LTE Network Performance Analysis - For DT Exercise
April 30, 2017 | Author: riboetriboet | Category: N/A
Short Description
LTE Network Performance Analysis - For DT Exercise...
Description
Qualcomm Technologies, Inc.
Telkomsel LTE Assessment - Jakarta
Qualcomm Technologies, Inc.
Executive Summary
Project Overview LTE FDD – Network Performance Assessment Telkomsel launched LTE FDD network on 1800 MHz (band 3) by the end of 2015 Bandwidth for LTE FDD on 1800 MHz is mainly 10 MHz with some selected sites having 15 MHz ((DL EARFCN 1875) and 20 MHz (DL EARFCN 1826) E-UTRAN Vendor: Huawei (eRAN 7.0) UTRAN Vendor: Huawei (RAN 17.0)
3
Test Cases Telkomsel LTE-FDD 1800 Performance Assessment Tests
Stationary Near Cell Scenarios
Mobility Scenarios
Best Effort Throughput
CSFB
Inter-RAT
DL FTP Golden Triangle
M2L MO Short
L2W Reselection
DL FTP Ring Road
M2M MO Short
L2W Redirection
UL FTP Golden Triangle
MT Short
W2L Reselection
UL FTP Ring Road
L2G Reselection L2G Redirection
Idle Mode
Reselection
Single User Throughput 15 MHz, 1x1 (Pacific Place ) 15 MHz (Senayan City)
Stationary Far Cell Scenarios
Multi User Throughput
Single User Throughput
DL Tput
DL Tput
UL Tput
UL Tput
15 MHz, 2x1 (Central Park) 10 MHz, 2x2 (Jak Tv) 4
Executive Summary Good RF coverage(RSRP) with acceptable Quality(RSRQ, SINR). Physical optimization can further improve RF quality High UL interference due to aggressive UL power control settings and sub-optimal PRB allocation to lower PRBs In idle mode drive, UE stays at Connected Mode state for 38.8%, due to long inactivity timer and spurious paging, will impact network load and UE battery life Acceptable DL throughput and good UL throughput performance. Throughput performance limited by RF & resource availability Good CS Fallback voice call performance with ~100% CSSR and < 4 secs CST at M2M scenario Low LTE network loading. LTE to WCDMA parameters can be optimized to further improve the UE retention in LTE Overall good accessibility and retainability performance during busy hours Suboptimal ANR implementation. Large neighbor lists and PCI conflicts MIMO is not used at indoor cells mainly due to DAS limitation, except those using small cells (lampsite). Upgrade DAS to MIMO Parameter changes recommended for Idle Mode and connected mode LTE WCDMA IRAT, intra frequency handover, inactivity timer, UL power control, DL scheduler, UL Scheduler and CSFB
5
LTE Scorecard- RF Coverage
Good Acceptable Poor
Legend
Good RF Coverage with Acceptable Quality 94% of the drive route have in car RSRP > -100 dBm, and room for SINR improvement with physical tuning Golden Triangle RSRP
-85.7
Coverage
Ring Road RSRP
-83.1
(10% / Med / 90%)
RSRP - dBm
-140
-100.4
-70.9
-140
-44
-98.4
-69.7
9.7
Quality
-44
10
(10% / Med / 90%)
CQI
0
0
14.8 15
6
14.7 15
6
-10.3
Quality
-10.1
(10% / Med / 90%)
RSRQ - dB
-30
-12.4
-9.2
-30
-3
-12.4
11.07
Quality
-9
-3
11.6
(10% / Med / 90%)
DL SINR - dB
-13
1.9
24.1
30
All stats from DL_FTP Drive
-13
1.8
21.66
30
LTE Scorecard – Stationary DL Throughput Sub-optimal Stationary DL Throughput in Some Locations Near Cell Performance in Central Park is sub-optimal due to no 2CW usage
Stationary DL Throughput (Mbps) Max Theoretical - 10 MHz, 2x2
−
73.4
UE always reports Rank 1 despite 2 antennas availability in the eNodeB
In some locations, DL performance is limited by
Max Theoretical - 15 MHz, 2x2
100.1
Far Cell (Senayan City) - 15 MHz, 2x2
18.4
Far Cell (Pacific Place) - 15 MHz, 1x1
4.8
Near Cell (Senayan City) - 15 MHz, 2x2
40.3
Near Cell (Pacific Place) - 15 MHz, 1x1
48.1
Near Cell (Jak TV) - 10 MHz, 2x2
34.3 0
Number of RBs (high number of users in the location)
−
RF condition
Locations for stationary testing are Point of Interests (POIs) defined by Telkomsel
60.7
Near Cell (Central Park) - 15 MHz, 2x2
−
−
Normally in important places and well-known shopping malls
−
Number of users is expected to be quite high in such POIs
Good Performance Acceptable Performance – limited either by RF or number of RBs 20
40
60
80
100
120
Sub-optimal Performance
7
LTE Scorecard – DL Throughput Acceptable DL Mobility Throughput Mobility - Golden Triangle
Throughput (Mbps) 18.7 0
5
10
21.3
15
20
25
0
Scheduling Rate (%)
10
20
Scheduling Rate (%)
88.4 0
20
40
60
80
92.8 100
0
RB Allocation
50
10
20
30
50
0
20
40
5
−
Lower number of RBs allocated
DL throughput in mobility could be further enhanced by improving SINR and RB allocations strategy
60
10
15.9
15
20
0
MIM0 2 TB (%)
5
10
20
40
20
Good Performance 63.1
60
80
DL BLER (%)
0
20
40
60
80
Acceptable Performance – limited either by RF or number of RBs Sub-optimal Performance
DL BLER (%) 8.7
5
15
MIM0 2 TB (%) 59.7
0
Lower scheduling rate
MCS 16.3
0
−
45.8
40
MCS 0
100
RB Allocation 41.5
0
Average throughput in Mobility in Golden Triangle is lower than in highway due to
Mobility - Ring Road Throughput (Mbps)
8.9 10
0
5
10 8
LTE Scorecard – Stationary UL Throughput Good Stationary Overall UL Throughput Stationary UL Throughput (Mbps)
Stationary UL Throughput is good Max Theoretical - 10 MHz
24.5
In some locations, UL performance is limited by
Max Theoretical - 15 MHz
39.2
Far Cell (Senayan City) - 15 MHz
26.6
Far Cell (Pacific Place) - 15 MHz
10.6
Near Cell (Senayan City) - 15 MHz
35.7
−
Number of RBs (high number of users in the location)
−
RF condition
Good Performance Acceptable Performance – limited either by RF or number of RBs
Near Cell (Jak TV) - 10 MHz
22.8 0
Sub-optimal Performance 5
10
15
20
25
30
35
40
45 9
LTE Scorecard – DL Throughput Acceptable UL Mobility Throughput Mobility-Golden Triangle
Mobility-Ring Road
Throughput (Mbps)
Throughput (Mbps)
11 0
5
14.9
10
15
20
Scheduling Rate (%)
0
5
10
15
93.5
50
100
0
50
−
Lower MCS
−
Lower scheduling rate
−
Lower number of RBs allocated
In general, the mobility UL throughput is good 100
RB Allocation
RB Allocation 32.6 0
20
Scheduling Rate (%)
90.5 0
Average throughput in Mobility in Golden Triangle is lower than in highway due to
39.7
20
40
0
20
40
60
20
30
MCS
MCS 18.8
20.1 Good Performance
0
10
20
0
10
PHR
PHR -0.3 -0.5
Sub-optimal Performance
0.2 0
0.5
-0.5
-0.3
-0.1
0.1
Acceptable Performance – limited either by RF or number of RBs
0.3
0.5 10
LTE Scorecard - CSFB Good Overall CSFB performance Call Setup Time
CSFB Call Setup Success Rate
2458
MT
3963
M2M MO
4524
M2L MO 0
1000
2000
3000
4000
MT
100
M2M MO
100 99.6
M2L MO 5000
99.4
99.5
99.6
99.7
Time (ms)
200
400
600
Time (ms)
100.1
100
M2M MO
984 0
100
99.4
MT
820
M2L MO
99.9
Fast Return to LTE Sucess Rate
762
M2M MO
99.8
%
Return to LTE TIme MT
Longer Call Setup delay on M2L due to core network signaling delay to landline number(Telkomsel customer care number)
800
97.2
M2L MO 1000
1200
95
96
97
98
99
100
101
% 11
Counters Observation Summary Busy Hours KPI (%)
UL Cell Thput
RRC Success Rate
99.92
Mbps Initial RAB Establishment
99.9
RAB Establishment
99.8
E-RAB Retainability
99.8
HO Success Rate
99.8
92
DL Cell Thput
0
0.95
98
100
%
0.73
%
0
0.27
2.17
10
15.83
PDCCH CCE Usage (90% / Med / 10%)
0
7.57
50
18.76
-120
-116
%
0
11.1
PRB DL Usage
-114
(90% / Med / 10%) 96
3
12.2
UL Interference 94
2.16
(90% / Med / 10%)
94 90
PRACH Usage (90% / Med / 10%)
PRB UL Usage %
LTE PS Retention
1.40
(90% / Med / 10%)
25.38
50
7.43
(90% / Med / 10%)
-109
% -105
0
3.6
17.85
50
15.83
(90% / Med / 10%)
Mbps
Low usage in general 0
7.57
CQI
25.38
30
10.35
(90% / Med / 10%)
Mbps
Improving cells with worst RF (CQI & MIMO) would increase DL efficiency 0
9
MIMO 2CW
12.2
15
46.9
(90% / Med / 10%)
%
Inactivity timer impact: 22.5 RRC connected users vs 5 active users
UL interference ~2.6 dB higher in busy hours. Higher load at low band PRB, related with PUSCH RB allocation Room to improve PS retention in LTE
0
13
63
100 12
Summary Observations and Recommendations Idle Mobility Performance Spurious paging
UE Stays Longer In Connected Mode
Suboptimal Idle Mode Reselection Configuration
• Observations • UE getting paged with for incoming data even with Data disabled on the UE • High frequency of paging messages observed in the logs • Source IP of pages indicated as google, facebook, blackberry, Singapore telecom, PT Telkom etc. • Incoming pages forces UE to go into connected more • Frequent connected mode transition will result in low battery life
• Observations • UE stays unexpectedly 39% of the time during idle mobility in LTE_Connected • Inactivity timer is configured to be 20 seconds • Long inactivity timer causes UE to stay in LTE_CONNECTED state longer and reduces UE battery life • High Ratio between active and connected users from counters
• Observations • Intra LTE reselection – UE starts measuring other LTE cells too early (draining UE battery life) • L2W reselection – Too early WCDMA measurements and L2W reselection triggers • W2L reselection – too high LTE cell RSRP criteria for W2L Reselection • In general, this causes lower traffic retention in LTE & reduced battery life
• Recommendation • Reduce inactivity timer to 10 seconds
• Recommendation • Intra LTE reselection – start measurement at later RSRP • L2W reselection – prolong L2W reselection to retain more traffic in LTE while ensuring service quality • W2L reselection – lower LTE cell RSRP reselection criteria from WCDMA Slide
• Recommendation • Investigate the source of incoming paging and implement firewall policy to block spurious packets Slide
Slide
13
Summary Observations and Recommendations Connected Mode Mobility Performance Intra LTE Mobility – Event A3
• Observations • Frequent Intra-frequency handovers observed between cells with coverage overlap • Low A3 offset causing handover to be triggered easily • A3-offset=1 dB • Recommendation • Increase A3-Offset to 2 dB
Slide
L2W IRAT Mobility – Event A2
W2L IRAT Mobility
• Observations • Low average PRB Usage in busy hours (~10% in DL and 12.% in UL) • Low PDCCH usage and RACH usage • Good IRAT redirection strategy in place • ~6% ratio of redirection compared to RRC attempt
• Observations • W2L redirection triggered when low activity is detected in WCDMA • Upon low activity detection, RNC configures compressed mode for LTE measurements • UE reports event 3C, then redirection takes place
• Recommendation • Room to improve PS retention in LTE through A2-threshold reduction
• Recommendation • Use blind redirection for W2L upon low activity in WCDMA for areas with good LTE coverage • Keep the current method for nonubiquitous LTE coverage
Slide
Slide 14
Summary Observations and Recommendations UL Performance High UL Interference
Higher Frequency of Lower PRB Allocation
• Observations • High UL interference is observed to from counter in off peak and peak hours • Interference ~2.6 dB higher in busy hours compared to offpeak • Higher UL interference at low band PRB, related with PUSCH RB allocation • Indoor cells have higher average UL interference • Recommendation • UL frequency selective scheduling and PUSCH power optimization to reduce UL interference • Investigate worst UL interference DAS cells for DAS configuration.
• Observations • Lower PRBs are allocated with higher frequency in both even and odd PCIs • Result in higher interference levels at lower PRBs as loading level will be close to 100% for these PRBs even with lower over all loading • Frequency selective scheduling is disabled • Frequency randomization scheduling enabled but not observed from UE logs
Slide
• Recommendation • Enable Frequency selective scheduling • Verify frequency randomization scheduling implementation Slide
High RACH Power
High PUSCH Transmit Power
• Observations • Very high RACH MSG3 transmit power. Average MSG 3 transmit power is 17.5 dBm • deltaPreambleMsg3 is currently set to very high value of 8 dB • 99% of the RACH attempts were successful on first preamble only. • preambleInitialReceived TargetPower set to -104 dBm
• Observation • Very high average PUSCH transmit power observed (18.3 dB) • Very aggressive power control settings (p0-NominalPUSCH= 67 dBm) • UE BLER significantly lower than 10 % in low path loss regions. • High UL TX power will result in high UL interference
• Recommendation • Decrease deltaPreambleMsg3 to 2 dB • Lower value of preambleInitialReceived TargetPower at -108 dBm can be trialed
• Recommendation • Decrease p0-NominalPUSCH to -80 dBm along • Increase alpha value of 0.8
Slide
Slide 15
Summary Observations and Recommendations DL Performance Lower MCS Than Reported CQI
Conservative RBG Allocation Strategy
• Observations • UE is using lower modulation than the one it should use according to the CQI reported • Network employs CQI adjustment with fixed target iBLER of 10% • DL BLER observed in far cell and in DL mobility test scenarios is around 8% – 9% • Conservative CQI adjustment for unloaded network
• Observation • Network is using ROUND_DOWN RBG allocation strategy • If the required RB is greater than multiple of RBG size, the outstanding RBs are allocated to the UE in the next TTI, causing UE to receive lower number of RB • RBs are efficiently used but the scheduling times also increase and the DL user rates decrease. For unloaded network, this is too conservative
• Recommendation • Trial CQI Adjustment with Dynamic iBLER target to allow UE to use higher MCS in the expense of higher initial iBLER • Additionally, enable StepVarySwitch to allow CQI adjustment step to vary based on the difference between current iBLER and target iBLER – faster iBLER convergence
• Recommendation • Use ADAPTIVE for RbgAllocStrategy • This mode prevents RB waste when the number of required RBs is less than that of one RBG, while rounding up RBGs allocated to UE
Slide
Slide 16
Summary Observations and Recommendations Automatic Neighbor Relation (ANR) PCI Conflict • Observations • UE reports A3 for PCI A, but eNB has 2 neighbors with same PCI • eNB is confused and requests UE to report eCGI for the PCI A every time UE reports A3 for PCI A • UE can only report eCGI after reading SIBs of PCI A when it enters CDRX mode • During continuous FTP DL, UE can hardly enter CDRX to read SIBs, therefore handover to PCI A never happens and UE stays in poor serving cell • Recommendation • Fix conflicting PCI neighbor settings • Ensure that all PCIs in the neighbor list are unique (no duplicate PCI referring to different cells) Slide
Huge Neighbor List • Observations • Only 2.3% of total cells have neighbor list with < 10 cells • Average size of neighbor list is 70 – this is too huge • This is mostly created/recommended by ANR • Recommendation • List down all cells with > 100 relation • Use per relation HO counters to detect 0 attempt • Delete the relation when the distance is justified • High HO attempt between distant cells may indicate cell overshooting
Slide 17
Summary Observations and Recommendations CSFB (1 of 2) Auth. and Identity Req. in all RAU • Observations • Authentication and Identity request procedure being performed for each RAU during CSFB call • Increases the overall RAU delay. • Longer RAU delay will result in longer data interruption in case of connected mode CSFB call.
