Best Neighbor Relations for Intra-LTE Load

Management

FEATURE DESCRIPTION

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Copyright

© Ericsson AB 2014-2015. All rights reserved. No part of this document may be

reproduced in any form without the written permission of the copyright owner.

Disclaimer

The contents of this document are subject to revision without notice due to
continued progress in methodology, design and manufacturing. Ericsson shall
have no liability for any error or damage of any kind resulting from the use
of this document.

Trademark List

All trademarks mentioned herein are the property of their respective owners.
These are shown in the document Trademark Information.

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 Contents

Contents

1 Introduction 1
1.1 Basic Characteristics 1
1.2 Benefits 2
1.3 Additional Information 2

2 Feature Operation 3
2.1 Network Requirements 3
2.2 Best Neighbor Relations for Intra-LTE Load Management
Operation 3
2.3 Process Steps 4
2.4 Configuration Guidelines 6

3 Parameters 9
3.1 Introduced Parameters 9
3.2 Affected Parameters 9

4 Network Impact 11
4.1 Throughput 11

5 Associated Features and Affected Functions 13

5.1 Prerequisite Features 13
5.2 Affected Features 13
5.3 Related Features 13
5.4 Affected System Functions 14

6 Performance 15
6.1 KPIs 15
6.2 Counters 15
6.3 Events 15

7 O&M Information 19
7.1 Feature Activation and Deactivation 19

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Best Neighbor Relations for Intra-LTE Load Management

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 Introduction

1 Introduction

This document describes the Best Neighbor Relations for Intra-LTE Load
Management feature and its main benefits and impacts in the LTE RAN.

The purpose of the feature is to evaluate whether inter-frequency neighbor

cells are suitable for inter-frequency load balancing or inter-frequency offload.
Suitable inter-frequency neighbor cells are automatically and dynamically
configured as load balancing relations.

The feature Best Neighbor Relations for Intra-LTE Load Management is used in
combination with one of the following features in order to identify the suitable
EUTRAN target load balancing relations to be used for load balancing/offload:

• Inter-frequency Load Balancing

• Inter-Frequency Offload

1.1 Basic Characteristics

This section describes the basic characteristics of the feature.

Feature name: Best Neighbor Relations for Intra-LTE Load

Management

Product identity:
DU-based node, see Feature Overview.

Baseband-based node, see Licensed Feature Overview.

Replaces: N/A

Dependencies

This feature requires at least one of the following RAN features to be active:

• Inter-frequency Load Balancing

• Inter-Frequency Offload

This feature also requires the following RAN feature to be active:

• Coverage-Triggered Inter-Frequency Handover

This feature affects no other features.

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 Best Neighbor Relations for Intra-LTE Load Management

1.2 Benefits
This section describes the benefits of this feature.

• It reduces the need for manual configuration of load management relations.

0 This automatic configuration is crucial in the network deployments

with several frequency layers and different cell grids where manual
configuration is difficult and tedious.

• Dynamic configuration of load management relations improves load

management efficiency .

0 This automatic configuration is crucial in the network. By considering

actual suitable targets and removing unsuitable targets, the load
balancing relation list is optimized and is used to determine the
amount of traffic load that must be handed over to each target cell.
Additional unsuitable target cells in the list reduce the chance of utilizing
suitable targets and can also increase the number of unnecessary
UE measurements.

1.3 Additional Information

More information about this feature and related topics can be found in the
following documentation:

• 3GPP TS 36.300, Overall description; Stage 2

• 3GPP TS 36.331, Radio Resource Control (RRC); Protocol Specification

• 3GPP TS 36.423, X2 Application Protocol (X2AP)

• Inter-frequency Load Balancing

• Inter-Frequency Offload

• Inter-RAT Offload to WCDMA

• Best Neighbor Relations for WCDMA IRAT Offload

• Coverage-Adapted Load Management

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 Feature Operation

2 Feature Operation

This section describes the Best Neighbor Relations for Intra-LTE Load
Management feature in more detail, including network configuration
requirements and operation flows.

2.1 Network Requirements

This is a licensed feature. This means that for the feature to be operational, a
valid license key must be installed and the feature must be explicitly activated
by setting a MOM attribute.

The following must be fulfilled at feature activation:

• A license key must be activated to operate the Coverage-Triggered

Inter-Frequency Handover feature.

See Coverage-Triggered Inter-Frequency Handover for a description on

how to activate the feature.

• A license key must be activated to operate the Inter-frequency Load

Balancing feature or Inter-Frequency Offload feature.

0 See Inter-frequency Load Balancing for a description on how to activate

the feature.

