Lte1841

1
For internal use
© Nokia Solutions and Networks 2014
LTE1841 - Inter Frequency
Load Equalization
Network Engineering Information
• Krzysztof Golebiewski
• 16-10-2014
Please always check the latest version of this
NEI slides!

5
For internal use
LTE1841 Inter Frequency Load Equalization
Table of contents
Simulation, Lab
and Field
Findings
Introduction
Motivation and
Feature Overview
Technical
Details
Detailed Functionality
Description
1
Inter –
dependenci
es
Interdependencies
with other features
and functions
Benefits
and Gains
Simulation, Lab and
Field Findings
Configuratio
n
Managemen
t
Parameters and
Parameterization
Scenarios
Deployment
Aspects
Activation,
Configuration
Examples, Fault
Mgmt, Trial Area
Performanc
e Aspects
Counters and KPIs,
Feature Impact
Analysis and
Verification
Compliance
Aspects
3GPP, IETF, ETSI

6
For internal use
Introduction
Table of contents

7
For internal use
Intra-Frequency
Inter-Frequency
Intra-LTE Inter-RAT
LTE1387 – Intra-eNB Inter-Frequency Load Balancing
(RL40)
LTE1387 – Intra-eNB Inter-Frequency Load Balancing
(RL40)
LTE1170 – Inter-eNB Inter-frequency Load Balancing
(RL50/RL35TD/RL50FZ)
LTE1170 – Inter-eNB Inter-frequency Load Balancing
(RL50/RL35TD/RL50FZ)
Connected Mode Load Balancing
Features
LTE1531 – Inter-frequency Load Balancing Extensions
(RL60/RL45TD)
LTE1531 – Inter-frequency Load Balancing Extensions
(RL60/RL45TD)
LTE487 – Idle Mode Load Balancing (RL50/RL35TD/RL50FZ)
CRL0632 – Basic Idle mode Load Balancing (RL40)
LTE1677 – Idle Mode Load Balancing Extensions (RL60/RL45TD)
LTE1140 – Intra-Frequency Load
Balancing (RL70/RL55TD)
LTE1140 – Intra-Frequency Load
Balancing (RL70/RL55TD)
LTE1841 – Inter Frequency Load Equalization
(RL70/RL55TD)
LTE1841 – Inter Frequency Load Equalization
(RL70/RL55TD)
LTE2050 – Load Triggered Idle Mode Load Balancing (RL70/RL55TD)
Idle Mode Load Balancing Features
Note: Arrows ( / ) signify the
extensions to features from previous
releases. The new/extension features
share the same activation flags as the
original features and aimed at adding
additional functionalities to legacy
features.
Introduction
Load Balancing Features Overview

8
For internal use
Introduction
• Inter-frequency Load Balancing (iF-LB) and Idle
Mode Mobility Load Balancing (IMMLB) features
offload/steer UEs towards inter-frequency/Inter-
RAT neighbour cells
- iF-LB offers reactive offloading when High Load
Threshold is reached
- The goal of iF-LB was not to equalize the load
between cells but rather to keep the load below
configured Target Load Threshold
- IMMLB features impact on cell load is visible
just after next enter to RRC Connected state
• Load Information available only within own eNB
- No Load information exchange between eNBs
• Load-Blind HO towards cell of neighbouring eNB
Pre-RL70
• Connected Mode Load Balancing
˗ LTE1387 Intra-eNB Inter-Frequency Load Balancing
˗ LTE1170 Inter-eNB Inter-Frequency Load Balancing
˗ LTE1531 Inter-Frequency Load Balancing Extensions
• Idle Mode Mobility Load Balancing
˗ LTE487 Idle Mode Mobility Load Balancing
˗ LTE1677 Idle Mode Mobility Load Balancing
Extensions

9
For internal use
Introduction
RL70
• Load Equalization (on top of existing
features)
˗ LTE1841 Inter Frequency Load
Equalization
• LTE1841 provides the possibility to equalize load
between inter frequency cells
- the load difference between partner cells is
maintained according to configured delta
• Candidate selection procedure for load equalization
is inherited from LTE1170/LTE1531
• DL GBR, DL non-GBR and PDDCH cell loads are
measured, in order to make a decision whether AMLE
- Active Mode Load Equalization phase should be
started or not
• Resource Status Reporting (RSR) procedure is used
to facilitate exchange of load information between
cells
- No Load-Blind HOs are triggered due to LTE1841
• when no Load information about cell is available, cell
will not be a target for Load Based HO for LTE1841

10
For internal use
Technical Details
Table of contents

11
For internal use
Technical Details
Dependency Table (LTE)
FDD LTE RL release eNodeB NetAct
Release/version RL70 LN7.0 NetAct 8 EP2
TDD LTE RL release eNodeB NetAct
Release/version RL55TD LNT5.0 NetAct 8 EP2
Flexi Zone Micro
(FZM)
RL release eNodeB NetAct
Release/version RL70/RL55 LNF7.0/LNZ5.0 NetAct 8 EP2
HW & IOT
HW
requirement
s
MME SAE GW UE
Specified by
3GPP
x FSME, FSMF x x Rel. 8

12
For internal use
Cell C
(Partner cell)
Cell C
(Partner cell)
Cell B
(Neighbour
cell)
Cell B
(Neighbour
cell)
• Goal of the feature: load equalization (LE)
between source cell and partner neighbour
cells
- Partner cell – neighbour cell of the same or
different eNB that uses partner frequency layer and
is AMLE allowed (LNREL:amleAllowed = true)
• The same set of parameters from AMLEPR is used for
all partner cells of partner frequency layer
- Partner frequency layer – frequency layer that is
configured in partnership for serving cell
- Partnership is created when frequency layer is
configured in any of Active Mode Load Equalization
Profile (AMLEPR): LNCEL:AMLEPR
• Intra frequency partnership is not supported
• Configuration of partnership is always done per
frequency layer
Technical Details
Cell A
(Source cell)
Cell A
(Source cell)
Inter Frequency Load Equalization overview
Load is being
equalized between
Source cell and
Partner cells only
Cell D
(Partner cell)
Cell D
(Partner cell)

