Inter-EnB Inter-Frequency Load Balancing
Short Description
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Description
LTE1170: RL50/RL35TD/RL50FZ
Network Engineering Information John Torregoza MBB CS NE LTE Radio & Performance Wroclaw, April 2013 Please make sure that you are using the latest version of this NEI found in this link: https://sharenet-ims.inside.nokiasiemens https://sharenet-ims.in side.nokiasiemensnetworks.com/liv networks.com/livelink/livelink?func=ll&o elink/livelink?func=ll&objId=491946924& bjId=491946924&objAction=Browse objAction=Browse
LTE1170 – LTE1170 – Inter-e Inter-eNB NB InterInter-Frequ Frequency ency Load Load Balancing Balancing Table of Contents
1
Introduction
2
Technical Details
3
Interdependencies
4
Configuration Management
5
Deployment Aspects
6
Benefits and Gains
Motivation and Feature Overview
Functionality and Implementation, Message Flows
Interdependencies Interdepende ncies with Other Features and Functions
Parameters and parameterisation scenarios
Feature Activation and Configuration Examples
Simulation, Lab and Field Findings
7
Performance Aspects Counters and KPIs, Feature Impact Analysis and Verification
Main Menu
LTE1170 – LTE1170 – Inter-e Inter-eNB NB InterInter-Frequ Frequency ency Load Load Balancing Balancing Table of Contents
1
Introduction
2
Technical Details
3
Interdependencies
4
Configuration Management
5 6
Motivation and Feature Overview
Functionality and Implementation, Message Flows
Interdependencies Interdepende ncies with Other Features and Functions
Parameters and parameterisation scenarios
Deployment Aspects Feature Activation and Configuration Examples
Benefits and Gains Simulation, Lab and Field Findings
7
Performance Aspects Counters and KPIs, Feature Impact Analysis and Verification
Main Menu
Introduction
Main Menu
LTE1170 - Inter-eNB Inter-Frequency Load Balancing
LTE1170 extends RL40 functionality in providing means to move incoming load from a high-loaded cell to low-loaded cells which use different frequency than the high-loaded serving cell • UEs entering Connected state can be offloaded if target cell is measured to be at good radio condition
• • • •
Offloading of UEs can be done towards intra-eNB or inter-eNB neighbor cells Target cell for offloading must have available capacity to serve offloaded UEs Load information is exchanged only between cells of the same eNB Load information from cells belonging to other eNBs are implicitly determined from HO preparation decision in Load blind HO
• The feature balances load only between inter-frequency cells • DL GBR, DL non-GBR and PDCCH load are evaluated to trigger offloading of UEs
LTE55 Inter-frequency handover must be activated in order for LTE1170 to work
Introduction
Main Menu
LTE1170 - Inter-eNB Inter-Frequency Load Balancing
LTE1170 is aimed to improve the utilization of resources between inter-frequency cells
• Does not aim to equally distribute between cells but to have cell load below a configurable threshold 100
100 Freq1
90
Freq2
80
Freq1
90 80 70
70
) % ( 60 d a o 50 L l l 40 e C
With LTE1170
30
) % ( 60 d a o 50 L l l 40 e C
Freq2 High Load Thresh
Target Load Thresh
30
20
20
10
10
0
0 t0
t1
t2
t3
t4
t5
t6
t7
t8
t9
t10
Time
Imbalanced utilization of resources in an eNB resulting in some UEs not scheduled in Freq1
t11
t12
t0
t1
t2
t3
t4
t5
t6
t7
t8
t9
Time
Resources are better utilized, resulting in more scheduled UEs
t10
t11
t12
Introduction
Main Menu
LTE1170 - Inter-eNB Inter-Frequency Load Balancing
LTE1170 extends the RL40 feature LTE1387 (Intra-eNB Inter-Frequency Load Balancing) with the following functionalities: Intra-eNB/Inter-eNB
Load Measurement, Evaluation and Exchange
LTE1387 (RL40)
LTE1170 (RL50)
Intra-eNB
Intra-eNB, Inter-eNB
GBR, non-GBR load (exchange only between same eNB cells)
GBR, non-GBR, PDCCH load (exchange only between same eNB cells) Similar sorting mechanism to LTE1387 for cells of the same eNB is supported.
Target Cell Selection
Suitable candidate cells are sorted according to load information exchanged between cells of same eNB
Load-blind HO for cells with unknown load is supported. Target cells of rejected iFLB-based HO are temporarily blacklisted. Cells with unknown load information are added at the bottom of the sorted list.
Radio Admission Control (RAC)
RAC forwards load measurements from scheduler to higher layers
RAC forwards load measurements from scheduler to higher layers. In case of iFLB-based HO, RAC in target cell checks for target cell’s available capacity and rejects the LBbased HO if the target cell has no available resource.
Introduction
Table of Contents
Main Menu
LTE1170 - Inter-eNB Inter-Frequency Load Balancing
Dependency table: FD-LTE
RL release
eNB
NetAct
Release/version
RL50
LBTS5.0
OSS5.5
TD-LTE
TD LTE release
eNB (TD LTE)
NetAct (TD LTE)
Release/version
RL35TD
TD-LBTS3.0
OSS5.5
Flexi Zone Micro
FZM release
eNB (FZM)
NetAct (FZM)
Release/version
RL50FZ
LNFZ5.0
OSS5.5
HW & IOT
Release/version
HW requirements FSMr2 (Flexi FDD) FSMr3 (Flexi 1Flexi10 TD-LTE0 FDD,)
MME
SAE GW
UE
No dependency
No dependency
3GPP R8 UEs
LTE1170 – Inter-eNB Inter-Frequency Load Balancing Table of Contents
1
Introduction
2
Technical Details
3
Interdependencies
4
Configuration Management
5
Deployment Aspects
6
Benefits and Gains
Motivation and Feature Overview
Functionality and Implementation, Message Flows
Interdependencies with Other Features and Functions
Parameters and parameterisation scenarios
Feature Activation and Configuration Examples
Simulation, Lab and Field Findings
7
Performance Aspects Counters and KPIs, Feature Impact Analysis and Verification
Main Menu
Technical Details
Main Menu
LTE1170 - Inter-eNB Inter-Frequency Load Balancing
Feature Overview LTE1170 can be split into the four building blocks as follows:
Load Supervision and Exchange • Each cell measures DL GBR, DL non-GBR and PDCCH load periodically and exchanges load information between cells of the same eNB
•
eNB decides whether the cell enters or exits active inter-frequency load balancing (iFLB) state
Continuous load Measurement and Exchange
Load Supervision and Exchange
Candidate UE Selection for measurement solicitation • UEs entering Connected state are considered candidates for measurement solicitation Candidate UE Selection for hence avoiding further increase in existing cell load
Measurement Solicitation
• Already connected UEs are NOT offloaded to neighbor cells via load-based HOs • UEs with QCI1 bearers established may be excluded from offloaded UEs depending on parameterization
Measurement Solicitation • A4 measurements is activated if candidate UE’s serving cell is in active iF-LB state
iF-LB Execution • Target cell list (TCL) is created based on r eceived RSRP, RSRQ and load measurements
•
TCL is then sorted and highest ranked neighbor cell is chosen as target cell for offloading
•
Load-blind HO is supported if load information is not available (ex. Inter-eNB target
Measurement Solicitation
iF-LB Execution
Technical Details
Main Menu
LTE1170 - Inter-eNB Inter-Frequency Load Balancing Load Supervision and Exchange
Candidate UE Selection f or Measurement Solicitation
Measurement Solicitation
iF-LB Execution
Cell Load Measurement(1/8)
When LTE1170 is activated, eNB periodically (every 500ms) calculates DL GBR, DL non-GBR and PDCCH load for each of its own cells
Relevant information as highlighted below are provided to L3 from L2 in order to calculate DL GBR, DL non-GBR and PDCCH load
DL GBR Load Measurements PDCCH Load Measurements
DL non-GBR Load Measurements
• DL GBR load (%) is defined as the ratio of the average DL GBR PRB utilization to t he average available PRBs for dynamic scheduling
• PDCCH load (%) is defined as the averaged ratio of utilized CCEs to total number of available CCEs • Total number of available CCEs is calculated based on configurable maximum number of PDCCH symbols(maxNrSymPdcch ), independent of number of currently used PDCCH symbols (when LTE616/LTE939 Usage-based PDCCH Adaptation is activated) • DL non-GBR load (%) is defined as the ratio of the estimated resource utilization for non-GBR bearers to the average available PRBs for non-GBR dynamic scheduling • Average available PRBs for non-GBR dynamic scheduling is the average available PRBs for dynamic scheduling without the PRBs allocated to GBR bearers • Estimated resource utilization for non-GBR bearers is related to the average sum of scheduling weights for established non-GBR bearers
Technical Details
Main Menu
LTE1170 - Inter-eNB Inter-Frequency Load Balancing Load Supervision and Exchange
Candidate UE Selection f or Measurement Solicitation
Measurement Solicitation
iF-LB Execution
Cell Load Measurement (2/8)
DL non-GBR load is estimated based on the average sum of scheduling weights for non-GBR bearers with data available for initial transmission • A single non-GBR UE in an empty cell can occupy most of the available bandwidth, limited only by bandwidthlimiting features (ex. LTE13 - Rate Capping)
DL non-GBR Load Measurements
Average sum of scheduling weights for non-GBR bearers
Scheduling weight pertains to the non-GBR QCI-specific configurable weight parameter, schedulWeight
•
iFLBNomNumPrb
Average available PRBs for non-GBR bearers
Configurable parameter that defines the estimated number of PRBs allocated to a nonGBR bearer with scheduling weight equal to 1
This product defines the estimated resource utilization for non-GBR bearers for a given average sum of weights for non-GBR bearers
It can be easily seen that parameterization of iFLBNomNumPrb defines how high/low non-GBR load is interpreted
Technical Details
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LTE1170 - Inter-eNB Inter-Frequency Load Balancing
Cell Load Measurement (3/8)
iFLBNomNumPrb Behavior Input parameters
Value
Average available PRBs for dynamic scheduling
50 PRBs
Average GBR allocation
20 PRBs
100
iFLBNomNumPrb Values
90
0.001
80
In high values of iFLBNomNumPrb, non-GBR changes significantly with slight changes in average sum of non-GBR weights
) 70 % ( d 60 a o L R 50 B G - 40 n o N 30
A
0.002 0.005 0.01 0.02
higher hysteresis between target and high load thresholds is needed or change iFLBNomNumPrb to a lower value
If iFLBNomNumPrb=0.5 with given input parameters, nonGBR load is 100% if there are >60 UEs with scheduling weight =1.