0 See Inter-Frequency Offload for a description on how to activate the

feature.

• A license key must be activated to operate the Best Neighbor Relations

for Intra-LTE Load Management.

See Section 7.1 on page 19 for a description on how to activate the feature.

• Load management between cells in different RBS nodes requires an X2

connection between the RBS nodes if inter-frequency load balancing is
required.

2.2 Best Neighbor Relations for Intra-LTE Load

Management Operation
The feature Best Neighbor Relations for Intra-LTE Load Management is a
continuous process that tries to automatically and dynamically determine and
configure which neighbor relations that each source cell can use for load
management by using hit-rate estimation.

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 Best Neighbor Relations for Intra-LTE Load Management

Hit-rate is defined as the likelihood of a UE candidate in the source cell to be

qualified for load balancing/offload to a certain target cell. It is assumed to
reflect the target cell coverage with respect to the UE density and distribution in
the source cell, rather than the geographical overlap. Target cells that cover
high-density areas in the source cell are better suited for load balancing or
offload than target cells that cover low-density areas. UE measurement is used
to estimate the hit-rate value for each target cell.

The resulting hit-rate for each cell relation is compared to reference thresholds
to decide whether load balancing/offload to this target cell is to be allowed.
The output of the feature is the updated MOM attribute loadBalancing of
MO EUtranCellRelation when applicable. This result is then used in the
load balancing/Inter-Frequency Offload features.

2.3 Process Steps

This section describes the main process steps for the feature flow.

2.3.1 UE measurements for hit-rate Estimation

To estimate the hit-rate value for each target cell, a number of UEs in the
source cell are required to measure on target frequencies. Note that this is
done regardless of whether neighbor relations are already configured for load
management on a frequency relation. The same measurements with the same
thresholds, as in load management (A5) are used for EUTRAN targets.

Measurements initiated for load management can be used to estimate

the hit-rate. When the number of measurements is not enough, extra
measurements are initiated to feed the hit-rate estimation.

2.3.2 Determine Best Neighbor Relations

The resulting hit-rate for each cell relation is compared to reference thresholds
to decide whether load balancing/offload to this target cell is to be allowed.

If hit-rate for an E-UTRAN neighbor relation exceeds lbHitRateEutranAddT

hreshold, the relation is considered suitable for load management. If hit-rate
is lower than lbHitRateEutranRemoveThreshold, the cell relation is not
considered suitable.

Figure 1 shows the process of automatic configuration of E-UTRAN neighbor

relations for load management.

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 Feature Operation

The algorithm is triggered every load balancing cycle

and performed for each E-UTRAN neighbor relation

No Is the feature BNR

for intra-LTE Load Mgmt
operable?

Yes

IbHitRate > No IbHitRate < No

IbHitRateEutranAddThreshold? IbHitRateEutranRemoveThreshold?

Yes Yes

FALSE IbBnrAllowed? IbBnrAllowed? FALSE

(MO EutranCellRelation) (MO EutranCellRelation)

TRUE (default) TRUE (default)

NOT_ALLOWED IbBnrPolicy? IbBnrPolicy? NOT_ALLOWED

(MO EutranFreqRelation) (MO EutranFreqRelation)

OFFLOAD_ONLY LB_ONLY
AUTO (default)
AUTO (default) LB_ONLY

No Is target cell Is target cell No

Ericsson RBS? Ericsson RBS?

Yes Yes

LoadBalancing = OFFLOAD LoadBalancing = ALLOWED LoadBalancing = NOT ALLOWED

Automatic configuration of the

E-UTRAN neighbor relation is complete

L0000790A

Figure 1 Automatic Configuration of E-UTRAN Neighbor Relations for Load Management

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 Best Neighbor Relations for Intra-LTE Load Management

• lbHitRateEutranAddThreshold and lbHitRateEutran

RemoveThreshold are configurable parameters, under MO
LoadBalancingFunction.

• lbBnrAllowed is a configurable parameter, under MO

EUtranCellRelation, used to control if this feature is allowed to
automatically change the loadBalancing attribute for the neighbor
relation.

• lbBnrPolicy is a configurable parameter, under MO EUtranFreqRelat

ion, used to control how this feature is allowed to automatically change
the loadBalancing attribute for neighbor relations associated with the
frequency relation.

• loadBalancing is a configurable parameter, under MO

EUtranCellRelation, which can either be manually updated by the
operator or automatically by this feature. Manual settings overwritten.

Note: When the Coverage-Adapted Load Management feature is operable,

new conditions are added in the algorithm. For more information,
see Coverage-Adapted Load Management, section Load Balancing
Relation Configuration.