13
For internal use
When feature is activated (LNBTS:actAmle = true) its behaviour
can be
reflected as 5 functional blocks
1) Load supervision and exchange:
• Measurements of CACS and exchange with neighbours
2) Check of active AMLE state conditions
• AMLE state of source cell is determined
3) Candidate UE selection
• When Inter Frequency Load Balancing QCI1 Bearer Check Timer or Inter
Frequency Load Balancing Retry Timer is expired UE is checked if it can
be Candidate for offloading
4) Measurement solicitation
• A4 measurements of partner neighbour frequencies are triggered
5) Load Equalization execution
• Target Cell List is post-processed, unsuitable cells are removed
• Inter frequency Handover preparation phase is started
Technical Details
Check of active
AMLE state
conditions
Check of active
AMLE state
conditions
Candidate UE
selection
Candidate UE
selection
Measurement
solicitation
Measurement
solicitation
Load Equalization
execution
Load Equalization
execution
Load supervision
and CAC exchange
Load supervision
and CAC exchange
AMLE feature
Inter Frequency Load Equalization overview
Partner Cell
Source Cell

14
For internal use
Technical Details
• PDCCH load (%) is defined as the averaged ratio of utilized CCEs to
total number of available CCEs
• DL GBR load (%) is defined as the ratio of the average DL GBR
utilization to the average available PRBs for dynamic scheduling
DL GBR Load Measurements
DL GBR Load Measurements
• 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
DL nonGBR Load Measurements
DL nonGBR Load Measurements
PDCCH Load Measurements
PDCCH Load Measurements
Source Cell
Partner Cell
Load Supervision
and CAC
exchange
Load Supervision
and CAC
exchange
AMLE feature
1) Load supervision and CAC exchange:
More details about Load Measurements can be found here & here.
From RL50 onwards all load types are measured: GBR, PDCCH and
nonGBR
• Load measurements are used for determination of Composite Available
Capacity that is used by AMLE, Intra-frequency Load Balancing and
others

15
For internal use
Technical Details
DL GBR
Measured Load
DL non-GBR
Measured Load
PDCCH
Measured Load
DL GBR Relative
Load
DL GBR Relative
Load
PDCCH Relative
Load
PDCCH Relative
Load
DL non-GBR
Relative Load
DL non-GBR
Relative Load
DL GBR
Available
Capacity
DL GBR
Available
Capacity
PDCCH
Available
Capacity
PDCCH
Available
Capacity
DL non-GBR
Available
Capacity
DL non-GBR
Available
Capacity
0%
100%
Cell LoadX [%]
50%
50%
50%
50%
ACX
RLX
50%
MLX
X = GBR, nonGBR, PDCCH
• Each measured DL Load (ML) is reflected as
Relative Load (RL)
˗ Relative Load defines measured load in relation
to configured Target Load Threshold (TL)
˗ Target Load Threshold is configured via
parameters:
LNCEL:LoadSettings:targetLoadGbrDl,
targetLoadNonGbrDl, targetLoadPdcch
˗ Relative load is a subcomponent in calculation
of DL Available Capacity (AC)
• Available Capacity = [100% - RL]
• DL Composite Available Capacity is the
minimum of all AC:
CACDL = min(ACGBR, ACnonGBR,
ACPDCCH)
25%
25%
TLX

16
For internal use
Technical Details
• In RL50/RL60 all types of load were
always taken for CACDL calculation
• From RL70 onwards user has impact on
which type of load is taken into account
for CACDL determination
• Parameter
LNCEL:loadSettings:mlbEicicOperMode is
used to control CAC calculation
˗ allUes – DL GBR, DL nonGBR, PDCCH loads
are considered
˗ nonGbrPdcch – DL nonGBR and PDCCH
loads are considered
˗ nonGbrOnly – only nonGBR load is
considered
LNCEL:loadSettings:mlbEicicOperM
ode
LNCEL:loadSettings:mlbEicicOperM
ode
allUes
allUes nonGbrPdcc
h
nonGbrPdcc
h nonGbrOnly
nonGbrOnly

17
For internal use
Technical Details
Resource Status Report (RSR)
• Procedure is used to derive information about CAC
of cells that belong to neighbouring eNBs
• A neighbour cell is requested to report load
information by LTE1841 if:
1. Neighbour cell is partner cell of source cell
2. The neighbour cell is not X2 blacklisted and it is not
blacklisted for HO
RSR procedure
facilitates load
information
exchange between
eNBs

18
For internal use
Technical Details
• The RSR consists of two basic procedures:
1. RSR Initiation (START/STOP) triggers the
start and stop of the periodic load
information reporting of one requested
cell
2. RSR Update is the periodic reporting of
load information
• RSR messages are exchanged via X2 only
Resource Status
Reporting (RSR)
RSR
Initiation
Initiation
(START)
Initiation
(STOP)
RSR Update