0.05 0.1 0.2 0.5 1 2
20
5
10
10
0 0
5
10
15 20 25 30
35 40 45 50
55 60 65 70 75 80 85
90 95 100 105 110 115 120 125 130 135 140 145 150
Technical Details
Main Menu
LTE1170 - Inter-eNB Inter-Frequency Load Balancing Load Supervision and Exchange
Candidate UE Selection f or Measurement Solicitation
Measurement Solicitation
iF-LB Execution
Cell Load Measurement (4/8)
The load measurements are subjected to a filter with coefficient α= 0.5 DL GBR Filtered Load Measurements
DL GBR Load Measurements PDCCH Load Measurements
Sliding Window Filter α = 0.5
DL non-GBR Load Measurements
PDCCH Filtered Load Measurements DL non-GBR Filtered Load Measurements
Filter Coefficient α = 0.5 means that the resulting filtered load measurement value consists of past filtered load measurement (50%) and current load measurement (50%)
Filtering prevents the algorithm from being overly sensitive to load measurement variations
Technical Details
Main Menu
LTE1170 - Inter-eNB Inter-Frequency Load Balancing Load Supervision and Exchange
Candidate UE Selection f or Measurement Solicitation
Measurement Solicitation
iF-LB Execution
Cell Load Measurement (5/8) DL GBR Filtered Load Measurements
DL GBR Relative Load
DL GBR Available Capacity
DL non-GBR Filtered Load Measurements
DL non-GBR Relative Load
DL non-GBR Available Capacity
PDCCH Filtered Load Measurements
Filtered load measurements as calculated from load information received from L2
Relative load (Rel.Load) for each load type (DL GBR/DL non-GBR/PDCCH) is the actual load (DL GBR/non-GBR/PDCCH) compared to the corresponding target load thresholds
Available capacity (AC) for each load type (DL GBR/DL non-GBR/PDCCH) defines the available resource of the cell relative to corresponding target load thresholds
PDCCH Relative Load
PDCCH Available Capacity
Technical Details
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LTE1170 - Inter-eNB Inter-Frequency Load Balancing Load Supervision and Exchange
Candidate UE Selection f or Measurement Solicitation
Measurement Solicitation
iF-LB Execution
Cell Load Measurement (6/8) DL GBR Filtered Load Measurements
DL non-GBR Filtered Load Measurements
PDCCH Filtered Load Measurements
Cell LoadX(t) 100%
Target load for X @ 60%
Available capacity in relation to configured target load threshold
Rel. LoadX(t) 100%
ACX(t) DL GBR Relative Load
DL non-GBR Relative Load
PDCCHSuppose that actual cell load for load Relative Load type X (DL GBR/DL non-GBR/PDCCH) is as shown
50%
80% 60%
LoadX(t) 30%
Rel. LoadX(t) 50%
40%
20%
DL GBR Available Capacity
DL non-GBR Available Capacity
PDCCH Available Capacity
50% of the cell’s configured target load threshold for load type X(DL GBR/DL non-GBR/PDCCH) is
Technical Details
Main Menu
LTE1170 - Inter-eNB Inter-Frequency Load Balancing Load Supervision and Exchange
Candidate UE Selection f or Measurement Solicitation
Measurement Solicitation
iF-LB Execution
Cell Load Measurement(7/8) DL GBR Filtered Load Measurements
DL non-GBR Filtered Load Measurements
PDCCH Filtered Load Measurements
Cell LoadX(t) 100%
Target load X @ 60%
DL GBR Relative Load
DL non-GBR Relative Load
Actual cell load for PDCCH load type X (DL Relative Load GBR/DL non-GBR /PDCCH) exceeds corresponding target load threshold
Available capacity=0%, no UEs are offloaded to this cell
Rel. LoadX(t) 100%
80%
LoadX(t) 70%
Rel. LoadX(t) 100%
60% 40%
20%
DL GBR Available Capacity
DL non-GBR Available Capacity
PDCCH Available Capacity
100% of target load threshold for load type X ((DL GBR/DL nonGBR/PDCCH) is utilized
Technical Details
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LTE1170 - Inter-eNB Inter-Frequency Load Balancing Load Supervision and Exchange
Candidate UE Selection f or Measurement Solicitation
Measurement Solicitation
iF-LB Execution
Cell Load Measurement (8/8) DL GBR Filtered Load Measurements
DL non-GBR Filtered Load Measurements
PDCCH Filtered Load Measurements
These load measurements are evaluated to trigger and to stop interfrequency load balancing
Available
DL GBR Relative Load
DL non-GBR Relative Load
PDCCH Relative Load
capacities are exchanged between cells of the same eNB periodically every 1 second
Load information is exchanged independent of load balancing status, i.e. ACs are exchanged whether LB was triggered or not as long as feature is enabled
DL GBR Available Capacity
DL non-GBR Available Capacity
PDCCH Available Capacity
Available capacity is used to quantify the load between different cells This information is exchanged between cells of the SAME eNB
Technical Details
Main Menu
LTE1170 - Inter-eNB Inter-Frequency Load Balancing Load Supervision and Exchange
Candidate UE Selection f or Measurement Solicitation
Measurement Solicitation
iF-LB Execution
Cell Load Evaluation (1/1) Filtered load measurements are evaluated periodically each time measurements arrive from L2 (period= 500ms)
Enter Active iF-LB State
GBR OR nGBR load OR PDCCH load exceed the related high-load thresholds Leave Active iF-LB
Receive and process Load Measurements
N N
Cell in Active iFLB state
Y
HighLoadxxx
Y
PDCCH Filtered Load Measurements
iFLBHighLoadGBRDL/ iFLBHighLoadNonGBRDL / iFLBHighLoadPDCCH
DL non-GBR Filtered Load Measurements
Y
ALL Cell Load < N TargetLoadxxx
ANY Cell Load >
State
GBR AND nGBR load AND PDCCH load are below related the target load thresholds
DL GBR Filtered Load Measurements
N
Y
Leave Active iF-LB State
iFLBTargetLoadGBRDL/ iFLBTargetLoadNonGBRDL/ iFLBTargetLoadPDCCH
Enter Active iF-LB State
UE Selection for Measurement Solicitation
Difference between target load and high load thresholds defines the level of hysteresis to prevent pingpong between iF-LB states
Technical Details
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LTE1170 - Inter-eNB Inter-Frequency Load Balancing Load Supervision and Exchange
Candidate UE Selection f or Measurement Solicitation
Measurement Solicitation
iF-LB Execution
Candidate UE selection for Measurement Solicitation(1/3)
For each UE that enter Connected state, iFLBBearCheckTimer is started. When iFLBBearCheckTimer expires, eNB checks if the following UE selection conditions are met: 1. Serving cell is in Active iF-LB state. 2. UE has no QCI 1 bearer* 3. Frequencies configured in LNHOIF are supported by the UE
4. A4 measurements and reporting supported by UE 5. No ongoing inter-frequency or inter-RAT measurements for the UE
UEs in Idle State
…
iFLBBearCheckTimer
Check UE selection conditions
If conditions are met, activate A4 and start timer reportTimerIFLBA4
t eNB sends Initial Context Setup Response for UE entering Connected state
Parameters
If conditions are not met, UE is not candidate for LB offloading UE stays in cell
Description
6. If carrier aggregation is supported, UE has no SCC configured (FDD RL50 only as CA not supported in RL35TD)
*Note: depending on settings for iFLBBearCheckTimer , condition 2 is not checked
If all conditions are met, A4 configuration is activated (Measurement Solicitation) • Otherwise, UE under consideration is removed f rom possible candidates for offloading (UE stays in cell)
MeasParameters > bandListEUTRA >> interfreqBandlist >> interfreqNeedGaps
Feature Group Indicator
Defines list of frequencies supported by UE For each of the defined frequencies, the list of other frequencies it can measure and necessity of setting gaps.
Defines which features are supported by UE. BIT13 Inter-frequency Handover BIT14 A4 and A5 measurements/reporting
Technical Details
Main Menu
LTE1170 - Inter-eNB Inter-Frequency Load Balancing Load Supervision and Exchange
Candidate UE Selection f or Measurement Solicitation
Measurement Solicitation
iF-LB Execution
Candidate UE selection for Measurement Solicitation(2/3)
Exemplary scenarios for iFLBBearCheckTimer
Suppose iFLBBearCheckTimer =30s,
UEs in Idle State
…
Check UE selection conditions • UE did not establish QCI1
Suppose iFLBBearCheckTimer =30s,
• Other conditions If conditions are met, activate A4 and start timer reportTimerIFLBA4
UEs in Idle State
…
UE establishes QCI1 bearer
30s
30s
eNB sends Initial Context Setup Response for UE going from Idle to Connected
UE can be offloaded if it measures a suitable cell and satisfies other conditions
eNB sends Initial Context Setup Response for UE going from Idle to Connected
•Since QCI1 bearer was established, UE stays in the cell
UE is not a candidate for offloading, UE stays in the highly-loaded cell
Technical Details
Main Menu
LTE1170 - Inter-eNB Inter-Frequency Load Balancing Load Supervision and Exchange
Candidate UE Selection f or Measurement Solicitation
Measurement Solicitation
iF-LB Execution
Candidate UE selection for Measurement Solicitation(3/3)
Exemplary scenarios for iFLBBearCheckTimer
,Suppose iFLBBearCheckTimer=30s,
Check UE selection conditions • UE did not establish QCI1 • Other conditions
UEs in Idle State
Suppose iFLBBearCheckTimer=31s(special value),
If conditions are met, activate A4 and start timer reportTimerIFLBA4
UEs in Idle State
• QCI1 Bearer condition not checked • Other conditions
… …
UE establishes QCI1 bearer
Check UE selection conditions
1s
If conditions are met, activate A4 and start timer reportTimerIFLBA4
30s
eNB sends Initial Context Setup Response for UE going from Idle to Connected
UE established QCI1 bearer 40s after switching to connected state
UE can be offloaded if it measures a suitable cell and satisfies other conditions
eNB sends Initial Context Setup Response for UE going from Idle to Connected
UE can be offloaded if it measures a suitable cell and satisfies other conditions
Technical Details
Main Menu
LTE1170 - Inter-eNB Inter-Frequency Load Balancing Candidate UE Selection f or Measurement Solicitation
Load Supervision and Exchange
Measurement Solicitation
iF-LB Execution
Measurement Solicitation (1/ 2)
ReportConfigEUTRA Parameter Name
> Trigger Type >> eventId
RSRP
Set values event eventA4
Lowest possible A4 RSRP threshold allows measurement of most neighbor cells
A4 Report Sent
RSRP Neighbor
>>> a4-Threshold >>>> threshold-RSRP >> hysteresis
0 (-140dBm) 0
>> Time To Trigger
40ms
> Trigger Quantity
RSRP
> Report Quantity
Both(RSRP & RSRQ)
> MaxReportCells
8
> Report Interval
60min
> Report Amount
1
time A4-threshold = -140dBm TTT=40ms
A4 Configuration hard-coded and NOT configurable! Reported cells are post-processed to remove cells with insufficient RSRP and/or RSRQ.
