mlb lte load control mechanismm

eRAN

MLB Feature Parameter Description

Issue 04Date 2013-10-30

HUAWEI TECHNOLOGIES CO., LTD.

Copyright Huawei Technologies Co., Ltd. 2013. All rights reserved.No part of this document may be reproduced or transmitted in any form or by any means without prior writtenconsent of Huawei Technologies Co., Ltd. Trademarks and Permissions

and other Huawei trademarks are trademarks of Huawei Technologies Co., Ltd.All other trademarks and trade names mentioned in this document are the property of their respective holders. NoticeThe purchased products, services and features are stipulated by the contract made between Huawei and thecustomer. All or part of the products, services and features described in this document may not be within thepurchase scope or the usage scope. Unless otherwise specified in the contract, all statements, information,and recommendations in this document are provided "AS IS" without warranties, guarantees or representationsof any kind, either express or implied.

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Website: http://www.huawei.comEmail: [email protected]

Issue 04 (2013-10-30) Huawei Proprietary and ConfidentialCopyright Huawei Technologies Co., Ltd.

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Contents

1 About This Document..................................................................................................................11.1 Scope..............................................................................................................................................................................11.2 Intended Audience..........................................................................................................................................................11.3 Change History...............................................................................................................................................................12 Overview.........................................................................................................................................42.1 Basic Concepts...............................................................................................................................................................52.1.1 Cell Load.....................................................................................................................................................................52.1.2 Service Type................................................................................................................................................................52.1.3 Source Cell and Target Cell.........................................................................................................................................62.2 MLB Procedure..............................................................................................................................................................63 Inter-Frequency Load Balancing................................................................................................83.1 Load Measurement and Evaluation................................................................................................................................93.2 Load Information Exchange...........................................................................................................................................93.2.1 Neighboring Cell Selection.........................................................................................................................................93.2.2 Inter-eNodeB Cell Load Information Exchange........................................................................................................103.3 Load Balancing Decision..............................................................................................................................................103.4 Load Balancing Execution............................................................................................................................................113.5 Performance Monitoring...............................................................................................................................................124 Inter-RAT Load Sharing.............................................................................................................134.1 Load Measurement and Evaluation..............................................................................................................................144.2 Load Sharing Decision.................................................................................................................................................144.3 Load Sharing Execution...............................................................................................................................................144.3.1 Transferring UEs in Connected Mode.......................................................................................................................154.3.2 Transferring UEs in Idle Mode..................................................................................................................................164.4 Performance Monitoring...............................................................................................................................................165 Related Features...........................................................................................................................175.1 Features Related to LOFD-001032 Intra-LTE Load Balancing...................................................................................175.2 Features Related to LOFD-001044 Inter-RAT Load Sharing to UTRAN...................................................................175.3 Features Related to LOFD-001045 Inter-RAT Load Sharing to GERAN...................................................................186 Network Impact...........................................................................................................................19

eRANMLB Feature Parameter Description Contents


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6.1 LOFD-001032 Intra-LTE Load Balancing...................................................................................................................196.2 LOFD-001044 Inter-RAT Load Sharing to UTRAN...................................................................................................196.3 LOFD-001045 Inter-RAT Load Sharing to GERAN...................................................................................................207 Engineering Guidelines.............................................................................................................217.1 When to Use MLB........................................................................................................................................................217.2 Required Information...................................................................................................................................................217.3 Planning........................................................................................................................................................................217.3.1 RF Planning...............................................................................................................................................................217.3.2 Network Planning......................................................................................................................................................227.3.3 Hardware Planning....................................................................................................................................................227.4 Deployment..................................................................................................................................................................227.4.1 Requirements.............................................................................................................................................................227.4.2 Data Preparation........................................................................................................................................................227.4.3 Precautions.................................................................................................................................................................327.4.4 Activation..................................................................................................................................................................327.4.5 Activation Observation..............................................................................................................................................367.4.6 Deactivation...............................................................................................................................................................447.5 Performance Monitoring...............................................................................................................................................457.6 Parameter Optimization................................................................................................................................................477.7 Troubleshooting............................................................................................................................................................478 Parameters.....................................................................................................................................509 Counters......................................................................................................................................10510 Glossary.....................................................................................................................................10811 Reference Documents.............................................................................................................109

eRANMLB Feature Parameter Description Contents


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1 About This Document1.1 Scope

This document describes mobility load balancing (MLB), including its technical principles,related features, network impact, and engineering guidelines.This document covers the following features:l LOFD-001032 Intra-LTE Load Balancingl LOFD-001044 Inter-RAT Load Sharing to UTRANl LOFD-001045 Inter-RAT Load Sharing to GERANAny managed objects (MOs), parameters, alarms, or counters described herein correspond tothe software release delivered with this document. Any future updates will be described in theproduct documentation delivered with future software releases.This document applies only to LTE FDD. Any "LTE" in this document refers to LTE FDD, and"eNodeB" refers to LTE FDD eNodeB.

1.2 Intended AudienceThis document is intended for personnel who:l Need to understand the features described hereinl Work with Huawei products

1.3 Change HistoryThis section provides information about the changes in different document versions. There aretwo types of changes, which are defined as follows:l Feature change

Changes in features of a specific product versionl Editorial change

eRANMLB Feature Parameter Description 1 About This Document


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Changes in wording or addition of information that was not described in the earlier version

04 (2013-10-30)This issue includes the following changes.

Change Type Change Description Parameter ChangeFeature change None NoneEditorial change Revised 3.4 Load Balancing Execution and

4.3.1 Transferring UEs in ConnectedMode.

None


Change Type Change Description Parameter ChangeFeature change In inter-RAT load sharing to UTRAN, deleted

the exchange of load information aboutneighboring UTRAN cells through RANInformation Management (RIM) procedures.

None

Editorial change None None


Change Type Change Description Parameter ChangeFeature change None NoneEditorial change Optimized some descriptions in 7.4.2 Data

Preparation and 7.4.4 Activation.None


Change Type Change Description Parameter ChangeFeature change None None



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Change Type Change Description Parameter ChangeEditorial change Optimized the descriptions of

types of services that triggerinter-frequency loadbalancing and inter-RATload sharing. For details, see3 Inter-Frequency LoadBalancing and 4 Inter-RATLoad Sharing.

None

Draft A (2013-01-30)Compared with Issue 05 (2012-12-29) of eRAN3.0, Draft A (2013-01-30) of eRAN6.0 includesthe following changes.

ChangeType

Change Description Parameter Change

Featurechange

In inter-RAT load sharing toUTRAN, added the exchange ofload information aboutneighboring UTRAN cellsthrough RIM procedures.

Added the MlbLoadInfoSwitch(MlbLoadInfoSwitch) option to theCellAlgoSwitch.MlbAlgoSwitchparameter.

Removed intra-frequency loadbalancing.

Removed the parameters for intra-frequency load balancing.

Added the switches of blindhandover for inter-frequencyand inter-RAT MLB. Fordetails, see 3.4 Load BalancingExecution and 4.3.1Transferring UEs inConnected Mode.

Added the CellAlgoSwitch.MlbHoModeparameter.

Added the configuration of thenumber of UEs that can betransferred in an MLB period.For details, see 3.4 LoadBalancing Execution.

Added the CellMLB.LoadTransferFac-tor parameter.

Editorialchange

Revised the description of inter-RAT load sharing.

None



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2 OverviewMobility load balancing (MLB) coordinates load distribution among inter-frequency cells tomaximize network resource usage. To achieve these goals, MLB checks the load status of cells,exchanges cell load information, and transfers load from heavily loaded cells to lightly loadedcells. In addition, MLB can transfer load to inter-RAT cells to reduce the E-UTRAN congestionrate, increase the access success rate, and improve user experience with services.

NOTE

RAT is short for radio access technology.

MLB can be classified into inter-frequency load balancing and inter-RAT load sharing.MLB involves the following optional features:l LOFD-001032 Intra-LTE Load Balancingl LOFD-001044 Inter-RAT Load Sharing to UTRANl LOFD-001045 Inter-RAT Load Sharing to GERAN

eRANMLB Feature Parameter Description 2 Overview


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2.1 Basic Concepts2.1.1 Cell Load

MLB considers the following types of loads: air interface load, hardware load, and transportnetwork layer load, as shown in Figure 2-1.

Figure 2-1 Different types of loads and their positions

l The air interface load is represented by the uplink (UL) and DL PRB usages in each cell.For details about how to calculate the PRB usage, see section 4.1.1 in 3GPP TS 36.314V10.2.0 (2011-09).

l The hardware load is represented by the hardware resource usage, such as the centralprocessing unit (CPU) and digital signal processing (DSP) hardware usage.

l The transport network layer load is represented by the S1 bandwidth usage. For details, seeTransport Resource Management Feature Parameter Description.