19
For internal use
Technical Details
• As RSR procedure is available, no Load-
blind HOs due to AMLE are triggered
- No CAC of target cell is known, no HOs
towards
this cell
• RSR Update message, as specified by
3GPP, requires both UL and DL CAC
- Only DL load is measured
- UL load can be reflected according to DL load
or it can be set to fixed value, depending on
LNCEL:ulCacSelection parameter setting
• LNCEL:ulCacSelection = ulStaticCac
(configured value of LNCEL:ulStaticCac is
always put as CACUL)
• LNCEL:ulCacSelection = ulReflectCac (CACUL =
CACDL)
“
u
l
F
i
x
e
d
C
a
c
”
IE/Group
Name Presence Range
IE type and
reference
Semantics
description Criticality
Assigned
Criticality
Composite
Available
Capacity
Downlink
M
Composite
Available
Capacity
3GPP TS
36.423
For the
Downlink
- -
Composite
Available
Capacity
Uplink
M
Composite
Available
Capacity
3GPP TS
36.423
For the
Uplink
- -
Composite Available Capacity Group IE used for RSR procedure
CACUL =
LNCEL:ulStaticC
ac
“
u
l
R
e
f
e
c
t
C
a
c
”
LNCEL:ulCacSelectio
n =
LNCEL:ulCacSelectio
n =
CACUL = CACDL

20
For internal use
Technical Details
Resource Status Update (RSU) message
• Resource Status Update message
contains LM information coming from
different eNB
• The first RSU is sent by responding eNB
as soon as first Load Measurements are
available
• Subsequent reporting is handled
according to Requested Periodicity
˗ If more than one feature activated on
Requesting eNB (like LTE1140 or LTE1113
among others) requires Load Measurements
from Responding eNB, the lowest periodicity
requested by all features is used
• Requested periodicity for LTE1841 is
defined by parameter
LNCEL:amlePeriodLoadExchange
Cel
l1
Cel
l1
…
Requesting eNB
X2AP: RSU
Cel
lX
Cel
lX
Cel
l1
Cel
l1
…
Responding eNB
Cel
lY
Cel
lY
Note:
Successful RSR Initiation of Cell1.
First Load Measurements are available on
Responding eNB
After each Requested periodicity RSU is sent again
X2AP:RSU (Cell1)
time
A
A B
B
Responding eNB
C
C C
C C
C C
C
A
A
B
B
C
C
Requested Periodicity
More details about RSR Procedure one can find here.

21
For internal use
Technical Details
LNCE
L
AMLEPR-0
amlePrId
cacHeadroom
deltaCac
maxCacThresho
ld
targetCarrierFre
q
Active mode load equalization profile identifier
Headroom in CAC
Target carrier frequency
Difference in CAC of source and target cells
Threshold for maximum CAC
Note:
When LTE1841 is activated (LNBTS:actAmle = true), at
least default AMLEPR-0 has to be configured
Source Cell
Partner Cell
Check of active
AMLE state
conditions
Check of active
AMLE state
conditions AMLE feature
When LTE1841 is enabled, source cell can
be in
active or inactive AMLE state with partner
cell
• Source Cell is in active AMLE state only
when:
1. It is not in Active Inter Frequency Load
Balancing (iFLB) State (applicable when
LTE1170/LTE1531 is activated)
2. There is at least one partner cell
configured
for source cell (LNREL:amleAllowed=true)

22
For internal use
Technical Details
When LTE1841 is enabled, source cell can be
in
cell
when:
3. Following criteria are met for configured
partner cell:
CRITERIUM 1: CACS <
AMLEPR:maxCacThreshold
CRITERIUM 2: CACT ≥ AMLEPR:cacHeadroom
CRITERIUM 3: CACT - CACS > AMLEPR:deltaCac
Source
maxCacThreshold
RL
S
CAC
S
TL
Note:
Each time when either Source cell CAC is updated (500ms)
or source eNB gets more up-to-date CAC of Target Cell (e.g.
via Resource Status Update), AMLE state of Source Cell is
rechecked

23
For internal use
Technical Details
Note:
rechecked
Partner
cacHeadroom
TL
RL
T
CAC
T
in
cell
when:
partner cell:
CRITERIUM 1: CACS <

24
For internal use
Technical Details
Note:
rechecked
Source Partner
RL
S
CACs
CACS
CACT
TL
∆CAC = CACT-CACS
RL
T
CAC
T
in
cell
when:
partner cell:
CRITERIUM 1: CACS <

25
For internal use
Technical Details
Load is equalized when CAC
deviation
between Source cell (CACS) and
CAC of
target Cell (CACT) is low enough
• the load difference between
partner cells is maintained
according to configured delta CAC
• Delta CAC
(LNCEL:AMLEPR:deltaCac) defines
maximum allowed CAC deviation
between Source cell and Target
cell
Load is equalized when:
CACT - CACS ≤
AMLEPR:deltaCac
Source Partner
maxCacThreshold
cacHeadroom
RL
S
CAC
S
CACT=70%
TL
∆CAC=10%
CACS=60%

26
For internal use
Technical Details
Example:
• 3 partner cells
• 2 partner frequency layers
AMLE State verification:
AMLE State verification:
PC1
f1
PC1
f1
PC2
f2
PC2
f2
PC3
f2
PC3
f2
CACPC1 CACPC2
CACPC3
Partner Cell (PC) of Source Cell (S)
CACS <
maxCacThresholdf1
CACS <
maxCacThresholdf1
CACS <
maxCacThresholdf2
CACS <
maxCacThresholdf2
CACS <
maxCacThresholdf2
CACS <
maxCacThresholdf2
CACPC2 ≥ cacHeadroomf2
STOP
STOP
CACPC2 – CACS>∆CACf2
CACPC2 – CACS>∆CACf2
STOP
STOP
AMLE INACTIVE
AMLE INACTIVE AMLE INACTIVE
AMLE INACTIVE
AMLE ACTIVE
AMLE ACTIVE
N
N
Y
Y
Y
Y