Technical Details
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LTE1170 - Inter-eNB Inter-Frequency Load Balancing Load Supervision and Exchange
Candidate UE Selection f or Measurement Solicitation
Measurement Solicitation (2 / 2)
If all conditions for Candidate UE selection for Measurement Solicitations are met, reportTimerIFLBA4 timer is started and A4 is activated If IF/IRAT mobility HO event is reported or no A4 reports arrive before reportTimerIFLBA4=3000ms expires, A4 is deactivated and UE stays in cell • UE with IF/IRAT event is excluded from UE candidates for offloading as they may handover via normal means
Some UEs are removed from UE Candidate for offloading (green boxes) UE in Idle Mode
Measurement Solicitation
A4 event activation Set s-measure in measConfig to 0 Add measIDs in MeasConfig Measurement gap handling Send RRC Connection Reconfiguration
Check UE selection conditions
If conditions are met, activate A4 and start timer
reportTimerIFLBA4
…
iFLBBearCheckTimer
eNB sends Initial Context Setup Response for UE going from Idle to Connected
iF-LB Execution
A4 event deactivation Set s-measure in measConfig to threshold1 Remove measIDs in MeasConfig Measurement gap handling Send RRC Connection Reconfiguration
If A4 report from UE arrives before timer expires, Target Cell List (TCL) from A4 reports are postprocessed for iFLB execution
If reportTimerIFLBA4 expires without any reports coming, UE not considered for LB offloading
Deactivate A4
UE stays in the the cell
reportTimerIFLBA4=3000ms
If conditions are not met, UE is not candidate for LB offloading UE stays in
If iF/interRAT event is reported before reportTimerIFLBA4 expires, stop timer and deactivate A4. UE stays in the cell but
t
Technical Details
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LTE1170 - Inter-eNB Inter-Frequency Load Balancing Load Supervision and Exchange
Candidate UE Selection f or Measurement Solicitation
iF-LB Execution (1/8)
Upon receiving A4 reports, the target cell list (TCL) is post-processed to choose the best target cell for offloading
Measurement Solicitation
iF-LB Execution
Elimination of Unsuitable LTE Handover Target Cells due to LB-HO conditions • Target cells with insufficient signal level or quality based on measurement reported.
Measured RSRP/RSRQ below thresholdRsrpIFLBFilter/thresholdRsrqIFLBFilter, respectively
• Target cells whose load is too high (load above target, CAC= min(AC_GBR, AC_nGBR, AC_PDCCH) =0) Target cells whose AC are unknown would not be removed from TCL
Elimination of Unsuitable Cells
• Target cells which are temporarily blacklisted due to highload conditions • Target cells are from another RAT • If target cell is considered as HeNB (HeNB mobility is done via redirection)
Reordering of Target Cell List
Elimination of Unsuitable LTE Handover Target Cells due to Handover Restrictions
Elimination of Unsuitable LTE Handover Target Cells due to Handover Restrictions for VoIP Emergency calls
Choosing the target cell for HO
Handover preparation
Handover Execution and Completion
UE entering Connected
Technical Details
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LTE1170 - Inter-eNB Inter-Frequency Load Balancing Load Supervision and Exchange
Candidate UE Selection f or Measurement Solicitation
Measurement Solicitation
iF-LB Execution
iF-LB Execution (2/8)
Upon receiving A4 reports, the target cell list (TCL) is post-processed to choose the best target cell for offloading
eNB sorts cells in Target Cell List according to descending Composite Available Capacity (CAC) = min (AC_GBR, AC_nGBR, AC_PDCCH)
For cells with unknown CAC, eNodeB places them after cells with CAC>0
Elimination of Unsuitable Cells
TCL Cell 1 CAC=X
Reordering of Target Cell List
Choosing the target cell for HO
Handover preparation
Handover Execution and Completion
y t i r o i r P g n i s a e r c n I
Cell 2 CAC=Y Cell 3 CAC=Z
Ordered according to descending CAC
…. Cell a CAC=? Cell b CAC=? Cell c CAC=?
Same order as measurement report
Technical Details
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LTE1170 - Inter-eNB Inter-Frequency Load Balancing Load Supervision and Exchange
Candidate UE Selection f or Measurement Solicitation
Measurement Solicitation
iF-LB Execution
iF-LB Execution (3/8)
Upon receiving A4 reports, the target cell list (TCL) is post-processed to choose the best target cell for offloading
Topmost cell of sort ed TCL is chosen as the target cell for handover • If no other cells exists in TCL, UE stays in cell
Elimination of Unsuitable Cells
TCL Cell 1 CAC=X
Reordering of Target Cell List
Choosing the target cell for HO
Handover preparation
Handover Execution and Completion
Target Cell for offloading
y t i r o i r P g n i s a e r c n I
Cell 2 CAC=Y Cell 3 CAC=Z
Ordered according to descending CAC
…. Cell a CAC=? Cell b CAC=? Cell c CAC=?
Same order as measurement report
Technical Details
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LTE1170 - Inter-eNB Inter-Frequency Load Balancing Load Supervision and Exchange
Candidate UE Selection f or Measurement Solicitation
Measurement Solicitation
iF-LB Execution
iF-LB Execution (4/8)
Upon receiving A4 reports, the target cell list (TCL) is post-processed to choose the best target cell for offloading Elimination of Unsuitable Cells
TCL Cell a CAC=?
Reordering of Target Cell List
(unknown cell)
Choosing the target cell for HO
Handover preparation
Handover Execution and Completion
y t i r o i r P g n i s a e r c n I
Cell b
If
the highest ranked cell is “unknown” (no existing LNREL) • Highest ranked cell is not considered as target cell for offloading • The next highest ranked cell is check if known
CAC=? (unknown cell) Cell c CAC=? (known cell)
Target Cell for offloading
Technical Details
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LTE1170 - Inter-eNB Inter-Frequency Load Balancing Load Supervision and Exchange
Candidate UE Selection f or Measurement Solicitation
iF-LB Execution (4/8)
Upon receiving A4 reports, the target cell list (TCL) is post-processed to choose the best target cell for offloading
Measurement Solicitation
iF-LB Execution
eNB
shall create a RNL-available NR if a neighbour cell is selected as target for handover preparation (if the RNL-available NR is not yet existing)
Elimination of Unsuitable Cells
TCL
RNL- available NR is created if not yet existing
Cell a CAC=? (unknown cell)
Reordering of Target Cell List
Choosing the target cell for HO
Handover preparation
Handover Execution and Completion
y t i r o i r P g n i s a e r c n I
Cell b CAC=? (unknown cell) Cell c CAC=? (unknown cell)
• If a neighbour cell is selected as target for handover preparation after an A4 event, then the eNB shall create the related RNL-available NR (if it does not exist yet)
Technical Details
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LTE1170 - Inter-eNB Inter-Frequency Load Balancing Load Supervision and Exchange
Candidate UE Selection f or Measurement Solicitation
iF-LB Execution (5/8)
Upon receiving A4 reports, the target cell list (TCL) is post-processed to choose the best target cell for offloading
Measurement Solicitation
Intra-eNB, X2 or S1-based handover is prepared towards the chosen target cell with Handover Cause =“Reduce load in serving cell
Elimination of Unsuitable Cells Source Cell Reordering of Target Cell List
iF-LB Execution
Radio Admission Control works in the same way as described for “HO due to radio reasons” in RRM_SFS.5090
In addition, radio admission control in target cell checks its CAC and decides whether to admit/reject the load based HO
If target cell’s load (any of the load type) is above corresponding target (i.e. CAC=0), target cell rejects HO with failure cause “No Radio Resources Available in Target Cell ”
Radio admission control condition applies for Intra-eNB, X2 or S1 LB-based HO
Target Cell
Handover Request Cause: Reduce Load in Serving Cell
Admission Control
Choosing the target cell for HO HO Preparation Failure
Handover preparation
Handover Execution and Completion
Cause: No Radio Resources Available in Target Cell
Technical Details
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LTE1170 - Inter-eNB Inter-Frequency Load Balancing Load Supervision and Exchange
Candidate UE Selection f or Measurement Solicitation
iF-LB Execution (6/8)
Upon receiving A4 reports, the target cell list (TCL) is post-processed to choose the best target cell for offloading
Measurement Solicitation
If source cell receives a X2AP/S1AP: HANDOVER PREPARATION FAILURE or HO was internally aborted (for Intra-eNB HOs) with cause"Radio Network Layer Cause (No Radio Resources Available in Target Cell)" or "Transport Layer Cause(Transport Resource Unavailable)", source eNB assumes that the target cell has no available capacity
Elimination of Unsuitable Cells Source Cell Reordering of Target Cell List
Target Cell
While the timer is running, the target cell where HO was rejected will be temporarily blacklisted for all LB-based HO requests from the source cell
Admission Control
Choosing the target cell for HO
Handover Execution and Completion
r e m i T O H B L t i b i h o r p
Source eNB starts timer with configurable duration “prohibitLBHOTimer ”
Handover Request Cause: Reduce Load in Serving Cell
Handover preparation
iF-LB Execution
Blacklist evaluation only for LB-based handovers
HO Preparation Failure Cause: No Radio Resources Available in Target Cell Transport Resource Unavailable
Handover Request Cause: Reduce Load in Serving Cell
Handover Request Cause: Reduce Load in Serving Cell
Target Cell X Handover Request Cause: Reduce Load in Serving Cell
Technical Details
Main Menu
LTE1170 - Inter-eNB Inter-Frequency Load Balancing Load Supervision and Exchange
Candidate UE Selection f or Measurement Solicitation
Measurement Solicitation
iF-LB Execution
iF-LB Execution (7/8)
Upon receiving A4 reports, the target cell list (TCL) is post-processed to choose the best target cell for offloading
If the Target cell sends accepts HO request with partial admission of bearers due to load reasons, the source eNB applies temporary blacklisting towards the Target cell
The source eNB starts HO CANCEL procedure with cause “Partial Handover”
Elimination of Unsuitable Cells Source Cell
Target Cell
IE/Group Name ERAB Not Admitted List
Reordering of Target Cell List
Handover Request
> ERAB List Items
Cause: Reduce Load in Serving Cell
>>ERAB Id Admission Control
Choosing the target cell for HO
Handover preparation
Handover Execution and Completion
r e m i T O H B L t i b i h o r p
>> Cause
X2AP: HO Request Acknowledge/ S1AP: HO COMMAND
Different Target Cell
ERAB Not Admitted List
Handover Cancel Cause: Partial Handover
Handover Request Cause: Reduce Load in Serving Cell
Handover Request Cause: Reduce Load in Serving Cell
Handover Request Cause: Reduce Load in Serving Cell
Technical Details
Main Menu
LTE1170 - Inter-eNB Inter-Frequency Load Balancing Load Supervision and Exchange
Candidate UE Selection f or Measurement Solicitation
Measurement Solicitation
iF-LB Execution
iF-LB Execution (8/8)
Upon receiving A4 reports, the target cell list (TCL) is post-processed to choose the best target cell for offloading Elimination of Unsuitable Cells Source Cell Reordering of Target Cell List
Target Cell
Handover Request Cause: Reduce Load in Serving Cell
Admission Control
Choosing the target cell for HO Intra-eNB/X2AP: HO Request Acknowledge/ S1AP: HO COMMAND/
Handover preparation Continue Normal HO Procedures
Handover Execution and Completion
Continue Normal HO Procedures
UE follows normal HO execution and completion procedures for Intra-eNB, X2 or S1-based HO.