• Recommendation • Reduce the frequency of authentication procedure and Identity Request Procedure during RAU Slide
Auth. in all TAU
Alerting after RB Setup
• Observations • Authentication procedure being performed in all TAU after CSFB call • Authentication procedure increase the TAU delay. • UE will not be reachable for incoming calls during TAU
• Observation • In 39% calls only network sent “signal” IE in the SETUP msg. resulting in UE sending NAS ALERTING before radio bearer setup • This feature significantly improved Call setup performance
• Recommendation • Reduce the frequency of authentication procedure during TAU after CSFB call
• Recommendation • Alerting before radio bearer setup feature should be implemented for all cells to improve M2M and MT CSFB and WCDMA CS voice call setup
Slide
Slide 18
Summary Observations and Recommendations CSFB (2 of 2) FlashCSFB or Release9 based redirection
CSFB degradation due to poor W Ec/Io
No target redirection Frequency in release message
• Observations • Release 8 redirection based CSFB with DMCR implemented • UE still need to read mandatory SIBs in WCDMA • ~400 ms SIB read time observed
• Observations • One MO call setup failure due to RRC connection setup failure in very poor Ec/Io in WCDMA • One MT call drop due to very Ec/Io in WCDMA • Instances of longer all setup due to delayed RRC connection setup in poor Ec/Io in WCDMA • UE not able to target frequency due to poor Ec/Io and CSFB call initiated on another frequency
• Observation • One instance of no LTE to WCDMA redirection frequency • 6 instance of no WCDMA to LTE redirection frequency after CSFB call • Results in significantly longer return to LTE time
• Recommendation • Release 9 based redirection or the Huawei FlashCSFB feature • WCDMA cell PSCs and their associated System Information included in the redirection message to faster camping in WCDMA
Slide
• Recommendation • Investigate the reason for not including redirection frequency in some release messages
• Recommendation • Optimize poor Ec/Io areas in WCDMA for improved CSFB and even WCDMA CS call performance Slide
Slide
19
Summary Observations and Recommendations Counters Based Analysis
Accessibility & Drop
• Observations • Major reason of ERAB failures are attributed by TNL rejection at 11 sites • Lampsite -cover a big church at Kota Kasablanka- every Sunday noon causing RRC success rate degradation (when users > 400) • Major reason of abnormal releases (drop) are attributed to RF and handover failure • Recommendation • Troubleshooting the transmission issue at 11 sites • Lower inactivity timer at Kota Kasablanka, or adding more cells
Slide
Radio Condition
• Observation • Most of indoor cells do not support MIMO due to DAS limitation • 5 macro cells with 0% 2x2 usage • High PDCCH CCE aggregation level in some cells indicating poor radio condition • Recommendation • Upgrade indoor DAS systems for two antenna. • Future DAS deployments should be planned with 2x2 MIMO support • Investigate 5 Macro cells with 0% 2 TB usage Slide 20
LTE Idle Mode Mobility Performance
21
Idle Mode Performance Reselection Procedure Idle Mode Procedures
Power On
System Access (Registration or Data transfer)
PLMN Selection/ Initial camping
Idle Not Camped
Connected Mode Procedures
Connected
Idle Camped
Connection Release (Dormancy etc.)
Loss of Coverage
Radio Link Failure
22
Idle Mobility Performance -84.7 dBm
109
Avg RSRP (95-tile -100dBm)
Intra-LTE Cell Reselections
-10 dB
1.8%
Avg RSRQ (95-tile -15dB)
Reselection Failures
11 dB
1.8%
Avg SINR
SIB Reading Failures
8.4 dB RSRP Delta After Reselection
Idle Mobility KPIs
Radio Statistcs
Key Highlights
0.0% Out of Service Occurrences 23
Idle Mobility Performance RSRP Plot RSRP Distribution Frequency
Cumulative (%)
8000
100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0%
6000 4000 2000 0 -130
-120
-110
-100
-90
-80
-70
-60
RSRP (above this level)
94% samples are above -100 dBm (outdoor) 69% samples are above -90 dBm (outdoor) RSRP is acceptable from drive test Some spots with poor RSRP (indicated in red) needs to be checked 24
Idle Mobility Performance RSRQ Plot RSRQ Distribution Frequency
Cumulative (%)
14000
100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0%
12000 10000 8000
6000 4000 2000 0 -30
-20
-15
-10
-5
RSRQ (above this level)
97% RSRQ samples are above -15 dB (outdoor) Only 57% RSRQ sample is above -10 dB (outdoor)
25
Idle Mobility Performance SINR Plot SINR Distribution Frequency
Cumulative (%)
10000
100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0%
8000 6000 4000 2000 0 -30
-10
0
10
20
30
SINR (above this level)
Around 9% SINR samples are below 0 dB (outdoor) 99.6% SINR sample is above -10 dB (outdoor)
26
Idle Mobility Performance High RSRP (above -90 dBm), but Low SINR(below 0 dB) RSRP
SINR
Some areas with low SINR are actually having high RSRP. This is highly associated with good coverage, but high interference. With poor SINR, DL throughput will be impacted negatively. RF Optimization is recommended for these sites/areas.
27
Idle Mobility Performance RRC State UE only stays at IDLE_CAMPED state for ~61%% of the time. ~39% of the time UE was in RRC_CONNECTED state −
When UE is already in RRC_CONNECTED, handover to a new cell will reset inactivity timer, hence prolonging the time UE stays in RRC_CONNECTED state
Inactivity timer is set to 20 seconds, i.e. once UE goes to connected state, network needs to wait for 20 seconds of inactivity before releasing the RRC connection – too long MO
Parameter
Current
QC View
RRCCONNSTATETIMER
UeInactiveTimer
20
10
Long Inactivity timer
Short Inactivity timer • • • •
Earlier RRC connection release Less radio resources occupied More RRC connection setups for bursty traffic Longer UE battery life
• • •
UE stays longer in Connected state Less frequent RRC connection setup Shorter UE battery life
28
Intra-LTE Cell Reselection Flow Cell ‘s’ must satisfy criterion S: S = Srxlev = {Qmeas,s – (Qrxlevmin + Qrxlevminoffset) – Pcomp*} > 0
Pcomp* = max(PMAX – PPowerClass,0)
UE is Camped (Suitable cell, S) Measured RSRP (Rel. 8) Obtained in SIB1 Obtained in SIB3 Obtained in SIB4
Cell ‘n’ must satisfy criterion S: S = Srxlev = {Qmeas,n – (Qrxlevmin + Qrxlevminoffset) – Pcomp*} > 0
Sintrasearch Included?
NO
Perform Measurements
Rn > Rs for Treselection ?
NO
Rs = Qmeas,s + Qhyst
YES
Rn = Qmeas,n - Qoffset YES
SServingCell > Sintrasearch
NO
Perform Reselection**
** Only if at least 1 sec has elapsed since camping on serving cell 29
Scenario Comparison LTE Intra-Frequency Cell Reselection TSEL Settings
• q-RxLevMin = -128 dBm • s-IntraSearch = 58 dB
TSEL Settings
• q-Hyst = 4 dB • T-ReselectionEUTRA = 1s
When to start cell reselection measurements? SServingCell ≤ Sintrasearch LTE serving cell RSRP ≤ -70 dB
When to perform intra-frequency reselection?
Rn > Rs for 1 s Qmeas,n > Qmeas,s + 4dB
Qualcomm Recommendations
• q-RxLevMin = -124 dBm • s-IntraSearch = 44 dB
Qualcomm Recommendations
• q-Hyst = 4 dB • T-ReselectionEUTRA = 2s
When to start cell reselection measurements? SServingCell ≤ Sintrasearch LTE serving cell RSRP ≤ -80 dB
When to perform intra-frequency reselection?
Conclusion
With current settings, UE will start intra frequency cell search very early, even when serving cell is still very good This is decreasing UE battery life stand by time
Conclusion It is recommended to increase the Treselection to 2 secs to avoid Ping-Pong reselections.
Rn > Rs for 2 s Qmeas,n > Qmeas,s + 4dB
A higher q-OffsetCell value is recommended for cells situated at Tracking Area borders. Tradeoff however is that TAU signaling is reduced but with UE camped on a cell that is not the best.
30
Intra-LTE Cell Reselection Parameters RRC Parameter
Huawei Parameter
Current
QC View
q-RxLevMin
QRxLevMin
-128 dBm
-124 dBm
(29)
(22)
58dB
(44dB)
s-IntraSearch
Comments •
Based on field observation, UE experience (throughput) in LTE with RSRP < -124 dBm is worse compared to when UE is in WCDMA, therefore QC recommends to set this value to -124 dBm
• •
With current settings, the UE will start the Intra frequency cell search very early at -70 dBm; even when the serving cell is still very good, thereby wasting idle mode current and decreasing the UE battery stand-by time QC recommends to start intra-frequency search when RSRP falls below -80 dBm
•
It is recommended to increase the T-reselection to 2 seconds to avoid ping-pong reselections
SintraSearch
Qqualmin
QQualMin
-18 dB
-18dB
q-Hyst
Qhyst
4 dB
4 dB
t-ReselectionEUTRA
TReselEutran
1s
2s
31
Idle Mobility Performance Observed Failure - SIB Read Failure Causing Cell Reselection Failure Basic flow for reselection procedure: LTE Network
UE New Cell Indication: Reselection
UE reselection to the new cell based on the measurements
SIB Broadcasting
eNodeB sends the MIB/SIB information in the PBCH/PDSCH
SIB Read Failure
PBCH/PDSCH decoding failed, UE cant read the SIB information for the new cell
PBCH Decoding failed
Cell Reselection Failure
New Cell Indication: Reselection to new cell
SIB decoding failure can lead to cell reselection failure
UE ends up reselecting to a new cell
32
Idle Mobility Performance Observed Failure – SIB Read Failure Causing Cell Reselection Failure (1) 1
UE is camping on PCI 115
2
3
UE eventually declares Reselection Failure
4
UE then reselects to PCI 34
RF is poor. UE can’t decode PBCH 3 times
Observed 2 times in different locations. Both due to poor RF condition
33
Spurious Paging
UE receives page for PS data even when data is disabled on UE
UE releases call after 20s on inactivity Spurious pages from the network for causing UE to frequently transitioning to connected mode Frequent Connected Mode Transitions will significantly reduce UE battery life and impact User experience
34
IP sources for the pages Investigate if these incoming data to the UE are genuine
IP 31.13.78.36 74.82.89.32
High paging to the UE observed in other market also and addresses by implementing firewall policy to book spurious incoming packets
23.220.203.24 74.125.68.97 216.58.199.202 31.13.78.13 125.160.18.59 74.125.68.97 74.82.89.118 74.125.68.95
Source Google singapore telecommunication blackbery facebook google facebook PT telekom Indonesia google blackberry google 35
Implicit Detach Due to Spurious Paging UE receives page for PS data even when data is disabled on UE
Network sent service reject with cause implicit detach. UE has to initiate attach procedure to register with the network again. This will cause high registration load in the Network Genuine CS pages for the UE can be missed to frequent detach from the network 36
Idle Mode Activity Telkomsel Users stays in connected mode longer compared to Indosat in same location same UE when data is enabled and no activity is initiated by user Indosat
Telkomsel
Total paging messages observed by UE (including pages for other UEs)
29
509
Time Spent in connected mode
16%
96%
Indosat
Telkomsel
1.2
1.2
1
1
0.8
0.8
0.6
0.6
0.4
0.4
0.2
0.2
0
0
37
LTE Downlink Performance
38
DL Throughput- Stationary
39
Theoretical LTE DL Throughput What to expect in “ideal” scenario for Cat.4 UE?
10MHz Assumptions − − − − − − −
MAC Header – 3Bytes RLC Header – 2Bytes PDCP Header – 2Bytes TCP Header – 32Bytes IP Header – 20Bytes MTU – 1500Bytes Always 2TB transmitted
Configuration
15 MHz 10MHz
15MHz
DL Cat4
DL Cat4
MIMO
2x2
2x2
Max MCS – DL
28
28
BLER Target
10%
10%
Scheduling Rate
100%
100%
UE Category
40
Stationary Near Cell DL Throughput Performance Downlink Statistics KPI (Average Value)
Pacific Place (Indoor Cell)
Jak TV (Macro Cell)
Central Park (Indoor Cell)
Senayan City (Lamp Site)
PCI
479
81
436
474
Transmission Mode
TM1
TM3
TM3
TM3
Bandwidth
15 MHz
10 MHz
15 MHz
15 MHz
RSRP [dBm]
-88.7
-65.7
-65.7
-74.7
RSRQ [dBm]
-6.2
-9.5
-9.6
-8.6
SINR [dB]
24.1
19.8
21
21
Wideband CQI [#]
15
11.7
14.4
13.3
Rank Request [#]
1
1.9
1
1.94
DL MCS [#]
27.1
23.4
26.7
25.9
−
Only 40 Mbps average DL throughput was observed
DL Scheduling Rate [%] in time domain
95.8
91.4
93.6
94
−
No. of DL RB scheduled [#]
71.5
41.5
68.6
56.6
The main limiting factor was UE unable to report Rank 2, despite TM3 being configured.
DL BLER [%]
0.45
7.9
4.4
8.7
MIMO 2 CW Rate [%]
0
91.8
0
98.2
−
Only ~60 Mbps average DL throughput was observed.
Max DL Throughput (Mbps)
54.8
67.7
55.1
110.2
−
L1 DL Throughput [Mbps]
48.1
34.3
40.3
60.8
Low number of RB allocation and slightly lower CQI are limiting UE from achieving optimum throughput
Pacific Place −
48 Mbps average DL throughput was observed
−
The main limiting factor is the “no MIMO” configuration – TM1 only.