27
For internal use
Candidate UE Selection procedure is reused from
LTE1170/LTE1531
• Each time when either
˗ [point A] Inter Frequency Load Balancing QCI1
Bearer Check Timer
(LNCEL:iFLBBearCheckTimer) or
˗ [point B] Inter Frequency Load Balancing Retry
Timer (Tdyn = Int(max(#actUEs* div 60;1) x
LNCEL:iFLBRetryTimer)
is expired, UE selection criteria are checked
Technical Details Source Cell
Partner Cell
Candidate UE
Selection
Candidate UE
Selection
AMLE feature
3) Candidate UE Selection
time
B
B B
B
Note:
Inter Frequency LB Bearer Check Timer is
started
UE selection criteria are verified. Inter
Frequency Load Balancing Retry Timer (Tdyn)
is (re)started
A
A
B
B
A
A
UE enters RRC Connected State
or UE was handed over to the cell that is in
active AMLE state or active iFLB state
* #actUEs = the actual number of active UEs in the cell excluding UEs with configured
SCC (Secondary Component Carrier)

28
For internal use
Candidate UE Selection procedure is reused from
LTE1170/LTE1531
• Inter Frequency Load Balancing QCI1 Bearer
Check Timer is started every time when:
˗ UE either enters RRC Connection state or
˗ UE enters cell that is already in active AMLE state or
active iFLB state via Handover
• Inter Frequency Load Balancing Retry Timer is
started every time when:
˗ Inter Frequency Load Balancing QCI1 Bearer Check
Timer is expired
˗ Inter Frequency Load Balancing Retry Timer is expired
˗ UE enters cell that is neither in active AMLE state nor
active iFLB state via Handover
Technical Details
time
B
B B
B
Note:
Inter Frequency LB Bearer Check Timer is
started
UE selection criteria are verified. Inter
Frequency Load Balancing Retry Timer (Tdyn)
is (re)started
A
A
B
B
A
A
UE enters RRC Connected State
or UE was handed over to the cell that is in
active AMLE state or active iFLB state

29
For internal use
UE is a candidate for offloading only if it fulfills UE selection
criteria
1) Source Cell is in active AMLE state
2) UE supports at least one partner frequency layer that is used by
partner cell with which source cell is in active AMLE state
3) UE has no QCI1 bearer established (depending on
LNCEL:iFLBBearCheckTimer)
• UE with QCI1 established, analogously to iFLB feature, is considered to
be candidate for offloading only when LNCEL:iFLBBearCheckTimer =
31
4) UE has no GBR bearer established (depending on the
LNCEL:loadSettings:mlbEicicOperMode setting)
• UE with GBR bearer established can only be offloaded if GBR load is
taken into account during CAC calculation
(LNCEL:loadSettings:mlbEicicOperMode = allUEs)
5) UE has no Secondary Cell (SCell) configured
6) There are no ongoing inter-frequency or inter-RAT measurements for
the UE
7) Required functionalities, i.e. Inter frequency Handover and A4
Technical Details
Source
Cell
?
Partner
Cell

30
For internal use
For UE that is a candidate for offloading A4
measurements
are started, provided that maximum number of
concurrent
A4 measurements (LNCEL:iFLBA4ActLim) is not
reached
• s-measure in measConfig is set to 0
˗ s-measure=0 causes instant start of UE measurements
(regardless of RSRP level of serving cell)
• ReportConfigEUTRA is added in reportConfigToAddModList
˗ A4 configuration is hardcoded and not modifiable
• Activation of A4 is done by adding selected measObjectIds and
reportConfigIds to measIdToAddModList
˗ Partner frequency layers (measObjectIds) that are supported
by the UE and for which at least one partner cell is in active
AMLE state with source cell are added
• UE is informed about changes in measConfig via RRC
Connection Reconfiguration message
Partner Cell
Measurement
Solicitation
Measurement
Solicitation
AMLE feature
ReportConfigEUTRA (A4)
Parameter Name Set values
> Trigger Type event
>> eventId eventA4
>>> a4-Threshold
>>>> threshold-RSRP 0 (-140dBm)
>> hysteresis 0
>> Time To Trigger (TTT) 40ms
> Trigger Quantity RSRP
> Report Quantity Both(RSRP & RSRQ)
> MaxReportCells 8
> Report Interval 60min
> Report Amount 1
4) Measurement Solicitation

31
For internal use
RSRP
Neighb
or
A4 Measurement Reports (MR) are expected
to be
Received within max 3s (supervision timer)
after
A4 measurements start
• If at least one MR was received before
supervision timer expiration, Target Cell List
(TCL) is created
˗ The lowest possible threshold-RSRP is used. It
ensures that almost all cells are reported via A4
report
˗ further filtering process is required to remove
cells that are unsuitable due to RSRP and/or
RSRQ criteria
• Whenever inter-RAT or inter-frequency
measurements are started, A4 is deactivated
and UE will not be offloaded due to LE
˗ UE can still be Handed over to different cell via
Technical Details
RSRP
time
A4-threshold
= -140dBm
TTT=40ms
A4 Report
Sent
Note:
All cells with RSRP > -140dBm are reported . Further
post-processing and filtering unsuitable cells is
required.
Note:
All cells with RSRP > -140dBm are reported . Further
post-processing and filtering unsuitable cells is
required.
A4 event activation
• Set s-measure = 0
• Add measIDs in
measConfig
• Measurement gap
handling
• Send RRC Connection
Reconfiguration
A4 event activation
• Set s-measure = 0
• Add measIDs in
measConfig
• Measurement gap
handling
Reconfiguration
A4 event deactivation
• Set s-measure = threshold1
• Remove measIDs in
MeasConfig
• Measurement gap handling
Reconfiguration
A4 event deactivation
• Set s-measure = threshold1
• Remove measIDs in
MeasConfig
• Measurement gap handling
Reconfiguration
Lowest possible A4
RSRP threshold
allows for
measurement of
most of neighbor
cells
4) Measurement Solicitation