According to section 9.2.36 in 3GPP TS 36.423 V10.5.0 (2012-03), the hardware and transportnetwork layer loads can be in one of the following states: LowLoad, MediumLoad, HighLoad,and Overload.3900 series eNodeBs currently support only MLB triggered by the air interface load.In RAN sharing scenarios, cell load is measured on a per cell basis, not on a per operator basis.

NOTEFor concepts related to RAN sharing, see RAN Sharing Feature Parameter Description.

2.1.2 Service TypeServices are categorized into guaranteed bit rate (GBR) services and non-GBR services in theuplink and downlink. The GBR services and non-GBR services combined are referred to as total



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services. In MLB, the eNodeB determines the load balancing type based on the percentage ofresources occupied by each type of service.

2.1.3 Source Cell and Target CellA source cell is the cell from which MLB transfers the load. In this document, a source cell isalso referred to as a serving cell.A target cell is a neighboring cell to which MLB transfers the load.

2.2 MLB ProcedureMLB can be performed between inter-frequency and inter-RAT cells. A cell can be configuredwith one or both of the two types of neighboring cells. When both types are configured, the typeof neighboring cells to which the load should be transferred is determined by the settings of theassociated switches and MLB thresholds. If the switches for both of them are turned on, the twotypes of MLB can coexist. It is recommended that the threshold for inter-frequency loadbalancing be set to a smaller value than the threshold for inter-RAT load sharing so that inter-frequency load balancing takes precedence over inter-RAT load sharing. Load balancing maybe triggered by an overload in the uplink or downlink. For details about how to configure MLB,see 7 Engineering Guidelines.The MLB procedure consists of the following steps:1. Load measurement and evaluation

The eNodeB periodically measures the resources occupied by the uplink and downlinkGBR services and non-GBR services. Based on these measurement results, the eNodeBevaluates the cell load.

2. Load information exchange (only applicable to inter-frequency load balancing)If an MLB switch is turned on for a cell, the cell initiates a resource status request towardsits neighboring cells when the uplink and downlink loads of the cell meet the MLBtriggering condition. In this scenario, the cell exchanges the load information with itsneighboring cells.

3. MLB decisionl For inter-frequency load balancing, the eNodeB selects the best candidate cell as the

target cell. The selection is based on the load difference between the serving cell andthe candidate cells and the historical statistics on the performance of handovers fromthe serving cell to the candidate cells.

l The eNodeB determines whether to perform load sharing with UTRAN or GERANbased on the MLB switch settings on the eNodeB. If the switches for load sharing withUTRAN and GERAN are turned on, the eNodeB may select UEs for load sharing toUTRAN or GERAN neighboring cells.

4. MLB executionAfter the target cell for MLB is determined, the serving cell selects several UEs to transfer.The transfer method may be handover or cell reselection. If UEs do not support inter-RAThandover, the serving cell transfers UEs using redirections.

5. Performance monitoring and adjustment



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After executing MLB, the eNodeB monitors the performance of the source and target cells.The performance serves as a basis for the next selection of a target cell for MLB.



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3 Inter-Frequency Load BalancingThis chapter describes the optional feature LOFD-001032 Intra-LTE Load Balancing.Inter-frequency load balancing transfers some UEs in connected mode to balance load betweeninter-frequency neighboring cells. This feature applies to inter-frequency cells with the samecoverage or with a large proportion of overlapping coverage. Therefore, inter-frequency loadbalancing takes into consideration all the UEs in connected mode in a cell.Inter-frequency load balancing is enabled if the InterFreqMlbSwitch(InterFreqMlbSwitch)option of the CellAlgoSwitch.MlbAlgoSwitch parameter is selected.The following sections describe the procedure for inter-frequency load balancing.

eRANMLB Feature Parameter Description 3 Inter-Frequency Load Balancing


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3.1 Load Measurement and EvaluationThe eNodeB periodically measures cell resources in use and compares the result with thespecified MLB threshold.Load information exchange is triggered for inter-frequency load balancing if the air interfaceload of a cell is consistently equal to or greater than the sum of CellMLB.InterFreqMlbThd(the threshold above which inter-frequency load balancing is started) andCellMLB.LoadOffset.Load balancing is preferentially triggered by GBR services, then by total services. If the PRBusage of GBR services is greater than the specified threshold, load balancing is triggered byGBR services. If the PRB usage of GBR services is less than the specified threshold but the PRBusage of total services is greater than the specified threshold, load balancing is triggered by totalservices. Services that trigger load balancing are treated separately in the uplink and downlink.Load offset is used to prevent load fluctuations from frequently triggering and stopping loadbalancing.Load information exchange is stopped if the PRB usage of the serving cell is consistently lessthan the value of CellMLB.InterFreqMlbThd .

3.2 Load Information ExchangeIf the cell has at least one inter-frequency neighboring cell under the same eNodeB, the eNodeBwill perform inter-frequency load balancing only to these intra-eNodeB inter-frequencyneighboring cells. The serving cell can acquire the load status of these cells directly (not throughthe X2 interface) before making a load balancing decision.If the cell does not have any inter-frequency neighboring cells under the same eNodeB, theserving cell initiates a resource status request towards the neighboring cells on a specified listto exchange load information. The load information consists of the air interface, hardware, andtransport network layer loads. The air interface load is represented by the total PRB usage, PRBusage of GBR services, and PRB usage of non-GBR services in the uplink or downlink in eachcell.

NOTE

Inter-eNodeB cells exchange load information through the X2 interface. If the X2 interface is notconfigured, load information cannot be exchanged between the cells, and therefore the subsequent activitiesare not performed.

3.2.1 Neighboring Cell SelectionAll inter-frequency neighboring cells can be candidate cells. After filtering out certain cells, theeNodeB generates a list of neighboring cells for load information exchange. The following areexamples of cells that the eNodeB filters out:l Cells under a neighboring eNodeB to which the local eNodeB is not connected through an

X2 interfacel Cells with a handover success rate less than 98%



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l Cells for which the EutranInterFreqNCell.NoHoFlag parameter is set toFORBID_HO_ENUM(Forbid Ho)

3.2.2 Inter-eNodeB Cell Load Information ExchangeAfter determining the inter-eNodeB cells with which the serving cell can exchange loadinformation, the eNodeB sends a RESOURCE STATUS REQUEST message to all the eNodeBsto which the inter-eNodeB cells belong. The message contains the IDs of the inter-eNodeB cellswhose load information is requested and the interval at which the cell load information shouldbe reported. For details, see section 8.3.6 in 3GPP TS 36.423 V10.5.0 (2012-03).The serving cell requests all candidate cells to report their load information. If the serving cellreceives a RESOURCE STATUS RESPONSE message from a neighboring cell, the serving cellwill periodically receive subsequent RESOURCE STATUS UPDATE messages from thatneighboring cell. If the serving cell receives a RESOURCE STATUS FAILURE message froma neighboring cell, the neighboring cell is not considered a qualified candidate for load balancingat present.

NOTE

If a neighboring cell stops reporting RESOURCE STATUS UPDATE messages after several reports, thecell is not considered as a candidate cell at present.

3.3 Load Balancing DecisionThe eNodeB generates a target cell list for inter-frequency load balancing based on the loaddifferences between the cells, handover performance, and the load information exchange results.After load information exchange, the eNodeB derives a preliminary candidate cell list based onfactors such as cell bandwidth differences and the uplink or downlink resources occupied byGBR and total services. Then, the eNodeB generates a target cell list by removing theneighboring cells that meet any of the following conditions:l The success rate of handovers from the serving cell to the neighboring cell is less than 98%.l The TNL load or hardware load of the neighboring cell is in the HighLoad or Overload

state.l Between the neighboring and serving cells, services in the uplink or downlink that trigger

load balancing is less than the value of CellMLB.LoadDiffThd.If the target cell list is empty, the eNodeB stops load balancing for the serving cell.

NOTE

In RAN sharing scenarios, a neighboring cell can be the target cell regardless of whether the cell operatesin RAN sharing with common carriers mode or in RAN sharing with dedicated carriers mode.It is recommended that the CellMLB.InterFreqMlbThd parameter be set to the same value throughout thenetwork.The target cell may be so heavily loaded that load balancing from the target cell to other cells is alsotriggered in the same direction (uplink or downlink) as load balancing from the source cell. In this situation,load balancing from the source cell to the target cell is still performed as long as the target cell meets theload balancing condition.