−
Average CQI of 15 was reported
Jak TV −
~34 Mbps average DL throughput
−
Main limiting factor was low CQI caused by low SINR
Central Park
Senayan City
41
Stationary Near Cell DL Throughput Performance DL Throughput Performance – Pacific Place (Indoor Cell) RB Allocation 500
MCS 100%
800
100%
700
400
80%
80%
600
500
60%
400
300
60%
40%
300 200
200
40%
20%
100 0
0% 19
100
20
21
22
23
24
25
26
27
28
20%
CQI 0
0%
25000 20000
Throughput without MIMO (1 antenna) reached up to 55 Mbps
15000
−
High RB allocation with 70 RBs and above were allocated 83% of the time
−
CQI is perfect – 15 the whole time
5000
−
MCS 28 is used - 57% of the time
0
10000
15 42
Stationary Near Cell DL Throughput Performance DL Throughput Performance – Jak TV (Macro Cell) RB Allocation 100
MCS 100%
70
100%
60
80%
60%
80%
50 40
60%
30
40%
20
40%
20%
0
20%
10 0
0% 16
18
19
20
21
22
23
24
25
26
27
28
CQI
0% 1600
100%
1400
Avg. Throughput around ~34 Mbps with TM3 and 10 MHz − − − −
45 RBs and above were allocated ~68% of the time CQI is quite low - CQI 11 (32%) and CQI 12 (30%) are used the most MCS is low with 88% of the time below 27 and MCS 24 is used the most RF is the main limiting factor – low CQI leading to low MCS
80%
1200 1000
60%
800 40%
600 400
20%
200 0
0% 9
10
11
12
13
14
15 43
Stationary Near Cell DL Throughput Performance DL Throughput Performance – Central Park (Indoor Cell) MCS
RB Allocation 1400
100%
3500
100%
3000
1200 80% 1000 60%
800 600
40%
400
80%
2500 2000
60%
1500
40%
1000 20%
500 20%
200
0
0% 0
0
1
2
4
11
17
18
20
21
22
23
24
25
26
27
28
0%
CQI
RI
70000
Average throughput of 40 Mbps with TM3 and 15 MHz −
70 RBs and above were allocated 70% of the time
−
CQI is varying, but mostly still 15 reported – 72% of the time
−
MCS 27 is used the most (54%), while MCS 28 is only 22%
−
The main limiting factor is UE only reports RI = 1 the whole time
100%
1000
100%
80%
800
80%
40000
60%
600
60%
30000
40%
400
40%
20%
200
20%
60000 50000
20000 10000 0
0% 12
13
14
15
0
0% 1 44
Stationary Near Cell DL Throughput Performance DL Throughput Performance – Senayan City (Lamp Site) RB Allocation
MCS
250
100%
200
80%
1200
100%
1000
80%
800 60% 150
60%
600 40%
100
40%
400 20%
200
50
20%
0
0% 11
0
12
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
0%
CQI
Average throughput of ~60 Mbps with TM3 and 15 MHz
25000
100%
20000
80%
−
70 RBs and above were allocated only 20% of the time
15000
60%
−
CQI is sub-optimal – mostly 14 (39% of the time)
10000
40%
−
MCS 27 is used the most (37%), while MCS 28 is only 19%
5000
20%
−
Low number of RB and slightly lower CQI are the main limiting factor
0
0% 8
9
10
11
12
13
14
15 45
Stationary Far Cell DL Throughput Performance Downlink Statistics KPI (Average Value)
Pacific Place (Macro Cell)
Senayan City (Lamp Site)
PCI
84
474
Transmission Mode
TM3
TM3
Bandwidth
10 MHz
15 MHz
RSRP [dBm]
-107.4
-110.6
RSRQ [dBm]
-11.4
-11.2
SINR [dB]
4.9
5.2
Wideband CQI [#]
7.7
6
Rank Request [#]
1.27
1.92
DL MCS [#]
12.6
9.1
DL Scheduling Rate [%] in time domain
68.8
98.6
No. of DL RB scheduled [#]
27.5
72.5
DL BLER [%]
8.9
8.8
MIMO 2 TB Rate [%]
28.5
88.9
Max DL Throughput [Mbps]
20.1
32.6
L1 DL Throughput [Mbps]
4.8
18.4
Pacific Place −
Average of 4.8 Mbps DL Throughput was observed.
−
Scheduling rate and number of RB allocated were observed to be quite low (very likely due to high number of users in the area).
Senayan City −
Average of 18.4 Mbps DL throughput was observed despite lower MCS, CQI.
−
Good throughput even in far cell
−
Cell is very low-loaded (high number of RBs allocated and high scheduling rate)
46
Stationary Far Cell DL Throughput Performance DL Throughput Performance – Pacific Place RB Allocation 200
MCS 100%
500
80%
400
CQI 100%
450
100
60%
250 40% 20%
200
40.0%
100
20.0%
50
50 0
0% 1
0
60.0%
250
150
150 100
20%
80.0%
350 300
300 200
40%
100.0%
400 80%
350
60%
450
3
5
7
9
11
13
15
17
19 21 23
0
0.0% 4
5
6
7
8
9
10
11
0%
Frame Usage in Time Domain (%) 700
Average throughput of ~4.8 Mbps with TM3 and 10 MHz
600 500
100% 80%
−
70% of the time UE is only allocated with ≤ 30 RBs
400
60%
300
−
40%
Low CQI and MCS is expected as UE is in far cell
200
−
100
Low scheduling in both frequency and time domain are the main limiting factors – Cell is highly loaded at this location
0
20% 0%
47
Stationary Far Cell DL Throughput Performance DL Throughput Performance – Senayan City RB Allocation 3500
100%
3000
80%
2500
60%
2000 1500
40%
1000 20%
500
CQI
MCS 2000 1800 1600 1400 1200 1000 800 600 400 200 0
100% 80% 60%
100.0%
5000
80.0%
4000
60.0%
3000 40% 20% 0% 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
0
6000
40.0%
2000
20.0%
1000 0
0.0% 4
5
6
7
8
9
0%
Frame Usage in Time Domain (%) 7000
Average throughput of ~18 Mbps with TM3 and 15 MHz − −
6000 5000
100% 80%
Cell loading is low as can be seen from the high scheduling in the frequency domain (High RBs) and time domain (High Frame usage)
4000
60%
3000
40%
Low CQI and MCS is expected as UE is in far cell
1000
2000 0
20% 0%
48
MultiUE Simultaneous DL Test PostPaid Vs PrePaid
The total scheduling is only about 64.5%. Thus, there are others user sharing the LTE resource. The scheduler tend to share the LTE in both time and frequency domain. Due to different QCI used, postpaid scheduling rate is higher than prepaid but not very obvious. The overall scheduling rate is 6.38% more for postpaid. The throughput result in Postpaid is 34.23Mbps, while Prepaid is 29.59Mbps. 49
DL Throughput -Mobility
50
Mobility DL Throughput Performance Key Highlights – Downlink Golden Triangle
88%
L1 Throughput (Max 75Mbps)
Avg Schedule Rate
41.3
1.62
Avg RB Number (Max 50)
Avg Rank Indicator
-85.5 dBm
10.3
Avg RSRP
Avg Wideband CQI
16.2
Downlink Throughput
Downlink Throughput
18.5 Mbps
Avg DL MCS 51
Mobility DL Throughput Performance Downlink Statistics – Jakarta Golden Triangle *Out of quota KPI (Average Value)
Golden Triangle
RSRP [dBm]
-85.7
RSRQ [dBm]
-10.6
SINR [dB]
12
Wideband CQI [#]
10.3
Rank Request [#]
1.62
DL Throughput Distribution Frequency
Cumulative (%)
28000
100% 90%
24000
62% of throughput samples are > 10 Mbps
20000
16.3
DL Scheduling Rate [%] in time domain
88.4
No. of DL RB scheduled [#]
41.5
DL BLER [%]
8.7
MIMO 2 TB Rate [%]
59.7
Max DL Throughput [Mbps]
73.4
L1 DL Throughput [Mbps]
18.7
*Avg. driving speed = 40 – 60 km/h
70% 60%
16000
DL MCS [#]
80%
50% 12000
40% 30%
8000
20% 4000
10%
0
0%
1
5
10 15 20 30 40 Mbps (Below the value)
50
100
52
Mobility DL Throughput Performance CQI vs MCS – Golden Triangle MCS Frequency
CQI Cumulative (%)
6000
Frequency 100%
Cumulative (%)
10000
100%
90% 5000
80%
90% 16QAM
8000
70%
4000
60%
80% 70%
QPSK 6000
60% 64QAM
3000
50%
50% 40%
2000
4000
40% 30%
30% 20%
1000
2000
20% 10%
10% 0
0% 0
1
2
3
4
5
6
7
8
9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28
High MCS 27 utilization observed
0
0% 0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
58% of the time CQI is less than or equal to 10 53
Mobility DL Throughput Performance Number of RBs vs Throughput – Golden Triangle Number of DL RBs Frequency
30000
Cumulative (%) 100%
65% of samples with DL RB > 40
25000
90% 80% 70% 60%
20000
50% 15000
40% 30%
10000
25000
DL Throughput (Kbps)
35000
30000
Number of DL RBs vs Avg. Throughput
20000
15000
10000
20% 5000 10% 0
5000
0% 0 1
High # of RBs for heavy downlink user
3
5
7
9
11
13
15
17
19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49
Good correlation between number of RBs and DL throughput 54
Mobility DL Throughput Performance MIMO 2 CW and 64QAM Utilization – Golden Triangle 64QAM
2CW MIMO, 64QAM vs CQI 100
28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
90 80 70 60 50 40
2CW Usage < 50%
30 20 10 0 0
1
2
3
4
5
6
7
Avg. 2CW Rate (%)
8
9
10
11
12
13
14
−
64QAM is enabled when MCS > 16 is used.
−
On average, MCS>16 is used only when CQI is 11 and above
2 Code Word MIMO −
When CQI is better, then 2 CW MIMO usage also increases
−
Less than 50% usage of 2CW MIMO is observed when CQI is below 9
Higher CQI is proportional with higher MCS usage and higher % of MIMO spatial multiplexing usage
15
Avg. MCS 55
Mobility DL Throughput Performance Key Highlights – Downlink Inner Ring Road
92%
L1 Throughput (Max 75Mbps)
Avg Schedule Rate
45.8
1.67
Avg RB Number (Max 50)
Avg Rank Indicator
-83.6 dBm
10.1
Avg RSRP
Avg Wideband CQI
15.9
Downlink Throughput
Downlink Throughput
21.2 Mbps
Avg DL MCS 56
Mobility DL Throughput Performance Downlink Statistics – Jakarta Inner Ring Road Highway *Out of quota KPI (Average Value)
Golden Triangle
RSRP [dBm]
-83.6
RSRQ [dBm]
-10.5
SINR [dB]
11.7
Wideband CQI [#]
10.1
Rank Request [#]
1.67
DL MCS [#]
15.9
DL Scheduling Rate [%] in time domain
92.8
DL Throughput Distribution Frequency
Cumulative (%)
12000
100% 90%
10000
71% of throughput samples are > 10 Mbps
8000
45.8
DL BLER [%]
8.9
MIMO 2 TB Rate [%]
63.1
Max DL Throughput
73.4
L1 DL Throughput [Mbps]
21.3
*Avg. driving speed = 60 – 80 km/h
70% 60%
6000
50% 40%
4000
No. of DL RB scheduled [#]
80%
30% 20%
2000
10% 0
0%
1
5
10 15 20 30 40 Mbps (Below the value)
50
100
57
Mobility DL Throughput Performance CQI vs MCS – Inner Ring Road Highway MCS Frequency
CQI Cumulative (%)
4000
Frequency 100%
Cumulative (%)
8000
100% 90%
90%
16QAM 80%
80%
22% MCS < 9
3000
6000 70%
70%
QPSK 64QAM
60%
2000
50%
60%
4000
50% 40%
40%
30%
30%
2000
1000
0
20%
20%
10%
10%
0% 0
1
2
3
4
5
6
7
8
9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28
High MCS 27 utilization observed, but low MCS values below 10 are still utilized about 22% of the time
0
0% 0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
59% of the time CQI is less than or equal to 10 58
Mobility DL Throughput Performance Number of RBs vs Throughput – Inner Ring Road Highway Number of DL RBs
45000 40000 35000
25000
Cumulative (%) 100%
85% of samples with DL RB > 40
30000
90% 20000 80% 70% 60%
25000 50% 20000 40% 15000 10000 5000 0
DL Throughput (Kbps)
Frequency
Number of DL RBs vs Avg. Throughput
15000
10000
30% 20%
5000
10% 0% 0 1
High # of RBs for heavy downlink user – not many people are downloading when driving on highway
3
5
7
9
11
13
15
17
19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49
Good correlation between number of RBs and DL throughput 59
Mobility DL Throughput Performance MIMO 2 CW and 64QAM Utilization – Inner Ring Road Highway 64QAM
2CW MIMO, 64QAM vs CQI 100
26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
90 80 70 60 50
2CW Usage < 50%
40 30 20 10 0 1
2
3
4
5
6
7
8
Avg. of 2CW Rate (%)
9
10
11
12
13
14
15
−
64QAM is enabled when MCS > 16 is used.
−
On average, MCS>16 is used only when CQI is 11 and above
2 Code Word MIMO −
When CQI is better, then 2 CW MIMO usage also increases
−
Less than 50% usage of 2CW MIMO is observed when CQI is less than 8
Higher CQI is proportional with higher MCS usage and higher % of MIMO spatial multiplexing usage
Avg. MCS 60
Downlink Performance – CQI - MCS CQI Adjustment – Lower MCS Used Compared to Reported CQI According to specs, CQI > 9 is entitled to use 64QAM 64QAM is used when MCS is > 16 Golden Triangle MCS Allocated for CQI > 9 28%
Highway MCS Allocated for CQI > 9 30%
70%
72%
Above 17
2 = QPSK 4 = 16QAM 6 = 64QAM
Below 17
Above 17
Below 17
From drive test, around 30% of UE reported CQI > 9 is adjusted to use lower modulation than what governed in the specs CQI adjustment is used in the network 61
Downlink Performance – CQI – BLER CQI Adjustment Impacting BLER and Downlink Performance Higher CQI correlates to higher MCS and higher throughput.
DL BLER
Higher MCS in downlink might cause higher BLER due to higher transport block size being transmitted
8.9
8.8
8.7
8.9 Stationary Far Cell DL (POI 1)
In different test scenarios, DL BLER is seen to be around 8-9% with current configuration.
Stationary Far Cell (POI 2) Mobility Inner City (Low Speed)
eNB currently employs conservative BLER target for CQI adjustment.
Mobility Highway (High Speed)
Instead of using fixed target, dynamic BLER target could be trialed to allow higher CQI and higher MCS used – higher DL throughput.
MO CELLALGOSWITCH
CELLALGOSWITCH
Parameter DlVarIBLERtargetSwitch
StepVarySwitch
Current OFF
OFF
QC View
Notes
ON
• Indicates whether to enable the downlink target IBLER adoption. • If this switch is ON, downlink target IBLER is adjusted based on the size of transport blocks (TBs) to improve spectral efficiency – around 10 – 30%. • If this switch is OFF, downlink target IBLER is a fixed value around 10%
ON
• Indicates whether to enable or disable the variable-step-based adjustment algorithm. • OFF - The CQI adjustment step is fixed • ON - The CQI adjustment step is constantly changing based on the difference between the current IBLER value and the target IBLER value
62
Downlink Performance – RBG Allocation Downlink Resource Allocation - Background eNB allocates number of PRBs in the downlink through DCI sent in PDCCH. In order to indicate where these PRBs are located, eNB needs a bitmap. −
Example: 20MHz system has 100 RBs, UE is allocated 15 RBs in the downlink. eNB needs to send 100 bits in every DCI to tell UE where the 15 RBs allocated to that UE are located within the 100 RBs.