32
For internal use
Target Cell List (TCL) postprocessing
STEP 1: Removing unsuitable cells from TCL
• Cells with unsufficient level of RSRP/RSRQ according to filtering
parameters setting: LNHOIF:thresholdRsrpIFLBFilter and
LNHOIF:thresholdRsrqIFLBFilter
• Cells from different RAT (including cells of Home eNB when
LNBTS:actHeNBMobility is activated)
• Cells that are blacklisted for Load Based HO (LB HO)
• Cells with unknown CAC and with too low CAC [CACT <
AMLEPR:cacHeadroom] *
• Cells for which CAC of Source cell is too high [CACS >
AMLEPR:maxCacThreshold] *
• Cells that do not fulfill: CACT - CACS > AMLEPR:deltaCac *
• Number of AMLE HOs towards given cell, between two CAC updates
from this cell, is higher than LNCEL:amleMaxNumHo
Partner Cell
Load
Equalization
execution
Load
Equalization
execution
AMLE feature
All unsuitable
cells are
removed from
TCL
Note:
* Whenever more up-to-date CAC is available, AMLE state of each cell is
verified again
Note:
* Whenever more up-to-date CAC is available, AMLE state of each cell is
verified again

33
For internal use
Target Cell List (TCL) postprocessing
STEP 2: TCL sorting
• If there is at least one cell on TCL after STEP1, list is sorted
according to descending ∆CAC
• First candidate that is at the top of TCL is a partner target cell
with the biggest CAC deviation with source cell
Technical Details
The highest delta CAC
value determines
which target cell is the
first candidate to
accommodate UE from
the source cell

34
For internal use
HO preparation phase
• First cell from the top of TCL is considered to be
the first Target Cell
• Intra-eNB, X2 or S1-based handover is prepared
towards the chosen target cell with Handover
Cause =“Reduce Load in Serving Cell”
• Radio Admission Control (RAC) is responsible for
verification if given handover can be admitted
˗ Case 1) Successful HO preparation phase
• If target cell provides sufficient number of
resources to serve the UE, HANDOVER REQUEST
ACKNOWLEDGE message is sent to source eNB
 Handover Execution phase is performed
Technical Details
Target Cell
Source Cell
Handover Request
Ack.
Handover Request
Radio
Admission
Control
Radio
Admission
Control
Cause: Reduce Load in Serving Cell
End of HO preparation phase
End of HO preparation phase
X2 based Handover message
flow
NOTE: For simplicity, only X2 Load Based
Handover is described. In case of different
types of HO (intra-eNB, S1 based HO) proper
HO messages are used

35
For internal use
HO preparation phase
˗ Case 2) Unsuccessful HO
preparation phase
• If RAC of target cell rejects the HO
Request, HO Preparation failure with
proper cause is sent
- If RAC admits only some of UE`s
bearers, LBHO is cancelled by
source cell (cause: Partial HO)
• Target cell in which RAC rejects (or
partially admits) LBHO is blocked by
source cell to avoid next LBHOs
during time defined by
LNBTS:prohibitLBHOTimer
• In such case, HO towards the second
cell in TCL (if any) will be triggered
Technical Details
Target Cell
Source Cell
HO Preparation Failure
Cause: No Radio Resources
Available in
Target Cell/Transport
Resources
Unavailable
prohibitLBHoTimer
Handover Request
Cause: Reduce Load in Serving
Cell
Handover Request
Handover Request
Cause: Reduce Load in
Serving Cell
Admission
Control
Admission
Control
Cell
Cell
Handover Request
Other
Target Cell

36
For internal use
Technical Details
System behaviour after LTE1841 feature (de)activation:
• Feature is activated in source cell if LNBTS:actAmle is set to true
˗ Continuous Load Measurements are started if they have not been started yet
˗ CAC is exchanged with partner cells
• When Partner cell belongs to neighbour eNB, RSR procedure is established
˗ Whenever conditions for AMLE are fulfilled, UE can be offloaded to partner neighbour cell via Inter
Frequency Handover
• Feature is deactivated in source cell if LNBTS:actAmle is set to false
˗ Load Measurements are done only if other features require them, i.e. if LTE1841 was the only feature
that required Load Measurements, they are stopped
• If Load Measurements are stopped, RSR are stopped as well and there is no CAC exchange
˗ Already started AMLE actions like HO preparation and execution or A4 measurements are allowed to
be completed, however no new AMLE actions are triggered (e.g. no next A4 will be started)

37
For internal use
Interdependencies
Table of contents

38
For internal use
LTE55 – Inter Frequency Handover:
UE offloading is done via iFHO thus feature that
introduced that functionality has to be enabled
LTE1060 TDD - FDD handover:
Whenever FDD-TDD LB (or vice versa) shall be
supported, feature LTE1060 that introduced FDD-
TDD and TDD-FDD HO is required
Interdependencies
prerequisites

39
For internal use
LTE1387/LTE1170/LTE1531 – Inter frequency
Load
Balancing (iFLB) and extensions:
• When LNBTS:actInterFreqLB is true, Inter
Frequency Load Equalization works only if cell is
not in Active Load Balancing State (offloading
only to partner cells)
• Inter frequency LB will ensure offloading towards
all neighbouring frequency layers (faster Load
reduction in source cell) when Active iFLB state is
reached (High Load Threshold is exceeded)
• iFLB Features are not required to activate
LTE1841, however some mechanisms are reused
Interdependencies
extensions