Technical Details
Main Menu
LTE1170 LTE 1170 - Inter Inter-eNB -eNB InterInter-Freq Frequenc uency y Load Balancing Balancing
Feature activation • Feature activated via parameter actInterFreqLB Activation flag is common between RL40 LTE1387 and RL50 LTE1170 Upgrade from RL40 to RL50 means that PDCCH load and load-blind HO is considered with regards to impact
on perfomance
• When activated, load measurements are taken and exchange between cells of same eNB. • In addition, iFLBBearCheckTimer is started for each UE that transitions from idle to connected.
Feature deactivation • Load measurements are not taken nor exchanged. iFLBBearCheckTimer is not started • If, iF-LB triggered actions are ongoing, continue actions but do not trigger new actions Running timers are not stopped but no new actions triggered when timers expire Incoming A4 reports are ignored Ongoing iF-LB handovers are completed
LTE1170 – LTE1170 – Inter-e Inter-eNB NB InterInter-Frequ Frequency ency Load Load Balancing Balancing Table of Contents
1
Introduction
2
Technical Details
3
Interdependencies
4
Configuration Management
5
Deployment Aspects
6
Benefits and Gains
Motivation and Feature Overview
Functionality and Implementation, Message Flows
Interdependencies Interdepende ncies with Other Features and Functions
Parameters and parameterisation scenarios
Feature Activation and Configuration Examples
Simulation, Lab and Field Findings
7
Performance Aspects Counters and KPIs, Feature Impact Analysis and Verification
Main Menu
Interdependencies
Main Menu
LTE1170 LTE 1170 - Inter Inter-eNB -eNB InterInter-Freq Frequenc uency y Load Balancing Balancing
LTE1170 Inter-eNB Inter-Frequency Load Balancing- Mandatory feature
LTE55 – LTE55 – Inter-frequency Handover (RL20/RL05TD) • • •
The feature provides means for a UE t o be handed over to neighbor cells of different frequency In order to off load UEs to neighbor cells using different frequency carrier, LTE55 must be activated LTE1170 will not work if LTE55 is not activated
LTE55 Inter-frequency Handover
LTE1170 Inter-eNB InterInter-eNB frequency Load Balancing
Interdependencies
Main Menu
LTE1170 LTE 1170 - Inter Inter-eNB -eNB InterInter-Freq Frequenc uency y Load Balancing Balancing
Affected/Affecting Features LTE1170 Inter-eNB Inter-Frequency Load Balancing- Affected/Affecting
LTE1089 Downlink Carrier Aggregation – Aggregation – 20Mhz (RL50) • UEs with Secondary Component Carrier(SCC) configured will not be considered as candidates for offloading to another layer • If a large percentage of UEs have SCC configured for carrier aggregation, gain from load balancing is limited
LTE1442 Open Access Home eNodeB Mobility (RL50) (RL50) • Home eNodeBs are not considered as target for LB-based HOs • If actHeNBMobility actHeNBMobility = = TRUE and if the PCI is within the PCI PCI range (defined by pciFirst by pciFirst and and pciLast pciLast ) for the HeNB for the EARFCN ( freqEutra freqEutra), ), the cell is removed from the target cell list
• Mobility towards HenB is only via via redirect LTE1089 Downlink Carrier Aggregation-20Mhz
LTE1442 Open Access Home eNodeB eNod eB Mobi Mobility lity
LTE1170 Inter-eNB InterInter-eNB frequency Load Balancing
Interdependencies
Main Menu
LTE1170 LTE 1170 - Inter Inter-eNB -eNB InterInter-Freq Frequenc uency y Load Balancing Balancing
LTE1170 Inter-eNB Inter-eNB Inter-Frequency Inter-Frequency Load Balancing- Affected/Affecting Affected/Affecting features
LTE497 Smart Admission Control (RL40/RL35TD) • LTE497 introduced a threshold maxGbrTrafficLimit to determine whether to initiate congestion control or preemption of GBR bearers maxGbrTrafficLimit and and the LTE1170 GBR high load thresholds iFLBHighLoadGBRDL • No cross-check between the maxGbrTrafficLimit • Relationship between maxGbrTrafficLimit maxGbrTrafficLimit and and iFLBHighLoadGBRDL determines determines whether whether congestion congestion control control or load balancin balancing g is the first mechanism to take effect
LTE533+CRL0923 MRO (RL30/RL35TD) • CRL0923 allows MRO algorithms to be applied as well to inter -frequency neighbor relations • Cell individual offsets adjusted by LTE533 would take into account HO events from LB-based HOs
LTE490 Subscriber profile based mobility (RL30/RL35TD) • Subscriber profiles are applied on the load balancing target frequency carriers as already supported for the normal Inter-Frequency HO targets
• When LTE490 is activated, the SPID assigned to the UE is evaluated and the LB HO target for offloading is selected according to the mobility profile defined by SPID (MODPR (MODPR and MOPR MOCs)
LTE490 Subscriber Profile based Mobility
LTE497 Smart Admission Control
LTE1170 Inter-eNB InterInter-eNB frequency Load Balancing
LTE533 Mobility Robustness
Interdependencies
Main Menu
LTE1170 - Inter-eNB Inter-Frequency Load Balancing
LTE1170 Inter-eNB Inter-Frequency Load Balancing- Supporting features
LTE1383-A Cell Specific neighbor relation / PCI hand ling (RL50/RL35TD) • LNREL object, is created by eNB for a neighbor cell selected as target cell for handover preparation, assuming LNREL object for this neighbor cell does not exist and no other cells in t he TCL are known
LTE1383 Cell Specific Neighbor Relation/PCI Handling
LTE1170 Inter-eNB Interfrequency Load Balancing
LTE1170 – Inter-eNB Inter-Frequency Load Balancing Table of Contents
1
Introduction
2
Technical Details
3
Interdependencies
4
Configuration Management
5
Deployment Aspects
6
Benefits and Gains
Motivation and Feature Overview
Functionality and Implementation, Message Flows
Interdependencies with Other Features and Functions
Parameters and parameterisation scenarios
Feature Activation and Configuration Examples
Simulation, Lab and Field Findings
7
Performance Aspects Counters and KPIs, Feature Impact Analysis and Verification
Main Menu
Configuration Management
Main Menu
LTE1170 - Inter-eNB Inter-Frequency Load Balancing
•
Definition of terms and rules for parameter classification: -
The ‘Basic Parameters’ category contains primary parameters which should be considered during cell deployment and must be adjusted to a particular scenario. These are: -
-
Network Element (NE) identifiers Planning parameters, e.g. neighbour definitions, frequency, scrambling codes, PCI, RA preambles Parameters that are the outcome from dimensioning, i.e. basic parameters defining amount of resources Basic parameters activating basic functionalities, e.g. power control, admission control, handovers Parameters defining operators’ strategy, e.g. traffic steering, thresholds for power control, handovers, cell reselections, b asic parameters defining feature behaviour
The ‘Advanced Parameters’ category contains the parameters for network optimisation and fine tuning: -
Decent network performance should be achieved without tuning these parameters Universal defaults ensuring decent network performance need to be defined for all parameters of this category. If this is not possible for a given parameter it must be put to the ‘Basic Parameters’ category
- Parameters requiring detailed system knowledge and broad experience unless rules for the ‘Basic Parameters’ category are viol ated - All parameters (even without defaults) related to advanced and very complex features
Purpose:
Categories of parameters have been defined to simplify network parameterization. Parameterization effort shall be focused mainly on parameters included in basic category.
Categorization will be reflected in a ‘view’ definition in NetAct CM Editor (planned in RL60) i.e. parameters will be displayed according to
the category: either in the ‘Basic parameters’ view or t he ‘Advanced parameters’ view.
Configuration Management
Main Menu
LTE1170 - Inter-eNB Inter-Frequency Load Balancing
actInterFreqLB
Activation of inter frequency load balancing (iFLB)
Object:
LNBTS
Range:
0 (false), 1 (true)
Default:
0 (false)
Multiplicity:
1
Modification:
Online Modifiable
Category:
Basic
Link to PKDB
Parameter Behavior: Feature is activated on eNB level. • All cells in eNB are considered in LB procedures • However, cell-level exclusion from LB procedures can be done via specific configuration of load thresholds When actInterFreqLB =“TRUE”, load measurements are taken and exchange bet ween cells of same eNB. In addition, iFLBBearCheckTimer is started for each UE that transitions from idle to connected. The parameter serves as a common activation switch for LTE1387 (Intra-eNB Inter-frequency LB) and LTE1170 (Inter-frequency LB) Parameterization Rules: 1. actifHO must be enabled to activate actInterFreqLB • Offloading to other frequencies is not possible without activating inter- frequency handovers 2. The object “Inter freq load bal load thresholds” must be created per cell belonging to an eNB for which actInterFreqLB is set to “TRUE”. • This object contains mandatory parameters (high load and target load thresholds, QCI1 bearer check timer and nominal number of PRBs) which are needed for LB operations 3. At least one of thresholdRsrpIFLBFilter or thresholdRsrqIFLBFilter must be configured when actInterFreqLB is “TRUE” • In order to assure a level of signal power and quality in t arget cells where UEs are offloaded
Configuration Management
Main Menu
LTE1170 - Inter-eNB Inter-Frequency Load Balancing
thresholdRsrpIFLBFilter (1/3)
thresholdRsrpIFLBFilter Object:
LNHOIF
Range:
-140, -139, ..., -44dBm
Step:
step 1dBm
Default:
-100dBm
Multiplicity:
1
Unit:
dBm
Modification:
Online Modifiable
Category:
Basic
Inter-Freq LB Threshold for RSRP Target Filter Parameter Behavior: The parameter thresholdRsrpIFLBFilter defines the minimum RSRP level at which UE reported measurements (via A4 event) are filtered in order to remove cells with insufficient signal power from the Target Cell List(TCL) • Cells with measured RSRP below thresholdRsrpIFLBFilter are removed from TCL
High Value of thresholdRsrpIFLBFilter • Low chance for UE to get offloaded as a suitable target cell needs to be measured with higher RSRP than configured thresholds • Less UEs are offloaded, less risk of HO failures and HO pingpongs
Low Value of thresholdRsrpIFLBFilter • High chance for UE to get offloaded as a suitable target cell needs to be measured with higher RSRP than configured thresholds • More UEs are offloaded, increase in risk of HO f ailures and HO pingpongs