In order to reduce overhead for control information (PRB bitmaps), PRBs are translated into Virtual Resource Blocks (VRBs) which are then localized in groups, called Resource Block Group (RBG). Telkomsel
Resource Block Groups (RBG) for Resource Block Allocation Type 0 63
Downlink Performance – RBG Allocation Downlink Resource Allocation – Field Observation With mostly 10 MHz system, TSEL has 17 RBGs with size 3 RBG 0 VRB 0
VRB 1
RBG 1 VRB 2
VRB 3
VRB 4
RBG 15
RBG 2 VRB 5
VRB 6
VRB 7
VRB 8
…
VRB 45
VRB 46
RBG 16 VRB 47
VRB 48
VRB 49
*The last RBG may have a size that is less than other RBGs in some situations
The bitmap is called Resource Indication Value (RIV). Example from the field.
17 bits RIV = 15 – 0 0000 0000 0000 1111 RBG 13, 14, 15, 16
UE is allocated 11 RBs in the last 4 RBGs spanning from PRB 39 – 49 as indicated in RIV = 15 in DCI received in PDCCH 64
Downlink Performance – RBG Allocation Downlink Resource Allocation – Allocation Strategy If the number of RB required is not that of an integral number of RBG size, the allocation is defined according to Huawei Specific parameter RbgAllocStrategy Value
Notes If the number of required RBs is less than that of one RBG, RBs are allocated to the scheduled UE as required, which is specified by resource allocation type 1.
ROUND_DOWN (Current Settings)
If the number of required RBGs is greater than N but less than N+1 (N is greater than or equal to 1), RBs of N RBGs are allocated to UEs in the current TTI and the other required RBs are allocated to UEs in the next TTI. The number of allocated RBGs is rounded down and an integral number of RBGs are allocated to the scheduled UE. In this situation, RBs are efficiently used but the scheduling times also increase and the DL user rates decrease.
ROUND_UP
The number of allocated RBGs is rounded up and an integral number of RBGs are allocated to the scheduled UE, regardless of whether the number of required RBs is greater or less than that of one RBG.
ADAPTIVE RBG allocation provides higher DL rates due to higher number of RBs allocated, while not wasting RB resources when UE requires RB below RBG size
In this situation, a few RBs are wasted but the scheduling times also decrease and the DL user rates increase. If the number of required RBs is less than that of one RBG, RBs are allocated to the scheduled UE as required, which is specified by resource allocation type 1.
ADAPTIVE (Recommended)
If the number of required RBs is greater than that of one RBG, the number of allocated RBGs is rounded up and an integral number of RBGs are allocated to the scheduled UE. Compared with RBG round-up, this mode prevents RB waste when the number of required RBs is less than that of one RBG.
In unloaded network like Telkomsel , ROUND_DOWN is not necessary as this leads to lower RB allocation and lower throughput 65
Connected Mode Handover Ping Pong Case Study AS PCI 85 RSCP decrease and PCI 84 RSCP increase UE performs an handover from PCI 85 to 84 Multiple ping pong handovers in short duration as very small A3Offset and Hysterisis − −
Current: RSRPNeighbor > RSRPServing +A3Offset+Hysterisis RSRPNeighbor > RSRPServing + 1 + 1 dB Recommended RSRPNeighbor > RSRPServing + 2 + 1 dB
-70
85.2
Serving Cell PCI
85
-75
84.8
RSRP
84.6 -85 84.4 -90 84.2 -95
-100
84
Coverage overlap region
83.8
Time Cell 84 EARFCN 1875
Cell 85 EARFCN 1875
Serving Cell ID
Serving Cell PCI
-80
RSRP SOURCE TARGET BEFOR PCI PCI E HO 85 84 -80.3
RSRP AFTER HO -82.5
84
85
-85.1
-81.2
85
84
-81.6
-80.2
84
85
-81.4
-82.1
85
84
-83.1
-81.0
85
85
-81.8
-82.0
85
84
-81.4
-81.3 66
Connected Mode Mobility – Intra LTE Handover Basic Overview of HO Implementation in Telkomsel Coverage based intra-frequency handover is used – based on RSRP With only 1 LTE frequency (DL EARFCN 1875), only LTE Intra-frequency handover available
Intra-LTE Handover
Measurement • UE measures neighbor cells based on given configuration • UE generates candidate cells list based on measurement
Handover Triggering • LTE Intra-frequency handover is triggered by event A3
Handover Decision
Handover Execution
• eNodeB checks the cells in candidate list
• eNodeB governs the UE handover procedure to target cell
• eNodeB decides to which cells UE needs to be handed over
67
Intra-LTE Handover Triggering Handover Triggered by Event A3 1
RSRPServ < S-measure • Start LTE neighbor measurement
2
RSRPServ + A3offset < RSRPNei - Hyst *In TSEL, Frequency offset & cell specific offset is set to 0
• A3 Triggering condition is fulfilled • Wait for Time to Trigger before sending measurement report 3
*Note: A3 leaving condition: RSRPServ + A3offset < RSRPNei + Hyst
After TTT, neighbor is still better • Send event A3 measurement report • Wait for reporting interval before repeating the measurement report
If the leaving condition is met, UE no longer report event A3 68
Intra-Frequency Handover – Event A3 (1 of 2) Parameter a3-Offset
timeToTrigger (A3)
MO IntraFreqHoGroup
IntraFreqHoGroup
hysteresis (A3)
IntraFreqHoGroup
S-Measure
HoMeasComm
Allowed Range
Current
QC View
(2)
(4)
1 dB
2 dB
(8)
(8)
320ms
320ms
(2)
(2)
1 dB
1 dB
IntraFreqHoA3Offset
Comments • •
Actual value = IE value * 0.5 dB 1dB along with hysteresis of 1 dB becomes equivalent to 2dB effective hysteresis, which might be too low to avoid HO ping-pong in low mobility scenario
•
Actual value = IE value * 0.5 dB
•
If the signal quality of the serving cell exceeds this threshold, the UE is not required to perform intra-frequency, inter-frequency, or inter-RAT measurements, leading to reduced power consumption.
•
If this parameter is set to True, the UE will continue reporting measurements for a cell that meets the event A3 leaving criteria (a cell that is not suitable for handover). If it is set to False, the UE will not report measurements for a cell that meets the event A3 leaving criteria.
IntraFreqHoA3TimeToTrig
IntraFreqHoA3Hyst
60 SMeasure
n/a (-80dBm)
reportOnLeave
-
-
FALSE
FALSE •
69
Intra-Frequency Handover – Event A3 (2 of 2) Parameter
MO
reportInterval (A3)
IntraRatHoComm
reportAmount (A3) maxReportCells filterCoefficientRSRP
filterCoefficientRSRQ
T304
IntraRatHoComm IntraRatHoComm
HoMeasComm
HoMeasComm
RrcConnStateTimer
Huawei Parameter
Current
QC View
(1)
(2)
240ms
480ms
(7)
(7)
Infinity
Infinity
4
4 to 6
(6)
(8 – 11)
Fc6
Fc8-11
(6)
(8 – 11)
Fc6
Fc8-11
IntraFreqHoRprtInterval
IntraRatHoRprtAmount
IntraRatHoMaxRprtCell
EutranFilterCoeffRsrp
EutranFilterCoeffRsrq
(4)
(5)
500ms
1000ms
Comments • •
Indicates the interval between periodic reports Lower value may increase signaling load – still fine with current network load, but may be revisited in the future.
•
Represents number of times a measurement report is sent
• •
Consider ability of eNodeB to utilize these reports Message length needs to be decoded by eNodeB
• If this value is set too low, measurement reports could be triggered by rapid, temporary, short term fluctuations in RSRP. • If this is set too large, then the generation of measurements reports will be delayed even though a more suitable cell is available.
• •
T304ForEutran •
Timer running while UE attempts to complete an LTE HO If the parameter is set too low, it may result in some failed HOs in case there is insufficient time to complete the HO (preparation, target cell RACH/contention resolution). If the parameter is set too high, it may result in the UE waiting too long for HO to complete when it may be suitable to trigger RLF and re-establishment.
70
User Uplink Performance
71
UL Throughput - Stationary
72
Theoretical LTE UL Throughput What to expect in “ideal” scenario for Cat.4 UE?
10 MHz Assuming
15 MHz
UL Configurations
Value
Value
LTE System bandwidth (MHz)
10
15
UE Category
Cat4
Cat4
−
MAC Header-3 bytes
−
RLC Header-2 bytes
−
PDCP Header-2 bytes
# TB
1
1
−
TCP Header-32 bytes
Max MCS
24
24
−
IP Header-20 bytes
BLER Target
10%
10%
−
MTU -1500 bytes
Scheduling Rate
100%
100%
−
PUCCH 2 RBs
73
Stationary Near Cell UL Throughput Performance Uplink Statistics Jak TV (Macro Cell)
KPI (Average Value)
Jak TV (Macro Cell)
Senayan City (Lamp Site)
PCI
81
474
−
~23 Mbps average UL throughput was observed.
Bandwidth
10 MHz
15 MHz
−
RSRP [dBm]
-66.9
-71.3
Good UL performance close to the maximum theoretical UL throughput.
RSRQ [dBm]
-7.8
-6.5
−
Reported BSR Index is not maximum (63).
Avg. DL SINR [dB]
19.2
25
UL TX Power [dBm]
4.85
-8.7
UL Power Headroom [dB]
16
26.9
−
~35 Mbps average UL throughput was observed.
Pathloss [dB]
84.5
64.2
−
BSR Index [#]
61
62
Number of RB is sub-optimal and hindering UE from achieving higher throughput in 15 MHz system.
Avg. UL MCS [#]
24
24
UL Scheduling Rate [%] in time domain
99.6
99.6
−
UE TX Power is much lower at this location due to lower path loss (PUSCH Power is calculated based on path loss)
No. of UL RB scheduled [#]
41.8
65.6
UL BLER [%]
1.26
4.4
Max UL Throughput (Mbps)
23.2
38.9
L1 UL Throughput [Mbps]
22.8
35.7
Senayan City
74
Stationary Near Cell UL Throughput Performance UL Throughput Performance – Jak TV RB Allocation 1400000
MCS 100%
50000
100%
45000
1200000 80% 1000000
40000
80%
35000
60%
800000
30000
60%
25000
600000
40%
400000
20000
40%
15000 20%
200000
10000
20%
5000 0
0%
0
0% 21
22
23
24
Average throughput of ~22 Mbps with 10 MHz −
UE is using highest MCS of 24 almost 100% of the time
−
UE is also allocated 87% of the time with RBs ≥ 40
−
The near cell UL performance at this location is good 75
Stationary Near Cell UL Throughput Performance UL Throughput Performance – Senayan City MCS
RB Allocation 12000
100%
10000
80%
8000
30000
100%
25000
80%
20000 60%
6000
60% 15000
40% 4000
40% 10000
20%
2000
20%
5000
0
0%
0
0% 21
22
23
24
Average throughput of ~35 Mbps with 15 MHz −
UE is using highest MCS of 24 almost 100% of the time
−
UE is also allocated 98% of the time with RBs ≥ 60
−
The near cell UL performance at this location is good 76
Stationary Far Cell UL Throughput Performance Uplink Statistics KPI (Average Value)
Pacific Place (Indoor Cell)
Senayan City (Lamp Site)
PCI
479
474
Bandwidth
15 MHz
15 MHz
RSRP [dBm]
-87.9
-111.1
RSRQ [dBm]
-3.8
Avg. DL SINR [dB]
Pacific Place −
Although RSRP was good, path loss is high and this location is considered as poor UL coverage
−
TX Power is close to max TX power most of the time
-10
−
UL throughput is averaged ~11 Mbps
23.3
2.6
−
UL TX Power [dBm]
22.5
21.5
The main limiting factor here is the low MCS and lower UL RB allocated (many other users in the area)
DL Pathloss [dB]
104.9
104.7
BSR Index [#]
62
62
Avg. UL MCS [#]
10.3
21.5
UL Scheduling Rate [%] in time domain
99.8
92.9
No. of UL RB scheduled [#]
58.9
61.2
UL BLER [%]
7.6
6.3
Max UL Throughput (Mbps)
16.5
38.3
L1 UL Throughput [Mbps]
10.6
26.6
Senayan City −
~27 Mbps average UL throughput was observed.