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3.4 Load Balancing ExecutionInter-frequency load balancing involves only UEs in connected mode. The eNodeB selects someUEs that do not support carrier aggregation (called non-CA UEs) based on the frequencyinformation about the target cells, frequency capabilities of UEs, PRB usage in the target cells,and type of services that trigger load balancing in the serving cell. Then, the eNodeB instructsthe UEs to transfer to the target cells. If load balancing is triggered by GBR services, the eNodeBselects the UEs that are performing GBR services. If the load balancing is triggered by totalservices, the eNodeB selects UEs that are performing non-GBR services.In addition, the eNodeB considers both the uplink and downlink PRB usages of UEs during UEselection for load balancing. That is, the uplink and downlink PRB usages of the UEs that areselected by the eNodeB must meet certain conditions. This prevents ping-pong load balancingin the transmission direction opposite to the MLB-triggering direction after the UEs aretransferred to the neighboring cell. If uplink or downlink PRB usage of the selected UEs is toolarge, load balancing is likely to be triggered in the uplink or downlink of the target cell. If theuplink or downlink PRB usage of the selected UEs is too small, the load of the source cell maynot be reduced in time.For example, if load balancing is triggered by GBR services in the downlink, the eNodeB selectsthe UEs that meet the following conditions for load balancing:l The PRB usage of downlink GBR services is greater than 2% and less than or equal to half

of the value of the CellMLB.LoadDiffThd parameter.l The PRB usage of uplink GBR services is less than or equal to 2%.This prevents load balancing triggered by GBR services in the uplink after the UEs are transferredto the neighboring cell.In inter-frequency load balancing, there are two methods to transfer UEs that support inter-frequency handover: blind handover and measurement-based handover. Measurement-basedhandovers work by default, and in this case it is required that the RSRP of target inter-frequencycells must be greater than the value of theInterFreqHoGroup.InterFreqLoadBasedHoA4ThdRsrp parameter. Blind handovers workonly if the InterFreqMlbBlindHo(InterFreqMlbBlindHo) option of theCellAlgoSwitch.MlbHoMode parameter is selected.

NOTE

The total number of RBs in a cell used by the UEs to be transferred within an inter-frequency load balancingprocess cannot exceed the maximum number, which is calculated based on the PRB usage differencebetween the source and target cells and the CellMLB.LoadTransferFactor parameter. A greater PRBusage difference or a larger value of the CellMLB.LoadTransferFactor parameter produces a larger totalnumber of RBs in a cell used by the UEs to be transferred within an inter-frequency load balancing process.A UE is considered as a CA UE regardless of whether the UE is in its secondary serving cell (SCell) orprimary serving cell (PCell).

During inter-frequency load balancing, the serving cell rejects incoming handover requests withthe cause value "Resource optimisation handover".

NOTE

For definitions of the cause values for handover requests, see section 9.2.1.3 in 3GPP TS 36.413 V10.6.0(2012-06) and section 9.2.6 in 3GPP TS 36.423 V11.1.0 (2012-06).



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Based on the measurement results reported by the UEs, the eNodeB performs inter-frequencyhandovers for UEs that meet the handover conditions. For details about inter-frequencyhandovers, see Mobility Management in Connected Mode Feature Parameter Description.

NOTE

The EPC sends an SPID to the eNodeB when a UE accesses the network. The subscriber profile identifiedby the SPID includes the mobility and service usage information to which the UE subscribes. The operators'network plan determines subscriber profiles. For details about SPIDs, see section 8.6.2.2 in 3GPP TS 36.413V10.6.0 (2012-06) and section 16.1.8 and Annex I in 3GPP TS 36.300 V11.2.0 (2012-06).The UE will be transferred only to the RATs or frequencies specified in the SPID configuration if thefollowing conditions are met:l The UE is to be transferred and the eNodeB has learned the UE's SPID from the EPC.l The SpidCfg MO corresponding to this SPID has been configured on the eNodeB with the

SpidCfg.InterFreqMlbSwitch parameter set to TRUE(TRUE).

3.5 Performance MonitoringSelf-organizing network (SON) logs record the following information during a load balancingperiod:l Total number of UEs that are handed over to target cells and UEs whose RRC connections

are reestablished with the target cells because of radio link failures during handoversl Total PRB usageOperators can query the SON logs for the statistics on load balancing within each period.The eNodeB monitors the success rate of handovers from the source cell. In the next round ofload measurement and evaluation, the handover success rate is considered as an evaluationstandard for selecting target cells for inter-frequency load balancing.



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4 Inter-RAT Load SharingThis chapter describes the optional features LOFD-001044 Inter-RAT Load Sharing toUTRAN and LOFD-001045 Inter-RAT Load Sharing to GERAN.The decision on inter-RAT load sharing is based on the load of an E-UTRAN cell. If an E-UTRAN cell becomes heavily loaded, the eNodeB can trigger inter-RAT load sharing based onUE capabilities, load statistics of the target inter-RAT network, and system performance. Aftertriggering inter-RAT load sharing, the eNodeB takes one or both of the following actions:l Transfers some UEs in connected mode to the target cell.l Instructs some UEs to camp on the target cell after their Radio Resource Control (RRC)

connections are released (when the UEs enter idle mode).The following sections describe the inter-RAT load sharing procedure.

eRANMLB Feature Parameter Description 4 Inter-RAT Load Sharing


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4.1 Load Measurement and EvaluationThe eNodeB periodically measures cell resources in use and compares the result with thespecified MLB threshold.Inter-RAT load sharing is triggered if both the following conditions are met:l The cell load is consistently greater than or equal to the sum of

CellMLB.InterRatMlbThd and CellMLB.LoadOffset.l The number of uplink synchronized UEs in the cell is greater than or equal to

CellMLB.InterRatMlbUeNumThd.The same rules that determine the service type for triggering inter-frequency load balancing(described in 3.1 Load Measurement and Evaluation) apply to inter-RAT load sharing.Inter-RAT load sharing is stopped if the load of the serving cell is consistently less than the valueof CellMLB.InterRatMlbThd or the number of uplink synchronized UEs in the serving cell isconsistently less than the value of CellMLB.InterRatMlbUeNumThd.

4.2 Load Sharing DecisionIn inter-RAT load sharing, the eNodeB selects the target RAT based on the MLB switch settingsin the CellAlgoSwitch.MlbAlgoSwitch parameter.l If the UtranMlbSwitch(UtranMlbSwitch) option of the

CellAlgoSwitch.MlbAlgoSwitch parameter and the UtranPsHoSwitch(UtranPsHoSwitch) option of the EnodebAlgoSwitch.HoModeSwitch parameter areselected, the eNodeB will select UEs in connected mode for load sharing to UTRAN cells.

l If the UtranIdleMlbSwitch(UtranIdleMlbSwitch) option of theCellAlgoSwitch.MlbAlgoSwitch parameter is selected, the eNodeB will select UEs in idlemode for load sharing to UTRAN cells.

l If the GeranMlbSwitch(GeranMlbSwitch) option of theCellAlgoSwitch.MlbAlgoSwitch parameter and the GeranPsHoSwitch(GeranPsHoSwitch) option of the EnodebAlgoSwitch.HoModeSwitch parameter areselected, the eNodeB will select UEs for load sharing to GERAN cells.

If the switches for load sharing with UTRAN and GERAN are turned on, the eNodeB may selectUEs for load sharing to UTRAN or GERAN neighboring cells.

4.3 Load Sharing ExecutionDuring inter-RAT load sharing, the serving cell rejects incoming handover requests with thecause value "Resource optimisation handover".

NOTE

For definitions of the cause values for handover requests, see section 9.2.1.3 in 3GPP TS 36.413 V10.6.0(2012-06) and section 9.2.6 in 3GPP TS 36.423 V11.1.0 (2012-06).

The following sections describe the principles of transferring UEs in connected mode and idlemode.