2.4 Configuration Guidelines

This section describes the configuration guidelines for using Best Neighbor
Relations for Intra-LTE Load Management feature.

In order to activate Best Neighbor Relations for Intra-LTE Load Management,

either Inter-frequency Load Balancing, or Inter-Frequency Offload, or both
must be configured.

2.4.1 Inter-frequency Load Balancing

Details configuration of Inter-frequency Load Balancing. See Inter-frequency
Load Balancing.

2.4.2 Inter-Frequency Offload

Details configuration of Inter-Frequency Offload. See Inter-Frequency Offload.

2.4.3 Best Neighbor Relations for Intra-LTE Load Management

The minimum time it takes to find suitable load balancing relations or remove
unsuitable relations depends on the following:

• The configured lbHitRateEutranMeasUeIntensity, MO

LoadBalancingFunction for hit-rate estimation. It specifies the number
of UE measurements for hit-rate estimation at load balancing cycles per

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 Feature Operation

E-UTRAN frequency. When many load management measurements are

ongoing, updating of load balancing relations is faster because these
measurements are also used for hit-rate estimation. To find load balancing
relations faster, it is recommended to set the measurement intensity
lbHitRateEutranMeasUeIntensity, MO LoadBalancingFunction
to a higher value at feature introduction, especially in networks with
non-colocated deployment. The intensity level can be reduced afterwards
to reduce the number of measurements.

• The configured thresholds to add/remove load balancing relations. The

threshold for adding relations lbHitRateEutranAddThreshold can
be reduced to add relations faster. But it is recommended to consider a
minimum difference of 5-10% between thresholds lbHitRateEutranAdd
Threshold and lbHitRateEutranRemoveThreshold . To prevent
the removal of load balancing relations, it is possible to set the threshold for
removing relations lbHitRateEutranRemoveThreshold to 0 .

Note: When the Coverage-Adapted Load Management feature is

operable the BNR feature gets updated with the required capability
to give faster and more adaptive hit-rate estimations. Depending
on the configuration of the lbHitRateEutranAddThreshold
and lbHitRateEutranRemoveThreshold parameters, more
frequent updates on the loadBalancing parameter including
corresponding AVC notifications, may be experienced. It is
recommended to have at least 10% gap between the thresholds
above.

• The configured threshold for starting hit-rate measurements:

lbHitRateEutranMeasUeThreshold which specifies the minimum
number of connected users in the source cell required to allow initiation of
UE measurements for hit-rate estimation on E-UTRAN.

• The number of connected UEs in the source cell, UE distribution and UE

capabilities. Assuming that there are enough number of RRC connected
UEs in the source cell, it is expected that at least the first suitable target cell
for load management is found within some hours.

• The number of defined frequency relations with lbBnrPolicy not set to

NOT_ALLOWED. Parameter lbBnrPolicy is a configurable parameter per
frequency relation, MO EUtranFreqRelation. The parameter specifies
how the loadBalancing attribute of cell relations during the frequency
relation must be updated by this feature. If the lbBnrPolicy is configured
to NOT_ALLOWED for a frequency relation, no UE measurements for hit-rate
estimation can be initiated on the frequency. Any other setting of parameter
lbBnrPolicy than NOT_ALLOWED indicate that UE measurements for
hit-rate estimation must be initiated on E-UTRAN frequencies. If many
defined frequency relations for load management exist, the hit-rate
estimation pace can be reduced.

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 Parameters

3 Parameters

This section describes parameters introduced by the Best Neighbor Relations

for Intra-LTE Load Management feature and parameters affected by activating
the feature.

3.1 Introduced Parameters

Table 1 describes the parameters introduced by the feature.

Table 1 Introduced Parameters

Parameter Description
lbHitRateEUtranMeasUeThres Defined in MOM class LoadBalancingFunction which
hold specifies the required minimum number of connected users in
the source cell to allow initiation of UE measurements for hit-rate
estimation on E-UTRAN frequencies.
lbHitRateEUtranAddThreshold Defined in MOM class LoadBalancingFunction. EUtran cell
relations with a hit-rate value greater than this threshold are
considered suitable for load management.
lbHitRateEUtranRemoveThres Defined in MOM class LoadBalancingFunction. EUtran
hold cell relations with a hit-rate value lower than this threshold are
considered NOT suitable for load management.
lbHitRateEUtranMeasUeInten Defined in MOM class LoadBalancingFunction which
sity specifies the number of UE measurements for lbHitRate
estimation, per cell and Load Balancing cycle, for each E-UTRAN
frequency.
lbBnrPolicy Defined in MOM class EUtranFreqRelation which specifies the
policy for updating the loadBalancing attribute by the feature Best
Neighbor Relations for Intra-LTE Load Management. The policy is
valid for all cell relations corresponding to this EUtranFreqRelation.
lbBnrAllowed Defined in MOM class EUtranCellRelation which specifies
if the feature Best Neighbor Relations for Intra-LTE Load
Management is allowed to automatically change the loadBalancing
attribute for this EUtran cell relation.

