3 lte eran6.0 mro feature issue 1.00
DESCRIPTION
3 Lte Eran6.0 Mro Feature Issue 1.00TRANSCRIPT
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Copyright © 2013 Huawei Technologies Co., Ltd. All rights reserved.
LTE eRAN6.0 MRO Feature
Copyright © 2013 Huawei Technologies Co., Ltd. All rights reserved.
Version Difference
eRAN3.0--Intra-freq LTE MRO
Intra frequency MRO arrives commercial standard
For intra-freq scenario, adjust CIO of cell-pairs as per
previous period's abnormal RLF rate
eRAN6.0--Intra-freq LTE MRO
Decrease ping-pong number for UE Level
Recognize and send anti-ping-pong CIO parameter to
ping-pong UEs.
Page3
Copyright © 2013 Huawei Technologies Co., Ltd. All rights reserved.
Objectives
Upon completion of this course, you will be able to:
Describe the function of MRO
Detail feature and parameters of intra-RAT MRO
Detail feature and parameters of inter-RAT MRO
Page4
Copyright © 2013 Huawei Technologies Co., Ltd. All rights reserved.
Contents
1. Overview
2. Intra-RAT MRO Management
3. Inter-RAT MRO Management
4. Related Features
5. Engineering Guidelines
6. MRO in M2000
Page5
Copyright © 2013 Huawei Technologies Co., Ltd. All rights reserved.
Contents
1. Overview
2. Intra-RAT MRO Management
3. Inter-RAT MRO Management
4. Related Features
5. Engineering Guidelines
6. MRO in M2000
Page6
Copyright © 2013 Huawei Technologies Co., Ltd. All rights reserved.
What is MRO?
MRO (Mobility Robust Optimization) is one
feature of SON
The MRO feature achieves self-optimization
functionality by automatically optimizing handover-
related parameters. This improves the handover
success rate and resource usage.
Page7
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MRO Processing Flow
Page8
Handover Scenario Identification
Handover Scenario Handling
Result Monitoring
X2
Handover processing
Copyright © 2013 Huawei Technologies Co., Ltd. All rights reserved.
Contents
1. Overview
2. Intra-RAT MRO Management
3. Inter-RAT MRO Management
4. Related Features
5. Engineering Guidelines
6. MRO in M2000
Page9
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Intra-RAT Handover Overview
Page10
Intra-Frequency Handover
Inter-Frequency Handover
Measurement trigger (Default)
Handover trigger (A3 event)
Measurement trigger (A2 event)
Handover trigger (A4 or A3 event)
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Intra-RAT MRO Procedure
See Remark.
Page11
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Classification of Intra-RAT MRO
Page12
Intra-RAT MRO
Intra-frequency MRO
A3 CIO modification
Inter-frequency MRO
A3 or A4 CIO
modification
A2 threshold
modification
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Identification of Premature Handover
Page15
UE movement
Source eNodeB Target eNodeB
Normal handover areaPremature handover area
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Identification of Premature Handover (Cont.)
Page16
eNB1 eNB2 UE
1. Measure Report(HO)
2. Handover Request
3. Handover Response
6. RLF In eNB1
8. if find UE ID in local cell UE Context, increase num_ho_too_early by 1
5. Handover Command
7. Re-establish (to old cell)
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Identification of Delayed Handover
Page17
Source eNodeB
UE movement
Target eNodeB
Normal handover area Delay handover area
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Identification of Delayed Handover (Cont.)
Page18
eNB1 eNB2 UE
1: Measure Control(HO)
3: Re-establish ( to new cell)
4: RLF Indication
2. RLF In eNB2
5: if find UE Id in local cell UE Context, increase num_ho_too_late by 1.
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Classification of Delayed Handover
Page19
Source
TargetSource Target
No A2 measurement
report
Gap Measurement command failure
Source Target
A2 measurement report
Measurement configuration failure
Source Target
A4 or A3 measurement report
Handover command failure
X2
Delayed intra-frequency handover Delayed inter-frequency handover related to event A2
Delayed inter-frequency handover related to event A2
Copyright © 2013 Huawei Technologies Co., Ltd. All rights reserved.