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4.3.1 Transferring UEs in Connected ModeThe eNodeB instructs a number of UEs to perform inter-RAT measurements based on theinformation about the target cells, frequencies and RAT capabilities of UEs, PRB usage in thesource cell, and the type of services that trigger load sharing, when either of the following optioncombination is selected:l UtranMlbSwitch(UtranMlbSwitch) of the CellAlgoSwitch.MlbAlgoSwitch parameter

and UtranPsHoSwitch(UtranPsHoSwitch) of the EnodebAlgoSwitch.HoModeSwitchparameter

l GeranMlbSwitch(GeranMlbSwitch) of the CellAlgoSwitch.MlbAlgoSwitch parameterand GeranPsHoSwitch(GeranPsHoSwitch) of the EnodebAlgoSwitch.HoModeSwitchparameter

If load sharing is triggered by GBR services, the eNodeB selects UEs that are performing GBRservices and sends Measurement Configuration messages to these UEs. Alternatively, if loadsharing is triggered by total services, the eNodeB selects UEs that are performing non-GBRservices and sends Measurement Configuration messages to those UEs.In addition, the eNodeB considers both the uplink and downlink PRB usages of UEs during UEselection for load sharing. That is, the uplink and downlink PRB usages of the UEs that areselected by the eNodeB must meet certain conditions. This prevents ping-pong load sharing inthe transmission direction opposite to the MLB-triggering direction after the UEs are transferredto the neighboring cell. If uplink or downlink PRB usage of the selected UEs is too large, loadsharing is likely to be triggered in the uplink or downlink of the target cell. If the uplink ordownlink PRB usage of the selected UEs is too small, the load of the source cell may not bereduced in time.For example, if load sharing is triggered by GBR services in the downlink, the eNodeB selectsthe UEs that meet the following conditions for load sharing:l The PRB usage of downlink GBR services is greater than 2% and less than or equal to half

of the value of the CellMLB.LoadDiffThd parameter.l The PRB usage of uplink GBR services is less than or equal to 2%.This prevents load sharing triggered by GBR services in the uplink after the UEs are transferredto the neighboring cell.Based on the measurement results reported by the UEs, the eNodeB determines the target UEsfor load sharing. The E-UTRAN cell transfers the selected UEs to the target cell for inter-RATload sharing based on inter-RAT handover policies.In inter-RAT load sharing, there are two methods to transfer UEs that support inter-RAThandover: blind handover and measurement-based handover. Measurement-based handoverswork by default, and in this case it is required that the received signal code power (RSCP) oftarget UTRAN cells for load sharing must be greater than the value of theInterRatHoUtranGroup.LdSvBasedHoUtranB1ThdEcn0 parameter or the received signalstrength indicator (RSSI) of target GERAN cells for load sharing must be greater than the valueof the InterRatHoGeranGroup.LdSvBasedHoGeranB1Thd parameter. Blind handovers workonly if the InterRatMlbBlindHo(InterRatMlbBlindHo) option of theCellAlgoSwitch.MlbHoMode parameter is selected. If UEs do not support inter-RAT handover,the eNodeB transfers UEs by blind redirections.Handover is the preferred method for the eNodeB to perform load sharing, because the use ofredirection interrupts services. The eNodeB performs load sharing only if handover is enabled.



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If handover is enabled but the UEs do not support handover, the eNodeB performs redirectionsfor load sharing.For details about the description of inter-RAT handover, see Mobility Management in ConnectedMode Feature Parameter Description.

NOTE

The EPC sends an SPID to the eNodeB when a UE accesses the network. The subscriber profile identifiedby the SPID includes the mobility and service usage information to which the UE subscribes. The operators'network plan determines subscriber profiles. For details about SPIDs, see section 8.6.2.2 in 3GPP TS 36.413V10.6.0 (2012-06) and section 16.1.8 and Annex I in 3GPP TS 36.300 V11.2.0 (2012-06).The UE will be transferred only to the RATs or frequencies specified in the SPID configuration if thefollowing conditions are met:l The UE is to be transferred and the eNodeB has learned the UE's SPID from the EPC.l The SpidCfg MO corresponding to this SPID has been configured on the eNodeB with the

SpidCfg.InterRatMlbSwitch parameter set to TRUE(TRUE).

4.3.2 Transferring UEs in Idle ModeIf the UtranIdleMlbSwitch(UtranIdleMlbSwitch) option of theCellAlgoSwitch.MlbAlgoSwitch parameter is selected for an E-UTRAN cell and the E-UTRANcell meets the conditions for triggering inter-RAT load sharing, the eNodeB instructs severalUEs that are undergoing RRC connection release procedures to camp on the target UTRAN cellafter their RRC connections are released. The eNodeB delivers the instructions by including theCellReselectionPriority IE in the RRCConnectionRelease messages to the UEs.The actual duration of load sharing with UTRAN is calculated based on the value of theCellMLB.InitValidPeriod parameter and the number of uplink synchronized UEs. TheCellMLB.InitValidPeriod parameter specifies the initial duration of load sharing with UTRANfor UEs in idle mode, and the actual duration increases with the number of uplink synchronizedUEs. Therefore, the larger the value of the CellMLB.InitValidPeriod parameter or the numberof uplink synchronized UEs, the larger the actual duration of load sharing with UTRAN. Withinthe time of actual duration, UEs preferentially camp on neighboring UTRAN cells if the UEsare to be released after the inactive timer expires.Load sharing with UTRAN for UEs in idle mode takes effect only if the priorities of the servingfrequency and the neighboring E-UTRAN frequencies of the serving cell are all higher than orall lower than those of the neighboring UTRAN frequencies of the serving cell.

4.4 Performance MonitoringSON logs record the following information during a load sharing period:l Number of UEs that are handed over to target cellsl Number of UEs whose RRC connections are reestablished with the target cells because of

radio link failures during handoversl Total PRB usageOperators can query the SON logs for the statistics on load sharing within each period.



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5 Related Features5.1 Features Related to LOFD-001032 Intra-LTE LoadBalancingPrerequisite Features

None

Mutually Exclusive FeaturesNone

Impacted FeaturesNone

5.2 Features Related to LOFD-001044 Inter-RAT LoadSharing to UTRANPrerequisite Features

The Inter-RAT Load Sharing to UTRAN feature depends on LOFD-001019 PS Inter-RATMobility between E-UTRAN and UTRAN.



eRANMLB Feature Parameter Description 5 Related Features


17

5.3 Features Related to LOFD-001045 Inter-RAT LoadSharing to GERANPrerequisite Features

The Inter-RAT Load Sharing to GERAN feature depends on LOFD-001020 PS Inter-RATMobility between E-UTRAN and GERAN.



eRANMLB Feature Parameter Description 5 Related Features


18

6 Network Impact6.1 LOFD-001032 Intra-LTE Load BalancingSystem Capacity

The Intra-LTE Load Sharing feature transfers some load from an E-UTRAN cell to intra-RATneighboring cells before the source E-UTRAN cell becomes congested, and, therefore, increasesresource usage and system capacity.

Network PerformanceThe Intra-LTE Load Balancing feature increases the number of intra-LTE handovers.

6.2 LOFD-001044 Inter-RAT Load Sharing to UTRANSystem Capacity

The Inter-RAT Load Sharing to UTRAN feature transfers some load from an E-UTRAN cell toneighboring UTRAN cells before the source E-UTRAN cell becomes congested, and, therefore,decreases the E-UTRAN load and improves the user experience of UEs in E-UTRAN. However,this feature increases the UTRAN load and negatively affects the user experience of UEs inUTRAN.

Network PerformanceThe Inter-RAT Load Sharing to UTRAN feature increases the number of inter-RAT handoversfrom E-UTRAN to UTRAN and the value of the L.RRC.ConnReq.Att.MoSig counter in thesource cell.

eRANMLB Feature Parameter Description 6 Network Impact


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6.3 LOFD-001045 Inter-RAT Load Sharing to GERANSystem Capacity

The Inter-RAT Load Sharing to GERAN feature transfers some load from an E-UTRAN cell toneighboring GERAN cells before the source E-UTRAN cell becomes congested, and, therefore,decreases the E-UTRAN load and improves the user experience of UEs in E-UTRAN. However,this feature increases the GERAN load and negatively affects the user experience of UEs inGERAN.

Network PerformanceThe Inter-RAT Load Sharing to GERAN feature increases the number of inter-RAT handoversfrom E-UTRAN to GERAN and the value of the L.RRC.ConnReq.Att.MoSig counter in thesource cell.

eRANMLB Feature Parameter Description 6 Network Impact


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7 Engineering Guidelines7.1 When to Use MLB

Use inter-frequency load balancing when one of the following conditions is met:l Inter-frequency cells provide the same coverage.l Inter-frequency cells have a large proportion of overlapping coverage.l The coverage of a cell contains that of another inter-frequency cell.Use inter-RAT load sharing if multi-mode base stations are used or base stations of differentRATs provide contiguous coverage.

7.2 Required InformationCollect the following information:l Information about each neighboring cell of the cells under the local eNodeB

Whether information about the neighboring cell is complete Whether the neighboring cell has been blacklisted Whether the No Handover attribute is set to prohibit handovers to the neighboring cell

l Status of the X2 interfaces with neighboring eNodeBsl UE capabilities

The proportion of UEs that support inter-frequency or inter-RAT measurements

7.3 Planning7.3.1 RF Planning

MLB is implemented by handover and reselection. Therefore, the current network coverage mustmeet the following UE mobility requirements:

eRANMLB Feature Parameter Description 7 Engineering Guidelines


21

l No holes exist in the coverage.l Overshoot coverage is minimized.l Pilot pollution is minimized. Pilot pollution occurs if the preambles used by different cells

under one eNodeB conflict.l Uplink and downlink imbalances are minimized.

