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CBRA Success Rate - Guideline PA2

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CBRA Optimization
Guideline
July 2019
Introduction
CBRA
 CBRA(Contention Based Random Access)
Initiate access, handover and ue initiated ul resync
CFRA
 CFRA(Contention Free Random Access)
The CFRA can be used for incoming handover and for
PDCCH ordered UL re-synchronization in case of DL data
arrival for a UE that is out-of-sync in UL, i.e. a UE whose
time alignment timer has expired.
RA Senario
CBRA
CFRA
Initial network access
Yes
Access following a radio link failure
Yes
Incoming Handover between cells (High
Yes
Yes
Downlink data transfer requiring uplink
synchronization
Yes
Yes
Uplink data transfer requiring uplink
synchronization
Yes
Uplink data transfer without dedicated
scheduling request resource
Yes
speed ue: PDCCH order for requesting UE
access attempts due to RA failures at their
previous access attempts by using CFRA)
LTE_CBRA_Success_Rate =
100*(EUtranCellFDD.pmRaSuccCbra/EUtranCellFDD.pmRaAttCbra)
LTE_CFRA_Success_Rate =
100*(EUtranCellFDD.pmRaSuccCfra/EUtranCellFDD.pmRaAttCfra)
2019-07-03 |
Counter
pmRaAttCbra
pmRaSuccCbra
pmRaAttCfra
pmRaSuccCfra
pmRaAllocCfra
pmRaUnassignedCfraFalse
pmRaUnassignedCfraSum
pmRaFailCbraMsg2Disc
pmRaFailCfraMsg2Disc
Description
The number of detected CBRA preambles in the cell.
The number of successfully detected RA Message 3 for CBRA.
The number of detected CFRA preambles in the cell.
The number of successfully detected RA Message 3 for CFRA.
The number of allocated CFRA preambles in the cell.
The number of detected CFRA preambles that are not allocated to any UE.
The total number of unassigned CFRA preambles at each PRACH activity.
The number of CBRA preambles for which no random access response (RA Msg2) was sent due to expiry of the random access response window.
The number of CFRA preambles for which no random access response (RA Msg2) was sent due to expiry of the random access response window.
Random Access – Cell Range vs RachRootSequence
The value of cellRange decides the preamble format to be used in the
random access procedure;
— cellRange  15  preamble format 0
— cellRange > 15  preamble format 1
› Cell Range = 15km  # of
RSI = 10
› Default RSI =384
—
By Default, cellRange parameter is fixed to 15 km.
—
—
Other cell ranges than 15 km can be set if the Maximum Cell Range
feature is enabled
rachRootSequence
The first root (Zadoff-Chu) sequence number for Random Access Channel
(RACH) preamble generation. It is broadcasted as a part of system
information distribution and used for preamble detection
The parameter takes the value in the range of 0 to 837 and the default value
is 386. It is recommended to set the parameter rachRootSequence to
different values in neighboring cells to reduce the probability for false RACH
detections
– For the particular cell
384,385,
…….,394 will be used.
› Therefore, neighboring
cells RSI should differ by
at least 10, resulting a
reuse of 838 (0 to 837) /
10  80 “groups”
Based on 3GPP 36.211
cellRange
Defines the maximum distance from the RBS where a connection to a UE can
be setup or maintained, or both
For a cellrange of 15 km size, the values of rachRootSequence in adjacent cells must differ by at least 10 between any two neighbors (and at most 827 since there is a wrap-around between the first
and last value in the value range) in order to eliminate overlap or collision
2019-07-03 |
Random Access - Optimization
—
Possible reasons for RACH failure:
—
—
—
—
—
—
—
—
Hygiene issue
Improper Radio optimization parameter
Improper RA preamble planning;
Poor RF condition;
Sleeping cell;
SW Bugs
Other reason (e.g. intermittent transport problem)
CBRA = NULL
—
—
—
—
—
—
Network hygiene is the most important factor for all services,
including Random Access. Need to follow up any issue related
to Active alarm, VSWR, ASM, TxRank2, UL RSSI etc to TS team.
For improper Radio optimization parameter, initial tuning team
need to follow standard Layering parameter guideline;
For current cell range setting (15km), the parameter
rachRootSequence should differ at least 10 between any two
neighbors to avoid collision;
Check for poor RF conditions. Increase the coverage area by
adjusting Tilt/Azimuths of self/neighbor sites and avoid
overlapped or overshooting coverage;
Upgrade to the newest software patch that available in the
network;
Sleeping cell is hard to detect. When there are many RA
attempt, but none successes (high pmRaFailCbraMsg2Disc),
the cell is considered a sleeping one. Try to lock/unlock the cell,
or cold restart;
Clear issue transport problem for both source/target cells
handover that experience bad Random Access
2019-07-03 |
Solution
CBRA < 20%
•
•
•
Availability issue;
No contact;
Counter not yet activated