Coverage-induced Delayed Handover In a delayed handover, a UE experiences an RLF in
cell A, the RRC connection is reestablished with
neighboring cell B, and cell B reports this
reestablishment event to cell A. This process may
occur in one of the following coverage areas:
Coverage hole in the overlapping area of the two cells
Coverage hole of cell A or B within their overlapping
area
Coverage hole or weak coverage area between cells A
and B that do not overlap
Page20
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Identification of Ping-Pong Handover
Page21
Ping-Pong Handover: Period 2 < PingpongTimeThd
… Cell A
… Period 1
Period 1
Information on the UE
Cell A Cell B
… Cell A Cell B
… Period 1
Period 2
Period 2Information on the UE
Ping-pong handover decision
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MRO Scenario Handling
Page22
Check handover statistics periodically
Check whether the threshold is achieved
Premature handovers and delayed handover
optimization
Ping-Pong handover
optimization
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Optimization of Premature & Delayed Intra-Frequency Handover Proportion of RLF-induced abnormal handovers >
RLF-induced abnormal handover threshold
Proportion of RLF-induced abnormal handovers ≤
RLF-induced abnormal handover threshold, and
Handover success rate ≤ MRO.NcellOptThd
(threshold for MRO between neighboring cells)
Page23
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Optimization of Premature & Delayed Intra-Frequency Handover(Cont.) In either of the preceding scenarios, the eNodeB
reacts as follows:
If the proportion of premature handovers to the total
number of RLF-induced abnormal handovers is greater
than 70%, the eNodeB decreases the CIO for intra-
frequency event A3 by one step.
If the proportion of delayed handovers to the total
number of RLF-induced abnormal handovers is greater
than 70%, the eNodeB increases the CIO for intra-
frequency event A3 by one step.
Page24
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Optimization of Delayed Inter-Frequency Handover related to A2 Triggering condition: Inter-frequency MRO trigger has the
same conditions as intra-frequency, and with the
following additional conditions:
The proportion of delayed handovers related to event A2
≥ a specified threshold,
the threshold for event A2 < the threshold for the event
A1,
the handover is regarded as a delayed handover
related to event A2 and A2 threshold is increased
by one step.
Page25
Proportion of delayed handovers
related to event A2
Number of delayed handovers related to event A2
Number of premature handovers
Number of delayed
handovers
Copyright © 2013 Huawei Technologies Co., Ltd. All rights reserved.
Optimization of Premature or Delayed Inter-Frequency Handover unrelated to A2
If the proportion of delayed handovers related to
event A2 < the specified threshold, the handover
is regarded as a delayed handover unrelated
to event A2 or a premature handover: Number of premature handovers < Number of delayed
handovers, then A4 or A3 CIO of inter-frequency
neighbor cell is increased by one step.
Number of premature handovers > Number of delayed
handovers, then A4 OR A3 CIO of inter-frequency
neighbor cell is decreased by one step.
Page26
Copyright © 2013 Huawei Technologies Co., Ltd. All rights reserved.
Cell-Level MRO against Ping-Pong Handovers The eNodeB performs MRO against ping-pong handovers
by decreasing the CIO value between the cells by one
step if the following conditions are met:
Proportion of ping-pong handovers > MRO.MRO.
PingpongRatioThd
where, Proportion of ping-pong handovers = Number of ping-pong
handovers/Total number of successful handovers
Handover success rate ≥ MRO.MRO.NcellOptThd
Proportion of RLF-induced abnormal handovers < RLF-
induced abnormal handover threshold/2
Page27
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UE-Level MRO against Ping-Pong Handovers the number of consecutive ping-pong handovers<
MRO.UePingPongNumThd, the eNodeB does not
regard the UE as a ping-pong UE. The eNodeB
delivers the configured CIO value to the UE.
the number of consecutive ping-pong handovers=
MRO.UePingPongNumThd, the eNodeB regards
the UE as a ping-pong UE, decreases the configured
CIO value by 1 dB for the UE, and then delivers the
result to the UE.
Page28
Copyright © 2013 Huawei Technologies Co., Ltd. All rights reserved.
UE-Level MRO against Ping-Pong Handovers(Cont.) MRO.UePingPongNumThd <the number of
consecutive ping-pong handovers< MRO.
UePingPongNumThd+2, the eNodeB regards the
UE as a ping-pong UE, decreases the configured CIO
value by 2 dB for the UE, and then delivers the result
to the UE.
the number of consecutive ping-pong handovers ≧ <
MRO.UePingPongNumThd+2, the eNodeB cannot
resolve ping-pong handovers for the UE and
increases the number of ping-pong handover
resolution failures by 1.Page29
Copyright © 2013 Huawei Technologies Co., Ltd. All rights reserved.
Value Range for Intra-Frequency Handovers If operators expect that an intra-frequency handover
is triggered when the difference of the measured
signal quality between the neighboring and serving
cells falls into the range of A to B, the operators
should set CELLMRO.CioAdjLowerLimit and
CELLMRO.CioAdjUpperLimit according to the
following formulas:
CioAdjLowerLimit = Min(Off + Ofs + Ocs - Ofn + Hys -
B)
CioAdjUpperLimit = Max(Off + Ofs + Ocs - Ofn + Hys -
A)Page30
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MML Command
Page31
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Value Range for Inter-Frequency Handovers The entering condition for event A4 is as follows: Mn
+ Ofn + CIO - Hys > Thresh. It is generally agreed
that a neighboring cell can provide continuous
services only when Mn is higher than -110 dBm.