7.3.2 Network PlanningN/A

7.3.3 Hardware PlanningN/A

7.4 Deployment

7.4.1 RequirementsThere are no requirements for the operating system and transmission networking. Beforedeploying MLB, the operator must purchase and activate the licenses for the features listed inTable 7-1.

Table 7-1 License information for MLBFeature ID Feature Name License

Control ItemName

NE Sales Unit

LOFD-001032 Intra-LTE LoadBalancing

Intra-LTE LoadBalancing

eNodeB per RRCConnected User

LOFD-001044 Inter-RAT LoadSharing toUTRAN

Inter-RAT LoadSharing toUTRAN


LOFD-001045 Inter-RAT LoadSharing toGERAN

Inter-RAT LoadSharing toGERAN


7.4.2 Data PreparationThis section describes the data that you need to collect for setting parameters. Required data isdata that you must collect for all scenarios. Collect scenario-specific data when necessary for aspecific feature deployment scenario.There are three types of data sources:



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l Network plan (negotiation required): parameter values planned by the operator andnegotiated with the EPC or peer transmission equipment

l Network plan (negotiation not required): parameter values planned and set by the operatorl User-defined: parameter values set by users

Required DataThe following table describes the parameters that must be set in the CellMLB managed object(MO) to configure MLB algorithms.

ParameterName

Parameter ID Data Source Setting Notes

Load Offset CellMLB.LoadOffset

Network plan(negotiation notrequired)

This parameter specifies anoffset applied to the thresholdvalue for triggering MLB. MLBis triggered only when the loadis consistently equal to orgreater than the sum of thethreshold and offset values.This mechanism helps preventload fluctuations fromfrequently triggering andstopping MLB.The recommended value is 8.

LoadDifferenceThreshold

CellMLB.LoadDiffThd


This parameter specifies theminimum load differencebetween two cells that triggersMLB. When the load differencebetween two cells exceeds thevalue of this parameter, theeNodeB regards the load asimbalanced and triggers MLBbetween the two cells. When theload difference between thesecells drops below this threshold,the eNodeB no longer regardsthe load as imbalanced andstops MLB between the cells.This parameter also specifiesthe maximum PRB usage ofUEs selected for inter-RAT loadsharing. The recommendedvalue is 15.

The following table describes the parameter that must be set in the InterFreqHoGroup MO toconfigure inter-frequency handover.



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ParameterName


Load BasedInterfreq RSRPthreshold

InterFreqHoGroup.InterFreqLoadBasedHoA4ThdRsrp


This parameter specifies theRSRP threshold for event A4related to load-based inter-frequency handover. When themeasured RSRP value exceedsthis threshold, event A4 isreported.The default value is -103.

The following table describes the parameter that must be set in the InterRatHoUtranGroupMO to configure inter-RAT handover to UTRAN.

ParameterName


Load ServiceBased UTRANEventB1 RSCPtriggerthresholdd

InterRatHoU-tranGroup.LdSvBasedHoUtranB1ThdRscp


This parameter specifies theRSCP threshold for event B1related to load- or service-basedinter-RAT handover toUTRAN.In inter-RAT handover toUTRAN, this parameterspecifies the requirement forRSCP of the target UTRANcell.When the measured RSCPexceeds this threshold, ameasurement report will besent.The recommended value is-101.

The following table describes the parameters that must be set in the InterRatHoGeranGroupMO to configure inter-RAT handover to GERAN.



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ParameterName


Load ServiceBased GeranEventB1triggerthreshold

InterRatHoGeranGroup.LdSvBasedHoGeranB1Thd


This parameter specifies theRSSI threshold for event B1related to load- or service-basedinter-RAT handover toGERAN.When the measured RSSIexceeds this threshold, eventB1 will be reported.The recommended value is-98.

Scenario-specific DataScenario 1: Inter-Frequency Load BalancingThe following table describes the parameters that must be set in the CellAlgoSwitch MO toenable the inter-frequency load balancing algorithm.

Parameter Name Parameter ID Data Source Setting NotesLocal cell ID CellAlgoSwitch.

LocalCellIdNetwork plan(negotiation notrequired)

This parameterspecifies the local IDof a cell. It uniquelyidentifies the cellwithin an eNodeB.The actual valuerange is 0 to 17.



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Parameter Name Parameter ID Data Source Setting NotesLoad balancingalgorithm switch

CellAlgoSwitch.MlbAlgoSwitch


TheInterFreqMlbS-witch(InterFreqMlbS-witch) check boxunder this parameterspecifies whether toenable the inter-frequency loadbalancing algorithm.l If

InterFreqMlbS-witch(InterFreqMlbSwitch) isselected, thealgorithm isenabled.

l IfInterFreqMlbS-witch(InterFreqMlbSwitch) is notselected, thealgorithm isdisabled.

The following table describes the parameters that must be set in the CellMLB MO to configurethe inter-frequency load balancing algorithm.

ParameterName

ParameterID

Data Source Setting Notes

Local cell ID CellMLB.LocalCellId


This parameter specifies the localID of a cell. It uniquely identifiesthe cell within an eNodeB.The actual value range is 0 to 17.



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ParameterName

ParameterID

Data Source Setting Notes

Inter-FrequencyMobility LoadBalancingThreshold

CellMLB.InterFreqMlbThd


This parameter specifies thethreshold for inter-frequency loadbalancing. Inter-frequency loadbalancing is started when the loadexceeds the sum of this thresholdand the load offset. Inter-frequency load balancing isstopped when the load dropsbelow this threshold.The default value is 60.It is recommended that thisparameter be set to the same valuethroughout the network.

Load TransferFactor

CellMLB.LoadTransferFactor


This parameter specifies the factorused to control the amount of loadtransferred during a single MLBprocedure. The value of thisparameter has an impact on theefficiency of the MLB algorithmand the algorithm to prevent ping-pong load transfer.A larger value of this parameterleads to the situation where alarger amount of load can betransferred, and a smaller valueleads to the situation where asmaller amount of load can betransferred. The recommendedvalue is 0.

(Optional) The following table describes the parameters that must be set in SpidCfg MOs toconfigure SPIDs.

Parameter Name Parameter ID Data Source Setting NotesSpid SpidCfg.Spid Network plan

(negotiation notrequired)

This parameterspecifies an SPID.The actual valuerange is 1 to 256.



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Parameter Name Parameter ID Data Source Setting NotesRAT frequencypriority indication

SpidCfg.RatFreqPriorityInd


This parameterspecifies whether toconfigure afrequency prioritygroup.

RAT frequencypriority group ID

SpidCfg.RatFreqPriority-GroupId


This parameteruniquely identifies afrequency prioritygroup.The actual valuerange is 0 to 255.

InterFreq MlbSwitch

SpidCfg.InterFreqMlbS-witch


This parameterspecifies whether toallow inter-frequency loadbalancing for UEswith the SPID.l If the parameter is

set to TRUE(TRUE), inter-frequency loadbalancing isallowed for UEswith the SPID.

l If the parameter isset to FALSE(FALSE), inter-frequency loadbalancing is notallowed for UEswith the SPID.This parametertakes effect onlyfor UEs thatnewly access thenetwork.

Scenario 2: Inter-RAT Load SharingThe following table describes the parameters that must be set in the CellAlgoSwitch MO toenable the inter-RAT load sharing algorithm.



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Parameter Name Parameter ID

DataSource

Setting Notes

Local cell ID CellAlgoSwitch.LocalCellId

Networkplan(negotiation notrequired)

This parameter specifies the local ID of acell. It uniquely identifies the cell within aneNodeB.The actual value range is 0 to 17.

Load balancingalgorithm switch

CellAlgoSwitch.MlbAlgoSwitch


The UtranMlbSwitch(UtranMlbSwitch)check box under this parameter specifieswhether to enable load sharing withUTRAN for UEs in connected mode.l If UtranMlbSwitch

(UtranMlbSwitch) is selected, thealgorithm is enabled.

l If UtranMlbSwitch(UtranMlbSwitch) is not selected, thealgorithm is disabled.

The UtranIdleMlbSwitch(UtranIdleMLBSwitch) check box underthis parameter specifies whether to enableload sharing with UTRAN for UEs in idlemode.l If UtranIdleMlbSwitch

(UtranIdleMLBSwitch) is selected,the algorithm is enabled.

l If UtranIdleMlbSwitch(UtranIdleMLBSwitch) is notselected, the algorithm is disabled.

The GeranMlbSwitch(GeranMlbSwitch) check box under thisparameter specifies whether to enable loadsharing with GERAN.l If GeranMlbSwitch

(GeranMlbSwitch) is selected, thealgorithm is enabled.

l If GeranMlbSwitch(GeranMlbSwitch) is not selected, thealgorithm is disabled.

The following table describes the parameters that must be set in the ENodeBAlgoSwitch MOto configure the inter-RAT load sharing policy.