40
For internal use
LTE1496 – eICIC – micro,
LTE1113 – eICIC – macro,
LTE2050 – Load Triggered Idle Mode Load Balancing
LTE1140 – Intra Frequency Load Balancing
• All of features outlined above enable CAC calculation
and exchange (RSR)
˗ Load Equalization is possible with each partner cell, in which
Load measurements and CAC exchange is initialized
• Activation of LTE1841 is not required in a partner neighbour cell
Interdependencies
extensions

41
For internal use
LTE1089 – Downlink carrier aggregation - 20
MHz
LTE1332 – Downlink carrier aggregation - 40
MHz
Carrier Aggregation (CA) behavior provides natural ‘Load
Balancing’ characteristic. As a result, if SCell is
configured for UE, it is not a candidate for offloading.
Moving UEs that are configured for CA does not have to
be beneficial. It is not known if SCell will be able to be
added for new source cell
• LTE1089 and LTE1332 can be activated in parallel with
LTE1841
• AMLE algorithm will stop at step 3 (Candidate UE Selection)
when SCell is configured for UE
Interdependencies
extensions

42
For internal use
LTE1382 – Cell Resource Groups
LTE1382 causes incorrect load calculation and
thus calculated CAC is useless. As whole
mechanism is based on CAC, usage improper CAC
for Load Equalization can cause for example: high
load in target cell, significant deteriorate of iFHO
Success Ratio
•LTE1382 cannot be activated in parallel with
LTE1841
Interdependencies
limitations

43
For internal use
Benefits and Gains
Table of contents

44
For internal use
Feature is intended to equalize load of cells that cover similar area
• The maximum gain is for cells of the same coverage
• UEs are offloaded between partner cells before source cell enters Active iFLB State
˗ Thanks to Proactive UE distribution between cells, High Load Threshold is expected to be
exceeded less frequently
• Improved UE distribution is visible faster
˗ AMLE is expected to reduce number of Load-blind HOs which are a result of using
LTE1387/LTE1170/LTE1531. Load Equalization functionality, in contradiction to Inter
Frequency Load Balancing, takes into account CAC of all target cells and CAC has to be
available
• Increased number of Inter Frequency Handovers is expected as well as improved overall LB HO Success
Ratio
˗ Improved UE TP might be observed (cell by cell level)
Note: There are neither simulations nor tests done so far, as a result there is no confirmation what is really
impacted by LTE1841. This section will be updated when the results will be available
Benefits and Gains

45
For internal use
Configuration
Management
Table of contents

46
For internal use
• Definition of terms and rules for parameter classification*
* - purpose: categories of parameters have been defined to simplify network parameterization. Parameterization effort shall be focused mainly on parameters
included in basic category. Categorization is reflected in a ‘view’ definition in NetAct CM Editor (released in RL60) i.e. parameters will be displayed according to
the category: either in the ‘Basic parameters’ view or the ‘Advanced parameters’ view.
Configuration Management
The ‘Basic Parameters’ category
contains primary parameters which should
be considered during cell deployment and
must be adjusted to a particular scenario:
• 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, basic parameters defining feature behaviour
The ‘Basic Parameters’ category
contains primary parameters which should
be considered during cell deployment and
must be adjusted to a particular scenario:
• 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, basic 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 violated
• All parameters (even without defaults) related to
advanced and very complex features
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 violated
• All parameters (even without defaults) related to
advanced and very complex features

47
For internal use
Abbreviated name Full name PKDB link
LNBTS:actAmle
Activate active mode load
equalization
LNCEL:AMLEPR:amlePrId
Active mode load equalization
profile identifier
LNCEL:AMLEPR:targetCarrierFreq Target carrier frequency
LNREL:amleAllowed
Active mode load equalization
allowed
New basic parameters

48
For internal use
LNCEL:AMLEPR:cacHeadroom Headroom in CAC
LNCEL:AMLEPR:deltaCac
Difference in CAC of source and
target cells
LNCEL:AMLEPR:maxCacThreshold Threshold for maximum CAC
LNCEL:loadSettings:ulCacSelection Uplink CAC source selection
LNCEL:loadSettings:ulStaticCac Static CAC for uplink
LNCEL:loadSettings:mlbEicicOperMo
de
Mode for calculating the CAC in load
bal. and eICIC
LNCEL:loadSettings:nomNumPrbNon
Gbr
Nominal number of PRBs for load
balancing
LNCEL:loadSettings:targetLoadGbrDl DL GBR resource target load
New advanced parameters

49
For internal use
LNCEL:loadSettings:targetLoadNonG
brDl
DL non-GBR resource target load
LNCEL:loadSettings:targetLoadPdcch PDCCH target load
LNCEL:loadSettings:cellCapClass Cell capacity class value
LNCEL:amlePeriodLoadExchange
X2 resource status update
periodicity
New advanced parameters

50
For internal use
LNHOIF:thresholdRsrpIFLBFilter
Inter-freq load bal threshold for
RSRP target filter
LNHOIF:thresholdRsrqIFLBFilter
Inter-freq load bal threshold for
RSRQ target filter
Related basic parameters

51
For internal use
LNCEL:iFLBBearCheckTimer
Inter-frequency load balancing QCI1
Bearer check timer
LNBTS:prohibitLBHOTimer Prohibit Load based handover timer
Related advanced parameters

52
For internal use
Deployment
Aspects
Network graphic boxes Network element boxes
Table of contents

53
For internal use
LTE1841 is activated on eNB level
Target frequency layers have to be configured in AMLE Profiles
• Each AMLEPR is a configuration set related to all cells of one frequency layer
- Neighbour cell can be a partner neighbour cell only if LNREL:amleAllowed = true
Deployment Aspects
 true
deltaCac
cacHeadroom
targetCarrierFreq
maxCacThreshold  true