−
Far cell performance at this location is good
−
MCS allocation is still high
77
Stationary Near Cell UL Throughput Performance UL Throughput Performance – Pacific Place RB Allocation 60000 50000
MCS 100%
30000
80%
25000
40000
60% 30000
100%
80%
20000 60% 15000
40% 20000
40% 10000
20%
10000
20%
5000
0
0%
0
0% 4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
Average throughput of ~11 Mbps with 10 MHz −
UE is never allocated with 72 RBs (only 64 RBs maximum)
−
Low MCS are allocated as expected in far cell
78
Stationary Far Cell UL Throughput Performance UL Throughput Performance – Senayan City MCS
RB Allocation 40000
100%
35000
35000
100%
30000 80%
80%
30000
25000
25000
60%
20000 40%
15000 10000
20%
5000
60%
20000 15000
40%
10000 20% 5000
0
0% 0
0% 10
12
13
14
15
16
17
18
19
21
22
23
24
Average throughput of ~27 Mbps with 15 MHz −
UE is also allocated 90% of the time with RBs ≥ 60 (unloaded cell)
−
The far cell UL performance at this location is good
79
MultiUE Simultaneous UL Test PostPaid Vs PrePaid
The total scheduling is only about 91.96%. Thus, both UE consumed most of the UL LTE resource. The scheduler tend to share the LTE in both time and frequency domain. Due to different QCI used, postpaid scheduling rate is higher than prepaid but not very obvious. The overall scheduling rate is 5% more for postpaid. The throughput result in Postpaid is 12.03Mbps, while Prepaid is 10.72Mbps. 80
UL Throughput - Mobility
81
Summary Acceptable UL throughput performance. Average performance limited by the other users in the network during drive Areas of poor coverage observed on the drive route resulting poor UL performance Network is able to allocates maximum MCS of 24 and Maximum TB size of 25456 possible for CAT4 device Network performance in uplink limited. Upgrading network to 4 way receive diversity from the current 2-way receive diversity will improve uplink coverage UL scheduler has tendency to allocate lower PRB ranges to user. Will result in higher UL interference in lower PRB ranges − Frequency Selective Scheduling is disabled and Interference Randomization also does not seems to be working − Recommended to enable Frequency Selective and Inference Randomization PRB allocation 82
Summary Very high average PUSCH transmit power observed (18.3 dB). − UE BLER significantly lower than 10 % in low path loss regions. UE using more higher than required power in low path loss regions − Will result in higher UL interference
Very aggressive power control settings (p0-NominalPUSCH= -67 dBm) − It is recommended decrease it to -80 dBm along with alpha value of 0.8
Low A3-Offset and hysteresis values. Multiple Intra frequency handover ping-ponds observed. − Recommended to increase A3-offset from 1 dB to 2 dB and Hysteresis from 0.5 dB to 1 dB
83
Connected Mode UL Mobility Test Golden Triangle Drive – Uplink Statistics Uplink Statistics
Performance
Comments
Avg. Serving cell RSRP [dBm]
-84.2
89% of samples >= -100 dBm
Avg. Serving cell RSRQ [dB]
-9.3
88% of samples >= -12 dB
Avg. DL SINR [dB]
11.8
Avg UL Tx Power [dBm]
18.3
Avg UL Power Headroom [dB]
-0.3
Avg Path loss [dB]
104.6
Avg BSR Index [#]
57.6
Avg UL MCS [#]
18.8
Avg UL Scheduling Rate [%]
90.5
Indicates unloaded network
Avg Num of UL RBs [#]
32.6
67.5% of samples have RBs >= 30
Avg UL BLER [%]
8.1
Avg. UL L1 Throughput [Mbps]
11
87.7% of samples have BSR >50
84
Connected Mode UL Mobility Test Ring Road Drive – Uplink Statistics Uplink Statistics
Performance
Comments
Avg. Serving cell RSRP [dBm]
-83.8
93% of samples >= -100 dBm
Avg. Serving cell RSRQ [dB]
-8.6
91% of samples >= -12 dB
Avg. DL SINR [dB]
11.8
Avg UL Tx Power [dBm]
18.2
Avg UL Power Headroom [dB]
0.2
Avg Path loss [dB]
103.9
Avg BSR Index [#]
58.6
Avg UL MCS [#]
20.1
Avg UL Scheduling Rate [%]
93.5
Indicates unloaded network
Avg Num of UL RBs [#]
39.7
89% of samples have RBs >= 30
Avg UL BLER [%]
8.1
Avg. UL L1 Throughput [Mbps]
14.9
91% of samples have BSR > 50
85
UL Throughput Areas of poor throughput observed on the drive route due to poor outdoor coverage z
PC QL
NL
QL QL
NL
PC
PC PC RSRP Throughput BSR PC: Poor Coverage resulting in low Throughput QL: Prepaid Quota Limit in the SIM resulting in poor Throughput NL: Network Loading resulting in lower RB assignment and poor Throughput
RB Count 86
Drive Route Coverage In Poor Coverage area UE becomes significantly power limited impacting the performance
RSRP
PUSCH Tx Pwr
PHR 87
UL Scheduler Performance
Network Starts decreasing even the RB count as PHR turns even more negative
UE becomes power limited PHR becomes negative MCS and therefore throughput starts decreasing
50 40 30
Average of AVG(Throughput L1 UL 1 Sec)2 Average of AVG(First Tx BLER LTE UL 500ms)
20
Average of AVG(MCS UL) Average of AVG(Power Headroom UL)
10
Average of AVG(RB Count PUSCH) Average of AVG(Tx Power PUSCH)
0 -117 -115 -113 -111 -109 -107 -105 -103 -101 -99 -97 -95 -93 -91 -89 -87 -85 -83 -81 -79 -77 -75 -73 -71 -69 -67 -65 -63 -61 -59 -57 -55 -53 -10 -20
At extremely poor RF conditions Network is not able to maintain the 10% BLER target. Average MCS is 2.5 and RB is 4.7. throughput drops to 228 kbps
UE reaches Average 10% BLER target
88
Uplink Scheduling MCS/RB/TB Size Allocation 0.5
Very good High MCS allocation.
0.45
− 25.5 % samples greater than TB size of 19848 bits − Network not completely unloaded during the drive test
0.8
0.3 0.25
0.6
0.2 0.4
0.15 0.1
0.2
0.05 0
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 28 29 30 31
1.2
MCS Index 30
PDF
0.6 0.1
CDF (%)
0.8
0.15
0.05
0.2
0
0
UL TBS Size (Bits)
PDF (%)
0.4
CDF
120
25
100
20
80
15
60
10
40
5
20
0
CDF (%)
1
0.2
CDF (%)
PCD (%)
0.35
RB availability limiting the TB size allocation
PDF (%)
1
0.4
− 44% MCS 24 allocations
0.25
1.2
0 1
2
3
4
5
6
8
9
10 12 15 16 18 20 24 25 27 30 32 36 40 45 48
RB Allocation
89
Uplink PRB Allocation PRB allocation A Ping test at two neighboring cells was performed to study the UL RB allocation behavior There is tendency by the scheduler to allocate RBs at the edge of the PRB range specifically RBs are allocated towards the lower PRB range. − Can result in high UL interference in the lower PRB ranges as for these PRBs network will encounter very high loading even when the overall network load is low PRB allocation overlap in neighboring PCI UL PRB Allocation PCI 443
35
35
30
30
Allocation Frequency (%)
Interference randomizatio n RB allocation does not seems to be working
Allocation Frequency (%)
Uplink RB Allocation PCI 442
25 20 15 10 5 0
25 20 15 10 5 0
1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 52 55 58 61 64 67 70 73
PRB Number
1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 52 55 58 61 64 67 70 73
PRB Number
90
Uplink PRB Allocation Stratergy UlRbAllocationStrategy: adaptively switches between frequency selective scheduling and interferencerandomization-based scheduling or adaptively switches between frequency selective scheduling and nonfrequency selective scheduling − Currently set to FS_INRANDOM_ADAPTIVE(switches between frequency selective scheduling and interferencerandomization-based scheduling )
RsvdSwPara0_bit28: Frequency Selective Scheduling is enabled or not − Currently set off
InterfRandSwitch: Indicates whether to enable or disable the interference randomize algorithm based on the eCoordinator or eNodeB. If this parameter is set to OFF, the interference randomize algorithm is disabled (This parameter is dedicated to LTE TDD cells. Need to check from Huawei if this has any impact on FDD) − Currently Set to OFF
Recommendation: Enable frequency Selective scheduling and Confirm if interference randomization Scheduling is enabled 91
Uplink Power Control PUSCH/PUCCH Power control Algorithm PPUSCH = min{PCMAX,10 logM + P0_PUSCH + PL + f(i) + TF} [dBm] − − − − − −
− −
PCMAX = min{PEMAX, PUMAX} P0 : Target PSD M : Number of assigned resource blocks : Cell-specific factor TF : Transport format-depending compensation f(i) : Accumulation function or absolute function ( f(x) = x ) PUSCH : Power-control step (”PUSCH TPC command”). Input to f(i). PL : Estimated DL path loss
PUSCH included in Uplink Scheduling Grant
PPUSCH = min {PCMAX,10logM + P0PUSCH + α·PL + f(i)+ΔTF} [dBm]
PPUCCH = min{PCMAX, P0_PUCCH + PL + h( ncqi,nharq) + ΔF_PUCCH(F) + g(i)} − − − − − − −
PCMAX : max UE power accoring to its class or cell restriction P0_PUCCH : Target PSD PL : Estimated DL path loss h(n) : = 0, when normal CP is used FPUCCH : PUCCH format offset g(i) : Accumulation function PUCCH : Power control step (”PUCCH TPC command). Input to g(i)
δPUCCH included in Downlink Scheduling Control (when present) δPUCCH for multiple UEs jointly coded and transmitted on PDCCH −
Used when no Downlink Scheduling Control
PPUCCH = min {PCMAX, P0PUCCH + PL + h(ncqi, nharq) + ΔF_PUCCH + g(i )} [dBm] 92
PO_NOMINAL_PUSCH+PO_UE_PUSCH
PUSCH Power Control
Currently Disables
PPUSCH (i)= min{PCMAX,10 log(MPUSCH(i)) + P0_PUSCH + PL + f(i) + TF } [dBm] Power does not vary with MCS
Power increase with pathloss and gets saturated at max power
Axis PUSCH Tx Pwr (dBm)
25 20 15 10
5 0 -5
65
75
85
95
105
115
125
-10 -15 -20
Observation:
135
PUSCH Tx Pwr (dBm)
30
30 25 20 15 10 5 0 -5 0 -10 -15 -20
5
Avg of PUSCH Tx Pwr
15
20
25
UL MCS Index
Path Loss PUSCH Tx Power
10
PUSCH Tx Power
Avg of PUSCH Tx Pwr
•The PUSCH transmit does not vary based implicitly on the MCS. eNodeB does not scale the PUSCH transmit power based on the UL MCS scheduled via the PDCCH for the UE. Frequent UL power control commands combined with UL HARQ is required to ensure appropriate UL power spectral density and good UL performance. As the Current Implementation has less aggressive eNB controlled Power control, this results in high UE transmit power for all MCS allocation.
Conclusion: •It is recommended to enable UE-specific parameter deltaMCS-Enabled (currently disabled) with Vendor consultation that enables or disables the MCS dependent component of the PUSCH power control. Through Pre-Post Analysis is recommended to verify the impact of this parameter Change. 93
Uplink Power Control Statistics during Uplink data transfer PUCCH/PUSCH Power Control TPC Behavior TPC Count PUCCH
TPC Count PUSCH
TPC (0) 99%
TPC (-1) 1% TPC (-1) TPC (0) • •
TPC (-0) 97%
TPC (3)
TPC (1) 0% TPC (1) TPC (3)
TPC (-1) 1% TPC (-1) TPC (-0)
TPC (1) 2%
TPC (-3) 0% TPC (1) TPC (-3)
eNB sent TPC commands of 0dB during majority of drive testing Closed loop power control limited in use. Given the very high PUSCH power in the entire drive power control in not regulating the transmit power enough 94
PUSCH Tx Power Recommended to trial lower values of PO_NOMINAL_PUSCH = -80 dBm Almost 65% of the time UE was operating with negative PHR Average PUSCH Tx power of 18.3 dBm is very high compared to values observed in even other Huawei Networks PO_NOMINAL_PUSCH set to very high value of -67 dBm
0.7
1.2
0.6
1
0.6
1
0.8
0.5
PDF (%)
0.5 0.4
0.6
0.3
0.4
0.2
0.2
0.1 0
0
PDF (%)
1.2
CDF (%)
0.7
20
0.4 0.6 0.3 0.4
0.2
0.2
0.1
CDF
-120
15 10 5 0 -110
-100
-90
-80
0 -23
PDF
25
0.8
0
PUSCH Tx Pwr
30
PUSCH Tx Pwr (dBm)
− − −
Very infrequent use of TPC commands regulate the PUSCH power results in high PUSCH tx power even in relatively better RF conditions where significant headroom to reduce power as BLRE is very low in these areas Ideally, p0-NominalPUSCH = -174 + 10*log(PUSCH BW) + eNB NF + C/I (function of minimum MCS) + PUSCH RoT Example with some typical values: -174+ 52.5 + 3+ 25 + 3 = -90.5 Using additional margin initially Po_NOMONAL_PUSCH = -80 dBm can trialed
CDF (%)
−
>-23 -20 20 -10 >0 10 ACK) which increases delays and could reduce DL throughput.
deltaF1
deltaF0
If this parameter is too large, the PUCCH Format 2 carrying CQI may be sent at higher than required power and in some cases may cause excessive interference to other users PUCCH transmissions with different formats as well as additional interference to neighboring cells in these PUCCH RBs. If set too low, the CQI bits carried on PUCCH may be detected incorrectly which could negatively impact DL link adaptation (imperfect eNodeB scheduling decisions) and reduce DL throughput.
deltaF2
If set too low the CQI, ACK bits carried on PUCCH may be detected incorrectly which may negatively impact DL link adaptation, cause duplicate DL transmissions/premature HARQ termination and reduce DL throughput. If set too large PUCCH Format 2a carrying CQI, 1 bit ACK/NAK may be sent at higher than required power and in some cases may cause excessive interference to other users PUCCH transmissions
deltaF2
If set too low the CQI, ACK bits carried on PUCCH may be detected incorrectly which may negatively impact DL link adaptation, cause duplicate DL transmissions/premature HARQ termination and reduce DL throughput. If set too large PUCCH Format 2b carrying CQI, 2 bit ACK/NAK may be sent at higher than required power and in some cases may cause excessive interference to other users PUCCH transmissions
deltaF0
deltaF2
deltaF2
96
Connected Mode PUSCH Power Control Parameter Audit SIB-2 UL Power control Parameter Parameter
p0-NominalPUSCH
alpha
deltaMCS-Enabled (Ks)
accumulationEnabled
Allowed Range
(-126…24)
al0, al04, al05, al06, al07,al08, al09, al1
en0, en1 TRUE (enabled) or FALSE (disabled)
Current
-67
al07 (0.7) en0 Disabled TRUE
filterCoefficient
fc6
p0-UE-PUSCH
0
QC View
Comments
-80
Higher setting will improve PUSCH reception, but will also drive higher UE transmit power leading to interference to neighboring cells resulting in lower overall cell-throughput in loaded condition and subsequent PC commands will be needed to adjust UE transmit power. Higher settings will be needed if alpha is set to a very low value so that the base PUSCH power can be increased when there is lack of pathloss compensation. Lower setting may result in UE transmit power starting at a low value during call-setup/after HO causing higher initial PUSCH BLER, increased UL HARQ retransmissions and possibly slower call setup and lower initial UL data rates until PC commands adjust UE power upwards to required level. The UL power could be increased significantly over a certain time-duration using Accumulated PC commands.
al08 (0.8) en1
Full path loss compensation (alpha close to 1) permits higher cell edge data rate maximizing fairness for cell edge UEs but determines lower total uplink capacity. Lower path-loss compensation can increase the total system capacity in the uplink, as less UL power resources are spent ensuring the success of transmissions from cell edge UEs and less inter-cell interference is caused to neighboring cells. However, cell-edge data rate is degraded. If this parameter is disabled, the PUSCH transmit power cannot be varied based implicitly on the MCS and frequent UL power control commands combined with UL HARQ is recommended to ensure appropriate UL power spectral density and good UL performance. If this parameter is enabled, the UL power will be scaled based on MCS
Enabled TRUE fc4 (Default) 0
97
Automatic Neighbor Relation (ANR)
98
PCI Conflict
99
ANR Missing Neighbor Procedure Detecting Missing Neighbor in ANR – Understanding When UE detects strongest neighbor cell B, UE reports cell B to the source eNB.
Source eNB checks whether cell B is in the neighbor list. If it is not in the list, then source eNB will instruct UE to read e-CGI, TAC, and PLMN list of cell B. UE reports e-CGI, TAC, and PLMN to source eNB. −
UE reads e-CGI only during C-DRX cycle.
−
If UE is doing heavy download, data session will have priority and UE will not enter CDRX.
−
It is possible that UE reports empty e-CGI because UE did not enter C-DRX after T321 (1s) has expired.