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ParameterName

Parameter ID DataSource

Setting Notes

Handover Modeswitch

ENodeBAlgoSwitch.HoModeSwitch

Networkplan(negotiationnotrequired)

If the UtranPsHoSwitch(UtranPsHoSwitch) or GeranPsHoSwitch(GeranPsHoSwitch) check box is selected,the eNodeB performs inter-RAT load sharingusing handovers. If neither of them is notselected, the eNodeB cannot perform inter-RAT load sharing using handovers and MLBis not allowed.

The following table describes the parameters that must be set in the CellMLB MO to configurethe inter-RAT load sharing algorithm.

ParameterName


Setting Notes

Localcell ID

CellMLB.LocalCellId Networkplan(negotiation notrequired)

This parameter specifies the local ID of acell. It uniquely identifies the cell within aneNodeB.The actual value range is 0 to 17.

Inter-RATMobility LoadBalancingThreshold

CellMLB.InterRatMlbThd


This parameter specifies the threshold forinter-RAT load sharing. Inter-RAT loadsharing is triggered if the cell load isconsistently greater than or equal to thesum of CellMLB.InterRatMlbThd andCellMLB.LoadOffset and if the number ofuplink synchronized UEs in the cell isgreater than or equal toCellMLB.InterRatMlbUeNumThd. Inter-RAT load sharing is stopped if the cell loadis consistently less thanCellMLB.InterRatMlbThd or the numberof uplink synchronized UEs in the cell fallsbelow CellMLB.InterRatMlbUe-NumThd.The default value is 75.



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ParameterName


Setting Notes

UTRAN IdleModeMobility LoadBalancingInitialValidPeriod

CellMLB.InitValidPeriod


This parameter specifies the initial durationfor load sharing with UTRAN for UEs inidle mode.A larger value of this parameter leads to thesituation where more UEs in idle mode aretransferred to UTRAN after the E-UTRANcell is over loaded. The recommendedvalue is 10.

Inter-RATMobility LoadBalancingThreshold ofUEnumber

CellMLB.InterRatMlbUe-NumThd


This parameter specifies the threshold forthe number of uplink synchronized UEsused to trigger or stop inter-RAT loadsharing.The actual number of uplink synchronizedUEs is equal to this threshold multiplied by1000.

The following table describes the parameters that must be set in SpidCfg MOs to configureSPIDs.

Parameter Name Parameter ID Data Source Setting NotesSpid SpidCfg.Spid Network plan

(negotiation notrequired)

This parameterspecifies an SPID.The actual valuerange is 1 to 256.

RAT frequencypriority indication

SpidCfg.RatFreqPriorityInd


This parameterspecifies whether toconfigure afrequency prioritygroup.

RAT frequencypriority group ID

SpidCfg.RatFreqPriority-GroupId


This parameteruniquely identifies afrequency prioritygroup.The actual valuerange is 0 to 255.



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Parameter Name Parameter ID Data Source Setting NotesInterRat Mlb Switch SpidCfg.

InterRatMlbSwitchNetwork plan(negotiation notrequired)

This parameterspecifies whether toallow inter-RAT loadsharing for UEs withthe SPID.l If the parameter is

set to TRUE(TRUE), inter-RAT load sharingis allowed forUEs with theSPID.

l If the parameter isset to FALSE(FALSE), inter-RAT load sharingis not allowed forUEs with theSPID.This parametertakes effect onlyfor UEs thatnewly access thenetwork.

7.4.3 PrecautionsPay attention to the following when deploying MLB in a live network:l If the switches for inter-frequency load balancing and inter-RAT load sharing are turned

on for a cell and the cell load meets the conditions for starting both types of MLB, theprobabilities of both types are the same because no priorities have been specified for thedifferent types of MLB.

l Inter-frequency load balancing is recommended in live networks.

7.4.4 ActivationUsing the CME to Perform Batch Configuration for Newly Deployed eNodeBs

Enter the values of the parameters listed in Table 7-2 in a summary data file, which also containsother data for the new eNodeBs to be deployed. Then, import the summary data file into theConfiguration Management Express (CME) for batch configuration. For detailed instructions,see section "Creating eNodeBs in Batches" in the initial configuration guide for the eNodeB.The summary data file may be a scenario-specific file provided by the CME or a customizedfile, depending on the following conditions:



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l The MOs in Table 7-2 are contained in a scenario-specific summary data file. In thissituation, set the parameters in the MOs, and then verify and save the file.

l Some MOs in Table 7-2 are not contained in a scenario-specific summary data file. In thissituation, customize a summary data file to include the MOs before you can set theparameters.

Table 7-2 Parameters for MLBMO Sheet in the

Summary DataFile

Parameter Group Remarks

CellAlgoSwitch

CELLALGOSWITCH

MlbAlgoSwitch This MO must becustomized in a list-typesheet of the template.

CellMLB CELLMLB LocalCellId,InterFreqMlbThd,InterRatMlbThd,LoadExchangePeriod,LoadOffset,LoadDiffThd,InterRatMlbUe-NumThd,InitValidPeriod,LoadTransferFactor

This MO must becustomized in a list-typesheet of the template.

ENodeBAlgoSwitch

ENODEBALGOSWITCH

HoModeSwitch This MO must becustomized in a list-typesheet of the template.

SpidCfg(Optional)

SPIDCFG Spid, InterFreqMlbS-witch, InterRatMlbS-witch


CellShutDown(Optional)

CELLSHUTDOWN

LocalCellId,CellShutdownSwitch,StartTime, StopTime,DlPrbThd,DlPrbOffset,UlPrbThd,UlPrbOffset


Using the CME to Perform Batch Configuration for Existing eNodeBsBatch reconfiguration using the CME is the recommended method to activate a feature onexisting eNodeBs. This method reconfigures all data, except neighbor relationships, for multipleeNodeBs in a single procedure. The procedure is as follows:

Step 1 Choose CME > Advanced > Customize Summary Data File (M2000 client mode), or chooseAdvanced > Customize Summary Data File (M2000 client mode), to customize a summarydata file for batch reconfiguration.



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NOTE

For context-sensitive help on a current task in the client, press F1.

Step 2 Choose CME > LTE Application > Export Data > Export Base Station Bulk ConfigurationData (M2000 client mode), or choose LTE Application > Export Data > Export Base StationBulk Configuration Data (CME client mode), to export the eNodeB data stored on the CMEinto the customized summary data file.

Step 3 In the summary data file, set the parameters in the MOs listed in Table 7-2 and close the file.Step 4 Choose CME > LTE Application > Import Data > Import Base Station Bulk Configuration

Data (M2000 client mode), or choose LTE Application > Import Data > Import Base StationBulk Configuration Data (CME client mode), to import the summary data file into the CME.

Step 5 Choose CME > Planned Area > Export Incremental Scripts (M2000 client mode), or chooseArea Management > Planned Area > Export Incremental Scripts (CME client mode), toexport and activate the incremental scripts.

----End

Using the CME to Perform Single ConfigurationOn the CME, set the parameters listed in the "Data Preparation" section for a single eNodeB.The procedure is as follows:

Step 1 In the planned data area, click Base Station in the upper left corner of the configuration window.Step 2 In area 1 shown in Figure 7-1, select the eNodeB to which the MOs belong.

Figure 7-1 MO search and configuration window

Step 3 On the Search tab page in area 2, enter an MO name, for example, CELL.



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Step 4 In area 3, double-click the MO in the Object Name column. All parameters in this MO aredisplayed in area 4.

Step 5 Set the parameters in area 4 or 5.Step 6 Choose CME > Planned Area > Export Incremental Scripts (M2000 client mode), or choose

Area Management > Planned Area > Export Incremental Scripts (CME client mode), toexport and activate the incremental scripts.----End

Using MML CommandsScenario 1: Inter-Frequency Load Balancing

Step 1 Run the MOD CELLMLB command to set the threshold for inter-frequency load balancing.Step 2 Run the MOD CELLALGOSWITCH command to enable the inter-frequency load balancing

algorithm.Step 3 (Optional) Run the ADD SPIDCFG command to set an SPID and enable SPID-specific inter-

frequency load balancing. If the SPID already exists, run the MOD SPIDCFG command tomodify the configuration as required.----EndScenario 2: Inter-RAT Load Sharing for UEs in Connected Mode

Step 1 Run the MOD ENODEBALGOSWITCH command with the UtranPsHoSwitch(UtranPsHoSwitch) or GeranPsHoSwitch(GeranPsHoSwitch) check box under theHandover Mode switch parameter selected.

Step 2 Run the MOD CELLMLB command to set the threshold for inter-RAT load sharing and thethreshold for the number of uplink synchronized UEs.

Step 3 Run the MOD CELLALGOSWITCH command to enable inter-RAT load sharing withUTRAN for UEs in connected mode or inter-RAT load sharing with GERAN.