3.2 Affected Parameters

Table 2 describes the parameters affected by the feature.

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 Best Neighbor Relations for Intra-LTE Load Management

Table 2 Affected Parameters

Parameter Description
loadBalancing Defined in MOM class EUtranCellRelation which will be
updated by the feature Best Neighbor Relations for Intra-LTE
Load Management. It indicates if Inter-Frequency Load Balancing
is ALLOWED or NOT_ALLOWED or if Inter-Frequency OFFLOAD
must be applied from the current cell towards the referenced
target EUTRAN cell.
lastModification Defined in MOM class EUtranCellRelation which will be
updated by the feature Best Neighbor Relations for Intra-LTE Load
Management. It indicates whether the MO was last modified by
the Automated Neighbor Relations (ANR) function or operator or
X2 or Load Management Function and if the MO that triggered the
deletion is to be deleted.

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 Network Impact

4 Network Impact

This section describes how the Best Neighbor Relations for Intra-LTE Load
Management feature impacts the network functions and capabilities.

4.1 Throughput
The additional UE measurements that this feature introduces are inter-frequency
measurements. As a result of this, they will require a measurement gap
depending on UE capability. If the number of UEs with a measurement gap are
increased, the data throughput is expected to decrease.

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 Associated Features and Affected Functions

5 Associated Features and Affected

Functions

This section describes how the Best Neighbor Relations for Intra-LTE Load
Management feature affects other features and functions.

5.1 Prerequisite Features

Table 3 lists prerequisite features to the Best Neighbor Relations for Intra-LTE
Load Management feature, that is, at least one of them must be active prior
to introducing the Best Neighbor Relations for Intra-LTE Load Management
feature.

Table 3 Prerequisite Features

Feature Description
Inter-frequency Load Balancing The feature Best Neighbor Relations for Intra-LTE Load
Management is used in combination with Inter-frequency Load
Balancing in order to identify the suitable EUTRAN target load
balancing relations to be used for load balancing.
Inter-Frequency Offload The feature Best Neighbor Relations for Intra-LTE Load
Management is used in combination with Inter-Frequency
Offload in order to identify the suitable EUTRAN target load
balancing relations to be used for offload.

5.2 Affected Features

Table 4 lists features that are affected by the Best Neighbor Relations for
Intra-LTE Load Management feature.

Table 4 Affected Features

Feature Description
Inter-frequency Load The Best Neighbor Relations feature adds/removes load
Balancing balancing relations used in Inter-frequency Load Balancing. If
the intensity of hit-rate measurements is set to a high value, it
may increase the speed of Inter-frequency Load Balancing.
Inter-Frequency Offload The Best Neighbor Relations feature adds/removes load
balancing relations used in Inter-Frequency Offload. If the
intensity of hit-rate measurements is set to a high value, it may
increase the speed of inter-Frequency Offload.

5.3 Related Features

Table 5 lists features that are related to the Best Neighbor Relations for
Intra-LTE Load Management feature.

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 Best Neighbor Relations for Intra-LTE Load Management

Table 5 Related Features

Feature Description
Mobility Control at Poor Coverage When the feature Mobility Control at Poor Coverage is operable,
the UEs in the search zone are probably fully configured with
mobility measurements and have no more resources for load
management measurements. If many of the UEs in the cell are
in the search zone, a lower number of UEs may be successfully
configured with load management measurements which results
in a slower hit-rate estimation and a slower load balancing/offload
pace.
Best Neighbor Relations for This feature provides the functions to automatically find and
WCDMA IRAT Offload evaluate suitable WCDMA IRAT offload neighbor relations for
WCDMA RIAT offload.
Coverage-Adapted Load This feature optimizes the amount of load to be transferred to
Management neighboring cells and also amount of required UE measurements
for load balancing purposes. It also allows handling large number
of load balancing relations with better efficiency which facilitates
load balancing towards small cells.
Carrier Aggregation-Aware IFLB When the feature Carrier Aggregation-Aware IFLB is operable
more UE measurements will be started which might reduce the
number of measuremens that BNR could start. To estimate the
hit-rate value for each target cell by BNR, a number of UEs in the
source cell are required to measure on target frequencies.