−
If the reported e-CGI is not in the neighbor list, source eNB will add cell B to its neighbor list and create neighbor relationship between cell A and cell B
Handover to cell B is then executed. 100
PCI Conflict - ANR Neighbor Confusion (1 of 2) eNB Requests UE to Report eCGI of Best Reported Cell 1. UE is camping on PCI 77
3. eNB requests UE to report CGI for PCI 213
4. UE reports CGI for PCI 213
2. PCI 213 is better than serving cell eNB ID 134501
5. Handover to PCI 213
Cell ID 11
Up to this point, we assume PCI 213 is a missing neighbor
101
PCI Conflict - ANR Neighbor Confusion (2 of 2) Multiple Neighbor with Same PCI in The Neighbor List
Neighbor Cell List
Neighbor Relationship Table
PCI 77 has 3 neighbors with PCI 213, out of which only 2 have neighbor relationship
Measurement report only contains PCI information of neighbor cells. If multiple neighbors with same PCI exist in the database, network becomes confused when that PCI is reported. In this case, eNodeB requests CGI reporting from UE when event A3 for neighbor PCI 213 is reported not due to missing neighbor, but simply because eNB is confused, which PCI 213 is being reported by UE. 102
Impact of PCI Conflict – Observation 1 Conflicting PCI is Best Neighbor – No Handover, eventually Radio Link Failure 1. UE reports event A3 for better PCI 213
3. eNB can’t execute handover to PCI 213. The same sequence keeps going
4. PCI 213 is still the best neighbor, while serving cell is very poor at -128 dBm RSRP
Serving RSRP is already at -128 dBm here PCI 213 stays on top of the list as the best neighbor
2. UE is doing heavy data and can’t enter CDRX, hence empty eCGI reporting for PCI 213 5. Radio Link Failure is Inevitable
103
Impact of PCI Conflict – Observation 2 (1/2) UE Stays Longer in Poor Cell Until Another Non-Conflicting Neighbor Becomes Better 3. eNB can’t execute handover to PCI 72. The same sequence keeps going
1. UE reports event A3 for better PCI 72
4. After ~6 seconds, UE detects second PCI 83 is now the best cell
1
Serving RSRP is already 8 dB worse here
2
Throughput performance will be impacted when UE stays longer in poor cell
3 2. UE is doing heavy data and can’t enter CDRX, hence empty eCGI reporting for PCI 72 5. Handover to PCI 83 took place
4 104
Impact of PCI Conflict – Observation 2 (2/2) Throughput Impact (Continuation of Observation 2) DL Throughput Staying in poor serving cell kills UE throughput ( < 1 Mbps)
RSRP UE stays in serving cell with deteriorating RSRP
No. of empty CGI report
UE can’t report eCGI for PCI 72
Only after handover to PCI 83, throughput is recovered
When PCI Conflict happens, UE is requested to report eCGI for best cell in the A3 measurement (PCI 72) During heavy data session, UE might not be able to report eCGI for PCI 72 If UE can’t report eCGI for PCI 72, UE stays in the serving cell where RSRP keeps deteriorating. Handover cannot happen until another PCI with better RSRP than PCI 72 is reported in A3 measurement.
DL Throughput is brought down to 200
Number of Cells
# of Ncells >5 > 10 > 30 > 50 > 100 > 200
Cell Count 6328 6290 5904 3208 1313 275
% 99.0% 98.4% 92.4% 50.2% 20.5% 4.3% 108
Proposed Steps
Fix conflicting PCI neighbor definition 1.
List down all neighbor relation with conflict PCI 2. Keep 1 PCI relation at each source cell and delete remaining relation based on distance 3. Monitor the ANR reporting and per relation HO counters
Long Term: fully utilize the ANR free mode
Reduce Number of Neighbor 1.
List down all cells with > 100 relation 2. Use per relation HO counters to detect 0 attempt 3. Delete the relation when the distance is justified 4. High HO attempt between distant cells may indicate cell overshooting
1.
In long term consider to use ANR with free mode 2. Need proper planning to determine addition / deletion criteria, and creating black list / white list neighbor 3. Combine with other feature like PCI conflict detection and selfoptimization 109
PCI Re-Use
110
Site-to-Site Distance considering Sector Antennas
Closest site
Based on gcell_jabo_31Mar The Site-to-Site Distance evaluation here has considered the Sector Azimuth and 65-degrees antenna beamwidth (assumption) By using the beamwidth angle limitation, this site-to-site distance would be more relevant in determining the most suitable downtilt angle − If the cell uses omni antenna, the site-to-site distance calculated does not consider Ant BW
Distance to the closest site
Not closest
65 deg BW
Not closest
Then the Downtilt Angle could be evaluated based on the Antenna Height and the distance to the closest site − Here we assume it’s flat terrain and antenna height in the Gcell database has incorporated the building height
Overshooting Reference Suitable Closest site 111
PCI Planning and PCI Conflict Same PCI should not be re-used too closely
Neighbor should not have the same PCI − Cannot differentiate the existing cell with the neighbor cell so cannot detect the neighbor cell − High RSRP (summing existing and neighbor cells together) for the PCI assigned − High chances of MIB / SIB read failures − Poor PDSCH SINR due to high interference − High BLER due to over-stated CQI
PCI 20
PCI 20
PCI 20 is very strong
Which PCI 40?
Neighbor of Neighbor cell should not have the same PCI
PCI 40
PCI 20
PCI 40
− Neighbor cell cannot determine which cell it should hand the call over to because the existing cell and the neighbor of neighbor cell use the same PCI 112
PCI Conflict Evaluation Based on gcell_jabo_31Mar
Neighbor should not have the same PCI − Not found in the Gcell database
PCI 20
PCI 20
Neighbor of Neighbor cell should not have the same PCI PCI 20 is very strong
− Some detected instances − 4% Ncell relations with PCI Conflicts − Refer to the ANR Case study
Taking into account these rules, it would be best to have a minimum of 5 tiers of cells before re-using the same PCI
Which PCI 40?
PCI 40
PCI 20
PCI 40
− 5-tiers would be equivalent to 5 x 889 m (median site-to-site distance) ~4.5 km 113
PCI Re-Use Evaluation Based on gcell_jabo_31Mar
Distance to the Closest Cell with the same PCI: − − − − − −
Average distance Min distance Max distance 30%-tile 50%-tile / median 80%-tile
= 12 km = 994 m = 86.2 km = 7.5 km = 9.6 km = 14.6 km
# of same PCI cells with < 4.5 km separation = 201 The table on the right hand side shows the cells with the shortest PCI reuse distance Subsequent slides show two examples covering the top 8 cells in the table
Cell C_JKU794HL_SUKAPURASTPHL3 N_JKT528ML_STOPGILINGANML3 C_JKU901HL_GDINGMDITERNIA2STPHL1 C_JKU901HL_GDINGMDITERNIA2STPHL2 C_JKU901HL_GDINGMDITERNIA2STPHL3 JKP715ML_GUDANGGARAMML1 JKP715ML_GUDANGGARAMML2 JKP715ML_GUDANGGARAMML3 N_JKP641ML_KEMPINSKYML1 N_JKP641ML_KEMPINSKYML2 N_JKP641ML_KEMPINSKYML3 N_JKS870HL_SEMANGGI2AI4THL1 N_JKS870HL_SEMANGGI2AI4THL2 N_JKS870HL_SEMANGGI2AI4THL3 N_KRW052ML_TUPAREVML3 N_KRW601ML_RESINDAKRWML3 JKP010HL_SEMANGGII4THL4 N_JKS081ML_WIJAYAML1 N_JKP039ML_ISTANANEGARAML1 N_JKP039ML_ISTANANEGARAML2 N_JKP039ML_ISTANANEGARAML3 N_JKP564ML_LANDASPACUML1 N_JKP564ML_LANDASPACUML2 N_JKP564ML_LANDASPACUML3 C_JSX028ML_GARUTMENTENGDMTHL1 C_JSX028ML_GARUTMENTENGDMTHL2 C_JSX028ML_GARUTMENTENGDMTHL3 JKP659ML_RSBUDIKEMULIAANML1 JKP659ML_RSBUDIKEMULIAANML2 JKP659ML_RSBUDIKEMULIAANML3
PCI Reuse Distance 0.994 0.994 2.324 2.324 2.324 2.324 2.324 2.324 2.456 2.456 2.456 2.456 2.456 2.456 2.855 2.855 3.199 3.199 3.436 3.436 3.436 3.436 3.436 3.436 3.675 3.675 3.675 3.675 3.675 3.675 114
Closest PCI Re-Use (PCI = 413, EARFCN = 1875) Based on gcell_jabo_31Mar Source Cell (PCI 413): C_JKU794HL_SUKAPURASTPHL3 (Long=106.9169, Lat=-6.17782) Target Ncell (PCI 413): N_JKT528ML_STOPGILINGANML3 (Long=106.9232, Lat=-6.18416)
PCI 413 Az: 280
Distance ~994 m (less than 1km) C_JKU794 is not in the parameter dump so this site may not be on-air but this will be a potential issue if the planned PCI is used when it is commissioned
PCI 415 Az: 30
SUKAPURASTPHL PCI 414 Az: 150
PCI 413 Az: 330
PCI 412 Az: 210
PCI 411 Az: 90
STOPGILINGANML
115
Second-Closest PCI Re-Use (PCI = 129/130/131, EARFCN = 1875) Based on gcell_jabo_31Mar
GUDANGGARAMML
Source Site (PCI 129, 130, 131): GUDANGGARAMML (Long=106.8765, Lat=6.17109) Target Site (PCI 129, 130, 131): GDINGMDITERNIA2STPHL (Long=106.8939, Lat=-6.1594)
PCI 129 Az: 20
PCI 131 Az: 270
PCI 130 Az: 180
Distance ~2.32 km Also PCI 130 are pointing towards similar areas in close proximity Both sites on-air PCI 129 Az: 300
GDINGMDITERNIA2STPHL
PCI 130 Az: 60 PCI 131 Az: 180 116
RACH
117
Preamble Count 99% of the RACH attempts were successful on first preamble only. Indicates very high preambleInitialReceivedTargetPower . Scope to reduce the preambleInitialReceivedTargetPower to -104 dBm to -108 dBm PRACH PREAMBLE COUNT 1.2
1.2 1
0.8
0.8
0.6
0.6
0.4
0.4
0.2
0.2
0
CDF(%)
PDF (%)
1
0 0
>0 1 2 3 4 5 6 ReselPrioSerFreq
NO Perform Reselection** Snonintrasearch included YES YES
SServingCell > Snonintrasearch
NO YES Perform Measurements SServingCell < Thresh serving, low
NO NO
YES
SNonServingCell,x > Thresh x, low for TReselectionUTRAN
NO 146
Scenario Comparison L2W Reselection TSEL Settings • q-RxLevMin = -128 dBm • s-NonIntraSearch = 18 dB
TSEL Settings • q-RxLevMin = -128 dBm • threshServingLow = 16 dB
TSEL Settings • q-RxLevMin = -115 dBm • threshXLow = 12 dB • T-ReselectionUTRA = 1s • q-QualMin = -18 dB
When to start IRAT cell reselection measurements? SServingCell ≤ Snonintrasearch LTE serving cell RSRP ≤ -110 dBm
When to start leaving LTE? SServingCell < Threshserving,low LTE serving cell RSRP ≤ -112 dBm
When to reselect to WCDMA? SNonServingCell,x > Threshx,low for 1s WCDMA non-serving cell RSCP > -103 dBm for 1s & Ec/No > -18 dB
Qualcomm Recommendations • q-RxLevMin = -124 dBm • s-nonIntraSearch = 12 dB
Qualcomm Recommendations • q-RxLevMin = -124 dBm • threshServingLow = 8 dB
Qualcomm Recommendations • q-RxLevMin = -115 dBm • threshXLow = 8 dB • T-ReselectionUTRA = 2s • q-QualMin = -18 dB
When to start IRAT cell reselection measurements? SServingCell ≤ Snonintrasearch
Conclusion With TSEL current settings, UE will start IRAT search at -110 dBm.
LTE serving cell RSRP ≤ -112 dBm
When to start leaving LTE? SServingCell < Threshserving,low LTE serving cell RSRP ≤ -116 dBm
When to reselect to WCDMA? SNonServingCell,x > Threshx,low for 1s WCDMA non-serving cell RSCP > -107 dBm for 1s & Ec/No > -18 dB
QC proposes -112 dBm to improve UE battery life
Conclusion TSEL settings may unnecessarily trigger reselection to WCDMA cells to early when LTE cell is below -112 dBm
Conclusion When UE is already in suboptimal LTE cell, TSEL settings may delay UE reselection to better WCDMA cell – higher risk for LTE OOS 147
LTE to WCDMA Cell Reselection Parameters LTE Parameter
Allowed Range
Current
QC View
(9) 18 dB Start at -110 dBm
(6) 12 dB Start at -112 dBm
• Inter-freq/IRAT neighbor search starts at -110 dBm • With q-RxLevMin adjustment, s-NonIntraSearch has to be modified as well
(8) 16 dB Start at -112 dBm
(4) 8 dB Start at -116 dBm
• Threshold for IRAT reselection serving cell criteria. • UE is ready to reselect when LTE serving cell is below RSRP -116 dBm
(6)
(4)
12 dB
8 dB
(58)
(58)
(i.e., -120 dBm .. -26 dBm)
-115 dBm
INTEGER (0 .. 7)
1s
INTEGER (0 .. 31)
s-NonIntraSearch (i.e., 0 dB to 62 dB) INTEGER (0 .. 31)
threshServing,Low (i.e., 0 dB to 62 dB)
INTEGER (0 .. 31)
• • • •
Actual value = IE value * 2 dB UTRAN threshold to start reselection to lower priority RAT Also has to be aligned with q-RxLevMin in SIB 6 With this settings, 3G neighbor needs to be at least better than -107 dBm to be selected
-115 dBm
• • •
Actual value = (IE value * 2) + 1 dBm Value refers to UMTS RSCP Align to 3G-QRXLevmin
1s
•
Value in [sec]
threshX-Low (i.e., 0 dB to 62 dB)
INTEGER (-60 .. -13)
q-RxLevMin
t-ReselectionUTRA
Comments
148
Connected Mode LTE to WCDMA Redirection
149
Connected Mode Mobility – IRAT LTE to WCDMA Basic Overview of L2W IRAT Handover Implementation in Telkomsel Telkomsel uses coverage based IRAT redirection – triggered based on RSRP According to Handover Mode Switch configuration, Telkomsel network allows for three HO modes. −
L2W Redirection
−
L2G Redirection
−
Blind HO (during CSFB)
Redirection - A process in which the eNodeB releases a UE and instructs the UE to access a cell working at a certain frequency. Redirection to other RAT in Telkomsel is blind redirection (based on event A2) −
If A2 threshold for IRAT ≤ A2 threshold for blind handling, eNB will only configure A2 for blind HO
−
WCDMA has higher priority for blind HO than GSM.