54
For internal use
Feature LTE1841 is intended to equalize the CAC between source cell and
partner cells
• CAC is the min(ACGBR,ACnonGBR,ACPDCCH). It is determined in relation to configured target load threshold
• Different value of target load threshold can be configured at source cell and the target cell
• While LTE1841 will equalize the CAC (with accuracy of LNCEL:AMLEPR:deltaCac), it does not necessarily
equalize the Measured Load
Deployment Aspects
TL
0%
100%
Cell Load [%]
50%
50%
50%
50%
66%
Source Cell Partner Cell
40%
50%
50%
50%
50% Composite Available Capacity (CAC)
Measured Load = 33%
Measured Load = 20%
TL
Composite Available Capacity (CAC)
Relative Load = 50%
Note:
For simplicity, in given scenario it is assumed
that only nonGBR is taken into account. All
threshold and variables corresponds to nonGBR
load (e.g. CACnonGBR, Related loadnonGBR and so
on)
Note:
For simplicity, in given scenario it is assumed
that only nonGBR is taken into account. All
threshold and variables corresponds to nonGBR
load (e.g. CACnonGBR, Related loadnonGBR and so
on)

55
For internal use
Frequency layer prioritization for different frequency layers
• Different parametrization of separate AMLEPR structures is possible (configuration is
done per target frequency layer)
Deployment Aspects
0%
Source
Cell (A)
C
C
B
B
A
A
Partner
Cell (B)
0%
Source
Cell (A)
Partner
Cell (C)
40%
40%
60%
60%
20%
20%
80%
80%
40%
40%
60%
60%
20%
20%
80%
80%
LNCEL:AMLEPR-(C):maxCacThreshold = 50%
LNCEL:AMLEPR-(B):maxCacThreshold = 70%
NOTE:
Different LNCEL:AMLEPR:maxCacThreshold for different frequency layer causes certain prioritization in terms of
what should be equalized first.
Different LNCEL:AMLEPR:deltaCac introduces different meaning for equalized load between target frequency layers.
NOTE:
Different LNCEL:AMLEPR:maxCacThreshold for different frequency layer causes certain prioritization in terms of
what should be equalized first.
Different LNCEL:AMLEPR:deltaCac introduces different meaning for equalized load between target frequency layers.

56
For internal use
Multivendor scenario issues
• Definition of CAC is specified by 3GPP, however calculation methodology is preserved for
eNB vendor
- Different CAC calculation method between different vendors might cause undesired UE offloading
• Example: CAC is determined according to full cell capacity, not Target Load Threshold. UE can be offloaded
despite the fact that cell of other vendor eNB is more loaded than cell of NOKIA eNB
Deployment Aspects
TLX
0%
100%
Cell Load X [%]
50%
50%
50%
50%
66%
X – GBR, nonGBR, PDCCH
Source Cell
NOKIA eNB
Partner Cell
Other vendor eNB
Measured Load = 33%
Relative Load = 50%
Measured Load = Relative Load = 40%
60%
40%
40%
60%
60%
No Target Load Threshold in other vendor eNB!

57
For internal use
Performance
Aspects
Table of contents

58
For internal use
Performance Aspects
New counters
Cell DL Composite Available Capacity
(DL CAC)
Description
DL_CAC_EQUAL_ZERO (M8011C81)
DL_CAC_ABOVE_0_BELOW_EQ_20
(M8011C82)
(M8011C83)
(M8011C84)
(M8011C85)
(M8011C86)
(LTE Cell Resource)
This set of counters provides the number of instances that
the measured downlink CAC falls into certain range.
Trigger event: Every second, the Cell DL Composite
Available Capacity (CAC) is measured by an eNB internal
measurement. Value of measured CAC is compared with each
range and proper counter is incremented.
Use case: This counter is used to generate a histogram plot
for the cell’s DL CAC over the measurement period. The
histogram plot gives insight to the cell’s load distribution over
the measurement period.
#
M8011C81
M8011C82
M8011C83
M8011C84
M8011C85
M8011C86

59
For internal use
Performance Aspects
Related counters
Number of load balancing Handover
attempts
Description
HO_LB_ATT (M8021C23) This counter provides the number of LB-based HO attempts for
both intra and inter-eNB LB-based HOs (regardless of LBHO was
triggered by iFLB or AMLE)
Trigger event: Transmission of an “RRC:Connection
Reconfiguration” message indicating a load based HO command to
the UE.
Number of successful load balancing
Handover completions
Description
HO_LB_SUCC (M8021C24) This counter provides the number of successful LB HOs for both
intra and inter-eNB LB-based HOs (regardless of LBHO was
triggered by iFLB or AMLE)
Trigger event:
Intra-eNB: Counter is updated upon reception of an internal
message indicating successful Intra-eNB 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 reception of S1AP: UE
CONTEXT RELEASE COMMAND from MME with cause value Radio
Network Layer (Successful Handover) in case received due to LB-
based HO

60
For internal use
Performance Aspects
Related counters
High cell load Indicator for Load
Balancing
Description
HIGH_CELL_LOAD_LB
(M8011C69)
This counter provides the number of times that a cell is in active
iFLB state for the whole measurement period
Trigger event: Every 1 second, the counter is incremented if cell
is in active iFLB state

61
For internal use
Performance Aspects
Related counters
Number of load balancing Handover
attempts
Description
HO_INTFREQ_ATT (M8021C0) This counter provides The number of intra LTE inter-frequency
Handover attempts. It comprises both the intra- and inter-eNB
HOs.
Trigger event:
intra-eNB HO: This counter is updated following the transmission
of an RRC Connection Reconfiguration message sent by the eNB to
the UE, which indicates a Handover Command to the UE in case
that this message is sent in response to the preparation of an
inter-frequency Intra eNB Handover.
inter-eNB HO-via X2: This counter is updated following the
reception of an X2AP:HANDOVER REQUEST ACKNOWLEDGE
message from the target eNB in case that this message is received
in response to the preparation of an inter-frequency Inter eNB
Handover.
inter-eNB HO-via S1: This counter is updated following the
reception of an S1AP:HANDOVER COMMAND message from the
MME in case that this message is received in response to the
preparation of an inter-frequency Inter eNB Handover.