Therefore, Huawei eNodeB calculates the upper limit
of the CIO value range for event A4 as follows:
Min(Thresh + 110 - Ofn + Hys). The eNodeB takes -
24 as the lower limit.
In summary, the CIO value range for inter-frequency
event A4 is [-24, Min(Thresh + 110 - Ofn + Hys)].
Page32
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Adjustments for Cell-Level MRO Cell-Level Penalty Ping-pong adjustments of parameter settings may occur
between MRO periods. Huawei eNodeB monitors the last
three parameter adjustments made during MRO periods.
If the last value is identical to the first value, the eNodeB
considers that a ping-pong parameter adjustment
occurred. As a penalty, the eNodeB will not perform MRO
throughout the next two MRO periods, each specified by
MRO.OptPeriod.
Page33
1
2
0
No optimization
No optimization
OptimizationPing-Pong
Optimization
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Adjustments for UE-Level MRO UE-Level Penalty When a UE-level ping-pong handover MRO period (4
hours) approaches its end, the eNodeB calculates the
proportion of RLFs due to delayed handovers caused by
UE-level MRO as follows:
Proportion of RLFs due to delayed handovers caused by UE-
level MRO against ping-pong handovers = Number of such
delayed handovers/(Number of times the CIO value is
decreased by 1 dB + Number of times the CIO value is
decreased by 2 dB)
If the proportion of RLFs due to delayed handovers
caused by UE-level MRO against ping-pong handovers
exceeds 1/20 (fixed), the eNodeB postpones the UE-level
ping-pong handover MRO for two periods.Page34
Copyright © 2013 Huawei Technologies Co., Ltd. All rights reserved.
MML Command
Page35
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MML Command (Cont.)
Page36
Copyright © 2013 Huawei Technologies Co., Ltd. All rights reserved.
Contents
1. Overview
2. Intra-RAT MRO Management
3. Inter-RAT MRO Management
4. Related Features
5. Engineering Guidelines
6. MRO in M2000
Page38
Copyright © 2013 Huawei Technologies Co., Ltd. All rights reserved.
Inter-RAT Handover Overview
Page39
Inter-RAT Handover
Measurement trigger (A2 event)
Handover trigger (B1 event)
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Inter-RAT Handover Classification
Page40
Inter-RAT MRO
Delayed handover
A2 related delayed
handover
Optimization A2 triggering threshold for
QCI
A2 non-related delayed
handover
Optimization of hysteresis
for B1
Premature handover
Optimization of hysteresis for B1
Copyright © 2013 Huawei Technologies Co., Ltd. All rights reserved.
Identification of Delayed Inter-RAT Handover related to event A2 - type 1
Page42
Triggering conditions:
The eNodeB does not or fails to deliver the gap
measurement configuration, and does not receive
intra-RAT premature or delayed handover indication
The source cell has valid inter-RAT neighboring cells
and the inter-RAT neighboring cells support the
ongoing services of the UE
The source cell deletes the UE context due to timer
expiration.
Copyright © 2013 Huawei Technologies Co., Ltd. All rights reserved.
Optimization of Delayed Inter-RAT Handover related to event A2 - type 1
Page43
MRO handling conditions: Proportion of delayed handovers in type 1 ≥ Proportion
threshold for delayed handovers related to event A2 Threshold for event A2 < Threshold for event A1
the handover is regarded as a delayed Inter-RAT handover related to event A2 and A2 threshold is increased by one step (for the corresponding QCI)
Proportion of delayed handovers
in type 1
Number of delayed inter-RAT handovers in type 1
Number of premature inter-RAT handovers
Number of delayed inter-RAT handovers
Copyright © 2013 Huawei Technologies Co., Ltd. All rights reserved.
Identification of Delayed Inter-RAT Handover related to event B1 - type 2
Page44
Triggering conditions:
The eNodeB receives a measurement configuration for
event A2 and successfully delivers a measurement
configuration for setting up a measurement gap.
The eNodeB does not or fails to deliver a handover
command, and does not receive intra-RAT premature or
delayed handover indication.
The source cell has valid inter-RAT neighboring cells
and the inter-RAT neighboring cells support the
ongoing services of the UE.
The source cell deletes the UE context due to timer
expiration.
Copyright © 2013 Huawei Technologies Co., Ltd. All rights reserved.