MO
Parameter
Value
CellHoParaCfg
BlindHoA1A2ThdRsrp
-114 dBm
Notes A2 threshold for blind HO
150
L2W Redirection – Field Example A2 Configuration from eNB
3
1
eNB sends L2W redirection UE reports event A2
2
*Event A2: Serving cell becomes worse than an absolute threshold. 151
L2W Redirection Parameters – Event A2 Parameter
MO
Huawei Parameter
timeToTrigger (A2)
InterRatHoCommGroup
InterRatHoA1A2TimeToTrig
Threshold (A2)
CellHoParaCfg
BlindHoA1A2ThdRsrp
hysteresis (A2)
InterRatHoCommGroup
InterRatHoA1A2Hyst
triggerQuantity (A2)
InterRatHoComm
InterRatHoA1A2TrigQuan
Current
QC View
(11)
(9)
640ms
480ms
-114 dBm
-116 dBm
(2)
(4)
1 dB
2 dB
RSRP
RSRP
reportInterval (A2)
480ms
480ms
reportAmount (A2)
r1
r1
Comments • •
Inter-RAT reporting (event a2) is enabled A too large setting will delay the event triggering, possibly causing service degradation on the source cell
• •
Actual value is IE value – 140dBm Too low value implies the risk of radio link failure on LTE
• •
Actual value = IE value * 0.5 dB 1 dB has the risk of un-necessarily entering/leaving reporting condition
• • •
Value in ms or minutes Indicates the interval between periodic reports Lower value may need to be revisited to manage signaling load in future
•
Represents number of times a measurement report is sent
152
Idle Mode WCDMA to LTE Cell Reselection
153
Scenario Comparison W2L Reselection TSEL Settings • E-UTRAN Priority = 7 • UTRAN Priority = 4
TSEL Settings • s-PrioritySearch1 = 4 dB • s-PrioritySearch2 = 2 dB • q-RxLevMin (WCDMA) = -115 dBm • q-QualMin = -18 dB
TSEL Settings • q-RxLevMin (LTE) = -128 dBm • threshXhigh = 20 dB • T-reselectionS = 2s
When to start cell reselection measurements? UE always measures LTE cells as LTE is higher priority RAT than WCDMA
How often to measure LTE while in WCDMA? If Srxlev_serv > Sprioritysearch1 & Squal_serv > Sprioritysearch2 , then at least every Thigher_priority_search Every 60 s while serving cell RSCP ≥ 111 dBm & EcNo > -16 dBm
When to reselect to LTE cell?
Qualcomm Recommendations E-UTRAN is set to higher-priority than WCDMA
Qualcomm Recommendations • s-PrioritySearch1 = 16 dB • s-PrioritySearch2 = 4 dB • q-RxLevMin (WCDMA) = -115 dBm • q-QualMin = -18 dB
Qualcomm Recommendations
SrxlevnonServingCell,x > Threshpx,high > for TreselectionRAT
• q-RxLevMin (LTE) = -124 dBm
LTE non serving cell RSRP ≥ -108 dBm for 2 s
• T-reselectionS = 2s
• threshXhigh = 12 dB
When to start cell reselection measurements? UE always measures LTE cells as LTE is higher priority RAT than WCDMA
How often to measure LTE while in WCDMA? If Srxlev_serv > Sprioritysearch1 & Squal_serv > Sprioritysearch2 , then at least every Thigher_priority_search Every 60 s while serving cell RSCP ≥ -99 dBm & EcNo > -14 dBm
When to reselect to LTE cell? SrxlevnonServingCell,x > Threshpx,high > for TreselectionRAT LTE non serving cell RSRP ≥ -112 dBm for 2 s
Conclusion TSEL settings are inline with QC recommendations
Conclusion If s-PrioritySearch1 and sPrioritySearch2 are set low, W2L reselection may be delayed
Conclusion TSEL settings require LTE RSRP to be > -108 dBm which may delay W2L reselection
154
WCDMA to LTE Cell Reselection Parameters LTE Parameter
Allowed Range
Current
QC View
(64)
(60)
-128 dBm
-124 dBm
INTEGER (0 … 31)
(2)
(4)
(i.e., 0 dB to 62 dB)
4 dB
8 dB
INTEGER (-70 .. 22)
q-RxLevMinEUTRA (i.e., -140 dBm .. 44 dBm)
Comments • If set too low, UE may reselect to an LTE cell with low quality and struggle to complete attach procedure
S-PrioritySearch1
INTEGER (0 .. 7)
(2)
(6)
(i.e., 0 dB to 7 dB)
2 dB
6 dB
INTEGER (0 .. 31)
(10)
(24)
20 dB
12 dB
• These parameters influence how frequently UE measures LTE cell while in WCDMA • If these two are set too low, WCDMA to LTE reselection may be delayed
S-PrioritySearch2
ThreshXhigh (i.e., 0 dB to 62 dB)
• • •
Actual value = (IE value * 2) + 1 dBm Value refers to UMTS RSCP Align to 3G-QRXLevmin
155
WCDMA to LTE Transition Observation
156
W2L Redirection With CM Upon UE Inactivity Telkomsel W2L Transition Overview Telkomsel uses Service-based W2L Service Based Redirection triggered during Low activity state.
W2L Redirection 3G NodeB
3 5 1
UE in 3G with active data connection
−
Low activity state: Conditions for a D2F or D2P state transition are met (UE inactivity)
−
If a UE in connected mode supports LTE measurements, the RNC triggers LTE measurements.
−
If the UE does not support LTE measurement, the RNC enables the UE to directly perform blind redirection.
The procedure for the current procedure is as the following 4
1.
UE is in WCDMA with active data connection
2.
UE inactivity is detected
3.
RNC configures compressed mode for LTE cell measurements along with event 3C configuration
4G eNodeB 2
User Inactivity
UE transition to LTE 6
−
RNC checks the total number of UEs in compressed mode in all cells in the active set
−
If the number is less than threshold (currently set to 20), RNC sends CM configuration
4.
UE reports event 3C for suitable LTE cells
5.
RNC sends RRC connection release with redirection to LTE 157
W2L Redirection Upon UE Inactivity – Field Example 1
RNC configures CM & E3C upon UE inactivity
2
4
UE reports E3C for PCI 122 & 159
3
UE registers in PCI 122 in LTE
RNC sends RRC Conn. Release with Redirection to LTE EARFCN 1875
Compressed Mode takes ~3s since UE inactivity in WCDMA until TAU Complete in LTE
158
Additional Solutions to Speed Up W2L Transition W2L Transition Enhancement Qualcomm proposes two options for solution to enhance the speed of W2L transition 1.
W2L Service Based Blind Redirection
2.
W2L Fast Reselection
W2L Service-Based Blind Redirection
W2L Fast Reselection
• RNC sends RRC connection release with redirection upon UE inactivity
• SIB19 based reselection
• UE does not need to wait until it is in CELL_PCH to transition to LTE upon data inactivity
• Reselection happens only in CELL_PCH
• Goal: Allow UE to transition to LTE faster without having to go through CELL_PCH
• UE needs to wait for transition to CELL_PCH upon data inactivity
• Goal: Speed up transition to CELL_PCH so UE can reselect to LTE Faster
159
Option 1 – W2L Service Based Blind Redirection Background Understanding Service-based W2L redirections are mainly used in the following situations: − − −
A UE only initiates a PS service on the UMTS network in a UMTS/LTE overlapping coverage area. A UE only initiates a PS service on the UMTS only network and then moves to an area under the LTE coverage. It is recommended that this feature be enabled in areas with continuous LTE coverage.
Qualcomm proposes W2L Service Based Blind Redirection triggered during Low activity state. −
Low activity state: Conditions for a D2F or D2P state transition are met (UE inactivity)
WCDMA
LTE
RRC Release with Redirection to LTE 1
UE in 3G with active data connection
2
No more data (inactivity)
3
Upon inactivity timer expiry, instead of D2F RBR, RNC sends release with redirection to LTE
4
UE continues data connection in LTE
160
Option 1 – W2L Service Based Blind Redirection Parameter Settings & Recommendations MO
UCELLU2LTEHONCOV
UCELLU2LTEHONCOV
UCELLU2LTEHONCOV
Parameter
HO_LTE_SERVICE_PS_OUT_SWITCH
HO_LTE_SERVICE_BLIND_FIRST_SWITCH
U2LServTrigSource
Current
1
0
1
QC View
Notes
1
• Whether to allow service-based UMTS-to-LTE redirections • When this switch is set to on, the RNC is allowed to deliver servicebased LTE cell measurement control messages and initiate servicebased UMTS-to-LTE PS handovers. When this switch is set to off, the RNC is prohibited from initiating service-based UMTS-to-LTE PS handovers.
1
• When this switch is set to on, a blind redirection is preferentially performed. When this switch is set to off, LTE measurement is preferentially performed and then a handover or redirection is performed based on the measurement report from the UE. • When this switch is set to on, the number UEs in compressed mode in the cell decreases and user experience in throughput is improved if the LTE coverage is good. However, if the LTE coverage is poor, the number of cell reselections increases.
1
• Trigger Source for Service-based U2L HO/Redir • Value 1 indicates U2L_SERV_LOWACTIVE_TRIGGER (Low activity state: Conditions for a D2F or D2P state transition are met when the UE enters the low-speed data transmission state.)
161
Option 1 – W2L Service Based Blind Redirection Example from Other Operator in Indonesia - Indosat Upon UE inactivity, Network sends RRC Connection Release with Redirection info
UE then starts redirection to LTE. In total, only ~1s required since UE inactivity in WCDMA until TAU Complete in LTE 162
Option 2 - W2L Fast Reselection Background Understanding W2L Reselection only happens from CELL_PCH or IDLE Fast Dormancy switch (RNC_EFD_D2F_SWITCH) is enabled in the network
Recommendation Turn on W2L Fast Reselection
−
Upon inactivity in CELL_DCH, UE is configured to CELL_FACH
−
Upon further inactivity in CELL_FACH, UE is configured to CELL_PCH
FAST_RETURN_LTE_BY_CELL_SELECT _SWITCH = 1
Telkomsel’s current configuration is the following MO
Parameter
Value
Notes
UPSINACTTIMER
PsInactTmr
1800s
Non-Fast Dormancy UE waits for 1800s inactivity time before entering CELL_PCH
UPSINACTTIMER
PsInactTmrForFstDrmDch
5s
Fast Dormancy UE waits for 5s inactivity in CELL_DCH before entering CELL_FACH
UPSINACTTIMER
PsInactTmrForFstDrmFach
5s
Fast Dormancy UE waits for 5s of inactivity in CELL_FACH before entering CELL_PCH
OptimizationSwitch
RNC_EFD_D2F_SWITCH
1
Allow CELL_DCH to CELL_FACH transition for Fast Dormancy UE
URRCTRLSWITCH
FAST_RETURN_LTE_BY_CELL_SELECT_SWITCH
0
Fast Reselection to LTE is inactive
163
Option 2 - W2L Fast Reselection Direct CELL_DCH to CELL_PCH/IDLE Transition for Fast Dormancy Capable UE Without Fast Reselection – UE needs to wait a total of 10 s until it enters CELL_PCH
WCDMA CELL_DCH
CELL_FACH
5s inactivity PsInactTmrForFstDrmDch = 5s
5s inactivity
CELL_PCH
W2L Reselection
LTE
PsInactTmrForFstDrmFach = 5s
With Fast Reselection – UE directly enters CELL_PCH upon inactivity in CELL_DCH (only 5 seconds)
WCDMA CELL_DCH
5s inactivity
CELL_FACH
5s inactivity
CELL_PCH
W2L Reselection
LTE
5s inactivity PsInactTmrForFstDrmDch = 5s 164
Option 2 - W2L Fast Reselection Faster CELL_DCH to CELL_PCH/IDLE Transition for Non-Fast Dormancy Capable UE Without Fast Reselection – non-FD capable UE follows PsInactTmr of 1800s before reconfigured to CELL_PCH
WCDMA CELL_DCH
1800s inactivity
CELL_PCH
W2L Reselection
LTE
PsInactTmr = 1800s
With Fast Reselection – non-FD capable UE follows PsInactTmrForFstDrmDch of 5s before reconfigured to CELL_PCH
WCDMA CELL_DCH
1800s inactivity
CELL_PCH
W2L Reselection
LTE
PsInactTmrForFstDrmDch = 5s
*Note: Most LTE Capable UEs already support Fast Dormancy 165
W2L Transition – Delay Comparison Delay Imposed from Different Scenario WCDMA
1
Redirection w/ CM
W2L Compressed Mode
* If no. of CM users in the RNC 20
3
W2L Blind Redirection
4
Fast Cell Reselection
LTE 1s
RRC Release w/ Redirection
Registration TAU Complete
Total ~8s
Registration TAU Complete
Total ~14 - 15s
2s 5-second WCDMA inactivity timer
WCDMA CELL_FACH
WCDMA CELL_PCH
5s
LTE Cell Measurement until reselection
5s
WCDMA CELL_PCH
5s
*Even longer if UE keeps transitioning between RRC States (cell reselection, paging, etc)
3s 1s
W2L Blind Redirection
WCDMA CELL_FACH
1s
LTE Cell Measurement until reselection
Registration TAU Complete
1s
Registration TAU Complete
Total ~6s
Total ~9s
3s 166
W2L Transition - Implementation Consideration Pros and Cons No.
W2L Transition Method
1
W2L Service Based Redirection with compressed mode LTE cell measurements (Current Settings)
2
3 4
Pros
Cons
Notes
• If number of compressed mode UE in all cells in ASET is above threshold, redirection is not triggered – UE stays longer in WCDMA
• Safe solution for non-ubiquitous LTE coverage area.
W2L Normal Reselection
• The basic safest way for W2L transition
• Might take long time as UE needs to transition through CELL_DCH – CELL_FACH – CELL_PCH first
• Might take even longer if UE keeps changing RRC State (due to WCDMA cell reselection, background data, etc) as W2L reselection can only occur in CELL_PCH • Dependent on inactivity timer in CELL_DCH and CELL_FACH
W2L Service Based Blind Redirection
• Fast W2L transition upon UE inactivity
• Risk of not having redirection failure when there is no LTE cells
• In continuous LTE coverage scenario or UMTS and LTE co-coverage scenario, this is the preferred for faster W2L transition
W2L Fast Reselection
• The safest way to avoid any W2L transition failures
• UE still needs to be transitioned to CELL_PCH
• Combination with method 1 or 2 when UE is not configured with compressed mode is also worth to be trialed
• Low Redirection failure risk, because LTE cells are measured before redirection
167
Network Counter Analysis
168
Counters Observation Summary (1) 1. 2. 3.
Overall low network utilization for LTE network in Jakarta Based on number of users and traffic, network busy hours are from 16 to 19 PM Overall good accessibility and retainability performance during busy hours − − −
4.
22.5 average RRC connected users while only 5 active users (with data) at busy hours − −
5. 6.
Major reason of RRC failures are attributed by UE no reply indicating cells with poor UL coverage, 3 cells are identified to have highest RRC failure due to no reply Major reason of ERAB failures are attributed by TNL rejection at 11 sites Major reason of abnormal releases (drop) are attributed to RF and handover failure suggesting areas of poor coverage and need of neighbor relation optimization Long inactivity timer (20 sec) resulting in high ratio of RRC connected users in LTE compared to active users (4-6 times) In most of the cells, RRC connected users are below 200, except lampsite -cover a big church at Kota Kasablanka- every Sunday noon causing RRC success rate degradation (when users > 400)
Network is DL data centric as indicated by 90:10 of DL to UL volume ratio 11 Mbps average cell DL throughput at busy hours − − −
CQI and 2x2 MIMO usage are the main factors of cell DL throughput, improving cells with worst RF would increase DL efficiency Most of indoor cells do not support MIMO due to DAS limitation Need to check 5 macro cells with 0% 2x2 usage
169
Counters Observation Summary (2) 7.