Step 4 (Optional) Run the ADD SPIDCFG command to set an SPID and enable SPID-specific inter-RAT load sharing. If the SPID already exists, run the MOD SPIDCFG command to modify theconfiguration as required.----EndScenario 3: Inter-RAT Load Sharing for UEs in Idle Mode

Step 1 Run the MOD CELLMLB command to modify the threshold for inter-RAT load sharing, thethreshold for the number of uplink synchronized UEs, and the initial duration for load sharingwith UTRAN for UEs in idle mode.

Step 2 Run the MOD CELLALGOSWITCH command to enable inter-RAT load sharing withUTRAN for UEs in idle mode.----End

MML Command ExamplesScenario 1: Inter-Frequency Load Balancing



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MOD CELLMLB: LocalCellId=0, InterFreqMlbThd=60;MOD CELLALGOSWITCH: LocalCellId=0, MlbAlgoSwitch=InterFreqMlbSwitch-1;ADD SPIDCFG: Spid=1, RatFreqPriorityInd=NOT_CFG, InterFreqMlbSwitch=TRUE;

Scenario 2: Inter-RAT Load Sharing for UEs in Connected ModeMOD ENODEBALGOSWITCH: HoModeSwitch=UtranPsHoSwitch-1;MOD ENODEBALGOSWITCH: HoModeSwitch=GeranPsHoSwitch-1;MOD CELLMLB: LocalCellId=0, InterRatMlbThd=70, InterRatMlbUeNumThd=15;MOD CELLALGOSWITCH: LocalCellId=0, MlbAlgoSwitch=UtranMlbSwitch-1;MOD CELLALGOSWITCH: LocalCellId=0, MlbAlgoSwitch=GeranMlbSwitch-1;ADD SPIDCFG: Spid=1, RatFreqPriorityInd=NOT_CFG, InterRatMlbSwitch=TRUE;

Scenario 3: Inter-RAT Load Sharing for UEs in Idle ModeMOD CELLMLB: LocalCellId=0, InterRatMlbThd=70, InterRatMlbUeNumThd=15, InitValidPeriod=10;MOD CELLALGOSWITCH: LocalCellId=0, MlbAlgoSwitch=UtranIdleMlbSwitch-1;

7.4.5 Activation ObservationInter-Frequency Load Balancing

To verify whether inter-frequency load balancing works correctly, perform the following steps:Step 1 On the M2000 client, choose Monitor > Signaling Trace > Signaling Trace Management.

The Signaling Trace Management window is displayed, as shown in Figure 7-2.

Figure 7-2 Signaling Trace Management window

Step 2 Start RB usage monitoring.1. In the navigation tree on the left of the Signaling Trace Management window, double-

click Usage of RB Monitoring under LTE > Cell Performance Monitoring.The Usage of RB Monitoring dialog box is displayed, as shown in Figure 7-3.



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Figure 7-3 Usage of RB Monitoring dialog box

2. Set the task name, select the eNodeB site, and click Next.The Usage of RB Monitoring dialog box as shown in Figure 7-4 is displayed.

Figure 7-4 Usage of RB Monitoring dialog box



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3. Enter the local cell ID and then click Finish.The RB monitoring task starts for the cell, and the tracing result is displayed as shown inFigure 7-5.

Figure 7-5 RB usage tracing result

Step 3 Start MLB performance monitoring.1. In the navigation tree on the left of the Signaling Trace Management window, double-

click MLB Monitoring under LTE > Cell Performance Monitoring.The MLB Monitoring dialog box is displayed, as shown in Figure 7-6.

Figure 7-6 MLB Monitoring dialog box

2. Set the task name, select the eNodeB site, and click Next.3. Enter the information about a neighboring cell of the local cell to be traced, as shown in

Figure 7-7.



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Figure 7-7 Entering information about a neighboring cell

4. Click Finish.The MLB performance monitoring task starts for the local cell, and the monitoring resultis displayed as shown in Figure 7-8. The monitoring result includes the PRB usage of thecell, the PRB usage of the neighboring cell, and the type of load that triggers MLB in thelocal cell.

Figure 7-8 MLB performance monitoring result



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NOTE

For details about the types of load that trigger MLB, see the related performance monitoring reference.

Step 4 On the M2000 client, start Uu interface tracing.1. In the navigation tree on the left of the Signaling Trace Management window, double-

click Uu Interface Trace under LTE > Application Layer. The Uu Interface Tracedialog box is displayed as shown in Figure 7-9.

2. Set the task name, select the eNodeB site, and click Next. The Uu Interface Trace dialogbox as shown in Figure 7-10 is displayed.

Figure 7-9 Uu Interface Trace dialog box



40

Figure 7-10 Entering information about a Uu interface tracing task

3. Click Finish.The Uu interface tracing task starts for the cell, and the tracing result is displayed as shown inFigure 7-11.



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Figure 7-11 Uu interface tracing result

Step 5 Start X2 interface tracing in a similar way as Step 4, and check the messages traced over the X2interface.

NOTE

Load information can be traced on the X2 interface only in inter-eNodeB inter-frequency load balancing.No load information is exchanged over the X2 interface in intra-eNodeB inter-frequency load balancing.

If the serving cell receives a RESOURCE STATUS RESPONSE message from a neighboringcell after sending a RESOURCE STATUS REQUEST message to the neighboring cell, and laterperiodically receives RESOURCE STATUS UPDATE messages from the neighboring cell,inter-frequency load balancing has been activated. Figure 7-12 shows an example of theRESOURCE STATUS REQUEST message.

Figure 7-12 RESOURCE STATUS REQUEST message



42

NOTE

The RESOURCE STATUS REQUEST message contains the IDs (eUTRANcellIdentifier IE) of the cellswhose load information is requested and the interval (reportingPeriodicity IE) at which the cell loadinformation needs to be reported.

Step 6 Use UE1 to access the local cell in the cell center, and use UE2 to access the cell at a place whereUE2 can receive signals from an inter-frequency neighboring cell with RSRP greater thanInterFreqHoGroup.InterFreqLoadBasedHoA4ThdRsrp.

Step 7 (This step simulates downlink overload in a 10 MHz cell as an example.) Inject downlink UDPpackets for UE1 until the M2000 client shows that the RB usage exceeds the sum of Inter-Frequency Mobility Load Balancing Threshold and Load Offset. Inject downlink UDPpackets at a rate of 2 Mbit/s for at least 1 minute.

Step 8 Check for an RRC_CONN_RECFG message in the Uu interface tracing result and aHANDOVER_REQUEST message in the X2 interface tracing result.If the HANDOVER_REQUEST message containing the handover cause of "reduce-load-in-serving-cell" exists, inter-frequency load sharing is working correctly. For details about thesignaling procedure, see the description of a successful inter-frequency handover in MobilityManagement in Connected Mode Feature Parameter Description.----EndTo use SON logs to verify whether MLB takes effect, perform the following steps:

Step 1 On the M2000 client, choose SON > SON Log.Step 2 On the Query SON Log tab page, choose MLB Log from the Log Category drop down list in

the upper left corner, and click Inter-Frequency Handover Statistics under Event Name.Then, click Query to query SON logs. From the logs, check whether the feature is workingcorrectly.You can view only the SON logs that were generated at least one day ago.----End

Inter-RAT Load Sharing for UEs in Connected ModeTo verify whether inter-RAT load sharing for UEs in connected mode works correctly, performthe following steps:

Step 1 On the M2000 client, start Uu interface tracing, S1 interface tracing, and RB usage monitoring.For details about how to start these three tasks, see Inter-Frequency Load Balancing earlierin this section.

Step 2 Use UE1 to access a cell in the cell center, and use UE2 to access the cell at a place where UE2can receive signals from an inter-RAT neighboring cell with the radio signal greater than thetrigger thresholds for load- and service-based event B1. In addition, ensure that the number ofuplink synchronized UEs in the cell is greater than or equal to the Inter-RAT Mobility LoadBalancing UE Number Threshold value.

Step 3 (This step simulates downlink overload in a 10 MHz cell as an example.) Inject downlink UDPpackets for UE1 until the M2000 client shows that the RB usage exceeds the sum of Inter-RAT



43

Mobility Load Balancing Threshold and Load Offset. Inject downlink UDP packets for UE2at a rate of 2 Mbit/s.