Optimization of Delayed Inter-RAT Handover related to event B1 - type 2
Page45
MRO handling conditions:
Proportion of delayed handovers in type 1 < Proportion
threshold for delayed handovers related to event A2
Number of premature handovers < Number of delayed
handovers in type 2
the handover is regarded as a delayed Inter-RAT
handover related to event B1 and B1 threshold is
decreased by one step (for the corresponding QCI)
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Optimization of Premature Inter-RAT Handover
Page46
is defined similarly as the intra-RAT premature handover
Triggering conditions: Proportion of delayed handovers in type 1 < Proportion
threshold for delayed handovers related to event A2 Number of premature inter-RAT handovers > Number
of delayed inter-RAT handovers in type 2 the handover is regarded as a premature and the
hysteresis for event B1 is increased by one step.
Proportion of delayed handovers
in type 1
Number of delayed inter-RAT handovers in type 1
Number of premature inter-RAT handovers
Number of delayed inter-RAT handovers
Copyright © 2013 Huawei Technologies Co., Ltd. All rights reserved.
Contents
1. Overview
2. Intra-RAT MRO Management
3. Inter-RAT MRO Management
4. Related Features
5. Engineering Guidelines
6. MRO in M2000
Page47
Copyright © 2013 Huawei Technologies Co., Ltd. All rights reserved.
Related Features
MRO is closely related to mobility management in
connected mode. MRO is performed based on all the
parameter values initially set for mobility
management in connected mode, and the parameter
adjustments by MRO affect mobility management in
connected mode.
If RAN sharing is deployed, only the primary operator
can modify handover parameters.
Page48
Copyright © 2013 Huawei Technologies Co., Ltd. All rights reserved.
Contents
1. Overview
2. Intra-RAT MRO Management
3. Inter-RAT MRO Management
4. Related Features
5. Engineering Guidelines
6. MRO in M2000
Page49
Copyright © 2013 Huawei Technologies Co., Ltd. All rights reserved.
Intra-RAT MRO
Use intra-frequency MRO only after RF optimization
is performed. Use intra-frequency MRO continuously
during routine eNodeB maintenance because MRO
can automatically identify scenarios with no MRO
gains and avoid parameter adjustments.
When intra-frequency MRO is enabled, it is
recommended that the MRO.StatNumThd
parameter be set to 1000 and the MRO.OptPeriod
parameter be set to 1440, which indicates a day.
Page50
Copyright © 2013 Huawei Technologies Co., Ltd. All rights reserved.
Intra-RAT MRO (Cont.)
Use inter-frequency MRO when either of the
following conditions is met:
The number of intra-RAT RRC connection
reestablishments is higher than expected.
The number of premature, delayed, or ping-
pong handovers between two inter-frequency
cells is higher than expected.
Page51
Copyright © 2013 Huawei Technologies Co., Ltd. All rights reserved.
Contents
1. Overview
2. Intra-RAT MRO Management
3. Inter-RAT MRO Management
4. Related Features
5. Engineering Guidelines
6. MRO in M2000
Page52
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Intra-Frequency MRO Activation Observation
Page53
This section describes
how to use SON logs
to verify all types of
MRO.
If a switch is turned on
in a MRO Switch
Setting event, the
corresponding type of
MRO has been
activated.
Copyright © 2013 Huawei Technologies Co., Ltd. All rights reserved.
Collecting and Analyzing MRO Data Choose Configuration > MRO Management and
choose “Log Statistics” tab.
Page54
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Performance Monitoring
To monitor the performance of intra-RAT MRO,
observe the following counters:
Page55
Counter Name Description
L.HHO.Ncell.PingPangHoNumber of ping-pong handovers between a specific pair of cells
L.HHO.NCell.HoToolateNumber of delayed intra-RAT
handovers
L.HHO.NCell.HoTooearlyNumber of premature intra-RAT
handovers
Copyright © 2013 Huawei Technologies Co., Ltd. All rights reserved.
Performance Monitoring(Cont.)
To monitor the performance of inter-RAT MRO,
observe the following counters:
Page56
Description Description
L.IRATHO.E2W.PrepAttOutNumber of handover attempts from E-UTRAN to UTRAN
L.IRATHO.E2W.ExecSuccOutNumber of successful handovers from E-UTRAN to UTRAN
L.IRATHO.E2G.PrepAttOutNumber of handover attempts from E-UTRAN to GERAN
L.IRATHO.E2G.ExecSuccOutNumber of successful handovers from E-UTRAN to GERAN
Copyright © 2013 Huawei Technologies Co., Ltd. All rights reserved.
Questions
What are the abnormal HO scenarios?
How to optimize the premature & delayed intra-
frequency handover?
Page57
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Glossary
CIO: Cell Individual Offset
MRO: Mobility Robust Optimization
SON: Self-Organizing Network
RLF: Radio Link Failure
PCI: Physical Cell Identifier
CGI: Cell Global Identifier
RAT: Radio Access Technology
Page58
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