Sleeping Cells
Synchronization issue
Sudden degradation of
CBRA/CFRA






Hygiene issue
Improper Radio parameter
Improper RA preamble planning
Poor RF Condition
SW Bugs
Other reason
•
•
•
Hygiene check
Solved No contact issue
Counter activation check
•
•
•
Lock unlock cells
Cold restart
Clear synchronization issue.
•
Hygiene Check and troubleshooting
on site if necessary, regarding
• ASM
• TxRank2
• Active Alarm
• VSWR
Parameter baseline concheck
• Basic parameter concheck
• Layering concheck
• Eutranrelation concheck
Rach Optimization
• RachRootSequence
• cellRange
• preambleInitialReceivedTargetP
ower
Physical Tuning
Upgrade to new SW patch
Clear transport problem issue
Possible
Reason
Solutions:
—
CBRA = 0%
“ M Loss of Sync over CPRI
Connections Synchronization=1,NodeGrou
pSyncMember=1
(clock_synchronisation_problem)”
•
•
•
•
•
Optimization Sample Cases
2019-07-03 |
CellRange and RachRootSequence Relation on CBRA Case
Background:


Sharp raising of pmRaAttCbra was observed in a sudden in cell
EJD961B, started from 2018-05-26 21:45:00
But counter pmRaSuccCbra did not show obvious degradation before
and after sharp raising of pmRaAttCbra;
Analysis
prachConfiguration collision was observed, so there might be high risk of false CBRA Msg1
detection among cells, and which might lead to pmRaAttCbra Abnormal Stepping Issue.
Way Forward:
—
—
—
2019-07-03 |
If pmRaAttCbra Abnormal Stepping Issue was observed with
— No obvious abnormal behavior was observed for counter ” pmRaSuccCbra”,
”pmRaAttCfra”, and ”pmRaSuccCfra”
— No obvious abnormal behavior was observed for UL interfernce counters
— No obvious abnormal behavior was observed for other KPI/PI measurements
Please collect cell information with template in previous table within at least 15 km cell
range of current cell with issue observed.
If PRACH configuration collision was observed, please contact Planning team first for
more suggestions
CBRA_SR = NULL due to counter not yet activated
In XL OSS, CBRA counters are include in USERDEF counter, need to activate below
pmJobs/Scanner to measure CBRA :
—
For BB Site  PmJob=USERDEF-L_RADIO_COUNTERS_L17.Cont.Y.STATS
—
For DUS Site  USERDEF-L_RADIO_COUNTERS_L17.Cont.Y.STATS
Counter
Description
pmRaAttCbra The number of detected CBRA preambles in the cell.
pmRaSuccCbra The number of successfully detected RA Message 3 for CBRA.
CBRA Success Rate
100
90
80
70
60
50
40
30
20
10
0
Counter activation
NULL
Before – USERDEF scanner not yet defined
X3472391G_CO
After – USERDEF scanner defined on 27 June 2019
2019-07-03 |
time
object
6/23/2019 X3472391G_CO
6/24/2019 X3472391G_CO
6/25/2019 X3472391G_CO
6/26/2019 X3472391G_CO
6/27/2019 X3472391G_CO
6/28/2019 X3472391G_CO
6/29/2019 X3472391G_CO
6/30/2019 X3472391G_CO
7/1/2019 X3472391G_CO
7/2/2019 X3472391G_CO
7/3/2019 X3472391G_CO
7/4/2019 X3472391G_CO
7/5/2019 X3472391G_CO
7/6/2019 X3472391G_CO
LTE_UL_RSSI_Pwr_dBm
NaN
NaN
NaN
NaN
-111.15
-111.95
-111.72
-110.71
-111.28
-107.62