Link to PKDB
The parameter incorporates frequency layer prioritization in offloading UEs as the parameter can be configured per neighbor carrier frequency under LNHOIF object
Configuration Management
Main Menu
LTE1170 - Inter-eNB Inter-Frequency Load Balancing
thresholdRsrpIFLBFilter (2/3) thresholdRsrpIFLBFilter
Inter-Freq LB Threshold for RSRP Target Filter Parameterization Rules: 1. Configured values for thresholdRsrpIFLBFilter is recommended to be above threshold2InterFreq of target cell to prevent inter-frequency mobility ping-pongs. 2. If actInterFreqLB is “TRUE”, at least one of the threshold parameters for RSRP (thresholdRsrpIFLBFilter ) and RSRQ (thresholdRsrqIFLBFilter) must be configured per LNHOIF object
Configuration Management
Main Menu
LTE1170 - Inter-eNB Inter-Frequency Load Balancing
thresholdRsrpIFLBFilter (3/3) Figures show the possible scenarios violations of rule#1 and rule#2 in parameterization of thresholdRsrpIFLBFilter
•Scenario below shows a possible ping-pong scenario if thresholdRsrpIFLBFilter < threshold2InterFreq Scenario: thresholdRsrpIFLBFilter < threshold2InterFreq Serving Cell RSRP (F1)
UE switches from idle to connected state
UE may be handed over back to previous serving cells via normal inter-frequency HO
Serving cells enter Active LB state threshold2InterFreq thresholdRsrpIFLBFilter UE is offloaded to target cell After a short delay Inter-frequency measurements are triggered
Target Cell RSRP (F2)
Configuration Management
Main Menu
LTE1170 - Inter-eNB Inter-Frequency Load Balancing
thresholdRsrqIFLBFilter (1/2)
thresholdRsrqIFLBFilter Object:
LNHOIF
Range:
-19.5, -19, , ..., 3.5, -3 dB
Step:
step 0.5dB
Default:
-10dB
Multiplicity:
1
Unit:
dB
Modification:
Online Modifiable
Category:
Basic
Link to PKDB
Inter-Freq LB Threshold for RSRQ Target Filter -
Parameter Behavior: The parameter thresholdRsrqIFLBFilter defines the minimum RSRQ level at which UE reported measurements (via A4 event) are filtered in o rder to remove cells with insufficient signal quality from the Target Cell List(TCL) • Cells with measured RSRQ below thresholdRsrqIFLBFilter are removed from TCL The parameter incorporates frequency layer prioritization in offloading UEs as the parameter can be configured per neighbor carrier frequency under LNHOIF object High Value of thresholdRsrqIFLBFilter • Low chance for UE to get offloaded as a suitable target cell needs to be measured with higher RSRQ than conf igured thresholds • Less UEs are offloaded Low Value of thresholdRsrqIFLBFilter • High chance for UE to get offloaded as a suitable target cell needs to be measured with higher RSRQ than conf igured thresholds • More UEs are offloaded, increase in risk of HO failures and HO pingpongs
Configuration Management
Main Menu
LTE1170 - Inter-eNB Inter-Frequency Load Balancing
thresholdRsrqIFLBFilter (2/2)
thresholdRsrqIFLBFilter
Inter-Freq LB Threshold for RSRQ Target Filter Parameterization Rules: 1.If actInterFreqLB is “TRUE”, at least one of the threshold parameters for RSRP (thresholdRsrpIFLBFilter ) and RSRQ (thresholdRsrqIFLBFilter) must be configured per LNHOIF object
Configuration Management
Main Menu
LTE1170 - Inter-eNB Inter-Frequency Load Balancing
iFLBTargetLoadGBRDL(1/2)
iFLBTargetLoadGBRDL Object:
LNCEL
Range:
0%..100%
Step:
1%
Default:
50%
Multiplicity:
1
Unit:
%
Modification:
Online Modifiable
Category:
Advanced
Inter-Freq Load Balancing GBR Target Load DL Parameter Behavior: The parameter iFLBTargetLoadGBRDL defines the level of GBR load that triggers the exit from iF-LB Active state of a cell, i.e. stop UE offloading to neighbor cells • Exit from iF-LB Active state occurs if ALL GBR, non-GBR and PDCCH load are below their corresponding target thresholds • Together with iFLBHighLoadGBRDL, iFLBTargetLoadGBRDL provides hysteresis between iF-LB state transitions in terms of GBR load
Link to PKDB
In addition, iFLBTargetLoadGBRDL serves as GBR load reference in the calculation of a cell’s GBR available capacity Setting the target load thresholds to 0% and high load thresholds to 100% allows a cell to be excluded from LB procedures Setting the target threshold to a value XX% and high load thresholds to 100% allows a cell to accept offloaded UEs but does not allow to offload UEs to neighbors Thresholds can be set per load type (DL GBR/DL non-GBR/PDCCH) to differentiate load levels per load type at which cell enters or exits active iF-LB states
Configuration Management
Main Menu
LTE1170 - Inter-eNB Inter-Frequency Load Balancing
iFLBTargetLoadGBRDL(2/2)
iFLBTargetLoadGBRDL Object: Range:
LNCEL 0%..100%
Step:
1%
Default:
50%
Multiplicity:
1
Unit:
%
Modification:
Online Modifiable
Category:
Advanced
Link to PKDB
Inter-Freq Load Balancing GBR Target Load DL
Parameter Behavior: High Value of iFLBTargetLoadGBRDL • More offloaded UEs can can be accepted by the cell from neighbor cells • Easier to exit from active iF-LB in terms of GBR load
Low Value of iFLBTargetLoadGBRDL • Low number of UEs can be offloaded to this cell due to CAC=0 level can easily be reached • Once cell enters active iF-LB state, it is difficult to exit active iF-LB state
Parameterization Rules: 1. Verify that iFLBTargetLoadGBRDL ≤ iFLBHighLoadGBRDL 2. iFLBTargetLoadGBRDL is mandatory when actInterFreqLB =“TRUE”
Configuration Management
Main Menu
LTE1170 - Inter-eNB Inter-Frequency Load Balancing
iFLBTargetLoadNonGBRDL(1/2)
iFLBTargetLoadNonGBRDL Object:
LNCEL
Range:
0%..100%
Step:
1%
Default:
75%
Multiplicity:
1
Unit:
%
Modification:
Online Modifiable
Category:
Advanced
Link to PKDB
Inter-Freq Load Balancing non-GBR Target Load DL Parameter Behavior: The parameters iFLBTargetLoadNonGBRDL defines the level of non-GBR load that triggers the exit from iF-LB Active state of a cell, i.e. stop UE offloading to neighbor cells • Exit from iF-LB Active state occurs if ALL GBR, non-GBR and PDCCH load are below their corresponding target thresholds • Together with iFLBHighLoadNonGBRDL, iFLBTargetLoadNonGBRDL provides hysteresis between iF-LB state transitions in terms of non-GBR load
In addition, iFLBTargetLoadNonGBRDL serves as non-GBR load reference in the calculation of a cell’s non-GBR available capacity Setting the target load thresholds to 0% and high load thresholds to 100% allows a cell to be excluded from L B procedures Setting the target threshold to a value XX% and high load thresholds to 100% allows a cell to accept offloaded UEs but does not allow to offload UEs to neighbors Thresholds can be set per load type (DL GBR/DL non-GBR/PDCCH) to differentiate load levels per load type at which cell enters or exits active iF-LB states
Configuration Management
Main Menu
LTE1170 - Inter-eNB Inter-Frequency Load Balancing
iFLBTargetLoadNonGBRDL(2/2)
iFLBTargetLoadNonGBRDL
Inter-Freq Load Balancing non-GBR Target Load DL
Object:
LNCEL
Range:
0%..100%
Parameter Behavior: High Value of iFLBTargetLoadNonGBRDL
Step:
1%
Default:
75%
Multiplicity:
1
Unit:
%
Modification:
Online Modifiable
Category:
Advanced
Link to PKDB
• More offloaded UEs can can be accepted by the cell from neighbor cells • Easier to exit from active iF-LB in terms of non-GBR load
Low Value of iFLBTargetLoadNonGBRDL • •
Low number of UEs can be offloaded due to CAC=0 can easily be reached Once cell enters active iF-LB state, it is difficult to exit active iF-LB state
Parameterization Rules: 1. Verify that iFLBTargetLoadNonGBRDL ≤ iFLBHighLoadNonGBRDL 2. iFLBTargetLoadNonGBRDL is mandatory when actInterFreqLB =“TRUE”
Configuration Management
Main Menu
LTE1170 - Inter-eNB Inter-Frequency Load Balancing
iFLBTargetLoadPdcch(1/2)
iFLBTargetLoadPdcch
Inter-Freq Load Balancing PDCCH Target Load DL
Object:
LNCEL
Range:
0%..100%
Step:
1%
Default:
50%
Parameter Behavior: The parameters iFLBTargetLoadPdcch defines the level of PDCCH load that triggers the exit from iF-LB Active state of a cell, i.e. stop UE offloading to neighbor cells
Multiplicity:
1
Unit:
%
Modification:
Online Modifiable
Category
Advanced
Link to PKDB
• Exit from iF-LB Active state occurs if ALL GBR, non-GBR and PDCCH load are below their corresponding target thresholds • Together with iFLBHighLoadPdcch, iFLBTargetLoadPdcch provides hysteresis between iF-LB state transitions in terms of PDCCH load
In addition, iFLBTargetLoadPdcch serves as PDCCH load reference in the calculation of a cell’s PDCCH available capacity Setting the target load thresholds to 0% and high load thresholds to 100% allows a cell to be excluded from LB procedures Setting the target threshold to a value XX% and high load thresholds to 100% allows a cell to accept offloaded UEs but does not allow to offload UEs to neighbors Thresholds can be set per load type to differentiate load levels per load type at which cell enters or exits active iF-LB states
Configuration Management
Main Menu
iFLBTargetLoadPdcch(2/2) LTE1170 - Inter-eNB Inter-Frequency Load Balancing
iFLBTargetLoadPdcch
Inter-Freq Load Balancing PDCCH Target Load DL
Object:
LNCEL
Range:
0%..100%
Step:
1%
Parameter Behavior: High Value of iFLBTargetLoadPdcch
Default:
50%
Multiplicity:
1
Unit:
%
Modification:
Online Modifiable
•
Category
Advanced
•
Link to PKDB
• More offloaded UEs can can be accepted by the cell from neighbor cells • Easier to exit from active iF-LB in terms of PDCCH load
Low Value of iFLBTargetLoadPdcch Low number of UEs can be offloaded due to CAC=0 can easily be reached Once cell enters active iF-LB state, it is difficult to exit active iF-LB state
Parameterization Rules: 1. Verify that iFLBTargetLoadPdcch ≤iFLBHighLoadPdcch 2. iFLBTargetLoadPdcch is mandatory when actInterFreqLB =“TRUE”
Configuration Management
Main Menu
LTE1170 - Inter-eNB Inter-Frequency Load Balancing
iFLBHighLoadGBRDL(1/2)
iFLBHighLoadGBRDL
Inter-Freq Load Balancing GBR High Load DL
Object:
LNCEL
Range:
0%..100%
Step:
1%
Default:
60%
Multiplicity:
1
Unit:
%
Modification:
Online Modifiable
Category:
Advanced