5.4 Affected System Functions

Table 6 lists functions affected by the Best Neighbor Relations for Intra-LTE
Load Management feature.

Table 6 Affected System Functions

Function Description
Inter-frequency The number of inter-frequency measurements increases when the Best
measurements Neighbor Relations feature is activated. The amount of extra measurements
depends on the configured attributes for hit-rate measurement intensity and
the number of defined frequency layers.
RRC Signalling Signaling intensity is expected to increase eventually due to an additional
number of RRC reconfigurations to start/stop measurements on the UEs and
the increased number of received measurement reports.

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 Performance

6 Performance

This section describes performance indicators, counters, and events associated

with the Best Neighbor Relations for Intra-LTE Load Management feature.

6.1 KPIs
This feature has no associated Key Performance Indicators (KPI).

6.2 Counters
Table 7 lists the counters associated with the Best Neighbor Relations for
Intra-LTE Load Management feature.

Table 7 Counters
Counter Description
pmLbMeasuredUe Records the number of UEs selected for measurements that
qualify for load management action towards cells on the related
frequency.
pmLbQualifiedUe Records the number of UEs qualified for load management action
towards the related cell.

More information about counters can be found in Managed Object Model

(MOM).

6.3 Events
Table 8 lists the events associated with the Best Neighbor Relations for
Intra-LTE Load Management feature.

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 Best Neighbor Relations for Intra-LTE Load Management

Table 8 Events
Event Event Parameter
INTERNAL_EVENT_UE_LB EVENT_PARAM_FREQ
_MEAS
EVENT_PARAM_TRIGGERING_FU Indicates the function that has
NCTION triggered the UE measurement and
consequently the measurement
report:

• Load Balancing (LB)

• Carrier Aggregation (CA)
triggered redirection
• Best Neighbor Relation (BNR) for
load balancing
EVENT_PARAM_UE_CA_CAPABLE Indicates whether the UE
selected for load balancing
related measurements is Carrier
Aggregation (CA) capable.
EVENT_PARAM_NEIGHBOR_CGI Cell Global Identity (CGI) of
neighbor target cells for which the
UE fulfilled the criteria for event A5.
EVENT_PARAM_TRAVERSED_UES Number of UEs checked and
discarded before choosing this
UE for load balancing related
measurements.

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 Performance

Event Event Parameter

INTERNAL_EVENT_UE_LB EVENT_PARAM_NEIGHBOR_CGI CGI of neighbor target cells for
_QUAL which UE fulfilled event A5 criteria
EVENT_PARAM_HO_SOURCE_OR_T Indicates the Radio Access
ARGET_TYPE Technology (RAT) of the source cell
for incoming handover, or target cell
for outgoing handover.
EVENT_PARAM_LB_CANCELLED_ Indicates the reason for not
REASON proceeding with a Load Balancing
(LB) or Carrier Aggregation (CA)
triggered redirection action when
a measurement report has been
received from the UE:

• CA criteria not met

• Reported cell is not a valid load
balancing target
• Reported cell is a valid target,
but lbAmount has already been
satisfied for the cell
• Service Specific Load
Management (SSLM) related
restrictions
• Reference Signal Received
Quality (RSRQ) of target cell is
below configured threshold
• UE has signalled interest in
Multimedia Broadcast Multicast
Service (MBMS) service on
serving frequency
• UE has an ongoing Voice over IP
(VoIP) call and does not support
Single Radio Voice Call Continuity
(SRVCC)
EVENT_PARAM_TRIGGERING_FU Indicates the function that has
NCTION triggered the UE measurement and
consequently the measurement
report:

• Load balancing
• CA triggered redirection
• Best Neighbor Relation (BNR) for
load balancing

More information about events can be found in PM Event List (DU-based node)
or Lists (Baseband-based node).

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 O&M Information

7 O&M Information

This section provides Operation and Maintenance (O&M) information for the
Best Neighbor Relations for Intra-LTE Load Management feature.

7.1 Feature Activation and Deactivation

Activating the feature requires that the corresponding license is installed. When
the license is installed, an MO instance BnrIntraLteLM is automatically
created.

Table 9 Feature MO Instance

Node type MO instance
DU-based node MO instance is OptionalFeatureL
icense=BnrIntraLteLM
Baseband-based node MO instance is FeatureState=Bnr
IntraLteLM

Feature activation and deactivation is described in Manage Licenses.

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