-105.78
-105.86
-105.46
-104.81
LTE_pmRaSuccCbra_SR
!NULL!
!NULL!
!NULL!
!NULL!
77.40
73.96
76.17
86.07
83.10
73.22
66.11
75.59
73.11
69.95
CBRA SR = 0 – Clock Sync alarm solved after clear NGS issue
and cold restart
Background:
• Found some new L21 sites with Sync Alarm
• Impact to CBRA degradation
ERBS
Layer
Alarm (Cause)
Alarm Clearance
Cold Restart
Alarm clearance
“ M Loss of Sync over CPRI
Connections Synchronization=1,N Sync OK, Cold
4435131E 2100
odeGroupSyncMember=1
restart after TS
(clock_synchronisation_problem)”
Solution:
• Clock Sync Alarm clearance, NGS alarm at 3G node
• Cold restart after execution
Result:
• CBRA Success Rate cells tend to improved
2019-07-03 |
CBRA and Antenna System Monitoring (ASM)
—
—
Refer to counter pmBranchDeltaSinrDistr (LTE)
Detection Bad ASM indicated from this counter calculation
std dev and Avg delta SINR
Antenna System Monitoring (ASM) indicates the following
problems related to the antenna system:
• Mismatched antenna pair Rx diagrams
• Swapped or disconnected feeders
• Loss in RF path
• Missing feeder
• SIR/SINR difference
indicates potential problem
• It is recommended if any
ASM issue persist , need to
check and troubleshooting
on site
1. disconnected
2. RF loss
X
3. Mismatched antennas
4. Swapped antennas
2019-07-03 |
Low CBRA SR due to ASM with remark “Partial Swap Feeder”
Background:
• Found ASM Issue “Partial swap feeder” at
LTE_DIPONEGORO_JATIMULYA, Impact to CBRA degradation
ASM BEFORE
ASM AFTER
Solution:
• Clear ASM and TxRank2 issue by
• On site Tshoot
• RU-Antenna connection correction
Connection Before
Connection After
Correction
120
100
80
Locked RRU
60
40
20
Result:
• CBRA Success Rate cells tend to improved; thus TxRank2 is tend to
improved also
2019-07-03 |
0
0 5 10 15 20 1 6 11 16 21 2 7 12 17 22 3 8 13 18 23 4 9 14 19 0 5 10 15 20 1 6 11 16 21 2 7 12 17 22 3 8 13 18 23 4
8/27/2018
8/28/2018
8/29/2018
8/30/2018
8/31/2018
9/1/2018
4451812E - Average of CB Random Access Success Rate
9/2/2018
9/3/2018
9/4/20189/5/2018
4451812E - Average of Txrank2
2019-07-03 |
ERBS
MC4451487E
MC4451487E
MC4451487E
MC4451487E
MC4451487E
MC4451487E
MC4451487E
MC4451487E
MC4451487E
MC4451487E
MC4451487E
MC4451487E
ASM Before
ASM After
CBRA Improvement
Solution:
• Clear ASM issue by
• On site Tshoot
• RU-Antenna connection correction
• Physical or Remote Tilting changes
Result:
• CBRA Success Rate cells tend to improved
date_id
6/9/2019
6/9/2019
6/9/2019
6/9/2019
6/9/2019
6/9/2019
6/16/2019
6/16/2019
6/16/2019
6/16/2019
6/16/2019
6/16/2019
SectorCarrier
1
2
3
4
5
6
1
2
3
4
5
6
Mean0
0.803429
1.248112
0.114598
1.004739
1.475389
4.284947
0.963841
1.672386
1.089405
1.036284
1.250208
0.647968
StD0
7.374661
7.213307
7.517325
6.830422
7.056444
8.450536
6.978253
7.203958
7.83548
6.978314
7.083157
7.209906
Tilting
Background:
• Found ASM Issue “Mismatch Antenna” Impact to CBRA
degradation (2T2R)
ASM
Low CBRA SR due to ASM “Mismatch Antenna” – 2T2R
—
CBRA cell_9 improved
Remark0
Normal