Parameter Behavior: The parameters iFLBHighLoadGBRDL defines the level of GBR load that triggers the entry to iF-LB Active state of a cell, i.e. start UE offloading to neighbor cells • Together with iFLBTargetLoadGBRDL, iFLBHighLoadGBRDL provides hysteresis between iF-LB state transitions Setting the target load thresholds to 0% and high load thresholds to 100% allows a cell to be excluded from LB procedures Setting the target threshold to a value XX% and high load thresholds to 100% allows a cell to accept offloaded UEs but does not allow to zoffload UEs to neighbors Thresholds can be set per load type to differentiate load levels per load type at which cell enters or exits active iF-LB states High Value of iFLBHighLoadGBRDL
Link to PKDB
• More GBR cell traffic handled by cell before triggering LB, i.e. delays offloading of UEs to neighbor cells
Low Value of iFLBHighLoadGBRDL • UEs are offloaded to neighbor cells earlier, cell enters active iF-LB earlier
Configuration Management
Main Menu
LTE1170 - Inter-eNB Inter-Frequency Load Balancing
iFLBHighLoadGBRDL(2/2)
iFLBHighLoadGBRDL
Inter-Freq Load Balancing GBR High Load DL
Object:
LNCEL
Range:
0%..100%
Parameterization Rules: 1. iFLBTargetLoadGBRDL ≤ iFLBHighLoadGBRDL
Step:
1%
Default:
60%
Multiplicity:
1
Unit:
%
Modification:
Online Modifiable
Category:
Advanced
Link to PKDB
2. iFLBHighLoadGBRDL is mandatory when actInterFreqLB =“TRUE” 3. When LTE497 (Smart Admission Control) is activated (actEnhAcAndGbrServices=true), care must be taken in setting iFLBHighLoadGBRDL • If maxGBRTrafficLimit < iFLBHighLoadGBRDL, admission control and congestion handling reduce/limit the load before iF-LB can act • Similarly, if maxGBRTrafficLimit > iFLBHighLoadGBRDL, offloading of Ues occurs first before load becomes high enough to trigger smart admission control actions
Configuration Management
Main Menu
LTE1170 - Inter-eNB Inter-Frequency Load Balancing
iFLBHighLoadNonGBRDL
Inter-Freq Load Balancing Non-GBR High Load DL
Object:
LNCEL
Range:
0%..100%
Step:
1%
Default:
85%
Multiplicity:
1
Unit:
%
Modification:
Online Modifiable
Category:
Advanced
Parameter Behavior: The parameters iFLBHighLoadNonGBRDL defines the level of non-GBR load that triggers the entry to iF-LB Active state of a cell, i.e. start UE offloading to neighbor cells • Together with iFLBTargetLoadNonGBRDL, iFLBHighLoadNonGBRDL provides hysteresis between iF-LB state transitions Setting the target load thresholds to 0% and high load thresholds to 100% allows a cell to be excluded from LB procedures Setting the target threshold to a value XX% and high load thresholds to 100% allows a cell to accept offloaded UEs but does not allow to offload UEs to neighbors Thresholds can be set per load type to differentiate load levels per load type at which cell enters or exits active iF-LB states High Value of iFLBHighLoadNonGBRDL • More non-GBR cell load handled by cell before triggering LB, i.e. delays offloading of UEs to neighbor cells Low Value of iFLBHighLoadNonGBRDL • UEs are offloaded to neighbor cells earlier, cell enters active iF-LB earlier Parameterization Rules: 1. iFLBTargetLoadNonGBRDL ≤ iFLBHighLoadNonGBRDL
Link to PKDB
Configuration Management
Main Menu
LTE1170 - Inter-eNB Inter-Frequency Load Balancing
iFLBHighLoadPdcch (1/2)
iFLBHighLoadPdcch
Inter-Freq Load Balancing PDCCH High Load DL
Object:
LNCEL
Range:
0%..100%
Step:
1%
Default:
80%
Parameter Behavior: The parameters iFLBHighLoadPdcch defines the level of PDCCH load that triggers the entry to iF-LB Active state of a cell, i.e. start UE offloading to neighbor cells
Multiplicity:
1
Unit:
%
Modification:
Online Modifiable
• Together with iFLBTargetLoadPdcch, iFLBHighLoadPdcch provides hysteresis between iF-LB state transitions
Link to PKDB
Setting the target load thresholds to 0% and high load thresholds to 100% allows a cell to be excluded from LB procedures Setting the target threshold to a value XX% and high load thresholds to 100% allows a cell to accept offloaded UEs but does not allow to offload UEs to neighbors Thresholds can be set per load type to differentiate load levels per load type at which cell enters or exits active iF-LB states High Value of iFLBHighLoadPdcch • More PDCCH cell load handled by cell before triggering LB, i.e. delays offloading of UEs to neighbor cells
Low Value of iFLBHighLoadPdcch • UEs are offloaded to neighbor cells earlier, cell enters active iF-LB earlier
Configuration Management
Main Menu
LTE1170 - Inter-eNB Inter-Frequency Load Balancing
iFLBHighLoadPdcch (2/2) iFLBHighLoadPdcch
Inter-Freq Load Balancing PDCCH High Load DL
Object:
LNCEL
Range:
0%..100%
Step:
1%
Parameterization Rules: 1. iFLBTargetLoadPdcch ≤ iFLBHighLoadPdcch 2. iFLBHighLoadPdcch is mandatory when actInterFreqLB =“TRUE”
Default:
80%
Multiplicity:
1
Unit:
%
Modification:
Online Modifiable
Link to PKDB
Configuration Management
Main Menu
LTE1170 - Inter-eNB Inter-Frequency Load Balancing
Target and High load threshold special configurations (1/4)
• Setting the target load thresholds to 0% and high load thresholds to 100% allows a cell to be excluded from LB procedures Special Case 1: Cell Exclusion from Load Balancing GBR/nGBR/PDCCH Cell Load GBR/nGBR/PDCCH High load = 100%
Load for any load type will never be below target=0%, will not exit active iF-LB state
AC is always 0%, cell will not accept any offloaded UEs from neighbor cells
GBR AC GBR/nGBR/PDCCH Target load = 0%
0% GBR Load 0%
Non-GBR AC PDCCH AC 0% Non-GBR Load 0%
0% PDCCH Load 0%
GBR
nGBR
PDCCH
Load
Load
Load
100%
100%
100%
Load for any load type will never exceed 100%, i.e. cell will never enter active iF-LB state
Configuration Management
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LTE1170 - Inter-eNB Inter-Frequency Load Balancing
Target and High load threshold special configurations (2/4)
• Setting the target threshold to a value XX% and high load thresholds to 100% allows a cell to accept offloaded UEs but does not allow to offload UEs to neighbors Special Case 2: Cell accepts offloaded UEs but never enter active iF-LB state GBR/nGBR/PDCCH Cell Load GBR/nGBR/PDCCH High load = 100%
Up to a certain level of cell load defined by target cell load, cell may be target for offloaded UEs
GBR
nGBR
PDCCH
Load
Load
Load
100%
100%
100%
GBR/nGBR/PDCCH Target load = XX% GBR Load A%
nGBR
PDCCH
Load
Load
B%
C%
Load for any load type will never exceed 100%, i.e. cell will never enter active iF-LB state
Configuration Management
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LTE1170 - Inter-eNB Inter-Frequency Load Balancing
Target and High load threshold special configurations (3/4)
• Thresholds can be set per load type to differentiate load levels per load type at which cell enters or exits active iF-LB states Special Case 3: Load Type Differentiation
GBR/nGBR/PDCCH Cell Load nGBR/PDCCH High load = 100% nGBR/PDCCH Target load = YY% GBR High load = XX%
Different threshold levels allows differentiation between load types
nGBR Load B%
GBR Target load = ZZ%
In this example, nGBR and PDCCH load never trigger cell’s entry to active iF-LB state; UEs will not be offloaded to this cell as GBR load has exceeded target GBR load
GBR
Load C%
Load A%
PDCCH
nGBRAC 0%
Configuration Management
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LTE1170 - Inter-eNB Inter-Frequency Load Balancing
Target and High load threshold special configurations (4/4)
• Setting the target threshold to 0% and high load thresholds to some value XX% makes the cell reject offloaded UEs and allows the cell to be in always active iF-LB state Not recommended Special Case 4: Cell always in Active iF-LB mode AC is always 0%, cell will not accept any offloaded UEs from neighbor cells
GBR/nGBR/PDCCH Cell Load
Cell enters active iF-LB state When cell enters active iF-LB state, cell will never exit due to load never going below target load. GBR/nGBR/PDCCH High load = XX%
nGBR Load B% GBR
PDCCH
Load
Load C%
A%
GBR/nGBR/PDCCH Target load = 0%
GBR AC
nGBR AC
0%
0%
PDCCH AC
GBR AC
nGBR AC
PDCCH AC
0%
0%
0%
0%
GBR Load nGBR Load PDCCH Load
Configuration Management
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LTE1170 - Inter-eNB Inter-Frequency Load Balancing
iFLBNomNumPrb (1/2)
iFLBNomNumPrb Object: Range:
Inter-Freq LB Nominal Number of PRBs Parameter Behavior: LNCEL The parameter iFLBNomNumPrb defines the estimated load contributed to the 1 (0.001), 2 (0.002), 5 (0.005), overall non-GBR cell load by a non-GBR bearer with scheduling weight=1 10 (0.01), 20 (0.02), 50 (0.05), 100 (0.1), 200 (0.2), 500 (0.5), 1000 (1), 2000 (2), 5000 (5), 10000 (10)
Default:
1000 (1)
Multiplicity:
1
Modification:
Online Modifiable
Category:
Advanced
Link to PKDB
• Non-GBR load can not be measured in similar manner as GBR load a single UE with non-GBR bearer may completely use all PRBs if there are no other UEs in the cell • Multiplying the parameter with the average sum of bearer weights results in the estimated non-GBR cell loaded for the cell
Higher Value: faster rate of change in measured non-GBR load with respect to change in sum of bearer scheduling weights • Faster to trigger entry and exit to active iF-LB • iF-LB state changes can be become more frequent difference between HighLoad and TargetLoad must be higher to have decent hysteresis between entering and leaving active iF-LB state • Faster to reach non-GBR target load less offloaded UEs accepted
Lower Value: slower rate of change in measured non-GBR load with respect to change in sum of bearer scheduling weights • Slower to trigger entry and exit t o active iF-LB • Slow to reach non-GBR target load more offloaded UEs accepted
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LTE1170 - Inter-eNB Inter-Frequency Load Balancing
iFLBNomNumPrb (2/2)
iFLBNomNumPrb
Inter-Freq LB Nominal Number of PRBs
Object:
LNCEL
Range:
1 (0.001), 2 (0.002), 5 (0.005), 10 (0.01), 20 (0.02), 50 (0.05), 100 (0.1), 200 (0.2), 500 (0.5), 1000 (1), 2000 (2), 5000 (5), 10000 (10)
Default:
1000 (1)
Multiplicity:
1
Modification:
Online Modifiable
Category:
Advanced
Link to PKDB
Parameterization Rules: 1. iFLBNomNumPrb must be configured with consideration to traffic profiles in the operators network • Take into consideration as well the average GBR PRB utilization and non-GBR PRB utilization measured from the field
2. If iFLBNomNumPrb is configured with a high value, it is recommended to increase the difference between iFLBHighLoadNonGBRDL and iFLBTargetLoadNonGBRDL to have decent hysteresis between entering and leaving active iF-LB state
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LTE1170 - Inter-eNB Inter-Frequency Load Balancing
