YesCPICH power analisys/ new site required
UL
DL
This condition should be the dominannt one without associated failure
Enabling all the causes a screaning on the network is returned individuating the limiting factor and the required action.
High # DL
DPCH?Service limiting
YesNew planning for service is required
End
IRATHO - Failure
Failure can happen at different point:
Before decision
- Before CM
- During CM
- Measuring GSM cell
After decision
- Drop
Utran and ue have to treated as particular case
UE Node B RNC
RRC: Measurement Report
RRC: Measurement Control
NBAP: Radio Link Reconfiguration Prepare
NBAP: Radio Link Reconfiguration Ready
NBAP: Radio Link Reconfiguration Commit
RRC: Physical Channel Reconfiguration
RRC: Physical Channel Reconfiguration Complete
NBAP: Compressed Mode Command
RRC: Measurement Report
RRC: Measurement ControlGSM RSSI Measurement
ISHO triggering (5 reasons are possible)
Initial Compressed Mode Configuration
CN
RANAP: SRNS Context Request
RANAP: SRNS Context Response
RANAP: IU Release Command
RANAP: IU Release Complete
RRC: Cell Change Order from UTRAN
RANAP: SRNS Data Forward Command
CM not possible
The following KPI gives an indication of the number of CM procedure not started
If CM fails one of the following mus be checked:
Not enough resources – AC reject CM.Evaluate interferenceExpand capacity(see PartI)
RNCRNCUEUE
RRC: Measurement Report (3,4,5)
RRC: Measurement Control
BTSBTS
Admission Control check for CM
Admission Control check for CM
NBAP: Radio Link Reconfiguration Prepare
NBAP: Radio Link Reconfiguration Ready
NBAP: Radio Link Reconfiguration Commit
RRC: Physical Channel Reconfiguration
RRC: Physical Channel Reconfiguration Complete
NBAP: Compressed Mode Command
RRC: Measurement Control
RRC: Measurement Report
NBAP: Compressed Mode Command
RRC: Measurement Control
RRC: Measurement Report
BSIC verification phase for target cell
RX Level measurement phase for
all ISHO neighbours
AC is responsible for checkiing if CM is possiblle
j
jMODIS_HHO_W_COS_STA_NOT_PIS_COM_MOD
OS_STA_NOT_PIS_COM_MOD
j
jMODIS_HHO_W_COS_STA_NOT_PIS_COM_MOD
OS_STA_NOT_PIS_COM_MOD
Considering that M1010C2 (INTER SYST COM MOD STA NOT POS FOR RT) is updated if it is not possible to start inter-system compressed mode measurement due to radio resource congestion, BTS- or UE-related reasons to have a better insight on radio congestion it could be better to use, e.g. for UL the M1002C361 REQ FOR COM MODE UL REJECT TO INT SYST HHO IN SRNC and the M1002C357 REQ FOR COM MODE UL TO INT SYST HHO IN SRNC and use the following :
M1002C361/M1002C357
NO Cell Found
Missing ADJG could be the reason or a dedicated parameter tuning for the 1F event. The KPI can be madified taling care of the WO_CMOD events
The following KPI gives an indication of the number of GSM cell not found
NO Cell Found means:
there is no suitable gsm target cell in terms of RX Level
OR
the target gsm is suitable but its BSIC verification fails
AND
the maximum number of measurement reported are received
AND
maximum measurement interval is not expired
CompressedMode start
No Cell FoundCounters
HHO AttemptCounters
… measurement fail
… measurement not fail
Allcauses
Allcauses
RTNxxxCMODWHHOIS
RTNxxxCELLNOHHOISRateFailMeasISHO
)_(____
)_(_______
Allcauses
Allcauses
RTNxxxCMODWHHOIS
RTNxxxCELLNOHHOISRateFailMeasISHO
)_(____
)_(_______
NO Cell Found
High #
NO Cell?
ADJG
Addition?
Yes
Verify
ADJG
Yes
Start
Reduce “Cancel”
Increase “Time hysteresis”
Good GSM coverage in the near field?
Yes
Coverage anlisys
End
End
Good GSM coverage in the far field?
Reduce
“thershold”
New site
requiredGSMCause=Ec/Nol?
Yes
Pollution evaluation
DROP & UNSUCCESS IRATHO
Allcauses
Allcauses
RTNxxxATTHHOIS
RTNxxxHHOISDRPSCONRateDropISHO
)_(___
)_(______
Allcauses
Allcauses
RTNxxxATTHHOIS
RTNxxxHHOISDRPSCONRateDropISHO
)_(___
)_(______
In this case the optimization is required and pass through the evaluate of GSM and 3G plot coverage. Optimize If necessary number of ADJG or NWP parameters otherwise tune RNW parameters.Thresholds can be relaxed to favourite an early exit from 3G layer
RRC DropCountersRRC DropCounters
HHO AttemptCounters
HHO AttemptCounters
ISHO SuccessCounters
ISHO SuccessCounters
ISHO UnsuccessCounters
ISHO UnsuccessCounters
UE FailureCounter
UE FailureCounter
UTRAN FailureCounter
UTRAN FailureCounter
Optimization for unsuccess is not possible because the reason are:
- physical channel failure (the UE is not able to establish the phy.
- Protocol error
- Inter-Rat protocol error
- Unspecified
Drop are related to drop call occurred during the procedure
3G –> 2G Unbalancing
VOICECSCOMPACCRAB
RTxxxATTHHOISISHOCallVoicePerc Allcauses
____
_______
VOICECSCOMPACCRAB
RTxxxATTHHOISISHOCallVoicePerc Allcauses
____
_______
This topic present the inherent problem due to the fact that the 2G layer is not involved in the analisys.
Few consideration can be performed under some assumption:
The following KPIs used over a cluster for CS voice service gives the percentage of the CM started over all the RAB, giving an idea of the attempted mobility procedure requested for a cluster where the 3G coverage should be assured
Once Correlated with voice drop due to radio link failure and rrc drop during ISHO, the KPI can help operator in understand the ISHO strategy. Similar KPI is possible for PS
Threshold to shrink the HO area or inhibit the procedure has to be setted
Better to use completes: failures, normal & SRNC reloc on denominator and use the KPI inside the 3G cluster or difining a polygon where 3G service is required