62
For internal use
Performance Aspects
Related counters
Number of successful inter-frequency
Handover completions
Description
HO_INTFREQ_SUCC (M8021C2) The number of successful intra LTE inter-frequency Handover
completions. It comprises the intra- and inter-eNB Handover
scenario.
Trigger event:
intra-eNB HO: This counter is updated following the reception of
an internal message in case that it is received for an inter-
frequency Intra eNB Handover.
inter-eNB HO-via X2: This counter is updated following the
reception of an X2AP:UE CONTEXT RELEASE message from the
target eNB for an inter-frequency Inter eNB Handover.
inter-eNB HO-via S1: This counter is updated following the
reception of an S1AP:UE CONTEXT RELEASE COMMAND message
from the MME with the cause value Radio Network Layer
(Successful Handover) in case that this message is received for an
inter-frequency Inter eNB Handover.

63
For internal use
Performance Aspects
Feature monitoring
Feature impact How to measure?
Improved Traffic Distribution
Note: Depending on scenario, traffic
distribution may be improved due to UE
offloading between partner frequency
layers. KPIs should be investigated on a
cell-by-cell level distribution
KPIs:
• E-UTRAN PDCP SDU Volume DL (LTE_5212a)
• UTRAN PDCP SDU Volume UL (LTE_5213a)
• E-UTRAN RLC PDU Volume UL (LTE_5810a)
Improved UE Distribution
Note: Depending on scenario, UE
distibution may be improved due to UE
offloading between partner frequency
layers. KPI should be investigated on a
cell-by-cell level distribution.
Some selected KPIs:
• Number of active users (users with data in buffer)
• E-UTRAN Average Active UEs with data in the buffer DL (LTE_5800d)
• E-UTRAN Average Active UEs with data in the buffer UL (LTE_5801d)
• 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_5804c)
• Active UE per eNB max (LTE_1082a)
• E-UTRAN Average Active UEs with data in the buffer for DRBs of QCI1 DL (
LTE_5805c)
LTE_5559b)
LTE_5560b)
LTE_5561b)
• E-UTRAN Average Active UEs with data in the buffer for non-GBR DRBs
(QCI5..9) DL (LTE_5806c)
• E-UTRAN Average Active UEs with data in the buffer for QCI1 DRBs UL (

64
For internal use
Performance Aspects
Feature monitoring
Feature impact How to measure?
Increased number of Inter Frequency
Handovers and improved iFHO SR
Note: Feature uses iFHO as a mechanism
that enables UE offloading. When feature
is active, increased number of iFHOs is
expected. Due to the fact that number of
Load Blind HO should be reduced,
improved Success Ratio (SR) is expected
KPIs:
• E-UTRAN Inter-Frequency HO Success Ratio (SR) (LTE_5114a
)
Increased signalling load on X2
interface
Note: Continuous RSR messages exchange
between eNBs will cause increased load
on X2
Monitoring of mentioned impact can be done via:
• M8004C0 (X2 data volume per eNB, incoming signaling
data) and
• M8004C1 (X2 data volume per eNB, outgoing signaling
data)

65
For internal use
Compliance
Aspects
Table of contents

66
For internal use
Compliance Aspects
• 3GPP 36.423 defines the standard for Resource Status Reporting procedure
• Some factors affect the reliability of AMLE functionality towards another vendor
˗ Composite Available Capacity(CAC) is defined as one of the Load Measurement that is communicated via
X2 Resource Status Reporting. However way of calculation of CAC is left to the vendors
• A Nokia eNB serving as the Requesting eNB includes only one cell per Resource Status Request
message.
˗ If cell from another vendor’s eNB request multiple cells in one RSR message, this is still supported by Nokia
eNB
• Note that Nokia eNB only calculate DL CAC. UL CAC can either reflect calculated value for DL or take a
fixed configurable value

67
For internal use

68
For internal use
Hidden parameters
LNBTS:reportTimerIFLBA4
Inter-frequency load balance
supervision timer A4 event
LNBTS:iFLBA4ActLim Inter Freq Load Bal A4 active limit
LNBTS:iFLBLoadExchangePeriod
Inter-frequency load balance load
exchange periodicity

69
For internal use
References
Reference
Th. Stark + CFAM Team – LTE1841 Inter Frequency Load 1 Equalization CFAM
John Torregoza – NEI for LTE1140 Intra-Frequency Load Balancing
Katarzyna Rybianska – NEI for 1127 Service based mobility trigger

70
For internal use
Abbreviations
Abbreviation Explanation
AMLE Active Mode Load Equalization
RSR Resource Status Report(ing)
iFLB Inter Frequency Load Balancing
iFHO Inter Frequency Handover
NR Neighbour Relation
TL Target Load
ML Measured load
RL Relative Load
AC Available Capacity
CAC Composite Available Capacity

Lte1841

Recommended

Recommended

More Related Content

What's hot

What's hot (20)

Similar to Lte1841

Similar to Lte1841 (20)

Recently uploaded

Recently uploaded (20)

Lte1841