iFLBBearCheckTimer (1/2)
iFLBBearCheckTimer Object:
LNCEL
Range:
1…30
Step:
1 sec
Default:
10 secs
Multiplicity:
1
Unit:
seconds
Modification:
Online Modifiable
Category:
Advanced
Link to PKDB
Inter-Freq Load Balancing QCI1 Bearer Check Timer Parameter Behavior: The parameter iFLBBearCheckTimer defines the amount of time to wait in order to check if QCI1 bearers are established by the UE before activation of A4 measurements The feature allows for voice users to be excluded from load balancing procedure to avoid risks of call drops For each UE that switches from Idle to Connected state, eNB waits for a time duration defined by iFLBBearCheckTimer • If UE establishes QCI1 bearer before iFLBBearCheckTimer expires, UE is not considered for offloading to neighbor cells (A4 not activated)
If iFLBBearCheckTimer is set to the special value 31, UE is included in candidate for offloading (A4 activated) regardless of QCI1 bearer establishment given that additional conditions for UE selection are met • The timer to wait before A4 activation is set to 1 second
Configuration Management
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LTE1170 - Inter-eNB Inter-Frequency Load Balancing
iFLBBearCheckTimer (2/2)
iFLBBearCheckTimer
Inter-Freq Load Balancing QCI1 Bearer Check Timer
Object:
LNCEL
Range:
1…30
Step:
1 sec
Parameter Behavior: Including and excluding QCI1 bearer UEs f or offloading affect gains derived from LTE1170 depending on networks traffic profile
Default:
10 secs
Multiplicity:
1
Unit:
seconds
Modification:
Online Modifiable
Category:
Advanced
Link to PKDB
• For instance, excluding QCI1 bearer UEs in a network where most UEs establish QCI1 bearers will have QCI1 UEs staying at t he highly loaded cell with minimal UEs offloaded
Higher Value: longer delay before LB actions can take effect Lower Value: higher possibility of QCI1 UEs included in UE candidates for offloading • Operators may require QCI1 to be excluded from UE candidate for offloading to minimize risk of call drops
Parameterization Rules: 1. It is recommended to align iFLBBearCheckTimer with average time of QCI1 bearer establishment in operator’s network
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LTE1170 - Inter-eNB Inter-Frequency Load Balancing
prohibitLBHOTimer
Prohibit Load Based Handover Timer
Object:
LNBTS
Range:
1 (1s), 2 (2s), 5 (5s), 10 (10s), 20 (20s), 50 (50s), 100 (100s)
Default:
10 (10s)
Multiplicity:
1
Unit:
seconds
Modification:
Online Modifiable
Parameter Behavior: If an UE is offloaded to a neighbor cell which does not have sufficient resources, the HO is rejected an d the neighbor cell is temporarily blacklisted in the source cell The parameter prohibitLBHOTimer defines the duration at which the neighbor cell is temporarily blacklisted for all LB-based HO requests from the source cell Higher Value: Longer time that the neighbor cell is temporarily blacklisted for load-based HOs
Category:
Advanced
Link to PKDB
• May delay effects of LB in cases when temporarily blacklisted neighbor cell is only heavily loaded for a short time
Lower Value: Shorter time that the neighbor cell is temporarily blacklisted for load-based HOs • Frequent load-based HO rejections occurs if neighbor cell’s load does not go below target threshold for each time temporary blacklisting is removed
LTE1170 – Inter-eNB Inter-Frequency Load Balancing Table of Contents
1
Introduction
2
Technical Details
3
Interdependencies
4
Configuration Management
5
Deployment Aspects
6
Benefits and Gains
Motivation and Feature Overview
Functionality and Implementation, Message Flows
Interdependencies with Other Features and Functions
Parameters and parameterisation scenarios
Feature Activation and Configuration Examples
Simulation, Lab and Field Findings
7
Performance Aspects Counters and KPIs, Feature Impact Analysis and Verification
Main Menu
Deployment Aspects LTE1170 - Inter-eNB Inter-Frequency Load Balancing
• Before enabling LTE1170, LTE55 Inter-frequency handover must be activated via actifHO flag
Main Menu
Deployment Aspects LTE1170 - Inter-eNB Inter-Frequency Load Balancing
Feature is enabled on eNB level via the activation flag actInterFreqLB
• Activation flag is common with RL40 LTE1387 Intra-eNB Inter-frequency Load Balancing feature
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Deployment Aspects
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LTE1170 - Inter-eNB Inter-Frequency Load Balancing
The LTE1170 feature is beneficial only for multi-layer LTE deployments with some level of coverage
overlap between different frequency layers • Overlap between frequency layers is needed to ensure sufficient RSRP/RSRQ of target cells for UE offloading • Verify that inter-frequency layers are configured (LNHOIF) • Verify that, for each LNHOIF object, RSRP (thresholdRsrpIFLBFilter ) and/or RSRQ (thresholdRsrqIFLBFilter ) thresholds are configured
Deployment Aspects
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LTE1170 - Inter-eNB Inter-Frequency Load Balancing
Verify that target and high load thresholds are configured
• Operator’s layering strategy must be taken into consideration in configuring the load thresholds Will all cells be involved in load balancing? Some cells will be UE offloading/accepting offloaded UEs only (unidirectional LB)? Will all load types trigger LB? Or will only specific types (i.e. GBR only, GBR + nGBR only, etc)
Deployment Aspects
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LTE1170 - Inter-eNB Inter-Frequency Load Balancing
Number of UEs that are capable of supporting the feature-needed functionalities (defined by FGI bits)
affects the gain derived from the feature FGI Bits 13
Description Inter-frequency Handover
14
A4 and A5 measurements/reporting
25
Inter-frequency measurements and reporting in connected mode
Gain from the feature is maximized for same coverage cells with different frequency carriers Higher probability that target cell/layer is seen with sufficient signal power and/or signal quality • A frequency layer(source layer/cell) must be sufficiently loaded to trigger entry to active iF-LB state Cell load reaches high load threshold • The inter-frequency neighbor cells must have low load to accommodate UE offloading Cell load is below target load thresholds • Sufficient amount of UEs switching to Idle state Low number of UEs which are “always on” and never go to idle •
LTE1170 – Inter-eNB Inter-Frequency Load Balancing Table of Contents
1
Introduction
2
Technical Details
3
Interdependencies
4
Configuration Management
5
Deployment Aspects
6
Benefits and Gains
Motivation and Feature Overview
Functionality and Implementation, Message Flows
Interdependencies with Other Features and Functions
Parameters and parameterisation scenarios
Feature Activation and Configuration Examples
Simulation, Lab and Field Findings
7
Performance Aspects Counters and KPIs, Feature Impact Analysis and Verification
Main Menu
Benefits and Gains
Main Menu
LTE1170 - Inter-eNB Inter-Frequency Load Balancing
Without LTE1170/LTE1387 100 90 80 ) 70 % ( d 60 a o 50 L l l 40 e C 30 20 10 0
With LTE1170/LTE1387 100 90 80 ) 70 % ( d 60 a o 50 L l 40 l e C 30 20 10 0
Fr eq1 Freq2
t0
t1
t2
t3
t4
t5
t6 t7 Time
t8
t9 t10 t11 t12
Freq1 Freq2 High Load Thresh Target Load Thresh
t0
Cell becomes overloaded and some UEs are not allocated resources
t1
t2
t3
t4
t5
t6 t7 Time
t8
t9 t10 t11 t12
New UEs connect to the cell and cell enters Active iF-LB state
New UEs connect to the cell
Incoming UEs switching from Idle to Connected
Benefits and Gains
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LTE1170 - Inter-eNB Inter-Frequency Load Balancing
With LTE1387 (RL40) Offloading to cells from other eNBs is possible in case same eNB cells are highly loaded
With LTE1170 (RL50)
Benefits and Gains
Main Menu
LTE1170 - Inter-eNB Inter-Frequency Load Balancing
Improved traffic distribution between layers •
Due to consideration of PDCCH load, CCE blocking rate is expected to decrease •
With LTE1387, if PDSCH utilization is below the configured high load threshold, LB will not be triggered despite Ues being blocked in PDSCH due to PDCCH scheduling
Average UE throughput is expected to improve due to UEs being offloaded to less loaded cells •
Depending on scenario, PDCP and RLC data volume increase on target cells for offloading
Without LTE1170, there is high probability of UEs being blocked in scheduling (PDSCH or PDCCH) in highly loaded cells
As a consequence of preventing further load increase in high load cells, ERAB setup failure due to lack of resource and ECM-IDLE to ECM-CONNECTED failure ratio due to Rejection by RRM RAC is reduced
Indirectly, improvements in distribution of average connected UEs can be observed
LTE1170 – Inter-eNB Inter-Frequency Load Balancing Table of Contents
1
Introduction
2
Technical Details
3
Interdependencies
4
Configuration Management
5
Deployment Aspects
6
Benefits and Gains
Motivation and Feature Overview
Functionality and Implementation, Message Flows
Interdependencies with Other Features and Functions
Parameters and parameterisation scenarios
Feature Activation and Configuration Examples
Simulation, Lab and Field Findings
7
Performance Aspects Counters and KPIs, Feature Impact Analysis and Verification
Main Menu
Performance Aspects
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LTE1170 - Inter-eNB Inter-Frequency Load Balancing
LTE1170 with CRL0893 introduces the following counters in RL50 to monitor the performance of the feature
Counter name
Description
HO_LB_ATT
This counter provides the number of LB-based HO attempts for both intra and inter-eNB LB-based HOs.
(M8021C23)
Trigger event: Transmission of an “RRC:Connection Reconfiguration” message indicating a load based HO command to the UE. Use case: Load Balancing based HO Success Ratio LB-HO SR (%) = 100 * HO_LB_SUCC / HO_LB_ATT = 100 * M8021C24 / M8021C23
Performance Aspects
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LTE1170 - Inter-eNB Inter-Frequency Load Balancing
LTE1170 with CRL0893 introduces the following counters in RL50 to monitor the performance of the feature
Counter name
Description
HO_LB_SUCC
This counter provides the number of successful LB HOs for both intra and inter-eNB LB-based HOs.