Normal
Normal
Normal
Normal
Antenna diagram mismatch
Normal
Normal
Normal
Normal
Normal
Normal
CBRA Improvement
Solution:
• Clear ASM issue by
• On site Tshoot
• RU-Antenna connection correction
• Physical or Remote Tilting changes
Result:
• CBRA Success Rate cells tend to improved
2019-07-03 |
ASM Before
ASM After
Tilting
Background:
• Found ASM Issue “Mismatch Antenna” Impact to CBRA
degradation (4T4R)
ASM
Low CBRA SR due to ASM “Mismatch Antenna” – 4T4R
—
CBRA L2100 improved
Low CBRA SR due to RET not calibrate – Overshooting
TA Before
Background:
• Found Overshooting issue and RET not working-well
• Thus impact to Overshooting and Low CBRA
—
—
TA After
RET need calibration
Low TxRank2
CBRA Improvement
CBRA SR vs TxRank2
Solution:
• Suspect due to mismatch RET configuration/need calibration
• On site Tshoot
• RET calibration and correction set to Y4
Result:
• CBRA Success Rate cells tend to improved
100
90
80
70
60
50
40
30
20
10
0
0 3 6 9 12 15 18 21 0 3 6 9 12 15 18 21 0 3 6 9 12 15 18 21 0 3 6 9 12 15 18 21 0 3 6 9 12 15 18 21 0 3 6 9
3/4/2019
3/5/2019
3/6/2019
JK4G18_441PC371E_24 - Average of CB Random Access Success Rate
2019-07-03 |
3/7/2019
3/8/2019
3/9/2019
JK4G18_441PC371E_24 - Average of tx_rank2
Low CBRA due to Impoper Layering parameter
(Network Roll-Out PY2018)
Background:
• Found new site, on air with low CBRA, while hygiene check already
PASS
CBRA Success Rate
Site On Air
concheck L2100
After Inject License
120
100
80
60
Solution:
• Layering concheck L2100
• Lock unlock after execution
40
20
0
0 4 8 12 16 20 0 4 8 12 16 20 0 4 8 12 16 20 0 4 8 12 16 20 0 4 8 12 16 20 0 4
Result:
• CBRA Success Rate and Accessibility cells tend to improved
9/1/2018
9/2/2018
9/3/2018
JK4G18_441PC175E_14
9/4/2018
9/5/2018
9/6/2018
JK4G18_441PC175E_24
Accessibility
Site On Air
concheck L2100
After Inject License
105
100
95
90
85
80
0 3 7 1013161922 1 5 8 1114172023 2 6 9 12151821 0 3 7 1013161922 1 5 8 1114172023 2 6
9/1/2018
9/2/2018
9/3/2018
JK4G18_441PC175E_14
2019-07-03 |
9/4/2018
JK4G18_441PC175E_24
9/5/2018
9/6/2018
Low CBRA due to Improper eARFCN
(Network Roll-Out PY2018)
Background:
• Found some new sites ON Air with old eARFCN
• Impact to CBRA degradation
Solution:
• NCCR221_XL_Discrepancy earfcn JABO_Dec2018.
Result:
• CBRA Success Rate cells tend to improved
2019-07-03 |
New sites with old
earfcn on air
NCCR211
Low CBRA due to Improper Rach Root Sequence (386)
(Network Roll-Out PY2018)
Background:
• Found L21 cell Rach Root Sequence setting = 386 (Default value)
• Rach Root Sequence cleanup based on CDR Planning team, to
avoid RSN collision.
Parameter
Description
rachRootSequence
First root sequence number for RACH preamble generation.
RACH root sequence is broadcast as a part of system information
distribution and is used for preamble detection. For information on the
definition of logical root sequence number, see 3GPP TS 36.211.
Taking effect depends on the feature state.
Exists for MO classes:

EUtranCellFDD.rachRootSequence

EUtranCellTDD.rachRootSequence
Solution:
• NCCR143_XL_Lte_Concheck_rachRootSequence_20190405.
Result:
• CBRA Success Rate L2100 cells tend to improved
2019-07-03 |
CBRA Improvement after RachRootSequence Optimization
(XL NQI Project 2017)
Background:
• The purpose of RACH Root sequence number clean up is as one of
consistency check for RSN disc parameter (Part of optimization)
• Rach Root Sequence cleanup based on CDR Planning team, to
avoid RSN collision.
CBRA Success Rate
85
84
83
82
Solution:
• NCCR NW_Wide_Rach_Seq_Disc_PARA_20170607
Result:
• CBRA Success Rate tend to improved
2019-07-03 |
81
80
79
6/16/2017
6/15/2017
6/14/2017
6/13/2017
6/12/2017
6/11/2017
6/10/2017
6/9/2017
6/8/2017
6/7/2017
6/6/2017
78
6/5/2017
First root sequence number for RACH preamble generation.
RACH root sequence is broadcast as a part of system information
distribution and is used for preamble detection. For information on the
definition of logical root sequence number, see 3GPP TS 36.211.
Taking effect depends on the feature state.
Exists for MO classes:

EUtranCellFDD.rachRootSequence

EUtranCellTDD.rachRootSequence
6/4/2017
rachRootSequence
6/3/2017
Description
6/2/2017
Parameter
Low CBRA on Radio4443 Connected to DUS/DUW – SW Bugs
(XL Orion H2 Program)
CBRA Success Rate vs RSSI
Background:
• Found SW Bugs L18.Q2 and W18.Q2 in site with Radio 4443 that
connected to DUS/DUW
120
100
-100
L2100 Mixedmode
with Radio4443
SW Upgrade from
L18.Q2 to L18.Q4
-102
-104
-106
-108
60
-110
40
-112
-114
20
-116
Solution:
• Overall performance (include ASM) improved after SW Update to
W18Q4.5-1 (3G) and L18.Q4 (LTE)
• Cold Restart after Software upgrade
Result:
• CBRA Success Rate tend to improved
2019-07-03 |
-118
6/19/2019
6/19/2019 18:00
6/20/2019 12:00
6/21/2019 6:00
6/22/2019
6/22/2019 18:00
6/23/2019 12:00
6/24/2019 6:00
6/25/2019
6/25/2019 18:00
6/26/2019 12:00
6/27/2019 6:00
6/28/2019
6/28/2019 18:00
6/29/2019 12:00
6/30/2019 6:00
7/1/2019
7/1/2019 18:00
7/2/2019 12:00
7/3/2019 6:00
7/4/2019
7/4/2019 18:00
7/5/2019 13:00
7/6/2019 7:00
7/7/2019 1:00
7/7/2019 19:00
7/8/2019 13:00
7/9/2019 7:00
7/10/2019 1:00
7/10/2019 19:00
7/13/2019
7/13/2019 18:00
7/14/2019 12:00
7/15/2019 6:00
7/16/2019
7/16/2019 18:00
7/17/2019 12:00
7/18/2019 6:00
7/19/2019
0
Average of LTE_pmRaSuccCbra_SR
Average of LTE_UL_RSSI_Pwr_dBm
RSSI (dBm)
CBRA SR (%)
80
TS - U2100 Config RBB11_1A with UL Attenuation Ext 17 dB and L2100 MIMO Impact to CBRA
the following connection is RBB22_1A, if we have to configure it as RBB11_1A on W side , then we should
consider 2nd RUS as part of antenna
Sample at 3G_CIKUPA

TS taken on Thursday, 26 and 31 July 2018
Result :

UL RSSI improved with config U2100
RBB11_1A and L2100 MIMO

Payload and traffic still under
monitoring
2019-07-03 |
Set ulAttenuation to -170 for EXT
ULRSSI improved
ericsson.com
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