Low average PRB Usage in busy hours (~10% in DL and 12.% in UL) − − − −
8.
Low average PDCCH CCE usage in busy hours (~20%) − −
9.
UL PRB usage is higher than DL PRB as it takes both PUSCH and PUCCH into account PUCCH resource is set to dynamic and in average consumed ~3.6 PRB and minimum 2 Only 17 cells have PRB DL usage > 50% All cells have UL PRB usage < 50% Most of cells have 20%
Indoor cells mostly do not have MIMO enabled due to DAS limitation Indoor lamp site show good OLSM usage (>20%) Further check on: − 5 macro cells with 0% OLSM usage (1 antenna) − 61 macro cells with 10 Need to check physical antenna installation for possible antenna copolarization
Indoor Cells
182
Integrity – UL Cell Throughput ~1.4 Mbps Cell UL Throughput UL cell throughput is observed ~1.35 Mbps at both busy hours and off-peak hours Users demand is currently the main factor for achievable UL cell throughput as it is not affected by UL interference / number of users
UL Cell Throughput 4E+12 1.6 3.5E+12
2E+12
0.8 0.6
1.5E+12
0.4
1E+12
0.2
5E+11
UL Interference -111 -112
28-0 28-10 28-14 28-21 29-4 29-11 29-18 30-1 30-8 30-15 30-22 31-5 31-12 31-19 1-2 1-9 1-16 1-23 2-6 2-13 2-20 3-3 3-10 3-17
2.5E+12
1
Volume (bits)
3E+12
1.2
0
0
Date - Hour LThrpbitsUL
Cell_UL_Throughput_Active_Avg
dBm
-113
28-0 28-6 28-12 28-18 29-0 29-6 29-12 29-18 30-0 30-6 30-12 30-18 31-0 31-6 31-12 31-18 1-0 1-6 1-12 1-18 2-0 2-6 2-12 2-18 3-0 3-6 3-12 3-18
Throughput (Mbps)
1.4
-114 -115 -116 -117 UL_Interference_Avg 183
UL Interference (1) ~2.6 dB Higher UL Interference at Peak
Peak Hours -109 -110 -111 -112 -113 -114 -115 -116 -117
Off-Peak Hours
Macro - 10MHz
-111.59 -111.49
IBS - 10MHz IBS - 15MHz
-113.6
-113.76
Delta Peak - OffPeak
Average UL Interference (dBm)
3.00
-108
2.50
also used for PUCCH -110
2.00
-112
1.50
-114
1.00
-116
0.50
-118
0.00
-120
UL Interference
UL Interference (dBm) per PRB for 10 MHz Cells
-114.41 -116.2
Delta Noise
off-Peak-1
off-Peak-2
off-Peak-3
Peak-16
Peak-17
Peak-18
Peak-19
off-Peak-4
~2.6 dB delta between peak and off-peak UL interference, higher than expected Indoor cells have higher average UL interference in general – due to DAS quality? Higher UL interference at low band PRB – scheduler tend to allocate low band PRBs for PUSCH (refer to UL PRB number study) Observed at different cells in the network 184
UL Interference (2) Higher UL Interference at Low Band PRB – consistently observed at different cells Correlation between users and UL interference There are still some traffic at off-peak – explains why UL interference of low band PRB is higher even at off-peak hours Many cells still have high UL interference in off-peak hours, mostly at indoor, example: − − − − −
JKU528IM_WTCMGDUA JKP680IM_GRINDOMALLB2 JKP772IM_GROSIRSENENJA YA JKP680IM_GRINDOMALLA JKS850IM_WTC2
Avg Users / Cell vs UL Interference (Peak) 0
50
100
150
200
-80 -90 -100 -110 -120 -130 Avg Users / Cell vs UL Interference (Off-Peak) 0
50
100
150
200
-80 -90 -100 -110 -120 -130 185
UL Interference (3) Recommendation 135634 132819 133024 132786 133946 133653 134083 433191 137814 132025 135580 134460 143991 134717 137485 133464 502113 137861 132135 134599 133020 133586 144057 137458 147302 143148 131180
Peak Hours UL Interference @ eNodeB
-95 -100 -105 -110 -115 -120 -125
PRB_0-3 PRB_4-7 PRB_44_47
135634 132292 143037 131178 135569 133307 132715 133718 143034 137988 131147 144027 135689 502001 133129 133446 135139 132607 433189 143253 143073 144080 137920 143072 134519 137259 148734
Off-Peak Hours UL Interference @ eNodeB
-95 -100 -105 -110 -115 -120 -125
PRB_0-3 PRB_4-7
Recommendation: Distribute PUSCH across different PRBs through enhanced frequency selective scheduling (Huawei specific) It seems that interference-randomization-basedscheduling is not really effective to distribute UL PRB at low band and high band need further investigation May need to activate frequency selective scheduling – controlled by RsvdSwPara0_bit28 under the eNBCellRsvdPara.RsvdSwPara0 Reduce P0 nominal PUSCH (currently too high) to reduce UE Tx Power – (refer to UL throughput test study) – need adjustment in pathloss alpha to compensate the reduction Investigate worst cells with high UL RSSI even in off-peak hours
PRB_44_47
186
Number of RRC Connected Users and Active Users 4-6 times connected users compared to active users
Busy Hours Average Users 10 9 8 7
15
6 5
10
4 3
5
2 1
0
0 28-0 28-5 28-9 28-15 28-20 29-1 29-6 29-11 29-16 29-21 30-2 30-7 30-12 30-17 30-22 31-3 31-8 31-13 31-18 31-23 1-4 1-9 1-14 1-19 2-0 2-5 2-10 2-15 2-20 3-1 3-6 3-11 3-16 3-21
Number of Users
20
Date - Hour Ratio
User_Avg
User_Data_Avg
Active Users
25
Ratio between Connected vs Active User
RRC Connected Users vs Active Users (with Data Buffer)
50 45 40 35 30 25 20 15 10 5 0 0
50
100
150
200
RRC Connected Users
The ratio between RRC connected users and active users (with data buffer) is 4 to 6 Current inactivity timer is 20 secs, may need to reduce it to 10 secs to reduce the load and save UE battery Spurious paging (explained in different study) also contribute to high RRC connected users 187
Mobility – RRC Redirection (PS Retention) ~6% Redirection Rate at Busy Hours to other RATs (3G / 2G) For PS Retention at LTE, RRC redirection is used to measure how much the traffic lost from LTE to 3G or 2G during connected mode RRC redirection rate is defined as a ratio between:
600000
0.06
500000
0.05
400000
0.04
300000 0.03 200000
0.02
100000
0.01 0
Redirection Attempt
0.07
− −
LTE RRC redirection to 3G and 2G during and number of RRC success
Most RRC redirection is to 3G, only < 0.2% to 2G ~6% connection lost to 3G/2G (redirection rate) is a bit high, typical target should be around 5% L2W redirection currently set to -112 dB with 1dB hysteresis, it is possible to reduce it to -114 dB with 2dB hysteresis
0
7-0 7-6 7-12 7-18 8-0 8-6 8-12 8-18 9-0 9-6 9-12 9-18 10-0 10-6 10-12 10-18 11-0 11-6 11-12 11-18 12-0 12-6 12-12 12-18 13-0 13-6 13-12 13-18
Redirection Ratio (per RRC attempt)
Redirection Activity to 3G and 2G
Date - Hour LRRCRedirectionE2W
LRRCRedirectionE2G
IRAT_Redirection_Ratio 188
Mobility – CS Fallback Redirection ~100% CSFB redirect to 3G CSFB preparation success in LTE is in very good level Almost all CSFB call is redirect to 3G ~100%
CSFB o 3G and 2G 100
300000 250000 200000
99.9
150000 99.85 100000
0%
CSFB Attempt
99.95
LRRCRedirectionE2 WCSFB (CSFB to 3G) LRRCRedirectionE2G CSFB (CSFB to 2G) 100%
99.8
50000
99.75
0
7-0 7-6 7-12 7-18 8-0 8-6 8-12 8-18 9-0 9-6 9-12 9-18 10-0 10-6 10-12 10-18 11-0 11-6 11-12 11-18 12-0 12-6 12-12 12-18 13-0 13-6 13-12 13-18
CS Fallback Preparation Succ (%)
CSFB Redirection
Date - Hour LRRCRedirectionE2WCSFB
LRRCRedirectionE2GCSFB
CSFB_Prep_Succ_% 189
Mobility – Handover Success Rate KPI ~99.8% HO Success Rate HO success rate do not have correlation with load, it remains good at busy hours Following target eNodeB with very low HO incoming success rate:
Handover Success 100
25000 20000 15000
99.7 10000 99.6 5000
99.5
99.4
HO Failure
99.8
eNodeB
Site Name
HO_Fail
135563 132512 132786 134278 475224 131241 432897 134107 131815
JKU563MM_GDGCORDOVA C_JKP512ML_GEDUNGARVA C_JKP786ML_KENARI2MENTENGSTP C_JKT278ML_PRKMPNGNINDKCILSTP C_TNX224ML_KAVLINGDEPLU C_JKB241ML_DURIKOSAMBIPDKBAMBUSTP C_JSX897ML_RUKOROYALPALACETEBET C_JKT107ML_KAVDKI C_JKB815ML_JALANLAYANGCKRGPTEL
11524 6891 2612 2503 2412 2331 2207 1990 1810
HO_Incoming HO_Fail Succ% Contribution% 0.05 6.73 86.25 4.03 94.01 1.53 96.85 1.46 95.70 1.41 98.21 1.36 99.10 1.29 97.11 1.16 97.24 1.06
0
7-0 7-6 7-12 7-18 8-0 8-6 8-12 8-18 9-0 9-6 9-12 9-18 10-0 10-6 10-12 10-18 11-0 11-6 11-12 11-18 12-0 12-6 12-12 12-18 13-0 13-6 13-12 13-18
HO Succ Rate %
99.9
Date - Hour HO_Fail_Intra_eNB
HO_Fail_Inter_eNB
HO_Succ_Intra_eNB_%
HO_Succ_Inter_eNB_%
HO_Succ_Tot_%
JKU563MM with 0% incoming HO succ rate has high packet loss ~2E10-3 For quick resolution, neighbor relation to this eNodeB can be deleted / blacklisted 190
PRB Usage
Users vs PUCCH PRB
Low PRB DL and UL Usage
8 7 6
14
7
12
6
10
5
8
4
6
3
4
2
2
1
0
0
Date - Hour PUCCH_PRB
PUSCH_PRB
PRB_DL_Usage_%
PRB_UL_Usage_%
PUCCH PRB
8
5 4 3 2
PRACH Load %
16
28-0 28-5 28-9 28-15 28-20 29-1 29-6 29-11 29-16 29-21 30-2 30-7 30-12 30-17 30-22 31-3 31-8 31-13 31-18 31-23 1-4 1-9 1-14 1-19 2-0 2-5 2-10 2-15 2-20 3-1 3-6 3-11 3-16 3-21
RACH Success Rate
DL Cell Throughput
1 0 0
50
100
150
200
RRC Connected Users
All cells have UL PRB usage < 50% UL PRB usage is higher than DL PRB as it takes both PUSCH and PUCCH into account PUCCH resource is set to dynamic and in average consumed ~3.6 PRB and minimum 2 191
PRB Usage DL 6 cells with PRB DL Usage > 60% PRB DL Usage vs Cell Throughput
Number of Users vs PRB DL Usage 90
40
80
35
PRB DL Usage %
Cell Throughput (MbpS)
45
30 25 20 15
10 5
70 60
0
20
40
60
PRB DL Usage %
80
100
Number of Cells
60%
6
PRB DL usage is still low in general, average is ~11% in busy hours Only 17 cells have PRB DL usage > 50% 6 cells with PRB DL usage > 60%
50 40 30 20 10
0
PRB DL Usage
0 0
50
100
150
RRC Connected Users
200
250
− − − − −
JKB032ML_TLKMSLIPIML3 C_JKU205ML_GADINGASRIML3 C_JBX076ML_KOTABAMBUSELATANTBGML2 JKP027ML_HTLLEMERIDIEML2 JKP222ML_PSRBENHILLML1
192
PDCCH Usage
Users vs PDCCH Usage %
7 6 5 4 3 2 1 0
20 15 10 5 0
PDCCH CCE Aggregation
25
28-0 28-10 28-14 28-21 29-4 29-11 29-18 30-1 30-8 30-15 30-22 31-5 31-12 31-19 1-2 1-9 1-16 1-23 2-6 2-13 2-20 3-3 3-10 3-17
PDCCH CCE Usage %
PDCCH CCE Usage
Date - Hour PDCCH_CCE_Agg_Avg
PDCCH_CCE_Usage_%
PDCCH symbol adaptation is enabled so the eNodeB can decrease / increase number of symbol for PDCCH dynamically based on number of required CCEs Cells with low average CQI (poor RF) use higher PDCCH CCE aggregation level – higher CCE resources & low coding rate
60 50 40 30 20 10 0
0
50
100
150
200
RRC Connected Users
CQI vs PDCCH CCE Aggregation PDCCH CCE Aggregation
Low PDCCH Usage, mostly < 50%
PDCCH CCE Utilization %
70
8 7 6 5 4 3 2 1 0 5
7
9
11
13
15
17
CQI 193
Integrity – Packet Delay & Loss Packet Loss mostly 1E-5
Date - Hour Packet_Delay_QCI6
Packet_Delay_QCI7
Packet_Loss_QCI6
Packet_Loss_QCI7 194
Integrity – Cell Throughput per CQI Lower DL Cell Throughput of QCI 6 than QCI7 UL Cell Throughput
10 8 6 4 2 0
3E+13 2.5E+13 2E+13 1.5E+13 1E+13
Payload (bits)
12
2 1.8 1.6 1.4 1.2 1 0.8 0.6 0.4 0.2 0
5E+12 0
28-0 28-10 28-14 28-21 29-4 29-11 29-18 30-1 30-8 30-15 30-22 31-5 31-12 31-19 1-2 1-9 1-16 1-23 2-6 2-13 2-20 3-3 3-10 3-17
14
Throughput (Mbps)
2.00E+13 1.80E+13 1.60E+13 1.40E+13 1.20E+13 1.00E+13 8.00E+12 6.00E+12 4.00E+12 2.00E+12 0.00E+00
28-0 28-10 28-14 28-21 29-4 29-11 29-18 30-1 30-8 30-15 30-22 31-5 31-12 31-19 1-2 1-9 1-16 1-23 2-6 2-13 2-20 3-3 3-10 3-17
Throughput (Mbps)
16
Payload (bits)
DL Cell Throughput
Date - Hour
Date - Hour LThrpbitsDLQCI6
LThrpbitsDLQCI7
LThrpbitsUL
LThrpbitsDL
Cell_DL_Throughput_QCI6
Cell_DL_Throughput_QCI7
Cell_UL_Throughput_QCI6
Cell_UL_Throughput_QCI7
Both postpaid (QCI6) and prepaid (QCI7) have similar MBR Postpaid has scheduling priority (weight), but cell DL throughput is lower Low data demand of QCI6 can be the reason, as the throughput is flat across all hours May also need to do check the counters accuracy 195
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