(M8021C24)
Trigger event: • Intra-eNB: Counter is updated upon reception of an internal message indicating successful IntraeNB load-based HO. • Inter-eNB via X2: Counter is updated upon reception of X2AP: UE CONTEXT RELEASE from target eNB in case received due to LB-based HO • Inter-eNB via S1: Counter is updated upon r eception of S1AP: UE CONTEXT RELEASE COMMAND from MME with cause value Radio Network Layer (Successful Handover) in case received due to LB-based HO Use case#1: Load Balancing based HO Success Ratio LB-HO SR (%) = 100 * HO_LB_SUCC / HO_LB_ATT = 100 * M8021C24 / M8021C23 Use case#2: Ratio of successful LB-based HOs to total successful inter-frequency HOs Ratio LB-HO to Total HO (%) = 100 * HO_LB_SUCC / HO_INTFREQ_SUCC = 100 * M8021C24 / M8021C2
Performance Aspects
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LTE1170 - Inter-eNB Inter-Frequency Load Balancing
LTE1170 with CRL0893 introduces the following counters in RL50 to monitor the performance of the feature
Counter name
Description
HIGH_CELL_LOAD_LB (M8011C69)
This counter provides the number of times that a cell is in active iF-LB st ate for the whole measurement period Trigger event: Every 1 second, the counter is incremented if cell is in active iF-LB state Use case#1: Duration of time (in minutes) at which the cell has been in active iF-LB stat e Time in active iF-LB (minutes) = HIGH_CELL_LOAD_LB / 60 = M8011C69 / 60 Use case#2: Percentage of time in active iF-LB state Percentage of time in active iF-LB (%) = 100* HIGH_CELL_LOAD_LB / (60*(aggregation period in minutes)) = 100* M8011C69 / (60*(aggregation period in minutes))
Performance Aspects
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LTE1170 - Inter-eNB Inter-Frequency Load Balancing
Load-Blind HO Performance Monitoring
At the highly- loaded cell, Inter-eNB HO preparation failure rate and the HO Preparation Failure due to admission control Distribution provide a measure of the intensity of load-blind HO failures when LTE1170 is activated • Increase in HO preparation failure rate and HO preparation failure due to admission control means that unsuccessful load-blind HOs are increasing FAIL_ENB_HO_PREP_TIME (M8014C2)
FAIL_ENB_HO_PREP_AC (M8014C3)
FAIL_ENB_HO_PREP_OTHER (M8014C5)
INTER_ENB_HO_PREP (M8014C0)
INTER_S1_HO_PREP_FAIL_TIME (M8014C15)
INTER_S1_HO_PREP_FAIL_NORR (M8014C16)
INTER_S1_HO_PREP_FAIL_OTHER (M8014C17)
INTER_ENB_S1_HO_PREP (M8014C14)
Inter-eNB HO preparation failure rate (%) = 100 * (FAIL_ENB_HO_PREP_TIME + FAIL_ENB_HO_PREP_AC + FAIL_ENB_HO_PREP_OTHER + INTER_S1_HO_PREP_FAIL_TIME + INTER_S1_HO_PREP_FAIL_NORR + INTER_S1_HO_PREP_FAIL_OTHER) / ( INTER_ENB_HO_PREP + INTER_ENB_S1_HO_PREP) Inter-eNB HO Preparation Failure due to AC Distribution (%) = 100 * (FAIL_ENB_HO_PREP_AC + INTER_S1_HO_PREP_FAIL_NORR ) / (FAIL_ENB_HO_PREP_TIME + FAIL_ENB_HO_PREP_AC + FAIL_ENB_HO_PREP_OTHER + INTER_S1_HO_PREP_FAIL_TIME + INTER_S1_HO_PREP_FAIL_NORR + INTER_S1_HO_PREP_FAIL_OTHER )
Further looking into details, HO preparation failure rate and HO preparation failure due to AC distribution can be derived per neighbor relation INTER_HO_PREP_FAIL_TIME_NB (M8015C6)
INTER_HO_PREP_FAIL_AC_NB (M8015C7)
INTER_HO_PREP_FAIL_OTH_NB (M8015C5)
Inter-eNB HO preparation failure rate per NB (%) = 100 * (INTER_HO_PREP_FAIL_TIME_NB + INTER_HO_PREP_FAIL_AC_NB + INTER_HO_PREP_FAIL_OTH_NB ) / (INTER_ENB_HO_PREP + INTER_ENB_S1_HO_PREP ) Inter –eNB HO Preparation Failure due to AC Distribution per NB (%) = 100 * (INTER_HO_PREP_FAIL_AC_NB) /
Performance Aspects
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LTE1170 - Inter-eNB Inter-Frequency Load Balancing
Feature impact on network performance Feature impact
How to measure
Improved Traffic Distribution
KPIs:
Note: Depending on scenario, traffic distribution may be improved due to UE offloading in high load scenarios. KPIs should be viewed on a cellby-cell level distribution
E-UTRAN PDCP SDU Volume DL (LTE_5212a)
Reduced CCE blocking
KPIs:
Note: Depending on scenario, CCE blocking may be reduced to UE offloading triggered by high PDCCH load.
CCE blocking = 100 * (1*AGG1_BLOCKED_PDCCH +
E-UTRAN PDCP SDU Volume UL (LTE_5213a) E-UTRAN RLC PDU Volume UL (LTE_5810a)
2*AGG2_BLOCKED_PDCCH + 4*AGG4_BLOCKED_PDCCH + 8*AGG8_BLOCKED_PDCCH) / (1*AGG1_USED_PDCCH +2* AGG2_USED_PDCCH + 4*AGG4_USED_PDCCH + 8*AGG8_USED_PDCCH + 1*AGG1_BLOCKED_PDCCH + 2*AGG2_BLOCKED_PDCCH +4* AGG4_BLOCKED_PDCCH + 8*AGG8_BLOCKED_PDCCH) AGG1_BLOCKED_PDCCH (M8011C43)
AGG2_BLOCKED_PDCCH (M8011C44)
AGG4_BLOCKED_PDCCH (M8011C45)
AGG8_BLOCKED_PDCCH (M8011C46)
AGG1_USED_PDCCH (M8011C39)
AGG2_USED_PDCCH (M8011C40)
AGG4_USED_PDCCH (M8011C41)
AGG8_USED_PDCCH (M8011C42)
Performance Aspects
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LTE1170 - Inter-eNB Inter-Frequency Load Balancing
Feature impact on network performance Feature impact
How to measure
Improved UE throughput
KPIs:
Note: UE throughput may improve due to UE offloading.
Currently there are no counters or KPIs that measure UE throughput. Tools for network
Improved UE Distribution
KPIs:
Note: Depending on scenario and strategy, UE distribution may be improved due to UE offloading to neighbor cells. KPIs should be viewed on a cell-by-cell level distribution.
Number of active users (users with data in buffer)
performance measurements are needed (eg. Iperf).
• E-UTRAN Average Active UEs with data in the buffer DL (LTE_5800b) • E-UTRAN Average Active UEs with data in the buffer UL (LTE_5801b) • Maximum Active UEs with data in the buffer per cell DL (LTE_5802a) • Maximum Active UEs with data in the buffer per cell UL (LTE_5803a) Number of connected users (with DRB) • E-UTRAN Average Active Connected Ues (LTE_5804b) • Active UE per eNB max (LTE_1082a) • E-UTRAN Average Active UEs with data in the buffer for DRBs of QCI1 DL (LTE_5805b) • E-UTRAN Average Active UEs with data in the buffer for DRBs of QCI2 DL (LTE_5559a) • E-UTRAN Average Active UEs with data in the buffer for DRBs of QCI3 DL (LTE_5560a) • E-UTRAN Average Active UEs with data in the buffer for DRBs of QCI4 DL (LTE_5561a) • E-UTRAN Average Active UEs with data in the buffer for non-GBR DRBs (QCI5..9) DL (LTE_5806b) • E-UTRAN Average Active UEs with data in the buffer for QCI1 DRBs UL (LTE_5807b) • E-UTRAN Average Active UEs with data in the buffer for non-GBR DRBs UL (LTE_5808b)
Performance Aspects
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LTE1170 - Inter-eNB Inter-Frequency Load Balancing
Note that LTE1170, with CRL0893, does not introduce changes to existing HO counters • A4 HO successes/attempts/failures will be counted in existing HO counters • When a cell is in active LB state, Inter-frequency HO attempts and successes are expected to increase
The LB-HO effects on HO counters may affect LTE533 MRO algorithm with CRL0923 • CRL0923 allows MRO algorithms to be applied as well to inter-frequency neighbor relations
Back-up Slides
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LTE1170 - Inter-eNB Inter-Frequency Load Balancing
BACK-UP SLIDES
Back-up slides
Main Menu
LTE1170 - Inter-eNB Inter-Frequency Load Balancing Load Supervision and Exchange
DL GBR Load Measurements
Candidate UE Selection for Measurement Solicitation
Measurement Solicitation
• DL GBR PRB Usage is already being obtained for LTE497 Smart Admission Control • The measured GBRload is post-processed in RAC as follows: Load GBR,DL(t)
aveUtil PRB DL,GBR
*100 aveAvail
PRB DL,GBR
Calculated based on information sent periodically (default: 500ms) from L2 QCI-specific scheduling weight of nonGBR bearer j
• L2 calculates average DL nGBR bearer QCI-specific weight sum
DL non-GBR Load Measurements
iF-LB Execution
nGBRWtSum(t ) 1
1 * nGBRWtSum(t 1) * scheduledW eight j T PRBave T PRBave jU (t ) 1
• L2 calculates average available PRB for DL non-GBR bearers aveAvail DL,nonGBR
PRB
aveAvail DL,GBR
PRB
aveUtil DL,GBR
PRB
• These results from L2 are forwarded to t he load balancing control
scheduledWeight j pertains to the non-GBR QCI-specific configurable weight parameter of nonGBR bearer j, schedulWeight
Set of bearers with data available for initial transmission Calculated based on information sent periodically (default: 500ms) from L2
• L2 provides pre-averaged PDCCH load to RAC
PDCCH Load Measurements
Load PDCCH (t )
1 1 1 ave * PDCCH Util _ LB (t 1) ave * PDCCH Util _ LB (t ) T PDCCH T PDCCH
Hard coded to 10 times the value of PDCCH link adaptation filter to assure that LB acts on long term basis compare to congestion handling
• PDCCHUtil_LB is calculated in L2 as the ratio of the number of CCEs used over the number of available CCEs • Available number of CCEs is calculated based on the configured maximum number of PDCCH symbols
Back-up slides
Table of Contents
Main Menu
LTE1170 - Inter-eNB Inter-Frequency Load Balancing Load Supervision and Exchange
Candidate UE Selection for Measurement Solicitation
Measurement Solicitation
iF-LB Execution
Non-GBR load calculations
•
Non-GBR Load is further processed, Load nGBR, DL (t ) min
iFLBNomNum Prb * max( 0.01; nGBRWtSum (t )) ; 1 *100 aveAvail PRB DL,nonGBR Operator configurable parameter for the nominal number of PRBs assigned for a non-GBR bearer with scheduledWeight=1.
•
Non-GBR load is calculated based on the average sum of scheduling weights of non-GBR UEs with data available for initial transmission in contrast to utilization-based calculations for GBR and PDCCH load
• •
Note that a single non-GBR UE may occupy the whole bandwidth of an empty cell
Care must be taken in configuring iFLBNomNumPrb
•
Value of iFLBNomNumPrb dictates how high or low the load is interpreted
Technical Details
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LTE1170 - Inter-eNB Inter-Frequency Load Balancing Load Supervision and Exchange
Candidate UE Selection for Measurement Solicitation
Measurement Solicitation
iF-LB Execution
Cell load filtering
• The load measurements are filtered as follows: Load GBR,DL(t) (1 ) * Load GBR,DL(t 1) * Load GBR,DL(t) Load nGBR,DL(t) (1 ) * Load nGBR,DL(t 1) * Load nGBR,DL(t) Load PDCCH (t) (1 ) * Load PDCCH (t 1) * Load PDCCH (t)
• Filtering prevents the algorithm from being overly sensitive to load measurement variations • Smoothing filter coefficient α is defined as follows:
1
2
iFLBLoadFilCoeff 4
Vendor parameter (non-modifiable, hidden) with default value =4 resulting in a smoothing filter coefficient α = 0.5.
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