Step 4 Check for an S1AP_HANDOVER_REQUIRED message in the S1 interface tracing result.If the S1AP_HANDOVER_REQUIRED message containing the cause value "reduce-load-in-serving-cell" exists, inter-RAT load sharing for UEs in connected mode is working correctly.----EndTo use SON logs to verify whether MLB takes effect, perform the following steps:

Step 1 On the M2000 client, choose SON > SON Log.Step 2 On the Query SON Log tab page, choose MLB Log from the Log Category drop down list in

the upper left corner, and click Inter-RAT Handover Statistics under Event Name. Then, clickQuery to query SON logs. From the logs, check whether the feature is working correctly.----End

Inter-RAT Load Sharing with UTRAN for UEs in Idle ModeTo verify whether inter-RAT load sharing for UEs in idle mode works correctly, perform thefollowing steps:

Step 1 On the M2000 client, start Uu interface tracing, S1 interface tracing, and RB usage monitoring.For details about how to start these three tasks, see Inter-Frequency Load Balancing earlierin this section.

Step 2 Use UE1 to access a cell in the cell center, and use UE2 to access the cell at a place where UE2can receive signals from an inter-RAT neighboring cell with a signal level higher than the cell-reselection threshold. In addition, ensure that the number of uplink synchronized UEs in the cellis greater than or equal to the Inter-RAT Mobility Load Balancing UE Number Thresholdvalue.

Step 3 (This step simulates downlink overload in a 10 MHz cell as an example.) Inject downlink UDPpackets for UE2 at a rate of 2 Mbit/s. Inject downlink UDP packets for UE1 until the M2000client shows that the RB usage exceeds the sum of Inter-RAT Mobility Load BalancingThreshold and Load Offset. Stop injecting downlink UDP packets for UE2. Wait until itsinactivity timer expires, so that UE2 enters idle mode. Check whether the RB usage exceeds thesum of Inter-RAT Mobility Load Balancing Threshold and Load Offset.If UE2 enters idle mode within the configured initial duration, the reselection priority containedin the RRC_CONN_REL message in the Uu interface tracing result meets the requirements, andUE2 is successfully transferred to the UTRAN cell, inter-RAT load sharing is working correctly.For details about the reselection priority, see 4.3.2 Transferring UEs in Idle Mode.----End

7.4.6 DeactivationUsing the CME to Perform Batch Configuration

Batch reconfiguration using the CME is the recommended method to deactivate a feature oneNodeBs. This method reconfigures all data, except neighbor relationships, for multiple



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eNodeBs in a single procedure. The procedure for feature deactivation is similar to that forfeature activation described in Using the CME to Perform Batch Configuration for ExistingeNodeBs. In the procedure, modify parameters according to Table 7-3.

Table 7-3 Parameters for MLBMO Sheet in the

Summary DataFile

ParameterGroup

Setting Notes

CELLALGOSWITCH

CELLALGOSWITCH

MlbAlgoSwitch

Turn off the related load balancingswitch.

Using the CME to Perform Single ConfigurationOn the CME, set parameters according to Table 7-3. For detailed instructions, see Using theCME to Perform Single Configuration described for feature activation.

Using MML CommandsScenario 1: Inter-Frequency Load BalancingRun the MOD CELLALGOSWITCH command to disable the inter-frequency load balancingalgorithm.Scenario 2: Inter-RAT Load SharingRun the MOD CELLALGOSWITCH command to disable inter-RAT load sharing withUTRAN for UEs in connected or idle mode or inter-RAT load sharing with GERAN.

MML Command ExamplesScenario 1: Inter-Frequency Load BalancingMOD CELLALGOSWITCH: LocalCellId=0, MlbAlgoSwitch=InterFreqMlbSwitch-0;

Scenario 2: Inter-RAT Load SharingMOD CELLALGOSWITCH: LocalCellId=0, MlbAlgoSwitch=UtranMlbSwitch-0;MOD CELLALGOSWITCH: LocalCellId=0, MlbAlgoSwitch=UtranIdleMlbSwitch-0;MOD CELLALGOSWITCH: LocalCellId=0, MlbAlgoSwitch=GeranMlbSwitch-0;

7.5 Performance MonitoringTable 7-4 lists the counters used to monitor inter-frequency MLB performance. They can beused to calculate the proportion of load-based inter-frequency handovers to total inter-frequencyhandovers in a cell.



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Table 7-4 Performance counters related to inter-frequency MLBCounter Name DescriptionL.HHO.InterFreq.Load.PrepAttOut Number of inter-frequency handover preparation

attempts triggered because of high loadL.HHO.InterFreq.Load.ExecAtt-Out

Number of inter-frequency handover executionattempts triggered because of high load

L.HHO.InterFreq.Load.ExecSucc-Out

Number of successful inter-frequency handoverstriggered because of high load

Table 7-5 lists the counters used to monitor inter-RAT load sharing performance.

Table 7-5 Performance counters related to inter-RAT MLBDescription Counter NameL.IRATHO.E2W.Load.PrepAtt-Out

Number of EUTRAN-to-WCDMA handover preparationattempts triggered because of high load

L.IRATHO.E2W.Load.ExecAtt-Out

Number of EUTRAN-to-WCDMA handover executionattempts triggered because of high load

L.IRATHO.E2W.Load.Exe-cSuccOut

Number of successful EUTRAN-to-WCDMA handoverexecutions triggered because of high load

L.IRATHO.E2G.Load.PrepAtt-Out

Number of EUTRAN-to-GERAN handover preparationattempts triggered because of high load

L.IRATHO.E2G.Load.ExecAtt-Out

Number of EUTRAN-to-GERAN handover executionattempts triggered because of high load

L.IRATHO.E2G.Load.Exe-cSuccOut

Number of successful EUTRAN-to-GERAN handoverexecutions triggered because of high load

L.RRCRedirection.E2W.Load Number of EUTRAN-to-WCDMA RRC redirectionstriggered because of high load

L.RRCRedirection.E2G.Load Number of EUTRAN-to-GERAN RRC redirectionstriggered because of high load

L.RRCRel.DedicatedPri.WCDMA.High

Number of times WCDMA frequencies are assigned thehighest dedicated cell-reselection priority

NOTE

LOFD-00105401 Camp & Handover Based on SPID and LOFD-001112 MOCN Flexible Priority BasedCamping also affect the L.RRCRel.DedicatedPri.WCDMA.High counter.



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7.6 Parameter OptimizationThe following parameters may need to be adjusted for better performance:l Thresholds inter-frequency load balancing or inter-RAT load sharing

The thresholds directly determine the probabilities and effectiveness of the two types ofMLB.

l Load offset (specified by the CellMLB.LoadOffset parameter)If the load offset is set to an appropriate value, the probability of ping-pong load transferwill decrease.

l Handover-related parametersThese parameters determine the handover performance for load transfer.

7.7 TroubleshootingThis section provides steps to troubleshoot a possible fault that might occur after MLB is enabled.

Serving Cell Not Initiating Load Information Exchange for Inter-Frequency LoadBalancing

Fault DescriptionWhen inter-frequency load balancing is enabled and packet injection is performed for a UE, theserving cell fails to initiate load information exchange with the neighboring E-UTRAN cells.Fault HandlingPerform the following steps for troubleshooting:

Step 1 On the M2000 client, start X2 interface tracing task by referring to Inter-Frequency LoadBalancing in 7.4.5 Activation Observation.

Step 2 Check whether the serving eNodeB has sent a RESOURCE STATUS REQUEST message,which contains information about the neighboring cells involved in load information exchangewith the serving cell. If the eNodeB has not sent this message, then this fault did occur. Go toStep 3.

Step 3 Run the LST EUTRANINTERFREQNCELL command to check the inter-frequencyneighboring cells of the serving cell.1. If at least one neighboring cell is displayed, go to 3.2. Otherwise, configure inter-frequency

neighboring cells and end the troubleshooting procedure.2. If all the inter-frequency neighboring cells displayed are intra-eNodeB neighboring cells,

this is a normal condition and no fault handling is required. If all the inter-frequencyneighboring cells displayed are inter-eNodeB neighboring cells, run the DSPX2INTERFACE command to check the connectivity of the X2 interface. If the X2interface is functional, go to 3.3. Otherwise, handle the ALM-29204 X2 Interface Fault byfollowing handling suggestions in the alarm reference.



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3. If No handover indicator for the neighboring cell is Permit Ho, go to Step 4. Otherwise,run the MOD EUTRANINTERFREQNCELL command to change it to Permit Ho.

Step 4 Run the LST INTERFREQBLKCELL command to check whether the displayed inter-frequency neighboring cells have been blacklisted.l If all these neighboring cells are blacklisted, this fault occurred because the eNodeB does

not perform MLB on blacklisted cells. No further action is required.l Otherwise, go to Step 5.

Step 5 On the M2000 client, check whether ALM-29247 Cell PCI Conflict has been reported for theserving cell.l If this alarm has been reported, handle the alarm by following handling suggestions in the

alarm reference.l If this alarm has not been reported, contact Huawei technical support.----End

Failing to Initiate Inter-RAT Load Sharing with UTRAN for U